Full text of "Rocks classified and described : a treatise on lithology"

NRLF

PUKL.ISHER & IMPORTER

UNIVERSITY Of
CALIFORNU

THE LIBRARY

THE UNIVERSITY
OF CALIFORNIA

BEQUEST OF

Alice R. Hilgard

LITHOLOGY.

LOIfDOK

FEINTED BY SPOTTISWOODB AITI) CO.
NBW-STEEBT 8QITABE

ROCKS

CLASSIFIED AND DESCRIBED.

Iwatitt on i

BY BEENHAED VON COTTA.

AN 'ENGLISH EDITION

PHILIP HENRY LAWRENCE.

WITH ENGLISH, GERMAN, AND FRENCH SYNONYMS.

REVISED BY THE AUTHOR.

LONDON :

LONGMANS, GREEN, AND CO.
1866.

LITHOLOGY, or a Classified Synopsis of the
Names of Kocks ar-d Minerals, also by Mr. LAWKENCE,
adapted to the present work, may be had, price 5s. or
printed on one side only (interpaged blank) for use in
Cabinets, price 7s.

GIFT

TRANSLATOR'S PREFACE.

IN presenting this work to English readers, I wish to
acknowledge the kind assistance I have received from
Professor Jukes and Mr. Bristow in my own country, from
M. Daubree and M. Guyerdet in France, and last, but
not least, from the distinguished author, Professor Cotta
himself, and from Mr. Stelzner, of Freiberg, to whose
valuable assistance I owe most of what is good in the
new arrangement of the Mineralogical part of the work.
For the many imperfections which, in spite of much care,
will probably be found, I am alone responsible. Never-
theless, I hope that this work may in some measure
supply a want which has been long felt in our geological
literature.

I trust that allowance will be made for the difficulties
of a translator if, in some instances, terms have been used
in this work in a slightly extended or even different
sense from that of some English authors. This has never
been done without much consideration, and what appeared
to me absolute necessity in rendering the meaning of my
author, and in the absence of an exact equivalent for the
German term in our accepted geological language.

M860773

vi TKANSLATOK'S PKEFACE.

The juxtaposition of the English, German, and French
equivalent names for each rock, although frequently pre-
senting doubts and difficulties, will, I trust, in the main
meet with acceptance, in which case it cannot fail to prove
useful.

Scientific names are the coin in which enquirers must
exchange their ideas ; and if they can be made to corre-
spond in different countries, the gain to science will be
great. Such correspondence is as important in its way
as the assimilation of currency for the operations of
commerce. Should this object have been in any way
promoted by the present work, my most sanguine expec-
tations will have been fulfilled.

I may here mention that, in furtherance of the same
object, I have published, separately, a catalogue of the
names of Rocks in the three languages. This catalogue,
which is an outline of this work, may, perhaps, prove
useful to collectors.

P. H. LAWRENCE.

LONDON : January 1866.

AUTHOR'S PREFACE

TO THIS EDITION.

BEFORE my friend the Translator undertook the transla-
tion of this work, I had collected materials and made
certain alterations with a view to a third edition.

The Translator himself, in the course of his labour,
proposed jcertain alterations, which were adopted with
my entire concurrence.

As far as my knowledge of the language enables me to
judge, after a careful perusal, the translation appears to
me to be very accurate. .

This English edition may therefore be considered as
the third edition of my original work, although, if the
appearance of a third German edition should be delayed
for some time longer, there will doubtless be new matter
and fresh alterations to be introduced; for Science
marches with uninterrupted steps towards new fields
of discovery, mid every year alters its aspect.

In a system of Lithology, however, most of the names

viii AUTHOR'S PREFACE.

which are in use will probably remain, and one chief
object of this book is to define these so as to render
intelligible the ideas which each name should convey ;
and both Author and Translator are actuated by the
desire and ambition of arriving, as far as may be possible,
at a common ground for all nations in respect of the
important matter of rock-nomenclature.

B. COTTA.

FBEIBEKG : January 1866.

CONTENTS.

PART I.
CHAPTER I.

PAGE

MINERALS ...... 1

I. Oxygen Compounds . . . . .5

A. Oxides of Silicon and Aluminum (Earths) . . 6

B. Silicates .....

a. Felspar Section ..... 8

Orthoclastic Felspars . . . , 9

Plagioclastic Felspars . . . .10

Leucite and Nepheline Group . . .14

b. Augite Section . . . . . K>

c. Mica Section . . . .22

d. Hydrous Magnesian Silicates (Talc Section) . 24

e. Zeolite Section (Non-Magnesian Hydrous Silicates) 28

The Monometric Zeolites

Hexagonal Zeolites . . . .30

Trimetric Zeolites . . . .31

Monoclinic Zeolites . . .32

f. Andalusite Section . . .34

g. Garnet Section ... .38

C. Tantalates (or Columbates), Titanates, Vanadates . 46

D. Sulphates ....

a. Anhydrous Sulphates . .47

b. Hydrous Sulphates . .49

E. Borates . . . -62

CONTENTS.

I. Oxygen Compounds continued. PAGE

F. Phosphates . . ... .53

a. Anhydous Phosphates . -. . .53

b. Hydrous Phosphates . . .54

G. Nitrates ... ... . . 55

H. Carbonates . . . . . .56

a. Anhydrous Carbonates . . . .56

b. Hydrous Carbonates . . . .59
I. Oxides of the Elements of the Hydrogen Group . 60

a. Anhydrous Oxides . . . . .60

b. Hydrous Oxides . . . . .66
II. Fluorides and Chlorides . . . . .67

III. Sulphurets. Arseniurets . . . . .69

IV. Native Elements . . . . . .74

V. Kesins. Organic Compounds . . . .76

CHAPTER H.

ANALYSIS OP ROCKS . . . . . .78

Microscopic Analysis . . . . . .78

Magnetic Analysis . . . . . .78

Chemical Analysis . . . . . .79

CHAPTER III.

PHYSICAL STRUCTURE OP ROCKS . . . .87

Texture ....... 87

Particular States of Rocks . . . . .95

Concretionary Structure . . . . .98

Special Forms of External Structure . . . .99

Jointed Structure . . . . . . 103

STRATIFICATION OP ROCKS . . . . 105

SHAPE AND BEDDING OP ROCK MASSES . . . . 106

CHAPTER IV.

GEOLOGICAL FORMATIONS AND GROUPS OF Roczs . . Ill

CHAPTER V.

TRANSITIONS AND TRANSMUTATIONS 120

CONTENTS. X

PART II. THE ROCKS.
INTRODUCTORY CHAPTER.

PAGE

CLASSIFICATION . . /'" . . . .123

CHAPTER I.

IGNEOUS ROCKS . . ', * 127

Basic Igneous Rocks ...... 131

(1) Volcanic . . . ." '. . 131

Basaltic Rocks ..... 132

(2) Plutonic . . . . . . .144

Greenstones ...... 146

Porphyrite Group ..... 168

Mica Trap Rocks . . . . .173

Syenite Group ; . ,. ^ .176

Acidic Igneous Rocks . . . . 182

(1) Volcanic . . . . . .182

Trachyte Group . . . , .183

Phonolite Group ' .. >, . . . 198

(2) Plutonic . . . . .201

Granitic Group . .... 201

CHAPTER H.

METAMORPHIC CRYSTALLINE SCHISTS .... 227

Felspar Group . . . . . 229

Quartz Group . ..... 241

Chlorite, Talc, and Hornblende Group . . 249

Schists indistinctly Crystalline . . . 264

CHAPTER HI.

SEDIMENTARY AND FRAGMENTAL ROCKS . . 259

Argillaceous Group . . . 263

Marl Group . . .

Limestone Group . 274

Gypsum and Anhydrite . 290

Fragrnental Rocks . .294

Conglomerates . 302

Xii CONTENTS.

CHAPTER IV.

PAGE

ROCKS OF SPECIAL CHARACTER OK BEDDING . . . 313

Serpentine Group -,' '.^ . . 314

Garnet Group . .318

Greisen and Schorl Group . . . . 320

Carbonaceous Group . . . r \ . 324

Ironstone Group . . . . . 340

CHAPTER V.

MINERALS AS ROCKS . 347

PAKT III.

OBSERVATIONS ON THE PROCESSES OF ROCK FORMATION IN

NATURE . . . . .- A-. . 359

Igneous Rocks ... u? v . 361

Sedimentary Rocks . . . "> .' :. - . 374

Metamorphic Crystalline Schists . . ; > . . 378

Mineral Veins and Veins of Ore 392

CONCLUSION , 393

LITHOLOGY.

PART L
CHAPTER I.

MINERALS.

THE SEVERAL SUBSTANCES which form the materials
of the earth's crust are termed 'Rocks,' the idea of a
solid rocky substance not being necessarily implied. Most
of what we call rocks are no doubt of a firm and solid
character, but some consist only of soft or loose aggregates
or accumulations of their component parts.

These component parts are always minerals ; that is to
say, all rocks are mineral aggregates, consisting of minute
mineral parts more or less solict and more or less intimately
and firmly united, knit, or cemented together. By this
definition it will be seen that we exclude the animal and
vegetable kingdoms ; it may therefore be well to add
that under the term mineral we include all mineralised
remains of organic bodies.

Most rocks are made up of parts of two or more different
minerals, in which case they are termed composite. Some
rocks, however, consist essentially of particles of one mine-
ral only, such for instance as limestone ; these, in contra-
distinction to the composite, are termed simple rocks.

The composite as well as the simple rocks not unfre-
quently contain subordinate ingredients, besides those
which are essential to their character. These subordinate
ingredients are termed accessory or non-essential. In
most cases they are inconsiderable in quantity, or they
only occur locally and do not appreciably alter the nature

2 MINEKALS.

of the rock ; but sometimes these accessory ingredients
impart a special character to it, and so to a certain extent
pass into essentials. Their presence creates the varieties
of species.

The constituent minerals (whether accessory or essen-
tial) of any given rock either occur in separate crystals or
particles distinguishable by the naked eye, or they consist
of small finely divided particles so intimately blended to-
gether as apparently to form a homogeneous mass ; never-
theless, in the latter case, their separate existence may be
generally recognised by magnifying power.

The first and principal requisite for the student of
Lithology is to be able to recognise and determine the
minerals of which a given rock consists. This is in many
cases no easy task ; he must therefore have a competent
knowledge of mineralogy. Not with a view adequately to
supply the want of such knowledge, but by way of intro-
duction to our subject, rnd for the purpose of reference
in the absence of more comprehensive works, we propose
to give in this chapter a brief notice of the principal
minerals with which we have to do in examining the
structure of rocks, adding such particulars as are more
especially useful for our present purpose.

The number of these principal minerals is relatively
very small. They may be classed under the following
comprehensive names : FELSPAR, QUARTZ, MICA,
HORNBLENDE (Amphibole), PYROXENE (Augite),
CALCSPAR, and DOLOMITE. The following occur less
frequently : CHLORITE, TALC, LEUCITE, NEPHELINE,
OLIVINE, TOURMALINE, GARNET, GYPSUM, COAL, some
SULPHURETS, and some IRON ORES.

The number of the accessory ingredients is very much
greater, and indeed almost unlimited; that is to say,
under certain circumstances almost every known mineral
may occur as an accessory in any rock, and the essential
ingredients of one rock frequently occur as accessories in
another rock. But although we may say with truth that
the number of the accessory minerals is without limit, yet
in fact only about a quarter of the number of hitherto
known minerals occur in rocks so abundantly and fre-
quently as to be specially noticed in a treatise of Lithology.

One consideration is particularly deserving the atten-

MINERALS. 3

tion of the scientific observer of rocks ; we refer to what
is termed by Breithaupt the ' Paragenesis ' of minerals.
By this is meant the law of mutual association or repulsion
of certain minerals. It is well known to mineralogists
that the presence of one mineral very frequently denotes
the neighbourhood of another, and, vice versa, that the
presence of some minerals forbids the simultaneous pre-
sence of certain others.

In 1849 Breithaupt first treated this subject, and pub-
lished in his ' Paragenesis der Mineralien ' a great number
of remarkable instances of this law. We may, for the sake
of illustration only, select the following as examples :

1. Minerals which are usually associated together:
Quartz and mica ; orthoclase, quartz, and mica ; ortho-
clase and oligoclase ; labradorite and augite ; orthoclase
or oligoclase and hornblende ; hornblende and epidote.

2. On the other hand, quartz and augite appear each to
exclude the presence of each other ; also (according to
Both) labradorite and hornblende (?).

We are unable to pursue this important subject in this
place ; we have been compelled to confine ourselves, in
the following notice, to appending a few of the more im-
portant instances of paragenesis to the description of
some of the principal mineral classes.

As to the much-debated question of classification of the
minerals, we have adopted one which appeared to us best
suited for our present purpose ; it is not exactly that of
any one author. We have -placed a few of those minerals
first which are of the most frequent occurrence ; otherwise,
the arrangement adopted will be found to correspond in
several respects with Dana's ' System of Mineralogy.'

The following are the abbreviations we have used :
H. for hardness; S.G. for specific gravity ; Cp. for
chemical composition ; Bp. for before the blowpipe. The
quantities of the chemical elements we have given in
round numbers, as being sufficient for our present pur-
pose. In the chemical formula? we have, for the sake of
convenience, adopted the abbreviations usual on the Con-
tinent, of expressing the oxygen atoms by dote, and a
stroke to denote a double atom ; thus, Fe' 2 O 3 is written
Fe. W"e subjoin the following list of formulae for the
elementary bodies and their simple compounds:

B 2

MINERALS.

CHEMICAL SYMBOLS.

Al Aluminum, Aluminium

Al Alumina
Ag Silver
As Arsenic

As Arsenic Acid
Au Gold
Ba Barium

Ba Baryta
B Boron

B Boracic Acid
Ca Calcium

Ca Lime
C Carbon

C Carbonic Acid
Cb Columbium, Niobium

Cb Columbic Acid
Ce Cerium

Ce Protoxide of Cerium
Cl Chlorine

HC1 Hydrochloric Acid
Cr Chromium

Cr Oxide of Chromium

Cr Chromic Acid
Co Cobalt

Co Oxide of Cobalt
Cu Copper

Cu Oxide of Copper
Fe Iron

Fe Protoxide of Iron

Fe Peroxide of Iron
F Fluorine

HF Hydrofluoric Acid
G Beryllium or Glucinum

G Glucina
Hg Mercury
H Hydrogen

H Water
K Potassium

K Potassa
La Lanthanum

La Protoxide of Lanthanum

Li Lithium

Li Lithia
Mg Magnesium

Mg Magnesia
Mn Manganese

Mn Protoxide of Manganese

Mn SesquioxideofMangane.se
Na Sodium

Na Soda
Ni Nickel

Ni Protoxide of Nickel
N Nitrogen

N Nitric Acid
Oxygen
P Phosphorus

P Phosphoric Acid
Pb Lead

Pb Oxide of Lead
Se Selenium
Si Silicon

Si Silica
Sn Tin

Sn Oxide of Tin
Sr Strontium

Sr Strontia
S Sulphur

S Sulphuric Acid
Ta Tantalum

Ta Tantalic Acid
Ti Titanium

Ti Oxide of Titanium

ti Titanic Acid

V Vanadium

Y Yttrium

Y Yttria

Zn Zinc

Zn Oxide of Zinc

Zr Zirconium

Zr Zirconia

QUARTZ. 5

I. Oxygen Compounds.

A. OXIDES OF SILICON AND ALUMINUM (EARTHS).

1. Quartz. Rhombohedral crystals, usually combinations
of two rhombohedrons and hexagonal prism. Cleavage accord-
ing to the planes pf one rhombohedron, but imperfect. Frac-
ture conchoidal to uneven and splintery. H.=7. S.G.=2'5
2 '8. Colourless and limpid, or variously coloured, forming many
varieties. Lustre vitreous, sometimes resinous, especially on
the surfaces of fracture. Cp. = Si, with admixture of minute
particles of colouring oxides. Two modifications of chemical
composition are distinguished by their different degrees of solu-
bility. The one is insoluble in water and in every acid, except
hydrofluoric acid ; the other is soluble in water at high tem-
peratures, especially in the presence of other acids and alkalies.
The insoluble variety of quartz may, in process of time, be-
come converted into the soluble by the contact-influence of
infiltrated moisture. The soluble variety of quartz, in small
proportions, is found in many waters of springs and rivers,
and in the sea, e. g., at the Geysers in Iceland, up to T8 | 00
per cent, and in sea- water to -nrurjuir P er cent - Bp. infusible ;
with soda fusible to a clear glass with effervescence. Not
affected by phosphoric acid.

(a) Common Quartz, the most abundant of all minerals.

It is found :

(a) As an independent rock. (See post.)
(ft) As essential ingredient of many crystalline rocks, espe-
cially the plutonic. In most kinds of granite, in greisen,
and in the crystalline schists it is found in crystalline
grains. In quartz-porphyry, rhyolite, and, excep-
tionally, in some kinds of granite (e.g. St. Austell,
Cornwall), it is perfectly crystallised.

r MINERALS.

(y) As accessory constituent mass of some rocks (snch as
crystalline schists), in form of veins and swellings, or
clothing the interior of geodes in other rocks (e.g. in
the granites of Switzerland, Carrara marble, the
variegated sandstone of the Schwarzwald, &c.) The
quartz of the geodes is frequently in the form of
transparent crystals (rock crystal), or in greyish-
brown to black crystals (smoky quartz, false topaz).

(S) As principal ingredient of many fragmental rocks
(sandstones, conglomerates). As sand and gravel in
beds of deposit.
(It) Amethyst. Violet, coloured by the oxide of manganese.

amorphous silica.

(d) Agate. A variegated combination of common quartz,

amethyst, jasper, carnelian, and other varieties of quartz,
arranged in alternate stripes or layers, or irregularly
mixed together.

\b, c, and d chiefly occur in the geodes of volcanic rocks (in
Iceland, Faroe Islands, the Brazils, &c.), or in metallic veins
(e.g. in Saxony).] .

(e) Jasper. Very frequently in globular masses (ball-jasper)

coloured red by the peroxide of iron ; found in the bog
iron-ore of Briesgau, in Germany, and elsewhere, or
coloured yellowish-brown by the hydrated oxide of
iron. (Occurs in form of pebbles, e.g. in the sand
of the Nile and Desert.) Jasper sometimes forms
subordinate layers in other rocks.

(/) Flint. Coloured greyish-blue, or black, by presence of
carbon. Occurs as a concretionary formation in sedi-
mentary limestone rocks, e.g. in the Chalk of England
and France, in the Upper White Jurassic of the Fran-
conian Switzerland in Bavaria.

OPAL. 7

(g) Chert, Homstone is distinguished from flint by its more
splintery fracture, by its transparency, and colour,
which is grey, yellow, green, red, or brown, resembling
jasper. It frequently furnishes the material of fossils,
especially of fossil wood (woodstone).

There are at least three different processes in nature which
have contributed to the formation of quartz.

Quartz has been formed: 1. By organic agency. The
siliceous needles (spiculae) of sea-sponges, the siliceous
shields of certain Protozoa (kieselguhr, tripoli), and many
plants (especially grasses) either contain quartz, or consist
entirely of quartz. 2. By agency of water. The concre-
tionary formations of flint, jasper, &c., the crystals and
amorphous quartz contained in geodes, and many formations
at springs which consist of pure quartz, and are termed
freshwater quartz. 3. By hydroplutonic agency. Daubree
has actually produced quartz, by way of experiment, through
the agency of steam on chloride and fluoride of silicon.
Many kinds of quartz have no doubt been produced by pure
plutonic agency.

2. Opal. Amorphous, massive. Fracture conchoidal to un-
even; friable. H.=5-5 6-5. S.G.=1'9 2-3. Colourless or
variegated with rich play of colours. Transparent to opaque.
Lustre vitreous, also resinous. Possesses many varieties, dis-
tinguished by their different colours and degrees of trans-
parency. Cp. amorphous Si combined with water, in varying
proportion (up to 13 per cent.), and small quantities of colour-
ing matter. It is distinguishable from quartz by being almost
entirely soluble in potash ley, in matrass yields water. Bp. most
kinds of opal decrepitate ; otherwise behaviour like quartz.

Occurrence and Mode of Formation. Opal is never an essen-
tial ingredient of rocks, but is of very frequent occurrence

8 MINERALS.

as a secondary product, furnishing the interior of small
nests, and filling vesicular cavities in volcanic rocks, or cloth-
ing the surfaces of clefts in the same rocks. In these
and similar cases the opal is a product of exfiltration from
the rock in or near which it occurs. Thus, the precious opal
found in the trachytic rocks of Hungary, the colourless
hyalite in clefts of basalt and lava (Bohemia, Auvergne).
In rare cases, however, opal forms independent layers of
small extent (riband opal) in siliceous rocks, e. g. in the
tripoli of Bilin. The variety known as menilite occurs in
knobs and layers embedded in the adhesive slate of Menil
Montant, Paris.

3. Corundum. Occurs in rhombohedral crystals, or gran-
ular aggregates (emery). Cleavage basal, also rhombohe-
dral in various degrees of perfection. Fracture conchoidal
to uneven and splintery. H. 9. S.G.=3'9 4*2. Colour-
less or coloured blue (sapphire), red (ruby), or cloudy
(corundum). Lustre vitreous, and frequently, on the basal
cleavage surface, mother-of-pearl lustre. Transparent to
translucent. Cp.=Al, with small quantities of Mg, Ca, Si.
Bp. infusible when alone, perfectly fusible with borax, but not
without difficulty ; not affected by acids. Occurs as an
original product accessorily in many rocks (granite of Silesia,
basaltic lava of Medermendig on the Rhine, dolomite of
the St. Grotthard). The precious varieties are chiefly found
in alluvial beds (Ceylon, China). Emery forms separate
masses of deposit in the talcose schist (Naxos, Saxony) .

B. SILICATES.

(a) FELSPAR SECTION.

The felspars are, after quartz, the most important of all
ingredients of rocks. We distinguish two principal kinds
of felspar, the orthoclastic (monoclinic), the two most per-

FELSPAR. 9

feet cleavage planes forming an angle of 90, and the pla-
gioclastic (triclinic) with an angle of less than 90. All
felspars have a great tendency to form twin crystals, and
this duplication occurs in them in a very marked manner,
and according to six different laws.

Orthoclastic Felspars.

4. OrtJioclase. Monoclinic. Cleavage basal and clinodia-
gonal, very perfect in both directions, hemiprismatic, im-
perfect. Fracture conchoidal to uneven and splintery.
H.=6. S.G. = 2*4 2*62. Colourless, sometimes limpid, more
frequently coloured, especially reddish, yellowish, rarely
green (amazon stone coloured by copper). Lustre vitreous,
frequently with mother-of-pearl lustre on the most perfect
cleavage surfaces. Possesses every degree of transparency,
sometimes with iridescence or play of colours. Cp.=KSi +
AlS'i 3 with 65Si, 18AJ, and 17K. A portion of the Al is
frequently replaced by Fe, or Mn, and a portion of the K is
sometimes replaced by Na or Ca. Bp. fusible with difficulty,
and only at the edges, where it forms a dull porous glass.
The varieties which contain soda colour the flame yellow.
In microcosmic salt it is only soluble with difficulty, leaving
behind a skeleton of silica. With cobalt solution the fused
''dges are coloured blue. Not susceptible to the action of
acids.

Varieties of Colour and Lustre.

(a) Adularia. Colourless, or only slightly coloured, with
bright lustre, transparent to semi-transparent. Essen-
tial ingredient of the adularia-granite and adularia-
gneiss abundant in the Alps, also frequently found in
the geodic cavities of granitic rocks (St. Gotthard).

(6) Common Felspar (Pegmatolite, Microdine). Variously
coloured, less lustrous than adularia, translucent to

10 MINERALS.

opaque. A characteristic ingredient of very many
rocks, especially amongst the phitonie, such as granite,
.gneiss, syenite, porphyry. Frequently large felspar
crystals (such as the so-called Carlsbad twins) occur
porphyritically embedded in an otherwise regularly
constituted rock (e.g. in the granite of Carlsbad in
Bohemia, and of Cornwall, porphyry of Ilmenau), or
larger crystals clothe the sides of geodes (as in the
granite of Baveno and the rocks of the Mourne Moun-
tains, in Ireland).

(c) Sanidine. Colour greyish- and yellowish-white, also
grey. Lustre vitreous, very bright, transparent, trans-
lucent. The crystals are very often split and creviced.
It forms a very characteristic ingredient of genuine
volcanic rocks, and only occurs in these. Thus it is
found in phonolites, trachytes, pitchstones, obsidian,
and lavas. Sometimes it occurs porphyritically in
large tabular crystals, as in the trachyte of Dra-
chenfels.

Plagioclastic Felspars.

All plagioclastic felspars are triclinic ; they cleave perfectly
according to the base and the brachydiagonal, imperfectly
according to the hemiprism.

5. Albite. Fracture uneven. H.=6 6'5. S.G. - 2'59
2 ! 65. Colourless or light red, yellow, green, or brown. Lustre
vitreous ; mother-of-pearl lustre on the basal cleavage sur-
faces. Transparent, translucent. A white and usually
semi-opaque variety termed pericline, is distinguished by
its constant crystallographic habitus. Cp.==NaSi + AlSi 3 ==
69Si + 19AH-12;N"a. The Na is frequently in part replaced
by Ca, K, or Mg. Bp. it fuses with difficulty, colouring the
flame yellow. It is scarcely affected by acids. Albite is

FELSPAR. 1?

frequently found associated in parallel growth with ortho
clase. It is likewise a characteristic ingredient of many
diorites and granites. Exceptionally crystals of albite are
found in compact limestone (Col du Bonhomme).

6. Oligoclase. Fracture uneven. H.=6. S. G. = 2'58
2*69. Colour greyish, yellowish, or greenish. Lustre upon
the principal cleavage surface vitreous, otherwise resinous.
Usually is much weathered, and in that state dull ; in its
fresh state translucent at the edges. Cp. = NaSi-i- AISi 2 =
62S1 + 24Al + 14Na, The Na replaced in part (up to 6 per
cent.) by Ca, K and small quantities of Fe or Mn. Bp. fuses
much more easily than orthoclase and albite, forming a clear
glass. Little attacked by acids. Oligoclase is an essential con-
stituent of diabase, diorite, and kersantite ; it is frequently
associated with orthoclastic felspars as a constituent of many
kinds of granite (Stockholm), syenite (Dresden), porphyry
(Southern Tyrol), and trachytes (Hungary).

Andesine may be considered as an oligoclase rich in lime.
It has much the outward appearance of albite. It is an
ingredient of many trachytic rocks of the Andes, and likewise
of many crystalline rocks of the Vosges.

7. Labradvrite. H. = 6. .S.G. = 2'67 276. Barely co-
lourless, usually grey, reddish, bluish or otherwise coloured ;
usually displays a rich play of colours. Lustre vitreous,
sometimes resinous ; translucent, but usually only at the
edges. Cp. = RSi + AISi = 53Si + 30A1 + 12Ca + 5Na. Bp.
fuses somewhat more readily than oligoclase to a colour-
less glass. Unlike other felspars, its powder is thoroughly
soluble in heated muriatic acid. Labradorite is an essential
constituent of many, and especially of the augitic, rocks,
e. g. dolerite, basalt, gabbro (Isle of Skye), hypersthenite,
and many lavas of Etna.

Saussurite (jade) is probably only an impure labradorito.

12 MINERALS.

bearing somewhat the same relation to it as felstone to
orthoclase. It remains unchanged by acids, occurs only in
compact or finely granular masses, and forms an essential
constituent of many kinds of gabbro and greenstones.

8. Anorthite.H.= 67. S. G. = 2'66 278. Colour-
less, white. Lustre, mother-of-pearl on the cleavage surfaces,
otherwise vitreous; transparent to translucent. Cp.= R/ 3 Si
+ 3A1S1 = 43Si + 37Al + 20Ca. The Ca replaced by Mg, K,
and Na to the extent of 5 per cent. Anorthite is completely
soluble by concentrated muriatic acid, without gelatinising,
but is distinguished from labradorite by its being more diffi-
cult of fusion. It is an essential constituent of the orbicular
diorite (Kugeldiorit) of Corsica and of many ancient lavas
(Monte Somma). It is also found in meteoric stones.

Some Aids for distinguishing the Felspar Species.

(a) Crystallographic Signs. When the light is brought to
play on the basal cleavage plane of the orthoclastic fel-
spars it presents an unbroken surface, or in case of twin
crystals (according to the Carlsbad law) is double ;
whereas in the case of the plagio clastic felspars a fine
parallel striping is usually observed, occasioned by the
parallel growth of numberless individual crystals as thin
as leaves of paper. This striping, when observable, is a
very characteristic sign, but its absence is not equally so.

(/3) Signs of Paragenesis. The following minerals are fre-
quently found in comparing : Orthoclase with oligo-
clase ; orthoclase and oligoclase with hornblende ;
labradorite with pyroxene.

On the other hand, we seldom or never find together :
the alkali felspars (Nos. 4. 5, 6) and the calcareous
felspars (Nos. 7, 8) ; or orthoclase with pyroxene ;
oligoclase with leucite and nepheline ; labradorite with

FELSPAR. 13

hornblende ; labradorite or anorthite with quartz or
leucite.

(y) The weathering of felspars is noteworthy, and is parti-
cularly useful for purposes of distinction where two
species are found together in one rock. Labradorite
and oligoclase weather more readily than orthoclase,
orthoclase more readily than albite. Bearing this law
in mind, if we have determined the species of the un-
changed felspar, we may usually determine the other
with a high degree of probability.
(3) The chemical and physical characteristics of felspars

have been already noted as above.
As regards the origin of felspars :

They are sometimes clearly the result of wet process ;
evidence of which is their appearance in veins and
clefts, also the pseudomorphs which we find after
leucite, analcime, laumontite, &c.

Sometimes metamorphic, for Daubree succeeded in pro-
ducing sanidine-like crystals by subjecting obsidian to
the influence of overheated steam.

And sometimes plutonic, as is proved by the presence of

felspars in lavas and many other rocks of undoubted

igneous origin, as also in the slags of smelting furnaces.

Finally, some are the result of process of sublimation.

Thus, crystals of felspar have been found in blown-out

furnaces, and, reasoning from analogy, we may suppose

the same process to have taken place in nature.

9. Kaolin may be put as an appendix to the felspar group,

as it is a product of the disintegration of orthoclase, albite,

and other felspars. Its chemical formula may be stated

as AJSi + 2H or Al 3 Si 4 + 6H. Occasionally kaolin is the

result of the decomposition of whole rock masses (granite

of St. Stephen's in Cornwall, gneiss of St. Yricux, near

14 MINERALS.

Limoges, graimlite near Passau). It occurs only in primary
formations. On the other hand, the clays (which, in a che-
mical point of view, may be called impure kaolin) always
occur in secondary formations.

More or less allied to kaolin are the following minerals,
all of whose composition is, however, more or less indefi-
nite, viz. lithomarye, myelin, halloysite, bole or bolus, rock-
soap, and agalmatolite. These sometimes occur as separate
independent mineral deposits, but principally are found filling
cavities and nests in various rocks, in which latter case they
are to be regarded as products of exfiltration from those rocks.
Chemically they are all hydrous aluminous silicates, and in
appearance may easily be mistaken for soapstone, talc, &c.

Leucite and Nepheline Group.

The minerals of this group, which in many respects are
closely allied to the felspars, are without doubt of contem-
poraneous origin with the volcanic (or plutonic) rocks, in
which they occur as essential constituents. They are, there-
fore, almost always, if not always, igneous products. "We
do not, however, mean to dispute the possibility of some
having arisen by wet process. The most questionable of all
in respect of origin is probably lapis lazuli.

10. Sodalite. Monometric in dodecahedrons ; cleavage,
accordingly, also massive. Fracture conchoidal to uneven.
H. r= 5-5-6. S.G. =2-26. Colour yellowish, greenish-
white, greenish-grey, and blue. Lustre on crystal sur-
faces vitreous ; on fracture surfaces resinous. Translucent.
Cp. = Na s Si + SAlSi + NaCl. Bp. fuses, with more or less
difficulty, to a colourless glass, sometimes with intumescence.
Gelatinises with muriatic and nitric acids. Sodalite is an
essential constituent of miascite, and an accessory in other
igneous rocks (dolerite at the Kaiserstuhl) .

LEUC1TE AXD NEPHELINE. 15

11. Lapis lazuli (ultramarine). Monometric in dodeca-
hedrons ; cleavage accordingly, usually massive. H. = 5*5.
S. G. = 2'4. Colour azure-blue. Lustre glassy, resinous.
Translucent at the edges to opaque. Cp. a silicate of Al
with Na and Ca, containing also NaS. Bp. loses its co-
lour and fuses to a white vesicular glass. Gelatinises with
muriatic acid, and evolves HS. Lapis lazuli is found as an
accessory in granite, limestone, and dolomite.

12. Haiiyne. Monometric in dodecahedrons ; cleavage, ac-
cordingly, usually in crystalline grains. H.= 5'5. S. G.
= 2 '4 2 '5. Colour blue, rarely green or red. Lustre vi-
treous to resinous ; semi-transparent to translucent. Cp.=
Na 3 Si + 3AlSi + 2CaS. Bp. decrepitates violently, and fuses
to a blue-green vesicular glass. Gelatinises with muriatic
acid. It occurs in single crystals imbedded in the lavas of
active volcanoes (Volturara, near Melfi), or in the basaltic
lavas of extinct volcanoes (Niedermendig, on the Rhine), in
which latter it is characteristic as an accessory mineral, and
occasionally occurs in such quantity as to have given rise to
the name of Hauynophyre for those rocks.

Nosean is very similar to haiiyne in its mineralogical
character and geological habitat, usually yellowish-grey or
greyish- white. In Brava, one of the Cape Verde Islands,
there occurs a porphyry rock, consisting of very numerous
small crystals of nosean in a felsitic mass. Cp.= Na 3 Si4-
SAlSi+NaS.

13. Leucite. Monometric, only known in trapezohedrons
(embedded). Cleavage cubic, imperfect. Fracture con-
choidal. H. = 5'5 6. S. G. = 2'48. Colour greyish or
reddish- white, also ashen-grey. Lustre vitreous, in fracture
resinous. Semi-transparent to translucent only at the edges ;
brittle. Cp. = K 3 Si 2 -I- 3AlSi 2 . Bp. unchanged ; with cobalt
solution coloured a beautiful blue; with borax melts to a

16 MINERALS.

clear glass. Gelatinises with muriatic acid. Lencite is a
frequent and very characteristic constituent of recent ig-
neous rocks, in which it appears to some extent to be a sub-
stitute for felspar. It is especially frequent in basaltic lavas
(leucitophyre), in which it always appears porphyritically
imbedded. In the older rocks leucite is unknown.

14. Nepheline (Davyne, Elceolite). Hexagonal. Crystals
with imperfect basal and prismatic cleavage, or massive.
Fracture conchoidal to uneven. H.= 5'5 6. S. G. = 2*5
2*64. Colourless, white and usually crystallised (nephe-
line), or green, red, brown, and then massive (elaeolite).
Lustre on crystal surfaces vitreous ; on fracture surfaces
pre-eminently resinous. Transparent to translucent at the
edges. Cp. = (]STaK) 2 Si + 2A1S1 = 44Si + 33A1 + IGlSTa + 5K
(with small quantities of Fe and Ca). Davyne, which is
very similar, both chemically and mineralogically, contains,
in addition to the above, some Cl and C. Bp. nepheline fuses
with difficulty, and elseolite readily to a vesicular glass.
Slowly dissolved in borax and phosphor- salt. The fused
edges are coloured blue in cobalt solution. Gelatinises with
muriatic acid. It occurs in geodic cavities of lavas, and as
an accessory constituent of dolerite and basalt. In these
rocks it sometimes forms a complete substitute for the fel-
spar, producing nepheline rock. Finally it appears as an
essential constituent of some of the older plutonic rocks
(miascite, zirconsyenite) . In dolerite it may be recognised
by its forming short thick columns, whilst the apatite, which
is associated with it in those rocks, assumes the form of
acicular hexagonal columns.

(&) AUGITE SECTION.

15. Hornblende (Amphibole). Monoclinic. Crystallised or
massive, in stalklike or granular aggregates. Cleava ge pris-

LEUCITE GROUP AUGITE. 17

matic, very perfect ; in other directions imperfect. Fracture
uneven. H. = 5 6. S.G.=2'9 3*4. Colour passing from
white through various shades of green and brown to black.
Streak either colourless or lighter than the colour of the
mineral. Lustre vitreous, on cleavage surfaces mother-of-
pearl ; the fibrous varieties silky. All degrees of trans-
parency to the opaque. Cp. variable. We may give as a
normal formula, R 3 Si' 2 + RSi, in which B = Mg, Ca, and Fe,
and Si is sometimes partially replaced by Al. Bp. these
minerals usually fuse, with intumescence, to a grey, greenish,
or black glass, and the more readily the more iron they con-
tain. The varieties richest in iron are partially decomposed
by muriatic acid ; other varieties are little affected by that
acid.

(a) Tremolite (Grammatite, Calamite). Of light colour,
semi-translucent. Iron not an essential ingredient.
Cp. = Mg'S'i 2 + CaSi=60Si + 27Mg + 12Ca. Usually
imbedded in granular limestones and dolomites, in the
form of long columnar crystals, or long stalklike or
fibrous masses.

(6) Actinolite (Strahlstein, Glassy Actinolite). Colour green.
Cp. like tremolite. Occurs as an accessory in talc-
schist, chlorite-schist, &c. also as an independent rock
(actinolite-schist) .

(c) Hornblende (proper). Colour dark-green or black;
opaque. Cp. rich in iron and alumina. Forms an
independent rock of itself, or occurs as an essential
constituent of many compound rocks (syenite, diorite,
many kinds of gneiss and porphyry). Occurs in the
form of very perfect brownish-black crystals, imbedded
in basaltic and trachytic rocks. A variety of the
mineral is termed gamsigradite, and forms an essential

constituent of the rock timazite.
C

18 MINERALS.

(d) Uralite has the same cleavage, structure, and composition

as hornblende, but the exterior form of augite. Crystals
of this mineral occur in many greenstones (uralite-
porphyries). (Predazzo.)

(e) Asbestus and amianthus are fibrous varieties of tremolite

and actinolite. In the variety known as Mountain
leather the fibres are closely interlaced, or woven like
felt. These minerals fill cavities and clefts in lime-
stone and serpentine.

(/) Nephrite and Jade may be here added. They consist of
a compact white or light-green translucent mass, with
splintery fracture. Cp. very variable, sometimes that
of tremolite. It is not a rigidly- defined mineral ;
forms independent layers as deposits between talcose
rocks (in Turkey, New Zealand, &c.).

16. Pyroxene (Augite). Monoclinic. In crystals imbedded
or attached, or in stalklike, scaly, or granular masses.
Cleavage prismatic, but usually less perfect than hornblende.
Fracture conchoidal to uneven. H.=5 6. S.Gr.^3'2 3'5.
Rarely colourless. Colour usually grey, green, or black. Lustre
vitreous, sometimes mother-of-pearl. All degrees of trans-
parency. Cp.=R, 3 Si 2 , but very variable. Si partly replaced
by Al ; R. Ca, Mg, Fe, Mn. Bp. the pyroxenes fuse (some
quietly, others with some effervescence) to a white, grey,
green, or black glass. Usually they are with difficulty re-
ducible by microcosmic salt ; those that contain Al almost not
at all. Almost all exhibit the reaction for iron, the white
and light-coloured varieties manganese. Imperfectly decom-
posed by acids. The following mineralogical varieties are
distinguished :

(a.) Diopside. Light- coloured, transparent and translucent
varieties, and

(5) Salite. Green, translucent only at the edges ; usually

AUGITE SECTION. 19

foliated. This and the last are without much geological
importance. A sahlite, termed malakolite, is however
found separately imbedded in the granular limestone.

ingredient in basalt, dolerite, diabase, and many lavas.
Frequently in the form of perfect crystals porphyriti-
cally imbedded. Also found in meteoric stones.

(d) Omphazite. Grass-green, always accompanied by garnet,

and together with it forming eklogite.

(e) Hypersthene (Paulite). Reddish-brown, greenish-black,

or black, with metallic mother-of-pearl lustre on the
faces of most perfect cleavage, and sometimes a change
of colours showing a copper-red tinge. Lustre other-
wise vitreous or resinous. In thin lamellce translucent.
Cp. very poor in lime, rich in iron and manganese.
Hypersthene is an essential constituent of the rock
hypersthenite (Penig in Saxony, Isle of Skye, Southern
Tyrol). Otherwise it is usually an accessory, and is
especially frequent in gabbro.

Appendix to Pyroxene.

Diallage (Smaragdite), which is an essential consti-
tuent of many gabbro rocks, is only a peculiar variety
of pyroxene or hornblende, or perhaps a mixture of
both.

The following are hydrous products of the decomposition of
pyroxene :

Schiller spar. An essential constituent of schiller rock
(Baste, in the Harz), accessory in serpentine.

Palagonite. The principal ingredient of the tufa of
that name (Sicily, Nassau).

Green Earth. Frequent in vesicular cavities of
amygdaloids and in basaltic tufas.
c 2

20 MINERALS.

The distinction between hornblende and pyroxene is ex-
tremely important lithologically, but is often attended with
considerable difficulty. Some assistance may be derived from
the following remarks :

(a) As to Grystallograptiic Differences. Only recognisable in
cases of granular texture, where the crystals are tolerably
perfect. One of the most essential and best-marked
differences consists in the different angles of the
cleavage prisms of the two minerals (and those are
usually identical with the angles of the exterior faces
of the crystal.) In hornblende the larger angle of the
prism is 124 30' (giving a complement of 55 30') ;
in pyroxene the angles are 87 5' to 92 55'.

(/3) Differences of Par agenesis. Rocks containing free quartz,
felspars rich in silica (such as orthoclase and albite),
or potash-mica as essential constituents, seldom
likewise contain augitic minerals, but if the latter
occur, they are almost invariably hornblende, and not
pyroxene. In pyroxenic rocks, quartz especially is
very rarely found, and if present is only accessory
(eklogite, hypersthenite). On the other hand, labra-
dorite and magnesian micas are very frequent in such
rocks, though not exclusively there found.

Pistacite and pyrites are more frequent accessories
in hornblendic than pyroxenic rocks. The pistacite is
found adhering to the surfaces of clefts, or in geodic
cavities, and would appear in most cases to be a pro-
duct of the decomposition of amphibolite.

Leucite and olivine are characteristic as accessory
minerals in pyroxenic rocks.

As a very general rule, we may characterise horn-
blende as the constituent of the plutonic, pyroxene as

AUGITE SECTION. 21

that of the volcanic igneous rocks. Nevertheless,
sometimes both are found together in the same rock
(basalt, omphacite, trachyte of Etna). In this latter
case the pyroxene is the older formation of the two,
i.e. it has cooled and become solid more rapidly than
the hornblende.

(y) The chemical differences between pyroxene and hornblende
are not marked. It would appear as if one or the other
might have resulted from the same identical mass ac-
cording to the conditions under which it cooled and
solidified. The origin both of hornblende and of
pyroxene may be of various kinds.

The possibility of their formation by wet process
during the development or the transmutation of a
rock's mass has been proved by Daubree, who actually
produced diopside by subjecting glass to the influence
of the thermal waters of Plombieres.

Many of the crystals which are found disseminated
in limestone rocks would appear to be the result of
metamorphosis (Pargas, Tyrol).

Again, both these minerals may be products of sub-
limation (Elie de Beaumont, Sacchi), or they may be
simple products of igneous action, since we find in the
slags of smelting furnaces products of precisely similar
form and composition.

17. Spodumene (Triphane). Monoclinic, isomorphous with
pyroxene; crystallised or massive in broad fibrous or scaly
masses. Cleavage orthodiagonal and prismatic. Fracture
uneven. H.=6'5 7 S.G. = 3'1 3'2. Lustre vitreous, with
mother-of-pearl lustre on the cleavage surfaces. Colour
greenish-grey to apple-green. Translucent, but frequently
only at the edges. Cp. = Li 3 Si 2 + 4AlSi 2 frequently with some
Na, K, or Ca. Bp. intumescent ; colours the flame red, but

22 MINERALS.

weakly and transitorily. Fuses easily to a clear glass. When
mixed with Ca F and KS 2 , it gives a purple-red flame. Is
not affected by acids. Spodumene is found imbedded in gra-
nite (Uto in Sweden ; Killiney Bay, Ireland ; Peterhead,
Scotland). It also occurs in the quartz veins of mica-schist
(Massachusetts) .

Killinite is a product of the weathering or decomposition of
spodumene.

This is a section of minerals distinguished by their pre-
eminent foliation (basal cleavage) to a degree not known in any
other mineral. As regards origin, they are in part purely
plutonic, being found even in the most recent igneous rocks. In
part however, they are products of wet processes, and we find
pseudomorphs after felspar, tourmaline, and other minerals.

18- Potash-Mica (Phengite, Muscovite, Binaxial Mica),
Trimetric with monoclinic aspect. The crystals usually appear
as rhombic or hexagonal plates. Sectile, and its thin laminse
elastic. H.=2 2'5. S.G.=275 31. Colourless, frequently
white, and various shades of yellow, green, or red. Light
colours are characteristic. Metallic mother-of-pearl lustre.
Transparent to translucent. Optically very distinctly binaxial ;
the angle of the optical axes =45 75. Cp. variable average
formula==mAlSi + KSi ; in which formula ra=2, 3 or 4. A
portion of the Al may be replaced by Fe, Mn, Cr ; a portion
of the K by Fe and Mn. Strange to say no Ca is to be found
in any species of mica. The K is usually =8 9 per cent.
There is usually from 1 5 per cent, of water and some fluorine.

Bp. fuses, with more or less readiness, to a cloudy glass or
a white enamel. Not affected by muriatic or sulphuric acid.

Potash-mica is an essential ingredient of many rocks, and
especially characteristic for the older plutonic or metamor-

MICA SECTION. 23

plilc rocks, thus for many kinds of granite, gneiss, and mica-
schist.

Damourite, Margarodite, and other similar minerals of very
limited frequency, are, in part at least, products of transmu-
tation of potash-mica. They occasion a transition to the
chlorites. The same may be said of Sericite, a green mineral,
of silky lustre, which is said to form the base of several crys-
talline schists and clay-slates ; but it is not .yet free from
doubt whether or not sericite is entitled to be regarded as an
independent mineral. List gives the following account of
sericite H.=l. S.G.=2'89. Foliated in one direction ; planes
undulated. Lustre silky. Colour greenish or yellowish-
white.

19. Lithia-Mica (Lepidolite, Lithionite). Trimetric, corre-
sponds with potash-mica in many crystallographic and phy-
sical properties, except that its colour is frequently red.
H. = 2'5 4. S.G.=2'84 3. The angle of the optical axes
= 70 78.

Cp. very variable, may be generally expressed by the
formula mRSi+7&RSi; m = w=l; or ra=2, n=3 ; or some-
times m=3, n=.2. Again, a part of the bases, as well as of the
acids, are compounds of fluorine, not oxygen. The content of
lithia is usually 2 5 per cent., and of fluorine 2 10. Bp.
fuses very readily, with efflorescence to a colourless, brown,
or black glass. The flame is coloured purple-red ; with acids
it is imperfectly soluble, but completely decomposed.

Lithia-mica is an essential ingredient of Greisen, very fre-
quent in some kinds of granite, and in metalliferous veins,
especially those of tin. In all these cases this mineral is
usually associated with other fluorides, such as topaz, tourma-
line, apatite, &c.

20. Magnesia-Mica (Biotite, Hexagonal or Uniaxial Mica).
The name of uniaxial mica is now found to be incorrect, as

24 MINERALS.

all magnesia-mica is "binaxial, if only slightly. The angle of
the two axes is for the most part less than 5. Trimetric (?)
crystals, usually tabular ; usually sectile, and in thin plates,
elastic. H.=2'5 3. S.G. -- 27 31. Green, brown, black, in
general colours usually dark. Metallic mother-of-pearl lustre.
Translucent to opaque. Cp. very variable; chiefly =AlSi +
K, 3 Si, in which Al is in part replaced by Fe, and R--Mg, K,
Fe. The Mg=9 25 per cent. Some fluorine, chlorine, and
water likewise enter into the composition. Bp. fuses with
greater difficulty than the before-mentioned species of mica, to
a grey or black glass. It is little attacked by muriatic acid ;
on the other hand, unlike potash-mica, it is completely de-
composed by concentrated sulphuric acid, leaving a white
residue of silica.

The geological area of biotite is far more extensive than
that of potash-mica, for it is not only found in the older
plutonic rocks and crystalline schists (granite, porphyry,
gneiss), but also in more recent and the most recent volcanic
products (trachyte, basalt, and the corresponding lavas).

Rubellan and Phlogopite are minerals closely allied to mag-
nesia-mica, of which rubellan is perhaps only a transformed
product.

(d) HYDROUS MAGNESIAN SILICATES (TALC SECTION).

These have many characteristics and properties in common.
Some minerals which contain Fe instead of Mg belong to the
same group. We may make three principal divisions : the
Chlorites (21), the Serpentines (2225), and the Talcs (26,27).
The chlorites under certain circumstances may be regarded as
hydrous mica ; the serpentines and talcs appear chiefly to be
products of metamorphosis, perhaps occasioned by percolating
water. The most important species are :

21. Chlorite (Ripidolite). Ehombohedral ; the crystals

TALC SKCTIOX. -25

grouped in the form of comb or botryoidal shape, usually in
massive, foliated, or scaly aggregates. Cleavage basal, very
perfect; sectile. Its thin lamellae flexible, but not elastic.
H.=l 1-5. S.Gr.=2'65 to 2'85. Colour green, in various
shades. Its crystals are frequently translucent, and of red colour
when regarded in the direction of thfc principal axis. Streak
greenish-grey. Lustre mother-of-pearl. Thin laminae trans-
parent to translucent. Cp.=3R 3 Si-f E 3 Si-f 12H=30 31 Si +
1419 Al + 32 37 Mg+5 6 Fe. In matrass it gives out
water. Bp. fuses on charcoal ; with borax it melts and shows
uhe reaction of iron. Thin laminae are decomposed by concen-
t rated sulphuric acid.

Chlorite forms the most important and essential elements
of chlorite- schist, also of chlorite mica-schist, both frequent in
the Alps. In the protogine-granite and protogine-gneiss it is
a substitute for mica. It is also a characteristic constituent
of diabase, and many kinds of syenite-porphyry (Altenberg in
Saxony).

Delessite is a mineral closely allied to chlorite, but richer
in iron. It is frequent in vesicular cavities of melaphyres.

Pennine, Ripidolite, and Clinochlore are minerals resembling
chlorite, but not yet accurately denned. They are of frequent
occurrence in chloritic schists as essential ingredients.

Some of the minerals which we have already noticed as
having arisen from transmutation of augite, such as schiller
spar, green earth, &c., are externally very similar to chlorite.

22. Saponite (Soapstone) . Massive, sectile, and very soft.
S.G.^2'26. Colour white or light grey, yellow or reddish
brown, dull, with lustrous streak. Greasy feel, not adhesive
to the tongue. Cp. = 2Mg 3 Si 2 + Al *Si + 10H. In the matrass
it gives out water and becomes black. Thin laminae melt
with difficulty at the edges. It is readily and completely
decomposed with sulphuric acid.

26 MINERALS.

Saponite occurs in fissures of serpentine rock (Lizard's
Point, Cornwall).

23. Serpentine. Usually compact, sometimes granular or
fibrous ; in the latter case it is called chrysolite or serpentine-
asbestus. Fracture conchoidal, flat, or uneven, splintery,
fine-grained, or of twisted fibres. H.=3 4, rarely 5 ; S.G.=
2 '2 2 '6. Bright coloured and translucent varieties are termed
precious serpentines to distinguish them from the ordinary
serpentine, which is usually of dark colour green, red,
or brown. Cp.=the general formula Mg 9 Si 4 H (i =43 Si +
42 Mg + 12 H, with a trifling percentage of Al and Fe. In
matrass gives out water and becomes darker in colour. Bp.
almost infusible, exhibits the reaction of iron ; easily soluble
in borax, in microcosmic salt with effervescence. When
powdered, soluble in muriatic acid, and still more readily
in sulphuric acid.

Serpentine is found disseminated in rocks, usually massive,
sometimes in broken masses, plates, and veins. It likewise
forms a rock of itself.

The right of serpentine to the character of an independent
mineral is open to doubt, as it frequently appears to be only
a pseudomorph of other minerals, e. g. hornblende, augite,
garnet, spinel, &c. The rock serpentine also appears to be
usually, if not always, a product of transmutation derived
from other rocks, such as granite, gneiss, gabbro, chlorite-
schist, &c. ; and only to resemble the mineral, not to con-
stitute, strictly speaking, an aggregate of it. (Yide post,
p. 314.)

24. Ottrelite. In small thin hexagonal or rounded laminae ;
cleavage parallel to the lateral faces. Hard; is capable of
scratching glass. S.Gr. =4'4. Greenish grey to blackish-green.
Lustre vitreous; translucent. Cp. = (Fe,Mn) 3 Si 2 + 2AlSi +
3H. In matrass gives out water. Bp. fuses with difficulty

TALC SECTION. 27

at the edges to a black magnetic globule ; with borax, iron
reaction ; with soda, that of manganese.

Ottrelite is found disseminated in various kinds of clay-
slate, which have received the name of Ottrelite Slate (Lux-
embourg).

25. Glauconite. Small, round, dark-green grains, which
when recently exposed are frequently very soft, but in time
assume about the hardness of gypsum. S.G.=2'29 2'35.
Cp.=a hydrous silicate of Fe and K (5 10 per cent. K),
moreover Al and small quantities of Ca and Mg.

Glauconite is found in the form of grains or nuclei of
minute fossils (Foraminifera) imbedded in clay-marl and
sandstone rocks. Very characteristic for rocks of the Chalk
formation (Upper Greensand, Isle of Wight; Chalk of Calais).
Occurs also in other sedimentary formations (Muschelkalk of
Berlin ; Calcaire grossier, Paris ; Browncoal Sandstone of
the North-eastern Alps).

26. Talc. Trimetric (?) ; rarely crystallised, usually mas-
sive, in granular, foliated or scaly aggregates. Cleavage basal,
very perfect. Very sectile with greasy feel. Thin laminae
flexible, but not elastic. H.=l 1-5. S.G. = 2'56 2-8.
Colour white, grey, and green, in various shades. Lustre
mother-of-pearl, or resinous. Translucent to opaque. Opti-
cally binaxial. Cp. = Mg 6 S> + 2H=62 Si + 32'9 Mg-f 4'9 H.
The Mg is partly replaced by Fe. Bp. shines brightly and
loses its colour ; exfoliates ; becomes hard ; does not fuse.
If heated with cobalt solution, becomes pale-red. Is not at-
tacked by acids.

Varieties especially noticeable are :

(a) Foliated Talc. The purest crystalline talc.
(6) Steatite. Amorphous. Frequently pseudomorphous after
other minerals. Decomposes with boiling sulphuric acid.

28 MINERALS.

Talc is a very widely diffused mineral. Talc-schist and
many beds of rock in the regions of crystalline schists con-
sist almost exclusively of this mineral. Talc-mica-schist,
protogine, and some sandstones contain it as an essential
ingredient.

27. Meerschaum. Massive and in nodules. Fracture flat
conchoidal, and fine-grained, earthy; sectile. H. = 2 2 '5.
S.G.=0'8 1. Colour yellowish or greyish- white, dull.
Streak little lustrous. Opaque. Greasy feel ; adhering
strongly to the tongue. Cp. (probably) MgSi + H, usually
with some C. Bp. contracts, becomes hard, and fuses at the
edges to a white enamel.

Forms separate beds, which are the result of a process of
transmutation, probably of Magnesite.

(e) ZEOLITE SECTION (NON-MAGNESIAN HYDROUS SILICATES.)

The minerals which are grouped under the name of Zeolites
are an extensive family of the silicates, having both as to che-
mical composition and crystallographic form much in common
with the Felspar group, as well as with the Augite and the An-
dalusite groups but their chief distinguishing feature is that
they invariably contain a large proportion of water, varying
from 4 22 per cent.

The following properties are common to all zeolites. Before
the blowpipe they froth up and melt to a glass, which
owing to the many bubbles never becomes very clear or trans-
parent. They are all decomposed by muriatic acid, under
which process the Si is precipitated to a gelatinous or slimy
mass. Again, they all have a colourless streak, which circum-
stance is owing to the small proportion of colouring oxides
(not above 2 per cent.) which they contain.

The geological character of the zeolites is very uniform.
They are principally found in the volcanic rocks. They are

ZEOLITE SECTION. 29

either found in the vesicular cavities, veins and fissures of
those rocks in the form of crystals and foliated and radiated
masses, or they sometimes form an essential ingredient of the
rock's mass (in basalt, phonolite). In either case they are
not original products, i. e. not of contemporaneous formation
with the rock in which they are found ; they are products of
exfiltration or of the internal decomposition and transmutation
of the mother rock. It is interesting to notice with reference
to those zeolites which are the products of what we have
termed exfiltration, that Daubree has shown them not to be
simple deposits of substances held in solution by the per-
colated water to which they owe their origin, but rather
products of the chemical action of that water at a high
degree of temperature on a portion of the rock's mass which
had already oozed out ; and thus that the same rill of water
percolating through different rocks will produce different
species of zeolite. As regards zeolite forming part of the
composition of the rock's mass, this is so frequently the case
in basalt, that it has recently been put forth as a universal
rule that no rnr.k can be a genuine basalt without zeolite.
Nevertheless we think this assertion too general, and it is
possible that nepheline, which enters largely into the com-
position of basalts, may by reason of its great solubility
in muriatic acid, have been sometimes mistaken for zeolite.
Zeolites are seldom found in metalliferous veins, or in the
fissures of the older plutonic rocks.

The most convenient arrangement of the individual species
for our present purpose will be the crystallographic. We
begin with

The Monometric Zeolites.

28. Analcime. Usually in trapezohedrons ; more rarely a
combination of these with the cube. The crystals usually

30 MINERALS.

found grouped together in geodic cavities. Sometimes mas-
sive, granular. Cleavage cubal, imperfect. Fracture uneven.
H. 5'5. S.G. = 2'1. Colourless, white to grey, or flesh-red.
Lustre vitreous. Transparent to translucent at the edges
only. Cp. =JSTa3Si 2 + 3AlSi 2 + 6H.

Analcime is found in geodic cavities of basaltic rocks
(Giant's Causeway, Ireland ; Dumbartonshire ; Seisser Alp) ;
in metalliferous veins (Kongsberg ; Andreasberg in the Harz) ;
and as a recent formation at the mouth of springs (Plom-
bieres). It is especially frequent in the old dolomitic lavas of
the Cyclopean Islands near Sicily, and those have been named
Analcymite accordingly. The observer must avoid confound-
ing the crystals of analcime with those of leucite.

29. Apophyllite (Ichthyophthalmite, Albine). Crystals py-
ramidal, columnar, or tabular. Usually grouped together in
geodes ; occasionally in scaly aggregates. Cleavage basal, per-
fect. Fracture uneven. H.=4'5 5. S.G-. = 2'33. , Colour-
less, or yellow, greyish, or reddish- white. Lustre vitreous,
on the cleavage surfaces mother-of-pearl. Transparent to
translucent at the edges. Cp. -8CaSi-|-KSi 2 + 16H, with
sometimes 1 per cent, of fluorine.

Apophyllite is found in the geodic cavities of volcanic rocks
(Iceland, Faroe, Fassa Thai) in metalliferous veins (at Utoe in '
Sweden, at Andreasberg, and in the Bannat associated with
wollastonite). In the Tertiary limestone near intruded basaltic
rocks at Puy de la Piquette, in Auvergne. Finally as a recent
deposit from spring water at Plombieres.

Hexagonal Zeolites.

30. Chabasite (Phacolite). Rhombohedral. Crystals often
of twin growth. Cleavage rhombohedral. Fracture uneven.
H.=4 4-5 S.G.=2-08 2-17. Colourless, white, or red-

ZEOLITE SECTION. 31

dish. Lustre vitreous. Transparent to translucent. Cp.=.
(Ca,Na,K)3'Si 2 + 3AlSi 2 + 18H.

It occurs in geodes of volcanic rocks (Faroe, Fassa Thai,
Giant's Causeway) ; in syenite (Massachusetts) ; ^in gneiss
(Connecticut).

Trimetric Zeolites.

31. Prehnite. Crystals tabular or short columnar. Grouped
in geodes in fan-shaped or spheroidal aggregates. Cleavage
basal, perfect. H. = 6 67. S.G.=2'8 2'95. Earely colour-
less, usually green. Lustre vitreous ; on the cleavage surfaces,
mother-of-pearl lustre. Transparent to translucent at edges
only. Cp. Ca 2 Si + AlS'i + H, frequently with some Fe.

Occurs in basaltic amygdaloids (Fassa Thai) ; in the trap
rocks of Dumbarton.

32. Thomsonite (Comptonite) . In geodes, the crystals in
sheaves or fan-shaped groups, or in fibrous aggregates. Cleav-
age, according to the brachy- and macro-diagonal, almost
equally perfect. Fracture uneven. H. = 5 5*5. S.G.=2'35
2 '38. Colour white. Lustre vitreous, sometimes mother-of-
pearl. Translucent, but usually clouded. Cp. = (Ca v N"a) a Si +
3AlSi + 7H.

Thomsonite occurs in amygdaloids at Kilpatrick, in Dum-
bartonshire, and Lochwinnock, in Renfrewshire, in the
vesicular cavities of Vesuvian lavas, in the analcimite and
phonolite of Bohemia.

33. Natrolite (Soda-Mesotype) . Crystals usually thin, co-
lumnar, acicular, or capillary. In geodes, also in bunches or
reniform masses. Cleavage prismatic, perfect. H.=5 5*5.
S.G.-=2-17 2-24. Colourless, greyish-yellow or reddish-
white. Lustre vitreous, occasionally mother-of-pearl. Trans-
lucent, or only at the edges. Cp. = NaSi * AISi -f- 2H, occa-
sionally a small quantity of Fe.

32 MINERALS.

Natrolite occurs in vesicular cavities of basaltic and phono-
lite rocks (Kilmalcolm in Renfrewshire, Aussig in Bohemia) .

34. Pliillipsite (Lime-Harmotome) . Columnar crystals,
sometimes long and sometimes short, frequently twin, growth
cross-shaped. Cleavage brachy- and macro- diagonal. EL
4 4'5. S.Gr. = 2'2. Colourless, white, yellowish or reddish.
Lustre vitreous. Transparent to translucent at the edges
only. Cp. = (Ca,K)Si+AlS> + 5H.

Phillipsite is found in the basaltic lavas of Capo di Bove
near Rome, County Antrim, in Ireland, &c.

35. Harmotome (Baryt-harmotome). Columnar crystals
almost always twins, shaped in form of a cross. Cleav-
age imperfect, the brachydiagonal more perfect than the
macrodiagonal. H.=4'5. S.G.=2'39 2*5. Colourless, or
different shades of white. Lustre vitreous, little translucent.
Cp.=BaSi+AlSi 2 + 5H, with some K and Ca.

Harmotome occurs in the metalliferous veins of Andreas-
berg, in nodules of agate from the melaphyre of Oberstein,
Zweibrucken, under like circumstances in Dumbartonshire,
where its crystals are simple.

Monoclinic Zeolites.

36. Laumontite (Laumonite). The crystals usually in colum-
nar combinations, also in granular and fibrous masses. Cleav-
age prismatic, perfect ; very friable and brittle. H. = 3'5 4.
S.G.=2'29 2*36. Colour yellowish, or greyish- white, also
reddish. Lustre vitreous, on the cleavage surfaces mother-of-
pearl. Transparent to translucent on the edges only. Cp.=
Ca 3 Si 2 + 3AlSi 2 + 12H. It loses a portion of its water very
quickly on exposure, and then falls to powder.

Laumontite is found in vesicular cavities of basaltic rocks
(Dumbartonshire, Faroe), in clefts and fissures of syenite
(Dresden), or quartz-porphyry (Botzen).

ZEOLITE SECTION. 33

37. Scolecite (Lime-Mesotype) . Crystals long or short prisms
or acicular ; also massive, radiated, and fibrous. Cleavage
prismatic, tolerably perfect. H. = 5 5'5. S.G.=2'2 27.
Colourless, greyish, yellowish, or reddish- white. Lustre
vitreous, the fibrous clusters silky. Transparent to trans-
lucent at the edges only. Cp. = CaSi + AlSi + 3H.

Scolecite occurs in the vesicular cavities of basaltic rocks
(Auvergne, Staffa), or in the fissures of the same rocks (Kil
patrick hills). t

38. Heulandite (Foliated Zeolite, Stilbite, in part). Crystals
usually tabular, rarely prismatic, either single or clustered in
geodes, also massive, in radiated, foliated, or globular aggre-
gates. Cleavage clinodiagonal, very perfect. H.=3'5 4.
S.Gr.=2'2. Colourless, white, usually red to brown. Lustre
vitreous, on the cleavage surfaces, mother-of-pearl. Transpa-
rent to translucent at the edges only. Cp. =CaSi + AlSi 3 + 5H.

Heulandite occurs frequently in the vesicular cavities of
basaltic rocks (Faroe, Iceland, Skye, Fassa Valley) ; rare in
metalliferous veins (Andreasberg).

39. Stilbite (Desmine, Radiated Zeolite). Its monoclinic
character is questionable. The crystals are broad prisms,
frequently clustered into sheaves or bundles ; also massive and
fibrous aggregates. Cleavage brachydiagonal, very perfect,
macrodiagonal imperfect. H.=3'5 4. S.G. = 2'1 2'2. Co-
lourless, white, grey, yellow, or red. Lustre vitreous, on the
most perfect cleavage surfaces, mother-of-pearl lustre. Trans-
lucent, perfect or only on the edges. Cp. - CaSi + AISi 3 + 6H.

Stilbite is a frequent inhabitant of vesicular cavities or
fissures of volcanic rocks (Fassa-Thal, Faroe, Iceland) also
occurs in metalliferous veins (Andreasberg, Kongsberg).

40. Smitlisonite (Hydrous Silicate of Zinc, Galmey, in part)
may be added here by way of appendix, although geologically
it is very far removed from the zeolites, since chemically it

34 MINERALS.

agrees with them in being a hydrous silicate free from
magnesia.

It crystallises trimetrically, hemimorph. The crystals are
nsnally small, tabular, and prismatic, independent or in geodes,
frequently grouped in fan-like, grape-like, botryoidal, or reni-
form clusters ; also fine fibrous to felt- like varieties occur.
Cleavage prismatic, very perfect, macro- domatic perfect. Frac-
ture uneven. H.=4'5 5. S.G. = 3'16 3'9. Colourless,
white and variously coloured (but always light coloured).
Lustre on crystal surfaces vitreous. Semi-transparent to
opaque. Cp.=2Zn 3 Si + 3H. When heated in matrass gives
out water. Bp. decrepitates a little, shows green phospho-
rescent light, but does not melt. Gelatinises with acid.

Smithsonite takes no essential part in the composition of
rocks, but both alone and with other zinc-ores and galena forms
separate beds of ore of considerable extent. These ores are
usually associated with dolomites and limestones (Raibl and
Bleiberg in Carinthia, Aachen, Tarnowitz in Silesia, Mendip
hills). Smithsonite occurs in veins of lead-ore at Matlock in
Derbyshire, and many other English localities.

(/) ANDALUSITE SECTION.

With respect to the minerals grouped under this head,
we must remark that they are allied together more by
their chemical and physical properties than their geological
affinities.

41. Andalusite (Chiastol/ie, Hohlspath). Trimetric. The
crystals are usually combinations of the prism and base, hence
columnar, attached, also imbedded ; also in radiated, fibrous,
and granular clusters. Cleavage prismatic, imperfect. Frac-
ture uneven and splintery. H. - 7*5. S.G. - 3'1 3 P 2. Colour
grey, greenish, or reddish-^ ; ev. Lustre vitreous, usually weak.
Barely transparent, and in that case showing trichroism ;

ANDALUSITE SECTION. 35

usually translucent, or translucent only at the edges. [The
variety chiastolite fluctuates in hardness between 3 and 7'5.
This difference is attributable to foreign substances contained
in its crystals. These foreign substances are arranged in some
sort symmetrically about the edges and axis so as to give a tes-
selated appearance in the section. The crystals are mostly
twins or fourfold.] Cp.= Al 3 fii 2 , sometimes Al 4 Si 3 , usually
with some Fe and Mn. Bp. infusible. When reduced to
powder, fuses with difficulty in borax to a transparent colour-
less glass ; with cobalt solution coloured blue. Not affected
by acids.

Andalusite occurs as an accessory in granite and crystalline
schists (gneiss, mica-schist), Devonshire and Aberdeenshire.
The variety chiastolite occurs exclusively in clay-slate, and
usually in the neighbourhood of granites or other igneous
rocks. It probably is the product of a metamorphosis result-
ing from percolated water.

42. Topaz. Trimetric. Crystals sometimes hemimorphous,
always prismatic. Single crystals attached or imbedded, or
clusters incrusted in geodes ; also coarse or fine-grained
masses. Cleavage basal, very perfect. Fracture conchoidal
to uneven. H. = 8. S.G.=3'4 3*6. Colourless and transpa-
rent, but usually yellow, red, or blue. Lustre vitreous. Trans-
parent to translucent at the edges only. Cp. = 5Al 3 Si 2 +
(3AlF 3 + 2SiF 3 ) shows reaction of fluorine. Bp. infusible,
but soluble in microcosmic salt, leaving a skeleton of silica.
Not affected by muriatic acid. With sulphuric acid, some
hydrofluoric acid is formed.

Pycnite is a fibrous variety of topaz.

Topaz is an essential constituent of topaz-rock, an accessory
of granite (imbedded, or incrusting geodic cavities) : Mourn e
in Ireland, Mursinsk in Siberia, Greifenstein in Saxony. Very

frequently associated with other minerals which contain fluo-

D 2

36 MINERALS.

rine, and with beryl and tin ore. Also in separate localities,
associated with the like minerals (Cornwall, Saxony).

Although the topaz crystals which are found imbedded in
granite appear to be of simultaneous formation with that rock,
and therefore of plutonic origin, Daubree has succeeded in
producing topaz by subjecting alumina to the action of fluoride
of silicon.

43. Staurotide (Staurolite). Trimetric. Crystals always
imbedded, prismatic, frequently cruciform. Cleavage brachy-
diagonal, perfect. Fracture conchoidal to uneven. H. = 7 7'5.
S.Gr.=3'5 3*7. Deep red to blackish-brown. Lustre vitre-
ous. Translucent to opaque. Cp. variable =(AlFe) 2 Si, or
R, 3 Si 2 , or R 5 Si 4 . Bp. infusible. With difficulty soluble in
borax and microcosmic salt. Not affected by muriatic acid.

Staurotide occurs in association, sometimes twin growth,
with the next named species ; accessory in mica- schist and
gneiss (Switzerland, Tyrol, Brittany).

44. Ky unite (Disthene,Rhoeiizite'). Triclinic. Crystals usually
long and broad-shaped (bladed), without terminal faces, fre-
quently in twins ; imbedded singly or grouped in fibrous
masses. Cleavage prismatic, very perfect, brittle. H.=6 7'2.
S.G. =3*56 3'67. Colourless or common blue. Lustre vitre-
ous, on the most perfect cleavage planes, mother-of-pearl.
Transparent to translucent on the edges only. Cp. = Al 3 Si 2 ,
with little Fe. Bp. infusible ; dark blue if heated with cobalt
solution. Not affected by acids.

Kyanite occurs as an accessory ingredient in granulite, also
in gneiss and mica-schist similarly to staurotide.

45. Lievrite (Tlvaite^Jenite) . Trimetric. Crystals long prisms.
Crystals attached or incrusting geodic cavities ; also massive,
usually in fibrous, rarely in granular aggregates. The crystals
usually coated with brown iron-ochre. Cleavage indistinct.
Fracture conchoidal to uneven. Brittle. H.=5'5 6. S.Gr.=:

ANDALUSITE SECTION. 37

3'8 4'2. Colour brownish to greenish-black. Streak black.
Lustre resinous. Opaque. Cp.=2Fe 3 Si + Ca 3 Si + Fe 2 S'i. Bp.
fusible to a black magnetic globule; with microcosmic salt
shows the reaction of iron, and leaves a skeleton of silica.
With muriatic acid gelatinises.

Lievrite is found associated with pyroxene in subordinate
masses in the mica-schist of Elba, also (according to Dana) in
the granite of Predazzo in Tyrol.

46. Tourmaline (Schorl). Rhombohedral, eminently hemi-
morphous. Crystals mostly columnar, imbedded or attached,
also massive, fibrous, or granular aggregates. Cleavage rhom-
bohedral, very imperfect. H. = 7 7'5. S.Gr. = 2'94 3'3.
Colourless, seldom transparent, most usually black, also brown,
red, blue, green, &c. Lustre vitreous. Every degree of pellu-
cidity from transparent to opaque. Very eminently polar
electric. Cp.= very various and complicated. The following
ingredients take part in its composition : Si, B, P, F, K, Na,
Li, Ca, Mg, Fe, Mn, Al, Fe, Mn. The oxygen ratio of all the
bases in this compound (including boracic acid as a base) to
the silica is constant, and is =4 : 3. Bp. very variable, in part
fusible (in different degrees), in part intumescent, and in part
not. All kinds of tourmaline, when mixed with fluor-spar and
sulphate of potash, exhibit the reaction for boron. Not affected
by muriatic acid. Sulphuric acid almost completely decomposes
the powder of fused tourmaline after lengthened digestion.

Tourmaline is of very frequent occurrence ; but is almost
exclusively confined to the plutonic-igneous and the meta-
morphic rocks. It is an essential constituent of schorl rock ;
accessory in granite, granulite, mica-schist, topaz-rock, and it
sometimes appears in such quantity in these rocks as to cause
varieties to be specially named after it. [See post.] It is
unknown in augitic and volcanic rocks. In dolomite it ap-
pears exceptionally (Capo Longo, south of St. Gotthard) ; also

38 MINERALS.

in sandstone, but only in neighbourhood of intruded plutonic
rocks. -, K

The origin of tourmaline is sometimes contemporaneous
with that of the mother rock, sometimes it is a secondary
product occasioned by metamorphism (percolation of fresh-
water springs ?). It has not yet been artificially produced.

Tourmaline is also known in pseudomorphs after felspar (in
the granite of Trevalgan, Cornwall), and on the other hand
pseudomorphs of mica, chlorite, and steatite after tourmaline,
occur in many places.

(#) GARNET SECTION.

The affinity of the different minerals of this section to each
other consists in their containing the like ratio of oxygen
between the acids and bases.

47. Chrysolite (Olivine, Peridot). Trimetric. The crystals
usually columnar and imbedded (chrysolite), but very often
massive, in granular aggregates, and disseminated (olivine).
Cleavage brachydiagonal, tolerably distinct. Fracture con-
choidal. H. =67. S.G. = 3'3 3-5. Lustre vitreous. Co-
lour green, asparagus-green, olive-green, also yellow and
brown. Transparent to translucent. (Chrysolite usually in-
cludes the transparent crystals of paler colour, while olivine,
so called from the olive-green tint, is applied to imbedded
masses and grains of inferior colour and clearness. Dana.)
Cp. = (Mg,Fe) 3 Si, with some Mn, Ca, Ti, and H. Bp. only
the varieties containing much iron are fusible. All varieties
are easily decomposed by sulphuric acid.

The most beautiful crystals of chrysolite are said to come
from granitic rocks of Upper Egypt. Fayalite, a variety very
rich in iron, is found in granite of Mourne Mountains. Other-
wise this mineral is known as essential ingredient of the rock
called eulisite. It is an accessory constituent of hypersthene

GARNET SECTION. 39

rock (Elfdalen) in talc-schist (Katherinenburg). All these
occurrences are insignificant compared with the abundance
and frequency in which both grains and crystals of olivine
occur in basalts and lavas. In basalt, olivine is almost an
essential constituent. It is also found in meteoric stones.

Olivine is, doubtless, usually a purely igneous product. If
additional proof of this were wanted, it may be found in the
crystals of an olivine rich in iron which occur in the slags of
smelting furnaces.

A rock of New Zealand, which has been called Dunite,
consists of granular olivine.

48. Beryl (Emerald, Smaragd). Hexagonal. Crystals co-
lumnar, either singly attached or imbedded, or clustered in
geodes ; also fibrous aggregates. Cleavage basal, tolerably
perfect. Fracture conchoidal to uneven. H. = 7'5 8.
S.G.=2*68 2'73. Colourless, limpid, but usually green or
blue. Lustre vitreous. Transparent to translucent at the
edges only. Cp.=(jrSi' 2 + Ai8i 2 , with some Fe and Cr. Bp.
fuses with difficulty at the edges to a clouded scoriated glass,
completely soluble in microcosmic salt. Not affected by
acids.

Beryl occurs as an accessory in mica-schist (Salzburg), in
granite (Mourne Mountains, Bodenmais in Bavaria), in black
limestone (Muzo in Columbia), and with tin-ore (Saxony).

PJicnaleite or Phenacite. Cp. GSi. Rhombohedral crys-
tals, and occurs under precisely similar conditions to beryl. t

49. Garnet. Monometric, in rhombic dodecahedrons or
trapezohedrons or in combinations of both. Crystals singly
attached or imbedded or clustered in geodes, also massive,
in granular to compact aggregates. Cleavage indistinct, do-
decahedric. Fracture conchoidal, or uneven and splintery.
][.=6-5 7'5. S.G.==3'15 4-3. Seldom colourless, usually
green, yellow, red, brown or black. Lustre vitreous to

40 MINERALS.

resinous. Transparent, translucent, opaque. Cp. extremely
manifold, so that six groups may be distinguished of essen-
tially different composition, passing over, however, one into
the other. The common formula may be thus given : B 3 Si-f
RSi, in which formula E,= (Ca, Fe, Mn, Mg), and R=(A1,
Fe, Cr). Bp. fuses with considerable ease to a green, brown,
or black glass, which is frequently magnetic. With phosphor-
salt gives a siliceous skeleton, otherwise iron and manganese
reaction. In raw state little affected by muriatic acid, but
after fusion easily and completely decomposed by that acid,
with a gelatinous precipitate of silica.

Almandine, Grossularite, Essonite, Common or Aplome Garnet,
Colophonite and Melanite are varieties chiefly distinguished by
their colour and different degrees of transparency.

Garnet occurs as an essential, and sometimes sole ingredient
of the following rocks : garnet rock, eklogite, eulisite, kinzi-
gite. It likewise is a very frequent accessory in granite,
granulite, vitreous trachyte and perlite (in which it would
appear to be a contemporaneous formation with the mother-
rock), and in metamorphic rocks (e.g. chlorite- schist, mica-
schist), where it is probably a product of the very process of
metamorphism. In limestone and sandstone rocks (Killan
and Wexford in Ireland), and in lavas of Vesuvius.

50. Pyrope. Monoclinic, crystals almost always rounded
off at the edges, imbedded, or scattered loose in alluvial soil.
Fracture conchoidal. H.=7'5. S.G.=3'69 3'8. Colour
deep hyacinth to blood-red. Lustre vitreous. Transparent
or very translucent. Cp. a magnesian alumina- garnet, with a
considerable portion of the magnesia replaced by Fe and
Cr. Bp. becomes black and opaque at a red heat, but re-
sumes its transparency and red colour on cooling. With
borax, gives the reaction of chromium. Not affected by
acids unless previously fused.

GARNET SECTION. 41

Pyrope is a very characteristic accessory constituent of
many kinds of serpentine (Saxony), and of the opal-rock
termed vitrite (Bohemia).

51. Zircon {Hyacinth). Dimetric. Crystals columnar or
pyramidal, singly imbedded or attached. Cleavage pyramidal
and prismatic, imperfect. Fracture conchoidal to uneven.
H.=7'5. S.G.=4 47. Colourless, rarely white, usually
coloured yellow, red or brown. Lustre adamantine, vitreous.
Every degree of transparency. Cp. = ZrSi, with little Fe.
Bp. infusible, only soluble with borax. Partially decomposed
in sulphuric acid after long digestion. Not affected by any
other acid.

Zircon occurs in many rocks (more or less abundantly),
usually as an accessory ingredient only, viz. in zirconsyenite
(Norway, Ural) ; in granite (Criffel, Kircudbright and New
Jersey) ; in basaltic lavas of extinct volcanoes (Rhenish
Prussia) ; and in volcanic tufa (Auvergne) ; in granular lime-
stone (Hammond).

52. Idocrase (Vesuvian, Egeran, Wiluit). Dimetric. Crys-
tals usually columnar or pyramidal, imbedded and attached ;
also massive in fibrous and compact aggregates. Cleavage
prismatic, imperfect. Fracture uneven and splintery. H.=
6'5. S.G. = 3*45. Colour yellow, green or brown. Lustre
vitreous or resinous. Transparent, translucent, opaque. Cp.=
R 3 Si + RSi, and R= principally Ca, Fe, Mg, with H up to
3 per cent. R=A1, Fe. Bp. fuses easily, with effervescence,
to a yellowish-green or brownish glass. With microcosmic
salt it produces the reaction of iron and a siliceous skeleton.
In raw state, imperfectly decomposed by muriatic acid,
but after fusion, completely decomposed with a gelatinous
precipitate of silica.

Idocrase occurs as an accessory in old lavas of Vesuvius ; in
serpentine (Mussa Alp, Piedmont) ; in dolomite (Fassa Thai,

42 MINERALS.

where it is an unmistakable product of metamorphism) ; and
in metalliferous veins (Swarzenberg, Saxony).

Its igneous origin, at least in part, is proved by the appear-
ance of similar products in slags of furnaces.

53. Scapolite (Wernerite). Dimetric. The crystals columnar,
attached and imbedded, also clustered in geodes, or massive
and granular. Cleavage prismatic, tolerably perfect. H.=
5 5*5. S.Gr.= 2'6 2*7. Colourless, or coloured pale green,
green, or reddish. Lustre vitreous to resinous. Semi-trans-
parent to opaque. Cp. very fluctuating, in part answering
to the formula : B 3 Si 2 + 2AlSi, with Ca, Na, some H and Fe.

Scapolite is an essential constituent of wernerite rock ; it
also occurs as an accessory in granite and other crystalline
rocks, likewise in limestone, but in that case usually near the
margin of intruded granites. Finally in veins of ore ( Arendal) .

Heionite and Mellilite. Limpid crystals found in the marble
blocks of Somma, and Mellilite, dirty yellow, found in nepheline
rocks at Capo di Bove near Rome, are two minerals very
closely allied to scapolite.

54. Epidote (Pistacite, Zoisite). Monoclinic. Crystals co-
lumnar, extended in the direction of their horizontal axis,
usually in geodes, also massive and in fibrous, granular, or
compact aggregates. Cleavage orthodiagonal, very perfect,
hemidomatic perfect. Fracture conchoidal to uneven. H. =
6 7. S.G. = 3'2 3*5. Almost always coloured, viz. green,
yellow or grey. Lustre vitreous, and on the cleavage surfaces
adamantine. Transparent to opaque. Cp. = R 3 Si-f 2RSi, in
which formula R Ca, with some Mg and up to 2 per cent H ;
R=A1, Fe. Bp. variable ; after being subjected to strong
heat or melted, all varieties may be decomposed by muriatic
acid and they become gelatinised.

Zoisite is grey, with Ca and Al ; it occurs as an accessory in
granular limestone and granite (Fichtelgebirge).

GARNET SECTION. 43

Pistacite is green and rich in Fe. It occurs as an accessory
and very frequently in hornblende rocks, and is probably
the product of decomposition of hornblende. It also occurs
in beds of iron-ore (Arendal).

55. Orthite (Allanite, Cerine). Monoclinic, isomorphous
with epidote, but seldom occurs in distinct crystals. More
usually massive, in granular and short fibrous aggregates.
Fracture conchoidal to uneven. H. 5 5*6. S.G. = 3'3 4'2.
Colour, pitch-brown to black. Streak greyish or greenish.
Lustre imperfect, metallic to vitreous and resinous. Trans-
lucent at the edges to opaque. Cp. variable. In part, R :} Si +
JiSi, in which R= Al and R=Ce, Ca, Mg, with little La and H,
and in the variety orthite, Y. Bp. on charcoal, puffs up slightly
and fuses to a black glass ; with borax fuses easily and makes
with oxidising flame a bead of blood-red colour in the heat and
yellow on cooling ; with the reduction flame the bead is green.

Orthite occurs as an accessory in granite, especially in cer-
tain narrow dykes of granite, rich in felspar, which traverse
hornblendic rocks (Greenland, Dresden) ; in zirconsyenite
(Hitteroe in Norway), where the crystals are a foot in height ;
sometimes in porphyries (Totun Fjeld in Norway).

56. Gadolinite. Monoclinic, but seldom in crystals, usually
massive and imbedded. Fracture conchoidal to uneven. H.==
6-57. S.G. = 4 4-3. Pitch- and raven-black. Streak
greenish-grey. Lustre vitreous, resinous. Translucent at
the edges to opaque. Cp. various, in general R 3 Si ; and R=
Y, Ce, Fe, Ca. Bp. puffs up slightly without fusing, glows
vividly and burns to a light-grey colour. Gelatinises with
muriatic acid.

Gadolinite occurs chiefly in granite, and as an accessory,
imbedded (Fahlun in Sweden, Hitteroe in Norway).

57. Axinite (Thumite). Triclinic. Crystals singly at-
tached, or clustered in geodes, also massive, in scaly aggre-

44 MINERALS.

gates. Cleavage indistinct. H. = 6'5 7. S.G.=3'3. Colour
clove-brown, grey, or plum-blue. Transparent to translucent
at edges only. Exhibits trichroism in an eminent degree.
Cp. very complicated = B, 3 Si + 2RSi + JB Si; and R = Ca,
Mg, K ; R = Fe, Mn. Bp. melts easily, and with intumescence,
to a dark green glass, which becomes black in the oxidation
flame ; with fluor-spar and sulphate of potash gives the reaction
of boracic acid. After fusion it gelatinises completely with
muriatic acid. Axinite occurs in the geodes of granite (Oisans,
St. Gotthard), or in metalliferous veins (Botallack in Cornwall ;
Kongsberg in Norway).

58. Cordierite (Dickroite, Peliom, lolite). Trimetric. Crys-
tals usually columnar, hexagonal, also massive and dissemi-
nated. Cleavage brachydiagonal, tolerably perfect. Fracture
conchoidal to uneven. H. = 7 7*5. S.G. 2*6. Colourless, but
usually coloured bluish-grey, violet-blue, or brownish. Lustre
vitreous ; in fracture eminently resinous. Transparent to
translucent, beautiful trichroism. Cp. R 3 Si 2 -f 3AlSi ; and
R=Mg, Fe, Mn and H. Bp. fuses with difficulty at the edges
to a glass ; dissolved with difficulty in borax. Little affected
by acids.

Cordierite occurs as a substitute for quartz, and an essential
ingredient in several granites and in metamorphic gneiss, under
circumstances pointing to an igneous origin, or to an origin
from contact with igneous masses (Saxony). It also occurs
in beautiful crystals in metalliferous veins (Bodenmais in
Bavaria).

FaMunite and Finite are products of transmutation from
cordierite, or (according to some authors) from nepheline.
They occur porphyritically in granite.

Liebnerite and Oosite are like products. They occur chiefly
in porphyry rocks.

TANTALATES, TITANATES, VANADATES. 45

C. TANTALATES (OR COLUMBATES) TITANATES,
VANADATES.

The minerals here grouped occur very frequently as acces-
sory ingredients in plutonic and igneous rocks, and are for the
iinost part of contemporaneous origin with the rocks in which
they occur.

59. Pyrochl&re. Monometric, usually in octahedrons (cry-
stals or grains imbedded.) Fracture conchoidal, brittle. H.=
55-5. S.G.=3'8 4-3. Colour dark reddish- and. blacjdsh-
brown. Streak light brown. Lustre vitreous. Translucent
at the edges to opaque. Cp. = (Ca,Fe,Ce,Mn)(Cb,fi) with
some NaF and H. Bp. becomes yellow and fuses with diffi-
culty to a brown slag, previously (sometimes) emitting an
intense light. When powdered, it is decomposed in concen-
trated sulphuric acid.

Pyrochlore occurs as an accessory in granite and syenite
(imbedded), (Miask, Brevig in Norway), also in granular
limestone (Kaiserstuhl in Baden).

60. Perofskite. Monometric, usually in cubes or octahedrons.
Crystals attached or imbedded, also massive. Cleavage cubal.
H. =5'5. S.G.=4. Colour greyish- to iron-black, or reddish-
brown. Streak greyish-white. Lustre metallic-adamantine.
Opaque. Cp.^CaTi, with small quantity of Fe. Bp. in-
fusible. Scarcely affected by acids.

Perofskite occurs as an accessory in chlorite schist (Slatoust,
in the Ural) in talc schist (Zermatt), and in granular limestone
(Kaiserstuhl).

61. Tantalite. Trimetric. Crystals usually columnar, also
massive and disseminated. Fracture conchoidal to uneven.
H.=6 6-5. S.G.=7'1 7'9. Colour iron-black. Streak
brown. Lustre adamantine metallic. Opaque. Cp. =
(Fe,Mn)(Ta,Cb 2 ), w ith sometimes some Ca and up to 16 per

46 MINERALS.

cent, of Sn. Bp. unchanged. Not affected, or very little
affected, by acids.

Tantalite occurs as an accessory in granite, imbedded, and is
usually associated with beryl and tourmaline (Finland, Sweden).

62. Columbite (Nwbite). Trimetric, usually in thick tabular
or broad columnar crystals. Cleavage macrodiagonal, very
distinct, brachydiagonal distinct. Fracture conchoidal to un-
even. H.=6. S.G. = 5'4. 6'4. Colour brownish-black to
iron-black. Streak reddish-brown to black. Lustre metallic
adamantine. Opaque. Cp. = (Fe,Mn) 3 Cb 2 , with little Ca and
Sn. Bp. infusible, unchanged. Not affected by acids.

Columbite occurs as an accessory in granite, associated with
beryl and tourmaline (Bodenmais in Bavaria, Connecticut and
Massachusetts), also imbedded in cryolite (Greenland).

63. Wolilerite. Trimetric. Distinct crystals very rare,
usually massive and disseminated. Fracture conchoidal. H. =
5'5. S.G. - 3*4, Colour wine-yellow to honey-yellow, or
yellowish-brown. Lustre resinous in the fracture. Trans-
lucent. Cp.=a silicate of Ca, Na, Ta, Zr. Bp. at first un-
changed, after some time fuses to a yellow glass. Decomposes

in concentrated muriatic acid.

Wohlerite occurs as an accessory in zirconsyenite (Brevig
in Norway), in syenite and miascite (Ditro in Transylvania).

64. Titanite (Sphene, Menochine ore). Monoclinic, frequently
crystallised, prisms and tabular, imbedded and attached, twins
frequent, also massive and in scaly aggregates. Cleavage
indistinct. H. = 5 5'5. S.G.=3'4 3'56. Colour grey or
brown. Lustre adamantine, often resinous. Semi-transparent
to opaque. Cp.=2CaSi=CaTi :{ . Bp. fusible only at the edges.
With microcosmic salt and metallic tin gives the reaction of
titanium in the reduction flame. Incompletely decomposed
by muriatic acid ; completely decomposed by sulphuric acid,
gypsum being formed.

SULPHATES. 47

Ghreenovite is red-coloured titanite containing Mn.

Titanite occurs as an accessory in the mica-schist of the
Alps, and there usually in cruciform twin crystals, in gneiss
(Massachusetts), in granite (Greenland), in syenite and zir-
consyenite (Strontian, Argyleshire ; Arendal), in volcanic
rocks, rich in felspar (Laachersee, Andernach on the Rhine),
in phonolite (Bohemian Mittelgebirge), in beds of iron-ore
(with pyroxene in Arendal), finally in granular limestone (in
many localities in North America).

65. Volborthite. Hexagonal. Crystals are small, often only
scaly particles on an earthy incrustation. H.=3 3'5. S.G.=
3'45 3'86. Colour olive- or grass-green, also yellow. Streak
almost yellow. Lustre mother-of-pearl, vitreous. Translucent
in thin plates. Cp. = (Cu,Ca) 4 V + H. When heated in glass
tube gives out water. Bp. fuses easily on charcoal, and at a
higher temperature consolidates to a slag, resembling graphite,
which slag contains grains of metallic copper. It is soluble
in muriatic acid.

Volborthite occurs as an accessory ingredient in many sand-
stones of the Permian formation of Russia, or as incrustation
on the walls of clefts in the same rocks.

D. SULPHATES.

(a) ANHYDROUS SULPHATES.

66. Barytes (Heavy Spar). Trimetric. Crystals tabular or
columnar, very various; also lamellar, fibrous, granular, or
compact. Cleavage perfect in the planes of the brachy- and
macro-diagonals. H.=2'5 3'5. S.G.-4'3 47. Colour-
less, limpid, or variously coloured, white, yellow, brown, or
red. Lustre vitreous or resinous. Transparent, translucent,
opaque. Cp.=BaS, with admixture, in small quantities, of
other bases, such as Ca, Sr, and Fe. Bp. decrepitates, and fuses

48 MINERALS.

with difficulty. Colours the flame yellowish-green. Not
affected by acids.

Barytes seldom occurs as an independent rock. It occurs
as an accessory in the form of lamellar nodules in the clay
strata of Monte Paterno near Bologna, where it is called
Bologna-spar or Bolognese stone. It also occurs in the
cavities of fossils in the Swabian Jurassic formation ; also very
frequent in veins of ore.

67. Celestine. Trimetric, isomorphous with barytes, also
the same cleavage, frequently fibrous, granular, or compact.
H. 3 3-5. S.Gr. = 3'9. Colourless, limpid, but usually
white, rarely blue. Lustre vitreous to resinous. Transparent,
translucent. Cp.=SrS. Bp. decrepitates and fuses without
difficulty to a milk-white bead. If moistened with muriatic
acid, it colours the flame carmine-red. It is only slightly
affected by acids.

Celestine only occurs as an accessory constituent in rocks.
Sometimes it is found in layers of a fibrous texture imbedded
in marly limestone (Jena), in lamellar or radiated nodules in
dolomite (Seisser Alps), or in fossils (Swabia), also in many
metalliferous veins.

68. Anhydrite (Muriacite, Karstenite) . Trimetric. Crystals
thick, tabular, but rare ; usually massive, in granular or com-
pact aggregates. Cleavage macro- and brachy- diagonal, very
perfect, basal perfect. H. = 3 3'5. S.G. = 2'8 3. Colour-
less, white, but most frequently light bluish-grey or reddish-
grey. Lustre vitreous, on the faces of basal cleavage, resinous.
Cp. = CaS. Bp. fuses with difficulty to a white enamel ; with
borax effervesces, and fuses to a transparent glass, which on
cooling becomes yellowish. Little soluble in acids.

Anhydrite occurs as an independent rock, associated with
gypsum and rock-salt (frequent in the Alps). It also occurs
in metalliferous veins (Andreasberg).

SULPHATES. 49

69. Glauberite. Monoclinic, also massive, in thin lamellar
aggregates. Cleavage basal perfect. H.=2*5 3. S.G.=
2*6 2 - 8. Colourless and coloured, greenish, yellowish or
reddish-white. Lustre vitreous to resinous. Translucent.
Taste salt and bitter. Cp. = NaS + CaS. Bp. decrepitates
violently, and fuses readily to a transparent glass. Colours
the flame reddish-yellow.

Glauberite occurs as an accessory in rock-salt (Villa Rubia
in Spain, Berchtesgaden in Bavaria, Tarapaca in Peru).

(>) HYDROUS SULPHATES.

70. Gypsum (Alabaster, Selenite). Monoclinic. Crystals
prismatic and tabular, various, frequently twins, also massive,
fibrous, lamellar, granular, or compact. Cleavage clinodiagonal,
very perfect, hemipyramidal less perfect. Sectile. In thin plates
flexible. H. = 1'5 2. S.G.=2'3. Colourless, limpid, or
white, sometimes variously coloured grey, flesh-red, yellow,
&c. Lustre mother-of-pearl on the faces of most perfect cleav-
age, silky on the hemi- pyramidal faces, otherwise vitreous.
Transparent, translucent, opaque. Cp. = CaS=2H. In matrass
yields much water. Bp. becomes dull and white, exfoliates
and fuses with difficulty to a white enamel, which has an
alkaline reaction. Soluble in 460 parts of water, in acids
somewhat more easily.

Gypsum occurs as an independent rock in sedimentary for-
mations, or in metamorphic schists (mica-schist of the Alps).
It occurs accessorily in the form of crystals or nodules in
clay-marls, rarely in metalliferous veins or dykes ; sometimes,
however, in mines as a recent product.

The origin of gypsum may be either by wet or dry process,
or by metamorphism. It is formed (1) in volcanic districts by
fumes of sulphuric acid and sulphuretted hydrogen issuing

from cracks or other openings in the ground, and act:'ng upon

50 MINERALS.

lavas previously containing pyroxene and labradorite ; (2) by
wet process, where pyrites is decomposed in the neighbour-
hood of lime, or as a sediment from the evaporation of sea-
water. The latter process may be observed taking place arti-
ficially in salt pans ; (3) by metamorphism from anhydrite by
simple absorption of water.

71. Alunogen (Hair Salt). Occurs in capillary or acicular
crystals or crystalline masses of irregular form, usually in
crystalline crusts or reniform aggregates of fibrous structure.
H.=1'5 2. S.G.=l-6 1-8. Colour white and yellowish,
or greenish. Lustre silky. Cp. = AlS 3 + 18H. Easily soluble
in water. If heated in test tube, it intumesces and gives out
water.

Alunogen is sometimes the product of volcanic action (vol-
cano of Pasto, Milo Isle), sometimes a result of the decom-
position of pyrites in coal districts, and in alum-shales (Bonn,
Dresden) ; sometimes is found as an efflorescence in numerous
places in the United States.

72. Native Alum. Chemically speaking there are several
subspecies. Crystallographically all monometric, and usually
in octahedrons ; also occurs in fibrous masses. Fracture con-
ohoidal. H.=2 2-5. S.G. = 1 -61-9. Soluble in water.
Taste sweet-astringent. Cp.=RS + AlS 3 -i-24H. According
to the various bases, different species are distinguished, viz. :
Potash-alum, soda-alum, magnesia-alum, iron-alum, manganese-
alum, and ammonia-alum. Bp. on charcoal, efflorescence ;
with cobalt solution blue.

Alum is found in the vicinity of the crater of ^tna, filling
clefts in the Coal and Browncoal formations, especially in
pyritous shales (Saarbrucken, Bohemia), and as an efflorescence
on other minerals or rocks. In fresh alum-slate no alum is
contained, but the latter is only developed in that rock by
weathering and the consequent decomposition of the pyrites
contained in it.

SULPHATES. 51

73. 'Epsomite (Epsom Sa.lt). Trimetric. Crystals columnar,
usually in granular, fibrous, or earthy aggregates. Cleavage
brachydiagonal. H.=-2'25. S.G.=175. Colourless. Trans-
parent. Taste saline bitter. Cp.=2MgS + 7H. Easily soluble
in water. Bp. if heated in test tube gives water, fuses, and
then remains unchanged. On charcoal it effervesces violently,
and shows alkaline reaction ; if heated with cobalt solution,
becomes rose-pink.

Epsomite occurs as an efflorescence from marshy ground
(Steppes of Siberia), and from many kinds of rock (gneiss
near Freiberg, alum-slate at Idria), also in solution in spring
waters (Epsom, Saidschutz in Bohemia).

74. Glaubersalt (Mirabilite). Monoclinic, usually incrusted.
H.=1'5 2. S.G. = 1-48. Colourless, transparent. Taste
cooling, and saline bitter. Cp.=NaS + 10H. Easily soluble
in water, quickly decomposing, and falling to powder in the
atmosphere. Bp. in test tube it melts in its water of crystal-
lisation. It colours the flame reddish-yellow.

Glaubersalt occurs as an independent rock (Guipuscoa in
Spain), accessory in rock-salt strata (Berchtesgaden) ; also in
mineral springs (Carlsbad in Bohemia), and salt lakes.

75. Alunite (Ahimstone) . Bhombohedral. The crystals
mostly very small, and clustered in geodes. Usually massive,
in granular, earthy, and compact aggregates. It occurs mixed
and interlaced with quartz, hornstein, and felsite. Cleavage
basal. H. = 3-5 4. S.G. = 2'6 27. Colourless, white, yel-
low, or reddish. Lustre vitreous, with mother-of-pearl lustre
on the basal cleavage faces. Translucent. Cp. = KS-f 3A1S-J-
6H. In test tube gives out water. Bp. decrepitates violently
and is infusible. Not affected by muriatic acid ; soluble in
heated concentrated sulphuric acid. Alum is manufactured
from this mineral by heating and adding water to it.

Alunite is met with in the largest known quantities at La

52 MINERALS.

Tolfa near Rome, where it occurs in small geodes in decom-
posed trachytic rocks, and owes its origin to the action of
sulphuric acid (a product of volcanic agency) upon the rock
during long periods of time (Muzay, Hungary ; Montdore,
Auvergne).

E. BOKATES.

76. Boracite. Monometric, tetrahedral. The crystals some-
times show combinations of the cube, the rhombic dodeca-
hedron, and tetrahedron. Always porphyritically imbedded.
Cleavage imperfect. Fracture conchoidal. Brittle. H. = 7.
S.Gr. = 2'97. Colourless, white or greyish, yellowish, greenish.
Lustre vitreous to adamantine. Transparent to translucent at
edges only. Cp.=Mg 3 B 4 . Bp. intumesces, fuses with diffi-
culty, forming a pearl which, whilst hot, is transparent and
yellowish, and when cooled is white and crystalline, acicular.
It colours the flame green when fused with sulphate of soda
and fluor spar. In muriatic acid it is perfectly soluble.

Boracite occurs, as an accessory only, in gypsum, anhydrite,
or rock-salt (Liineburg in Hanover, Seegeberg in Holstein,
Luneville in France ; in the last place in radiated fibrous
masses). A fine-grained to compact rock, which occurs in
subordinate masses in the salt mountains of Stassfurt near
Magdeburg, consists essentially of boracite with some chloride
of magnesium. It is called stassfurtite.

77. Borax (TinkaT). Monoclinic, isomorphous with pyrox-
ene. The crystals usually broad and short, columnar. Cleavage
clinodiagonal and prismatic. Fracture conchoidal. H. =
2 2'5. S.G.=:1'72. Colourless, or more usually yellowish
and greyish- white. Lustre resinous. Translucent. Cp.=
NaB 2 -f 10H ; usually impure. Bp. decrepitates with rapid
heating, pufis up violently, becomes black, and finally melts to
a transparent colourless powder. It tinges the flame reddish-

PHOSPHATES. 53

yellow. If moistened Avith sulphuric acid, it tinges the flame
green.

Borax is met with in loose crystals and crystalline grains
or incrustations, associated with rock-salt, on the shores of
several lakes in Thibet, where it is a recent formation. Clear
lake in California, in crystals several inches long.

F. PHOSPHATES.

(a) ANHYDROUS PHOSPHATES.

78. Apatite (Spargelstein, Phosphorite). Hemihedral hexa-
gonal. The crystals short, columnar, or tabular ; also massive,
in granular, fibrous, or compact masses (phosphorite). Cleav-
age prismatic and basic. Fracture conchoidal to uneven, and
splintery. Brittle. H.=5. S.G.=3'25. Colourless, white,
but more usually light green, blue, or grey. Lustre vitreous
on crystal faces ; resinous on fracture or cleavage surfaces.
Cp.=3Ca 3 P + Ca(Cl,F), with sometimes Mg and Fe. Bp.
only fusible in thin laminae. If moistened with sulphuric acid,
colours the flame bluish-green. Soluble in muriatic and in
nitric acids.

Apatite is met with (1) as an independent rock or in con-
cretions, principally in strata of the Browncoal formation, more
rarely in the Chalk formations, always massive (phosphorite) ;
frequent in the Oberpfalz of Bavaria : (2) as an accessory con-
stituent of rocks, especially the volcanic (nepheline-dolerite
at Lobau in Saxony ; basalt in Bohemia ; volcanic rocks of
Tumilla and in meteorites) ; in talc-schist (Zillerthal), and in
limestone (Gouverneur in North America, Arendal, Pargas) ;
(3) very frequent in veins of tin-ore.

It will be therefore seen that apatite in many cases must be
a formation by wet process, and in others a plutonic product.
Daubree has succeeded in producing artificial crystals of

54 MINERALS.

apatite by conducting fumes of chloride of phosphorus over
heated quicklime.

79. Turquois (Calaite). Amorphous in cavities and veins,
reniform or stalactitic. Fracture conchoidal to uneven. H. = 6.
S.Gr. 3=2*6 2*8. Colour sky-blue to verdigris-green. Streak
greenish- white, Lustre feeble. Translucent at the edges to
opaque. Cp. = Al 2 P + <5H, with some Cu up to 3 per cent.
If heated in test tube, it gives water, decrepitates violently,
and becomes black. Bp. infusible ; tinges the flame green.
Soluble in acids.

Turquois is met with as an incrustation in the fissures of
Lydian stone ; very precious varieties in Persia. Also occurs
in sandstone in Arabia.

(6) HYDROUS PHOSPHATES.

80. Vivianite (Blue Iron-Earth). Monoclinic. The crystals
usually single, attached, also fibrous, divergent, earthy. Cleav-
age clinodiagonal, very perfect ; in thin laminae, flexible. H. =
1*5 2. S.Gr. 2*66. Colour indigo-blue to blackish- green,
sometimes white, and becoming blue by exposure. Lustre on
cleavage surfaces, mother-of-pearl. Translucent. Cp.=Fe 3 P +
8H. Bp. in matrass gives out much water, pufis up, and
becomes particoloured grey and red ; on charcoal burns and
becomes red, and then fuses to grey, lustrous, and magnetic
globule. Readily soluble in muriatic and nitric acids.

Vivianite is usually a product of decomposition from magnetic
pyrites, in veins traversing the clay slate (St. Agnes, Corn-
wall), or in granite (Bodenmais in Bavaria). The earthy
variety is very frequent as an accessory constituent of turf
mosses and Tertiary clays. Pseudomorphous in form of oysters
and belemnites in New Jersey, U. S.

81. Wavellite (Lasionite). Trimetric. The crystals usually
small, acicular, and clustered to reniform aggregates of radiated

NITRATES. 55

structure. H.=3'25 4. S.G.=2'34. Colourless, white, or
coloured greyish, or a beautiful green or blue. Lustre vitreous.
Cp. = (Al 4 P + 18H)+JAlF. Bp. in matrass gives cutwater
and traces of hydrofluoric acid. In the forceps puffs up and
tinges the flame bluish- green, especially if moistened with
sulphuric acid.

Wavellite is met with as an accessory and a secondary
product in fissures of a soft clay-slate at Barnstaple in Devon-
shire ; in Lydian stone at Langenstriegis, near Freiberg ; and
in Devonian sandstone at Zbirow in Bohemia.

G. NITRATES.

82. Nitre (Saltpetre). Trimetric. The crystals prismatic,
isomorphous with aragonite, but usually only very thin,
capillary, and acicular. Fracture conchoidal. H.=2. S.G.
= 1'9. Colourless, white and grey. Lustre vitreous. Taste
saline, cooling. Cp. = KN. Readily soluble in water; defla-
grates vividly on glowing charcoal. Bp. fuses easily on pla-
tinum wire, tinging the flame violet.

Nitre occurs as a separate formation in the caverns of
several limestone mountains (Ceylon, Calabria), as an efflores-
cence from the surface of the ground, especially in hot weather
after rain (Aragon, Hungary, East India) ; also in springs.

83. Nitratine (Chili saltpetre). Rhombohedric. In crystals,
and crystalline grains ; cleavage, rhombohedric. H. = 1*5 2.
S.G.=-2'1 2'3. Colourless or light coloured. Transparent to
translucent. Taste saline, cooling. Cp. = NaN. Soluble in
water ; deflagrates in glowing charcoal, but less vividly than
saltpetre. Bp. fuses, tinging the flame yellow.

Nitratine is a marine product, found in grains mixed with
the sand, and associated with gypsum, rock-salt, and glauber-
salt, occurring at many parts of the coast of Chili.

56 MINERALS,

H. CARBONATES.

(a) ANHYDROUS CARBONATES.

The most important of the carbonates are those comprised
in the Calcite group. The calcspar and dolomites form whole
mountain ranges (limestone and dolomite) as well as isolated
mineral formations of minor extent in cliffs, fissures, and
veins.

They are chiefly of neptunian origin, partly crystalline or
compact precipitates ; partly formed by springs ; and partly
the result of organic processes (chalk, coral). There are
probably no limestone rocks of plutonic origin, although
carbonate of lime under high pressure is capable of fusion
without chemical decomposition. The minor mineral forma-
tions in clefts, veins, dykes, and geodes are doubtless, for the
most part, the result of infiltration.

All calcites are rhombohedral in crystallisation. Calcspar
alone presents great variety of form. Its crystals are grouped
and interlaced in almost every conceivable shape and fashion,
and the uncrystallised varieties are fibrous, granular, compact.
The cleavage of the crystals is rhombohedral, very perfect.
The angle of the cleavage rhombohedron is the most charac-
teristic distinguishing feature of the different species, which
can only be determined in many cases by an accurate measure-
ment of that angle. Fracture conchoidal, but in the crystal-
lised varieties it is somewhat difficult to obtain a genuine
fracture. The colour is usually white, grey, yellowish, reddish,
or brownish. Lustre vitreous, sometimes resinous. Calcspar
and magnesite alone are sometimes perfectly transparent,
the other calcites at most only attain translucence. The Cp.
of all calcites comes under the general formulae E/C.

The following are the principal species of this important
group of minerals :

CARBONATES. 57

84. Calcspar {Calcareous Spar, Calcite). H.=2'5 3*5.
S.G. = 2'5 2-8. Cp. = CaC, usually with small quantities of'
Fe, Mg, Mn. Bp. infusible, but burns to quicklime with a
bright light. Readily soluble in muriatic acid, even in large
pieces, with effervescence, caused by the evolution of carbonic
acid.

Limestone, marble, chalk, oolite, pisolite, coral, are some of
the most important of the very numerous varieties which
form independent rocks, and will be described hereafter as
such. Marl is a mixture of clay and lime. Iceland spar is
a pure transparent variety of calcspar. Anthraconite is
coloured black by admixture of carbon. It would lead us too
far to attempt to enumerate all the varieties of this very
abundant mineral.

Calcspar stands next to quartz in importance, as consti-
tuting the mineral of the greatest frequency after it, and
forming nearly as large a portion of the earth's crust.

85. Magnesite (Talc-spar). H.=3'5 4*5. S.G.=2'8 3.
Cp. = MgC, usually also some Fe. Bp. becomes red if heated
with cobalt solution. Soluble in acids, if powdered and heat
applied.

86. Dolomite (Bitter Spar, Brown Spar, Ankerite). H.=
3-5-^. S.G. =2-85 2-92. Cp.=CaC + MgC, usually with
admixtures of Fe and Mn. Ankerite is particularly rich in
iron. Bp. infusible, burns to caustic. Does not usually effer-
vesce with muriatic acid, and is only soluble in that acid if
powdered and heat applied.

87. Breunnerite (Bitter and Brown Spar, in part ; Mesitine
Spar). Cp.=FeC + 2MgC. H.=4'5. S.G.=3 3'63.

88. Spathic Iron (Sparry Iron-ore, Siderite). H. = 3'5 4'5.
S.G. 3'7 3'9. Colour always yellowish-grey or yellowish-
brown. Cp. FeC, with some Mn, Mg, and Ca. In matrass
decrepitates and gives out carbonic acid. Bp. infusible ; but

58 MINERALS.

becomes black and magnetic. Soluble in acids without heat
applied (effervescing).

In the compact state, or when occurring in reniform masses
or concretions, this mineral is termed SpJicerosiderite, and if,
moreover, combined with play, Clay Ironstone.

89. Zinc Spar (Calamine, Galmey, in part). H. =5. S.G.
=4 4'3. Cp.=ZnC, with small quantities of Fe, Mn, Ca,
Mg. Bp. loses its carbonic acid, and then shows reaction of
oxide of zinc. Readily soluble in acids, with effervescence.

90. Aragonite. Trimetric. Crystals usually columnar, with
inclination to twin formations. Singly imbedded or clustered
in geodes ; also occurring in divergent and fibrous aggregates
and stalk-like, coralloidal shapes (flos ferri), or in the form of
peastone (pisolite). Cleavage brachydiagonal, distinct ; pris-
matic, and brachydomatic, imperfect. Fracture, conchoidal
to uneven. H. =3'5 4. S.G.=2'93. Colourless and coloured
yellow, wine-yellow, reddish. Lustre vitreous. Transparent
to translucent. Cp.=CaC, very often with SrC (up to 2 '4
per cent.), also some CaF. Bp. in matrass decrepitates
violently, and falls to a white coarse powder ; on charcoal
burns to caustic lime ; if containing strontian colours the
flame carmine. Soluble both in muriatic and nitric acids,
with effervescence.

Aragonite occurs as an accessory in clay and gypsum
(Molina and Valencia in Aragon). In clefts and veins of
vesicular cavities of basaltic rocks (Bilin, Bohemia). Flos-
ferri is formed in great perfection in the Styrian iron mines.
A fine fibrous variety called satinspar is found in thin silklike
veins traversing the shale at Alston Moor. Peastone (sprudel-
or erbsenstein) occurs in great beauty at Carlsbad.

Aragonite is entirely a watery product. It is said that
whereas cold springs can only produce calcspar, hot springs give
birth to aragonite. Moreover, according to Becquerel, aragonite

. CARBOXATES. 59

is formed by the action of a saturated solution of NaC 2 on
gypsum, but calcspar if the solution of NaC 2 be much diluted.

(6) HYDROUS CARBONATES.

91. Trona (Urao). Monoclinic. Crystals broad, columnar ;
in direction of horizontal axis, also in fibrous and divergent
aggregates. Cleavage orthodiagonal, perfect. H. =2 '5 3. S.G.
=2*1. Colourless or grey. Lustre bright vitreous. Transparent.
Cp. = Na 2 C 3 + 4H. Sometimes with some NaCl. Does not alter
by exposure in a dry atmosphere. Yields water in matrass.
Soluble in dilute muriatic acid with brisk effervescence.

Trona forms an independent rock (Figzan, North Africa).
It forms a crust on the ground on mountain slopes at Mara-
caibo in Peru ; and occurs as an efflorescence near Sweetwater
River, Rocky Mountains, mixed with sulphate of soda and
common salt.

92. Natron {Carbonate of Soda). Monoclinic. Is only
known in nature in form of incrustation, or mealy efflorescence
on the surface of the ground, or various rocks. H. = 1 1'5.
S.Gr. 1'4. Colourless, white or grey. Lustre vitreous, dull.
Taste alkaline. Cp. NaC-f 10H. Unlike trona it weathers
rapidly on exposure to the air. Liquifies at a moderate tem-
perature, and dissolves in its own water of crystallisation ;
otherwise, however, has the same attributes as trona (Egypt,
Hungary, Vesuvius).

93. Malachite. Monoclinic. In aggregates composed of
minute crystallisations, acicular and capillary, lamellar, botry-
oidal, and stalactitic, fibrous to compact. Cleavage when crys-
tallised basal and clinodiagonal, very perfect. H. = 3'5 4.
S.G 3*7 4. Colour emerald- to verdigris-green. Streak
verdigris- to apple-green. Lustre of crystals adamantine and
vitreous ; of aggregates silky to dull. Translucent to opaque.
Cp. = Cu 2 C + H. In matrass yields water and blackens. Bp.

60 MINERALS. -

fuses on charcoal, and is finally reduced to copper. Soluble
in acids, with effervescence.

Malachite occurs as an accessory in various rocks. It is
doubtless usually, if not always, a product of the decomposition
of copper-ores (Siberia; Chessy near Lyons; Cornwall). It
very frequently is found in the form of a pseudomorph of
azurite and red copper-ore.

94. Azurite (Lasurite, Blue Copper-ore). Monoclinic. Crys-
tals columnar or tabular, usually in clusters or geodes ; also
massive and earthy varieties. Cleavage clinodomatic, toler-
ably perfect. Fracture conchoidal to uneven, and splintery.
H.^3'5 4-25. S.G-.=3'5 3-8. Colour azure-blue, in earthy
varieties smalt-blue. Lustre vitreous. Translucent, opaque.
Cp. Cu 3 C 2 + H. Bp. similar to malachite.

Azurite resembles malachite in the places where it is found
in nature, and in the mode of its occurrence in other respects.
The earthy variety of azurite may, from its outward appearance,
be easily mistaken for vivianite.

I. OXIDES OF ELEMENTS OF THE HYDROGEN GKOUP.

The oxides collected under this head properly speaking
belong more justly to the family of earths (Nbs. 1 3). We
have, however, postponed their consideration in order to give
place as far as possible to those minerals which are more im-
portant to the geologist.

(a) ANHYDROUS OXIDES.

95. Spinel (Ceylonite, Pleonaste, Automolite, Gahnite).
Monometric, usually octahedrons and rhombic dodecahedrons.
Crystals singly imbedded and attached, seldom gathered into
geodic clusters. Cleavage octahedral. Fracture conchoidal.
H. = 8. S.Gr. 3-5 4-9. Usually coloured, red-blue, green,
yellow, brown, or black. Lustre vitreous, sometimes

ANHYDROUS OXIDES. 61

resinous. Transparent, translucent, opaque. Cp.=RAl; R =
(Mg,Fe,Ca,Zn,Mn), and a part of the Al is sometimes replaced
by Fe and a little Cr. The varying composition gives rise to
distinguishable varieties of the mineral. Thus MgAl, red,
transparent, is spinel proper ; (Mg,Fe)Al, black, translucent
at the edges, is pleonaste ; ZnAl, greenish-black, translucent at
the edges, automolite. Bp. the red varieties infusible, but lose
their colour ; on cooling the colour returns. The black
varieties fuse to a dark-green bead. The zinc-spinels with
soda give oxide of zinc. Not affected by acids.

Spinel occurs as an accessory in granular limestone (pleon-
aste at Monzoni ; blue spinel in North America in several
places), in gneiss and talc-schist (the automolite of Fahlun) ; in
the vesicular cavities of volcanic rocks (Somma), and in allu-
vium (Ceylon). Sometimes spinel is a product of metamor-
phosis, e.g. of the action of syenite on limestone, at Monzoni.
Ebelmen has also succeeded in producing spinel artificially
by igneous means.

96. Magnetic Iron-ore (Magnetite, Oxydulated Iron). Mono-
metric, most usually in octahedrons and rhombic dodeca-
hedrons. Crystals imbedded and attached, and clustered in
geodes ; very generally massive in granular or compact aggre-
gates, also earthy (eisenmulm). Cleavage octahedral. Frac-
ture conchoidal to uneven. Brittle. H.=r5'5 6*5. S.G.=
4*9 5 '2. Colour iron-black. Streak black. Lustre metallic.
Opaque. Yery strongly magnetic. Cp.=FeFe, sometimes with
some Mg. Bp. fuses with difficulty, and with borax gives iron
reaction. The powder completely soluble in muriatic acid.

Magnetic iron-ore is found in separate beds (Arendal,
Dannemora) ; it also occurs as an accessory in many rocks,
especially in chlorite-chist, talc-schist, serpentine, granite,
syenite, basalt, and limestone.

62 MINERALS.

97. Chromic Iron-ore (Chromite). Monometric in octa-
hedrons, usually massive, in granular aggregates, and dis-
persed. Cleavage octahedral, imperfect. Fracture conchoidal
to uneven. H.=5'5. S.G. =4'3. Colour brownish-black.
Streak brown. Lustre semi-metallic. Opaque. Sometimes
magnetic. Cp.=FeCr, with some Fe replaced by Mg and
some Cr by Al. Bp. infusible. With borax it fuses to a green
globule. If fused with saltpetre and dissolved in water, it
yields a yellow solution, which shows the reaction of chromic
acid. Scarcely affected by acids.

Chromic iron very frequently occurs as an accessory in
serpentine (Islands of Unst and Fetlar, Shetland), rarely in
dolomite (Hoboken, New Jersey).

98. Hematite (Specular Iron, Red Iron-ore}. Rhombo-
hedral ; in rhombohedrons, pyramidal or tabular crystals,
which are singly imbedded or attached in groups (Specular
Iron, Micaceous Iron), or subcrystalline, frequently fibrous in
botryoidal, reniform, or stalactitic masses ; also granular,
lamellar, compact, and earthy textures (Bed Hematite, Fibrous
Red Iron, Scaly Red Iron, Red Iron Froth, Reddle, or Red Chalk,
&c.) The crystallised varieties have : Cleavage basal and
rhombohedral, imperfect. H.^5'5 6'5. S.G. = 4'5 5'3.
Fracture conchoidal to uneven. Colour iron-black to dark
steel- grey. Streak cherry- or blood-red. Lustre metallic.
The subcrystalline varieties have: H.=3'5 only. S.G.
4*5 4'9. Colour blood-red to brownish-red, sometimes pass-
ing over into steel-grey. Streak blood-red. Lustre dull.
Cp. Fe, sometimes with some Ti. Bp. both varieties become
black and magnetic in the reducing flame. In acids but slowly
soluble.

Specular iron (eisenglanz) includes the varieties with perfect
metallic lustre ; red iron-ore the amorphous varieties. The sub-
crystalline varieties of hematite frequently contain impurities,

ANHYDROUS OXIDES. 63

siliceous, argillaceous, &c. Itabirite is a granular variety of
the same mineral containing quartz, jaspery clay -iron ; reddle,
argillaceous iron. Hematite forms independent rocks and
beds, sometimes horizontally imbedded between the strata of
other sedimentary rocks. It also forms an essential constituent
of micaceous iron-gneiss and micaceous iron-schist. It is like-
wise met with as an accessory in many other rocks. At Vesuvius
and ^Etna it fills clefts in lava, or is found in vesicular cavities
of lava, where it is probably the result of the decomposition of
fumes of chloride of iron by the vapour of water (steam). In
other cases it is usually a product of metamorphism from
spathic iron and brown hematite. Again, it is sometimes pos-
sibly a direct hydrogenic formation (especially where it is
pseudomorphous of other minerals or dendritic on the surfaces
of rock clefts).

99. Titaniferous Iron (Titanic Iron-ore, Ilmenite, Crichtonite) .
Rhombohedral, isomorphous with specular iron. Crystals
imbedded singly, or attached in groups. Also massive, in
granular lamellar aggregates, or dispersed in grains. Cleavage
sometimes rhombohedral. Fracture conchoidal to uneven.
H.=5 6. S.Gr.=4'5 5. Colour iron-black to brown or
steel-grey. Streak black to brownish-red. Lustre semi-
metallic. Opaque. Cp.=Ti and Fe in various and probably
indefinite proportions, sometimes with some Mn, or Mg. It
will be seen that this composition admits of a near approach to
that of hematite, and in truth the division between the two is
not very definitely marked. Bp. infusible, with fluxes gives
the reactions of iron and titanium. If heated in concentrated
sulphuric acid, it gives a blue colour. Soluble with difficulty
in muriatic or nitric acid, titanic acid being separated.

Titaniferous iron is an accessory ingredient in many rocks,
especially in basalts and dolerites, also in talc-mica-schist
(Gastein), miascite (Ilmensee near Miask), granite (Aschaf-

64 MINERALS.

fenburg). Very frequent in river deposits (Menaccan in
Cornwall).

100. Braunite. Dimetric. Crystals usually small and in
pyramids resembling the octahedron, clustered in geodes and
in granular aggregates. Cleavage pyramidal, tolerably per-
fect. H.=6 6-5. S.G. =475 4-82. Colour iron-black to
brownish-black. Streak black. Lustre metallic, resinous.
Opaque. Cp. = Mn or MnMn. Bp. infusible. With borax,
phosphor- salt, or soda gives the reaction of manganese. Soluble
in muriatic acid, chlorine being evolved in the process.

Braunite occurs sometimes as an accessory in other rocks,
chiefly, however, in veins. (In the porphyry of Oehrenstock
near Ilmenau, Elgersburg in Thuringia.) This mineral and
similar manganese products very frequently form dendritic
coatings to the faces of clefts in rocks. These dendritic forma-
tions are usually exfiltrations from the mother rock.

101. Hausmannite (JBraunstein) . Dimetric. Crystals always
pyramidal, grouped in geodes. Cleavage basal, tolerably per-
fect, pyramidal less distinct. H. = 5 5*5. S.G.=47. Colour
iron-black. Streak brown. Lustre bright metallic. Opaque.
Cp. = MnMn. Bp. like oxide of manganese. Soluble in
muriatic acid, with disengagement of chlorine. In concen-
trated sulphuric acid, after a short time, assumes a bright red
colour.

Hausmannite is usually found in separate beds (Ilmenau in
Thuringia, Ihlefeld in the Harz), and would appear to be in
almost all cases a hydrogenic product, Mn having been first
dissolved in spring and other water, and having afterwards
absorbed more oxygen from the air. Daubree has, however,
shown the possibility of producing hausmannite by the reaction
of water in the state of steam upon chloride of manganese at a
red heat.

102. Polianite. Trimetric. Crystals usually in short prisms,

ANHYDROUS OXIDES. 65

vertically striped. Also massive in granular aggregates.
Cleavage brachydiagonal. H.=6'5 7. S.G-.=4'84 4'88.
Colour light steel-grey. Streak black. Lustre black metallic.
Opaque. Cp.=Mn. Bp. infusible ; on charcoal changes to
brown MnMn. Soluble in muriatic acid, with brisk effer-
vescence of chlorine.

Pyrolusite is sometimes a modification of polianite, sometimes
a product of the transmutation of manganite, a mineral which
we shall presently notice. The manganite is a compound of
Mn and water, and it has a strong tendency to part with its
water and absorb oxygen. Polianite is frequently found in
beds of the manganese- ores (Flatten in Bohemia, Johanngeor-
genstadt, Saxony). Pyrolusite is found in the same localities,
or associated with iron-ores (Siegen, in many parts of France).

103. Cassiterite (Tin-ore, Tinstone). Dimetric. Crystals in
short prisms or pyramids, very often twins, imbedded or at-
tached ; also massive, granular, or fibrous (wood- tin). Cleav-
age prismatic, imperfect. Brittle. H.=6 7. S.Gr.=6'3 7'1.
Colour usually yellowish-, reddish-, or blackish-brown ; rarely
colourless. Streak colourless or brownish. Lustre adaman-
tine or resinous. Translucent to opaque. Cp. = Sn, usually
with some Fe, Mn, Si, and Ta. Bp. unchangeable, on charcoal
with carbonate of soda reducible to metallic tin. Not affected
by acids.

Tin-ore is principally found in metalliferous veins, also as
an accessory, and especially so in plutonic rocks (greissen,
granite, and tourmaline rocks). Wolfram, tourmaline, beryl,
and topaz are almost always associated with this mineral.

Tin-ore in nature is doubtless in many cases a product of
wet processes (we find pseudomorphs after felspar in Corn-
wall) ; but Daubree has also proved that crystallised oxide of
tin may be formed by the action of steam on fumes of chloride
of tin.

66 MINERALS.

104. Rutile (Nigrine). Dimetric. Crystals always columnar,
frequently very thin, acicular and capillary, imbedded and at-
tached, frequently twins ; also massive, compact, or granular.
Cleavage prismatic, perfect. Fracture conchoidal. H.=6 6*5.
S.Gr.=4'18 4'25. Colour yellowish- or reddish-brown to black
(nigrine). Streak yellowish-brown. Lustre metallic adaman-
tine. Translucent to opaque. Cp.=Ti, with small quantity
of Fe. Bp. unchangeable ; with borax gives reaction of
titanium. Not affected by acids.

Rutile occurs only as an accessory ingredient in rocks ;
chiefly in greenstones and diorites, rarely in granite ( Warwick
in America) ; gneiss and mica-schist (Barre and Shelburne in
Massachusetts) ; or in granular limestone (Edenville in New
York).

Daubree has produced crystallised titanic acid by the action
of steam upon fumes of chloride of titanium.

(&) HYDROUS OXIDES.

105. Manganite. Trimetric, sometimes hemihedral. Crys-
tals always columnar and distinctly marked with vertical
stripings, frequently grouped in bundles or clustered in the
form of geodes. Also massive in fibrous, divergent, rarely in
granular aggregates. Cleavage, brachydomatic very perfect,
basic and prismatic imperfect. Somewhat brittle. H. = 4.
S.G.=4'2 4*4. Colour dark steel- grey to nearly iron-black,
frequently brownish-black. Streak brown. Lustre imper-
fectly metallic. Opaque. Cp. MnH. Bp. in matrass yields
water, with borax gives reaction of manganese. Perfectly
soluble in concentrated muriatic acid, chlorine being disen-
gaged. Slightly soluble in sulphuric acid, which colours it
pale red.

Manganite is found in separate beds with other manganese-
ores (Ihlefeld in the Harz, Ilmenau and Oehrenstock in

HYDROUS OXIDES. 67

Thuringian Forest). We have already noticed the tendency
of manganite to change into pyrolusite.

Psilomelane and Wad are two hydrous ores of manganese,
occurring frequently with other manganese ores, or as acces-
sories in rocks. They are crystalline, also amorphous, some-
times massive, in reniform, stalactitic, lamellar, and earthy
varieties. Cp. (of psilomelane) = RMn 2 + H, with Mn, Ba,
K ; (of wad) very variable, so that it is hardly to be called an
independent mineral : consists principally of Mn, Mn, and
H, with variable proportions of Ba, Ca, Cu, Co (earthy cobalt
or asbolan).

106. Limonite (Brown Iron-ore, Brown Hematite). Subcrys-
talline. In fibrous masses of globular, reniform, or stalactitic
shape. Also compact or earthy. H. = 5 5*5. S.G.=3*6 4.
Colour, clove-brown to yellowish- or blackish-brown, black.
Lustre silky, shining or dull. Opaque. Cp. = Fe 2 H 3 . Bp.
becomes black and magnetic, is fusible in thin laminae. With
borax it gives reaction of iron. Soluble in heated nitric
acid.

Limonite is a very abundant mineral, sometimes in inde-
pendent beds, sometimes as an accessory.

Gothite or Stilpnosiderite (FeH) is a mineral very closely
allied to limonite and frequently associated with it.

ii. Fluorides and Chlorides.

107. Common Salt (Rock-salt). Monometric. Crystals
always cubic ; usually in granular or fibrous aggregates or
massive. Cleavage cubic, very perfect. Fracture conchoidal.
Slightly brittle. H.=2'5. S.G.=2'1 2'2. Colourless or
grey, or yellowish, or reddish ; rarely blue or green. Lustre
vitreous. Transparent. Taste pure saline. Cp.=NaCl,

very often impure, containing F, Br, KC1, MgCl, and other

F 2

68 MINERALS.

salts. Soluble in 3" 7 parts of water. Liquefies on exposure
to moist atmospheres. Bp. decrepitates in matrass ; fuses on
charcoal and evaporates with strong heat ; tinges the flame
reddish-yellow, and if combined with microcosmic salt and
oxide of copper, it gives a beautiful blue flame.

Rock-salt is frequently met with as an independent rock in
sedimentary formations of every age. It also occurs as an
accessory ingredient in clay marls of the salt mountains
(Berchtesgaden) where it is in the form of cubic crystals
porphyritically imbedded. In each case it is a neptunian
product. It is found in a state of solution in sea- water, which
contains about 2'5 per cent .of salt. It occurs in the steppes,
in the sand of the Desert, in inland springs and lakes, and
finally as a sublimation at the craters of volcanos. We shall
have occasion to mention rock-salt again amongst the rocks.

108. Sal-ammoniac. Monometric, usually in uncrystalline
crusts, stalactites, or as an earthy coating. The crystals have
conchoidal fracture. H.=l 1'5. S.Gr.=l'5. Colourless, or
coloured yellow or brownish. Taste saline and pungent. Cp.=
NH 4 C1. Easily soluble in water. Bp. in matrass evaporates
entirely ; with soda emits a strong smell of ammonia. If
melted with phosphor-salt and oxide of copper, it colours the
flame a beautiful 1blue.

Sal-ammoniac occurs as a product of sublimation in the
clefts and fissures of volcanic rocks, and many lavas, also in
burnt seams of coal.

109. Fluor (Fluor-spar). Monometric, Cubic form very
frequent. Crystals single or in groups, attached, also massive,
in coarse granular and radiated aggregates, or amorphous and
earthy. Cleavage octahedral, perfect, so that the conchoidal
fracture is seldom observable. Brittle. H. = 4. S.Gr.=
3'14 3'19. Colour blue, yellow, green, and various. Some-
times colourless and limpid. Lustre vitreous. Transparent,

FLUORIDES AND CHLORIDES. 69

translucent, opaque. Cp.=CaF. Bp. decrepitates violently,
shows phosphorescence, and in thin laminae fuses to a clouded
mass, tinging the flame red. In a stronger flame the fused
product becomes infusible, and acts like lime. Is completely
decomposed by concentrated sulphuric acid, giving forth hydro-
fluoric acid.

Fluor-spar forms independent rocks of subordinate extent.
It occurs most frequently in metalliferous veins, from which it
has occasionally spread into the mother rock. In dolomite it
sometimes occurs as an accessory (St. Gotthard), and in geodic
cavities of the variegated sandstone at Waldshut. It is also
met with as a recent deposit from springs of water (Plom-
bieres). The last mentioned case proves that fluor-spar may
be produced by purely wet chemical process.

110. Cryolite. Trimetric (?). Hitherto only known in
amorphous single masses or thick crusts of coarse granular
texture. Cleavage basal, tolerably perfect. Brittle. H.=
2'5. S.G.=2'9 3'0. Colourless, greyish- white, or reddish.
Lustre vitreous, on the basal cleavage face mother-of-pearl.
Translucent. Cp.=NaF+Al 2 F 3 . Bp. very readily fuses to a
white enamel, tinging the flame reddish-yellow. In glass tube
gives the reaction of fluor ; on charcoal also it fuses easily,
but is decomposed, and leaves a deposit of alumina. In con-
centrated sulphuric acid it is perfectly soluble, giving forth
hydrofluoric acid.

Cryolite occurs in a separate bed or layer in the gneiss of
Arksutfiord in West Greenland.

in. Sulphurets. Arseniurets.

111. Galena (Blue Lead-ore). Monometric. Very usual in
cubes, more rarely in rhombic dodecahedrons, octahedrons,
and other forms. Crystals usually attached, clustered in
geodes, also botryoidal and reniform. Chiefly massive in coarse

70 MINERALS.

and fine grained or compact aggregates. Cleavage cubic, very
perfect. Sectile. H.=2'5 275. S.G.=7'25 77. Colour
lead-grey, sometimes with tinge of reddish colour, sometimes
iridescent on the surface. Streak greyish-black. Lustre me-
tallic. Opaque. Cp.^PbS, with frequently a small quantity of
silver, or also of Fe, Se, Sb. Bp in glass tube, evolves sulphur
and a sublimate of PbS. On charcoal decrepitates, fuses after
the sublimation of the sulphur, and finally yields a lead globule
and lead fumes. Soluble in nitric acid, with development of
nitrous acid and precipitate of sulphur.

Galena is met with as an accessory in many rocks, e.g.
sandstones (in the form of disseminated grains Commern in
the Eifel) ; in the argillaceous sphserosiderite of the Coal for-
mation, and elsewhere. Very frequently in veins of ore (in
the gneiss of Freiberg, in the Devonian strata of the Harz,
in mountain limestone of Derbyshire and Cumberland, in
granite of Linares) ; also in nests and irregular masses im-
bedded, which are usually met with in limestone or dolomite
(Tarnowitz in Silesia, Bleiberg in Carinthia, Alpuj arras in
Spain).

Although galena may very frequently be of hydrogenic
origin, it is not less certainly in many cases a product
of sublimation ; artificially it is formed in the cracks of
furnaces.

Gralena has given rise to many secondary products, such as
cerusite (PbC) ; pyromorphite (3Pb 3 P + PbCl) ; and mime-
tisite (3Pb 3 As + PbCl).

112. Blende (Zincblende, Sphalerite). Monoclinic, tetra-
hedral. The crystals frequently irregularly twisted, some-
times twin growth ; often massive, in granular, rarely in
fibrous or radiated aggregates. Cleavage very perfect ac-
cording to the rhombic dodecahedron. Very brittle. H.=
3'5 4. S.Gr. = 3*9 4'2. Colour, most frequently brown or

SULPHURETS. ARSENIURETS. 71

black, more rarely yellow-red, white or colourless. Lustre
adamantine to resinous. Semi-transparent to opaque. Cp.=
ZnS, sometimes combined with considerable quantities of FeS
(up to 23 per cent) and a little cadmium. Bp. decrepitates
violently, but is only fusible at the sharp edges. On charcoal
in the oxidation flame gives zinc fumes. Soluble in concen-
trated nitric acid, with precipitate of sulphur.

Its place and mode of occurrence in nature are similar to
those of galena, which is almost always associated with it. It
has been likewise found in the cells of ammonites of the
brown Jura and Lias formations, a fact which proves its partial
formation by wet processes.

113. Cinnabar. Bhombohedral. Crystals in rhombohedrons
or thick tabular, small and in geodes. Usually massive, in
granular, compact or earthy aggregates, dispersed or incrust-
ing. Cleavage prismatic. Fracture uneven and splintery.
Sectile. H.=2'25. S.G. = 8'99. Colour cochineal-red and
scarlet ; streak scarlet. Lustre adamantine. Translucent ;
opaque. Cp. = HgS. Bp. in matrass burns black; in open
tubes sulphur burns with a blue flame, and sublimes, yielding
fumes of sulphurous acid with black sublimate and a mirror
of metallic mercury. Soluble in nitro-muriatic acid (aqua
regia).

Cinnabar forms independent beds, appears as impregnation
of bituminous shale, or in veins (Idria), also forms incrustation
on clefts of many kinds of rock (granite, clay-slate).

114. Magnetic Pyrites. Hexagonal ; m rarely crystallised,
usually massive and disseminated, in lamellar, granular or
compact aggregates. Cleavage basal, perfect ; prismatic im-
perfect. Fracture conchoidal. H. = 3'5 4'5. S.G.=4'4
47. Colour between bronze-yellow and copper-red ; streak
grey-black. Magnetic. Lustre metallic. Opaque. Cp.=
Fe 7 S 8 , sometimes contains Ni. Bp. unchangeable in matrass ;

72 MINERALS.

in glass tube gives out S, but no sublimate ; on charcoal fuses
in reduction flame to a greyish black and highly magnetic
bead. Soluble in muriatic acid, sulphuretted hydrogen being
developed, and sulphur precipitated.

Magnetic pyrites occurs with metallic ores, also as an acces-
sory ingredient in many igneous rocks, especially diorite, in
Vesuvian lavas and in meteorites.

115. Pyrites (Iron Pyrites). Monometric, in various hemi-
hedral combinations. Crystals singly imbedded, or combined
in geodes and various groups ; also in globular and reniform
or fibrous aggregates, or massive. Cleavage cubic, imperfect.
Fracture conchoidal to uneven. Brittle. H.=6 6'5. S.Gr.=
4' 8 5. Bronze-yellow to gold-yellow. Streak brownish-
black. Lustre metallic. Opaque. Cp.=FeS 2 , with occasion-
ally small quantities of Au or Ag. Bp. in matrass gives out
sulphur and sulphurous acid, and afterwards acts like magnetic
pyrites. Scarcely affected by muriatic acid. Soluble in nitric
acid, leaving a precipitate of sulphur.

Pyrites is found in independent beds. It is also an essential
constituent of the species of granite called beresite. It is a
very frequent accessory ingredient in many rocks ; very fre-
quent in the crystalline schists, in diorite, limestone, in clay
rocks, in coal. It is no less frequent in metalliferous veins.

Pyrites is sometimes formed by the action of a solution of
copperas on organic substances, and this will account for its
often being found in the form of fossils. Wohler has produced
artificial pyrites by slowly heating oxide of iron, together with
sulphur and sal-ammoniac.

116. Marcasite (White Iron Pyrites, Hydrous Pyrites).
Trimetric. Crystals tabular or columnar, usually clustered
into groups termed radiated pyrites, spear pyrites, hepatic
pyrites, cockscomb pyrites, cellular pyrites, according to vary-
ing texture. Cleavage prismatic, indistinct. Fracture uneven.

SULPHURETS. ARSEXIURETS. 73

Brittle. H. = 6 6-5. S.G.=4'6 4'8. Colour greyish bronze-
yellow, inclined to green ; tarnishes very readily. Streak dark
greenish-grey. Lustre metallic. Opaque. Cp. like pyrites,
but more prone to decompose and turn to vitriol. Bp. like
pyrites.

Marcasite is found in separate beds, and as an accessory
mineral (Browncoal formation of the Carlsbad region, dolo-
mites of Tharandt in Saxony, and Cornwall).

117. Leucopyrite. Trimetric, usually massive and dissemi-
nated, granular, or fibrous. Cleavage basal. Fracture uneven.
Brittle. H.=5 5'5. S.G. = 7 7'4. Colour silver-white,
merging into steel-grey. Streak black. Lustre metallic.
Opaque. Cp.=FeAs 2 , almost always with some sulphur,
owing to admixture of mispickel. Bp. in matrass yields sub-
limate of metallic arsenic ; on charcoal strong smell of arsenic,
and a black magnetic residuum. Soluble in nitric acid, with
a separation of arsenious acid.

Leucopyrite is an accessory in many rocks, especially in
serpentine (Reichenstein in Silesia), and in metalliferous veins.

118. Mispickel (Arsenopyrite) . Trimetric. Crystals usually
short prisms, or tabular, singly imbedded, or attached in
groups; also massive, in granular or fibrous aggregates.
Cleavage prismatic, rather distinct. Fracture uneven. Brittle.
H.=5 - 5 5'6. S.G. = 6 6*4. Colour silver- white, inclining to
steel -grey. Streak black. Lustre metallic. Opaque. Cp. =
FeS 2 + FeAs. Several varieties contain Ag (Weisserz), Au, or
Co (Kobalt-arsenkies). In matrass gives first a red, afterwards
a brown sublimate of sulphuret of arsenic, finally a sublimate
of metallic arsenic. On charcoal the arsenic is dissipated, and
leaves a black magnetic bead, which acts like magnetic pyrites,
and sometimes gives cobalt reaction. Soluble in nitric acid,
with separation of arsenious acid and sulphur.

Mispickel is frequently met with in veins of ore, is also an

74 MINEKALS.

accessory ingredient in many rocks, e.g. the crystalline schists
(Kongsberg in Norway, Freiberg, Franconia in New Hamp-
shire), and serpentine in various localities.

119. Chalcopyrite (Copper Pyrites) . Dimetric. Tetrahedral.
Crystals usually small, frequently of regular twin growth, often
massive. Cleavage pyramidal, sometimes distinct. Fracture
conchoidal to uneven. Unlike pyrites, is very little brittle. H.=
3*5 4. S.G.=4'1 4'3. Colour brass-yellow, sometimes with
tarnish of gold colour and iridescence. Streak black. Lustre
metallic. Opaque. Cp.= Cu 2 S + Fe 2 S 3 . Bp. becomes black
on cooling, red, and fuses at a strong heat to a magnetic bead
of steel-grey colour ; with borax and soda gives a copper bead ;
when moistened with muriatic acid tinges the flame a beautiful
blue. Soluble in nitro-muriatic acid (aqua regia) with separa-
tion of sulphur.

Chalcopyrite is a very frequent associate of pyrites. Is
accessory in many rocks, e.g. tourmaline-granite, Predazzo,
Tyrol.

iv. Native Elements.

120. Sulphur. Trimetric. Crystals usually pyramidal,
singly attached, or clustered in geodes ; also globular, reni-
form, stalactitic ; with fibrous or compact structure. Cleavage
basal and prismatic, imperfect. Fracture conchoidal to uneven,
and splintery. Not very brittle. H.=1'5 2'5. S.Gr.=2.
Colour sulphur-yellow to straw-colour, or yellowish-grey.
Lustre resinous ; on crystal surfaces adamantine. Transparent,
translucent. Cp. = S, frequently mixed with clay or bitumen.
Bp. sublimates in matrass ; inflammable, and burns with blue
flame to sulphurous acid gas.

Sulphur occurs as an accessory in rocks, and also as a sepa-
rate formation in beds. It is formed by sublimation in the
clefts of volcanoes, also in the neighbourhood of burning coal

NATIVE ELEMENTS. 75

seams. Sometimes it is the product of the decomposition of
metallic sulphurets, or of the sulphuretted hydrogen of some
spring waters, which are decomposed by contact with the
atmosphere, and form deposits of sulphur.

Artificial crystals of sulphur may be produced in great per-
fection by dissolving sulphur in sulphuret of carbon, and set-
ting it to crystallise at ordinary temperature. Monoclinic crys-
tals of sulphur, which have not as yet been observed in nature,
are obtained on the cooling of melted sulphur.

121. Graphite (Plumbago). Hexagonal, rhombohedral, usu-
ally in six-sided, thin tabular or short prismatic crystals ; also
massive, in radiated, lamellar, or compact aggregates. Cleav-
age basal, very perfect, prismatic imperfect. Very sectile,
flexible in thin laminae. Feel greasy. H.=l 2. S.G.=
2 '09. Colour iron-black to grey. Streak black, with metallic
lustre, soils paper, used for pencils to draw and write with.
Opaque. Cp.=C, with some iron, and often containing im-
purities of Si, Ca, and AL Bp. burns with difficulty . If heated
with saltpetre, puffs up slightly.

Graphite is sometimes found in separate beds, and is then
probably the final product of the transmutation of vegetable
remains. It is, however, also found as an accessory ingredient
in igneous rocks (in trap at Borrowdale, Cumberland, in por-
phyrite at Elbingerode in the Harz, in granite boulders, Green-
land) ; in limestones (Lower Styria, Fichtelgebirge), or in
metalliferous veins (Arendal) ; finally as an essential consti-
tuent of graphite-granite, graphite-gneiss, graphite-mica-schist.
The igneous origin of some graphite may be inferred from its
presence in furnace slags, where it sometimes occurs in the
form of thin lamiiui'.

76 MINERALS.

v. Eesins. Organic Compounds.

122. Amber (Yellow Mineral Resin). It is exclusively found
in rounded masses of the shape of drops or fluid substance,
and frequently insects and fragments of plants are enclosed in
it. Fracture perfectly conchoidal. Little brittle. H.=2 2 '5.
S.G. = 1*1. Colour yellow or brown in various shades, fre-
quently with flame-shaped pencilling^. Lustre resinous. Trans-
parent, translucent. When rubbed,, becomes negatively electric.
Cp.=C 10 H 4 0. Bp. fusible y burns with a clear flame, and
agreeable smell.

Amber is a fossil gum-resin, the product of conifers or ter-
tiary lignites. It is found as an accessory in strata of the
Upper Chalk formation (Lemberg), the planercoal (Skutschin
Bohemia), in pebbles in the diluvium and alluvium of North
Germany, on the coast of the Baltic, and of Yorkshire and
Essex.

123. Bitumen (Asphalte, Naphtha, Petroleum, Mineral Pitch,
Mineral Oil).

Under the term bitumen are included a whole series of olea-
ginous and pitch-like substances, of which the most important
are naphtha and asphalt e.

(a) Naphtha, a volatile, and, when pure, colourless, oil with
bituminous smell. S.G.=07 0'84. Cp.=C 6 H 5 , fre-
quently mixed with paraffine, asphalte and the like.

(6) Asphalte, a hardened mineral pitch without oil ; massive
with perfect conchoidal fracture. Colour pitch-black.
Lustre resinous. Opaque. When rubbed gives a
strong bituminous smell. Cp. = C, O, and H in un-
certain proportions. Easily ignited, burning with a
bright flame and thick smoke.
Naphtha flows from the ground in considerable quantities

RESINS. ORGANIC COMPOUNDS. 77

(Persia, Pennsylvania, Amiano in Parma, Canada, Cali-
fornia, &c.).

Asphalte is found in many localities (e.g. at the Dead Sea ;
Trinidad, where there is a complete pitch-lake ; at Poldice in
Cornwall it occurs in granite).

An intermediate substance between naphtha and asphalte is
elastic mineral pitch or elat&rite (Castleton in Derbyshire).

All these bituminous substances are of vegetable or animal
origin, partly products of distillation of organic remains. They
frequently occur as admixtures in shales and other rocks,
which have received the name of bituminous ( Autun in France,
Bonn, Markersdorf in Bohemia, &c.)

124. Mellite (Mellilite, Honey Stone). Dimetric, usually in
pyramidal crystals, singly imbedded. Cleavage pyramidal, very
imperfect. Fracture usually conchoidal. Somewhat brittle.
H.=2 2-5. S.G. = 1'5 1-6. Colour honey-yellow to wax-
yellow, seldom white. Lustre resinous. Semi-transparent to
translucent. Cp. = A1(C 4 3 ) + 18H. Bp. it carbonises with
smell of burning ; on charcoal burns to a white ash, which acts
like pure alumina. It is readily and completely soluble in
nitric acid.

Mellite occurs as an accessory ingredient in Browncoal
(Artern in Thuringia, Luschitz in Bohemia).

78 ANALYSIS OF EOCKS.

CHAPTER II.

ANALYSIS OF ROCKS.

MICKOSCOPIC ANALYSIS.

IT not unfrequently happens that the various mineral
ingredients of a composite rock are so small and inti-
mately blended together as to be entirely undistinguish-
able even to the practised eye unaided by magnifying
power. A simple lens will often render great service in
this respect, but the aid of magnifying power may be
carried much further with the microscope. For the mi-
croscope very thin plates of a rock, so thin as to be
somewhat transparent, are cemented on glass, and by the
aid of a powerful instrument, textures apparently quite
compact are frequently resolved into a web of minute
crystals, or we find individual crystals become prominent
(porphyritic) in an actually compact matrix. The form of
these minute crystals is sometimes to be recognised, and
so serves as a guide to the determination of the mineral
in doubtful cases. If we further call in the assistance of
polarised light, we are enabled to pronounce, with greater
certainty, on the amorphous or crystalline character of the
compact mass, and on the character of the crystals which
by these means are brought to view.

Delicate investigations such as these no doubt require
the assistance of complicated apparatus and demand time,
so that they are quite out of the question for the geologist
on his travels ; but as we have said, much may be dis-
covered by a simple lens, which for the practical geolo-
gical purposes of the general inquirer is in most cases
sufficient.

MAGNETIC ANALYSIS.

An admixture of magnetic iron-ore makes many rocks
magnetic in their entirety, so as to affect the magnetic

CHEMICAL ANALYSIS. 79

needle, or if the iron-ore be present in small quantities
only, it may be discovered by abrasure with a sharp-
edged magnet, the magnetic particles of the powder so
formed clinging to the magnet like a beard. As, how-
ever, magnetic iron-ore occurs in many very different
rocks, its discovery does not often afford much help to the
geologist in determining the character of any given rock.
Fostemann and Delesse have made careful investiga-
tions of the magnetism of many different rocks. The
former is of opinion that by means of careful magnetic
experiments, we ought to be able to ascertain whether a
rock be of volcanic or neptunian origin, whether it has
been rendered metamorphic by heat, whether it has re-
tained its original position or been subsequently displaced
(vide Poggendorff's Aimalen^ 1859, vol. cvi. p. 106).
Delesse had previously discovered that almost all igneous
rocks were somewhat magnetic as well as many sedi-
mentary ana 1 metamorphic rocks. (Annales des Mines,
1849, vol. xv. p. 1, and Bulletin de la Soc. Geol. de
France, 1850, vol. viii. p. 108.)

CHEMICAL ANALYSIS.

The geological interest attaching to the chemical ana-
lysis of rocks is chiefly in respect of the nature of their
origin.

In the early stages of the science the analysis of com-
posite rocks was conducted by mechanically separating,
as far as possible, their several mineral ingredients, and
analysing each mineral species individually ; and this
method is still sometimes adopted where the parts are
very distinct and easily to be separated. Compact rocks,
such as basalt, were mostly considered as simple mineral
substances, and so analysed. When, however, it came to
be recognised that many apparently homogeneous rocks
were but mechanical compounds of several minerals,
chemical analysis was directed to the discovery of these
mineral constituents too intimately mixed to be distin-
guished by the eye.

Gmelin introduced the method of treating a powdered
mass of rock with muriatic or other acid, and so sepa-

80 ANALYSIS OF ROCKS.

rating it into a part soluble, and another part insoluble in
such acid. These two parts he separately analysed, and
reduced the results into chemical formulas. The object
he had in view was chiefly to discover the mineral con-
stituents of the rock. But this mode of analysis is in-
adequate for the purpose, since few minerals are wholly
soluble, or wholly insoluble, in acids, and therefore, in-
stead of the several minerals being separated from each
other, a part of each is dissolved and a part of each left,
and no definite result as to the original structure can be
attained. It is found that even the elementary consti-
tuents cannot be successfully so divided ; but that some
elementary substances are only partly dissolved and partly
precipitated by the process. Nevertheless, as a rough
approximate, and somewhat empirical mode of suggesting
rather than proving the constituents of a rock, it is still
sometimes employed, and may in certain cases be of use.

As the chemical character of minerals came to be better
known, less reliance was placed on chemical analysis as
a means of ascertaining and distinguishing the mineral
ingredients of rocks. A small number of elements are so
universal in their character that they enter into the com-
position of a very large proportion of the whole series of
mineral bodies, a very slight variation in their propor-
tionate quantities or combination serving to produce en-
tirely different minerals, or even the very same elements
in the same relative quantities wearing a totally different
mineral aspect according to slight differences in the con-
ditions of their original formation. Therefore it is that
chemical analyses have always hitherto failed, and it
would appear that they must always fail, to detect many
important mineral differences.

For instance, a rock containing 72 silica, 11 alumina,
2*8 oxide or protoxide of iron, 1 lime, 1*2 magnesia, 1*2
potash, 2 soda, and 0*4 water, may either be a granite, or
a gneiss, protogine, granulite, quartz-porphyry, felsite,
petrosilex, pitch-stone, trachyte-porphyry, obsidian, or
pearlstone ; and if we take a wider margin for the propor-
tion of silica, say from 62 to 72, increasing some of the
other ingredients in proportion, then a rock, such as we
have described, may be a trachyte, phonolite, or minette,
for in all the rocks we have named similar values of their

CHEMICAL ANALYSIS. 81

elementary constituents occur. Again, a rock, containing
49 50 silica, 12 alumina, 5 10 oxide or protoxide of
iron, 5 lime, 2 3 magnesia, 1 potash, 2 soda, and 1
water might just as well be a dolerite as a basalt,, or a
nepheline rock, leucite rock, diabase, diorite, gabbro,
hypersthenite, melaphyre, or porphyrite, for in like
manner those values occur in all these rocks.

On the other hand rocks, the same in mineral composi-
tion, may vary in the values of their chemical or elementary
ingredients 10, 20, or even 40 per cent.

The mineral character of rocks is therefore now sought
to be determined in doubtful cases by microscopic rather
than chemical analysis, or by tracing the different stages
of a rock's transition from a compact into a distinctly
composite state ; for many rocks (as we shall later have
occasion to show) are found to pass by gradual stages
from an apparently homogeneous mass into states where
their mineral ingredients become distinctly and separately
developed so as to be readily recognised.

Whilst chemical analysis was thus found insufficient for
determining the mineral character of a rock, it derived
a new importance from the igneous theory of the consti-
tution of the primary rocks, when these came to be con-
sidered as the products of the consolidation of a general
molten mass once the sole material of the earth's structure.
The different minerals then came to be regarded as of
subordinate importance in inquiring into the origin of
rocks, and their differing forms of crystallisation or
structure to be regarded but as accidental consequences of
slightly different circumstances attending the consolidation
of the formerly fused mass.

In this view even the sum of a separate analysis (if it
were possible) of all the minerals constituting a rock
would fail to present a complete picture of its aggregate
chemical character, unless the exact proportionate quan-
tity of each mineral could be also ascertained, which is
practically impossible, although it has been sometimes
roughly attempted.

These considerations led to the present mode of analy-
sis, which is now usually adopted in the case of all rocks
indiscriminately, whether compact or granular, homo-
geneous or distinctly composite. This is what is termed

82. ANALYSIS OF KOCKS.

In German the ( Bausch analyse ' (or collective average
analysis). It consists in pulverising a number of repre-
sentative specimens carefully selected from various parts
of the rock, and in mixing the powder thus obtained so
thoroughly as to make the portion taken for the analysis
a fair average sample of the whole rock.

The results of these analyses are sometimes combined
into chemical formulae such as those by which minerals
are described. For instance :

3(B)Si + 2KSi,
or(R) 2 Si 3

In such formulae we need hardly say there is always
more or less of speculation or theory involved.

The idea is to arrive at a view of the chemical consti-
tution of the original molten mass, and chiefly in the first
instance of the preponderance of the silica or other acid
in the compound. In other words, the object is to ascer-
tain if the original compound forming the rock, when in
its previous molten state, were acidic or basic in its
chemical character. It has been sought to express the
same idea more simply by giving the proportion of the
oxygen contained in the acids to that contained in the
bases of the compound. Thus if, in a compound say of
silica, alumina, peroxide of iron, potash and soda, the
silica contain 3 parts of oxygen to 1 of silicon, and
the alumina and peroxide of iron 1-J oxygen to 1 of
aluminum and iron respectively, the potash and soda 1 of
oxygen to 1 of potassium and sodium respectively, the
oxygen quotient in a neutral compound would be

3 : 11 I 1

(a proportion which has been actually found to obtain in
some rocks), and any variation of this proportion on either
side would cause the compound to assume an acidic or a
basic character ; thus,

5 : 1J : 1

would constitute an acidic compound, and

3:312

would constitute a basic compound.

Bunsen endeavoured to set up two typical rocks, to be

CHEMICAL ANALYSIS. 83

termed the trachytic and the pyroxenic, the former con-
taining much silica (acidic), the latter a preponderance of
bases (basic).

He endeavoured to bring all the igneous rocks under
one or other of these two heads, but soon found many
rocks of intermediate character. These he regarded as
mixtures of the two, or rather as the result of a combina-
tion of the two kinds of original material which he
believed to have existed at their formation.

He suggested the idea of the existence of two great
furnaces in the interior of the globe, containing these two
different mixtures in a molten state ; an idea which has,
however, not met with much general favour or acceptance.

Others have suggested, with more plausibility, that at
the time when the whole earth was fluid, its component
parts would be in some degree separated according to
their specific gravity, and the silica being the lightest of
the very abundant ingredients of the mass, would prevail
in greatest quantity at and near the surface, so that the
rocks which were first consolidated and the earlier volcanic
rocks would be acidic, the next formed igneous rocks
would be more basic, containing chiefly the lighter bases,
such as alumina, potash, soda or lime ; whilst the latest or
most recent igneous rocks would contain the least silica,
and principally the heavier bases, e.g. iron. It has also
been suggested that the older igneous rocks, as having
been formed nearer to the surface of the globe, would
probably contain more water than those of later origin.

These, then, are the chief problems which have been
suggested for solution by chemical means. The most
simple and useful of the chemical differences is that of the
varying proportion of silica. This quantity when ascer-
tained forms a clue to the proportion of the other ingre-
dients and general chemical character of the rock. Scheerer
has lately proposed that all the igneous rocks should be
divided into nine or ten classes, according to their quan-
tity of silica, without regard to their mineral character.

He has pointed out an easy mode of ascertaining the
proportion by fusing the portion of the powdered rock
selected for analysis with a certain proportion of carbonate
of potash or soda (about five times its weight). So much
of the silica as is more than the proportion required for a

o 2

84 ANALYSIS OF KOCKS.

neutral compound will combine with the potash or soda of
the carbonate salt, and drive off a proportionate quantity
of carbonic acid so that from the quantity of carbonic acid
so driven off, the quantity of silica contained in the
original rock may be calculated.

Without pronouncing on the correctness of any of the
foregoing speculations*, we may however confidently say
that for the purpose of lithological classification, an ex-
clusively chemical grouping of rocks. would be utterly
impracticable. How should the geologist pursuing his
labours in the field, or on the mountain, wait for the
tedious and uncertain process of a chemical analysis
before naming the rocks which come under his ken ? We
must, therefore, still adhere in the main to a mineralogical
designation and nomenclature, and all the more, as in
general we find the mineral characteristics of rocks very
much coincide with geological phenomena.

We need not, however, on this account disregard the
results of chemical analysis, which are doubtless of the
highest geological interest, and must prove of still greater
value when they shall have been more fully and exten-
sively carried out.

We propose, moreover, to use these chemical properties
for the purposes of our classification to the extent pro-
posed by Bunsen of dividing the igneous rocks into two
great classes, the acidic and the basic, merely warning
our readers that there is, so far as our present knowledge
extends, no rigid boundary between the two, and that
the state of our analytical knowledge in general is still
very imperfect.

With these remarks we present the reader with the
following extract from the analyses of Roth, as given in
his masterly work on this subject ( e Gesteinsanalysen ').
For the sake of brevity, the decimal figures have in some
instances been omitted or shortened to one figure.

* See post, pp. 367 et seq.

CHEMICAL ANALYSIS.

ll
Bi

3 OJ 3 00 ^ ,-< <* f~ CO

n j-iai

eo 6 6 b 6 rH 4*

e<iot>. ^>^(Mf-H

In id i

<O CO <M -* <N M CO <M CN

CO -H i-H rH

1 II!

O O i-i O O

si 6 ^ -

Syenitic
Granite

OOO -<*<oeokOOr-t

t^(M rH r-l

p o o o o o

6 CO 6 6 H r^ f^H

.3 N

M 1 1 1 1

00 CN rH 3

*~ 66 rn 6

(N^O OS>*COOSOSOO
<O <N rH

,L iiiia

o o o o o e* o

11 uu

AH rH O ^-i W tH

t^-iOi-H (NeOi-HOOCO

11 L.UU

6 <N rH 6 ^H A( ^H

T7 : 1 1 1 1 1

O O ' -^ ^l CO ^H (M

?t< OS O O O O O

t^.

000 000 0.(N

(M(>l6 6-^rH rHO

:1 1 1 1 1 I
J Ui

w5 ^i tooq-^t^b-^
II 1 1 1 1

O CO r-t O CO

1 1 1

O O O O .-i O
<N 00 ^-1 6 <N

t>-

I-HCO * (Mrjieooooco

OO rH rH

=U cliliJ,

0-*(N (N<MrH<MCOrH
t^. I-H
II 1 1

i^ 6 66 6

CO i t

U 4 4

O -< i-H O
t- i-H

ill

CO * W
r- * S?

t^rH CO OOCOrH^COrH
CO C<l

II 1 I 1 1 1

<Mt^ QO-^(MW5CO^-'
1 - i-H
II II II

B.SJ
g'S

ib 66 6
rH

1 1 II 1

O O C< ( I-H Tj< ^

^ w 66 66

CO-I-* CNCO<MOOOSCN
O C^ rH

1] iJ,iiJ,

rH t>- .t- (M <N 3 <N

II 1 1 1 1 1

99 9-^999

OS (N rH O CO <M rH

Mill
oo o -< -* o *

(NO r-l rH

c
t

o
<

I a

_>>

Jl -L

.81 i 8!i35

gq 5 3&&

Ji*i* 1-

II I Nil

i<J P^j ^^(^CCr^

ANALYSIS OF EOCKS.

Porphyrite

11 J.^rlJ,cli
IO rH

Greywacke
Sandstone

P O rH CO p CO O
TH O O O rH O C<1
OO

1 i I 1 1 1

O O <M TH CSI CO

ib o o o o o

Melaphyre

-MCOTH CMOCOCOCO(M
CO <N rH i 1 I 1

II Ml

O O O rH p p

TH O rH O rH rH
kO rH

Alum-Slate

OOp O p p p TH p

ib cc b cb cb M r~ o cb

CO C<>

II 1 1 1 1 1

OO rH O rH CN O

OO*O O rH O O <N
TH rH

IT S ILII

>0 CO 00 <M CO rH t^ <M 1

t^ CO rH rH rH rH

II III

O O rH 03 lO CN O

w "

lO TH lO (M O rH O
TH rH

00 rH

Oit^t>- ICrHrHrHCO'O

(M^OrH 5 <N TH iQ CO CO

ii i^iJ,

1 1 MIM

O O TH CO O O O

CO 00 00 CO O rH O

Oi CO O O (M rH C3

Diorite

COOOlM COOiOiCOt^rH
CO rH rH

u u^i

CD (M b CO O <N O
TH rH

Argillaceous
Mica-Schist

C5 TH *O O rH CO CD Th TH
t- <M rH rH rH rH

II 1 II 1 1
O O rH rH <M rH t-

kO O3 O O O O O

1
N

O (M -J rH
1 IJliJ

O O O O O O O

rnblende-
Schist

1!* H 7 i i

p p *p p kp p c^

TH rH

f-J

H^ CO !> rH C^ ^O OO 00 C^

OO p p C<l O rH
TH CO TH rH O rH O

}

OO GO OO TH rH CO CO
I!" 1 = U

OOO OOOrHrHO

to
o

VO rH rH rH rH
00 *0 t-

(M O O CDrHrHOOrH

i r 7

rH CO Jtr O5

rH rH CO rH O (M O
TH rH

CO rH

iCiOQC rHCOCOTHOTH

7> M C^ (M rH rH i 1

O O O O TH rH lO

CO CO

II Mill

O O CO CO O CO 5

CO !>. TH rH O O O
CO

O O5 O O rH O O

Dolerite

t--COt>- COTHOSCO'OCO

nrH rH i i
O <O C^ O TH
rH CO CO O O rH O
TH

Grey Gneiss

H clidrU

-02

s^i-f? 1L

l|^yi||i|

METAMOR]
SEDIMENTA

PHYSICAL STRUCTURE OF ROCKS. S7

CHAPTER III.

PHYSICAL STRUCTURE OF ROCKS.

TEXTURE.

BY the term texture, as applied to rocks, we mean
chiefly their physical structure, having regard to the size,
shape, and mode of adhesion of their individual mineral
particles. All rocks may be divided into two principal
classes, in respect of the size of their component parts.
Either the separate mineral particles of which they are
composed are large enough to be recognised as such by
the naked eye, or they are so small as not to be dis-
tinguishable in the general mass. In the former case
rocks are termed granular, in the latter compact. The
word granular is, however, usually only applied when
the different mineral parts are all of a granular shape
of nearly the same size, and are crystallised into each
other. If on the other hand a rock consists only of
grains, pebbles, or fragments mechanically cemented
together, it is termed according to its character either a
sandstone (arenaceous), a conglomerate, or a breccia, which
terms we shall explain more at large hereafter.

The term compact is usually only applied to a rock
when its particles adhere firmly and closely together
(without being fused into one mass like glass). If the
particles only lie loosely together so that the mass is
friable, then that condition is called earthy ; if they are
intimately blended and fused into a homogeneous mass,
then the state is termed vitreous or opalescent. The
vitreous and opalescent conditions are indeed essentially
different from the ordinary compact and earthy condi-
tions, inasmuch as in the former no individual particles

88 PHYSICAL STRUCTURE OF ROCKS.

are found, whilst the latter at best are but very fine-
grained. In extreme cases, however, this difference is
only to be discovered with certainty by means of polarised
light.

Using the terms granular and compact in their
wider sense, so as to include, on the one hand, the
sandstones, conglomerates, and breccias ; and on the other
the vitreous and opalescent rocks ; we may say that every
rock must necessarily either be granular or compact
that is to say, we either can, or cannot recognise their
individual component parts. A rock, for instance,
which is granular cannot at the same time, in the same
part, be compact, and vice versa. These conditions are
inconsistent with each other ; although transitions occur
from one state to the other, and although the same
mineral combination may at one place be granular and
at another compact.

In the case of composite crystalline rocks formed by
the cooling of matter previously in a state of igneous
fusion, the coarse-grained, fine-grained, compact, or
vitreous state is probably the result only of a more or less
speedy process of cooling. The slower the cooling pro-
cess, the more time would be allowed for the mineral
parts to form themselves into separate crystals, and the
more coarsely granular would the rock become ; the more
speedy the process, the more compact the rock would be,
or if the process were very rapid, then the rock might
even become vitreous.

The latter condition is almost exclusively confined to
those igneous rocks, which contain a large proportion of
silica ; in such as contain but little silica, the compact and
the vesicular state seem to be substitutes for the vitreous.
If individual mineral particles occur in the form of dis-
tinct crystals (porphyritically) in an otherwise compact
mass ; then we may regard this as a sort of intermediate
state between the granular and compact some of the
mineral constituents, more prone to crystallisation than
the rest, having developed themselves into crystals earlier
and more vigorously than those. The very same dif-
ferences of texture and condition may be frequently
observed in the products of artificial melting at fur-
naces.

TEXTURE. 89

In the case of compact rocks it is often very difficult to
determine whether the undistinguishable particles have
grown together in process of crystallisation, or are only
mechanically bound together; whether they consist only
of one mineral substance or a combination of several.

AVe now proceed to consider the special kinds of tex-
ture, structure, or state.

The texture of a rock is termed PORPHYRITIC when
distinct crystals or crystalline particles are distributed
through an otherwise compact principal mass or matrix.
The texture of the matrix or principal mass need not, how-
ever, always be compact ; it may be crystalline-granular,
or may exhibit many varieties of texture. Accordingly
the porphyritic texture may be subdivided into
(a) Porphyritic with compact matrix. Rocks exhibiting (
this texture are called, porphyries, independently of '
the character of their mineral ingredients.
(Z>) Porphyritic with granular matrix. Rocks exhibiting
this texture are not called porphyries, but only por-
phyritic; such for instance as many porphyritic
granites, with large crystals of felspar in the gra-
nular matrix.

(e) Porphyritic with shaly or schistose matrix. Mica-
schist for instance, if it contains garnets, thereby
becomes porphyritic.

The crystals thus porphyritically disseminated in a rock
may either belong to its essential constituents or they
may be accessories only.

SCHISTOSE (FOLIATED), SLATY (CLEAVED), SHALY
(LAMINATED), FISSILE are terms expressive of different
kinds of internal parallel texture of rocks. The German
geologists have the one term ' Schiefrig ' for all these
varieties of texture, the common element in all of which
is their tendency to split in the direction of a given plane.
This tendency may, however, be the result of very dif-
ferent causes, viz :

(a) By the parallel arrangement of certain minerals, such

as mica, chlorite, talc, &c. eminently cleavable in
one direction. Mica-schist is a rock of this
character, and the texture is termed schistose or
foliated.

(b) By some cause or causes, not to be discovered by mere

90 PHYSICAL STRUCTURE OF ROCKS.

ocular observation, the invisibly small mineral con-
stituents or particles of the rock are arranged so
as to produce a fissility or cleavage in the direc-
tion of a given plane, which very often cuts at a
considerable angle the plane or curved surfaces of
stratification. The rock itself has frequently a
compact appearance. The ordinary roofing slate
is an eminent instance of this texture, which is
termed slaty texture or cleavage.

the fine particles of the rock. Thus a fissile tex-
ture is developed in mud deposits, whether of marl,
clay, or sand. This is in truth nothing but a kind
of stratification on a small scale. The thin layers
of the rock are not in themselves of a fissile tex-
ture. Ordinary flagstones are of this character.
Or a similar texture may be occasioned by the
parallel juxtaposition of thin plates or lenticular
particles of the ingredients of the rock, thus for in-
stance the laminated texture of certain browncoals
may be traced to their construction from an accu-
mulation of actual leaves of trees, and a similar
texture of certain amygdaloids is owing to the shape
and position of the amygdaloidal particles.

These and similar textures more or less origin-
ating in the act and mode of deposition, and all of
which have a tendency to split in the direction of
their bedding, are called laminated or shaly, the
rocks themselves shales.

(d) Occasionally two of the above descriptions of texture

occur together ; fissile is a general term which
may be applied to all or any of the above-named
textures.*

* When we wish to be precise, we speak of the ' foliation of schist J
the 'cleavage of slate ,' and the l lamination of shale? Jukes.

See Jukes's Student's Manual of Geology (2nd edit.), pp. 265277.

See also Phillips's Manual of Geology (1855), p. 43, and in Glossary,
under heads of slate, schist, shale, laminated, flagstone, fyc.

See also Page's Advanced Text-Book, 3rd edit. pp. 74, 81 ; also in
Glossary under heads slate, schist, fissile, laminated, flags, shale.

See also Dana's Manual of Geology, pp. 71, 93, 95, 96, 100, 101,

All the above-named authorities agree, with very trifling excep-

TEXTURE. 91

As respects the different causes of the above mentioned
varieties of the fissile texture, we have seen that the thin
stratification productive of the laminated texture is in-
variably the consequence of the original construction of
the rock. But if rocks exhibit a slaty texture, which is
not parallel to their bedding, this must have another
origin than stratification.

According to the opinions of Sharpe, Haughton, Sorby,
and Tyndall, slaty texture or cleavage, when not iden-
tical with stratification, has in most cases been caused
by pressure in one direction (viz. at right angles to the
cleavage plane), applied to the rock either during or sub-
sequent to its formation that is to say, during consolida-
tion in the case of igneous rocks, during process of trans-
mutation in the case of the crystalline schists, and after
their deposition in the case of the sedimentary rocks, in
which it therefore seldom coincides with the plane of
stratification. (Vide Journ. Geol. Soc. of London,
1848-1849, and Phil. Mag., 1856.)

On the other hand, the conjecture of Poulet Scrope,
that lamination and cleavage may have arisen from friction
of some kind appears to us improbable. Nor can we
subscribe to the view advocated by Sedgwick, in his
otherwise masterly treatise on the structure of large
mineral masses (Trans. Geol. Soc. 1835, vol. iii. p. 469),
namely, that this texture is the result of a crystallising
force, although his view has been partially adopted by
Sharpe and Murchison. (Vide Siluria, edit. 1859, p. 34.)

Many rocks exhibit, variously developed, a marked
texture, consisting of parallel fibrous lines or particles,
with a parallel linear arrangement, called by Naumann,
Linear Parallelism. This linear parallelism is of two
kinds essentially differing from each other. It is either a
delicate zig-zag pencilling of slaty or schistose rocks, or
an elongation or extension of the particles or vesicular
cavities in one direction.

The linear foldings or pencilling of frequent occurrence

tions, in the nomenclature as laid down by Jukes, and which is
adopted in this translation throughout. It is almost identical with
that first proposed by Sedgwick in 1835. See his ' Structure of Large
Min -ml .Masses' in'Trans. of Geol. Soc. of London: 2nd series, vol.
iii. p. 480. TRANSLATOR.

92 PHYSICAL STRUCTURE OF ROCKS.

in gneiss, mica-schist, and clay-slate have the appearance
of having been occasioned by lateral pressure, although
such an explanation of the phenomenon is open to great
and various difficulties. Transitions are found from the
most delicate pencilling to the coarsest foliation.

Linear elongation or fibrous texture consists of a
kind of an apparent extension or elongation of individual
parts, or of all the particles of a rock in one principal
linear direction, by which a texture resembling the fibres
of wood is sometimes occasioned ; or else the vesicular
cavities of a rock, either empty or filled (amygdaloids)
are elongated in one prevailing direction. In the latter
case, we may easily explain the origin of the texture by
supposing the mass of the rock, during the period of its
consolidation and whilst yet soft, to have been flowing in
one direction. But it is much more difficult to ascribe a
cause to the linear extension of the particles in other
rocks, as, for instance, in some kinds of gneiss.

VESICULAR, SconiACEOUs(or Slaglike\ PUMICEOUS,
are textures of rocks containing cellular cavities more or
less rounded, and which are evidently the result of
gas bubbles, developed whilst the rock was in a soft
state either at the time of its original formation, or at
a subsequent period. If these cavities are only few and
isolated, then the rock is termed vesicular. If, however,
they are so numerous as to occupy an equal space with
the solid part of the rock, then the texture is scoriaceous,
and if the hollow part predominates over the solid, then
pumiceous (bimssteinartig). The shape of the cellular
cavities is most usually irregular, but sometimes very re-
gularly spherical, or pear-shaped, lenticular, and occasion-
ally the cavities are uniformly elongated in a particular
direction, as if stretched. All these differences of shape
may be easily explained by the circumstances under
which the vesicular mass attained its solid state, whether
it was in a state of quiescence, or was subjected to pres-
sure, or whether it was in motion, and whether such
motion was flowing or irregular.

This vesicular condition is most frequently found in
those igneous rocks which possess a compact, or at least
a very fine-grained or porphyritic principal mass occasioned
by rapid cooling. It never occurs in coarse-grained

TEXTURE. 93

igneous rocks, probably because these being always sub-
jected to a high pressure, crystallised very slowly. But
even sedimentary and metamorphic rocks sometimes con-
tain genuine vesicular cavities, in which case we must
always infer the rock to have been in a soft state during
the development of the gas which caused the bubbles.

Many rocks are porous without being vesicular, that is,
they are penetrated with irregular and often even angular
cavities, not the consequence of the development of gas,
therefore not to be termed vesicular. The differences
between porous and vesicular textures are sometimes very
difficult to determine.

To a certain extent almost all rocks are porous,
although not so to the naked eye, in the sense that they
admit of the percolation of water, even if but slowly.
Daubree has made many experiments upon this kind of
porosity, the result of which is communicated in the
Bullet, de la Soc. Geol. de France, 1861, vol. xviii. p. 183,
and Delesse has investigated the moist condition of rocks
arising from this cause. (Ibid. vol. xix. p. 64.)

A rock is said to be AMYGDALOIDAL when the vesicular
cavities are filled either wholly or in part with new
mineral substance. The filling of these cavities is always
a process subsequent to the formation of the rock. The
material for this purpose appears, as a rule, to have been
derived from the rock itself by a species of exfiltration,
and usually consists of chalcedony or quartz, or different
kinds of carbonic spars or zeolites, or sometimes of green-
earth, varying according to the character of the rock itself.
The arrangement of these mineral substances is often very
interesting ; concentric or horizontal layers, stalactites, and
stalagmites, are formed within the cavities, or we find a
crystallised geode or a compact mass.

We infer from all the attendant circumstances that the
formation of these amygdaloids must have been a very
slow process, and therefore have occupied a considerable
time in their completion. Hence, we may explain the fact
that the most recent of all the igneous rocks, the lavas,
although they are very often vesicular, are never amygda-
loidal ; whereas the frequency and completeness of the
filling up of the cavities increases almost in direct ratio
with the age of the rock.

94 PHYSICAL STRUCTURE OF ROCKS.

Such igneous rocks as are rich in silica are not only less
frequently vesicular, but their cavities, when they occur,
are less frequently amygdaloidal than those with little silica
in their composition, which probably arises from their con-
taining fewer soluble substances adapted to the formation
of amygdaloids, in particular, less lime and magnesia.

There are some appearances which may be easily mis-
taken for the amygdaloidal texture, but which only arise
from a concretion of separate mineral parts without
previous cavities. We shall mention these below under
the names of spherulite, globuliferous, nodular) and
variolitic.

OOLITIC texture is only found in limestones and iron-
stones, and it consists either in the entire mass being
composed of small globules, or a great number at all
events of such being contained in the mass. The glo-
bules are very much of the size and shape of peas or
grains of millet or lentils, and when broken exhibit a
concentric or radiated structure. Sometimes many very
small globules combine to form a larger ball. In the so-
called roestune the globules are grey, and usually inter-
nally compact, or somewhat radial in the common oolitic
limestone or oolite. They are more frequently white or
yellowish, and sometimes formed of concentric layers, or
they show an organic origin. In pisolite or peastone they
sometimes contain a nucleus of foreign substance, covered
with concentric layers or coatings of calc sinter, and these
layers also show a fibrous radial structure, so that we may
distinctly recognise the process of structure to have been
a repeated coating of a grain of sand.

In oolitic ironstone the grains are partly spherical,
partly lenticular. In bog-ore they exhibit a concentric
structure, and sometimes attain considerable size, culmi-
nating in reniform iron-ore.

The origin of this texture is only to be recognised with
certainty in the case of pisolite ; in the other similar
formations it is more or less wrapped in obscurity, and
especially in the Great Oolite beds it is still very pro-
blematical. L. von Buch observed a kind of oolite for-
mation on the shores of the Canary Isles very analogous
in its apparent origin to the pisolite. Virlet d'Aoust
found a species of oolite in the Gulf of Mexico produced
by the coating of minute insects' eggs with lime (Comptes

PARTICULAR STATES OF ROCKS. <J5

Rendus, 1857, vol. xlv. p. 865). Some recently formed
limestones, on the surface of coral reefs, are occasionally
oolitic. Many oolites appear to be formed entirely of
small and almost spherical shells (these are strictly speak-
ing not genuine oolites). Deicke communicated a careful
observation of the texture of roestone in the Zeitschrift
f. d. ges. Naturw., 1853, p. 188, and more recently in the
Transactions of the Lyons Academy, 1853. Fournet
published a comprehensive treatise ' Sur la Formation des
Oolites Calcaires.'

In many of these rocks it would appear that the round
grains are, in fact, only the result of a peculiar concretion
of the homogeneous mass.

SPHEKULITIC, or GLOBULIFEROUS (Dana). A tex-
ture so named, somewhat similar to the oolitic, occurs in
some felsitic igneous rocks, most distinctly in pearlstone.
The round grains consist of pearl-like globules, or simply
of compact felsitic concretions.

Another variety of a similar texture sometimes occurs
in basalt, dolerite, or phonolite, where it appears that the
rock by a singular process of decay has resolved itself
into grains of a tolerably round shape.

NODULAR texture is closely allied to the oolitic, or some-
times to the porphyritic, and consists in this that the
mass of the rock contains small rounded or lenticular
or somewhat elongated concretions of a firmer and more
compact substance than itself. Under certain circum-
stances this appearance is termed spotted, variolitic, or
pock-marked.

There also occur in rocks, but in a very subordinate
degree, those states which in minerals are termed SPARRY,

FIBROUS, Or ASBESTIFORM.

PARTICULAR STATES OF ROCKS.

There are certain states or conditions (in part identical
with the above-mentioned textural phenomena) which,
although they frequently alter the very nature and
properties of the rock into which they enter, are never-
theless not always considered a sufficient reason for
giving a distinct name. This is not a consistent mode
of treatment, for there are many cases in which rocks
of precisely the same essential - mineral constituents

96 PHYSICAL STRUCTURE OF ROCKS.

are called by different names, by reason only of a dif-
fering texture ; and, again, in cases where a series
of rocks form a long but gradual chain of transition or
gradation between two extremes of different character, it
is the custom to give distinct names to many members
of the series arbitrarily selected, and which can only be
regarded as links in the chain. Still more inconsistent is
it when the same conditions or properties are used in one
case as a reason for a distinction, and in another not.
But if we would avoid these and similar inconsistencies,
we should be compelled to throw over the existing nomen-
clature of rocks altogether, and substitute an entirely new
one, which would be more hazardous than the inconsis-
tencies themselves.

We will now proceed to describe the most important of
these special states in rocks, only observing in the outset
that the terms used for denning the mere states are fre-
quently also used more generally to designate the rocks
themselves, and they sometimes even embrace a number
of different rocks.

1. Lava is not a definite rock, but is the name given to

every rock which has been originally poured forth
from a volcano in a state of igneous fusion. Thus
we distinguish dolerite-lava, basalt-lava, trachyte-
lava, &c.

2. Wacke is the name given to a somewhat decomposed

state of igneous rocks poor in silica. The mass
has become more or less soft, almost earthy, of a
yellowish or brown colour, and its mineralogical
structure quite unrecognisable and only to be
traced by transitions from the fresh state of the
original rock. In subsequent pages we shall have
occasion to speak of dolerite-wacke, basal t-wacke,
melaphyre-wacke, greenstone-wacke, &c., or we
shall use the adjective ( ivackenitic' * to designate
this state of those rocks (wackenitic dolerite, &c.)

3. Porphyry is the general designation for all porphyritic

rocks with compact main mass or matrix, whereas
those with a granular matrix are only termed por-

* We have here been compelled to coin an adjective for the Ger-
man ' wackenartig,' an equivalent for which we have been unable to
find in English text-books. In analogy to porphyritic, granitic, &c.,
we trust the term may meet with acceptance. TRANSLATOR.

PARTICULAR STATES OF ROCKS. 97

phyritlc. Therefore we distinguish between quartz-
porphyry, mica-porphyry, trachyte-porphyry, and
porphyritic granite, trachyte, <fcc. The quartz- or
felsite-porphyries however (with compact felsitic
matrix) are frequently, par excellence, termed por-
phyries without further designation.

4. Amygdaloid (Mandelstein, Germ.) is the name given

to every rock originally vesicular, whose cavities
have in course of time become filled with mineral
substance; hence there are basalt-amygdaloids,
melaphyre-amygdaloids, &c.

5. Scoria or Volcanic Slag, Scoriaceous, Slag-like, are

terms expressive of' very open cellular states of
basalt, trachyte, or other volcanic rock.

6. Pumice, Pumice Stone, Pumiceous. These terms are,

properly speaking, only expressive of the state or
condition of certain rocks ; but this state is, ge-
nerally speaking, confined to three kinds of rock
trachyte, trachyte-porphyry, and obsidian, whose
composition is essentially one and the same.

7. Schist, Slate, Shale, are general terms for rocks con-

sisting of very different mineral ingredients. The
individual rocks are distinguished accordingly, e. g.
as mica-schist, chlorite-schist, &c.,or clay-slate, &c.,
or bituminous shale, argillaceous shale, &c. ; or the
adjectives schistose, slaty, shaly, are used in con-
junction with the mineralogical name of the rock.

8. Sandstone, Arenaceous, are general terms applied to

rocks, consisting of a mechanical compound of small
rounded or sometimes angular siliceous grains,
usually quartz.

9. Conglomerate is the universal designation for rocks

consisting of rounded stones or pebbles, mechani-
cally bound or cemented together.

10. Breccia is a general term for rocks consisting of

angular fragmens, mechanically cemented together.

11. Tuff, Tufa. These terms doubtless in the first

instance were used to express a loose, or little
adhesive state of rock.

Tufa is now principally used to denote an earthy
compound of volcanic products of the most various
kind, and

98 PHYSICAL STRUCTURE OF ROCKS.

Tuff is chiefly applied to certain calcareous or
siliceous deposits at the mouths of springs, very
porous, and frequently very firm and tenacious ;
in which case they are termed travertine.
The four last states in the preceding list are also uni-
versally made use of as separate classes of rock in them-
selves, and as such they cannot indeed be well dispensed
with, unless we would give separate names to each of the
endless variety of rocks in each of those states ; a task
not easily possible, nor are the varieties of rocks them-
selves of sufficient importance to deserve such distinction.

CONCRETIONARY STRUCTURE.

A molecular arrangement quite distinct from crystal-
lisation causes clusters of particles to segregate themselves
round centres, or otherwise present various and singular
appearances and shapes, which have received different
names.

Spherical concretions, which are very different from
conglomerates, are frequently found in sandstones, clay
rocks, marls, limestones, dolomites, quartz-porphyries,
pitchstones, and greenstones. This structure has given
rise to various names the oolite is an instance, so
called from the egg-shape of the concretions ; pisolite
is so called from its pea-shaped concretions, &c. Many
concretions are compact, others are hollow, and their
interior is sometimes garnished with crystals forming what
is called a geode, a little crystal grotto ; or sometimes a
small concretion is found loose in the hollow interior of
the larger one, so as to rattle in it when shaken (clapper-
stones). Some concretions are grouped together like
clusters of grapes, or in irregularly kidney-shaped masses.
These pass over into the nodular or massive concretions
(Germ. Steinwulste, Schlangensteine, Lb'sskindel, &c.).
Others are lenticular in shape, and are called swellings,
or septaria. The latter is the special designation for
lenticular concretions irregularly cleft in their interior,
and frequently into pentagonal clefts on the outside.
The clefts are frequently filled again with new mineral
formations such as calcspar, brownspar, or ironspar. If
their surface be exposed and much washed away by water,

CONCRETIONARY STRUCTURE. EXTERNAL STRUCTURE. 99

it sometimes occurs that the veins of spar, as being harder
than the coating of the concretion, protrude and show a
kind of network.

These singular structures have been well described by
Ehrenberg, Parrot, and Glocker with engravings. Ex-
tracts from the treatises of Ehrenberg are to be found in
v. Leonhard und Bronn's Jahrbuch, 1840, pp. 680 and
741. The treatise of Glocker on the Laukasteine ap-
peared in Breslau, 1854.

Stylolites are a very singular formation in certain lime-
stones, dolomites, or marls ; they consist of irregular and
longitudinally striped cylinders standing at right angles
to the rock's stratification, and often ended abruptly.
Quenstedt endeavoured to explain their origin by sup-
posing them to consist of spaces left by marine animals
which had risen perpendicularly in the rock whilst yet
soft, the tubes or spaces so formed being afterwards refilled.
(See von L. und B. Jahrbuch, 1837, p. 406.)

Cone in Cone. Concretions of a conical shape marked
with concentric rings, are sometimes to be found in certain
marls or marly limestones (in German these concretions
are called Tuten, and smaller and more pyramidical con-
cretions of the same kind are termed Nagel).

No satisfactory explanation of the last three singular
forms of concretion has yet been given.

SPECIAL FORMS OF EXTERNAL STRUCTURE.

There are certain other phenomena of rock structure
(chiefly of their outward structure) which should not re-
main entirely unnoticed here. We will, therefore, pro-
ceed to mention them, merely premising that they are
incapable of systematic arrangement, being individual in
their character and unconnected with each other.

Stalactites are formations produced in caverns or vesi-
cular cavities after the manner of icicles, and resembling
them in form. They are caused by the dropping of
water holding some mineral in solution, and leaving
behind a deposit or incrustation thereof. The mineral is
usually calc-spar, barytes, aragonite, chalcedony, brown
hematite, manganese spar, pyrites, or the like. If the
incrustations, on the other hand, have been formed on the

100 PHYSICAL STRUCTURE OF ROCKS.

floor of the cavern or cavity by the drops when fallen,
and have so grown upwards, they are called Stalagmites.
Both stalactites and stalagmites are frequently met with
in caverns of limestone and dolomite, where they are
occasionally developed in extraordinary beauty and size.
In vesicular cavities they are similarly formed, but of
course smaller in size. Their original, normal position is
necessarily perpendicular. If they are found in any other,
that is the consequence of movement during or subse-
quent to their formation.

Dendrites (Dendritic) are terms applied to certain ex-
ternal crystallisations or deposits, usually arborescent in
form, which are found incrusting the surfaces of joints
and fissures in many rocks. These dendrites usually
consist of oxide of manganese, sometimes of oxide of iron.
Their origin appears to resemble that of the flowers of ice
on window panes, or the so-called silver trees.

Slickenslides, Friction Surfaces (Germ. Tlutschflaclien,
Reibungsjlaclien, Schliffflachen, Spiegelftachen, or Har-
nische). The surfaces of solid rocks are sometimes found
to have been naturally smoothed or polished, and also
furrowed or scratched in some one direction. This phe-
nomenon occurs in the most various kinds of rocks, some-
times in the interior of the earth, sometimes on the exposed
surface of the rock. When it occurs in the interior of
the earth, it has been invariably caused by masses of rock
pushing and shoving against each other, and forms one of
the clearest proofs of such movements having taken place
in the solid crust of the earth. Friction surfaces when
met with on the exposed face of a rock may no doubt
have been likewise caused in the same manner, and have
been laid bare subsequently, but in fact they have very
often been caused by the progressive movement of a glacier
rubbing over the surface of the rock. These latter friction
surfaces may be distinguished from the former kind by
the uniform direction of their furrows, always correspond-
ing to the indications of the valley, and further by their
never exhibiting protuberant masses between the furrows,
as is sometimes the case with the others. They are to
be met with in districts where glaciers once existed.
Floating ice is said sometimes to produce similar marks on
rocky sea-coasts.

EXTERNAL STRUCTURE. 101

Many hard rock surfaces exhibit a peculiar smoothness
with at the same time a wavy conformation or a furrow-
ing in one particular direction. It has been observed
that sand set in motion by the wind and driven against
the surfaces of rocks for very long periods of time, has
produced the like singular abrasions. This phenomenon,
first described by Naumann (who ascribed it to glacial
action), is observable in certain rocks at Wurzen, in
Saxony. (See v. L. und B. Jahrb. 1844, pp. 557, 561,
680; 1848, p. 497.)

It is familiar to every one how running water will
gradually round off and eat into the hardest rocks.
The singular phenomenon of what are called pot-holes
or ^iant-holes deserve special mention. These circular
hollows are formed at waterfalls or rapids by whirl-
pools carrying sand or pebbles round and round, and so
gradually scooping out a smooth round hollow. Basins
of this kind are found in river beds from a few inches to
many feet in diameter, and even over the height of a man
in depth. In places where the origin of these basins is
not to be explained by any existing waterfall or stream,
we must presume the former existence of such.

Somewhat analogous to the pot holes are the so-called
f Karren* or ' Karrenf elder] which are terms of Swiss
geologists for certain rill marks hitherto only observed on
limestone and dolomite rocks. They usually only occur
in lofty mountain districts, and are very frequent in the
Alps. They consist of gutters of from a quarter of an
inch to two feet wide, washed out of the face of the rock
by the rain, and following the lines of its steepest in-
clination.

Rocks locally possessing different degrees of hardness
when exposed to the weather and the action of rain often
present a singular jagged, glandular, or honeycombed
appearance from the unequal degree of resistance of their
parts. Thus, for instance, the quadersandstone of the
Saxon Switzerland, the argillaceous gypsum of the Kiff-
hauser, &c.

The traces of raindrops are not unfrequently found on
rock surfaces. These raindrops must have fallen during
the formation of the stratum, probably at ebb tide, mak-
ing small holes surrounded with raised rings. These

102 PHYSICAL STRUCTURE OF ROCKS.

holes have then been covered by the next stratum, and so
preserved for all time, like the ripple- and current-marks,
which are also of frequent occurrence on the surfaces of
some sedimentary rocks. Vide Froriep's Neue Notizen,
1839, vol. xi. p. 134 ; Ann. d. Sc. geol. 1843, p. 61 ;
Compt. rend. 1861, vol. 53, p. 649; Lyell in Koyal
Institution of Great Britain, 1851-4, Cepr. und Geologic
(translated 1858), i. p. 390 ; i. p. 150.

Animals also take part in the transformation of rock
surfaces. Certain kinds of mollusca on the sea coast
(Pholades) have the peculiar habit of burrowing several
inches deep into limestones or dolomite rocks, and even
into clays as well as much harder rocks ; (as, for instance,
mica-schist), so as by degrees to perforate the whole
surface. Ancient lines of coast are sometimes to be re-
cognised by means of their appearance.

Rounded Stones, Gravel) Shingle, Pebbles, or Boulders.
These stones have usually been wholly or partially
rounded by the action of water. There are, however,
such as have been rounded by the motion of glaciers, and
some even appear to have been rounded in clefts of
rocks, the sides of which have been much agitated.

There are also some special points respecting them
which deserve attention. In the first place most pebbles
are not spherical, but flattened and lenticular or elon-
gated, egg-shaped, &c. This very universal law is evi-
dently the result of an unequal degree of resistance to
waste presented by the stone in the direction of one or
more normal axes. In the case of rocks of slaty texture
or the like, this phenomenon may be readily conceived ;
but in the case of compact or granular rocks without a
trace of fissile or laminated texture, it is more remarkable,
and points to some parallelism of texture or structure
which has hitherto escaped observation.

The boulders or pebbles formed by glaciers sometimes
exhibit grooves or scratches on their surface.

At the foot of the Alps in the neighbourhood of Vienna,
many pebbles and boulders have been formed showing
deep grooves and forcible impressions, and some which
are partially broken and pieced together again.

In some conglomerates (as in the Nagelflue of St. Gall)
pebbles are found partly forced into each other (these are

EXTERNAL STRUCTURE. JOINTED STRUCTURE. 103

usually of limestone), and in other conglomerates, for in-
tance at Waldenburg in Silesia, there are pebbles which
have been cleft asunder, their several parts somewhat dis-
placed, and so cemented together again. But perhaps the
most remarkable of these phenomena are the dolomitic
limestone pebbles in a conglomerate at St Lauretta in
the Leitha mountains, many of which are hollow.

Much has been written on these peculiar forms and
phenomena, as appearing in pebbles. We have referred
to the greater part of such treatises in a former work
(vide Geolog. Fragen, 1858, pp. 198212), and will only
here add a reference to some later treatises, viz. :

WUrttmlerflcr in von L. & Br. Jahrb. 1859, p. 153.
Deicke, ibid. 18(30, p. 219.

(.'nrlt, ibid. 1861, p. 225.
Serggeist, 1860, p. 382.

Sorby, On the Direct Correlation of Mechanical and Chemical
Forces.

JOINTED STRUCTURE.

All large masses of rock are internally cleft by fis-
sures or joints, and thereby divided into solids of different
size and form. The general cause of this jointed structure
of the mass is evidently contraction which, in the case of
the igneous rocks, in all probability took place during
cooling ; in the case of the sedimentary during the process
of their drying; and in the case of the metamorphic, which
they inherited from the sedimentary, or which was re-
newed during the process of metamorphism.

In most rocks the jointing is irregular, dividing the
rock into irregular masses ; frequently, however, a cer-
tain degree of regularity is exhibited i.e. the dividing
fissures observe one or more prevailing directions, and are
at definite distances from each other, so as to form a
severance into tolerably regular plates, columns, paral-
lelopipeds, or spherical masses.

This so-called jointed structure deserves to be here
described with some particularity, although it has no
connection with the mineralogical composition of the rock,
and solely results from the circumstances attending its
original formation, and especially its solidification.

Tabular Jointing. The rock's mass is split into parallel
plates or tables, and these, unlike flagstones or strata,

104 PHYSICAL STRUCTURE OF ROCKS.

have not been successively deposited one over the other,
but were all formed simultaneously and subsequently to
the first formation of the rock. This constitutes, indeed,
the characteristic distinction between stratification and
jointing the former being the result of successive super-
position, the latter of the splitting of a previously formed
mass. Tabular jointing occurs most frequently in the
igneous rocks, less frequently also in the sedimentary
and metamorphic.

A modification of the tabular structure sometimes
occurs, consisting in a curvature of the individual plates,
which are frequently very thin. This is called in German
Schalige absonderung, ' conchoidal jointing.'

Columnar, Subcolumnar, Prismatic Jointing. The
rock's mass is split into columns of from 3 to 9 faces,
usually 5 or 6 faces, and the thickness of the pillars in
each place is tolerably uniform, but in different places
varies from a few inches to several feet. The length of
the columns is of course unequal. Some are known more
than 200 feet long. These columns are, however, usually
cross-jointed i.e. split into shorter blocks by means of
cross courses or horizontal fissures at right angles with
the first set of joints. This jointing is regular or irre-
gular, it sometimes exhibits rounded surfaces, indicating
in that case that the pillars were formed by the joining
together of spherical masses (as may be clearly seen,
indeed, in some places).

Columnar jointing may be observed with peculiar fre-
quency and beauty in basalt, but it also occurs in diabase,
diorite, aphanite, and quartz-porphyry ; less frequently in
trachyte, granite, or syenite. In all these rocks this
jointing is evidently the result of a special process of
cooling ; moreover, the axes of the columns are for the
most part at right angles with the plane of the larger
cooling surface. In lava streams, for instance, perpen-
dicular to their surface ; in veins or dykes of basalt, per-
pendicular to the walls of the cleft. If the larger cooling
surface has been curviform, the columns at right angles
to it will be found bent or radiating.

But sedimentary rocks sometimes exhibit the pheno-
menon of columnar jointing. In them it is probably owing
to having dried more rapidly from one side of the mass,

JOINTED STRUCTURE. STRATIFICATION. 105

and in rare cases, locally, to the effect of heat from con-
tact with igneous rocks.

Parallelopipedic, Cuboidal, or Rhomloidal Jointing.
The rocks are severed by joints which traverse them in
planes of three different directions, which, if they cross
each other at right angles, produce cubes or rectangular
parallelepipeds ; if at inclined angles, rhomboidal solids.
In sedimentary rocks the direction of one of these planes
is frequently determined by the bedding, but in igneous
rocks all three sets of joints are independent of such
influence.

Spherical, Globular, or Spheroidal Jointing. Some
rocks are entirely composed of spherical masses, the in-
terstices or spaces originally existing between them being
now filled with a mass of similar substance and compo-
sition, but so that the jointing is still apparent. These
spherical masses are often formed of concentric layers,
and sometimes ranged over each other in columns. In
the latter case the globular and columnar jointing may be
said to be combined.

A modification of the spherical structure is what is
called ball and socket jointing, in which single masses
with rounded heads more or less approach the globular
shape, and seem to fit into a cavity on the other side of the
fissure.

This passes over into irregular or massive jointing,
which occurs more or less distinctly in rocks of the most
different description.

All jointing becomes much more distinctly apparent
when the rock is weathered, and it sometimes even ap-
pears as if the structure were solely caused by decay of
the rock. Nevertheless, it is very probable that even
in these cases a disposition to the severance previously
existed.

STRATIFICATION OF ROCKS.

We have already spoken of the lamination of shaly
rocks as consisting of a structure dividing those rocks in
planes parallel to their bedding, and originating in the
mode in which they were formed i. e. by successive
layers of deposit.

106 PHYSICAL STRUCTUKE OF ROCKS.

The same phenomenon on a larger scale is called strati-
Jication, and the individual members of the series are
termed strata. Page observes in his Adv. Text Book,
6 Thus ' (speaking of stratified rocks), ' the terms stratum
and bed are used when the deposit is of considerable
thickness ; layer or band when it is thin, and holds a
subordinate place among the other beds ; and seam when
a rock of a peculiar character occurs at intervals among
a series of strata. The miner, for example, speaks of a
seam of coal occurring among strata of clay and sand-
stone, and of a band of ironstone occurring in a bed of
shale.'

The horizontal line on the surface of strata is termed
the strike, and their steepest inclination towards the hori-
zontal plane is termed the dip.

Stratification is exhibited more especially and distinctly
in the sedimentary rocks, but it is also frequently to be
recognised in the metamorphic, and even the igneous rocks
may exceptionally be actually stratified, if, for instance,
successive streams of lava have overflowed each other,
each consolidating separately.

SHAPE AND BEDDING* OF EOCK MASSES.

Both the shape and the mode of bedding of rock masses
are dependent on the mode of their original formation.

Igneous rocks neither exhibit any certain shapes nor
any uniform bedding in relation to other rocks, whereas
in the case of sedimentary rocks and their offspring, the
metamorphic, both shape and bedding have some relation
to certain general laws.

The form assumed by igneous rocks depends to some
extent on the shape and size of the opening by which
they forced their passage from the interior of the earth.
They accordingly fill clefts more or less regular in form,

* The word ' BEDDING ' is used indifferently throughout this work
in speaking of all rocks, whether stratified or not. It is taken as the
equivalent of the German ' Lagenmg? We are aware that in England
this has not been always usual ; nevertheless, some general word must
be adopted. f Mode of occurrence/ ' position/ 'lie,' &c., are all ex-
pressions which fall short of the idea intended to be conveyed.
TKASTSLATOK.

SHAPE AND BEDDIXG OF ROCK MASSES. 107

or they occupy larger irregular spaces between other
rocks, or they have overflowed through craters, and create
accumulations after the manner of lava in streams, in
plains, or conical heaps.

Where the igneous rock forms a clear and evident
filling of a previously existing cleft or fissure, it is termed
a dyke or vein. The latter term is, however, more usually
confined by many to such as are metalliferous. The irre-
gular disrupting masses are called in German Stb'cke (ste-
hende or liegende Stocke), for which terms there are no
precise equivalents in English nomenclature of very
general acceptation. Where igneous rocks are accu-
mulated in great extent, and they appear to have filled
greater gaps in the earth's* crust, they are spoken of as
ranges, districts, or tracts. These are sometimes of ap-
proximately circular or elliptical shape in their horizontal
extension, as may be observed on geological maps. From
such ranges, again, there frequently run smaller branches
in different directions (ramifications).

W'here igneous rocks in a state of fusion have broken
through other rocks and spread themselves over the latter,
they are said to be overlying. They are either extended
longitudinally in one direction in the manner of streams
of lava, or they cover broad surfaces, and form extensive
fields. In both cases they may afterwards be themselves
covered by later rock formations.

The form which the igneous rocks assume above the
surface of the ground corresponds little with that of their
mass beneath, the geographical outline alone is determined
by the latter not the elevation. Very recent igneous
rocks, by reason of their volcanic origin, may be of coni-
cal shape, as is the case with many basalts, phonolites, or
trachytes ; but all the older igneous rocks owe their pre-
sent shape to the transforming influence of long continued
weathering and flooding, so that their present appearance
depends much more on their individual power of re-
sistance to those influences than upon the shape in which
they first made their appearance on the surface of the
globe.

The shape of the sedimentary and metamorphic rocks
is always flat, or nearly so. Their material was originally
deposited on surfaces more or less even, and if inequalities

108 PHYSICAL STRUCTURE OF ROCKS.

existed they were filled up, so that at least the upper
strata of such deposits are always very regularly flat
shaped, or very broadly lenticular. The general shape
and extent of these rocks corresponds therefore, more or
less, with that of every individual stratum of the same.
The conformation of the actual surface in many cases has,
however, been much changed by external forces, such as
weathering, the action of flood waters, &c. ; and, again, the
lowest beds of the series may exhibit very great inequal-
ities ; even former rents or fissures in underlying rocks
may have been filled up by the material of the deposit, so
that these fillings of clefts may subsequently assume the
shape and character of veins or dykes, in the underlying
rock. Such last mentioned cases, however, are rare.

Rents in the earth's crust have come to be filled in very
various ways, e. g. by the injection of matter in a state of
igneous fusion, by mechanical deposit from above, or by
chemical precipitate from solutions. Such fillings are
called dykes, veins, or lodes. The term lode is exclusively
applied to a metalliferous vein ; so also by some geologists
is the term vein, but this is not the universal practice.
The term dyke is exclusively applied to such as consist of
the same material throughout.

Although the sedimentary rocks, as a rule, form exten-
sive flat-lying systems of stratification, yet there occa-
sionally occur irregular accumulations distinguished from
the ordinary flat strata by proportionately greater thick-
ness and less horizontal extent, as well as by irregularity
of shape. They may have sometimes arisen by filling of
caverns.

The bedding of rocks may be divided into the regular
and irregular. The latter is characteristic of the igneous
rocks, the former of the sedimentary and metamorpnic.

Irregular bedding is in general the consequence of a
violent disruption of the pre-consolidated earth's crust.
The igneous rocks have forced themselves a path through
the existing rocks and filled up the cracks made in the
latter by the eruption. These are sometimes, but not
always, regularly formed fissures, such as when filled can
be called dykes. These violent disruptions are termed
intrusions, and when they are of unmistakable character
we may conclude with certainty that the intruding rock is

SHAPE AXD BEDDING OP ROCK MASSES. 109

of more recent formation than the one broken through,
but not how much more recent.

Regular Bedding, which, as we have said, chiefly pre-
vails in the sedimentary and metamorphic rocks, corre-
sponds with their internal stratification.

The following are some of the phases of bedding :

1. Parallel alternating bedding, or uniform bedding, when

two or more rocks alternate with each other in
parallel strata, forming a whole system of strata
whose general shape is flat or gently swelling.

2. Divergent bedding. When any set of beds incline in

different directions, they sometimes incline towards
each other (synclindt), and sometimes they fall
away from each other (anticlinal).

3. Overlapping (ubergreifend), when one set of strata

overlaps the edges of another set of strata.

4. A hollow basin-like form (Muldenformig).

5. Cloak-like bedding (Mantelformig), where the strata

or beds surround and nearly envelop a central
point from which they dip on all sides (quaqua-
versal dip).

6. Subordinate intermediate bedding, when beds of subor-

dinate size lie in the midst of a larger series of

strata.

The originally regular bedding of the sedimentary and
metamorphic rocks has very often been more or less dis-
turbed by subsequent processes, such as the intrusion of
igneous rocks, subsidence, &c., and even some of the
above-named cases are sometimes only the consequence of
some such disturbances. The natural or original position
of the sedimentary or the metamorphic rocks and their
strata is necessarily the horizontal, or nearly so. If we
find any very great variations from the horizontal, these
are, as a rule, to be considered as the consequence of dis-
turbance, although the original cause of such disturbance
may not always be recognised with certainty.

The following are some of the different kinds of dis-
turbance of bedding:

1. Uplifting, by which whole strata or systems of strata

frequently appear to have been very strongly in-
clined from the horizontal direction.

2. Contortion, foldings, bendings.

110 PHYSICAL STEUCTURE OF ROCKS.

3. Disruption, breaks (Zerknickung), where the strata

appear to have been uplifted in the centre and
broken, the two parts dipping from the place of
rupture.

4. Displacement or faults (Yerwerfung) where one por-

tion of the bed has been uplifted or depressed and
bodily separated from the remaining portion.

5. Subversion (Ueberstiirzung), where the bed has been

entirely overturned, and its position reversed.
From the bedding of rocks we may often, but not
always, determine their relative age. The principles to
guide us in this are somewhat as follows :

1. Overlying rocks as a rule are more recent than those

which they cover.

The only exceptions to this rule are created by
subversions, or by obliquely upheaved or intruded
igneous masses. Such exceptions, however, are
usually easily to be recognised by surrounding
circumstances.

2. Intruding rocks are always more recent than those

which they have penetrated.

The exceptions to this rule can be only apparent ;
as for instance, if a steep projecting rock has been
surrounded by and come to be imbedded in a later
deposit and so afterwards possibly been mistaken
for an intruder.

3. Rocks which during their formation have created

manifest disturbance of the bedding of other rocks
are necessarily in every case younger than those.

From this rule also only apparent exceptions
can arise, as when the bedding of a rock may have
been disturbed by the decay of the underlying
stratum, e. g. the dissolution of rock-salt.

4. The level of a rock alone will not enable us to pro-

nounce on its age, for the oldest sedimentary rocks
may by upheaval have been shoved up into the
highest level ; and as regards the igneous rocks,
according to their very nature the oldest and the
youngest may be met with in any level.

Ill

CHAPTER IV.

GEOLOGICAL FORMATIONS AND GROUPS OF ROCKS.

ACCORDING to the present state of our geological know-
ledge, we regard a certain class of rocks as the original
products of the consolidation of parts of the fused mass of
which our planet formerly consisted, and which we still
believe to be the substance of the interior of the globe.
These original products we term igneous rocks. All other
rocks are only secondary products arising from their
transmutation, their decomposition, decay or -disintegra-
tion, and reconstruction.

The igneous rocks are subdivided into two principal
groups, the Volcanic and the Plutonic. The volcanic are
those which, having been ejected from the interior in a
fluid or viscous state, cooled and consolidated at or near
the surface of the earth. The plutonic are those rocks
which have not reached the surface of the earth in a fluid
or viscous state, but solidified at considerable depth,
probably therefore under influences of great heat and
pressure.

The rocks which we have termed secondary products
are likewise divisible into two great classes, the Sedi-
mentary and Metamorphic. The sedimentary rocks being
formed from the debris of the igneous rocks, and the
metamorphic being the older sedimentary rocks, which, in
process of time, and from various causes, have assumed an
altered character, have undergone ' metamorphosis.' Let
us take a brief review of these principal rock forma-
tions :

1. Volcanic Formations. The active volcanoes of the
present day furnish us with the best instances of
these formations, and the surest data for consider-
ing the phenomena of their origin. First we find
consolidated lavas of various outward form and

112 GEOLOGICAL FORMATIONS

internal structure ; they assume the shape of narrow
streams down the mountain side, they overflow the
plains in broad sheets, or filling up previously
existing cracks and fissures they form veins or
dykes in other rocks, or they form conical mounds
on the mountain top. The column of lava which
solidifies in the abyss of the crater must frequently
assume the shape of a vertical cylinder, Avhich,
however, remains inaccessible to observation, unless
and until a considerable portion of the whole moun-
tain has decayed and been washed away.

The lavas consist either of basaltic or trachytic
rock ; their inferior mass is either compact, por-
phyritic, or crystalline-granular, their exterior
frequently vesicular or scoriaceous.

Thus there are many different rocks or varieties
entitled to be called lava, and all belonging to one
and .the same formation. Besides the lavas proper
we find at volcanoes various kinds of loose ejected
masses, some more and others less decomposed,
consisting of large concretions of slag, smaller
fragments of lava (lapilli), volcanic sand, and dust-
like particles, so-called ' volcanic ash.' These
ejectamenta either remain lying loose on the sur-
face of the ground, or they form conical piles K of
slag, or they are washed together by water and are
redeposited as volcanic tufa, which thus may be of
very various character.

2. The older Volcanic Formations differ from the most
recent by the entire or almost entire absence of
loose ejectamenta, scoria, evident streams of lava,
and distinct craters. No doubt all these were once
in existence, but in course of time they have de-
cayed and been washed away. We now only find
bare conical hills of basalt, dolerite, trachyte, or
phonolite (the kernels which have remained of
former volcanoes after the decay of the masses which
surrounded and covered them), accompanied by
veins branching out of those nucleous masses, and
by tufa formations or other decomposed forms of
volcanic product. So much of the outer vesicular
or scorified coating of the original volcanic rocks

AND GROUPS OF ROCKS. 113

as has not been entirely destroyed and washed
away has in the course of time been turned to
amygdaloid. These older volcanic formations, like
the more recent, are partly basaltic and partly
trachytic, and they form transition states between
the volcanic and plutonic formations.
3. Upper Plutonic Formations. These may be divided
into such as are of prevailing basic and acidic com-
position, characterised respectively by the green-
stones and quartz-porphyries. The Voigtland in
Germany presents us with a good example of
the basic greenstones, and the north-western dis-
trict of the Thuringian Forest of the acidic quartz-
porphyries.

In the Voigtland, associated with transition rocks,
we find various kinds of greenstone, such as diabase
andaphanite, granular, compact, porphyritic, fissile,
and amygdaloidal, some decayed into wacke, some
in the form of tufa, or conglomerate. These green-
stones, it would appear, constitute the subterranean
portion of a volcanic formation of the Devonian
age. We must assume that the upper and perhaps
more basaltic portion of this formation has decayed
away; loose ejectamenta and genuine volcanic
shapes are no longer observable ; the conical hills
of greenstone are doubtless the result of the supe-
rior power of resistance of that rock, just as quartz
rocks frequently protrude above masses of a softer
rock which formerly enclosed them. It is, never-
theless, remarkable that the tufa and conglomerates
which have been preserved imbedded in the tran-
sition strata appear to have been originally green-
stone and not basalt, whence we might conclude
that even the original volcanic portion of these
eruptive formations which reached the surface
rather resembled greenstone than basalt.

In the Thuringian Forest quartz-porphyries
predominate ; they are of various kinds, and are
associated with mica-porphyrites and greenstones,
claystone tufas and conglomerates. The conglo-
merates contain fragments of rocks belonging
unmistakably to the Rothliegende or Dyassic age,

114 GEOLOGICAL FORMATIONS

so that we must conclude that the eruptions which
upheaved these Thuringian porphyries took place
during that period or subsequent to it. Every
trace of genuine volcanic formation has long since
decayed and been swept away ; the plutonic part
alone has remained, except, indeed, some tufas
which have been preserved by superincumbent
strata. It need hardly be said that the process of
laying bare rocks which lay so deep must have
occupied long spaces of time, and therefore plutonic
rocks must be very old before they are exposed
and rendered accessible to our observation.
4. Lower Plutonic Formations. The most characteristic
and strongly marked representatives of these for-
mations are the granites (and syenites). These
have consolidated in the earth at great depth.
They are for the most part very distinctly crystal-
line, though their texture is very various.

They are never vesicular, nor do they occur in
the form of tufas, for the latter could not possibly be
formed in the interior of the earth. On the other
hand, they are sometimes accompanied by friction
breccias. They branch out into veins traversing
other rocks as well as the older masses of the same
formation. These branches have frequently cooled
more rapidly than the general mass and formed
themselves into porphyry. This result has been
especially observed where the veins are narrow ;
but the width of the veins has not been the only
determining cause of more rapid cooling ; the depth,
the temperature of the neighbouring rock, its state
of moisture or dryness, must all have operated in
hastening or retarding the consolidation of the in-
truding mass.

Tracts of granite frequently form the back-bone
or nucleus of mountain ranges. They occur in
larger masses and of more connected range than the
upper plutonic formations. It would appear to be the
case, as we might a priori have supposed, that upon
the occasion of every eruption of igneous fluid
from the earth's interior the opening made is wider
below than at the surface. The eruptive mass
when cooled acquires different characters according

AND GROUPS OF ROCKS. 115

to the pressure to which it has been subjected
during the cooling process ; in other words, ac-
cording to the depth at which it consolidated. The
same eruptive mass may be volcanic at the surface,
and plutonic below the surface of the earth. The
plutonic rocks, in all probability, represent the
upper portion of a conical mass, widening towards
its base. Thus we may explain the fact that the
lower plutonic rocks, when laid bare, occupy a
wider area than the upper. It also follows that as
a longer time would be requisite for their exposure,
the lower plutonic rocks which are exposed to our
observation are universally the oldest igneous for-
mations for the time being ; and thus the granites,
being those of the plutonic rocks which have con-
solidated at the greatest depths, are for the most
part the oldest of the igneous rocks of the present
geological period. This does not however exclude
the possibility of newer granite formations being
accidentally exposed in some cases, for instance, by
very violent local upheavings, or very rapid waste
of superincumbent rocks, favoured by numerous
fissures. This, in the Alps, has actually taken
place. So much of the granite formations as
reached the surface at the time of the eruption
may perhaps have been of trachytic character, and
it may be that the same masses which form the
trachyte-lavas of the present time are simulta-
neously forming granite rocks at great depths below
the surface. The fact of the chemical composition
of the two rocks being the same is at all events in
harmony with such an hypothesis.

These examples may suffice for the igneous rocks. TV r e
next proceed to notice the chief sedimentary formations.
(The metamorphic rocks being the products of the sedi-
mentary, are consequently later in date of their formation
than those.)

5. Argillaceous Formations. These are deposits of clayey
mud alternated with marl, lime, or sand, some-
times containing a large proportion of hydrated
oxide of iron. These deposits were, in process of
time, covered by more recent strata, and produced

I 2

116 GEOLOGICAL FORMATIONS

clay-slate, argillaceous shale, interstratified with
calcareous shale, compact limestone, sandstone,
and ironstone. Such formations have taken place
in all geological periods.

6. Marl Formations. These deposits consisted chiefly

of marly silt alternating with clay, calcareous mud,
sand, and sometimes gypsum or hydrated oxide of
iron. Under the pressure of superimposed strata,
these deposits became converted into marl-shale
and compact marl, interlaid with strata of argil-
laceous shale, limestone, gypsum, and ironstone.
A very characteristic marl formation of this nature
is met with in the German keuper.

7. Limestone Formations. These are the result of the de-

posit of calcareous silt, invisibly small shells, larger
shells, coral reefs (partly dolomitic) or calcareous
tufa, alternating with calcareous, argillaceous, or
sometimes siliceous strata. From these under the
pressure of superjacent formations, there have re-
sulted beds of limestone and dolomite of many dif-
ferent varieties, earthy and compact, in alternate
strata with subordinate beds of marl-shale, clay-
slate, argillaceous- shale, ironstone, or flint. In
every geological period these deposits have taken
place ; we find them very characteristically de-
veloped in Germany in the Jurassic, Muschelkalk,
and Zechstein formations.

8. Sandstone Formations. These are deposits of quartz

sand (more or less fine-grained) with some clay
marl or protoxide of iron. Pebbles also have been
deposited with the sand either locally interspersed
or in alternate beds. The deposited sand when
subjected to pressure then became sandstone, and
the other ingredients formed themselves into in-
termediate strata of slate-clay, marl-shale, conglo-
merate, and the like. These formations have taken
place in all geological periods. Very characteristic
instances are furnished by the Quader-sandstone
and variegated sandstone (Buntsandstein) of Ger-
many.

9. Conglomerate Formations. The original deposits were

chiefly pebbles, sand, and clay. From these materials

AND GROUPS OF ROCKS. 117

by pressure, solid conglomerates were formed, con-
sisting of pebbles cemented together by the sand
or clay, and inter stratified with beds of sand or
clay. These deposits have taken place in all
periods, but have never attained any great extent
at one time or place. Hence the conglomerates
play a very subordinate part in the sedimentary
formations. In Germany, there is properly speak-
ing but one very characteristic conglomerate for-
mation, which is that of the Rothliegende. The
Nagelflue of the Molasse formation is quite subor-
dinate to the sandstone, which is the predominant
rock of that formation.

10. Coal Formations. The greater part of these forma-

tions originally consisted of peat, or vegetable
materials washed together ; usually sand and clay
were likewise contained in the deposit, and some-
times hydrated oxide of iron or protocarbonate of
iron. These deposits, in the course of time, with
pressure, were formed into strata of alternate sand-
stone (usually grey) and slate-clay or shale ; and
between these strata, beds of brown or black coal
or anthracite and clay-ironstone were formed, sub-
ordinate, however, in extent and thickness to the
sandstone, slate, and shale. Coarse conglomerates,
marl, or limestones very rarely occur in these for-
mations.

The Carboniferous period and the Tertiary period
furnish the most characteristic examples of these
formations ; but the carbonaceous deposits of other
periods are associated with similar rocks, and are
so like the genuine coal formations that, petro-
graphically, they are hardly to be distinguished
from them.

11. Rock-salt Formations. Rock-salt is always accom-

panied by gypsum and anhydrite, and it likewise
usually occurs in combination with argillaceous
deposits. The rocks of this group are usually
imbedded in limestone or dolomite, as in the
Muschelkalk of Germany, or in sandstone as in
Galicia and Transylvania. In all periods these
local deposits appear to have taken place* but

118 GEOLOGICAL FORMATIONS

the special conditions and causes of their origin
are not yet known with certainty.

If we turn to the rocks which we consider 1o be of
metamorphic origin, the crystalline schists, we find alter-
nating beds analogous to those of the sedimentary rocks,
but in an altered state. We, kowever, seldom or never
find rock-salt or gypsum, a circumstance which may be
explained by the great solubility of those rocks.

The crystalline schist formations may be best described
by naming the principal rocks of each. Thus we have :

12. Argillaceous Mica-schist Formations, with subordinate

beds of quartz-schist, lydian stone, alum-schist,
granular limestone and dolomite, sometimes also
hornblende-schist, ironstone, and graphite.

13. Mica-schist Formations, with similar subordinate for-

mations to those in the argillaceous mica-schist.
In these we include some kinds of gneiss.

14. Gneiss Formations, consisting of gneiss of various

kinds in parallel and alternating strata, and con-
taining similar subordinate formations to the mica-
schists.

15. Chlorite-schist Formations, also containing similar

subordinate beds of other rocks.

These formations seem to be the result of a
special process of transmutation occasioned by the
presence of magnesia.

The fact that in the crystalline schists coal, gypsum and
anhydrite are much more rarely met with than in the sedi-
mentary formations, and rock-salt almost never, may, as
we have already said, be accounted for by the perishable
nature of those rocks. It seems remarkable that con-
glomerates are also very rarely met with. We should
not, however, forget that these only play a subordinate
part in the sedimentary formations, where they are
usually only of local occurrence. They are, moreover,
found in some crystalline schists, as, for instance, in
Valorsino and in the Upper Rhine Valley, in the west
Alpine district, where they occur in the gneiss and mica-
schist formations, and pass over by transition into those
rocks, their cementing medium having become crystalline,
and the pebbles blended with the general mass.

AND GROUPS OF ROCKS. 119

The following is a list of the great geological periods
of deposit:

POST-TERTIARY EPOCH :
Recent period (human).
Pleistocene period.

TERTIARY EPOCH :
Pleiocene period.
Meiocene period.
Eocene period.

SECONDARY or MESOZOIC EPOCH :
Cretaceous period.
Oolitic period.
Triassic period.

PRIMARY or PALEOZOIC EPOCH :
Permian period. (Dyas.)
Carboniferous period.
Devonian period.

Silurian period (upper and lower).
Cambrian period.
Pra3-cambrian periods.

120 TRANSITIONS AND TRANSMUTATIONS.

CHAPTER V.

TRANSITIONS AND TRANSMUTATIONS.

WE have hitherto treated generally of the composition
of rocks, their texture, and other outward characteristics,
and their formation or origin. It is comparatively easy
to describe these phenomena in general terms, but their
application to particular rocks in describing and classify-
ing them is a task of great difficulty. One of the prin-
cipal difficulties of classification is occasioned by the great
number of rocks of character varying more or less from
the established types. These varieties, in many cases,
form series with every shade of divergence from the
normal rock until the last member of the series presents
a totally different species, coinciding may be with some
other normal type. A series of intermediate rocks thus
connecting two established types is termed a series of
transition ; and thus, in the abstract, one type is said to
pass into the other ; not, however, that any real transition
takes place of the actual rock, but merely, as we have
said, that two groups are connected together by a chain of
rocks partaking partly of the attributes of each.

Transitions of this kind are met with in nature in
almost all kinds of rock, in respect alike of their composi-
tion, their texture, and their origin. A few instances will
suffice for explanation.

1. Transitions in respect of composition are said to take
place when in a rock of given character a strange
mineral ingredient occurs not usual in rocks of
that class, or when an essential ingredient of its
composition diminishes or altogether disappears.

For instance, in the case of limestone and dolo-
mite, a rock consisting essentially and principally
of calc-spar (carbonate of lime) is a limestone, even
though it contain some bitter spar or carbonate of

TRANSITIONS AND TRANSMUTATIONS. 121

magnesia ; but if enough of the latter enters into
its composition, then the rock will be a dolomite ;
and an endless variety of rocks are found with very
different proportions of those two ingredients, so
that it is impossible in many cases confidently to
describe them either as limestone or dolomite.
These are transition states between those two typi-
cal rocks. Again, in the case of gneiss and mica-
schist, we find first some, and then more felspar
entering into the composition of a mica-schist, until
at last we obtain a gneiss ; or we find less and less
felspar in a gneiss, until at last it is reduced to a
mica-schist. These and the like transitions may
actually be observed in nature side by side, so that
in the same mass we may sometimes find at one
end a limestone, at the other a dolomite ; at one
extremity a gneiss, at the other a mica-schist, &c. ;
but the term transition is employed in this and
other treatises in a wider sense to characterise any
rocks of intermediate composition, wherever occur-
ring, by means of which a relationship or connection
may be traced between any two species of rock.

2. The same kind of transition takes place between rocks

in respect of their outward characteristics. The
texture of rocks of every kind varies indefinitely
from one type to another, without any sharp dis-
tinction between the types; thus granite passes
over into gneiss in numberless instances where it
is more or less foliated in texture ; or granite-por-
phyry passes into porphyritic granite by means of
those rocks whose matrix partakes more of the
granular than the compact texture ; or basalt into
dolerite, by those varieties in which the individual
minerals are somewhat more separately developed
(granular) so as to be partially recognisable.

3. Transitions occur between rocks in respect of their

origin or mode of formation. Certain rocks are
only the result of a transmutation of others, and
the different stages of such transmutation have
been distinguished by separate names. Thus
argillaceous shale passes over into clay-slate and
argillaceous mica-schist ; peat into browncoal ;

122 TRANSITIONS AND TRANSMUTATIONS.

browncoal into common coal ; common coal into
anthracite ; and anthracite into graphite. Grabbro
or granite passes over into serpentine.

These last-mentioned transitions or transmu-
tations are such in the strictest sense of the word,
having been occasioned by changes of the rocks'
substance in the course of time ; whereas the term
transition, as applied to the two former classes is
only a conventional term for a progressive series
of rocks, all of which were from the first different
from each other, and remain so.

It need hardly be said that these several transitions
and transmutations multiply not a little the difficulties of
nomenclature and classification, and frequently render
the desired precision and accuracy impossible. We are
always driven back to this that every name applied to a
rock can only be considered as establishing an especially
characteristic form of its development as a kind of centre
point, which, however, in nature is surrounded by nu-
merous varieties and derivative forms of more or less
doubtful character.

123

PART II.

THE ROCKS.

INTRODUCTORY CHAPTER.

CLASSIFICATION.

A SCIENTIFIC classification of rocks is a task of more
difficulty than might at first sight appear ; as yet, no one
has succeeded in producing a perfectly consistent and
comprehensive system. Not only do the nature of the
subject and our own imperfect knowledge present many
serious obstacles to consistent arrangement ; but in many
cases established usage and nomenclature, too firmly rooted
to be lightly disturbed, prevent our changing an old classi-
fication even when based on error.

Even were our knowledge far more certain than it is,
and were we free to overthrow all previous errors and
misconceptions, we could not lay down a logically com-
plete system of classification to embrace all rocks, on any
principle, whether of ORIGIN, TEXTURE, or COMPOSITION
(chemical or miner alogical). We do not find the minera-
logical differences between rocks coincide with those of their
chemical composition, nor are either of those dependent
on geological position or stratification. There are no
rigidly defined classes in nature.

The student must not, therefore, expect too much from
any system ; but, as we are driven to choose some basis for
arrangement of our subject, we consider, on the whole,
that the best scheme for our purpose will be one in its
general features coinciding, as far as possible, with what
we know of the origin of the various rocks, making use,
however, of the distinctions arising from differences of

124 CLASSIFICATION OF ROCKS.

texture, composition, or otherwise, for the subdivision of
our subject, as the nature of each case may seem to render
advisable.

A great number of distinctions have been established by
custom between many rock formations, which in truth do
not differ from each other very materially. These we shall
as far as possible drop, endeavouring to make uniform
connected groups, and treating many rocks, which have
hitherto been known by different names, as varieties only
of one and the same rock. On the same principle, we
avoid as far as possible the introduction of new names for
rocks. It is impossible, and would be unprofitable, to
dignify every slight modification of texture or structure
(perhaps only of local occurrence) by a separate name.
Even in treating the most important and prevalent rocks,
we should seek to confine our nomenclature to their most
characteristic forms of development, establishing these as
central points of departure, from which manifold transi-
tions are found leading towards other central points in
the next group of rocks. One observer may pronounce
a doubtful rock to be granite, which another will call a
gneiss, without our being able to say that one is right and
the other wrong. In cases of this kind there constantly
arises the temptation to give new names, but in the in-
terest of science this temptation should be resisted as far
as possible.

The following are the general heads under which we
have grouped the rocks in this work.

I. IGNEOUS ROCKS* (Eruptive Rocks), all of which are
most probably products of igneous fusion.

* The term l IGNEOUS ROCKS ' is used throughout this book as the
equivalent of the German l ERTJPTIV-GESTEINE. The Germans object
to the term ' igneous/ as conveying the idea of fire or burning (which
could not take place in the absence of air), and also because the meta-
inorphic rocks may have been subjected to heat as well as those we
call igneous. Most of our rocks have, however, been named in an im-
perfect state of knowledge of their origin, and with reference to
erroneous ideas; and if we are agreed on the signification of a term,
we need not always go back to its derivation. Mr. Jukes objects to
the German term ' eruptive] as applied indiscriminately to these rocks.
He thinks that in speaking of the plutonic rocks, we should use the
terms, ' irruptive ' or ' intrusive^ &c., as they did not, or are not sup-
posed by us to have reached the surface at the time of their upheaval.

CLASSIFICATION OF KOCKS. 1-25

A. Rocks poor in silica, or basic rocks.

(a) Volcanic. Of which the BASALTS are the principal

representatives.

(b) Plutonic. Of these the principal representatives are

the so-called GREENSTONES (diabase, diorite, &c.).

B. Rocks rich in silica, or acidic rocks.

(a) Volcanic, e. g. the TRACHYTES.

(b) Plutonic, e. g. the GRANITES.

II. METAMORPHIC CRYSTALLINE SCHISTS. Most
probably the product of the transmutation of sedimentary
rocks, but in respect of their mineralogical composition
closely allied to the igneous, e. g. GNEISS, MICA-SCHIST,

CHLORITE-SCHIST, &C.

III. SEDIMENTARY ROCKS. The products of deposit.

1. Argillaceous rocks, such as CLAY and ARGILLACEOUS

SHALE.

2. Limestone rocks, such as LIMESTONE and DOLOMITE

(including gypsum and anhydrite).

3. Siliceous rocks, e.g. SANDSTONES and CONGLOME-

RATES.

4. Tufa formations.

The above are the groups of principal rocks which
occur in masses of great extent.

IV. We shall next range those rocks of less frequent
occurrence, or which only form subordinate strata or sepa-
rate beds, and whose origin is in part still doubtful, without
attempting in their case a logical classification. To this
series belong, for instance, many silicates, the CARBONA-
CEOUS ROCKS, the IRONSTONES, SERPENTINE, &C., and
some other rocks of problematical character.

V. Finally we shall instance those rocks which are
essentially composed of one mineral, such as QUARTZ,
OPAL, &c.

The first book on rocks,, at that time a most masterly
treatise, was von Leonhard's ' Charakteristik der Felsar-

We have, however, kept to the term ' eruptive ' as a general term for
describing the action of all igneous rocks ; and any other course would
have compelled us to put a construction of our own on the origin of
each rock, although not in the mind of our author, and unnecessary for
his immediate purpose. TBAUSLATOB.

126 CLASSIFICATION OF EOCKS.

ten ' (1823). In it is to be found a reprint of Alexander
Brongniart's * Classification mineralogique des roches
melangees,' which had appeared in the 34th vol. of the
Journal des Mines.

The following are the most important among the more
recent works on this subject :

Naumanri's Geognosie, vol. i., a second edition of which ap-
peared in 1858.

Senffs Classification der Felsarten, 1857, in which the rocks
are arranged with special reference to one or more charac-
teristic ingredients.

Durocher, Essai de Petrologie comparee in the Ann. des Mines,
1857 ; ii. pp. 217 and 676. He separates the igneous rocks,
in the same way that Bunsen did before him, into acidic
and basic rocks. He subdivides these again according to the
degrees of their acidity or basic composition ; these sub-
divisions nearly correspond with Bunsen's l Mittelgesteine.'

G. Bischof has examined and pronounced upon a large number
of rocks from a chemical point of view. The arrangement
of the separate treatises in his Lehrbuch der Geologie appears
to be entirely accidental, and the geological relations of the
rocks are hardly regarded.*

Rammelsberg 1 s Handworterbuch der Mineralogie (with sup-
plements) contains numerous analyses.

Roth has recently attempted to collect all the known analyses
of rocks and to arrange them according to fixed principles,
accompanying them with critical remarks.

Having referred the reader to the above-named compre-
hensive works, we shall abstain from again quoting them
in detail at the mention of each different rock. In dealing
with the particular views of their several authors we shall
only give the name of the author in question.

On the other hand, we shall have occasion to cite at the
proper places the valuable treatises of Abich, Biintsch,
Bergemann, Blum, Breithaupt, Bunsen, Delesse, Deville,
Ehrenberg, Fischer, Girard, von Hochstetter, Hochmuth,
Jentsch, Knop, List, Nauriiann, Oppermann, vom Rath,
Gr. Rose, Freiherr von Richthofen, Scheerer, Sochting,
Stache, Streng, von Walterhausen, &c.

* In the second edition (translated into English) there is much
proyement in this respect.

127

CHAPTER I.

IGNEOUS ROCKS.

WHEN we consider the position and bedding of these
rocks, and the disturbances and other changes they have
effected in the strata and beds of other rocks, we cannot
doubt that they have been forced upwards from the interior
of the earth in a fluid or semi-fluid (viscous) state. They
have penetrated and overflowed other formations and then
become solid, partly in the clefts and partly on the surface
of those rocks. The soft state in which they must have
existed during their upheaval was in all probability the
result of great heat, in other words, it was a state of
igneous fusion ; hence the term Igneous Rocks. By pro-
cess of cooling they then passed over into the solid state,
assuming (under different circumstances) a crystalline-
granular, a porphyritic, a compact or vitreous texture,
sometimes vesicular, or sometimes even a fissile texture
(schistose or slaty). Amygdaloids and wackes (as we
have already seen) were of later origin, i. e. products of
transmutation from original formations.

As regards one great division of these rocks, their
former state of fusion is capable of direct proof, and may
be observed at the present day ; we see them in process
of formation from the lava of active volcanoes. These
are termed Volcanic Rocks.

In the case of another class of those which we term
Igneous Rocks, their former state of fusion is not so
clearly evident ; indeed we occasionally find their com-
position, their bedding, or their relative position with
other formations in apparent contradiction to their assumed
origin. It is supposed that these became solid at a con-
siderable depth, some of them possibly having been poured
out in a state of fusion like lava, but in the interior of
the earth without reaching the surface, and consequently
that their consolidation took place under very high pres-

128 IGNEOUS EOCKS.

sure, and more slowly than in the case of the volcanic
rocks. They are therefore termed Plutonic rocks, and
most geologists are agreed on the nature of their origin.
The apparent contradictions to an igneous theory of their
formation are to be explained by slow cooling, and the
changes produced by time and high pressure.

All igneous rocks consist principally of compounds of
some kind of felspar (or leucite and nepheline) with
pyroxene, hornblende, mica or quartz, generally also with
some magnetic iron-ore and other subordinate minerals.

We divide the igneous rocks, whether volcanic or plu-
tonic, into those poor in silica (basic) and those rich in
silica (acidic).

The first class, the basic rocks, .are distinguished by
their deficiency of quartz ; by their felspar being gene-
rally poor in silica, and frequently richer in lime than
that of the acidic rocks, and being mixed with pyroxene
or hornblende ; by their texture being frequently vesicular
or amygdaloidal, very seldom vitreous ; and by their ge-
nerally prevailing dark colour. "^-.

The acidic rocks on the other hand are distinguished
by a felspar richer in silica ; by their frequently contain-
ing a large proportion of quartz ; by their being rarely
vesicular or amygdaloidal, but frequently vitreous ; and
in general by their lighter colour.

We might add that the basic rocks are more fre-
quently compact and porphyritic than distinctly granular ;
more frequently volcanic than plu tonic ; more frequently
found in small unconnected masses than ranging in great
tracts or regions ; whereas the acidic rocks on the contrary
are more frequently distinctly granular and porphyritic
than compact ; and more frequently extend over vast re-
gions than occur in masses of very circumscribed extent.
These data are, however, altogether general in their
character, and must be taken with many qualifications.

Bunsen was the first to draw attention to the scientific
value of the difference between the basic and acidic
rocks, which was previously little known, and had not
been carefully investigated. He devoted himself to
analysing rock-masses, and from the results of those
analyses set up two normal types of composition (see
page 364 post). We cannot, however, say that the com-

COMPOSITION OF IGNEOUS ROCKS. 129

position of the individual rocks of each of Bunsen's
groups does more than approximately correspond with
those normal values. In fact it would be more accurate
to describe the individual values as fluctuating between
two extremes than approaching any one central type.
With this explanation we present the reader with our
view of the composition of the two classes of rocks (the
basic and acidic) differing somewhat, but not very greatly,
from those of Bunsen.

The principal and most important difference between
the two groups is that of the quantity of silica, in which
respect there really seems to be a kind of leap with most
rocks. The basic rocks in general also contain somewhat
more lime and magnesia than the acidic.

Average Compositions

of the two classes

of Igneous Rocks.

Basic Rocks

Acidic Rocks

Silica

. 4555

. 6080

Alumina . ...

... 1020

816

Protoxide | ofiron

115

V . 115

Oxide J

Lime

.' 110

Magnesia .

1 6

Potash .

1 4

1 6

Soda

1 5

1 6

Water .

But the limits which we have above given are some-
times overstepped on each side, and there are igneous
rocks which we cannot with mere reference to their chemi-
cal composition reckon in either group, and which in fact
entirely fill up and annihilate the assumed gap between
the two in respect of the content of silica. These rocks
of middle character can only be classed with one group
or the other by having regard in each case to their geo-
logical character or their mineralogical affinities.

If we disregard minor differences, the varieties of
igneous rocks are not very numerous ; they may be
almost reduced to two principal mineral combinations,
the other differences consisting chiefly in texture or the
presence of accessory or single minerals.

The two principal combinations are as follows :

(1) Felspar poor in silica (in its stead sometimes nephe-
line or leucite) combined with pyroxene or hornblende,
also mica, magnetic iron-ore, and the like.

130 IGNEOUS HOCKS.

(2) Felspar rich in silica, combined with quartz, mica,
and occasionally amphibole, and the like.

In presenting this broad view, we do not mean to un-
derrate the importance of the minor differences in the
igneous rocks. All those differences are the result of
varying conditions and circumstances of their original
formation, and are therefore deserving of the greatest
attention and study.

We will return to this subject in the concluding chap-
ter, and mention some of the theories in respect to the
causes of the various development of the different igneous
rocks.

IGNEOUS ROCKS. 331

BASIC IGNEOUS ROCKS.

These are compounds of felspar (of various species)
with augite, pyroxene, hornblende, or dark coloured
mica. They frequently also contain magnetic iron-
ore, sometimes olivine. In some rocks of this class
nepheline or leucite takes the place of the felspar. In
most, there is an entire absence of quartz.

Their texture is compact, porphyritic, or crystalline ;
granular, seldom fissile, more frequently vesicular, or
amygdaloidal ; they are often found in a wackenitic state
(wacke).

According to our arrangement as previously indicated,
we divide these rocks into two classes expressive of their
origin viz. the volcanic and the plutonic.

1. Volcanic.

These rocks occur in the form of lava at actual vol-
canoes of the present day ; they are also found in districts
where the volcanoes to which they owe their birth have
been long extinct. In the latter case they often form
isolated conical mountains, or they are found as dykes
filling up the rents and fissures of older rocks.

They differ from the plutonic rocks (which have solidi-
fied deep down in the earth) by the prevalence of a
species of felspar poor in silica, such as labradorite (or in
its stead nepheline or leucite) ; moreover, by the preva-
lence of augite rather than hornblende ; and by the total
absence of quartz in their composition. Volcanic rocks
also show the traces of their former state of fusion much
more distinctly than the plutonic ; and they have evidently
cooled much more rapidly than them.

All the volcanic rocks hitherto met with are of com-
paratively recent date, and probably no ancient ones are
now existing : for the most part they have decayed away.

K 2

132 BASIC IGNEOUS KOCKS. (l) VOLCANIC.

BASALTIC KOCKS.

These rocks are mostly compounds of labradorite and
augite, with the addition of some magnetic iron-ore.
Instead of the labradorite, they sometimes contain
oligoclase, nepheline, leucite, or hauyne, and frequently
also olivine. In their fresh state they are black or
dark-grey.

These rocks have been differently named, partly ac-
cording to their somewhat varying mineralogical compo-
sition, partly in respect of their differing texture. The
most usual distinctive designations are the following :

Dolerite, consisting of labradorite and augite.

Nepheline-dolerite, consisting of nepheline and augite.

Basalt, the same compound in a compact state.

Leucite rock, consisting of leucite and augite.

Besides the above, there occur other, though less fre-
quent combinations, and varieties which have been
separately named, or which deserve special notice as
frequently recurring. In this category we may place
anamesite, tholeite, analcymite, allogovite, hauynophyry.

The basaltic rocks are all much alike in their outward
form and bedding. They occur as lava at active or re-
cently extinguished volcanoes. Sometimes they form
conical hills, which are to be regarded as the kernels of
extinct volcanoes whose outer coating has been washed, or
has decayed, away. Again, they frequently form dykes,
that is, they fill up clefts in older rocks, but in this case
they usually appear to be connected with larger masses
of a similar nature from which they have branched out.
Where they occur as actual lava we usually find vesicular
or scoriaceous varieties and tufa formations of correspond-
ing composition ; but not the vitreous state. There can be
no doubt that all these rocks are cooled products of igneous
fusion, and that the process of their formation is con-
tinued at the present day. The proof of this even in the
case of the older ones may be found in the effect which
they have often produced upon other rocks with which
they came into contact while in a state of fusion. Those
rocks frequently exhibit transmutations, for which the
simplest or only explanation is the effect of heat ; such as

BASALTIC ROCKS. 133

local vitrefaction, change of their state of oxidation ;
expulsion of their bitumen, or carbonic acid, change of
their texture, or obliteration of their jointed structure.
Sometimes also, but less frequently, the stratification of
older rocks has been disturbed to a remarkable extent by
the eruption of basaltic rocks. Again, the latter very
often contain, near their margin, fragments of the rocks
which they have broken through, and breccias have been
formed in this way.

The basaltic rocks, as purely volcanic, chiefly belong
to the most recent geological period. They are never-
theless found in many districts whose former volcanic
activity has long since ceased, and where their bedding
shows that they are older than some tertiary formations.
The original surface of these older basaltic rocks is usually
partly or entirely decomposed and washed away, and
they partake somewhat of the nature of plutonic rocks,
especially resembling certain greenstones of analogous
mineral character, and actually forming transitions into
the latter from the more genuine basaltic rocks. They
appear to have undergone many changes of state through
the influence of time and position. Their vesicular cavi-
ties have become filled with new mineral substances
(amygdaloids), internal decomposition or transmutations
have taken place, carbonates, zeolites, and other hydrous
minerals (formerly absent) have been formed, and are
now intimately blended with, and actually form part of
their composition ; or else their original fresh condition
has become wackenitic. Hence we find that no sharp
defining boundary exists between the volcanic and the
plutonic rocks. It nevertheless is not a little remarkable
that we do not know any rocks of undoubted basaltic
character older than tertiary.* The case is the same with
the trachytes and other volcanic rocks, and, generally
speaking, we find that all the older igneous formations
differ materially from the more recent, and more still from
the most recent. This fact deserves attention, and seems
to require more explanation than it has hitherto received,
since we are authorised on other grounds to conclude that

* Mr. Jukes believes the Rowley Rag basalt of the South Stafford-
shire coalfield to be of Palaeozoic age (Geol S. Staff. Coal/ield, Geol
Survey}. TRANSLATOR.

154 BASIC IGNEOUS ROCKS. (l) VOLCANIC.

volcanic agency has been at work in all periods of the
earth's history, much in the same way as at the present
time, and has always brought forth like products. What
has become of those older products corresponding to the
lavas and basalts of the present age ? Doubtless a great
part may have perished from long exposure to the de-
stroying influence of the atmosphere, or if more deeply
buried, has suffered internal change ; nevertheless it was
to have been expected that here and there (in old con-
glomerates for instance) we should have discovered some
blocks and boulders at least of genuine basalt. Strange
to say, none have yet been found, at all events none
whose character has been proved with certainty. We are
aware that in England some basaltic and phonolitic boulders
are said to have been found in Devonian strata, but these
statements seem to require further confirmation.*

1. DOLERITE and AKAMESITE. Mimesite, Ne-
pheline-Dolerite, Trap in part.

DOLERIT und AITAMESIT. Mimesit, Basaltischer Griinstein,

Griinstein, Nephelin-Dolerit. (Germ.}
DOLERITE, Haily. (Fr.}

A crystalline-granular compound of labradorite and
augite with some titaniferous magnetic iron-ore. In
nepheline-dolerite, nepheline is a substitute for the
labradorite.

Spec. grav. . . . ... 2-7 2 -9

Contains silica ..... 42 57 p. c.

The name of Dolerite was given to this rock by Hau'y.
It is rarely sufficiently coarse-grained to allow of its
individual mineral constituents being readily distin-
guished, but more usually it forms a fine-grained dark
grey to black mass, in which we are unable to distinguish

* In describing some of the igneous rocks interstratified with the
Lower Silurian rocks of Ireland, Mr. Jukes mentions the occurrence of
associated beds of conglomerate containing pebbles of vesicular trap,
derived probably from the upper surface of the old lava flows (Student's
Manual, 2nd Edit. p. 82). Some of the traps interstratified with the
Carboniferous Limestone of Co. Limerick have the vesicular and quasi-
scoriaceous parts of their upper and under surfaces preserved. A
similar fact is described by Mr. Geikie in his paper on the trap rocks
of Scotland (see Trans. JR. Soc. JEdm. vol. xxii. part 3, p. 641).
TRANSLATOR.

BASALTIC ROCKS. 135

between the labradorite and augite. This fine-grained
variety has been specially named by von Leonhard as
Anamesite.

If the compound is distinct, then the labradorite appears
in the form of white or light-grey tabular crystals, the
augite in black columnar ones. But in such case there
is usually also a compact matrix in which the more dis-
tinct particles are imbedded. This matrix is a compound
of the same ingredients viz. labradorite and augite,
usually with the addition of magnetic iron-ore, and some
carbonate of protoxide of iron and carbonate of lime, and
is so compact that its several components cannot be re-
cognised with the eye, except that the magnetic iron-ore
sometimes appears in distinct octahedrons.

The presence of the carbonates of protoxide of iron
and of lime of which we have spoken was first demon-
strated by Bergemann, as well as that of a certain silicate
of alumina and soda, whose character he could not defi-
nitely determine. He showed that almost every dolerite
contains one part capable of being decomposed by, and
another part which resists the influence of muriatic acid.
The first part consists of the carbonates, the magnetic
iron-ore, and the undetermined silicate. The latter part
consists of augite, and probably also some labradorite,
inasmuch as the different kinds of labradorite comport
themselves very variously in the presence of muriatic
acid, and there is also a, material difference according to
whether it be heated or not. Most kinds of dolerite con-
tain from 1 to 2 per cent, of water, but this Bergemann
regards as accidental, and as not having formed part of
the original composition of the rock.

Bergemann made a series of analyses to test the com-
parative character of two kinds of dolerite, the one at the
Meissner Mountain in Hessen, and the other at the
Aulgasse in Siegburg in Westphalia, with the following
result :

Meissner Aulgasse

Labradorite 47'91 . 30-06

Augite

Magnetic iron-ore
Silicate (problematical)
Carbonates

9-27

8-97

22-21

11-29

35-43
3-61
2-71

27-75

We thus find two perfectly characteristic varieties of

136 BASIC IGNEOUS KOCKS. (l) VOLCANIC.

dolerite differing very widely in their mineralogical com-
position. In other varieties, in spite of outward uniformity
of appearance, other and even greater differences, both of
mineral and chemical character, constantly occur.

Besides the above-named more or less essential in-
gredients of dolerite, it contains a considerable number of
accessory ingredients, many of which are only locally
found, or in very subordinate quantity. Such, for in-
stance, are nepheline, sodalite, melanite, mica, bronzite,
hornblende, olivine, titaniferous iron-ore, and specular
iron. In fissures and vesicular cavities there also occur
zeolites of various kinds, and distinctly crystallised sparry
carbonates.

In some varieties, the proportion of nepheline is very
considerable, supplanting the labradorite, and so forming
transitions into nepheline-dolerite. Becoming more com-
pact in other varieties, dolerite passes over into basalt,
and the different stages of compactness of texture may be
typified by the three names of Dolerite, Anamesite, Basalt.

Varieties in Texture.
(a) COMMON DOLERITE. x j n w hich the principal ingredients

G-EMEINERDOLERIT. (Germ.) \ M-nlisriTMtflirvimMo Tfloin Pm'oami

DOLEHITE LITHOIDE. (Fr.) f ar e Distinctly visioie- -iviem-.rnesen,

J near Tetschen, Bohemia.

(5) ANAMESITE. } Fine-grained, the principal ingredients

^^^on Leonhard. L on i y barely visible, Steinheim, near
ANAMESFTE. (Fr.) ' Hanau.

PORPHYRARTIGER DoLERTT. (Germ.) f onmfp ratlipr rVP

DOLERITE PORPHYROIDE. (Fr.) ) 01 au g lte > rather rare -

(d) VESICULAR or SCORIACEOUS DOLERITE. ) This texture only

BLASIGER (or SCHLACKIGER) DOLERIT. (Germ.) f occurs in the tine-
grained varieties (anamesite) ; frequent at volcanoes Stein-
heim, near Hanau.

(e) AMTGDALOIDAL DOLERITE. ) With filled-up cavities.

MANDELSTEINARTIGER DOLERIT. (Germ.) r This variety is rather more

AMYGDALOIDE. Brongniart. (Fr.) ) __

rdi t/.

(f) DOLERITE-WACZK. ) Can in general only be recognised as

DOLERIT WACKE. (Germ.) \ belonging to dolerite by tracing the
WACKE DOLERITIQUE. (Fr.) j sequence of transition states, or by
its immediate juxtaposition in nature with fresh dolerite.

Variety in Composition.

(g) NEPHELINE-DOLERITE. ] A crystalline granular compound

NEPHELIN-DOLERIT, Von Leon- I of nepheline and augite with ti-
' taniferous magnetic iron-ore.

BASALTIC ROCKS. 137

Spec. grav. . . . . 2-22-6
Contains silica .... 41 61 p. c.
This rock, formerly taken for common dolerite, was first sepa-
rately described and named by v. Leonhard. It is a dolerite in
which nepheline takes the place of labradorite. As accessories
we find it to contain thin acicular crystals of apatite, some
sanidine, olivine, and titanite. In becoming compact it passes
into nepheline-basalt, which is hardly to be distinguished from
common basalt.

Subvarieties of Texture.

(a) Porphyritic Nepheline-dolerite, the porphyritic texture being
created by crystals of nepheline. Xatzenbuckel in the Oden-
wald.

(/J) Vesicular and amygdcdoidal and wackenitic varieties occur; as
also fine-grained ones, answering to anamesite, e.g. in the
Lobauer mountains.

Perhaps much of what has hitherto been called dolerite is
more properly nepheline-dolerite. The rock is now very
distinctly recognisable, e.g. near Meiches in Hessen, at the
Lobauer Berg in Upper Lausitz and near Tichlowitz on the
Elbe in Bohemia.

Dolerite is found irregularly massive, or of columnar,
tabular, or globular jointed structure. It forms lava
streams, isolated cones, and veins in other rocks.

This rock is so frequent in all countries, especially in
volcanic districts, that particular localities need not be
further enumerated. We will only add that the doleritic
trachytes of G. Rose, which are mentioned in the fourth
volume of his ' Kosmos,' as occurring at Etna, Stromboli,
&c., appear to be dolerites rather than trachytes.

References.

v. Leonhard, Basaltgebilde. 1832, vol. i. Nepheline in Do-
lerite, 1822.

Bunsen in Poggendorf s Annalen, vol. Ixxxiii. p. 197.

Abich, Vulkanische Erscheinungen, 1841, p. 74.

liergemann in Karsten's Archiv. 1847, vol. xxi. p. 1 and 41.

/leusser in Poggend. Annalen, 1852, vol. xxxv. p. 299.

G. Hose, On Dolerite, in Neumann's Zeitsch. f. Erdkunde, 1859,
vol. vii. p. 265.

Deluxe in Ann. des Mines, 1858 [5], vol. xiii. p. 369.

Durocher in Ann. des Mines, 1841 [3], vol. xix. p. 659."

Hartung, Die Azoren, 1860, p. 97.

v. Roth in the Zeitschr. der deutsch geol. Ges. 1860, vol.
xii. p. 40.

Zirkel in the Zeitschr. der deutsch geol. Ges. 1859, vol. xi.
p. 539, on Nepheline-Dolerite.

Gumprecht in Poggend. Ann. voL xlii. p. 177.

138 BASIC IGNEOUS EOCKS. (l) VOLCANIC.

G. Rose in Karsten's Archiv. 1840, vol. xiv. p. 261.

Schitt in v. L. andBr. Jahrbuch, 1857, p. 43.

Lowe in Poggend. Annalen, 1836, vol, xxxviii. p. 158.

Girard in Poggend. Annalen, 1841, vol. liv. p. 559.

Heideprim in d. Zeitschr. d. d. geol. Ges. 1850, p. 149.

Hesse in Journ. f. prakt. Chem. 1858, vol. Ixxv. p. 216.

Mitscherlich, Basalt u. Nephelindolorit am Rhein. Zeitsch. d.

deutschen geol. Gesellsch. 1863, p. 372.
Otto Prolss, Analysen einiger Dolerite von Tava. Neues Jahrb.

f. Miner. 1864, p. 426.
v. Rath, Dolerite der Enganeen. Zeitschr. d. deutsch. geolog.

Gesellsch. 1864, p. 496.
A. Knop, Nephelindolerit von Meiches. Neues Jahrb. f.

Mineralogie, 1865, pp. 674 and 682.

Appendix.

THOLEITE. Steininger has given the name of Tholeite to a rock
found at the Schaumberg near Tholei, which he took for a
compound of albite and titanite. But according to Berge-
mann's analysis this rock consists of 70 labradorite, 5 augite,
3 magnetic iron-ore, 11 of undetermined silicate, and 9 of
carbonate of lime and protoxide of iron. It must therefore from
its composition be considered a dolerite or basalt unless indeed
it be considered as plutonic and classed with melaphyre.

ANALCTMITE. ) Bergemann in Karsten's Archiv. 1847,

CYCLOPHYRE, lle de Beau- [ vol. xxi. pp. 4, 12. Gemellaro has given

mont. (Fr.) ) the name of Analcymite to a rock found

in the Cyclades which appears originally to have been a dolerite

containing nepheline, but two-thirds of its mass now consist of

analcime, although the latter chiefly fills clefts and cavities.

We may here also mention two kinds of volcanic rock which
might collectively be called

OLIGOCLASE-DOLERITE. We refer to the AKDESITE of L. v. Buch,
and the TRACHYDOLERITE of Abich.

Both are compounds of oligoclase, augite, hornblende, mag-
netic iron and some mica, the latter generally of dark colour.
But as their silica contents often exceed 60 per cent., and as
they are frequently found in vitreous state but of trachytic ap-
pearance, we have arranged them according to universal custom
amongst the trachytes; but no doubt they stand on the
boundary between the trachytic and basaltic rocks, and may be
considered as transition states between the two.

2. BASALT. Nepheline Basalt, Trap in part

BASALT. (Germ.*)
BASALTE. (Fr.)

A compact rock, nearly or quite blacky with dull con-
choidal fracture ; an apparently homogeneous com-
pound^ of which the essentials are labradorite (or
nepheline), augite, and magnetic iron-ore, frequently

BASALTIC ROCKS. 139

united with carbonates and zeolitic substances. In
the compact mass there often occur prominently dis-
tinct grains or even crystals of olivine, labradorite,
augite, and magnetic iron-ore.

Spec. grav. . . . . ,' ' . 2'9 3-1
Contains silica . . . . . 40 5G p.c.

The mineral ingredients of basalt are too small and
intimately blended to be separately recognised with the
naked eye ; formerly it was taken to be a simple mineral
substance, but it is now shown to be only the compact
state of dolerite or nepheline-dolerite. We must, however,
observe that olivine and magnetic iron-ore is of much
more frequent occurrence in basalt than in the two last-
named rocks.

Cordier was the first who, by means of microscopic
examination, thought he recognised in basalt a similar
composition to dolerite. Hessel confirmed this view by
deduction from analysis, and many instances of the
gradual transition from basalt into dolerite also coincided.
But that basalt was in fact a compound of the above-
named minerals was afterwards established beyond doubt
by the more accurate analyses of Gmelin, Lowe, Girard,
v. Bibra, Grager, Binding, Petersen, Ebelmen, Baumann,
Rammelsberg, Schmid, and Bergemann.

Gmelin first found that a portion of the mass of basalt
was soluble in muriatic acid, and another portion not. The
insoluble part he considered must be chiefly augite and
olivine, perhaps also labradorite ; the soluble part, mag-
netic iron-ore, a sparry carbonate and zeolitic substance
(and sometimes nepheline). The proportion between the
two parts (as in the case of dolerite) is very different in
different kinds of basalt. The quantity of the soluble por-
tion fluctuates between 36 and 88 per cent. The propor-
tion of the individual mineral constituents, and also that of
the elementary ingredients, appear to be equally variable.

Like dolerite, basalt very often contains some carbonate
of iron, calcspar, and zeolitic substance (probably arisen
from decomposition, and of later date than the rock itself)
and some kinds of basalt likewise contain nepheline
instead of labradorite. Girard first discovered this com-
position in the basalt of Wickenstein in Silesia. It is
not easy from outward characteristics alone to distinguish

140 BASIC IGNEOUS ROCKS. (l) VOLCANIC.

the nepheline-basalt from the ordinary species, unless we
are assisted by finding a transition into a distinct nephe-
line-dolerite, as is the case, for instance, at the Lobauer
Berg. For this reason it is hardly practicable for the
geologist to separate nepheline-basalt from labradorite-
basalt as a distinct rock, although the difference between
them, in a purely mineralogical point of view, is of more
importance than that between dolerite and basalt, which
are only varieties of texture of the same mass.

Besides the more or less essential ingredients of basalt
(to which we therefore reckon nepheline), other minerals
also very often occur as accessories porphyritically dis-
seminated through the mass. Thus, for instance, basaltic
hornblende, oligoclase, dark brown mica, rubellan, zircon,
(hyacinth), sapphire, apatite, garnet, bronzite, micaceous
iron, titaniferous iron-ore, pyrites, &c. These minerals
may, in consequence of special local circumstances, have
either developed themselves into crystals during the
original cooling of the rocks, or (such as pyrites and
micaceous iron) they may have arisen from later processes
of transmutation. Similar internal transmutations aided
by gases or water have most probably produced the car-
bonates, zeolites, and water concealed in the compound.
The same influences have, doubtless, also produced the
minerals which have arisen in the vesicular cavities and
narrow fissures of the rock, such as hyalite, chalcedony,
zeolites, sparry carbonates, glauconite, &c.

The essential texture of basalt is compact ; if it becomes
crystalline-granular it passes into anamesite and dolerite.
But we frequently find porphyritically disseminated in
the compact base, numerous single crystals or crystalline
grains of augite, hornblende, olivine, magnetic iron-ore, and
the like, or the rock is penetrated with vesicular cavities,
and these are filled with those newer mineral formations of
which we have already spoken. There also often appears
a kind of round-grained or spotted conformation which
seems to be the result of decomposition.

Varieties in Texture.

( " } Very frequent e.g., at SchlossHerg,

(Germ.) near otolpen, Saxony.

BASALTE LTTHOIDE. (Fr.)

BASALTIC EOCKS. 141

(6) PORPHYRITIC BASALT, or BASALTIC \ .. _

PORPHYRY I Aiso f re( l uent Leschtma,

BASALTE poRpHYRotoE. (Fr.) ) Q ear Tetechen, in Bohemia.

PORPHYRAKTIQER BASALT. (Germ.) '

SCORIES BASAL-PIQUES. (Fr.) [ Icticc, Basaltic Lava, as

BLASIGER ODER SCHLACKIGER BASALT. (Germ.) J t his j s usua lly vesicular

at the surface Kammerbiihl and Wolfsberg, in Bohemia.

(d) AMYGDALOIDAL BASALT, or BASALTIC i Never of recent origin

AMYGDALOID. J Schlachenwerth, near

BASALTE AMYGDALOIDE. (Fr.) I Carlabad

MANDELSTEIXARTIGEH BASALT. (Germ.)

(e) SPOTTED AND GRANULAR BASALT \ Usually has dark grains in

(RESEMBLING DOLERITE). I lighter green mass. It is

KORXIOFLECKIGERODERDOLENTAHNLICHER [ a Stage of decomposition

J E.g. between Arnsdorf and
Steinschonau, in Bohemia, as Stoppels Kuppe, near Eisenach.

(f) BASALT- WACKE. ) (Werner's Eisenthon) a dark brown

\V.\CKK BASAI.TIQCE. (Fr.) \ OT grev, almost earthy mass, in which
BASALT- WACKE. (Germ.) ) sometimes the textures (a) (6) (c) and
(d) are distinctly repeated. Pascepole, near Teplitz.

Sometimes, but quite exceptionally, a vitreous state also occurs,
which Breithaupt has named Trachylyt, as a separate mineral
formation. It is found, e.g. near Dransfeld, in the Vogelsgeberg
and skirting basalt-veins in Iceland.

Here may be also fitly mentioned a number of varieties
of composition, some of which, if they were always dis-
tinguishable, might even be separately classed as distinct
rocks.

Varieties in Composition.

(c/) COMMON (or LABRADORITE) BASALT. ) Consisting of labradorite,
LABRADOR BASALT. (Germ.) i augite, magnetic iron-

ore, and usually also some olivine.

(A) NEPHELINE-BASALT. \ In which nepheline is substituted for la-

NEPHELIN-BASALT. I bradorite ; according to Girard, it shows

BASALTEAVEC NEPHE- ( traces of a resinous lustre, and thereby dif-

LINE. (Fr.) ) fers somewhat from ordinary basalt. But

there must be intermediate gradations or transitions between

the two which cannot be distinguished as separate varieties.

() HAUYNOPHYRY. \ Is the name given by Rammelsberg

HAUYNOPHTR, Rammel&erg. f to a rock from Vulture, near Melfi,

HAtJ^oP^RE. (fr.) f not far from Naples, which essentially

/ consists of augite and haiiyne, with

some olivine, mica, and leucite, in which also the haiiyne ap-
pears to be the substitute for the labradorite of basalt or
dolerite. The simultaneous occurrence of leucite, however,
causes it to resemble leucite rock.

The basaltic lava of Niedennendig on the Rhine contains a
considerable quantity of haiiyne distinctly prominent, but it
has been conjectured that this rock according to its conipo-

142 BASIC IGNEOUS ROCKS. (l) VOLCANIC.

sition should belong to the nepheline-basalt. On account of its
vesicular conformation it is well adapted for millstones.

(&) ALLOGOVITE. -j Is the name given by Winkler to certain

ALLOGOVIT, Winkler. \ dark grey or reddish rocks of the Allgau,
' which according to him are formed of an
intimately blended compound of labradorite with the basalts,
although their colour is somewhat different. This may, how-
ever, be the consequence of a slight difference in composition
or an incipient decomposition.

Regular jointed structure is very frequent in basalt,
usually columnar, sometimes however tabular or spherical,
with concentric layers spheroidal, or even irregularly
massive. It forms streams of lava and layers in the
basaltic tufa. It is very characteristically and variously
developed in the Bohemian Mittelgebirge ; in the
columnar form it may be seen with great regularity and
beauty at the Giant's Causeway in Ireland, at Staffa, &c. ;
but these approach dolerite in their character, and may
be more accurately described as transition states between
that rock and basalt.

References.

v. Leonhard, Basaltgebilde, 1832, vol. i.
A. Madelung, Metamorphosen von Basalt und Chrysolith.

Jahrb. der geol. Reichsanst. 1864, vol. xiv. p. 1.
Abichj Vulkanische Bildungen, 1841.

Bergemann, Analysen in Karsten's Archiv. vol. xxi. p. 88, 1847.
Surtorius v. Waltershausen, Physik. geogr. Skizze v. Island, p. 64.
Schmid, Analysen in der Zeitschrift d. d. geol. Gesellsch. vol. v.

p. 280, 1853 ; and Poggend. Annalen, vol. xcix. p. 291, 1853.
Rammelsberg in der Zeitschrift d. d. geol. Ges. p. 493, 1859 j

p. 273, 1860 ; p. 4, 1861, iiber Hauynophyr.
Schitt in v. Leonhard u. Br. Jahrb., p. 44, 1857 (Hegau), and

in G. Leonhard's Beitr. z. miner. Kenntn. von Baden, No. 3,

p. 43, 1854 (Kaiserstuhl).
Hartung, Die Azoren, j). 97, 1860.
Girard, Ueber Nephelinbasalt in Poggend. Annalen, vol. liv.

p. 562, 1841.

3. LEUCITE ROCK. Leucite- Porphyry, Leucito-
phyry, Leucilite, Sperone.

LETJCITFELS. (Germ.)
LEUCITOPHYRE, Coquand. (Fr.)

A more or less distinct compound of Icucite and augite,
with some magnetic iron-ore porphyritic or compact.

Spec, grav 2-5 2-9

Contains silica. . . . . . 45 54 p. c.

BASALTIC EOCKS. 143

Leucite rock may be regarded as a dolerite, in which
the labradorite is replaced by leucite. This difference of
composition is also usually accompanied by other differ-
ences easily to be recognised. The colour of the compact
mass or matrix of the rock is more grey or reddish-grey
than either dolerite or basalt, and, moreover, the charac-
teristic crystals of leucite are frequently to be found dis-
tinctly and prominently developed. It is a distinguishing
feature of this mineral in general, that it rarely occurs
otherwise than porphyritically imbedded, and not clus-
tered in geodes. Sometimes distinct crystals of augite
lie near the leucite in the compact matrix. As acces-
sories leucite rock also contains the following minerals :
dark magnesia-mica, sodalite, sanidine, labradorite, ne-
pheline, olivine, haiiyne, garnet, and traces of apatite.
Zeolites also very frequently occur in the clefts or vesi-
cular cavities of this rock.

Where the proportion of nepheline is greater, a transi-
tion takes place into nepheh'ne-dolerite or nepheline-
basalt.

Varieties in Texture.

(a) PORPHYRITIC LEUCITE, LEUCITOPHYRY.

LEUCITOPHYRE PORPHYROXDE. (Fr.)
(6) COMPACT LEUCITE.

LKUCTTOPHYRE LITHOKDE. (Fr.)

LEUCITOPHYRE VACUOLAIRE. (Fr.)

(d) AMYGDALOID.

AMYGDALOlDE. (Fr.)

Leucite rock forms old and recent lavas, e.g. at Monte
Somma and at Vesuvius (eruptions of 1828 and 1832); it
also occurs at volcanoes long extinct, for instance at
Roccamonfina, in the Albanian Mountains, at Bieden,
and at Bell near Andernach. Not long since, a leucite-
porphyry was discovered at Bohmisch-Wiesenthal, on the
highest ridge of the Erzgebirge, with decomposed wack-
enitic matrix, and crystals of leucite, more than an inch
in length, but for the most part changed into orthoclase
(or kalioligoclase). This last named occurrence involun-
tarily suggests the question whether the felspar of many
older rocks may not originally have been leucite, whose
form has become indistinct or entirely altered so as to be
no longer recognised. It certainly is somewhat remark-
able that hitherto no ancient leucite rock has been found.

144 BASIC IGNEOUS ROCKS. (2) PLUTONIC.

Appendix.

NOSEAN-MELANTTE ROCK is the name recently given by vom Rath
to a rock consisting of a fine-grained compound of nosean,
vitreous felspar, and melanite, with some hornblende, augite,
and titaniferous iron-ore. Zeitsch. der deutsch. geol. Ges.
p. 655, 1862.

Von Fritsch uses the common name of TEPHRITE to include leuci-
tophyry, hauynophyry, and nepheline rock. Neues Jahrb. f.
Mineral. 1865, p. 663.

DUNITE is the name given by von Hochstetter to a granular rock
which occurs in New Zealand, consisting almost exclusively of
olivine. Zeitschr. d. deut. geol. Ges. 1864, p. 341. Sand-
berger has described a similar rock as occurring in the Tring-
stein in Nassau. Neues Jahrb. f. Mineral. 1865, p. 449.

References.
ie la Soc. d.
Dufrenoy, Mem. p. s. a un descr. geol.'d. Fr. vol. iv. p. 368.

Devitte in the Bullet, de la Soc. d. Fr. [2] vol. xii. p. 612, 1856.

E. s. a un descr. geol. d. Fr. vol. iv.
xxi. p. 326, 1845.

Wedding in d. Zeitschr. d. d. geol. Ges. vol. x. p. 395, 1858.
v. Rath in d. Zeitschr. d. d. geol. Ges. vol. xii. p. 37 (Zittau),

1860. Leucitophyr von Rieden : Zeitschr. d. deutschen

geol. Gesellsch. 1864, p. 73.
Naumann in v. L. und Br. Jahrbuch, p. 61, 1860 ; p. 59,

1861 (Wiesenthal).
Rammelsberg in d. Zeitschr. d. d. geol. Ges. vol. xi. p. 493,

1859 ; vol. xiii. p. 96, 1861 (Vesuv. and Wiesenthal).

2. Plutonic.

These rocks are compounds of various felspars with
pyroxene, hornblende or mica. Besides these essential
ingredients they frequently contain some chlorite, nephe-
line and magnetic iron-ore, quartz only exceptionally ;
the greater number are free from quartz. Mineralogi-
cally as well as chemically, therefore, the composition of
these rocks is very similar to that of the basaltic rocks.
The chief differences consist in the greater frequency of
hornblende as an essential ingredient, and the frequent
occurrence of chlorite and the more rare occurrence of
quartz as accessories ; and in the development of slaty or
schistose texture in many of these plutonic rocks.

All these differences may be accounted for by the
greater depth at which these rocks probably attained the
solid state, and by their having remained a longer time
under the pressure of superincumbent masses. The same
causes may have given rise to many transmutations or

GREENSTONE GROUP. 145

new formations, such for instance as the formation of
chlorite, a characteristic (if not altogether essential) in-
gredient of the augitic greenstones, and to which they
chiefly owe their green colour, and which also usually
serves to distinguish them from the basalts.

TVe divide the plutonic basic rocks into GREENSTONES,
MELAPHYRES, PORPHYRITES, MICA-TRAPS and SYE-
NITES. Some of these, however, approach the acidic
rocks in the proportion of silica which they contain.

GREENSTONES (trap in part).

These rocks are compounds of some species of felspar
with pyroxene or hornblende as essential ingredients ;
their prevailing dark green colour they apparently
owe partly to hornblende and partly to a small admix-
ture of chlorite.

They are usually divided according to their mineral
character into three classes, under the following heads :

Diabase, consisting of felspar and hypersthene or augite
and chlorite.

Gabbro, consisting of felspar and pyroxene.

Diorite 9 consisting of felspar and hornblende.

Besides these principal divisions, there are several
subordinate varieties of composition which have distin-
guishing names, such as Calc-diabase, Eukrite, Teschi-
nite, Augite-rock, Malakolite-rock, Euphodite, Norite,
Hypers thenite, Timazite, Calc-diorite, and Anorthite-
diorite. Aphanite is the compact state of greenstone
rock in which the several ingredients are not to be distin-
guished with certainty ; and if the compact aphanitic mass
contain distinct individual grains or crystals porphyriti-
cally disseminated through it, then we employ the names
of Calc-aphanite, Labradorite-porphyry, Oligoclase-por-
phyry, Augite-porphyry, and Uralite-porphyry, for the
different varieties.

Greenstones of all kinds occur frequently in subor-
dinate masses, dykes, or stratified veins in the schists or
slates of the grey-wacke or transition period, and even
alternating with tuff-formations of the same period which
contain characteristic fossils, so that we may conclude
that many greenstones were contemporaneous with those
formations. This association with the transition-forma-

146 BASIC IGNEOUS EOCKS. (-2) PLUTONIC.

tions may be observed in the Voigtland, Fichtelgebirge,
Hartz, and the Rhine district, also in the Silurian district
of Bohemia, in Germany, and many other parts of the
world. Greenstones are likewise met with which have
broken through and penetrated much more recent forma-
tions; the timazite of Hungary and Transylvania for
instance is found to have even penetrated sandstones of
the tertiary period. But the most recent tertiary for-
mations are nowhere found to have been broken through
by genuine greenstones, although very frequently by
basaltic rocks. Greenstones are never found in the form
of genuine lava, but always more or less show their
plutonic origin, in which probably consists the whole
difference (not very considerable after all) between them
and the basalts. It is very possible that the same basic
compound which, consolidating near the surface, has pro-
duced the basaltic rocks, when it attained the solid state
at a greater depth formed the greenstones, whose pyrox-
ene and hornblende may have been partly an original
product and partly produced by subsequent transmu-
tation. The basalts and greenstones in general very much
resemble each other both in chemical composition and
mineral character. The chlorite, by which some of the
augitic greenstones are alone distinguishable from the
basalts, is most usually a product of transmutation.

4. DIABASE. Hyperite, Scandinavian Trap.

DIABAS. (Germ.}

DIABASE, Brongniart. (Fr.}

A crystalline-granular compound of oligoclase, labra-
dorite, albite, or anorthite, with pyroxene and some
chlorite in its fresh state dark green.

Spec.grav 2-72-9

Contains silica . . . . . , 43 56 p. c.

Diabase was first raised to the rank of a separate rock,
and distinguished from other greenstones, by Hausmann.

It is often very fine-grained, and in that case it be-
comes difficult to determine the , species of the felspar or
of the pyroxene, or to recognise the chlorite as such.
The felspar seems in most cases to be a white or greyish-
green, oligoclase or labradorite. The pyroxene is most ge-
nerally hypersthene, but sometimes common augite. The
green colour of the rock is chiefly owing to its chlorite,

GREENSTONE GROUP. 147

the quantity of which is however small. As accessories
the following minerals very frequently occur : magnetic
iron-ore, magnetic pyrites, pyrites, sometimes also some
chalcopyrite (copper pyrites).

As accessory accompaniments (in clefts, veins, nests and
vesicular cavities) are found quartz, actinolite, asbestus,
cat's-eye, pistacite, prehnite, axinite, calcspar, brownspar
(dolomite), talcspar (magnesite), &c.

The prevailing texture of diabase is fine-grained; it
passes over into the compact (aphanite) ; it is also some-
times porphyritic, slaty, variolitic or amygdaloidal.

Diabase bears a strong relationship to dolerite, the
most marked feature of its difference from the latter is its
chlorite and its consequent green colour. If this chlorite
be a product of transmutation, then all the original dif-
ference between diabase and dolerite probably consists in
the level or depth of solidification.

The vesicular cavities of diabase (where they occur) are
almost always filled up (amygdaloids), and this circum-
stance may be explained by the rock having long lain
in the interior of the earth under modifying hydro-
plutonic influences.

Varieties in Texture.
(a) GRANULAR DIABASE j Frequent near Berneck, Saalburg,

SSSZS!^ a 3ti [ both* in the Fichtelgebirge, &c.
(6) FINE-GRAINED (TO COMPACT) DIABASE.) Merging into aphanite,
FKiNKoijvioERBisDicHTEnDxABAs. (Germ.) > generally occurs with
DIABASE LrraoStDE. (Fr.) j (a).

PonpHYRARTiGERDiABAR.(G'erm.) I labradorite,
DZABAHK POKPHVHO^ (Fr.)

is compact, then these varieties are also sometimes designated
labrador-porphyry, augite-porphyry, or uralite-porphyry (com-
pare with aphanite, post, p. 157).

(d) SCHISTOSE DIABASE, or DIABASE- ) Indistinctly foliated, going

SCHIST. I over into aphanite-schist :

DiABAs-ScHiEFKR. (Germ.) [ occurs together with (a) and

SCHISTE DIABASIQUK. (f*r.) ) /\

(e) AMYGDALOIDAL DIABASE, or\ The vesicular cavities are filled

DIABASE AMYGDALOID. I with calcspar, chlorite, glauconite,
AM^l^iL^ 1 ^; (Germ ' ) > chalcedony and the like. Berneck

in Fichtelgebirge.

(f) VARIOLITIC DIABASE (VARIOLITE) In the principal mass round
in part). I concretions occur of a com-

VARIOI.ITISCHER DIABAS. (Germ.) [ pact or radial-fibrous or con-
(Fr.) J centric felsite (labradorite),

L 2

148 BASIC IGNEOUS KOCKS. (2) PLUTONIC.

very characteristic near Berneck, where the small felsitic glo-
bules have a violet-coloured nucleus and a white ring.
0) WACKEIQTIC DIABASE, or ) Decomposed, discoloured, earthy,
DIABASE WACKE. L an d can only be determined to be

DIABAS-WACKE. (Germ.) \ such by its juxtaposition with other
WACKE DIABASIQTJE. (Fr.) J diabase.

The following rocks are varieties of diabase in respect
of their composition, or are to be classed under the head
of diabase on account of their close approximation.

Varieties in Composition.

CALCAREOUS DIABASE. } In the fine-grained or compact matrix
KALKDIABAS. (Germ.) [ O f diabase rock are found small rounded

. )

(h) COMMON DIABASE.
(0

DIABASECALCAIKE.(/V.)

to be the fillings-up of cavities. This somewhat proble-
matical variety has been called calc-trap by Oppermann. By
others it has been called blatterstein, calc-aphanite, diabase,
and amygdaloid, and if somewhat slaty, schalstein. (Loben-
stein in the Fichtelgebirge.)

(&) EUKRITE. ) A crystalline-granular compound of anor-

ETJKRIT. (Germ.)) thite and augite, occasionally with some
olivine, hornblende, and epidote. The latter appears to have
arisen from decomposition.

This rock, according to its mineralogical composition, would
almost appear to be better classed with dolerite than diabase,
but according to Tschermark and Kraff't, its geological cha-
racter is plutonic.

It appears at Gumbelburg near Neutschin in Moravia. Some
meteorites have precisely the same composition.
(I) TESCHINITE. \ Is the name given by Hohenegger to a

TESCHINIT, Hohenegger. f rock whose mass is chiefly felsitic, and
in which hypersthene forms long black
needles ; it sometimes also contains fine needles of apatite.
This rock has broken through chalk formations and even
eocene strata in the neighbourhood of Tetschen, where it some-
times forms irregular masses, sometimes veins. According to
von Hochstetter, hornblende and augite form part of its com-
ponents, also sometimes augite and labradorite with subordi-
nate admixtures of iron pyrites, magnetic iron-ore, mica, and
chlorite. These therefore are compounds which might partly
be classed with the diorites and partly with diabase, hyper-
sthenite, or even dolerite.

More by way of appendix than as properly inclusive in
this class, we here add :

(m) AUGITE ROCK (LHERZOLITE). j A granular to compact ag-

AUGITFELS, LHERZOLITH. (Germ.) i grearate, chiefly consisting of

LHERZOLITE. (Fr.) ) l n ^ dttk^tt^ brown, or

grey ; as accessory components it contains some talc, steatite,

GREENSTONE GROUP. 149

schorl, hornblende, or calcspar. This rock can only be said to
be allied to diabase ; it forms subordinate masses at the Lake
Lherz, near Vicdessos in the Pyrenees. [According to Damour,
however, this rock of the Lherz is not thus composed, but
consists of olivine, eustatite, and diopside. See Neues Jahrb.
f. .Mineral. 1863, p. 95.]

(ti) MALAKOLITE. j Found in granular limestone near

MALAKOLTTHFELS. (Germ.) \ Rocklitz at the foot of the Rie-
PvRoxfiNrrK, ^uand. (Fr.)> sengebirge) where> according to

Herter and Porth, it forms subordinate masses, containing
copper-ore and consisting essentially of compact salite (rnala-
kolite).

The diabases and the last mentioned rocks, which are
related to them, are either found in indefinite masses or
with columnar, spherical, or irregular spheroidal jointings.

The genuine diabases are most frequently found in
the Devonian, Silurian and Cambrian formations, so for
instance in the Voigtland, Fichtelgebirge, and Hartz
mountains, where sometimes the immediately adjoining
clay -slate is transfonned into a kind of hornstone.

References.

G. Rose on Greenstones in Poggend. Annalen, 1835, vol.

xxxiv. p. 1.

Oppermann, Dissertation iiber Schalstein und Kalktrapp, 1836.
IIiiHsmann, Ueber die Bildung des Harzgebirges, p. 22.
v. Rodham u. Canaval, Kalktrapp oder Schalstein in Karn-

then in v. L. u. Br. Jahrbuch, 1855, p. 584.
Genth on Eukrite in the Annalen der Chemie u. Pharm. 1848,

vol. Ixvi. p. 17.
II(i/f(/hton on Eukrite in the Quarterly Journ. of the Geol. Soc.

1856, vol. xii.j). 197.
Tschermack u. &rafft., on Eukrite in the Berichten der Wiener

Akademie, pp. 40 and 127.
Hoheneyyer on Teschinite in Die geog. Verhaltnisse der

Nordkarpathen, 1861, p. 43.
v. Hochstetter on the same subject on the Jahrbuch d. geol.

Preichsanst, 1853, p. 319.
V. Charpentier on Augite Rock in his Essai sur la const. gtSol.

des Pyrenees, 1823, p. 245.
Marrout on Augite Rock in the Ann. des Mines, 1828 [2]

vol. iv. p. 307.
Herter u. Porth on Malakolite in the Jahrbuch der geol.

Reichsanst, 1859, p. 10.

Kjenilf (Diabase) in Christiania Silurb. 1855, p. 26.
Delesse (Diabase) in the Ann. des. Mines, 1858 [5] vol. xiii. p.

374.
Modelling. Uber Teschinit. Neues Jahrb. fur Mineral. 1865,

p. 345.

150 BASIC IGNEOUS KOCKS. (2) PLUTONIC.

5. GABBKO.

GABBRO, von Such. (Germ.}
GABBRO. (-Fr.)

These rocks are compounds of labradorite or saus-
surite, with diallage, smaragdite, or hypersthene,
and usually some other minerals. They are distin-
guished by the irregularity oj their composition and
texture.

Spec. grav. '. ' . . , . . 2-8 3-1
Contains silica ...... 43 46 p. c.

The Italian name of Gabbro, which L. v. Buch first
applied to a distinct class of rocks, has a broad and a
narrow signification ; but as even the narrower meaning
is not very definite, the name is more serviceable in its
comprehensive sense, and in which it is more generally
understood.

Naumann, using the term in its narrower sense, de-
scribed gabbro as a compound of labradorite or saussurite
with diallage and smaragdite, and he separates from it
hypersthene rock or hyperite, which essentially consists
of labradorite and hypersthene ; and there are some very
similar rocks which have received the names of norite and
euphotide.

All these in fact only form varieties of the same rock ;
they are very difficult to distinguish from each other
when they occur in a somewhat fine-grained state ; and
when they pass over into the quite compact state, as is
often the case, they all become aphanite.

Since the texture of these rocks frequently changes
very rapidly, that is within a small area, from very coarse-
grained to fine-grained, compact, or slaty, their division
into varieties of texture cannot serve any useful purpose.
We shall therefore only enumerate the varieties of com-
position, which are the following :

Varieties in Composition.

(a) GABBRO, DIALLAGE ROCK, GRANITONE. } Consists of labra-
GABBRO. (Germ.) L dorite or saussurite

DIALLAOITE, Descloizeaux. (/>.)

ragdite irregularly combined, also sometimes of all those mi-
nerals together. It is very coarse-grained, fine-grained to
compact, sometimes slaty or spotted (variolitic).

GREENSTONE GROUP. 151

The felspar if in the form of labradorite is coarse-grained to
fine-grained ; colour white, grey, or violet. If it be saussurite
it is compact and white or greenish.

The diallage occurs in white individual crystals of half
metallic lustre, grey to green. The smaragdite is grass-green,
and has a mother-of-pearl lustre. Small quantities of sparry
carbonates are often also contained in the compound frequently ;
not visible, but recognisable through effervescence with acid :
they are probably of secondary origin. The visible accessory
ingredients are mica, talc, hornblende (especially at the mar-
gins of the diallage), actinolite, garnet, iron pyrites, magnetic
iron-ore, titaniferous iron-ore, specular iron, and apatite. Many
of these also may be secondary formations. Calcspar and
quartz occur in nests or veins.

This rock passes into serpentine by transmutation (as near
Siebenlehn in Saxony) into aphanite by becoming compact,
and apparently it also even passes into diorite, diabase, granite,
and granulite.

The prevailing character of gabbro is massive. It penetrates
older rocks and formations in a massive form, or in the form of
veins forms apparent parallel strata in such. But it is also fre-
quently penetrated by veins of granite, which in that case gene-
rally contain some orthite, as near Rosswein and Bb'hrigen in
Saxony. In the Radauthal in the Hartz, where it may be easily
mistaken for diabase, it also contains wollastonite, schillerspar,
and rutile, and in fissures also desmine, prehnite, and albite,
near La Prese in Upper Italy. It consists, according to Breit-
haupt, principally of hornblende with metallic pearly lustre
(schillerspar), and a felspar of the highest spec. grav. with
some brown mica. If the felspars have become much wasted
from weathering, then the pyroxenic ingredients often appear
above the surface in strong relief.
(6) EUPHOTIDE. | The euphotide of French geologists is

Kri-Honrr. (Germ.) according to Delesse, essentially a com-
BupH<mHB,ir*. </*..)) bination 6 of felspar and diallage with
titaniferous and chromic magnetic iron-ore, iron pyrites, ser-
pentine and carbonates. The felspar is Saussure's jade, which
afterwards Beudant called saussurite. It approaches in cha-
racter labradorite, also vosgite and anorthite. The diallage
often occurs as the variety smaragdite, which, according to
Haidinger, properly consists of a combination of hornblende
and pyroxene. The talc forms small laminae, scarcely percep-
tible, the serpentine minute veins. The carbonates consist of
invisible particles of calcspar, dolomite, and iron. As acces-
sories there also occur hornblende, mica, and garnet, especially
characteristic in the Alps and in Corsica.

NOWT, Scheerer. \ compound of hypersthene or diallage, labra-
' dorite, orthoclase (containing soda), and even
some quartz.

The felspathic ingredient of this rock is sometimes so pro-
minent that the whole mass almost appears to be nothing but

152 BASIC IGNEOUS ROCKS. (2) PLUTONIC.

a granular felspar rock. It occurs on the island Hitteroe,
Norway.

(d) HYPERSTHEISTITE, HYPERITE. "j Consists of a coarse-grained to
HYPERSTHENIT, HYPERSTHENSYENIT, >. compact compound of labrado-
(FrT } J. rite ^ d hypersthene.

Labradorite is the prevailing ingredient, coarse to fine-
grained, grey, greenish or bluish. The hypersthene appears
dark-brown, to green on its cleavage surfaces, has a metallic
pearly lustre, its outer edges sometimes coated with horn-
blende. The labradorite is the most strongly affected by
weathering, and it decays away, leaving the hypersthene to
protrude. The following minerals occur as accessories in this
rock : Titaniferous iron-ore, garnet, hornblende, olivine, brown
mica, needles of apatite, iron pyrites, and magnetic iron-ore.
It usually is of a massive structure, and forms veins or irregular
masses between other rocks. It occurs characteristically in
Hollenmiihle, near Penig in Saxony, Neurode in Silesia/ Isle
of Skye, Elfdalen in Sweden.

The monzon-hypersthenite of v. Richthofen differs slightly
from the ordinary kind. It consists of a very distinctly crys-
talline granular compound of dark-green to black hypersthene
with greenish-white labradorite. The hypersthene is usually
the principal ingredient ; sometimes, however, the labradorite
is entirely predominant, and in that case distinct crystals of
common black augite occur in the mass.

The hypersthenic varieties also sometimes contain the like
in small quantities, also dark -brown mica-plates and crystals
of titaniferous iron-ore are found. At Monzoni in Southern
Tyrol, this rock has broken through genuine syenite (free from
quartz) and formed veins in it.

References.

v. Such in the Magaz. d. Gesellsch.-naturforsch. Freunde zu
Berlin, 1810, vol. iv. p. 128.

v. Rath in Pogg. Annal. 1855, vol. xcv. p. 535 (Silesia).

Delesse, Bullet, de la Soc. geol. de France, 1849 [2] vol. vi.
p. 410, 435, 547, and Ann. des Mines, 1849 [4] vol. xvi. p. 323.

Scheerer in the Gaea Norwegica, vol. ii. p. 313.

v. Richthofen, Geogn. Besch. von Siid-Tyrol, 1860, p. 146.

Keibel, Zeitschr. d. d. geol. Ges. 1857, vol. ix. p. 573.

Koch, Jahrb. d. Ver. f. Naturk. in Nassau, 1858, vol. xiii. p. 123.

Kjerulf, Christianias Silurbildungen, 1855, p. 23.

Streny, Zeitschr. d. d. geol. Ges. 1858, vol. x. p. 174; Neues
Jahrbuch fiir Mineralogie, 1862, pp. 513 and 932, 1864, p. 257.

Drysdale, London and Edinb. Phil. Journ. 1833, vol. xv. p. 386.

EMmen, Ann. des Mines, 1847 [4] vol. xii. p. 629.

Jenzsch has analysed the hypersthenite of Neurode in Silesia,
which contains bright shining spots and distinct particles of
chlorophoeite in dark brown-green matrix, and pronounces
both from chemical and microscopic analyses that the
matrix consists of about 27 oligoclase and 25 augite, and of
39 vitreous felspar, 5 magnetic iron-ore, 2 chlorophoeite and

GREENSTONE GROUP. 153

2 apatite. He found the content of silica very high, viz.
66-5. Poggend. Ann. 1855, vol. xcv. p. 418, and v. L. u.
Br. Jahrb. 1857, p. 436.

Websky, Gabbro von Neurode. Zeitschr. der deutschen geol.
Gesellsch. 1864, p. 530.

6. DIORITE.

DIORIT. (Germ.)
DIORITE, Haiiy. (JFV.)

A crystalline-granular compound of felspar and horn-
blende. The felspar is not orthoclase. In fresh state
it is usually dark green.

Spec, grav . 2'6 2-9

Contains Silica ...... 47 58 p. c.

Diorite was first so named by Haiiy. Its texture is
often so fine-grained that it is difficult to determine the
species either of its felspar or hornblende, although the
minute particles of the former in most cases shew the
fine parallel striae which are characteristic of albite,
oligoclase, anorthite, or labradorite, and which forbid the
idea of orthoclase. Gustav Rose in his first work on
greenstones held the felspar of diorite to be albite. Sub-
sequently he embraced the view that albite never occurs
at all in crystalline rocks. Although this latter opinion
is shared by few, yet all observers now agree that the
felspar in diorite which was formerly taken for albite is
usually oligoclase. Delesse again has recognised labra-
dorite and anorthite as essential ingredients in many
kinds of diorite. Thus the difference in the species
of the felspar constitutes one class of varieties of the
rock. The hornblende is also various : generally it is the
ordinary hornblende ; sometimes, however, a variety more
approaching to actinolite, and Breithaupt lately disco-
vered an entirely new species of hornblende as an essential
ingredient in many greenstones of Servia, Transylvania,
and Hungary. It has a black colour and greenish-grey
streaks. He named it gamsigradite after the name of the
place where he first found it.

But inasmuch as it is not easy, and in the fine-grained
state of the rock impossible with certainty, to recognise
the different species of felspar and hornblende, it does not
appear to us desirable on their account to dignify these
different varieties of diorite with the character of indi-

154 BASIC IGNEOUS EOCKS. (2) PLUTONIC.

vidual rocks, although it is well to distinguish them where
possible, since they are somewhat mineralogically dif-
ferent. The gamsigradite variety has been named by
Breithaupt timacite, from one place where it occurs.
This timacite has also a geological importance, as it is
found to have broken through the older tertiary strata of
Hungary and Transylvania, whereas the greater number
of diorites are much more ancient.

All these mineralogical differences are very trifling in
a chemical point of view ; so that we may well consider
them but as the result of somewhat unequal cooling of
the same original mass. We do not mean that they
should therefore be disregarded, on the contrary we
consider that it would be an inquiry of the greatest
geological interest to endeavour to trace their causes.
Such an inquiry, to be successful, however, would demand
a comparison of many special and accurate observations of
the rock taken from various localities.

The following minerals sometimes occur in diorite as
accessories ; mica (brown and black) pyrites, magnetic
pyrites, magnetic iron-ore, titaniferous iron-ore, titanite,
garnet-pistacite, and quartz. Some of these may be of
secondary origin, e.g. the pyrites and the pistacite, which
latter appears to have proceeded from the hornblende, and
sometimes contributes to the green colour of the rock.

The fine-grained varieties of syenite may be easily
mistaken for diorite, the only essential difference between
the two being that orthoclase is a necessary ingredient of
syenite. The following characteristics may assist in dis-
tinguishing the two rocks, although not always to be re-
cognised in them, nor universally to be relied on. Diorite
is more frequently fine-grained than syenite, and gene-
rally (owing to its hornblende) more green in colour. In
diorite the felspar decomposes sooner than the horn-
blende, and therefore on weathered surfaces the latter
often protrudes prominently, whereas syenite weathers
more evenly and falls into a kind of sandy grit. Diorite
usually contains more pyrites than syenite, and the latter
more frequently contains titanite or wohlerite than the
former. Their variations of texture and their outward
structure, as well as their place in nature, are usually
somewhat different, as will appear from the short ac-

GREENSTONE GROUP. 155

count which we shall give of each under their respective
heads.

As varieties of texture without regarding varieties of
composition, the following kinds of diorite may be distin-
guished :

Varieties in Texture.

(a) GRANULAR DIORITE. \ The most normal variety, e.g. at the
KORXIGER DIORTT. (Germ.) \ Klumpsen mountain, near Ebers-

DIORITEGRAMTOIDE. (Fr.) )

(6) FINE-GRAINED DIORITE. \ Passing into compact (aphanite)
FEIXKORXIGER BIS DICHTBR ! Belmsdorf, near Bischofswerda, in

DIORTT. (Germ.) [ nV^loneU*

DIOKITK UTHOIDE. (Fr.) ) Oberlausitz.

PORPHYRY. I amphibole, going over into

PORPHYRARTIGER DlORTT. (Germ.) nnhamtif nnmhvrv

DIORITE PORPHTROIDE. (Fr.) ) a lc P or P n y r y-

(d) SLATY DIORITE, or DIORITE-SLATE. j The slaty texture usually

DIORIT-SCHIEFER. (Germ.) [ imperfect, passing into

DIORITE SCHISTOSE. (Fr.) } apfanite slate.

(e) ORBICULAR DIORITE, or ] The globular conformation is only

NAPOLEONITE. ! a local appearance in diorite. It

(Germ.) f occurs very characteristically and
1111 ' BrOH9 ~) Beautifully near Sautina and Ajac-
cio, in Corsica. The rock consists,
according to Delesse, of a combination of anorthite, blackish-
green hornblende, and some quartz, so that it is a distinct
variety in respect of its composition no less than its texture.
The constituent minerals form alternating concentric layers
round kernels. The kernels themselves consist (almost exclu-
sively) either of the anorthite or hornblende (not of both), and
they likewise exhibit a radiated texture. Thus we find balls
of from one to three inches in diameter, whose section shews
rings of alternate light and dark colour.

At Schemnitz (Stephen-shaft) orbicular timazite occurs, but
the spherical masses are not in concentric layers.
(/) AMYGDALOIDAL DIORITE. ) Only occurs rarely, and with

MAXDELSTEIXARTIGERDIORIT. (Germ.)) a fine-grained to compact
matrix, which passes into the state of aphanite.
, O) WACKENITIC DIORITE, or\ This decomposed discoloured, and
DIORITE-WACKE. L somewhat earthy state can only be

SSSSStfSfU.) I rg^h certainty as belong-
ing to dionte by tracing its transi-

tion from distinct rocks. The foregoing differences of texture
are however repeated in it.

Varieties in Composition.

(A) COMMON DIORITE essentially consisting of oligoclase and horn-
blende, the diorite of the Huhnberge, in the Thuringian Forest,
is somewhat differently composed, inasmuch as its felspar con-
tains lithia, and very many small needles of apatite occur
disseminated through the whole mass. This rock, which is

156 BASIC IGNEOUS BOCKS. (2) PLUTOXIC.

sometimes very coarse-grained, has broken through the rothlie-

gende and becomes quite compact near the surfaces of contact.

() AsroRTHiTE-DiORiTE. i In. which the oligoclase is partly or

AXORTHIT-DIORIT. (Germ.) f wholly replaced by anorthite. As for

instance in the orbicular diorite of Corsica, which likewise

contains some quartz.
(k) TIMAZITE (TRACHTTIC GREENSTONE). } Consists, according to

TIMAZIT, Breithaupt. (Germ.) ] Breithaupt, of a grey

or greenish-grey felsitic base, in which are imbedded crystals
of white felspar (albite or mikrokline), black hornblende (gam-
sigradite), some mica, magnetic iron-ore, and iron pyrites. The
base, which is tine-grained to compact, corresponds most closely
with labradorite.

The cleavage-prism of gamsigradite shews an angle of
124 26', its hardness is 7, and spec. grav. is 3 1' ; it has a
greenish-grey streak. The mica forms hexagonal brown plates.
The magnetic iron-ore forms very small grains or crystals,
the iron pyrites very small cubes.

According to an analysis by Dr. Rube the tirnazite of Gam-
sigrad, in Servia, contains about 50 per cent, of silica. We
have already stated that this rock is frequently met with in
Transylvania and Hungary, especially in the mining districts,
and that it has penetrated through the Eocene sandstones. We
have elsewhere described a rock occurring in Borsabanya, in
the Marmaros, in the north of Hungary, which we named
labradorite -rock, because its prevailing base consists of labra-
dorite. According to Breithaupt this is essentially the same
as timazite j but we find from Dr. Rube's analysis that it con-
tains above 63 per cent, of silica, and therefore it belongs to
the acidic rocks. As, according to Delesse, the diorite of Pont
Jean, in the Vosges Mountains, also contains labradorite, it is
very possible that it is a timazite.

(T) CALCAREOUS DIORITE. ) ls the name g iven b 7 Senftto a dark-
KALK-DIORIT, Senft. (Germ.) \ green, more or less distinct compound
HEMITHRENE. (Fr.) ) O f hornblende, oligoclase and mica,

penetrated with calcspar, and which near Ruhla, in the Thurin-

gian Forest, forms a stratum in mica-schist.

The jointed structure of the diorites is usually irre-
gular ; but sometimes columnar or globular.

Diorite frequently occurs in subordinate masses, veins,
or dykes in the schistose or slaty rocks of the Silurian or
Devonian age, and (exceptionally) sometimes in much
newer formations ; sometimes also in granite, gneiss, or
mica-schist.

Appendix.

The NORITE of Esmark (different from that of Scheerer) very
widely spread in Norway, appears only to be a variety of
diorite containing quartz and mica.

The OPHITE of Palassou is, according to its description, a tolerably

GREENSTONE GROUP. 157

compact diorite. The MiCA-DiORiTE of Delesse on the other
hand ought rather to be classed with Syenite than here, on
account of its containing orthoclase.

References.

G. Rose on Greenstones in Poggend. Annal. 1835, vol. xxxiv.

p. 1.
Keibel, Analysen in d. Zeitschr. d. d. geol. Ges. 1857, vol. ix.

p. 575, and v. Leonhard u. Br. Jahrhuch, 1859, p. 445.
Riviere, Bullet, de la Soc. ge"ol. d. Fr. 1844, vol. i. p. 528.
Hunt in Sillim. Amer. Journ. 1859 [2] xxvii. p. 340.
v. Richthofen, Geogn. Beschreibung v. Siid-Tyrol, 1816, p. 111.

The diorite at Klausen contains actinolitic hornblende with

oligoclase.
Delesse on Orbicular diorite, which was first described in 1785

bv Besson, in the Journ. d. Phys., and on the Diorite of the

v osges, Ann. des Mines, 1859, vol. xvi. pp. 160 and 339 :

1851, p. 149.
Brctihaupt on Timazite, in the Berg- u. Hiittenm. Zeitg. 1861,

p. 51. On the Diffusion of Timazite.

Compare Cotta's Gangstudien, vol. iv. pp. 28, 56, 65, and 85.
Senft on Calc-diorite. In the Zeitschr. d. d. geol. Ges. 1858,

p. 308.
Esmark on Norite in the Magaz. for Naturvidenskabern, vol. i.

p. 207.

Charpenticr on Ophite, Constit. g6ol. des Pyrenees, 1823, p. 481.
Dufrenoy on Ophite, Ann. des Mines, 1832 [3] vol. ii. p. 21.
v. Rath. The diorite of Neurode, in Silesia, consists of 56

parts of hornblende, and 44 saussurite. The former has been

formed from augite according to G. Rose, Pogg. Ann. 1855,

vol. xcv. p. 655.
Herm. Vogclgesang, as to globular diorite, Berggeist, 1862,

Nos. 90 and 91.

7. APHAKITE. Trap in part, Melaphyre in part.
APHANIT. (Germ.}
APHANITE, Hauy. (Fr.)

A compact, apparently homogeneous mass ; usually dark
green to black ; of about the hardness of felspar ;
very tough ; sometimes porphyritic by reason of crys-
tals of felspar, hornblende, or pyroxene ; also vesicular
or amygdaloidal.

Spec, grav 2-62-9

Contains silica .... 43 58 p. c.

The separate ingredients of the principal mass of this
rock are not to be recognised with the naked eye, hence
the name of aphanite, given by Haiiy. Wehave already
shown that transitions take place into aphanite from
diabase, gabbro, or diorite ; proving it to be but a com-

158 BASIC IGNEOUS ROCKS. (-2) PLUTONIC.

pact state of one or other of those rocks, bearing the same
relation to them as basalt to dolerite; a view which is
entirely confirmed by chemical analysis.

The minuteness and intimate union of the individual
constituent ingredients of aphanite when quite compact,
no less than their general resemblance to each other,
make it impossible with the ordinary aids to discover
from the appearance of the rock whether it belongs to
diabase, gabbro, or diorite. We can only draw conclu-
sions in this respect from finding it in conjunction with
one or other of those rocks. If, however, the aphanite
be porphyritic, then the minerals porphyritically enclosed
in the compact matrix may give a clue to the composition
of the latter ; for instance, we frequently find labradorite,
oligoclase, pyroxene, or hornblende thus porphyritically im-
bedded in aphanite. It is dangerous, however, to rely too
implicitly on conclusions so drawn, and on every account,
therefore, in describing the varieties of aphanite we refrain
from the attempt to keep up distinctions corresponding
to the three normal rocks of diabase, gabbro, and diorite.

Possibly by careful microscopic observations we might
succeed in determining the special mineral character of
every aphanite. But such observations are attended with
considerable labour, and the appliances are not always
within reach; on a journey they would be out of the
question. We may, however, state that the microscopic
observations which have been made of aphanite entirely
confirm what we have already said respecting its nature,
and show that even the accessory ingredients of the three
normal rocks are represented in its composition. The
greater number of aphanites appear to belong to the
pyroxenic greenstones, or we might rather say that these
latter have more frequently assumed the compact state
than the hornblendic varieties. Many varieties of texture
and composition which are found in the three granular
rocks are likewise repeated in the compact rock.

Varieties in Texture,
(a) COMMON COMPACT APHANITE.

GEMEINER DICHTER DIORIT. (Germ.)

APHANITE LITHOIDE. (Fr.) -VTT-.LT- j. i /i i i ,. T

(6) PORPHYRITIC APHANITE or With crystals of labradorite, oli-

APHANITE-PORPHYRY. I goclase, hornblende, augite, or

PORPHYRARTIGER DIORIT. (Germ.) uralite. Accordingly we dis-

APHANITE PORPHYROIDE. (Fr.) ) tinguish labradorite - porphyry,

GREENSTONE GROUP. 159

oligoclase-porphyry, augite-porphyry, or uralite-porphyry, of
which we will treat more at large hereafter.

Near Manebach, Herges, and Tabarz, in the Thuringian
Forest, there occur aphanitic porphyries whose felspar crystals
are not yet accurately determined.

(C> Sl s ATT T ^ PHANITEOrApHiNIIE -) Usually only indistinctly
AnumttMm. (Otrm.) \ slaty, or of thick cleavage.

APHANITE scrasrolDE. (Fr.)

(d) VESICULAR APHANITE. ) Rather rare ; sometimes it would

BLASIGER APHAXTT. (Germ.) \ appear that the vesicular cavities
APHANITE VACUOLAIRE. (Fr.) ) have been once filled, and their
contents weathered out. We often find them empty at the
weathered surface, but still remaining filled in the fresh in-
terior of the rock.

(e) AMYGDALOIDAL APHANITE. -\ The vesicular cavities are most

APHANIT-MANDELOTEIN. (Germ.) [ usually filled with calcspar or
APHANITE AMYGDAixtfDE. (Fr.) ) zeo litic substance.
(/) WACKENITIC APHANITE, orj Discoloured and earthy through
APHANITE-WACKE. ( decomposition, its petrographic

APHANIT-WACKE. (Germ.) character only to be determined
WACKEAPHANITIQUE. (Fr.) ) byitssurrou / dings .

As varieties of composition the following species may
be distinguished in addition to the usual quite compact
form : x

Varieties in Composition.

(</) CALCAREOUS APHANITE. ) In the compact and slaty mass are

KALKAPHANIT, SCHALSTEIN f f oun d n^ing o f calcspar or brown

] spar which are not fillings up of

vesicular cavities.

(A) VARIOLITIC APHANITE, VARIOLITE. ) The compact base con-

YAIMOI.ITHISCHKH APHANIT,VARIOLTTH. (Germ.) I tains concretions of
VARIOLJTHE, JADEGLANDULEUX, Brongniart. lie \

de Beaumont. (Fr.) > greenish or violet grey-

ish colour, either of stringy, radiated, or concentric texture from
the size of a grain of mustard-seed to that of a walnut, firmly
grown in, and not very sharply defined. They consist of a
felsite (probably labradorite), but frequently also contain some
pistacite in concentric layers. As accessories in the matrix of
the rock we find iron pyrites and magnetic iron-ore, in its clefts
and cavities quartz, pistacite, calcspar, and chlorite.

Delesse has narrowly investigated and described the vario-
lites of the Durance, and he also mentions those of the Fichtel-
gebirge, and of Savoy, &c. (Ann. des Mines, 1850, vol. xvii. p.
11(3.) Their spherical concretions often exhibit a reddish, violet,
or grey kernel, round that a lighter coloured rind, and round the
latter a green shell of a somewhat lighter colour than the
enclosing matrix of the rock. In the latter, with the aid of
the microscope, he also discovered small laminae of felspar.
(*) LABRADORITE-PORPHYRY(BLACK PORPHYRY).) The black matrix
LABRADORPORPHYR. (Germ.) [incloses crystals

MELAl'HYHE fKLD.Sl'ATHiyUE. (Fr.) 1 / i r j S j

oi laDraciorite and

160 BASIC IGNEOUS EOCKS. (2) PLUTONIC.

small particles of a dark green mineral not yet determined ; spec.
grav. 2-7, content of silica 56-58 p. c. By aid of the magnifying
glass Streng found the apparently compact matrix to be dis-
tinctly crystalline, consisting of one mineral of dark-green in-
clining to black, and another of a lighter green colour. Probably
they are the same as the minerals which also occur in a distinct
form. The crystals of labradorite often shew a dark dull-green
kernel, surrounded by a light and shining margin. The striae
of twin crystallisation are continued equally through both.
Sometimes the reverse is the case, the kernel is light and
shining, and the margin dull and of a darker colour. As acces-
sories, but rarely, and only in small particles, brownish-black,
mica plates, pyrites, and magnetic iron-ore. Near Elbingerode
at the Hartz, this rock penetrates Devonian slates and lime-
stones.

To this class belong the rocks described by Delesse, found
by him at Belfaly and Ternuay, in the Vosges ; these contain
augite, and are amygdaloidal in part. Also the rock described by
Kjerulf as melaphyre from Barnekjern, near Christiania, as well
as many other so-called melaphyres and porfido-verde-antico.

Streng in v. L. u. Br. Jahrb. 1860, p. 397.

Delesse in Ann. des Mines, 1847 [4] vol. xii. p. 228.

Kjerulf, Christiania Silurbecken, 1855, p. 28.

(&) OLIGOCLASE-PORPHYRY. \ Is the name given by G. Eose to a
OLIGOKLASPORPHYK. (Germ.) J diabasic or aphanitic rock in the Ural
Mountains, which has a dark green compact or nearly compact
matrix containing crystals of oligoclase. Much porfido-verde-
antico is of this character ; also the rock described by Delesse,
as found by him at Lescines, in Belgium, containing some
pyrites, and some copper pyrites (unless it belongs to mica-
diorite) and several rocks from the neighbourhood of Christiania
described by Kjerulf.

G. Rose, Keise nach dem Ural, vol. ii. p. 571.
Delesse. Bulletin de la Soc. geol. d. Fr. 1849 [2] vol. vi. p.
386 ; 1850 [2] vol. vii. p. 310.

) Christiania Silurbecken, 1855, p. 9.

ATJGITE-PORPHYRY. | (Often called Melaphyre,) A com-

AUGITPORPHYR. (Germ.) \ p ac t matrix, usually dark green,

MELAPHYRE PYROXENIQUE. (Fr.) ) Containin c ' rsta ls of auite!

Fr. v. Richthofen reckons to this division the most of the
rocks of the Fassa region, which are usually designated as
melaphyres.

These contain crystals of augite and labradorite (or sometimes
oligoclase), inclosed in a matrix resembling basalt. Titaniferous
iron-ore is also disseminated through the mass in small par-
ticles. They are very variously developed ; most frequently we
find them vesicular and amygdaloidal.

V. Richthofen, Southern Tyrol, 1860, p. 128.

(jri) URALITE-PORPHYRY. \ Is the name given by G. Rose to
URALITPORPHYR,^. Rose. (Germ.) \ rO ck containing crystals of uralite
PORPHYRE 1 OURALITE. (Fr.) ) ^ ft CQmpact dark; pro bably diabasic

GREENSTONE GROUP. 161

matrix. This uralite has the form of augite, and the substance
of hornblende.

G. Rose, Reise nach dem Ural, vol. ii. p. 370.

The four last-named varieties may be indifferently
termed aphanitic porphyries, or greenstone-porphyries ;
and they are sometimes classed together under the name
of melaphyres. The timazites of Hungary likewise fre-
quently have a compact aphanitic base, for instance, those
in the neighbourhood of Schemnitz, in which single crys-
tals or crystalline particles of hornblende (gamsigradite)
or felspar may be clearly distinguished.

Aphanite is usually of jointed structure, or very dis-
tinctly cleft.; generally the blocks are irregularly massive,
sometimes, however, regularly columnar, or regularly or
irregularly spherical. The aphanites occur in nature under
the same circumstances as diabase, diorite, and gabbro ;
and very often in their company. We have already sug-
gested that they should be regarded as mere modifications
of those rocks, differing from them chiefly in the greater
rapidity of their original cooling process. The Saxon
Oberlausitz affords striking instances in illustration of this
opinion. The granite region there is found to have been
broken through by diorite, and accordingly numerous
dome-shaped hills of the latter rock protrude from the
surface ; near to these the same eruptive mass has pro-
duced narrower dykes (from 5 to 20 ft. thick), whose
texture is fine-grained, nearly compact. Near Belmsdorf,
not far from Bischofswerde, we observed a diorite dyke
20 to 30 ft. thick, which in the centre was fine-grained,
but almost compact towards the walls of the cleft, where
it must have cooled more quickly. The offshoots from the
same vein into the granite, and the narrow parts of the
principal vein of only two inches thick, consist of a com-
pletely compact mass, which might easily be taken for
basalt, as it is almost quite black. These differences of
texture are there manifestly the consequence of different
degrees of rapidity of cooling caused by the different
volume or thickness of the mass.

On this subject see Erlauter. z. geog. Karte von Sachsen, 1839.

No. 3, p. 24. Also on the subject of aphanitc,
Dclesse in Ann. des Mines, vol. xvi. p. 350.

162 BASIC IGNEOUS ROCKS. (2) PLUTONIC.

8. MELAPHYRE. Augite-Porphyry in part, Trap in

part.

MELAPHYB. (Germ.')
MELAPHYHE, Brongniart. (Fr.)

The rocks which we include under this name are dark-
coloured, greenish, brownish, or black ; compact, por-
phyritic, vesicular, or amygdaloidal ; always free from
quartz. They are compounds (intimately blended) of
felsite, pyroxene, hornblende, and magnetic iron-ore.

Spec. grav. 2'6 3-1

Contains silica ..... 54 62 p. c.

The name melaphyre has ceased to bear a distinct
character, having been successively used by different
geologists, ever since the time of Brongniart, who first
introduced it, for many and various igneous rocks having
nothing in common with each other, unless it be a pre-
valent compact texture, dark colour, and absence of
quartz. Hence the name conveys no definite idea, unless
qualified by the name of a particular author, and that is
not always sufficient without the name of the locality.

There are many and various rocks of uniform dark
colour, of a prevailing compact or amygdaloidal texture,
close compounds of some kind of felspar with pyroxene,
hornblende, and magnetic iron. We have already
spoken of several such under the heads of basalt and
aphanite. Much of what has been called melaphyre cer-
tainly belongs to our basalts and greenstones. The rocks
of which we shall treat under the name of porphyrite
have often been called melaphyre, and if we take away
all that may be ascribed to basalt, greenstone, and por-
phyrite, little will be left to which to apply the name of
melaphyre.

Under these circumstances the name can only be use-
fully retained as a sort of provisional term for any basic
igneous rocks of prevalent compact texture and dark
colour, whose composition is not so definitely marked as
to entitle them to be included under any other more
distinct species ; much in the same way as we are often
compelled to use the general name of greenstone for
rocks whose mineral character is not sufficiently decided,
or has not been sufficiently investigated, to enable us to
class them as diorite, gabbro, or diabase.

MELAPHYRE. 163

In dealing thus, for our own part, with the name of
melaphyre, we here subjoin a quasi-historical account of
the mode in which it has been used by different authors.
\Ve think the divergence of their readings will be a
sufficient justification, if any be needed, for the way in
which we propose that the term should in future be
accepted.

(a) Al. Branrjniart, the inventor of the name melaphyre, described it

as l Pate noire d'aniphibole pe"trosiliceux enveloppant des
cristaux de feldspath ; ' what is here meant by 'amphibole pe"tro-
siliceux ' is very uncertain, the more so as at that time (1813)
the differences Between hornblende and pyroxene were not so
well established or known as they are at present.

(b) L. von Bttch lirst applied Brongniart's name of melaphyre to

certain black-coloured rocks of the Fassa Thai and the Seisser
Alp (see ante, p. 162). He, however, also called these rocks
black porphyries or augitic porphyries, because they contained
crystals of augite, and their matrix was also black and rich in
augite. He also included under the same designation many
rocks of the Hartz and Thuringian Forest, &c., whose compo-
sition he presumed to be similar, and which he considered to be
the original cause of the upheaval of those mountains. To
them he also ascribed the formation of dolomite in several
localities. As the principal characteristics of this rock, he
enumerated dark colour, great content of augite, and complete
absence of quartz. See von Leonhard's Taschenbuch, 1824,
vol. ii. pp. 289, 372, 437, and 471.

niart has introduced under the somewhat singular name of
melaphyre are for the most part identical with those which
Faujas de Saint Fond collected under the Swedish name of
trap, and of which Warmholz, Steiniger and others have
made use in the same sense. Werner called them trap-por-
phyries or trap-amygdaloids ; Zobel and v. Carnal, porphy-
rite. Freiesleben called them pseudo-porphyries ; v. Raumer,
basaltite ; and in many French writings they ara also in part
called spilite. Trap and melaphyre are probably the most usual
names at the present day ; for although the Swedish trap, ac-
cording to Erdrnann is a diabasic rock, whereas the rocks
which bear the same name in the Faroe Islands and Iceland
are basaltic formations, it nevertheless appears to be most useful
to retain (with L. von Buch) the name of melaphyre for the
rocks which we are about to treat.' These are tnen described
as compounds of labradorite, and (probably) augite in small or
invisible crystals (therefore compact), but alone recognisable,
and frequently in the form of scattered crystals, the rock very
much inclinecl to the amygdaloidal in 'texture. They are
further described as always containing magnetic iron-ore, car-
bonate of protoxide of iron, and carbonate of lime, in invisible
particles, as well ns some rubellan and mica. Their petro-

H 2

164 BASIC IGNEOUS ROCKS. (2) PLUTONIC.

graphic difference from the basalts, according to Naumann, is
confined to the want of olivine, and to the circumstance that
the augite is not to be recognised with certainty. Geognosie,
and in v. L. u. Br. Jahrb. 1860, p. 1.

(0) Von Richthofen attempted to put an end to the confusion
which the name of melaphyre had gradually introduced by
restoring the definition of Brongniart, and he believed that he
had discovered the identical rock in various places ; for instance,
at Schneidemiillersberg near Ilmenau, in the Schleusenthal, in
the Thuringian Forest, between Landshut and Glatz in Silesia,
near Oberstein, and between Botzen and Colmann in the Tyrol.
He describes the rock thus :

Compact matrix, dark-green or brown to black. Fracture
uneven, inclining to conchoidal ; lustre shining ; hardness that
of felspar or less; spec. grav. 2*7; contains crystals of felspar
(oligoclase or labradorite), other minerals only exceptionally to
be recognised. In his large work on the Tyrol he also reckons
the rock of which the summit of the Margola is formed to this
compound of oligoclase and hornblende, with much oligoclase,
labradorite, augite, and hornblende, and partly of a fine-grained
species ; it consists partly of an intimate compound of oligoclase,
and few crystals of augite. This latter variety was termed by
v. Klipstein mulatt-porphyr.

From the results of the chemical and microscopic analyses
of these rocks, from the minerals which they contain in a dis-
tinctly crystalline form, and from their specific gravity, von
Richthofen framed conclusions respecting the mineralogical
composition of the compact matrix, and pronounced it to con-
sist essentially of oligoclase and hornblende, with subordinate
quantities of apatite, titaniferous iron, sometimes also some
magnetic iron-ore, and chlorophseite, or magnesia-mica. In it
often labradorite crystals lie imbedded exceptionally, perhaps,
also similar ones of augite, hornblende, epidote, or mica, but
never quartz or olivine.

In vesicular cavities there occur quartz and chalcedony, car-
bonic spars and zeolites. (Vide Zeitschr. d. d. geol. Ges. 1856,
pp. 589 and 593, which gives a very complete catalogue of the
literature on this subject; Sitzungsb. d. Wiener .Akad. d.
Wissensch. 1857, vol. xxvii. p. 293 ; Remarks upon the dis-
tinctions between melaphyre and augite-porphyrj^, Vienna,
1839, and Geogn. Beschreibung v. Siid-Tyrol, I860. p. 141.)
(e) E. Sochtinff, on the other hand, attempts to show that Richt-
hofen's definition of the matrix is unfounded ; that accord-
ing to the results of the analyses, it might just as well consist
of labradorite and augite, and that Brongniart was not to be
depended upon as to the determination of hornblende (Zeitschr.
d. d. geol. Ges. 1857, p. 427). Sb'chting himself had formerly
described the so-called melaphyres of the Thuringian Forest as
an intimate compound of labradorite and augite in the Zeitschr.
d. ges. Naturwissenschaften, 1854, p. 197.

(/) Girard starts with the principle that the geological character of
rocks is the principal thing to be determined, and that they

MELAPHYRE. 165

should always be classed and named accordingly, rather than
according to their mineralogical or chemical composition. He
combats von Richthofen's view in respect of melaphyre, but
seems somewhat to have misunderstood his meaning. For
Richthofen merely sought to avoid the uncertainty into which
the term melaphyre had fallen by keeping as strictly as possible
to Brongniavt s first definition, and thereby excluding many
rocks which had been called melaphyres. Girard, on the other
hand, seeks to show that many of these excluded rocks really
contain augite and no hornblende, a fact not disputed by
Richthofen, but one which according to him did not entitle
them to be called melaphyres. We may, perhaps, think von
Richthofen's narrowing of the sense of melaphyre impractical
or inconsistent : unpractical because, being too much opposed
to prevailing ideas, it is little likely to be adopted ; inconsistent
if taken in connection with the enlargement of the meaning of
the term trachyte which he himself advocated. Nevertheless
it does not follow that it is in itself inaccurate, even if we
choose to acknowledge Girard's premised principle to be the
ri^ht one. Girard himself considers the melaphyre of Ilfeld
to be a compound of a mineral containing felspar with augite,
the augite forming only one-fifth or one-sixth of the entire
mass. Whether the prevailing ingredient be labradorite or
oligoclase, he leaves undetermined. Small black grains in the
same mass, he takes for magnetic or titaniferous iron. He
compares also some other .melaphyre with that of Ilfeld.
(v. L. u. Br. Jahrb. 1858, p. 173.)

(g) Streny distinguishes three kinds of rock in the neighbourhood of
Ilfeld by the names of melaphyre, porphyry-melaphyre, and
melaphyre-amygdaloid. The first, which should belong to our
porphyrite, is a grey or brown-coloured rock with matrix re-
sembling hornstone, and containing small crystals of felspar
not longer than the tenth part of an inch, white or greenish
with twin strise (labradorite or oligoclase) associated some-
times with crystals of an undetermined dark-green mineral
grown into the felspar crystals ; the matrix likewise contains
small reddish-brown garnet grains, also a light-green mineral,
perhaps only the product of decomposition and very small par-
ticles of magnetic iron-ore.

In the melaphyre of Streng the principal mass is of dull ap-
pearance, a'nd in its fresh state is blue-black, distinctly crystal-
line, of wavy lustre and friable by weathering it becomes
greenish-grey or brown. It is probably a compound of felsite
and augite or hornblende, or a yet undefined mineral of the
nature of diallage and some magnetic iron-ore. In the matrix
occur very small crystals of the same diallage-like mineral, also
hirircr columns of the same mineral which exhibit a growth of
t win crystals, crossing each other regularly at an angle of 60,
and distinct small plates of rubellan. In a second essay Streng
described the diallage-like mineral as a schillerspar which con-
tains alumina.

The melaphyre-amygdaloid of Streng consists of a homo-

1G6 BASIC IGNEOUS ROCKS. (2) PLUTONIC.

geneous brown matrix, of the hardness of 5-6, and contains
small amygdaloidal cavities filled with glauconite, chalcedony,
and carbonate of lime.

The specific gravity of these varieties fluctuates between 2 '6
and 2-7. Their content of silica, taking the mean of a consider-
able number of analyses, is for the melaphyre-porphyry 61'3, for
the melaphyre and melaphyre-amygdaloid 54'4. They form
together a plateau of considerable size between the lower and
upper Rothliegende districts (Zeitschr. d. d. geol. Ges. 1858,
p. 99, and 1859, p. 78). Upon the position and bedding of these
rocks see Bantsch in Abhandl. d. naturf. Ges. zu Halle, 1858.
(h} G. Hose defined the Ilfeld melaphyre as follows : a fine-grained
almost compact mass of black or brown colour, sometimes con-
taining small acicular crystals, or greenish-white crystals,
(likewise small). The texture is often vesicular or amygda-
loidal. According to the known analyses, both microscopic and
chemical, the matrix most probably consists of an intimately
blended crystalline compound of oligoclase, with augite or
hornblende, magnetic iron-ore, and some apatite; the fine
acicular crystals appear to be augite transformed into schil-
lerspar; the greenish white crystals Rose could not determine.
In local varieties also small crystals of mica occur and irregu-
larly shaped grains of some other mineral.

The vesicular cavities, often very regularly shaped (for in-
stance pearshaped), contain concentric layers of chalcedony and
quartz as well as calcspar.

The following are varieties more especially distinguished by
Rose.

Black melaphyre, from the Raben Klippen, at the Hartz. A
compact compound in which transparent prismatic crystals are
prevalent ; between them lie larger white crystals, very small
grains of magnetic iron-ore.

Black melaphyre from Wieprersdorff. Matrix under the mi-
croscope less distinct than the last-named ; in it lie diallage-like
crystals of augite.

Red melaphyre from Wiegersdorff. Matrix under the mi-
croscope less distinct than the last-named; in it lie diallage-
like crystals of augite.

Red melaphyre from the Birkenhoff. The matrix reddish-
brown, and containing green acicular crystals of augite.

Ro^e considers these melaphyres to resemble chiefly those of
Lowenberg, Lahn, and Landshut in Silesia. (Zeitschr. d. d.
geol. Gesellsch. 1859, p. 280.)

(f) THE OBERSTEIN AMYGDALOID. This rock, celebrated for its
beautiful agates, is considered by many geologists to belong to
the melaphyres ; thus (e. g.) : von Dechen, Dufrenoy, Elie de
Beaumont, and Naumann. Its principal mass, usually brown or
greenish, no doubt consists chiefly of felsite, and often contains
small crystals of felspar, and amygdaloidal cavities filled with
agate and other minerals ; accordingly we should term the rock
a porphyrite. Delesse was the first to give a careful analysis
of it. Its spec. grav. is 2-68. Chemically it contains 51-13

MELAPHYRE. 167

silica, 29-73 alumina and peroxide of iron, 473 of lime, 4073
magnesia and alkali, 3*68 water and carbonic acid. From these
data, as well as its mineralogical characteristics, Delesse con-
cludes that the principa. mass essentially consists of labra-
dorite ; in fact, there frequently occur in it a great number of
small labradorite crystals, white and translucent : its frequent
green colour appears to be owing to an admixture of chlorite.
Sometimes some aueite is observable, also small flakes of
brown mica. Magnetic iron-ore in very finely divided particles
appears to be uniformly dispersed through the whole mass.

In the numerous amygdaloidal cavities, whose diameters
vary from one-tenth of an inch to a foot, Delesse found agate,
opal, quartz, chlorite, calcspar, different kinds of zeolite, hy-
drated oxides of iron and manganese.

The amygdaloid of Oberstein possesses compact fine-grained
and porphyritic varieties, and occurs in the coal formation of
that district, sometimes forming dykes and masses of consider-
able size, sometimes parallel seams. It appears to have been
t lirust up about the time when the deposit of the rothliegende
began. Perhaps its character is the same as that of the rock,
previously described under the name of tholeite. (See ante,
p. 138.)

(Delesse in Ann. des Mines, [4] vol. xvi. p. 511 ; Steininger,
Geogn. Beschreib. d. Landes. zu Saar. u. Rhein, 1840, p. 110.)
(k) Senft designates as melaphyres almost all dark quartzless igneous
rocks of the Thuringian Forest ; according to him, they consist
principally of a compact mass of labradorite, combined with
in;i<rnetic titaniferous iron-ore, calcspar, ironspar, and iron-
chlorite (delessite). He distinguishes several varieties, viz. :
in the first place, those resembling greenstones from those
resembling basalt or felsite-porphyry, then according to their
texture; (1) granular like dolerite, near Schmiedelfeld ; (2)
porphyritic (melaporphyry), which he subdivides into labra-
dorite- and melaphyre- (trap-porphyry), mica-porphyry and
iron-chlorite (delessite) porphyry ; (3) nielaphyre-amygdaloids,
and (4) compact or fine-grained melaphyres. "Surely these are
rocks of very various character.

(Bericht der Naturforscherversammlung zu Wien, 1858,
p. 144.)

As regards the so-called spilites of the Western Alps, which
ore also considered to belong to the melaphyre, compare

Gueymard, in the Ann. des Mines, 1850, [4] vol. xviii. p. 54,
with

Delesse, ibid. 1857, [5] vol. xii. p. 457.

E. E. Schnrid on Melaphyre of Mombachler Hofen, between
Baumholde and Grumbach in Rheinpfalz, in Pogg. Ann. 1863,
vol. cxix. p. 138.

Modeling, Melaphyre des Riesengebirges, Neues Jahrb. f.
Miner. 18G5, p. 344.

168 BASIC IGNEOUS ROCKS. (2) PLUTONIC.

PORPHYRITES.

As the rocks which come under this head are all inti-
mately connected with each other by transition states,
and they likewise all assume the same geological position,
we shall characterise them as the varieties only of one
species, describing them, nevertheless, individually.

9. PORPHYRITE. Felspar-Porphyry, Quartzless
Porphyries, Mica-Porphyry or Hornblende-Porphyry.

PORPHYRIT, G. Rose. {Germ.}
POKPHYRITE. {Fr.}

Contains in a felsitic matrix (usually of dark colour)
individual crystals of felspar, mica, or hornblende.
The matrix is sometimes also vesicular or amygda-
loidal.

Spec. grav. i - .... 2-627
Contains silica 59 61 p. c.

The term porphyry, without addition or qualification,
denotes, par excellence, quartz-porphyry, a rock with

Suartz-felsitic base and crystals of felspar and quartz
see p. 214 post, where it is more particularly de-
scribed). Naumann, therefore, proposed ^n his treatise
on Ilfeld) to collect all the quartzless porphyries with
prevailing felsitic base under the common name of POR-
PHYRITE, which had already been applied to some of
them. This nomenclature has now been pretty generally
accepted. It appears to us certainly better than Rose's
proposal to designate a part of these quartzless rocks
syenitic porphyry (see also post, p. 210, where Rose's
divisions are further explained). Many varieties of por-
phyrite stand on the very margin between the basic and
acidic rocks (their silica ranging from 49 to 61 per cent.),
but the greater part are basic. Quartz only occurs very
exceptionally in their composition.

These rocks, by reason of their prevailing dark colour
and their deficiency in quartz, were formerly frequently
classed as melaphyres. We have already expressed
the opinion that most of the so-called melaphyres are
either basalts, greenstones, or porphyrites, so that there
is scarcely anything left to which to apply the name of
melaphyre distinctively. But as it is often very difficult

PORPHYRITE GROUP. 1G9

to determine whether a rock is properly a basalt, a green-
stone, or a porphyrite, the name of melaphyre for such
doubtful rocks may prove convenient and useful. It might
have been more correct to give up the name of porphyrite
and use that of melaphyre in its stead, both because the
name of porphyrite refers to a texture which is not an es-
sential feature of these rocks, and because the porphyrites
are not always in fact porphyritic. Such an innovation,
which Senft seems really to have intended, was, however,
open to the serious objection that the name of melaphyre
had already been so much abused as to make it hopeless to
attempt now to clothe it with a definite meaning, although
it may perhaps be usefully retained for rocks of indefinite
character.

The porphyrites may be divided into distinguishable
varieties, according to their different composition. They
may be best classed according to the distinct minerals
which occur in them porphyritically. Thus we shall dis-
tinguish Porphyrite (proper), with crystals of felspar ;
Hornblende-porphyrite, with crystals of felspar and horn-
blende ; and Mica-porphyrite, wdth crystals of felspar and
mica.

The porphyrites are usually severed by joints into irre-
gular masses, or very deeply cleft by fissures ; they are
more rarely jointed in columnar or tabular form.

In Germany they are not met with of much more re-
cent origin than the Rothliegende ; this formation is, how-
ever, sometimes found pierced by them, and the two are
very often contemporaneous. In Southern Tyrol, much
more recent porphyrites would appear to occur.

The porphyrites never occupy connected fields of great
extent, and in general they are far less widely spread than
the quartz-porphyries.

(A) PORPHYRITE (FELSPAR-PORPHYRY).

PORPHYRIT. {Germ.)
PORPHYRITE. (Fr.)

A felsitic principal mass, usually dark-brovm, containing cry stain
of felspar, oliyoclase, or sometimes orthoclase, and occasionally
other minerals.

Spec, grav ' . . 2-6 27

Content of silica at Ilfeld on the average "| A1 Q

(therefore very high). . . J

170 BASIC IGNEOUS EOCKS. (2) PLUTONIC.

The colour of the matrix varies sometimes into grey, red,
violet, or blue, and besides the crystals of felspar, it contains as
accessory ingredients an admixture of garnet, titanite, mag-
netic iron-ore, specular iron, and pyrites, &c. This porphyrite
is extensively developed in the South of Norway, where
L. von Buch has in part named it ' Rhombenporphyr,' on
account of the rhombic section of its felspar crystals. At
Elfdalen, in Sweden, it is manufactured into small ornaments.
It is also very prevalent in the Lenne-Gebiet in Westphalia,
and on the southern border of the Hartz Mountains. As the
rock of the last-named locality has been recently very ac-
curately described, we subjoin a short abstract of those de-
scriptions.

Porphyrite (Streng's melaphyre-porphyry, p. 165), found at
Ilfeld, near the Hartz Mountains, contains in a dark-brown or
grey felsitic matrix, cry stals of felspar, also a dark-green mineral,
a light-green mineral, red garnet, and small scales of mica-
ceous iron. The matrix, according to Streng, consists chiefly
of orthoclase, which Rose, however, doubts.

Rose made a microscopic analysis of this rock. The thin
polished plates showed a transparent matrix marked with black
spots and streaks, and filled with black grains of irregular
shape. According to Streng, the felspar crystals as well as the
grains consist of labradorite. Baentsch and Girard hold the
dark-green mineral for augite ; Rose, on the other hand, con-
siders it to be a product of decomposition of hornblende. Ac-
cording to Streng, black and shining grains of titaniferous iron-
ore may be recognised in the weathered state of the rock. At
Ilfeld no vesicular or amygdaloidal varieties of this rock appear
to occur, unless we regard those amygdaloids as such which
have been described as melaphyre a view which Streng and
Naumann disapprove.

This rock is often of columnar jointed structure; it forms an
extensive plateau in the region of the Rothliegende, where it
also probably ramifies downwards in the form of veins.

Many other porphyrites bear a close resemblance to the
Ilfeld rock ; for instance : the porphyrite of Korgon in the
Altai Mountains, which contains greyish-white laminae of
oligoclase and specular-iron in a reddish-brown matrix ; the
porphyry of Hainersreuth in the Fichtelgebirge, which has
reddish-white crystals of oligoclase, and very little specular
iron in a reddish-brown matrix ; the porphyrite of the Pentland
Hills, near Edinburgh, with crystals of oligoclase, and specular-
iron sparkling in a brownish-red matrix ; the porphyrite of
Ziegenriicken, near Hohenelbe, with crystals of oligoclase, is
a dark-coloured matrix, and the porphyrite of Rovigo, near
Lugano, also with oligoclase crystals in a dark matrix. The
amygdaloids of Oberstein, which we have previously described
on Delesse's authority, probably also may belong to this class.

Von Richthofen describes certain porphyritic rocks of Mu-
latto and Cavalessi, in Southern Tyrol, which contain tabular
crystals of felspar in a compact, and for the most part reddish

PORPIIYRITE GROUP. 171

matrix, or which sometimes consist of a fine-grained mass
without crystals; others contain liebenerite in the forms of
nepheline or orthoclase (pseudomorphous) ; these last-named
rocks form narrow veins, penetrating all the other rocks of that
district.

Varieties in Texture.

( a } PORFHYRITIC.

(b) COMPACT.

(') AMYGDALOIDAL PORPHYRITE or AMYGDALOID.
(d) PORPHYRITE-WACKE. I Somewhat decomposed. AtMa-

ARGILOPHYRE, Brongniart. (Fr.) J rienberg in Saxony, these veins
of wacke" in the gneiss rock are called ' Kalchgange.'

References.

Strenrj, Zeitschr. d. d. geol. Ges. 1858, p. 106; 1861. p. 87.

G. Rose, ibid. 1859, p. 296.

Naumann in v. L. u. Br. Jahrb. 1860, p. 24.

Girard, ibid. 1858, p. 145.

JSaentsch, Die Melaphyre des Harzes, 1 858.

Von RiMofenj Geogn. Beschr. v. Sud-Tyrol, 1860, p. 149.

Kjemlf, Christiania Silurbecken, 1855, p. 29. The rhomben-
porphyr of the Vetta Collen (Kjerulf s melaphyr) contains
large crystals of labradorite in a felsitic matrix, which ac-
cording to him also contains augite.

(B) HORNBLENDE-PORPHYRITE.

HORNBLENDEPORFHYRIT. (Germ.)

PORPHYRE SYENITIQTJE. (Fr.)

In a compact felsitic matrix , usually of dark colour, are con-
tahtt'il cn/xfals or crystalline particles of hornblende and felspar
(oligoclaae).

Spec, grav 2-6 2-7

Contains silica (at Potschappel, near Dresden) 59 p. c.

The matrix of this rock usually much preponderates over
the porphyritic crystalline parts, and is in its fresh state usually
brown, violet-brown, or grey ; becomes lighter in weathering.

The hornblende forms small columnar or acicular crystals,
which become very distinct when the matrix is somewhat
weathered or discoloured. The crystals or grains of felspar
(oligoclase ?) are often very intimately blended with the matrix,
and their species is therefore difficult to determine. At Wils-
(IrutK, in Saxony, and in some other localities, some dark-
coloured mica occurs, together with the hornblende, forming
transitions into mica-porphyrite. The rock contains no quartz.
The matrix is sometimes vesicular or amygdaloidal. Didey
describes a blue porphyry (probably belonging to this class),
and occurring at Chaux, near Trejus, where it passes through
the Variegated Sandstone. He states that it contains crystals
of hornblende and albite.

172 BASIC IGNEOUS KOCKS. (2) PLUTONIC.

This rock is not known to be very extensively developed
anywhere. In the Plauenschen-Grund, near Dresden, it occurs
in the neighbourhood of syenite ,- it may possibly represent a
more compact state of that rock. It is older in that place than
the coal formation, and even the lower strata of that formation
contain fragments of it; its jointings show smooth surfaces.
The masses are irregular, approaching somewhat to the colum-
nar form.

To this rock belong many antique porphyries, particularly
the porfido-rosso-antico, which contains white felspar and black
acicular crystals of hornblende, and usually some micaceous
iron in a red matrix.

A rock occurring at the Hutberg, near Weisig, to the east
of Dresden (called by Jenzsch ' amygdalophyre '), seems to
belong here, as it contains some hornblende ; in any case it
belongs to the porphyrite group. It is often amygdaloidal,
and contains in its vesicular cavities hornstone, chloraphseite,
chalcedony, quartz, pyrites, and sometimes felspar, resembling
petalite, which Jenzsch has called weissigite.

Varieties of Texture.

(a) PORPHYRITIC.

(b) COMPACT.

(d) WACKENITIC.

References.

Delesse on the antique red porphyries, Bullet, geol. 1850,
p. 532 ; also, in v. L. u. Br. Jahrbuch, 1851, p. 422.

Jenzsch in v. L. u. Br. Jahrb. 1853, p. 386, and in 1854, p. 400.

Naumann, Erlauter. zur geogn. Karte v. Sachsen, 1845, No. 5,
p. 202,

Diday, Ann. des Mines, e*d. 2, p. 193, von L. u. Br. Jahrb. 1855,
p. 784.

(C.) . MlCA-PORPHYRITE Or MlCACEOTJS PORPHYRY.

GLIMMERPORPHYRIT. (Germ.}

PORPHYRE MlCACE. (Fr.)

A compact felsitic matrix, usually of dark colour, containing
crystals or crystalline particles of mica and felspar.

Spec. grav. ..... 2-62-8

Contains silica at Meissen . , . 59 p. c.

The felsitic matrix when fresh is of a brown or violet-brown
colour, but is lighter when weathered. It incloses distinct
laminae of mica of dark colour, and often of hexagonal form ;
also grains or crystals of felspar, sometimes frequently, some-
times sparingly disseminated.

The felspar appears to be partly oligoclase, partly orthoclase ;
it is white, greenish, or reddish j sometimes only in thin

MICA-TRAP ROCKS. 173

laminae. Occasionally hornblende or quartz occurs, developed
in distinct crystals ; and thus a transition arises into horn-
blende-porphyrite, or granite-porphyry.

Vesicular and amygdaloidal textures sometimes occur, in
which case there are usually fewer crystals porphyritically
imbedded. The amygdaloidal cavities contain green-earth,
calcspar, and siliceous minerals.

Mica-porphyrite abounds in the Thuringian Forest, where it
is usually of irregular massive structure, with perhaps a ten-
dency to columnar jointing. When it occurs with quartz-por-
phyry in that locality, it is older than it, and older too than
the Rothliegende, the conglomerates of which formation contain
many fragments of mica-porphyrite. Near Meissen a very cha-
racteristic mica-porphyrite is found penetrating the syenite-
granite, as well as the granite dykes contained in that rock.
The veins of the porphyrite are usually compact without
crystals towards their outward edges, or throughout the vein,
where the ramifications are narrow. At Zwickau, in Saxony,
amygdaloidal varieties occur in conjunction with the compact.

Varieties in Texture.

(a) PORPHYRITIC.

(b) COMPACT.

(d) WACK&

Vide Cotta in v. L. u. Br. Jahrbuch, 1845 ; p. 75.

MICA-TRAP ROCKS.

The name mica-trap originated with Naumann, who
first proposed it for certain rocks of the Erzgebirge, being
compounds of mica and felspar, but himself afterwards
(in his ( Geognosie ') preferred the French name of mi-
nette for the same rocks, which no doubt is their older
designation. Under these circumstances, it may be ad-
missible to transfer the name of mica-trap to an entire
group of similar rocks, whose common attributes are :
that they consist principally of compounds of mica and
felspar, without marked porphyritic texture ; and that they
contain no quartz, unless quite exceptionally.

We count in this group the following rocks (although
it is uncertain if they are all of igneous origin), viz.
Minette, Faidronite, Kersanton, and Kersantite. Until
that question is determined in the negative, they may be
so classed on account of their petrographic affinity ; and
for the same reason they will be most conveniently treated
as varieties of the same rock.

174 BASIC IGNEOUS EOCKS. (2) PLUTONIC.

10. MICA-TRAP.

GLIMMERTRAPP. (Germ.)
TRAPP MICACE. (Fr.)

A compound of felspar and mica.

Spec, pav 2-5 2-9

Contains silica .... 50 65 p. c.

Varieties.

(A) MINETTE.

MDTETIE. (Germ.)
MUSETTE. (Fr.)

Afelsitic matrix containing much mica and sometimes distinct
crystals of orthoclase or hornblende ; grey colour predominates.

Spec, grav 2-5 2-9

Contains silica ... 60 65 p. c.

The blackish-brown magnesian mica sometimes predominates
so completely as to be alone distinctly visible. As accessories,
there occur hornblende, and sometimes chlorite and magnetic
iron-ore. Calcspar and sparry iron are probably only of
secondary origin, and quartz is probably never present. It is
sometimes difficult to distinguish minette from mica-porphyry
or from kersantite.

It is found in considerable extent near Framont, in the Vosges
Mountains, where it first received its name from the miners, a
name which Voltz first introduced into science. Near Oederan,
in Saxony, it forms subordinate masses in the Red Gneiss, and
not far from Dippoldiswalde, in Saxony, it penetrates the grey
gneiss of the Weissritzthal in distinct veins.

References.

Voltz, Geognosie de 1' Alsace, p. 55.
Naumann, Erliiuter. zur geogn. Karte v. Sachsen. 1838, No. 2.

p. 96.

Cottain v. L. u. Br. Jahrb. 1853, p. 561.
Delesse in the Ann. des Mines, [5] vol. x. p. 317, and Compt.

rend. 1857, vol. xliv. p. 766. Ausz. in v. L. u. Br. Jahrb. 1858,

p. 848, and 1860, p. 724.
G. Leonhard, on Minette in the Odenwald Verhandl. d. nat.

med. Vereins zu Heidelberg, vol. ii. p. 7, and v. L. u. Br.

Jahrb. 1861, p. 495.

H. Mutter Neues Jahrb. f. Min. 1865, p. 1.
H. Pauly, Neues Jahrb. f. Min. 1863, pp. 257, 418.
Th. Elray, Minette im Morran. Neues Jahrb. f. Min. 1863,

p. 478, 1865, p. 745.

(B) FRAIDEONITE.

FRAIDRONIT. (Germ.)
FRAIDRO^ITE, E. Dumas. (Fr.)

MICA-TRAP ROCKS. 175

A greenish fehitic principal mass combined with a greater or less
quantity of mica. Iron pyrites and quartz occur as accessories.

This composition so evidently resembles that of minette that
it might well be considered as only a variety of that rock.
Lan, however, adheres to the name of fraidronite, which had
been already given by Dumas, and from the analyses which he
made, pronounces it to contain a considerable admixture of
chlorite, which he considered as the cause of its greenish colour.
He also found carbonate of iron and lime, which he considered
as accessory. Delicate veins of calcspar often pervade the
whole mass of the rock. On weathering it crumbles into balls
or a kind of grit. In the department of Lozere and in the
Cevennes it forms dykes and veins in talc-schist, mica-schist,
gneiss, and granite. Lan in the Ann. des Mines, [5J vol. vi.
p. 412 ; v. L. u. Br. Jahrb. 1858, p. 609.

KI;K> \vrnx. (Germ.)

KlillSANTON. (Fr.)

In a grwnuk-grty fekpathic matrix are contained hexagonal
tabular crystals of mica, broion to black. Less frequently the
matrix is granular, and contains crystals of felspar.
Contains silica about 53 p. c.

In the matrix, felspar usually predominates, which is not
orthoclase, but most likely oligoclase. The distinct crystals
of felspar are generally oligoclase. The mica is magnesian
mica, which is not only an ingredient in the matrix, but some-
times forms a coating round small globular grains (amygda-
loids) of calcspar or quartz. Marcasite and magnetic iron-ore
occur as accessories. Delicate veins of calcspar often run
through the whole rock.

The name of kersanton was first given by Riviere. The
rock is evidently closely allied to the inica-porphyiite, minette,
and kersantite.

It abounds in the district of Brest, and Quimper in Brittany,
where it is applied to building purposes.

References.

Riviere, intheBullet.de laSoc. gSol. deFr.,1844, [2] vol. i. p. 528.
Dufrenoi, Expl. de la Carte ge"ol. de la France, 1844, vol. i. p. 198.
Delesse, Ann. des Mines, 1851, vol. xix. p. 175,

(D) KERSANTITE.

KERSANTIT. (Germ.)

\\ KKSANTITE (OlJGOCLASITE). ( Fr.)

A fibrous or porphyritic compound of oliyoclase and mica, fre-
quently containing some hornblende and quartz.

Contains silica, about 64 p. c.

Oligoclase generally predominates in the compact or fine-
grained matrix of the rock, which sometimes is entirely com-

176 BASIC IGNEOUS ROCKS. (2) PLUTONIC.

posed of that species of felspar, sometimes of oligoclase and mica.
In this mass are enclosed crystals of oligoclase with brown
stripings, and of white or greenish colour, or tinged with red
by decomposition ; dark laminae of magnesia-mica, some small
grains of quartz, and frequently some fibrous hornblende, espe-
cially in the narrower veins formed by this rock, and, dispersed
through the whole rock, very minute particles of magnetic
iron -ore.

Carriere also found some red garnet combined with horn-
blende in places where the latter was more prevalent and the
rock somewhat fissile. At Viesembach, in the Vosges Moun-
tains, where the rock is broken through by metalliferous veins,
it contains magnetic iron pyrites and common pyrites. It is
amygdaloidal. In some places the amygclaloidal cavities are
filled with quartz, chlorite, epidote, and calcspar.

The porphyritic varieties of this rock (which owes its name
to Delesse) are evidently closely allied to the porphyrites, or
perhaps also to granite-porphyry; in other respects it very
nearly corresponds with kersanton, from which it is, perhaps,
only to be distinguished by its containing hornblende, and also
more quartz than that rock, and by its texture being sometimes
fissile.

Near Viesembach and Sainte Marie, in the Vosges, this rock
forms subordinate masses and veins in gneiss. The veins are
often quite compact at their borders. Fournet observed a
similar rock in the granite near Francheville in Brittany.

Reference.
Delesse, in the Ann. des Mines, 1851, vol. xix. p. 165.

SYENITE GROUP.

It has been a frequent practice to include under the
name of syenite all granites containing hornblende. But
as the genuine syenites contain little or no quartz, we
consider it more accurate to exclude the first-named rocks
from the syenite group, and range them under the head
of granites (syenite-granites), confining the term syenite
to those rocks which consist essentially of orthoclase or
microcline and hornblende, such as the rock of the
Plauenschen-Grund, near Dresden. Nevertheless there
is no precise boundary to be drawn between these and
the syenite-granites. As accessories, some mica and even
quartz may occur in syenite, but they are not essential
ingredients. This narrowing of the meaning of the
term syenite appears to us the more justifiable, as these
genuine quartzless rocks only contain 50-60 per cent, of
silica, and therefore can be included in the basic group ;

SYEXITE GROUP. 177

whereas those containing quartz have 60 70 per cent, of
silica, and so belong to the acidic group. It so happens
that the derivation of the name presents no obstacle to
our definition, since it is well known to have originated
in the erroneous belief that the antique stones which first
received the name of syenite came from Syene in Egypt,
which was not the case. Roziere therefore proposed to
alter the name to Sinaite, from Mount Sinai, where
genuine syenite is found, whereas at Syene only granite
occurs. Werner, who first introduced the name into
scientific petrography, applied it to the quartzless rocks
of the Plauenschen-Grund ; although afterwards, in his
' Klassification der Gebirgsarten ' (1787), he called the
same rock a greenstone.

In the syenite group we also include miascite, zircon-
syenite, and foyaite, as being closely allied to the genuine
syenite.

11. SYENITE.

SYEXIT, Werner. (Germ.)
SYENITE. (Fr.)

A crystalline granular compound of orihoclase or micro-
dine and hornblende, and usually some titanite.

Spec, grav 27 2-9.

Content of silica in the rock of the Plauenschen-Grund,
near Dresden, 55 60.

The orthoclase or microcline is usually the principal
ingredient, and being in general red, it gives that colour
to the whole rock, deepened into a brownish-red by the
hornblende. There are, however, syenites whose orthoclase
is nearly white, and others containing an admixture of
oligoclase. The andesine, which Delesse considered he
had found in some syenites of the Vosges^ is held by
Rose to be a decomposed oligoclase. An indistinct fissile
texture is sometimes occasioned by the parallel disposition
of the felspar crystals (sometimes twins), and a porphyritic
texture by the prominence of separate and larger twin
crystals. The hornblende is occasionally developed in
separate columnar crystals, but it usually only forms part
of the general crystalline granular mass of the rock. Be-
sides these, its two principal ingredients, syenite usually
contains some titanite (or wohlerite), forming minute

178 BASIC IGNEOUS KOCKS. (2) PLUTONIC.

brown crystals of adamantine lustre, dispersed through
the general mass, often only to be recognised with the
lens. Some mica, quartz, elaeolite (nepheline), zircon,
magnetic iron-ore, and pyrites, are also to be found in
the general mass, but only as accessories and in small
quantity. Epidote, which also occurs partly in the ge-
neral mass, and partly in the crevices of the rock, is
probably the product of a decomposition of hornblende ;
and an invisibly small proportion of carbonate of lime,
causing a slight effervescence with acids, is traced by
Bischoff to the same origin.

A larger proportion of mica and quartz occasions transi-
tions into syenite-granite or syenite-gneiss ; an increase of
elasolite and zircon, transitions into miascite and zircon-
syenite. Again, many syenites contain oligoclase as well
as orthoclase or microcline, opening up a transition into
diorite, which latter is essentially nothing but a syenite
containing oligoclase instead of orthoclase. This trifling
difference, which is usually connected with a coarser tex-
ture of the rock, may possibly only be a consequence of
the different level at which it attained the solid state. We
find, indeed, syenite in its bedding to be more decidedly
plutonic than diorite.

Varieties in Texture.

(a) COMMON SYENITE. \ Uniformly granular, as in the Plau-

( $KH enschen-Grund, near Dresden.
(6) POBPHYRITIC SYENITE. \ With separate and larger crys-

PORPHYRARTIGER SYENIT. (Germ.) > f -i f nr fi inP i Qca
SYENITE PORPHYROIDE. (Fr.) J tals Ol rtnodase.
Frh. von Richthofen has given the name of syenite-porphyry
to a rock of this class found hi the Visena Valley, near Predazzo,
in Tyrol. He desciibes it as consisting of a granular matrix of
orthoclase, with little hornblende, and sometimes oligoclase in
small quantity. The matrix enclosing twin crystals (three
inches long) of orthoclase.

It would be too much to say that there are no compact,
vesicular, or amygdaloidal varieties of syenite ; we are
only unable directly to trace any rocks of such textures
through transition states from genuine syenite so as to
show a direct connection with it ; and therefore we con-
fine the name to the distinctly granular compound of
felspar and hornblende, as above described. But amongst
the aphanites there are certainly compact and vesicular

SYEXITE GROUP. 179

rocks, whose chemical composition, at least, is so exactly
that of syenite, that under a slower and more plutonic
process of cooling, they might well have become syenite.
They bear the same relation to it as petrosilex to granite.
That these compact rocks do not occur in geological con-
nection with syenite may be owing to the thoroughly
plutonic origin of the latter, causing it always and every-
where to have cooled uniformly and very slowly. The
same observation applies to granite.

Properly speaking, there are no varieties of composition
to adduce, unless we consider as such those transitions
into granite and diorite which are occasioned by the
occurrence of mica, quartz, and oligoclase. The zircon-
syenite is rather a variety of miascite than of syenite
proper. But this seems a fitting place in which to in-
troduce the rock which Delesse has termed

MiCA-DioRiTE. ] It consists of a crystalline granular

(,!.!MMi.i;!)[oitrr. (Germ.)\ compound of hornblende, orthoclase,
Ditmrr^MiCACi, Beta*, t oligocla5e) mica> md very little ^^

' generally of a dark colour, almost

black. Content of silica only 48. From this composition we
may regard this rock as something between diorite, syenite,
and granite. In the Vosges it occurs in dykes in granite.

Syenite is usually jointed into large irregular or thick
tabular masses ; it forms entire mountains and occupies
extensive regions ; only seldom forms distinct veins or
dykes in other rocks, but is not unfrequently traversed
by granitic veins, or it often contains granitic concre-
tions. It is often associated v with great tracts of granite,
and then passes over into syenite-granite, and finally into
granite. The syenite of the Plauenschen-Grund, near
Dresden, is eminently characteristic. Near Ditro, in Tran-
sylvania, instead of titanite it contains much wohlerite.

References.

Xinimtmn on the Saxon Syenite, Erlauterung zur geog. Karte

von Sachsen, 1845, No. 6, p. 116.
L. van Such on the Monzon-syenite in v. Leonhard's Taschen-

buch, 1824, p. 345.
von Richthofen on Monzon-syenite, in Geogn. Beschr. v. Siid-

Tyrol, 1860, p. 144, which contains, besides orthoclase and

hornblende, some oligoclase, mica, and pyrites; ibid. p. 150.
Zirkflj Syenit des Plauenschen-Grundes. * Poggendorf s Ann.

vol. cxxii. p. 621.

N 2

180 BASIC IGNEOUS KOCKS. (2) PLUTONIC.

Delesse on Mica-diorite, in which he also includes rocks from
the Kuhlenberg, near Harzburg, (gabbro ?) and from the
Felsberg, near Darmstadt, in the Ann. des Mines, 1851, [4]
vol. xix. p. 150. Karsten's Archiv. 1851, vol. xxiv. p. 280.
Bullet, de la Soc. geol. de Fr. 1850, vol. vii. p. 524. The
syenite rose cFEgypte here described is granite, Ann. des

jnsyenit in v. L. u. Br. Jahrb. 1848, p.
The following works on Syenite relate partly to rocks rich in

quartz, which we class under the head of syenite-granite,

viz. :

v. Dechen in v. L. u. Br. Jahrbuch, 1858, p. 339.
v. Rath in v. L. u. Br. Jahrbuch, 1858, p. 339.
Streng in Poggend. Ann. 1853, vol. xc. p. 132.
Kjerulfj Christiania Silurbecken, 1855, pp. 8, 12, and 15.

12. MIASCITE.

MIASCIT. (Germ.)
MIASCITE. (Fr.)

A crystalline compound of orthoclase, nepheline, socialite,
and black mica ; coarse-grained to fine-grained (in
the different varieties other minerals also occur).

This rock was first discovered by G. Rose in the Ural
Mountains. Its orthoclase is Breithaupt's Mikrokline,
and is white or grey ; the nepheline is yellowish-white
(elaeolite) ; lustre only slightly resinous ; the sodalite is
grey or a fine blue ; the black mica is nearly unaxial.
Besides these principal ingredients, the following occur,
but frequently" only as accessories : davyne, wohlerite,
zircon, magnetic iron-ore, pyrites, pyrochlore, cancrinite,
apatite, monazite, even quartz, hornblende, &c. By means
of these minerals, transitions take place into granite,
syenite, and especially zircon-syenite. At Miask the
texture of this rock is sometimes fissile ; at Ditro, in
Transylvania, where miascite occurs at the margin be-
tween syenite and mica-schist, and intimately blended
with the former, the blue sodalite is frequently arranged
in layers, and the texture is generally very unequal,
sometimes quite coarse, sometimes fine-grained.

References.

G. Rose, Eeise nach dem Ural, vol. ii. pp. 47, 93, and 535,
and Poggend. Ann. vol. xbii. p. 375.

SYENITE GROUP. 181

firrithaupt, Berg- u. Huttenin. Zeit. 1861, p. 493.
t'otta, ibid. 1862, p. 73.

Varieties in Composition.

A. ZIRCON-SYENITE.

ZJRKONSYENIT, Von Buch. (Germ.)
SYENITE ZIRCONIENNE. (-fV.)

A crystalline-granular compound of orthoclase, nepheline (elaolite),
zircon, and usually only little hornblende.

This rock is closely allied to miascite, both in respect of its
essential and accessory ingredients. However, its composition
varies so much in different places, that it is frequently difficult
to decide what are essential and what accessory ingredients.
The principal place where it occurs is the district of Laurvir
and Brevig, in Norway: here there also occur eukolite and
eudialite as accessory ingredients.

References.

L. v. Buch, Reise nach Norwegen, vol. i. p. 133.
Ifamsmann, Reise nach Skandinavien, vol. ii. p. 103, and
vol. x. p. 235.

B. FOYAITE.

FOYAIT. (Germ.)

A crystalline granular compound of orthoclase-mepheline (elaolite),
and hornblende.

Spec. grav. . ** 2*6.

The orthoclase is white or greyish-white, forms long tabular
crystals with twin growth^(but not very perfectly developed),
and is decidedly predominant. The reddish elaeolite of greasy
lustre occurs in single hexagonal crystals.

The greenish-black hornblende forms columnar crystals or
small grains and parts of grains. The varieties of texture are
the coarse-grained, fine-grained, compact, and porphyritic ; the
latter contain crystals of orthoclase and elaeolite in a fine-
grained matrix. The orthoclase crystals themselves some-
times contain elaeolite and hornblende. The texture often
changes very rapidly, as in gabbro. As accessories there
occur titanite and magnetic iron-ore (very frequent), hexagonal
brown laminae of mica, and iron-pyrites.

This rock forms the mountains Foya and Picota in the pro-
vince of Algarve in Portugal, where it is jointed in irregular
masses. Blum has named it after the first mountain.

Blum in von Leonhard's Jahrbuch, 1861, p. 426.

182 ACIDIC IGNEOUS ROCKS. (l) VOLCANIC.

ACIDIC IGNEOUS EOCKS.

These rocks are compounds of orthoclase, sanidine, or
oligoclase, with quartz, mica, or hornblende.

They also contain many other minerals as accessories.

Their proportion of silica is almost always above 60
per cent., and extends in some cases to upwards of 80
per cent.

Their texture is generally granular or porphyritic, but
sometimes compact or vitreous, seldom vesicular, and never
amygdaloidal. Frequently they have a somewhat fissile
or foliated structure, and so they even form transitions
into certain of the crystalline schists.

Like the basic rocks, they are divisible into the volcanic
and the plutonic.

1. Volcanic.

In the rocks of this division the prevailing species of
felspar is sanidine or oligoclase ; the labradorite (rich in
lime), so often found with pyroxene in the basic rocks,
is very rare in the acidic. The felspar is combined with
some hornblende, and more rarely also with quartz, yet
the rock always contains a large proportion of silica ;
augite is only an accessory ingredient.

The volcanic acidic rocks fall into two principal groups ;
the trachytes and phonolites. The trachytic group, how-
ever, contains many varieties both of composition and
texture, and hence a great number of separate names,
such as pearlstone, obsidian, &c. The trachytes occur
as lava at active volcanoes of the present day, which is
rarely, if ever, the case with the phonolites. Perhaps
the latter are, to a certain extent, products of transmu-
tation from compact or porphyritic trachytes.

Although the trachytes, when characteristically deve-
loped, differ very widely from the basalt, so that these
two may be called the extreme products of volcanic
agency, yet there are many volcanic rocks of intermediate
character, which, to a certain extent, form transitions
between the two groups, and prevent any very definite

TRACHYTE GROUP. 183

line of distinction between them. In many individual
cases it is, in fact, difficult to distinguish trachytic from
basaltic rocks.

THE TRACHYTE GROUP.

The term trachyte, signifying rough stone, was first
introduced by Hatiy, to denote a crystalline granular com-
pound, in which sanidine, as the predominant ingredient,
is combined with some other felspar, with hornblende (or
augite), mica, or even quartz, in subordinate quantities.
The principal mass is sometimes fine-grained, or even
compact, with distinct minerals porphyritically prominent.

Soon after Haiiy had first called attention to this rock,
many other rocks came to be observed, having the same
mineral composition, differing somewhat from it in tex-
ture, but connected with the normal trachyte by inter-
mediate transition states. These were called trachytic
rocks, without being reckoned as actual trachytes ; thus,
for instance, trachyte-porphyry, pearlstone, obsidian,
pumice-stone, and many compact as well as porous tra-
chyte-lavas.

Then it was discovered tfyat many of the rocks which,
without accurate mineralogical investigation, had been
taken for trachyte of the 'prescribed composition, con-
tained an oligoclase-felspar instead of the sanidine for-
merly considered so essential an ingredient ; but in other
respects their trachytic character was preserved. Ac-
cordingly, the trachytes came to be divided into sanidine-
trachyte and oligoclase-trachyte ; these two varieties are,
however, connected with each other by many transition
states, and their geological position and character are
identical. In compact or fine-grained states the difference
between them is scarcely to be recognised ; the varieties
of texture appear likewise to be essentially the same in
both.

It may be useful, before going on to the description of
the individual trachytic rocks, to take a general survey of
what have been described under that name, and the mode
in which different writers have dealt with the different
varieties.

Before the difference as to the species of felspar was re-
cognised or known, the following varieties of the rock were

184 ACIDIC IGNEOUS KOCKS. (1) VOLCANIC.

distinguished by Beudant (in his Voyage en Hongrie),
and by Bur at (in his Description des Terrains vole, de la
France centr. 1833), and also by Naumann.

(a) TRACHYTES.

Trachyte granitoide (granitic trachyte), e. g. at Handerlo, near
Schemnitz.

Fibrous or gneiss-like Trachyte, e. g. on the Pontellaria.

Trachyte schistoide (schistous trachyte), e. g. at the Pas de
Compain, department of Cantal in France.

Trachyte a gros crystaux, a trachyte rich in felspar, at Dra-
chenfels, near Bonn.

Trachyte amphibolique, a trachyte rich in hornblende, e. g.
near Schemnitz (perhaps the same as Breithaupt's timazite).

Trachyte micace (micaceous trachyte), Monte Catini, in
Tuscany.

Domite, or Trachyte terreux (domite or clay stone-like tra-
chyte), e. g. at the Puy de Dome.

Trachyte porphyrolde (porphyritic trachyte), Schemnitz and
Kremnitz in Hungary.

Trachyte homogene (simple trachyte), frequently resembling
phonolite, Monts Dores in Velay.

Trachyte semi-vitreux (semi-vitreous trachyte), Tokay in
Hungary; Iceland.

Masenga, according to Naumann, the genuine trachyte of
the Euganean Hills in Lombardy.

Nenfro of Brocchi, according to Naumann, genuine trachytes
of the Cimini Mountains.

Nekrolite of Brocchi, according to Naumann, trachyte from
Viterbo and Tolfa.
(6) TRACHYTE-PORPHYRIES CONTAINING QUARTZ.

Perlite-like Trachyte-porphyry. Hungary.

Porous Trachyte-porphynj . Hungary.

Vesicular Trachyte-porphyry (with globular cavities). Hun-
gary.

Millstone porphyry, or cavernous trachyte-porphyry. Miih-
lensteinporphyr, or cavernoser Trachytporphyr. Porphyre
meulier. Hliniker valley, in Hungary.

Clay stone-like Trachyte-porphyry. Thonsteinahnlicher Tra-
chytporphyr, Ponza Islands.

(<?) Q.UARTZLESS TRACHYTE-PORPHYRIES. A

Perlite-like Trachyte-porphyry, withom quartz. Hungary.

Clay stone-like Trachyte-porphyry, wi^)iit quartz. Hungar} r .

Pumice-stone-like Trachyte-porphyry, without quartz. Hun-
gary.

Slaty Trachyte-porphyry, without quartz. Ponza Islands.
(d) PERLITES AND PEARLSTONE-PORPHYRIES.

Perlite testace (granular shelly perlite). Telkebanya in
Hungary.

Spherolitic pcrlite or spherolite rock. Schemnitz in Hungary.

Perlite retinitiqi{e (pitchstone-like perlite) ; Ofen in Hungary.
Lipari Islands.

TRACHYTE GROUP. 185

Perlite porphi/rique (perlite porphyry), Hungary.

Perlite litho'ide. compacte (clay stone-like perlite), Hungary.

Perlite ponceaux (perlite pumice-stone), Hungary.
(e) PURE OBSIDIAN.

Porphyritic Obsidian, or obsidian-porphyry, spherulitic obsi-
dian.
(/) PUMICE-STONE.

Obsidian pumice-stone.

Perlite pumice-stone.

Trachyte pumice-stone,
(g) ANDESITE.
(h) TRACHYTE-DOLERITE.

In the decomposed states of trachyte, and especially in the
so-called alumstone, we can of course not recognise the fresh
state of the rock.

The first thing which strikes us with reference to the
foregoing catalogue is the great number and variety of
rocks which may be included under the head of trachyte
in its more extended signification. All the distinctions
which have been made are, however, not equally important.

Some varieties occur only in one locality, and some
scarcely belong to the trachytes at all.

In investigating a particular district, we should, of
course, notice the smallest modifications in the nature of
the rocks which come under our observation ; but for the
purposes of definition in a general treatise like the present
it is impossible, and would be undesirable, to record every
trifling variety of texture and composition.

G. Rose, in the 4th vol. of the ' Kosmos,' has proposed
to subdivide all trachytic rocks into the six following
groups :

1. A rock whose principal mass consists entirely of crystals of

vitreous felspar, which are tabular and usually large. Little
or no hornblende and mica are contained in its composition,
and are quite non-essential as ingredients Campi Phelegrai,
Ischia, La Tolfa, &c. Augite shows itself in small crystals in
the Mont Dore", but very rarely. In the Campi Phelegrai,
where there is hornblende there is no augite, also no leucite, but
of this last mineral Hoffman discovered some specimens at the
Lake of Averno, and G. Rose on the cliffs of the Monte Nuovo.

2. A rock whose principal mass contains single vitreous felspar crys-

tals and a great number of small snow-white oligoclase crystals.
The latter are frequently regular, and grown into the vitreous
felspar, and form a covering round it. Sometimes a small
proportion of hornblende and mica, and in some varieties
aujnte, are found in it.
The trachytes of Drachenfels and the Perlenhardt in the

186 ACIDIC IGNEOUS ROCKS. (!) VOLCAXIC.

Siebengebirge, and many varieties in the Mont Dore and Cantal,
belong to this subdivision.

3. These are dioritic trachytes whose principal mass contains many
small oligoclase crystals with black hornblende and brown
magnesian mica. To this species belong the trachytes of
^Egina, the Kozelniker valley near Schemnitz, Nagyag in
Transylvania, and Montabaur in Nassau, Stenzelberg and
Wolkenburg in the Siebengebirge, Puy de Chauniont, near
Clermont, and Liorant in Cantal. The Kasbegk in the Cau-
casus, the Mexican volcanoes of Toluca and Orizaba, also the
domites of L. v. Buch, belong to this subdivision. In the white
fine-grained matrix of the trachytes of the Puy de Dome are
enclosed vitreous crystals which have always been considered
to be felspar, by which term Rose implies orthoclase, but the
cleavage surfaces of which always show striae, and are, there-
fore, in fact, oligoclase. (The above-named examples from
Hungary and Transylvania belong to Breithaupt's timazite.)

4. The principal mass contains augite and oligoclase. The peak of

Teneriffe, the Mexican volcanoes, Popocatepetl and Colima, the
South American volcanoes, Tolima, Purace near Popayan,
Pasto, and Cumbal Ruca Pichincha, Antisana, Cotopaxi, Chim-
borazo, Tunguragua. In Tunguragua, associated with the
augite crystals, there occur small independent crystals of uralite
of blackish-green colour (diabase or dolerite ?).

5. A combination of labradorite and augite, a doleritic trachyte,

^Etna, Stromboli, &c. (Why should not these rocks be genuine
dolerites ?)

6. A rock whose matrix is usually grey, in which crystals of leucite

and augite are enclosed, with some olivine (very little). Vesu-
vius and Somma ; also the extinct volcanoes Vulture, Rocca
Monfina ; the Albanian Mountains and Borghetto. (This is
the same as our leucite rock.)

It will be seen that Rose's idea of trachyte is much
more extended than is at all usual : it embraces almost all
the volcanic rocks.

More recently Freiherr v. Richthofen has divided the
trachyte formations of Transylvania and Hungary into
two classes the rhyolitic and trachytic. The latter are
almost exclusively rocks containing hornblende and oligo-
clase as their essential constituents. Sanidine is not the
predominant felspar except in certain rocks of the most
recent and subordinate eruptions ; so that, speaking gene-
rally, according to von Richthofen, by far the greater
proportion of the whole group of trachytes (proper)
consists of oligoclase, and not of sanidine rocks. The
silica is never so abundant as to develope distinct crystals
of quartz.

TRACHYTE GROUP. 187

Von Richthofen subdivides the trachytes again into
' greenstone trachytes ' and ' grey trachytes.' The former
(our timazite) often correspond exactly with the oldest
diorites and dioritic porphyries. The latter, on the other
hand, consist principally of oligoclase and hornblende,
with the occasional addition of some augite.

Under the term rhyolite, Richthofen embraces all the
most acidic (richest in silica) amongst the recent igneous
rocks. He especially instances in Hungary the trachyte-
porphyries, perlites, &c. (Vide L. u. 13. Jahrb. 1859,
p. 304, and 1861, p. 98 ; Jahrbuch d. geol. Reichsanst.
1860, Sitzungsber. p. 92.)

These two groups of trachytes proper and rhyolites
certainly appear of general geological importance ; they
bear the same relation to each other, within the acidic
group, as the acidic rocks bear to the basic ; and although
in Hungary they both belong to one and the same great
tertiary eruptive period, the rhyolites always appear the
more recent of the two.

We find similar phenomena in the rocks of all eruptive
periods, the plutonic as well as the volcanic. Where
syenites and granites occur together, the granite (rich in
silica) is usually the most recent ; in the same way we
often find veins of granite intersecting the gabbro (poor
in silica). In the Thuringian Forest the quartz-porphy-
ries are in general of more recent origin than the mica-
porphyrites (poor in silica), although they both belong
to the same great period. In the Bohemian Mittelge-
birge, whose conical mountains consist partly of basalt
and partly of phonolite, both of which appear to have
been formed during the tertiary period, the phonolite
(somewhat the richer of the two in silica) is found
throughout as the most recent; so that putting all these
facts together, we are almost justified in holding it for a
universal law, that wherever igneous rocks rich in silica
occur together with basic igneous rocks of the same great
period of eruption, the former are of somewhat later
origin than the latter. Basalt, nevertheless, sometimes
forms an exception to this rule, as in Hungary, where it
penetrates the trachytes ; but it is questionable whether
the basalt in these cases may not belong to a separate
period more recent still than the trachytes.

188 ACIDIC IGNEOUS EOCKS. (l) VOLCANIC.

If we find it impossible to define a precise boundary
between the acidic and basic volcanic rocks, any more
than between the volcanic and plutonic groups themselves,
there can hardly be matter for surprise ; we should, 011
the contrary, be at a loss to explain any such sharp dis-
tinction if it existed. We find rocks of character' so
undecided, that we may with almost equal justice group
them with the greenstones as the trachytes. Such, for
instance, is timazite. With others it may appear doubtful
whether we should attach them to basalt or trachyte. Such
are trachydolerite and andesite. The latter was in the first
instance, without much inquiry, grouped with the trachytes
because of its geological position and its rough texture.
Subsequently the prevailing felspar species was taken for
albite, and L. von Buch called the rock andesite from the
Andes, where it occurs in great extent, to distinguish it
from ordinary trachyte ; and although it has lately been
discovered that the felspar is not albite but oligoclase,
that does not seem to us to furnish a sufficient reason for
changing the name of the rock (as proposed in e Kosmos'),
if we wish to preserve any individuality for it at all. It
may, however, remain questionable how the rock should
be grouped. If we find with the oligoclase, pyroxene
and hornblende occurring as essential and important in-
gredients ; if the rock contains no quartz, but occasionally
dark magnesia-mica, olivine, and titanite (and always
magnetic iron-ore), then it may certainly be that andesite,
if a volcanic product, should be assigned to the basalts ;
or if plutonic, to the greenstones. Whilst, on the other
hand, its somewhat high proportion of silica (59 67 per
cent.), as well as its sometimes vitreous state, is opposed
to this grouping, and gives the rock a more trachytic
character. It is for these reasons a rock of middle cha-
racter, of which there are many such. Roth even distin-
guishes a pyroxene-andesite and an amphibole-andesite.
With the first he classes many volcanic rocks of Iceland
and TenerifFe ; with the latter, the so-called trachytes of
Wolkenburg, and of Stenzelberg in the Siebengebirge, the
domite of the Puy de Dome, and many lavas of ./Etna.

The trachytes often form an essential part of the pro-
ducts of active volcanoes, and form actual lava streams.

They are also frequently found at so-called extinct

TRACHYTE GROUP. 189

volcanoes; and form single conical hills or connected
groups of mountains in districts where, since the tertiary
period, no eruptions have taken place. These last-men-
tioned older trachytes approach in character the plutonic
rocks. We are, however, unacquainted with any trachytes
which arc certainly older than the Tertiary period.

AYe propose, with Von Richthofen, to divide all the
trachytic rocks into two separate sub-groups (trachytes
and rhyolites), the differences between which are more
marked than those of the several varieties of mere texture
and composition. These latter differences are, however,
important enough to deserve a more special notice than
the corresponding varieties of many other rocks ; and
we shall, therefore, accord them a full description, merely
premising in general that theyare apt to run one into the
other by gradual transitions occasioned by the prepon-
derance or the reverse of a principal ingredient.

13. TRACHYTE.

TRACHYT. (Germ.')
TRACHYTE, Haiiy. (Fr.}

A compound of sanidine, oligoclase (or even albite and
labradorite), ivith some hornblende or augite and dark-
coloured mica. A rough principal mass in which, as
matrix, some of its mineral constituents are jrequently
distinctly and separately developed and imbedded.

Spec, grav 24 2-8

Contains silica .... 50 67 p. c.

As a rule, in all trachytes the felspar is predominant.
The detailed grouping of their different mineral ingre-
dients will appear from the description which we give
below of the several varieties in composition.

Varieties in Texture,
(a) GRANULAR TRACHYTE.

KMKMGER TRACHYT. (Germ.)
TRACHYTE GRAxrrolDE. (Fr.)

(5) PORPHYRITIC TRACHYTE. \

PORPHYRARTIGER TRACHYT. (Germ.) \ With larffe felspar Crystals.
TRACHYTE PORPHYHOIDE. (Fr.) )

/..KM..,, Hmn.TKK TRACHYT. (Germ.)\ approaching the compact.)
TRACHYTE LITHOH>E. (Fr.) ) Also somewhat porphyritic.

190 ACIDIC IGNEOUS ROCKS. (l) VOLCANIC.

(d) VESICULAR TRACHYTE. ^ often, par excellence, called Tra-

BLASIGER TRACHYT. (Germ.) r T , /
TRACHYTE VACUOLAIRE. (Fr.) ) ch V te iam '

(e) DECOMPOSED TRACHYTE. \ Manv decomposed varieties are

ZERSETZTER TRACHYT. {Germ.) called Alumstone, on account of
TRACHYTE DECOMPOSE. (Fr.) ) their containing alum.

Varieties in Composition.

(A) SANIDINE-TRACHYTE.

SANIDIN-TRACHYT. (Germ.)

An aggregate of sanidine crystals, with some hornblende or mica as
subordinate ingredients. Texture coarse or fine- grained to compact.

Spec. grav. . ... . . . . 2 -4 2-6

Contains silica - . : . . / . - r 59 60 p. c.

In this compound, principally consisting of sanidine, horn-
blende, and magnesia-mica, occur, as accessory ingredients,
magnetic iron-ore, sodalite, olivine, titanite, and augite or
quartz. It further appears probable, from the frequent pre-
ponderance of the proportion of soda over the potash in the
whole rock, that the compact matrix which permeates the
whole nias?, cementing the distinct and recognisable minerals,
contains, in addition to those we have mentioned, some mineral
rich in soda, such as oligoclase, sodalite, or nepheline. The
sanidine often occurs in a porphyritic form. The colour of the
rock fluctuates between greyish-white and dark-brown grey.
In most cases the texture is porphyritic, with granular or
sometimes compact matrix ; some varieties are vesicular, and
at the surface even scoriaceous, but not amygdaloidal. By
decomposition a state is produced, not wackenitic, but more
resembling claystone. The mass then appears almost white,
whereas, in fresh condition, it is often very dark-coloured.
The rock is generally of irregularly jointed structure.

To this species belong, according to Roth, the trachytes of
Rabertshausen, in the Grand Duchy of Hessen ; of Kappellen-
berg (which contains some pyrope) ; of Mondhalde and Silber-
brunnen, at the Kaiserstuhl j of Gleichenberg, in Styria ; of
Monte Olibano, near Pozzuoli. Likewise the lavas found at
Monte Nuovo, and those of the Azores, &c.

The grey porous sanidine-trachyte, which occurs at the
Laager lake, contains a good deal of haiiyne.

(B) SANIDIXE-OLIGOCLASE-TRACHYTE (DRACHENFELS TRACHYTE).

SANiDrsr-OLiGOKLASTRACHYT. (Germ.)

A crystalline compound of sanidine and oligoclase with mag-
nesia-mica and hornblende, also some augite, magnetic iron-ore,
and titanite.

Spec, grav 2'6 2-7

Contains silica . . . . 60 67 p. c.

This very characteristic rock of the Drachenfels, near Bonn,
with its large sanidine crystals porphyritically enclosed in
granular matrix, served a long time as the principal type of the

TRACHYTE GROUP. 191

trachytes, and all the felspar in that rock was assumed to be
sanidine. Now, however, it appears, from the very consider-
able quantity of soda contained in the matrix (up to 5 per
cent.), that tlie latter probably consists principally of oligoclase.
It is especially worthy of remark tnat in this porphyritic
trachyte the large sanidine crystals frequently assume a parallel
position to each other ; they are also sometimes broken in
two, but both pieces still lie close together imbedded in the
matrix. According to Roth, to this class belong the trachytes
of Kiihlsbrunnen, in the Siebengebirge, and Freienhauschen, in
the Eifel ; also, according to Richthofen, many trachytes of
Hungary and Transylvania.

OLIGOKLAS-TRACHYT. (Germ.)
DOMITE. (Fr. )

In this rock oliyoclase is the only recognisable felspar, as it con-
tain* no xaniiliitc. The oligoclase is combined with some horn-
blende or anyite and dark-coloured mica.

These trachytes have been the least accurately analysed of
any. They contain many other accessory minerals. *If the
quantity of hornblende be above the average, then they pass
into greenstones, e.g. into the greenstone-trachyte of Richt-
hofen, or the timazite of Breithaupt. Whether andesite
and trachydolerite should be included here may be doubtful.
We prefer to treat them separately. This variety occurs in a
tolerably fresh state at Stenzelberg', and at Wolkenburg, in the
Siebengebirge. At the Puy de Dome, on the other hand, it is
much decomposed, rough, almost crumbly, and is there called
domite. It would be hazardous to attempt to distinguish
varieties of texture.

At Stenzelberg this rock exhibits a singular cylindrical
jointed structure, in so-called 'outliers,' which consist of round
columns, composed of concentric layers. Usually its structure
is massive.

(D) ANDESITE.

ANDESIT. (Germ.)
ANDESITE. (Fr.)

A fine-grained or compact, and sometimes mtreous matrix, usually
of dark-grey to black colour; contains crystals which, accord-
ing to G. Rose, are oligoclase and augite. According to Abich,
on the other hand, they are albite or oligoclase; and Abich
adds, that some sanidine and hornblende, and always tiwyni'tic
iron- ore, are likewise found in the rock. Dark-coloured mica
frequently also occurs.

Spec. grav. ,.;.. . . . 2-62-7
Contains silica 50 67 p. c.

Roth distinguishes an amphibole-andesite and a pyroxene-
andesite, but as the latter likewise contains some hornblende,
this distinction would be difficult to maintain. To the amphi-
bok-endesites, according to him, the localities which we have

192 ACIDIC IGNEOUS ROCKS. (1) VOLCANIC.

above given under the head of * oligoclase- trachyte ' apply ;
to the pyroxene-andesite, many volcanic rocks of Iceland and
Tenerifte.

This rock was first named by L. v. Buch, and its felspar was
taken to be entirely albite. G. Kose could only discover oligo-
clase in it. Doubts have also arisen respecting the other in-
gredients. The matrix is sometimes easily to be reduced to
powder. Known localities of its occurrence are : Pinchincha,
Chimborazo, Antisana, and Cotopaxi j according to Abich, also
the Caucasus and Mount Ararat.

(E) TRACHYDOLERITE.

TRACHYDOLERIT. (Germ.}
TRACHY-DOLERITE. (Fr.^

A compound of oligoclase (or labradorite) with hornblende or
augite, some magnetic iron-ore, and frequently also mica. These
minerals lie imbedded in a grey or brown matrix.

Spec, grav 2-72-8

Contains silica . . . . . 54 61 p. c.

We may here distinguish the varieties which contain horn-
blende from those which contain augite j the latter are very
nearly related to dolerite.

Vesicular varieties also occur. Abich, who first distinguished
this rock and gave it its name, designates the following places
where it is found : The Peak of Teiieriffe, the Schivelutsch in
Kamtschatka, the island of Liscanera, near Stromboli, and the
older lavas of ./Etna, for the varieties which contain hornblende ;
and the top of the crater of Stromboli, and the central cone of
the Rocca Monfina, for those containing augite.

Deiters recognised in the rock of the Lowenburg, in the
Siebengebirge, a complete transition grade between trachyte
and dolerite. Under the microscope its principal mass appears
to consist of crystalline felspar (either oligoclase or labradorite),
imbedded in which lie scattered crystals of striated felspar,
of hornblende, augite, magnetic iron-ore, and even some olivine.
The content of silica here diminishes to 52 per cent.

References.

Beudant, Vovage en Hongrie, translated (into German) by

Kleinschrod, 1825.
Abich, Vulkanische Erscheinungen, 1841 j Vulkanische Bil-

dungen, 1849; Natur des armenischen Hochlandes, 1843,

p. 25 j and Poggendorf 's Annalen, 1840, vol. 1. p. 345.
Bunsen, in Poggendorf 's Annalen, vol. Ixxxiii. p. 197.
Sartorius v. Walterhausen, Die vulk. Gesteine in Sicilien und

Island, 1853.
Schill, in G. Leonhard's Beitr. z. mineral. Kenntn. von Baden,

1854, No. 3, p. 46.
Deville, Sur le Trachytisine d. Eoches, in Compt. rend. 1859,

vol. xlviii. p. 16.
Enyelbach, in the Erlauter. d. geogn. Karte von Hessen. Sect.

Schotten. Darmst. 1859, p. 43.

TRACHYTE GROUP. 193

Rammehberg, in Zeitschr. d. d. geol. Ges. 1859, vol. xi. p. 434.

Zirkel, Die trachytischen Gesteine der Eifel, in Zeitschr. d. d.
geol. Ges. 1859, vol. xi. p. 507.

L. v. Buch on Andesite, in Poggendorf 's Ann. vol. xxxvii. p. 189.

v. Dechen gives eight divisions of trachyte in his Geogn. Beschr.
des Siebengebirges (Verhandl. d. nat. Ver. d. Rheinlande,
1852). He appears, however, to have abandoned these in
his more recent ' Geogn. Fiihrer durch d. Siebengebirge.'

Zehler observed, in 1837, as many as forty different trachyte
varieties in his l Siebengebirge.'

Vom Rath, in his treatise, ' Die Trachyte des Siebengebirges,'
1860, makes the following divisions :

1. Drachenfels trachyte, whose white or grey matrix con-
tains crystals of vitreous felspar and oligoclase, and some
magnesia-mica and hornblende; accessorily, titanite, mag-
netic iron-ore, augite, and apatite. Content of silica, 65 66.

2. Wolkenburg trachyte. 1 he colour of the matrix from grey
to black, or sometimes reddish. It contains crystals of oligo-
clase, no vitreous felspar, but some hornblende and magnesia-
mica. Accessorily, augite, olivine, magnetic iron-ore, pyrites,
and perhaps some quartz. Content of silica, 59 62 per cent.

3. Trachyte of Rosenau (not in connected rocks, only found
in blocks). The base contains crystals of vitreous felspar,
no oligoclase, more rarely some magnesia-mica, hornblende,
sphene, and magnetic iron-ore. Content of silica, 78*8.

The matrix appears in all these three varieties to be prin-
cipally felsitic. Acid produces a weak effervescence, which
may well be owing to carbonates of later origin than the
rock itself, and the small quantity of zeolite which occurs is
in all probability the result of decomposition.

Vom Rath, Ueber Trachyt d. Enganeen. Zeitschr. d. deutschen
geol. Ges. 1864, pp. 254-498.

Deitei-s, Die Trachytdolerite des Siebengebirges, in Zeitschr.
d. d. geol. Ges. 1861, p. 99.

v. Richthofen, in the Jahrbuch d. geol. Reichsanst. 1860, Sitz-
unjrsber. p. 92; extract in von L. u. Br. Jahrbuch, 1859,
p. 304, and 1861, p. 98 ; Jahrb. d. geol. Reichsanst. 1864, p. 7.

Stache has given the name of DACIT to a quartzose trachyte of
Transylvania. Geogn. Beschr. von Siebenbiirgen.

14. KHYOLITE.

RHYOLITH. (Germ.)

A compact, enamel-like, or vitreous matrix enclosing
grains or crystals of sanidine, oligoclase, mica, or
even quartz.

Spec. grav. . , , * 2'3 2-6
Contains silica 67 82 p. c.

The matrix, which should, strictly speaking, always be
of a prevailing felsitic character, varies however from the

194 ACIDIC IGNEOUS KOCKS. (l) VOLCANIC.

simple compact to the vitreous state. It is distinguished
from that of the trachyte proper by its larger proportion
of silica; and the same difference in the proportion of
silica is found to obtain between the trachytes and rhyo-
lites in the collective analysis of each rock in its entirety.
Hence in rhyolite free quartz appears much more fre-
quently than in genuine trachyte ; on the other hand, the
former contains no hornblende or augite, or, at least,
those minerals are much more rarely found in it than in
trachyte.

Under the common name of rhyolite we comprehend
the following principal varieties : Trachyte-porphyry,
perlite, obsidian, and pumice-stone, all of which possess
sub-varieties.

A. TKACHYTE-PORPHYKY. Liparite.
TRACHYTPORPHYR, LITHOIDIT in part. (Germ.)

PORPHYRE TRACHYTIQUE. (Fr.)

A compact felsitic matrix containing crystals of felspar,
and sometimes also mica or quartz. But as this
general definition essentially agrees with that of
many porphyrites and quartz-porphyries, it is per-
haps better to say : Trachyte-porphyry is the name
given to those rocks (prevalently felsitic and porphy-
ritic with a compact matrix) which are geologically
allied to the trachytes.

Spec, grav 2-42-6

Contains silica ...... 67 81 p. c.

The trachyte-porphyries are, as a rule, much richer in
silica than the trachytes proper which we have described
above. Their matrix is of prevalent felsitic composition
and character, scarcely to be distinguished from that
of the quartz-porphyries, and it only very rarely and
exceptionally contains some traces of hornblende.

Some trachyte-porphyries even contain grains or crys-
tals of quartz or mica, or of both those minerals together,
and thereby their resemblance to quartz-porphyry, gra-
nite-porphyry, or mica-porphyrite, becomes still greater,
and in fact so great, that occasionally, in the form of
single specimens, it is impossible to tell the difference.
In these cases, the only real difference consists in their
geological connection with genuine trachytes or their

TRACHYTE GKOUP. 195

petrographical transition into perlite or pumice-stone.
The felspar of the distinctly developed crystals in
trachyte-porphyry is most usually oligoclase, but some-
times also sanidine ; both of these also occur in quartz-
porphyries.

The most important varieties in texture, but which
may almost all be divided into those with, and those
without, quartz, are t

(a) COMMON TRACHYTE-PORPHYRY. ) Its felsitic matrix is compact
GEMEIXER TRACHYTPORPHYR. (Germ.) > i n fresh fracture, and fre-
quently somewhat shining ; usually light-coloured, containing
(more "or less plentifully dispersed) crystals of sanidine or
oligoclase, mica, or sometimes quartz. At the Schlossberg of
N'-usohl the matrix is of greenish colour, compact, with crystals
of felspar, mica, and quartz, ^n the Hliniker valley, near
Schemnitz, the matrix is yellowish, and especially distinguished
for its crystals of mica.

(/>) PERLITE-LIKE TRACHYTE-PORPHYRY. ) The matrix is often
PERUTAHNLICHER TRACHYTPORPHYR. (Germ.) f somewhat enamel-
like, and contains, besides those crystals which we have men-
tioned, small compact balls of felspar (spherulites), frequently
with radial fibrous texture, sometimes also grains of quartz
and mica. These rocks pass over by transition into perlite.

(e) ARGILO-TRACHYTE-PORPHYRY. ) The matrix is dull

THOXSTKIXAHXUCHER TRACHYTPORPHYR. (Germ.) J or earthy, and usu-
ally penetrated with firm veins or nests of harder texture.
Bereghasz in Hungary.

(d) VESICULAR or CAVERNOUS TRACHYTE-] The matrix contains
PORPHYRY, MILLSTONE PORPHYRY, (round vesicular cavi-

BLASIGER oder CAVI:IL\OSKK TRACHYTPOR- f ties, or 18 entirely pene-

PHYR, MUHLSTEINPORPHYR. (Germ.) J *

regularly shaped cavities, whose sides are sometimes partly
coated with cnalcedony or quartz.

These cavities, however, are never entirely filled, so as to
form genuine amygdaloids. Hliniker valley near Schemnitz.
(e) PUMICEOUS TRACHYTE-PORPHYRY. ) Forms a transition

BlMSTEDCAHNLICHER TRACHYTPORPHYR. (Germ.) J f rom the Vesicular

variety into pumice-stone.

( f) SLATY TRACHYTE-PORPHYRY. ) The slaty texture is pro-

SCHIEFRIGER TRACHYTPORPHYR. (Germ.) j duced by the manifold
alternation of their layers of somewhat differing composition.

Forchhammer has designated certain varieties of trachyte-porphyry
which occur in Iceland by the special names of Krablite and Baulite.
According to Bunsen, these are compounds of orthoclase and quartz.

All these varieties abound in certain trachyte regions, as, for in-
stance, in the neighbourhood of Schemnitz in Hungary, in the
Euganean Hills, on the Ponza Islands and the Lipari Islands. They
are usually irregularly cleft into angular masses, with columnar or
tabular jointed structure.

o 2

196 ACIDIC IGNEOUS ROCKS. (l) VOLCANIC.

References.

Beudant, Voyage en Hongrie, 1822, in many places.
Poulet Scrope, Ponza Islands, in Transact, of the Geol. Soc. [2]

vol. ii. p. 195.
AUch, Vulkanische Bildungen, 1849, p. 23. Vulkanische Er-

scheinungen, 1841, p. 20; Geol. N. d. armenischen Hoch-

landes, 1843, p. 44.

K. v. Hauer, Jahrbuch d. Geol. Keiclisanst. 1859, p. 466.
Forchhammerj in the Journ. f. prakt. Chemie, 1843, p. 390.
Bunseri, in Poggend. Annalen, 1851, vol. Ixxxiii. p. 201.

B. PEKLITE. Pearlstone, Pearlstone-porphyry.
PERLIT. (Germ.}
PERLITE. (Fr.}

An enamel-like matrix containing round grains, several
of which are constructed with concentric layers.

Spec. grav. . . . . .' . 2-32-4

Contains silica . . " . . . - 70 77 p. c.

The whole mass of the rock perlite is of the same com-
position as that of trachyte-porphyry, except that, on an
average, it is somewhat more rich in silica. The state,
however, of this compound, which is distinguished as
perlite, often alternates with the simple compact obsidian
state, or that other state which has become porphyritic
by the occurrence of sanidine crystals. It also forms
transition states into pumice-stone. Occasionally there
occur, in addition to the sanidine crystals, some small
mica flakes, red garnets, and even crystals of quartz.
According to texture, Beudant distinguishes the follow-
ing varieties :

(a) GRANULAR SHELLY PERLITE.

KORNIGSCHALIGER PERLIT. {Germ.)

TRACHYTE TESTACE. (Fr.)

(b) SPIUSRULITIC PERLITE. ^ with compact or radial striped

ICHER PERLIT. Germ.

SPHAROLITISCHER PERLIT. (Germ.)
PERLITE GLOBULAIRE. (Fr.)

PERLITPORPHYR. (Germ.)
PERLITE PORPHYROIDE. (Fr.)

(d) VITREOUS, WITH RESINOUS LUSTRE.

PECHSTEINARTIGKR PERLIT. (Germ.)

(e) ARGILLACEOUS PERLITE.

THONSTEINARTIGER PERLIT. (Germ.)

(/) PUMICEOUS PERLITE.

PERLTTBIMSTEIN. (Germ.)

All these varieties are found (for instance) in the trachytic regions
of Hungary, near Schemnitz, Tokay, Telkebanya, &c., near Zimapan
in Mexico, on the Lipari Islands, &c.

TRACHYTE GROUP. 197

References.

Beudant, Voyage en Hongrie, vol. ii. p. 363.
v. Pettko, in Haidinger's Abhandlungen, 1847, vol. i. p. 298 ;

and as to Schemnitz, in the Abhandlung. d. geol. Reichstanst.

1853, vol. ii. No. 1. He names the variety with felsite balls

' Spherolite rock.'

Erdmann, Journ. f. tech. Chemie, 1832, vol. xv. p. 38.
Delesse. Bullet, de la Soc. ge*ol. 1864, [2] vol. xi. p. 109 ; v. L.

u. Br. Jahrb. 1856, p. 195.

C. OBSIDIAN and PUMICE-STONE.

OBSIDIAN und BIMSTEIN. (Germ.}
OBSIDEENNE et PONCE. (Fr.)

Obsidian is a volcanic glass, sometimes porphyritic by
reason of sanidine crystals : this glass, however, when
it becomes vesicular, passes over into the most exquisite
foam-like pumice-stone.

Spec. grav. . ' . ' . . " . " . 2*3 2*5
Contains silica . , . , . . . 7182 p. c.

This glassy or frothy texture belongs only to the rocks
of the trachyte group, and more especially to the tra-
chyte-porphyries or rhyolites. Their colour is (in the
case of obsidian) usually dark black, brown, or greenish ;
in the case of pumice-stone, on the other hand, white or
yellowish-grey. According to differences of texture, we
may distinguish :

(a) COMMON OBSIDIAN. )

GEMEINER OBSIDIAN. (Germ.) \ A mere glass.

OBSIDIENNE COMMUNE uraotDE. (Fr.) )
(6) OBSIDIAN-PORPHYRY \ with sanidine crystals, or some-

OBSIDIANPORPHYR. (Germ.) [ t: mpa n l sn mi nlatps
OBSIDIENNE PORPHYROIDE. (Fr.) ) Umes al80 mica P lates -
(c) SPH^RULITIC OBSIDIAN. \ With felsite balls, passing

SPHAROLITISCHER OBSIDIAN. (Germ.) } nvpr intr nprlifp
OBSIDIENNB GLOBULAIRE. (Fr.) j over " to P er lte ' .

{This rock is often of
such long fibre and so
nnrniid that it will PVPTI
porous tnat it will even
float on water.

These species of volcanic glass are only found in trachytic volcanic
regions. They are very characteristically developed at the Peak of
Tenerifle, the Lipari Islands, in Iceland, in Mexico, &c.

References.

Beudard, Voyage en Hongrie, vol. iii. p. 389.
Erdmann, Journ. f. techn. Chem. 1832, vol. xv. p. 36.
K. v. Hauer, Jahrb. d. g. Reichsanst. 1854, p. 808.
Damour, Poggend. Ann. 1844, vol. Ixii. p. 287.

198 ACIDIC IGNEOUS EOCKS. (l) VOLCANIC.

Mundoch, Phil. Mag. and Journ. 1844, [2] vol. xxv. p. 495.
v. d. Boon-Meesch, Pogg. Ann. 1828, vol. xii. p. 616.
Herter, Perlstein. Zeitschr. d. deutschen geol. Gesellsch. vol. xv.
p. 459.

PHONOLITE GKOUP.

15. PHONOLITE, CLINKSTONE.

PHONOLITH, KLINGSTEIN, PORPHYKSCHIEFER. (Germ.)
PHONOLITHE. (Fr.}

A compact base or matrix, in its, fresh state dark
greenish-grey, showing here and there single cleavage
surfaces of a vitreous felspar. The mass is as a rule
somewhat slaty or schistose in texture, or of thinly
tabular jointed structure gives a clear sound when
struck by the hammer ; on weathering a sharply
defined white crust is formed.
Spec. grav. . . ..'.". 2-4 2'6

Contains silica . . , , , / 50 62 p. c.

Klaproth proposed the name of phonolite for this rock,
as having a more scientific air than that of klingstein,
previously in use, of which it is the translation, and
the new name has been very generally accepted. The
peculiar properties of the rock had long been recognised,
its difference from basalt, trachyte, felsite rock, &c., but its
exact ingredients had not been investigated. Gmelin first
drew attention to its analysis by muriatic acid, in which it
is partly soluble and partly insoluble. The soluble part was
considered to be a zeolitic substance, the latter a felspar,
and the whole was considered to be an intimately blended
compound of zeolite and felspar (sanidine).

By the more exact microscopic and chemical investi-
gations of later times, however, it has appeared that the
composition of the phonolite mass is not so simple, and is
in some part wholly different from what was supposed.
It is even questionable whether in its fresh state it con-
tains any zeolitic substance at all ; certain is it that the
nepheline crystals which both Breithaupt and Rose early
recognised in phonolite, as well as the mineral forming
part of the matrix which Rammelsberg also judged to be
nepheline, have frequently been mistaken for zeolite.

Gr. Jenzsch ventures to give the following as the mine-
ralogical composition of this rock, after investigating mi-
croscopically and chemically several very characteristic
phonolites of Bohemia :

PHOXOLITE GROUP. 199

Per cent.

Sanidine, estimated at 63-55

Nepheline, do 31-76

Hornblende (arvendsonite) . . . . 9-34

Titanite ,. > 3-67

Pyrites , . .* . . . 0'04

These proportional values must, of course, vary greatly
with locality.

As accessories, the following minerals occur, and are
sometimes distinctly to be recognised in the rock ; viz.
oligoclase, augite, magnetic iron-ore, olivine, hatiyne,
brown mica, leucite, and nosean ; the last two minerals
are the least frequent. It is possible that the zeolite
(natrolite) which sometimes fill^ the crevices of the rock
may also occur in the principal mass, but if so, it is
probably the result of decomposition.

In respect of the proportion of silica contained in pho-
nolite, we might equally well group it with the basic as
the acidic igneous rocks ; it forms one of the intermediate
links between the two. As it never contains quartz dis-
tinctly and separately developed, it might seem to be
more allied mineralogically to the basic rocks ; but geo-
logically its character is nearer that of the trachytes
than the basalts. Where it occurs together with the
latter, as is very frequently the case, it seems to play the
same part as the trachytes under similar circumstances.

Its small content of water (0-6 0*8 per cent.) appears
to be (at least in part) a secondary product, the result of a
commencing decomposition ; and in the same manner the
occurrence of many accessory minerals in the mass, more
especially those appearing in the clefts and vesicular
cavities.

Phonolite often acquires a porphyritic texture from the
prominence of distinct crystals of sanidine and acicular
hornblende. The most marked porphyritic varieties are
as a rule little slaty and somewhat decomposed. As de-
composition progresses, the crystals become more promi-
nent, and even the titanite then is frequently to be easily
recognised. Many phonolites are dark-spotted, or they
contain round grains of peculiar composition and colour ;
these, however, as in the case of basalt, appear chiefly to
arise from commencing decomposition. Many are en-
tirely decomposed (kaolinised), and show an earthy frac-

200 ACIDIC IGNEOUS KOCKS. (l) VOLCANIC.

ture, with a light colour. Whole mountains of phonolite
have, apparently at least, decayed in this manner, with
scarcely a trace of slaty texture remaining. Naumann calls
this variety Tr achy tic phonolite \ it is almost the only variety
in which vesicular and amygdaloidal texture is found ; it
never occurs in the fresh, dark, and slaty kinds. Jenzsch
is even of opinion that the apparent vesicular and amyg-
daloidal cavities of the phonolite are not genuine bubbles
of the original rock, but have arisen subsequently by a
kind of corrosive process of decay. This view certainly
agrees with the absence of cavities in the perfectly fresh
rock. Yet in some few phonolites are found very decided
vesicular cavities. These cavities, as also the clefts and
fissures, most usually contain zeolites ; especially apo-
phyllite, chabasite, comptonite, desmine, natrolite, anal-
cime, or calcspar and hyalite.

Varieties in Texture.

(a) COMMON PHONOLITE. ^ Dark-coloured, compact, schistose,

GEMEINER PHONOLITH. (tar.) > O r imperfect slaty cleavage, and
PHONO COMMUNE. (Fr.) ) ^ *

the hammer. Mileschauer in Bohemia; Milzburg on the Ehon
Mountain.

(6) PORPHYRITIC PHONOLITE. ) The same mass with dis-

PORPHYRARTIGER PHONOLITH. (Germ.) [ tinct crystals of hornblende,
PHONOLITHE PORPHYROIBE. (Fr.) J au ^ te / or sanidine . Aussi ^

and Jakuben, near Tetschen in Bohemia.

TRACHYTAHNLICHER PHONOLITH. (Germ.) j rough, of a rather light-
grey colour ; frequently porphyritic, geodic, or amygdaloidal. Aussig,
in JBohemia.

(d) SPOTTED PHONOLITE. ] Luschwitz. near Aussig. in Bo-

GEPLECKTER PHONOLITH. (Germ.) Y i^ arn : Q
PHONOLTTHE TACHETEE. (Fr.) ) L lld<

(e) VESICULAR PHONOLITE. j Blattendorf, nearHaida, in Bo-

BLASIGER PHONOLITH. (Germ.) \ V.Q:,,
PHONOUTHE VACUOLAIRE. (Fr.) ) "

(/) AMYGDALOIDAL PHONOLITE. ^ Marienberg, near Aus-

MANDELSTEINARTIGER PHONOLITH. (Germ.) [ -R^p,.,:,,
PHONOLITHE AMYGDALOIDE. (Fr.) } S1 ?? m -t>0&emia.

The slaty or schistose phonolites are those which are
most usually of tabular or columnar jointed structure.
Those which are not slaty are usually only irregularly
massive.

This rock forms isolated conical hills, even more per-
fectly than basalt, especially so in the Bohemian Mittel-
gebirge and in the Oberlausitz. Much more rarely does
it form great connected mountain ranges, and it is more

GEANITIC GROUP. (2) PLUTONIC. 201

rarely found in the form of dykes than basalt. On the
continent of Europe, phonolite is only known as of ter-
tiary or of still more recent origin, and never as a genuine
plutonic rock. It is, on the other hand, also unknown as
actual lava at active volcanoes, and from this it would
appear that its state must be more or less the result of
cooling under pressure or of transmutation. In favour of
the latter supposition (of transmutation) is the presence
of zeolite, which is, however, not a constant ingredient.

Lyell, in his Geology, has instanced the occurrence of a
phonolite of the Devonian period in Forfarshire. If this
be a genuine phonolite, it is the only recorded instance of
such being found of earlier than tertiary origin, but as
the notice is quite incidental, and has reference to a
different subject, and is moreover very brief, we can-
not, without further explanation, accept it as authority
in contravention of a law which otherwise appears uni-
versal.

References.

Gmelin, in Poggend. Ann. 1828, vol. xiv. p. 259.
Stntve, in Poggend. Ann. 1826, vol. vii. p. 348.
Meyer, in Poggend. Ann. 1839, vol. xlvii. p. 192.
Redtenbacher, in Poggend. Ann. 1839, vol. xlviii. p. 494.
Schill, in G. Leonhard's Beitr. z. miner. Kenntn. von Baden,

1854, vol. iii. p. 59.
Schmid, in Poggend. Ann. 1853, vol. Ixxxix. p. 295 ; v. L. u.

Br. Jahrb. 1856, p. 845.
Jenzsch, in the Zeitschr. d. d. geol. Ges. 1856, p. 167 ; and

Poggend. Ann. vol. xcix. p. 417.
v. Rath, in the Zeitschr. d. d. geol. Ges. 1856, p. 291, and 1860,

p. 29.
Enqelbach, in the Erl. z. geogn. Karte v. Hessen, Sect. Schotten,

1859, p. 45.
Fischer, Die Trachyte u. Phonolithe des Hohganes, v. L. Jahrb.

1862, p. 356.
Rammekburg, Analysen von Phonolithen, Zeitschr. der d. geol.

Ges. 1862, vol. xiv. p. 750.

v. Fritsch has lately set up a distinction between nepheline-
phonolite, nosean-phonolite, leucite-phonolite, and felspar-
phonolite, Neues Jahrb. fur Mineral. 1865, p. 663.

2. Plutonic.

Granite is the principal rock of the plutonic division of
the acidic igneous rocks, as trachyte is of the volcanic
division of the same rocks.

202 ACIDIC IGNEOUS ROCKS. (2) PLUTONIC.

The other plutonic rocks rich in silica may all be classed
with granite as subordinate varieties of the same com-
pound. The principal of these are quartz-porphyry,
felsite rock, and pitchstone, all of which may be almost
regarded but as different states of the same substance,
bearing somewhat the same relation to granite as the
rhyolites to the trachytic rocks. We therefore describe
them all as granitic igneous rocks, although the idea of
a granular texture is usually conveyed by the name of
granite.

In the composition of all these rocks, orthoclase, or an
orthoclastic substance, is predominant (frequently asso-
ciated with other felspars), and is combined with quartz,
mica, chlorite, talc, some hornblende, &c. ; never with
augite.

The various combinations of these mineral ingredients
give the following specially named rocks each with their
subordinate varieties.

1. Granite. A compound of felspar, quartz, and mica ;
granular, and sometimes also porphyritic, or other variety
of texture. The following are varieties in composition :
protogine, syenite-granite, schorl-granite, adularia-granite,
granitite, ferruginous granite, graphite-granite, beresite,
aplite.

2. Granitic porphyry and (so-called) syenitic porphyry.
A rock containing the same ingredients as granite. The
matrix is usually compact, enclosing distinct crystals or
grains of felspar, quartz, and mica, or chlorite.

3. Quartz-porphyry. A compact matrix of the same
chemical composition as granite, with separate individual
crystals of felspar and quartz.

4. Felsite rock, or petrosilex. The matrix of quartz-
porphyry without its crystals.

5. Pitchstone and pitchstone-porphyry. The same sub-
stance as the above in a vitreous state, sometimes with
crystals of felspar and quartz.

It may appear to be inconsistent to treat the four last-
mentioned rocks as distinct species, instead of mere varie-
ties of the same species, as in the case of the rhyolites in
the trachytic group. Our only reason for a different
treatment is, that in general they are capable of being
more easily distinguished from each other.

GRANITIC GROUP. 203

16. GRANITE.

GRANIT. {Germ.)
GRANITE. (Fr.)

A crystalline granular compound of felspar, quartz, and
mica. In certain varieties there occur chlorite, talc,
hornblende, and schorl.

Spec. grav. ...... 2-6 2-7

Contains silica 62 81 p. c.

The several mineral grains or particles are firmly knit
together by their crystalline surfaces, without any uniting
medium. They are of a size to be individually recognised,
but their size is very various, and the rock is accordingly
coarse-grained, fine-grained, or medium-grained. The so-
called giant granites have grains larger than a walnut,
other varieties not larger than mustard-seed. If the
grains are so small as to become indistinct, and the rock
assumes a compact texture, then it is no longer granite
according to the usual meaning of the term.

We shall treat of these compact states hereafter under
the names of felsite rock and petrosilex ; they form states
of transition between granite and other rocks.

The felspar is usually the predominant ingredient, and
the mica occupies the smallest place in granite.

The felspar is chiefly orthoclase, very often accompanied
by some oligoclase. Oligoclase alone has not yet been
observed with certainty. It is also uncertain if albite or
labradorite ever occur in the granitic compound.

The orthoclase is somewhat various ; it is usually the
common opaque species of yellowish-white or reddish
colour ; more rarely grey or greenish. At many places
(as, for instance, in the central chain of the Alps), it is
principally that transparent vitreous variety, frequently
split and cracked, which is termed adularia. The ortho-
clase of granite is most readily to be distinguished from
the oligoclase by its fresher state, its mother-of-pearl
lustre, and simple twin growth ; whereas the oligoclase is
somewhat of resinous lustre, and has delicate parallel
stria? arising from multiform twin growths, or it is more
decomposed, dull, paled in colour, or even transmuted
into a totally different substance resembling steatite.
Sometimes a thin coating of oligoclase is found incrusted
round the grains of orthoclase.

204 ACIDIC IGNEOUS ROCKS. (-2) PLUTONIC.

Orthoclase not only occurs as an ingredient in the
normal granitic compound, but sometimes prominently in
distinct twin crystals imbedded in the granitic mass, in
which case the rock is termed porphyritic granite. These
crystals are sometimes several inches long, and they enclose
particles of quartz and mica, so as to form inside the crystal
small kernels or parallel streaks of fine-grained granite. In
the granite of the Fichtelgebirge, very large twin crystals
of orthoclase are sometimes found broken, their several
parts lying imbedded close together, just as in the case
of the sanidine crystals of the Drachenfels trachyte.

The quartz in granite is seldom in the form of perfect
crystals ; it usually forms grains of irregular shape, or
masses grown in with the other mineral ingredients of the
granite, chiefly with the felspar. It is tolerably trans-
parent and colourless or white, dark-grey, vitreous, most
easily recognisable by its hardness. The granite of Rum-
burg in Bohemia contains a dark-blue variety of quartz.
It is remarkable that this, the most difficult of fusion of
all the ingredients of granite, is often found hemmed in
between the felspar and mica, and to have received impres-
sions from the felspar at least ; whence it follows that the
quartz must have solidified somewhat later than it.

The mica of granite occurs in the form of thin laminae
or small hexagonal plates, whose cleavage-planes lie in
various directions, and therefore do not occasion a foliated
texture. Sometimes they are clustered in small bunches ;
or sometimes long continuous rays of mica run through
the whole rock. Most usually it is potash-mica or mag-
nesia-mica ; sometimes margarodite ; or lithia-mica, white,
grey, brown, black, more rarely yellow or green in colour.
Occasionally different coloured micas occur in the same
rock, or a narrow border of white potash-mica envelopes
the dark magnesia mica. But it is often difficult accu-
rately to determine the species of mica in these thin laminae ;
the easiest test is generally the optical. It is worthy of
remark that potash-mica and tourmaline (schorl) appear
only to occur (as original products) in plutonic-igneous
or metamorphic rocks, and in plutonic dyke formations ;
never in volcanic rocks.

The ingredients which we consider as essential for
granite are nevertheless sometimes replaced by others.

GRANITIC GROUP. 20,5

This species of substitution occasions varieties in composi-
tion which will be more particularly described below. It
occurs especially with the mica, whose substitutes are, talc,
chlorite (in protogine), schorl (in schorl-granite), graphite
(in graphite-granite), micaceous iron (ferruginous granite).

Sometimes a fourth ingredient appears in local but
characteristic varieties of granite; e.g. hornblende (in
syenitic granite) or pyrites (in beresite).

The following minerals occasionally occur in granite,
but only as accessories ; viz., tourmaline, garnet (always in
the form of trapezohedra), andalusite, topaz, beryl, pinite,
apatite, fluorspar, pistacite, corundum, zircon, titanite,
gadolinite, orthite, pyrorthite, allanite, cordierite, magnetic
iron-ore, tin-ore, mispickel, molybdenite, and native gold.

We find many transitions from granite into other rocks.
These are partly occasioned by variations of composition,
and partly- by variations of texture. The accession of
talc, chorite, schorl, or hornblende to the granitic com-
pound occasions transitions into protogine, schorl rock, or
syenite. If the felspar of granite disappears, we obtain
gr lessen, or if the quartz disappears, mica-trap (minette),
or if the mica disappears, aplite, and a kind of granulite.
If the laminae of mica assume a parallel direction, then the
texture becomes foliated, and gneiss is the result. If the
matrix of a porphyritic granite becomes very fine-grained
to compact, then we have a transition to granitic porphyry ;
and if in that case the mica also disappears, then the rock
becomes quartz-porphyry. Finally, if the whole granitic
compound becomes very fine-grained to compact, then the
rock isfelstone.

Varieties in Texture.

(a) COMMON GRANITE. \ Coarse, medium, or fine-grained, pro-
GEMEiNERGRANrr.^rro.) f bably the most extensively diffused of

GBAKTTE COMMUN. (/*.) J ^ ^^ ^ j f ^ ^^ ^

very coarse, it is sometimes called giant granite. Trebendorf, near
Eger. Very fine-grained varieties, on the other hand, occur at
Kerbersdorf, near Eger, in Bohemia, at Welsau, near Redwitz, and
in the Vienna paving-stone.

(6) PORPHYRITIC GRANITE. \ The porphyritic texture is usually

GEBIROS-GRAIOT, r. Leonhard. I caused by large orthoclase crys-

G JS^RPHTRotoE. (Fr.) I tals, more rarely by quartz crys-

' tals. The principal mass is

granular. Carlsbad and Ellenbogen, Ochsenkopf and Gop-
fersgriin in the Fichtelgebirge, &c. As a subvariety of this
class, we may cite the rappakivi of Finland, the principal mass

206 ACIDIC IGNEOUS ROCKS. (2) PLUTONIC.

of which is usually much decomposed ; it encloses rounded masses
of red felspar often half an inch across, enclosed by orbicular
envelopes of green oligoclase a quarter of an inch in diameter.

GNEISSGRANIT. (Germ.) L a geological point of view, much of
GRANITE GNEISSIQUE. (Fr.) ) what ^tterly has been called red

gneiss (gneissite), and which appears to be eruptive, must be
here included. Perhaps some grey gneiss too.

(d) GRAPHIC GRANITE. j The orthoclase is altogether predomi-

SCHRIFTGRANIT. (Germ.) L nant in large crystals, and is penetrated
GRANJTEGRAPHIQUE.OPV.) * Iccording to a singular

PECHMATIT, Naumann.

(Germ.)
PEGMATITE, ffaily. (Fr.)

crystallographic law, so that in certain cleavage-planes it pro-
duces figures resembling writing. The mica (usually white) is
accumulated separately in groups. This remarkable variety
usually only forms subordinate masses or dykes of small extent
in the ordinary granite or in gneiss or mica-schist, but such
dykes' are very frequent, e. g. in the Schloitzbachthal, near
Tharand, in Saxony.

(e) PEGMATITE. \ This rock Naumann separates from the

graphic granite, and he understands by
it a variety, very coarsely and irregu-
> larly constituted, of orthoclase, quartz,
and silvery-white mica. It often contains tourmaline, and
occurs under the same conditions as the graphic granite, and
frequently together with it.

This seems the proper place for certain other granites of
irregular composition very rich in felspar. Some are traversed
by dark continuous rays of mica, in others the felspar assumes
a form resembling flowering stalks (Blumengranif).

In the granite of Ballybrack, near Dublin, the mica (Marga-
rodite) assumes this plumose form, occurring in branches of
Prince of Wales' feathers, one inch across and several inches
long. Jukes.

The granites of this class are all of very small extent, and

their particular character is probably owing to special circum-

stances. They all usually contain many accessory minerals, such

as albite, tourmaline, topaz, beryl, garnet, gadolinite, orthite, &c.

They are sometimes so imbedded between strata of crystalline

schist that they can scarcely be regarded as of eruptive origin.

(/) MIAROLITE. \ Is the name given by Fournet to

MIAROLITH. (Germ.) > a o-eodic granite, rich in oligoclase,

MIAROLITE, Fournet. (Fr.) J in " tlie nei | hbour h ood o f Lyons, and

at Baveno in the Alps.

The following are varieties in composition ; in them

we find many of the varieties in texture repeated.

(</) PROTOGINE. ] A granite which contains talc or chlorite

PROTOGIN. (Germ.) L or decomposed mica instead of the usual

pROTOGi*E,/ M rm*. (Fr.)] ^^ li{& yery extensively developed

in the Western Alps. In the Erzgebirge much of the granite
lying between Schneeberg and Eibenstock contains no mica, but
in its stead siskin-green talc, which combined with flesh-red
felspar and white quartz gives that rock a singular appearance.

GRANITIC GROUP. -207

(h) SYENITIC GRANITE, granite with hornblende. If the quartz and
mica gradually diminish and finally disappear from the granitic
compound, then the rock passes over into a syenite. Syenitic
granite is often porphyritic, owing to the presence of large
crystals of orthoclase. It is very abundant near Moritzburg
and Meissen, in Saxony. The greater part of what is usually
called syenite properly belongs to this class, especially those
syenites which contain quartz or mica as characteristic in-
gredients. But there is no definite boundary between syenitic
granite and syenite.

(i) SCHORLACEOUS GRANITE. } Granite with schorl in the place of mica,
ScHORLGRAxrr. (Germ.) L usually fine-grained, and forms veins in
LUXULUAMTE, Pitani. { Qther ^^ ^ for ' in8tance , near Hei-
delberg and near Predazzo in Tyrol (very characteristic) : the
latter is a compound of orthoclase, quartz, and schorl.

The name Luxullianite has been proposed by M. Pisani for a
porphyroidal granite, in which thfi~ mica is replaced by tour-
maline/ because it is found in the parish of Luxullian,' in Corn-
wall.

() ADULARIA GRANITE and ADTJLARIA PROTOGINE. > With adularia

ADULARGRANIT und ADULARPROTOGIN. (Germ.) I in the place of

the ordinary felspar ; very extensively developed in the Alps.

(1) GRANITITE. ' ) Is the name proposed by G. Rose for all

GRAxrnr. (Germ.) \ granites containing much oligoclase with

red orthoclase, quartz, blackish-green magnesia-mica in small

quantity, and no white mica. This rock forms the principal

material of the Riesen Gebirge; it occurs in the Brocken of

the Hartz Mountains, Brixen in the Tyrol, &c. In composition

it is identical with the mariolite of Foumet.

(m) RTJMBURG GRANITE. > With blue quartz, occurs at Rum-
RUMBURGER GRAuiT. (Germ.) \ burg in Bohemia, also at Pic Blanc
in the Monte Rosa chain,
(n) GRAPHITIC GRANITE. > With graphite in the place of mica,

GRAPHITGRANIT. (Germ.) \ e . g. near Passau, on the Danube.
(0) FERRUGINOUS GRANITE. ) With micaceous iron instead of the
EISKNGRAXIT. (Germ.) \ ordinary mica. Occurs at several places
in the Fichtelgebirge, also in iron-mines near Dossenheim in
the Odenwald.

(p) BERESITE. ) A granite containing pyrites and very little

BERESTT. (Germ.) \ niica ; forms considerable dykes in the clay-
slate near Beresowsk in the Ural. These dykes are themselves
traversed by quartz veins containing gold.

(q) APLITE or SEMI-GRANITE. ^ Is the name given to a variety

APLTT oder HALBGRANTT. (Germ.) } O f very subordinate extent,
consisting only of quartz and orthoclase, and therefore mine-
ralogically allied to granitite.

GREISEN might also be reckoned as a variety of granite without
felspar. It does actually pass over into granite. . Its special
geological character seems, however, to entitle it to be men-
tioned as a separate rock. (See post, No. 50.)

(r) TONALITE. ) The name given by Vom Rath to the

TONALTT, Foro Rath. (Germ.) I roc k which forms the principal mass

of the Adamello group of mountains in Southern Tyrol, and

208 ACIDIC IGNEOUS EOCKS. (2) PLUTONIC.

which has hitherto always been described as granite. It is a
crystalline granular compound of triclinic felspar with quartz,
magnesia-mica, and hornblende. The triclinic felspar belongs
to an entirely new species not yet named. The quartz forms
at least one-third of the whole mass. It contains as accessories,
orthoclase, orthite, titanite, and magnetic iron-ore. It contains
67 per cent, of silica. Many dark-coloured concretions are
contained in the rock. In Tyrol this rock has broken through
the mica-schist. (Zeitschr. d. deutsch. geol. Ges. 1864, p. 249.)

All the varieties of granite are most commonly of irre-
gularly massive or else of thick tabular jointed structure.
By weathering, elliptical bodies are sometimes formed
which fall off in concentric layers, the interior remaining
fresh and firm. Granite is often found in large blocks
and boulders on the surface of the ground.

Granite is unquestionably one of the most extensively
prevalent of rocks, and its mineral compound, which is
also that of gneiss, is without doubt the most important
and frequent of all the rock substances of the earth.
Moreover, we find granite in all regions of the globe
assume the same or analogous bedding in relation to
other rocks. It frequently occupies extensive tracts, and
sometimes forms the backbone of whole mountain re-
gions. It also frequently forms dykes, and these some-
times penetrate the larger granite masses (from which
they may be distinguished by their texture) ; sometimes
the crystalline schists or older sedimentary formations :
granite dykes having been exceptionally found as late as
the Jurassic formations, e. g. in the Alps. The greater
part of the granites accessible to observation appear,
however, to be older than the coal formation, and to be
of deep plutonic origin. These granitic dykes are occa-
sionally accompanied by so-called contact formations ;
such as friction breccias ; silicification of the neighbouring
rock ; chiastolite-schist ; nodular schist (see post, p. 257) ;
granulation of limestone, &c.

The usual bedding* of granite, and its relation to the
bedding of adjoining rocks, unmistakably prove its erup-
tive character, except, perhaps, in some special cases.
Some doubts, however, which deserve our notice, have
been raised as to its former state of igneous fusion.

* The term ' bedding ' applied to igneous rocks, especially to granitic
rocks, must be taken as equivalent to ' mode of occurrence ;' and l erup-
tive' as only meaning 'intrusive' or 'irruptive.' TRANSLATOR.

GEAXITIC GROUP. 209

These rest chiefly upon the fact of the quartz having
solidified later than the felspar and mica, and on the want
of distinct traces of the effect of heat on the rocks which
the granite appears to have broken through. These ob-
jections, it appears to us, may be satisfactorily answered
by supposing the granite always to have consolidated at
great depth, and under genuine plutonic influences, per-
haps even with the aid of water. The great resemblance
which granite bears to the trachytic rocks speaks, at all
events, for a similar process of formation for both.

That there are no new granites of volcanic origin is a
necessary consequence of the assumed fact that the granitic
compound can only have originated in the depths of the
earth. We must likewise assume that great periods have
elapsed in every instance from the time of the formation
of granite rocks before they have become exposed to view.
We may well assume that the trachytes represent the vol-
canic part of the same igneous formation which gave birth
to the granites.

The name of granite (according to Emmerling's Lehrb.
d. Mineralogie) was first applied to rocks by Tournefort
in the year 1698. But according to Breislack's Lehrb.
d. Geologic, it had been used by Caesalpinus as early as
1596. For a long time it was, doubtless, used to desig-
nate every coarse-grained compound rock. The meaning
of the term was first more definitely fixed by Werner.
It has from the first been felt to be a geological necessity
to group with granite many other rocks bearing a close
affinity to it, but it has always been no less difficult to say
where the line should be drawn.

In 1849, G. Hose proposed the following new division
and grouping of granitic rocks (see Zeitschr. d. d. geol.
Ges. p. 352) :-

1. Granite (proper), essentially consisting of orthoclase, white (potash-)

mica, black (magnesia-) mica, and oligoclase ; as accessories,
hornblende, orthite, titanite, apatite, and iron pyrites.

2. Granitite, essentially consisting of orthoclase, oligoclase, quartz,

and magnesia-mica ; as accessories, hornblende, orthite, zircon,
titanite, pyrites, chalcopyrite, and molybdenite.

Now as Rose himself subdivides his granite (proper) into
several varieties whose composition differs as much from each
other as granitite from granite, no sufficient reason appears for
this violent division and new nomenclature.

3. Syenite, essentially consisting of orthoclase, oligoclase, hornblende,

210 ACIDIC IGNEOUS EOCKS. (2) PLUTONIC.

magnesia-mica, and quartz ; as accessories, titanite, apatite,
magnetic iron-ore, &c.

The difference "between this and the granitite also consists in
the greater frequency of the hornblende, in its being named as
an essential instead of an accessory ingredient. This is our
syenitic granite. The genuine syenite of the Plauenschen-
Grund does not agree with this definition because it seldom
contains mica and, perhaps, contains no quartz at all. There-
fore Rose sets up varieties of composition differing, however,
more from each other than his syenite from granite.

4. Porphyry, essentially consisting of orthoclase, oligoclase, quartz,

and magnesia-mica; as accessories, cordierite, garnet, ortliite,
and pyrites, its essential difference from his granite or granitite
consisting only in texture.

Now, as oligoclase and mica entirely fail in many rocks which
Hose reckons as porphyries, he has been driven again to make
varieties which differ almost more from each other than his
porphyries from the other granitic rocks.

5. Syenitic Porphyry, with a matrix enclosing crystals of orthoclase,

oligoclase, magnesia-mica, and hornblende; as accessories,
garnet, nepheline, titanite, quartz, magnetic iron-ore, specular
iron, and pyrites.

This is a very different rock from that which has received
the name of syenitic porphyry ever since Werner's time. It is
our porphyrite, which as we have seen may be divided into (A)
a rock essentially felspathic, (B) containing felspar and horn-
blende, and (C) containing felspar and mica.

The literature respecting granite is, as we might ex-
pect, a very rich one we will only cite a few treatises
on the more special phenomena.

References.

G. Rose, On the Granitite of the Riesengebirge, Zeitschr. d. d.
geol. Ges. 1857, p. 513.

Cotta, On the Rumburg Granite with blue Quartz. Erlauter. z.
geogn. Karte v. Sachsen, 1839, No. 3, p. 14.

Four-net, On Miarolit, Mem. sur la Geol. des Alpes, part. 2, p. 24,
and Bullet, de la Soc.^ geol., [2] vol. ii. p. 495.

Sothlinkff, On Rappakivi a granite which,' however, often
contains no quartz, and then is very similar to mica-trap, v.
L. u. Br. Jahrb. 1840, p. 613.

v. Rosthorn and Canavd, On Albite-granite and Tourmalin-
granite in the Alps. v. L. u. Br. Jahrb. 1855, p. 584.

v. Richthofen, On Granitite, Tourmalin-granite, and Tourmalin-
syenite, Geogri. Beschr. von Siid-Tyrol, 1860, pp. 108 and
148.

Axel- Gadolin distinguished two kinds of granite dykes in the
gneiss of Ladoga Lake, viz. : older dykes, with albite from
two of more recent formation, containing much oligoclase.
Verhandl. der k. russ. mineral. Ges. zu Petersburg, 1857-8,
p. 85.

GRANITIC GROUP. 211

Svanberg comes to the conclusion from analysis that besides
orthoclase other orthoclastic felspars occur in granite. Journ.
f. prakt. Chem. 1844, vol. xxxi. p. 161.

I)('l<-sse distinguishes in the Vosges Mountains protogine from
'(iranite sye*nitique des Ballons.' Bullet.de la Soc. ge*ol.
1852, [2] vol. xi. p. 464.

Also, ' Granite des Ballons,' ' Granites des Vosges/ and
' Filons de Granite.' Ann. des Mines [5] vol. jii. p. 369.

On the Pegmatite with Tourmalin of Saint Etienne in the
Vosges. Ann. des Mines, 1849, [4] vol. xvi. On Pegmatite
of Ireland. Bullet, de la Soc. g(ol. 1853 [2] vol. x. p. 568.

Haw/hlon, Quart. Journ. Geol. Soc. 1856, vol. xii. p. 177 ;
and 1858, vol. xiv. p. 300. Address delivered before the
Geol. Soc. of Dublin, 1862.

.R. Scott, The Granites of Donegal. Journ. of the Geol. Soc.
of Dublin, vol. ix. p. 285.

Scheerer, Granite Tyrols. Jahrb.'f. Min. 1864, p. 385.

Sir W. E. Logan, Classification of Eruptive Rocks. Rep.
Geol. Surv. Canada to 1863, p. 645.

G. LconJiard distinguishes between older and newer granite
veins in the Heidelberg mountain granite. Gegend um
Heidelberg, 1844.

Bunsen, On Granite formation. Zeitschr. d. d. geol. Ges.
1861, p. 96.

C. Rothe, iiber die krystallinischen Gesteine des Ries. Jahrb.
fiir Mineralogie, 1863, p. 169, contains many new analyses
of granite.

v. Helmersen has described the Rappakivi of Finland, of which
the Alexander column of St. Petersburg is formed, as a por-
phyritic granite with a flesh-red felspar predominant.

n/8on treats of the supposed neptunic origin of granite in the
Edinb. New Philos. Journal, 1861, vol. xiv. p. 149.

Fuchs on the granite of the Ilartz in the Jahrb. fiir Mineralo-
gie, 1862, pp. 769, 807.

H. C. Sorby. On the Microscopical Structure of Mount Sorrel
Granite : Proc. Geol. and Polytech. Soc. W. Riding of
Yorksh., 1863-4, pp. 301-4. On "the Microscopical Structure
of Crystals, indicating the Origin of Minerals and Rocks :
Quart. Journ. Geol. Soc. 1858, vol. xiv. p. 453.

Sorby and (later) Zirkel have made interesting dis-
coveries by microscopic analysis of granites and several
other igneous rocks.

The quartz and the felspar of Granite are found to en-
close numerous very small vesicles filled with water and
air, and also many minute particles of glass. The quartz
also contains some very minute crystals of felspar. The mi-
croscopic structure of the Trachytes very closely resembles
that of the granites ; their compact matrix Zirkel recog-
nised as a compound of felspar and quartz. In the compact
mass of fresh Basalt he recognised a compound of felspar

p 2

212 ACIDIC IGNEOUS ROCKS. (2) PLUTONIC.

and magnetic iron-ore with very Mttle olivine, and traces
only of augite. The vitreous mass of Pitchstone resolved
itself under the microscope into a confused compound of
very delicate acicular crystals. The same thing with
Obsidian. Even the newest Lavas exhibited in their
mass very minute pores filled with water.

17. GRANITIC PORPHYRY and SYENITIC
PORPHYRY.

GKANITPORPHYR und SYENTTPORPHYR. (Germ.}
A compact or fine-grained felsitic base, enclosing crystals

or crystalline grains of felspar, quartz, and mica, or

chlorite.

Spec. grav. < . . Y , . . 2-6 27
Contains silica , . . . . 61 64 p. c.

The matrix is yellowish, brownish, or dark green.
When not quite compact, its material may be recognised
as consisting principally of felspar, combined with quartz,
mica, or chlorite in small proportion. The presence of
chlorite occasions transitions into porphyritic granite or
protogine ; but in distinguishing and naming these transi-
tion rocks, their geological relations must always, to some
extent, be taken into account.

The distinct crystals of felspar are very numerous in
this rock, and are usually of large size. They are for the
most part twin crystals of orthoclase, and these are often
coated with a different species of felspar, probably oligo-
clase, crystallographically combined (grown together) with
the orthoclase. There sometimes occur also separate and
smaller felspar crystals and grains ; these latter, as well as
the crust of the larger crystals, show delicate stripings,
and therefore both, probably, consist of oligoclase.

The quartz most usually forms small grains or crystals
of a smoke-grey colour, often, however, larger diplohe-
drons (which were formerly mistaken for double pyramids)
very distinct and prominent.

The dark mica usually only occurs in small delicate
flakes or thin hexagonal plates. If the rock contains
chlorite instead of mica, as in the variety termed syenitic
porphyry, the chlorite forms small dark green scaly grains,
or else it is intimately blended with the matrix, to which
it imparts a green colour.

GKANITIC GROUP. 213

The above-mentioned modifications give rise to several
varieties of the rock.

Varieties in Texture.

(a) COMMON GRANITE-PORPHYRY. The matrix is compact through-

out ; often dark-coloured. It contains separate crystals, grains,
or laminae of orthoclase (and sometimes oligoclase), quartz,
and mica. If the mica faiis ; the rock passes into ordinary
quartz-porphyry. Frequent in the Thuringian Forest, e.g.
near Schmiedefeld, and in the Drusenthal, where it forms dykes
of great thickness.

(b) GRANITIC GRANITE-PORPHYRY. i The matrix resembles

GiiAxn-AHNLicHER GRANITPORPHYK. (Germ.) I" j n part a fine-grained
granite, but distinct crystals of orthoclase, and large grains of
quartz, and also laminae of mica, are separately and prominently
developed. Frequent in the neighbourhood of Schellerhau and
Biirenburg in the Erzgebirge. The composition of this rock is
very similar to that of porphyritic granite. The geological
character in these doubtful cases should determine the nomen-
clature of each particular rock.

At Niederschona, near Freiberg, where a rock belonging to
this class forms a vein in gneiss, it contains large light-
coloured twin crystals of orthoclase, whose exterior appears fresh,
but inside each crystal is a decomposed nucleus frequently
changed into a greenish substance like lithomarge. It would
almost seem as if the nucleus of the orthoclase crystal had
originally consisted of oligoclase or a compound of oligoclase
and quartz. The magnificent columnar granite-porphyry of
Altenhain, near Frankenberg, in the Erzgebirge, is a rock of the
same class, but the orthoclase crystals do not exhibit the same
phenomenon as those of Niederschona.

Near Liebenstein in the Thuringian Forest, a granitic
porphyry traverses and forms dykes in the ordinary granite.
It possesses a very fine granitic matrix, and very distinct
white crystals of orthoclase, with brown edges ; also dark spots
or fragments (which are still compact) of greenstone which
the porphyry has broken through.

GUMMERREICHER GRANTTPORPHYR. (Germ.) } tel first described under
the name of granitic porphyry, and which occurs at Aschaffen-
burg, interposed between syenite rocks, consists of a fine-grained
to compact felsitic mass rich in mica (a kind of minette) in
which numerous grains or crystals of quartz and somewhat
fewer, but much larger crystals of felspar are imbedded.
According to Kittel, the quartz crystals often show prismatic
surfaces. The orthoclase crystals are partly single, partly
twins, very fresh, without marginal crust, and have well-defined
edges, but strange to say, completely rounded off, so that their
cross-section always appears elliptical.

(d) CHLORITIC GRANITE-PORPHYRY. \ Often called syenitic por-

GRANrmjRpHYR. (Germ.) ) phyry, probably because

214 ACIDIC IGNEOUS ROCKS. (2) PLUTONIC.

the. particles of chlorite which it contains have been mis-
taken for hornblende ; but in some places the rock appears
actually to contain some hornblende as an accessory. The
matrix is compact or fine-grained, .brown or dark green,
often very rich in quartz, and contains chlorite, and some-
times mica also. The chlorite forms little flakes or grains,
the quartz is in the form of diplohedrons, and the twin
crystals of orthoclase are sometimes more than an inch long.
In the syenitic porphyries of the Erzgebirge (the rocks ori-
ginally so named by Werner) these orthoclase crystals are often
enveloped in an outer coating of oligoclase, of about one-tenth
of an inch thick, showing distinct twin stripings. The oli-
goclase is sometimes lighter in colour than the orthoclase
(greenish-yellow) sometimes darker (brown), and it is gene-
rally more decomposed than it. This rock near Frauenstein
and Altenberg has broken through gneiss, mica-schist, granite,
and quartz-porphyry, and forms very important and extensive
dykes in those rocks many miles in length. Near Frauenstein
it contains, according to Rube, about 64 p. c. of silica.

Naumann has described a rock of somewhat different cha-
racter under the name of green porphyry. It occurs in the
neighbourhood of Wurzen in Saxony, where it forms small
rocky hills. Its matrix is dark-green, probably from chlorite,
and it also contains some magnetic iron-ore.

Dr. Rube determined its proportion of silica at about 61 p. c.
This rock is likewise more recent than the quartz-porphyry of
the same district.

(<?) THE BASE or MOTHER ROCK of these Porphyries occasionally
occurs free from crystals (towards the outer margin of the
rock), and it then assumes very much the character of a fine-
grained granite, poor in mica and rich in chlorite.

All the above-named varieties are most usually massive,
but sometimes of columnar-jointed structure. They form
great mountain masses or thick dykes. There are no
vesicular or amygdaloidal varieties, or tufa formations of
rocks belonging to this group.

References.

Zirkel, Geogn. Verh. d. Umg. von Aschaflfenburg, 1840, p. 30.
Naumann. Erlauter. zur geogn. Karte von Sachsen, 1836, No. 1,
p. 139.

18. QUARTZ-POKPHYKY, ELVANITE.

QUARZPORPHYR. (Germ.}

PORPHYRE QUARTZIFERE, ELVAN". (Fr.)

A compact felsitic mass as matrix, enclosing crystals or
crystalline grains of felspar and quartz.

Spec, grav 2 -5 2 -6

Contains silica ..... 70 81 p. c.

GRANITIC GROUP. 215

The compact matrix of the quartz- porphyries consists
principally, if not altogether, of felspar ; this is sufficiently
proved by its hardness, weight, colour, as well as by
chemical analysis; and from its compactness, its large
proportion of silica and the crystals of orthoclase which are
imbedded in it, we conclude that it most probably consists
of orthoclase. Its proportion of silica is, however, too high
even for orthoclase, and it is therefore probable that some
quartz is intimately combined with the felspar. If this
be the case, it would not alter the fusibility of the rock
before the blowpipe. An intimate compound of felspar
and quartz melts almost as readily as felspar alone. The
colour of the matrix generally varies between yellowish
and reddish, but sometimes goes over into brown and
grey, and even to white. Exceptionally, also, violet and
green varieties occur.

The state or texture of the matrix varies somewhat,
and the differences are partly original, partly occasioned
by decomposition and weathering. Sometimes it is quite
compact like hornstone, with a smooth conchoidal frac-
ture ; most usually it is compact with uneven dull fracture,
which appears to be the sign of transition towards a crys-
talline state ; finally, it is sometimes rough and dull,
almost earthy, which is a sign of commencing decompo-
sition (kaolinising of the felspar). Owing to these dif-
ferences of texture or state, the substance of the rock
itself was formerly regarded as varying essentially, and it
has been so described, whence the names of hornstone-
porphyry, felstone-porphyry, and clay stone-porphyry, or
even clay-porphyry. The differences, no doubt, exist,
but they are only of a different arrangement of particles,
or of decomposition of one and the same substance. This
matrix of the quartz-porphyries, which sometimes occurs
as a separate rock without crystals, has received separate
names, such zsfelsite or felsite rock, eurite, petrosilex, and
halleflinta, hence also the names of felsite-pcrphyry and
curite-porphyry. It is seldom or never of vesicular or
amygdaloidal texture.

In genuine quartz-porphyry, felspar and quartz are
the only crystals which are porphyritically developed.
If mica or chlorite occur in addition they constitute a
transition into granitic porphyry. The felspar is usually

216 ACIDIC IGNEOUS KOCKS. (2) PLUTONIC.

orthoclase, and from its twin growth is usually very dis-
tinctly to be recognised ; sometimes, also, oligoclase or
sanidine occur. All these felspars where they occur por-
phyritically are very distinctly and sharply developed,
and are easily distinguished from the matrix.

The crystals of quartz are white, grey, or almost black,
but withal frequently transparent ; they are small, seldom
larger than the size of a pea; they form either sharp-
edged diplohedrons (without a trace of prismatic surface),
or they are more or less rounded off at the edges and
angles, or finally they form mere rounded grains without
crystal surfaces. The rounding of these crystals is some-
times so remarkable that it has given rise to the idea of
their having been actually rounded by friction, which in
genuine porphyries can hardly be the case. The number
and proportion of the quartz crystals contained in the
matrix, as also that of the felspar crystals, is very variable,
and sometimes diminishes even to total disappearance, so
that transitions take place into the quartzless-porphyrite or
into felsite rock ; but quartz-porphyry, although poor in
quartz, is nevertheless always to be distinguished from
genuine porphyrite by its far greater proportion of silica.
The quartz-porphyries on an average have more silica
even than the granite, just as the rhyolitic division of the
trachytes contains more silica than the trachytic. There
is scarcely any petrographic difference between many
quartz-porphyries (especially if they contain sanidine or
oligoclase) and some kinds of trachyte-porphyry. They
are sometimes so much alike as not to be distinguished
from each other in ordinary hand specimens. In such
cases the character of a given rock can only be determined
geologically, and ascribed to the granitic or the trachytic
group respectively, according as it occurs in a granite or
trachyte district, or from its relation to some rock of more
distinct character to which it may be traced by transitions.

Smaller crystals or particles of quartz, but large enough
to be discovered by the eye or with an ordinary lens, are
often interspersed in the matrix between the larger and
more distinct crystals of this rock.

The quartz-porphyries seldom contain any accessory
ingredients properly so called, and where such do occur
they are probably only of secondary origin, products of

GRANITIC GROUP. 217

transformation, or new formation ; thus, for instance, pinite,
talc, lithomarge, chlorite, pinguite, pyrites, and specular
iron. But in veins or in clefts, nests or concretions in
the rock, many minerals are frequently found, such for
instance as quartz, hornstone, chalcedony, agate, opal,
lithomarge, calc-spar, brown-spar, fluor-spar, barytes,
specular iron, and dendritic pencilling^ of oxides of iron
and manganese all which appear to be secondary for-
mations caused by secretion from the rock's mass, or by
infiltrated solutions.

The porphyritic texture of the rock is sometimes united
witli a fissile or fine laminated structure (riband-porphyry,
band-porphyry) ; also sometimes- with geodic structure
(millstone-porphyry), or else with spotted texture or there
lie dispersed through the rock's mass smaller or larger
felsite balls (pyromeride).

Varieties in Texture.
(a) COMMON QUARTZ-PORPHYRY. \ with compact ma trix and

( : KM KIXER QUARZPOUPHYR. (Germ.) I 1 _ rai . p i fl n f fplqnnr onH niinrfy

PORPHYKE QUARTZIKEHE coMMux. (/v.) ) crystals oi .ispar ana quartz.
() Hornstone-porphyry (Homsteiuporphyr, Germ.\ Elvan,

(j3) Felstone-porphyry (Feldsteinporphyr, Germ, j Pe*trosilex,

JFK).
(y) Clay stone-porphyry or Argittophry (Thonsteinporphyr

oder Thonporphyr, Germ. ; Argtlophyre, Fr.).
All frequent, in the Thuringian Forest and near

Meissen, and near Tharand in Saxony.

(6) STRIPED PORPHYRY (SLATY
PORPHYRY).

SCHIEFRIGER PORPHYR, SCHALEX-

oder BAXDPORPUYR. (Germ.)
PETROSILEX RUBANE. (Fr.)

Composed of thin layers of
somewhat dissimilar texture or
colour; hence the fracture ap-
pears to be striped like a riband,
and the rock splits more easily

in the direction of the layers than straight across. The layers

are often much bent and twisted. Mohorn near Freiherg ;

Winterstein in the Thuringian Forest, Wachenberg in the Oden-

wald.

FLECKENPORPHYR. (Germ.) > ferent colour and texture from the
matrix. This variety has also been called Kattun-porphyry.
Leukersdorf near Chemnitz, Saxony.

(d) POROUS, CAVERNOUS, OR ] A rock penetrated by numerous

MILLSTONE PORPHYRY. I small irregular cavities or geodes,
POROSER, DRUSIGER, oderMt^Hi^ f which are seldom vesicular, more

STEINPORPHYR. (Germ.) ) usuftlly the regult of weathering>

Tannebergsthal in the Erzgebirge, Regenberg near Frie-
drichsroda, in the Thuringian Forest, where it is combined with
pyromeride.

218 ACIDIC IGNEOUS ROCKS. (2) PLUTONIC.

This rock in addition to the
usual quartz crystals, contains
balls of felsite (either small

(e) PYROMERIDE (BALL-PORPHYRY).'

KUGELPORPHYR oder PYROMERID.

(Germ.)
PYROMERIDE, Monteiro. (Fr.)

' and numerous, or large and

isolated. The small balls are frequently marked internally
with radial streaks. The interiors of the larger ones are usually
split after the manner of septaria, or they contain a geodic
cavity. The clefts or cavities in the balls are wholly or
partly filled with hornstone, chalcedony, agate, quartz, ame-
thyst, calc-spar, fluor-spar, micaceous iron, &c. These balls, as
we have already mentioned, frequently occur in combination
with a geodic structure of the matrix. Regenberg and Schnee-
kopf in the Thuringian Forest, the island of Corsica.
(/) PORPHYRY WITH ] Forms a transition into felsite rock
FEW CRYSTALS. I (petrosilex) or into porphyrite. The
KRYSTALLARMER POR- f matrix alone, without crystals, is some-
CYR. (Germ.) ) timeg foimd towar( J s tne o uter mar gi n o f

masses of very distinct quartz-porphyries thus e.g. at the
Weissritz, close above Dippoldiswalde in Saxony, The Frei-
berg porphyry dykes are also mostly very poor in crystals of
felspar and quartz, but they often contain, in their stead, small
cubic crystals of pyrites.

Varieties in Composition.

(</) ORTHOCLASE-QTJARTZ-PORPHYRY. ^With orthoclase and quartz
ORTHOKLAS-QUARZPORPHYR. (Germ.) f crystals only very frequent.

(A) OLIGOCLASE-QTTARTZ-PORPHYRY. ^ The rock contains crystals of
OLIGOKLAS-QUARZPORPHYR. (Germ.) \ oligoclase in addition to the
orthoclase and the quartz. The oligoclase is distinguishable by
its twin stripings, its different colour, or more advanced decom-
position. Under this head we include, for instance, the brown
porphyry of Manebach, in the Thuringian Forest, with its
distinct orthoclase twin crystals of an inch long, containing, in
addition to these, numerous smaller crystals of oligoclase, much
decomposed. Frequently the oligoclase is transformed into a
yellowish-green substance resembling steatite. Hermsdorf and
Schonfeld in the Erzgebirge.

Von Richthofen discovered certain porphyries at the Trost-
burg and Monte Bocche, near Botzen in Tyrol, which, in addition
to their quartz, only contain crystals of oligoclase, and (usually)
some black mica, in a dark matrix. In the same neighbour-
hood some porphyries contain quartz and orthoclase alone
(at Bronzell and Pelegrin) ; others quartz, orthoclase, and some
oligoclase (Castelruth, Blumau, Hoch-Eppen). Perhaps the
beautiful brown porphyries of Lehnau near Kemnath, and of
Kronberg near Erbendorf, are rocks containing oligoclase only.
Their felspar crystals are all decomposed, although the matrix
is unusually fresh.

(i) SANIDINE-QUARTZ-PORPHYRY. ) Is a name given by Jenzsch to a

SANIDIN-QUARZPORPHYR. (Germ.) } variety occurring at Zwickau in

Saxony, containing sanidine and quartz. To the west of Oederan

GRANITIC GROUP. 219

near Freiberg, there occurs a porphyry containing crystals of
orthoclase, sanidine, and quartz.

It would be impossible to instance here all local differences,
many of which only result from transmutation, or are to be re-
garded but as accessory phenomena. Of this kind is the change of
the felspar crystals into a greenish substance resembling steatite,
occurring in a quartz-porphyry rock at theRaubschlb'sschen, near
Weinheim. Again, in a porphyry of Manebach, near Ilmenau,
rich in orthoclase, all the quartz crystals are encrusted with a

greenish-blue coating, probably containing copper ; and in the
gold-containing porphyry of Csetatye in Transylvania, the
large diplohedrons of quartz are very much rounded oft) and the

Quartz-porphyries are usually much rent by fissures,
but sometimes are found of very regular columnar or
of tabular-jointed structure. Tihey are probably never
gnarled or irregularly spherical. They sometimes occupy
connected regions of great extent, but in that case are by
no means of uniform structure, consisting usually of many
different varieties which penetrate and traverse each other
in all directions, as in the Thuringian Forest, and near
Botzen. They sometimes again form isolated dykes in
granite, gneiss, &c., as near Freiberg. It is very rarely
that they are found to have penetrated any more recent
formations than the Devonian or Silurian. In Walden-
burg in Silesia, however, they traverse the coal formations,
and in the Thuringian Forest the Rothliegende, but these
are exceptional cases. Their comportment in this respect
is similar to that of granite, and with the difference of
their containing throughout a somewhat higher proportion
of silica, they would appear to represent but the porphy-
ritic state of that rock, since they actually contain the
elements of mica in small quantity. The compact state
of their principal mass may to some extent be owing to
their greater quantity of silica, but in all probability chiefly
to their having originally cooled down more rapidly than
granite, as is more especially likely to have been the case
with the frequent isolated dykes and small masses of this
rock. Quartz-porphyry as a rule, when found with granite,
is more recent than the latter, bearing much the same
relation to it as the trachyte-porphyries to the trachytes.
Thus in Cornwall we find the quartz-porphyry or elvanite
to have broken through the granite, and to form dykes or
veins in that rock.

220 ACIDIC IGNEOUS ROCKS. (2) PLUTONIC.

References.

G. Leonhard, Die quarzfiihrenden Porphyre, 1851.

Naumann in the 5th No. of the Erlauter. zur geogn. Karte
von Sachsen, 1845.

Laspeyres on careful microscopic examination of the quartz-
porphyries of Halle found the compact base to consist of
felspar, quartz, and some mica. The crystals of felspar, ac-
cording to him, had originally been sanidine, and are only
in part transmuted to orthoclase. Zeitschr. d. deut. geol.
Ges. vol. xvi. p. 867.

Delesse, Porphyry from Lescines in Belgium, Bullet, de la Soc.
Ge'ol. 1850 [21 vol. vii. p. 310.

Jenzsch, on Sanidine-quartz-porphyry, Zeitschr. d. d. geol. Ges.
1858, p. 49.

v. Richthofen in the Zeitschr. d. d. geol. Ges. 1826, vol. viii.
p. 644; v. L. u. Br. Jahrb. 1859, p. 312 ; and geogn. Beschr.
von Siid-Tyrol, 1860, p. 112.

Hochmuth, the Porphyries of Halle in the Bergwerksfreund,
1847, vol. xi. p. 450.

Streng in v. L. u. Br. Jahrb. 1860, pp. 129 and 257.

H. Vogelsang on the Pyromerides of Corsica (Berggeist), 1862,
NOB. 90 and 19 ; Jahrb. fur Mineralogie, 1863, p. 102.

19. FELSTONE, FELSITE-ROCK AND FEL-
SITE-SCHIST, PETKOSILEX,*EURITE, HAL-
LEFLINTA.

FELSTTFELS TJND FELSITSCHIEFER. (Germ.)
A rock of compact texture, about the hardness of felspar,
with dull or smooth conchoidal or fissile fracture ;
colour yellowish, reddish, grey, greenish, or bluish,
weathering white.

Spec, grav 2-52-7

Contains silica . . . . 7181 p. c.

Gerhard was the first to discover that this rock, which
we have already noticed as being identical with the ma-
trix of the quartz-porphyries, consists chiefly of felspar,
and he accordingly gave it the name of felsite. Some
years later, Dolomieu surmised that it contained the
essential ingredients of granite in a compact state, and

* The name of petrosilex was first proposed by Brongniart, who
applied it to felsite rocks, believing them to be identical with horn-
stone. The name has stuck to these rocks in spite of the original
error, and cannot well now be ignored. Some authors, wishing pro-
bably to correct the original misconception, have, however, applied
the name of petrosilex to hornstone, but this is simply to create un-
necessary confusion better drop the name altogether. TKANSLATOE.

GRANITIC GROUP. 221

Daubisson proved it to consist of an intimate compound
of felspar and quartz, and gave it the name eurite on ac-
count of its fusibility. The same substance has also re-
ceived the names of petrosilex, and in Scandinavia halle-
jlinta, which are of earlier date than the names of felsite
and felstone. All the later analyses of this rock have
confirmed the fact that it contains both felspar and quartz,
and besides these the elementary ingredients of some mica.

In 1845, Durocher showed, by comparing the various
analyses, that felstone, or petrosilex, is of the average
chemical composition of granite, even quantitatively ; and
it may therefore be regarded as a granite in compact
state, something in the same way as basalt and aphanite
respectively represent the compact states of the dolerites
and the granular greenstones. Now, this fact is of im-
portance with respect to the process of granite forma-
tions, since we know that felsite rock, although it contains
quartz, is as easily fusible as felspar alone. For we gather
from it that the quartz of granite, when in combination
with its other ingredients, might remain in a fluid state
quite as long as the felspar and mica, so that the process
of crystallisation of all might be contemporaneous, and it
would then depend on the individual crystallizing force
of each, which mineral would first develop its form.
Quartz-porphyry, granitic-porphyry, and granite, with all
their several varieties, are therefore products of essentially
the same mineral dough, and probably they only differ by
reason of slower or more rapid cooling or slight variations
in the proportion of the several ingredients. That this
igneous compound has most usually resulted in granite,
especially in great connected regions of its development,
probably proceeds from the fact of deep plutonic solidifi-
cation ; or we may reverse the proposition and say, that
wherever this igneous mass attained the solid state deep
in the interior of the earth, granite, or a granitic rock,
has been the result ; on the other hand, when it became
solid at or nearer to the earth's surface, then trachyte
(rhyolite) and trachy tic lavas were its products.

Felstone may be divided into two principal varieties,
the massive and the schistose. It goes over on the one
hand very frequently into quartz-porphyry, or less usu-
ally into granitic porphyry ; and on the other, it is con-

222 ACIDIC IGNEOUS ROCKS. (2) PLUTONIC.

nected by stages of transition with granulite and gneiss.
The rock called Werner ite we reckon to the first of these
two divisions : it has the character of an eruptive rock,
whilst the foliated varieties of felsite are more closely
connected with the metamorphic crystalline schists, and
may be regarded as compact granulite or gneiss.

Varieties.

(a) FELSTOKE PROPER, orj Not fissile, usually of massive jointed
PETROSILEX. I structure, or very much divided by

PETROSILEX. (Germ.) f clefts and fissures. It is frequently
PETROSILEX, Dolomieu. J found continuous with porphyry, but

sometimes forming independent dykes

in the same way as porphyry. Dippoldiswalde in Saxony,
Bellmannsloos, near Tharand.

(6) ' WERNERITE ROCK. \ Is the name given by Jasche to a
WERXERITFELS. (Germ.) ( compact compound of common felspar
SKAPOLIT-FELS. (Fr.) J and scapolite ( wern erite), with acces-
sory admixtures of graphite, magnetic pyrites, and iron pyrites.
It traverses the ironstone beds of Buchenberg at the Hartz.
A similar rock, according to Axel Gadolin, occurs on tlie island
of Pusu in the Ladoga Lake.

(c) HALLEFLISTTA, or FELSITE-SCHIST. ] Foliated or unevenly lami-
HALLEFLINTA, oder FELSITSCHIEFER. f nated. Sometimes contains
HAiiEFKtNTA. (Fr.) j an admixture of chlorite in-

* timately blended in its mass,

and occasionally some mica. This rock is almost always found
in parallel bedding with granulite or gneiss, into which it
goes over by transition states. It is most frequently found in
Sweden, and therefore, for the most part, should be con-
sidered as belonging to the metamorphic schistous rocks, but it
is not always possible distinctly to separate its different forms
of development according to origin.

The schistous as well as the massive varieties of felstone are
very frequent among some of the older formations in the British
Islands, making up whole mountain masses.

It is most probable that the felsitic matrix of the quartz-
containing porphyries of the granite group, is somewhat
different in composition from that of the porphyrites which
are free from quartz. The former will always contain
more silica than that of the porphyrite, and its felsitic
constituent will partake of the nature of orthoclase. This
is our petrosilex. To outward appearance this difference
is often scarcely appreciable, although the matrix of the
porphyrites is usually (not always) darker in colour than
that of the quartz-porphyries and granitic porphyries.

GKAXITIC GROUP. 223

References.

Gerhard, Abhandl. d. k. Akad. d. Wissensch. zu Berlin, 1814

and 1816, p. 12.

Daubimson, Traite* de Ge*ognosie, 1st ed. 1819, vol. i. p. 112.
Ditrocher, Compt. rend. 1845, vol. xx. p. 1277.
Schweitzer, in Poggend. Ann. 1840, vol. li. p. 287.
Kersten, in Poggend. Ann. 1843, vol. liii. p.^130.
Wolff, Journ. f. prakt. Chemie, vol. xxxiv. p. 193, and vol.

xxxvi. p. 412.

Svanberp, Vet. Akad. Handl. 1850, p. 9.
fftuiffhton, Journ. of the Geol. Soc. of Dublin, 1857, [7] p. 283;

and Phil. Mag. 1857, [4] vol. xiv. p. 49.

Jasche, on Wernerite rock, Mineralogische Studien, 1838, p. 4.
A. Gadolin, on Wernerite rock, in the Verh. d. k. Kuss. mineral.

Ges. at St. Petersburg, 1857-58, p. 85.

20. PITCHSTONE and PITCHSTONE-POR-
PHYRY.

PECHSTEIN und PECHSTEINPORPHYR. (Germ.)
REUNITE. (Fr.)

The principal mass is homogeneous ; of vitreous pitch-
like appearance; conchoidal fracture ; resinous lustre,
translucent at the edges ; very variously coloured, viz.,
yelloiv, red, brown, black, and green; it sometimes
encloses (porphyritically) small crystals of vitreous
felspar, grains of quartz, and lamina of mica ; fre-
quently also halls offelsite.

Spec. grav. 2-22-3

Contains silica 63 75 p. c.

Pitchstone is evidently to be regarded only as a vitre-
ous state of felsite rock, quartz-porphyry, or granite its
chemical composition being essentially the same as that of
these rocks, except that it contains more water than they,
sometimes as much as 6 p. c. This may be one cause
of its vitreous state. Its colour is dependent on the rela-
tive proportions which it contains of the peroxide or the
protoxide of iron and protoxide of manganese. The first
of these gives the rock a red or yellow colour, the latter
green, grey, and black. In spite of its large proportion
of silica, thin splinters of pitchstone melt easily before
the blowpipe to a white vesicular glass without intumes-
cence. Formerly pitchstone was regarded as an inde-
pendent mineral, but it is clearly nothing but a close
compound of felspar and quartz, with which the elements

224 ACIDIC IGNEOUS ROCKS. (2) PLUTONIC.

of mica are also combined. Recently it has been even
doubted whether this compound is really an amorphous
vitreous mass, or only a very intimately blended crystal-
line aggregate. It may be that this opinion has arisen
from some few fine crystalline particles which swim in the
prevailing vitreous mass.

Crystals of sanidine are sometimes found porphyritically
imbedded in the rock ; they are small, but usually quite
fresh, and are frequently coated with a thin light-red
crust, evidently caused by oxide of iron ; grains of quartz
and laminae of mica are also found, but more rarely, and
are often similarly coated. Instead of these crystals, or
in addition to them, there also very frequently occur
nodules or balls of felsite, very various in size and struc-
ture. In the pitchstone-porphyry at Spechtshausen, near
Tharand in Saxony, such are found varying from one-tenth
of an inch to six inches diameter, consisting of compact
felsite, and some of the very small balls of shining sani-
dine. The larger ones occasionally contain veins of chal-
cedony in their interior ; the grey pitchstone of Planitz,
near Zwickau, contains balls of from one to five inches
diameter veined inside in the manner of septaria, the
veins narrowing towards the periphery and filled with
chalcedony and quartz. At the Fichtenmiihle, near
Meissen, a yellowish-brown pitchstone contains irregular
nodules, whose size extends even to ten feet diameter,
consisting of quartz-porphyry, with a matrix resembling
hornstone. It would almost seem as if these were frag-
ments torn from the adjoining quartz-porphyry (which is
here traversed and disturbed by the pitchstone) and then
rounded off in the convulsion. Near Corbitz, in the
neighbourhood of Meissen, there is a pitchstone rock very
much weathered, containing nodules from a quarter to
three feet diameter ; these nodules consist of a compact
felsitic mass, which itself contains other more compact and
dark-coloured ball-shaped concretions of the same sub-
stance. Similar phenomena with many modifications re-
peatedly occur in the pitchstone of other localities. These
nodules appear to answer to those in the pearlstone (sphe-
rulites), which are smaller in size ; they are frequently
coated with a deep-red crust or their surfaces much
weathered.

GRANITIC GROUP. 225

The pitchstone of Planitz in Saxony is found to contain
in some places small fragments of (so-called) mineral
charcoal (a coal of woody texture without bitumen, and
containing much silica) which indicate that the pitchstone
has broken through the coal formation of that district.

Scarcely any other minerals than those we have named
are known to be similarly enclosed in pitchstone.

This rock passes over into obsidian and pearlstone.
By decomposition it becomes a kind of claystone rock,
which variety Naumann called Pechthonstein (pitch-clay-
stone).

Varieties in Texture.

(a) COMMON PITCHSTONE. \ Very variously coloured. Ex.g.

I Trieb'isch Thai near Meissen.

(6) PITCHSTONE-PORPHYRY. j With sanidine crystals. Mohorn
PECHSTEINPORPHYR. (Germ.) I and Spechtshausen, between Frei-

Kimxin POKPHYROlDE. (/>.) J ^ DreS den.

A rock of this description is met with at Castelruth in

Southern Tyrol ; it contains a felspar resembling sanidine and

round grains of quartz, and v. Bichthofen describes it as a

quartz-porphyry.

PECHTHONSTEIN, Naumann. (Germ.) I ma nn, a Stage of decompo-

J sition not unfrequent near
Meissen.

Pitchstone is for the most part of irregular massive
structure. It usually occurs associated with quartz-por-
phyries, and traverses them in dykes ; probably, however,
its geological age is not very different from that of the
quartz-porphyries, and it would seem to bear somewhat
the same relation to the porphyries as perlite and obsidian
to the trachyte porphyries.

The vitreous state of pitchstone is somewhat enigma-
tical, inasmuch as that rock usually occurs with rocks of
decidedly plutonic origin, and moreover contains a large
proportion of water : Bischof and Jenzsch consider the
glassy texture to be the consequence of transmutation by
aqueous process, and only to be apparently vitreous.
But it is very possible that under special circumstances in
the interior of the earth, eruptive igneous masses may
have cooled very rapidly, perhaps in consequence of the
sudden accession of a large quantity of water, and so
have become converted into a vitreous state containing
water.

226 ACIDIC IGNEOUS KOCKS. (2) PLUTONIC.

References.

Knox discovered a bituminous substance in pitchstone.
Transact, of the Geol. Soc. 1811, vol. i. p. 278, and Ann. d.
Phys..et Chem. 1823, vol. xxii.^ p. 44.

Necker de Saussure. Voyages en Ecosse et aux lies Hebrides,
vol. ii. p. 455. The pitchstone of the Hebrides exhibits
under the lens a fine granular texture resembling basalt.

Macculloch, Descr. of the Western Islands, vol. i. p. 520, on
the pitchstone of the Hebrides.

v. Oeynhausen and v. Decken, on the Pitchstone of the He-
brides, in Karsten's Archiv. vol. i. p. 50.

Haughton concludes from his analysis of pitchstone, that it con-
sists of a combination of about 62 felspar, 30 stibite, and
7 quartz.

Naumann, on Pitchstone and Pitch-claystone from Meissen, in
the Erlauter. zur. geogn. Karte v. Sachsen, 1844. No. 5,
p. 184.

Cotta, on the Pitchstone of Meissen and Tharand, Geognostiche
Wanderungen, 1836, vol. i. pp. 40 and 104.

Scheerer, Analysen u. Folgerungen in the Art. Pechstein in
Liebig's Handworterbuch der Chemie, 1854, vol. vi. p. 105,
and in v. L. u. Br. Jahrbuch, 1855, p. 60.

Jenzsch considers pitchstone to be fine crystalline, and a pro-
duct of transmutation and the balls of felsite in it, for re-
mains of porphvry not yet transformed. Zeitsch. d. d. geol.
Ges. 1856, p. 257.

Rentzsch, Die Pechsteine, 1860.

H. Fischer, on Pitchstone and Pearlstone, Zeitschr. der deutsch.
geol. Ges. 1862, vol. xiv. p. 312.

227

CHAPTER II.

METAMORPHIC CRYSTALLINE SCHISTS.

THE term Metamorphic as applied to these rocks implies
that they are the product of the metamorphosis of rocks
originally sedimentary, and, although several gneiss rocks
may have had another origin, they cannot be lithologically
separated from those of undoubted metamorphic character.

The designation of Crystalline Schist on the other hand
rests solely on petrographical characteristics.

The mineral composition of these rocks most resembles
that of the plutonic division of the acidic igneous rocks,
i.e. they consist (like those) chiefly of compounds of fel-
spar, quartz, mica, talc, chlorite, and hornblende, and do
not essentially contain pyroxene. We might indeed have
anticipated the resemblance of the metamorphic rocks to
the plutonic rather than the volcanic division of igneous
rocks (whether basic or acidic) as their transmutation
has probably taken place deep in the interior of the
earth, therefore under plutonic influences ; and the fact
that they contain more silica and less lime and magnesia
on the average than the basic igneous rocks, is accounted
for by the separate beds of carbonate of lime and magnesia
(limestones and dolomites) which interlie the metamorphic
rocks, whence we should expect to find the last mentioned
rocks somewhat deficient in those bases. But we shall
find that some of the crystalline schists are in fact rich in
lime and magnesia, and therefore are more allied to the
basic rocks. Those of prevailing acidic character are
principally granulite, gneiss, mica-schist, quartz-schist,
itacolumite and argillaceous mica-schist. The basic on the
other hand are : chlorite-schist, talc-schist, and hornblende-
schist, and others.

All the rocks of this class are to be distinguished from
the igneous by their foliated texture, and yet more by
their alternate bedding in parallel layers or strata, and the

228 CRYSTALLINE SCHISTS.

traces which they often very distinctly show of internal
stratification. These phenomena it is true are sometimes
exceptionally met with in the igneous rocks, but in them
they are the reverse of characteristic ; their foliated tex-
ture, when it occurs, is usually to be explained by local
pressure, their stratification by successive overflows of
fused matter; as a general rule the igneous rocks also
differ very widely in the character of their bedding from
the metamorphic schists. Nevertheless there are actual
petrographic transitions between the two, and in some in-
dividual cases where the nature of the bedding is not very
distinctly marked it is difficult to decide the character of a
given rock.

The properties which the crystalline schists have in
common with the sedimentary rocks are stratification,
fissile texture, and parallel alternating bedding ; on the
other hand the schists are wanting in organic remains
(fossils) and in mechanical aggregates. In their com-
position they differ from the sedimentary rocks by the
crystalline state of their mineral ingredients. There is,
however, no very definite boundary between the two ; on
the contrary there are series of distinct transitions from
one to the other just as we might expect to find if the
crystalline were really as we suppose them to be, the
offspring of the sedimentary rocks. We moreover find
that the greater part of the sedimentary rocks, and espe-
cially the older ones, are no longer in their original state
but are somewhat changed, doubtless by the identical
influences which at last have transmuted them into crys-
talline rocks and which are probably still in operation,
viz. heat and pressure.

The term Metamorphic, however, is in practice only
applied to the extreme products of this slow process of
transmutation, such as by assuming a crystalline state
have entirely departed from that of their original deposit,
although their connection with it may still be traced through
stages of transition. This is simply a matter of usage, for
looking to the meaning of the term., we might just as well
call every clay-slate or firm sandstone metamorphic
(transmuted) since they were not originally formed in the
state in which we find them at the present day.

Por these and other reasons it is difficult to prescribe

FELSPAR GROUP. 229

a definite and consistent limit to metamorphic rocks.
From a geological point of view we ought to include
in that term most granular limestone, serpentine, gra-
phite, magnetic iron-ore, &c., and reject many kinds of
gneiss and granulite as being irruptive ; but in a system
of lithology this treatment, however logically correct,
would lead to so many inconveniences and difficulties as to
render it impossible in practice.

For these reasons we have not made use of the general
designation Metamorphic rocks as the title for this
chapter, but chosen the more restricted term of Metamor-
phic crystalline schists. These for the most part are
compounds rich in silica, which, in their chemical com-
lHition approach Bunsen's formula for the normal
trachytic rocks. Some few, however, are poor in silica
and resemble the basic igneous rocks in composition.
We do not propose to divide the metamorphic schists into
basic and acidic groups ; we prefer to group them accord-
ing to their leading mineral ingredients without attempting
a strict scientific arrangement, except that we begin with
those which in their mineral character bear the greatest
resemblance to the granite rocks and place those last
which approach most in character to the unchanged
sedimentary rocks.

CRYSTALLINE SCHISTS, RICH IN FELSPAR.
(Granulite and Gneiss.)

21. GRANULITE, LEPTYNITE.

GRANULTT, WEISSSTEIN. (Germ.)
LEPTYNITE, Haiiy. (Fr.)

A fine-grained to compact fissile compound of felspar and
quartz ) usually with some mica.

Spec. grav. . ... . 2-62-7

Contains silica . . 70 80 p. c.

This rock, oil account of its frequent white or light-
yellowish colour, was formerly called weissstein (white
stone) ; but as the same mineral compound also occurs of
a dark colour, Weiss proposed to substitute the name of
granulite, which has now been generally adopted. Its
mineral composition is for the most part that of a granite
or gneiss (a red gneiss), with very little mica. Its cha-

230 CRYSTALLINE SCHISTS.

racteristic varieties are nevertheless easily to be distin-
guished from granite and gneiss, as will appear from a
more special description of the rock. Intermediate grades
of uncertain character and transitions are, however,
frequent, and if these occur in the midst of gneiss or
granite, we reckon them without hesitation, to those rocks,
and call them granulitic gneiss, or granulitic granite ; but
if found in granulitic regions the same rocks would be
properly termed gneissic granulite, and reckoned to the
granulites.

The felspar of granulite is mostly orthoclase ; some-
times, however, in part oligoclase. It is intimately
blended with the quartz, which is Jess in quantity,
or at all events is less apparent, than in granite or
gneiss. The free quartz forms few and very thin sepa-
rate layers, or flat lenticular grains, which are to be most
distinctly seen when the rock is weathered. The mica
appears in small scattered laminae, disposed in parallel
planes, or if sometimes found connected, scaly seams en-
tirely dividing the rock, which otherwise is an intimate
compound of felspar and quartz. In both cases the mica
increases the fissile texture of the rock. It is usually a
white variety of mica seldom black. The felspar, which
is always predominant, is usually white, yellowish, or
light-red ; and these are, therefore, the prevailing colours
of the rock. The quartz is never dark-coloured, seldom
transparent, and usually white. In a section of the rock
the seams of mica sometimes produce riband stripings of
dark colour. There are, however, varieties of granulite
in which the whole mass is of a blackish-green to almost
quite black colour (owing perhaps to protoxide of iron);
for these the old name of weissstein is inappropriate.

We repeat, then, that the essential constituents of the
rock are its felspar and quartz, and a small proportion of
mica. In addition to these, red garnets often appear
disseminated through the mass in small grains or crystals ;
where little or no mica is present, then these garnets are
especially frequent, and this is the most characteristic
composition of granulite. Where much mica is' found, the
garnets appear to fail, and varieties of this latter kind
form the transitions into gneiss. Another characteristic
accessory ingredient of granulite, though but * sparingly

FELSPAR GROUP. 231

distributed, is blue disthene (kyanite). Schorl and horn-
blende also occur, but more locally.

This rock forms transitions into granite by assuming a
more distinctly granular, and less fissile texture, into
gneiss, by the increase of its mica, and into felsite-schist,
when its mica disappears and the mass becomes quite
compact.

Varieties in Texture.

(d) COMMON GRANULITE. ) White, yellowish, or flesh-red,

GEMEINER GRANULIT. (Germ.) I with little or no mica, contains
LEPTYNITK COMMUN. (Fr.) J ^^ g^et^ ^d frequently

some disthene. It is more laminated than properly speaking
foliated or slaty. Rosswein in Saxony.

(b) RIBAND-STRIPED GRANTJLITE. ) Striped by parallel seams of

BAXDSTREIFIGER GRANULIT. (Germ.) L mica, interlying the main

J mass of felspar and quartz.

On the Zschopau between Sachsenburg and Schonborn in
Saxony.

GLIMMERRHICHER oder GNEISSGRANUUT. (Germ.) I garnets. Mitt-
LKPTYNITE MICACE. (Fr.) J we id a in Saxony.

(d) GRANITIC GRANULITE. ] More granular than fissile. This

GRANrrGRANULrr. (Germ.) I variety passes into a kind of granite
LEFTYNITE GRENU. (Fr.) j w hich contains little mica, and where
it occurs in the form of dykes or veins, it may be considered
as a granite. Neighbourhood of Herrnhut in Saxony.

. protoxide

LEPTYNITE NOIR. (Fr.) I of iron. Tenig in Saxony.

(/) SPOTTED GRANULITE. ) "With dark spots caused by horn-
GEFLECKTER oder FORELLKN- f blende. Glocknitzer Schlossberg,

ORAKUZ^T. (Germ.) ) Wiener Neustadt.

(0) SCHORLACEOUS GRANULITE. ] With considerable quantity
TOURMALINGRANULIT. (Germ.) [ o f 8C horl in its composition.

) W
of
*) Ac

LEPTYNITE TOURMAJJMFERE. (Fr.) T TT

') According to v. Hochstetter,

it occurs near Krummau in Bohemia,

Granulite is usually of very regular tabular-jointed
structure, disposed parallel to the foliation or lamination
of the rock ; but besides this more or less horizontal
jointing, it is also usually intersected at right angles by
cross joints, somewhat crooked, but whose surfaces are
smooth. This latter jointing is characteristic of granulite,
which by its means may sometimes be distinguished from
gneiss at a considerable distance.

In Saxony, Bohemia, and Moravia, this rock fills con-
siderable regions of elliptical shape, surrounded by other

232 CRYSTALLINE SCHISTS.

crystalline schists. The granulite region of Mittweida
in Saxony is surrounded and overlayed with mica-schist
and dichroite-gneiss, of which latter it contains large frag-
ments. It is also penetrated in all directions by numerous
often very distinct, but narrow dykes or veins of granite.
JSTaumann considers this region to be of eruptive origin.
Metamorphic rocks may possibly in some cases have
become eruptive here.

References.

JEnyelbrecht, Kurze Beschreibung des Weisssteins, 1802.
Weiss, Neue Schriften naturf. Freunde in Berlin, vol. iv.

p. 350.
fforniff, Analysen des Kremser Granulits, in den Sitzimgs-

berichten der k. k. Akademie zu Wien, 1851, vol. vii. p. 586.
v. Hochstetter, Granulit von Krummau, in Jahrb. d. geol.

Reichsanst. 1854, vol. v. p. 11, and the Corresp.-Bl. d. geol.

mineral. Ver. zu Eegensburg, 1853, p. 157.
Naumann, in Erlauter. z. geogn. Karte v. Sachsen, No. 1,

p. 9, and 1838, No. 2, p. 19 ; Karsten's Archiv, 1832, vol. v.

p. 393, and Jahrb. d. geol. Reichsanst. 1856, p. 766.
Zirkel, Granulit-analysen, in Poggendorff's Annalen, vol. cxxii.

p. 624.

22. GNEISS.

GNEISS, GNEUSS. (Germ.}
GNEISS. (Fr.)

A crystalline-granular compound of quartz, felspar, and
mica; texture foliated.

Spec. grav. . . . * . 2-6 27
Contains silica 64 76 p. c.

The mineral composition of gneiss is precisely the same
as that of granite ; the only petrographic difference be-
tween the two rocks consists in the foliated texture of the
former. We may, therefore, say that gneiss is the name
given to schistose granite. The term gneiss originated
with the Freiberg miners, who from ancient times have
used it to designate the rock in which their veins of silver
ore were found, and more especially such parts of the
rock as were much decomposed.

The felspar of gneiss is usually orthoclase, sometimes
with oligoclase, and perhaps even albite. The orthoclase
is white, grey, yellow, or reddish, and on fresh cleavage
surfaces has mother-of-pearl lustre. Usually it occurs

FELSPAR GROUP. 233

only in small grains, sometimes larger crystals or lentil-
shaped masses so called, swellings or eyes (Schwielen,
Augen), with the regular twin growth peculiar to ortho-
clase (porphyritic gneiss, augen-gneiss). The oligoclase
which occurs with and subordinate to the orthoclase or
(more rarely) as its substitute may usually be recognised
by its twin stripings, more resinous lustre, or more
advanced decomposition.

The quartz forms small white or grey lentil-shaped
grains or irregular excrescences upon the felspar ; more-
over it often appears in separate larger and irregular
masses.

The mica is usually potash-mica (more rarely magnesia-
mica), brown, black, white, or dark-green ; and some-
times in the same gneiss different coloured micas occur
together.

Gneiss occasionally contains accessory ingredients of
various kinds, such as chlorite, talc, graphite, micaceous
iron, dichroite, garnet, tourmaline, andalusite, pistacite,
zircon, disthene, rutile, titanite, pyrites, magnetic iron-
ore, &c.

Sometimes one or other of these minerals is abundant,
and assume the character of an essential ingredient ; thus,
for instance, the prevalence of hornblende occasions a tran-
sition from ordinary gneiss into syenite-gneiss, the presence
of chlorite or talc into protogine-gneiss, &c. These
different varieties in composition are easy of recognition.

It is more difficult in many cases to recognise the
perhaps more important difference between the so-called
' red ' and * grey ' gneiss. It was formerly considered
that all gneiss was of metamorphic origin, but it has of
late years been established beyond a doubt that many
kinds of gneiss are irruptive, and some geologists have
gone so far as to regard all gneiss as of igneous origin.

In the mining districts of the Erzgebirge it had been
observed that the veins in the red varieties of gneiss were
usually non-metalliferous, although within a short distance
the same veins traversing grey gneiss were rich in ore.

Previously to the year 1844, we ourselves had observed
red gneiss of a distinctly eruptive character, forming veins
in the grey gneiss, which latter is the prevalent rock of
the mining districts of the Erzgebirge ; the result of

234 CRYSTALLINE SCHISTS.

these observations we published in von Leonhard's
Almanack. (Vide v. L. u. Br. Jahrb. 1844, p. 681.)

Subsequently Professor Scheerer received a commission
from the Saxon mining authorities, to analyse several
kinds of gneiss, with a view to discover the cause of the
superior richness of the metalliferous veins in the grey
gneiss ; and he found amongst other chemical differences
that the red gneiss usually, if not always, contained a
considerably larger proportion of silica than the grey.

Accordingly the gneiss of the Erzgebirge came to be
divided into two principal classes of distinct mineralogical
as well as chemical characters, termed respectively red
gneiss and grey gneiss.

The red gneiss is not, however, always to be easily dis-
tinguished from the grey gneiss, as the colours of the two
distinct classes do not in every case correspond with the
names that have been given to them, and some so-called
grey gneiss is of red colour, and vice versa ; and although
in several instances the bedding of the red gneiss shows
it to be of distinctly irruptive character, yet the bedding
of both kinds of gneiss is frequently indistinct and un-
certain, or might be capable of various interpretations,
and therefore would not alone serve the purposes of litho-
logical distinction. The recognised and only reliable
distinction consists in the proportion of silica, only to be
arrived at by chemical analysis of the rock. These con-
siderations compel us, regardless of origin, to retain the
usual classification for all gneissic rocks, and notwith-
standing the irruptive character of some varieties, to treat
them collectively in this place amongst the metamorphic
rocks.

We proceed to define these two principal classes of
gneiss, and (to avoid attaching an undue importance to
their mere colour) we propose the name of gneissite for
the variety formerly known as the red gneiss :

A. GNEISSITE, or RED GNEISS. (Rother Gneiss oder
Gneissit. Germ.) The felspar of the compound appears
to be always orthoclase, and to be the predominant in-
gredient. The mica is always white, or at all events not
dark-coloured, not abundant in quantity, but usually
scattered through the mass in thin straight laminae.

The rock contains 74 76 per cent, of silica.

FELSPAR GROUP. 235

According to Scheerer,it is an acidic compound, a sesqui-
silicate. Its extreme varieties are easily to be recognised,
and may be better distinguished from the grey gneiss than
gneiss from many varieties of granulite. Its felspar is
usually reddish, exceptionally, however, white or greyish.

In the Erzgebirge this gneissite is found in irregular
tracts, and sometimes forming distinct dykes or veins in
the ordinary gneiss, of which it frequently encloses frag-
ments. We may therefore say that there it comports
itself as an eruptive igneous rock towards the common
gneiss, and geologically speaking should perhaps properly
be considered a granite. But as its bedding is frequently
indistinct and the character of single specimens is often
not to be recognised with certainty, and as some kinds of
gneissite may very possibly be of metamorphic origin, we
cannot usefully separate it lithologically from every other
gneiss by taking it out of the class of the crystalline schists.

B. GREY GNEISS. (Grauer Gneiss. Germ.) The
felspar of the compound is principally orthoclase, some-
times, however, with the orthoclase some oligoclase or
albite is associated. The mica is partly dark-coloured
(ferruginous and more basic than that of the gneissite),
it is moreover abundant, whence the rock usually assumes
a dark or grey colour.

The rock contains 64 67 per cent, of silica.

According to Scheerer, it is a neutral silicate. The
normal Freiberg variety is granular, scaly, and unevenly
foliated. The felspar is usually white or grey, but some-
times of a reddish colour. The mica is mostly dark-
coloured, but some white. Mica occasionally occurs in
the compound. Accordingly, the differences between
these two normal varieties (the gneissite and the grey
gneiss) may be stated as follows :

Gneissite, or Red Gneiss.

Content of silica, 74 76 p. c.
Felspar orthoclase only.

Mica in small quantity and
li<rht-coloured.

Approximate proportion of mineral
ingredients.
30 quartz
60 felspar

10 illicit

Ordinary, or Grey Gneiss.

Content of silica, 64 67 p. c.
Felspar orthoclase and sometimes

oligoclase.
Mica abundant and dark-coloured.

Approximate proportion of mineral
ingredients.
25 quartz
45 felspar
30 mica

236 CKYSTALLINE SCHISTS.

The mica (both of the gneissite and grey gneiss) usu-
ally contains about 4 per cent, water, and this water
Scheerer regards as an original ingredient of the mineral
entering into its chemical composition, as a base to the
silicic acid.

Besides these two extreme kinds of gneiss, it appears
that many intermediate grades exist, which may be col-
lectively designated as

C. MEDIUM GNEISS. (Mittelgneiss, Germ.) Gneiss
containing an intermediate proportion of silica between
that of the gneissite and the grey gneiss. The mineral
character sometimes resembles the one and sometimes the
other of those two extremes.

Scheerer has endeavoured to show that, chemically
speaking, this medium gneiss C forms an independent
rock or variety, whose proportion of silica is constant be-
tween 69 and 70 percent., and that it therefore uniformly
and essentially differs from the varieties A and B. (Vide
Scheerer iiber die Gneusse des Erzgebirges in the Zeit-
schrift der deutschen geol. Ges. vol. xiv. ; also published
separately, Berlin, 1862.)

Later analyses have, however, shown the existence of
gneisses varying in their composition, and especially in
the proportion of silica which they contain, as much from
the normal medium gneiss as from the two extreme va-
rieties of red and grey gneiss. Therefore we must guard
ourselves against expecting any sharply defined chemical
character in the different varieties which come under our
notice.

We must remember that it is only of late years that
attention has been called to this subject, and with the
utmost chemical industry but few analyses, comparatively
speaking, have yet been made with the special object of
distinguishing different species of gneiss. These analyses
have chiefly been conducted at Freiberg, and mainly with
a view to ascertain and discover whether any and what
differences of rock coincide with the richness of metal-
liferous veins in the Erzgebirge. It appears to be an
established fact that the grey gneiss is more favourable
for the yield of rich veins than the gneissite or red
gneiss.

This is a very interesting fact, which deserves the

FELSPAR GROUP. 237

attention of geologists. At present we are not aware of
any thoroughly satisfactory explanation of it, unless we
adopt Scheerer's theory that the iron of the mica in the
grey gneiss is the cause of its advantage in this important
respect. He has shewn that the mica is invariably decom-
posed for some distance on each side of the metalliferous
veins.

The gneiss of the Erzgebirge is undoubtedly partly
irrnptive and partly metamorphic ; and we believe that
its character in this respect must always be determined
rather from observation of the bedding than from the
chemical composition of each individual rock ; at all
events, the analyses which have hitherto been made do
not justify the conclusion that rocks of a definite propor-
tion of silica are confined to any particular geological
origin, or vice versa that rocks of the same geological
origin are uniformly of one chemical character.

It would, indeed, be somewhat remarkable if it were
found that the collective elementary ingredients of a rock
like gneiss, consisting of three separate minerals, were
combined in such uniform proportions as to be capable
of being expressed by a simple chemical formula ; we
should rather expect that from a mass so constituted a
homogeneous rather than a compound rock would have
resulted. We are, however, ready to admit that the
strangeness of a phenomenon to our preconceived ideas is
no valid argument against its truth.

In the present state of our chemical investigations,
therefore, we can only seek approximately to range all
known gneisses under one or other of the three heads we
have named. If geologists in different parts of the world
will assist in this work, there is room for hope that some
general law may be discovered which shall advance the
state of science with respect both to the origin of gneiss
and the causes which have influenced the superior rich-
ness of the metalliferous veins in some rocks to the
exclusion of others.

Independently of the division into gneissite, grey gneiss
and medium gneiss, which, however important geologi-
cally, depends mainly on chemical, and only partly on
mineralogical, differences, we have the following varieties
in texture and composition.

238 CRYSTALLINE SCHISTS.

Varieties in Texture.

(a) COMMON FREIBERG GNEISS. ] Belongs to the class of grey
FREIBERGER NORMALGNEISS. (Germ.) L o-neiss. The flakes or laminae
GNEISS COMMON ou NORMAL. (Fr.) J g f mica are digtributed in

parallel planes through the granular compound of felspar and
quartz. The rock has often a folded or wavy texture. In the
immediate neighbourhood of metalliferous veins, near Freiberg,
it is impregnated with pyrites, sometimes with arsenical pyrites,
galena or blende, by which latter its decomposition is much
accelerated.

(J) PORPHTRITIC GNEISS. ] In the otherwise uniform schis-

AUGEXGNEISS oder PORPHYR- j. tose mass there occur at in-

S?SSffiy^!) > tervals large egg-shaped crystals

of orthoclase (usually they are

twin crystals, sometimes they are amorphous), round which
the foliated texture bends itself with a wavy sweep. This is
very characteristically developed near Schwartzenberg in the
Erzgebirge, Kedwitz in the Fichtelgebirge.

STANGELGNEISS oder HOLZGNEISS. (Germ.) > are disposed in

a fibrous manner towards one direction, so that a peculiar
linear parallel conformation is produced. The stalks or fibres
may consist of felspar and quartz, or of stripes of mica. In
the extreme development of this texture a wood-like confor-
mation is produced, which almost supersedes the schistose
texture. Lippersdorf, Lengefeld, Weissenborn, and Weig-
mannsdorf, near Freiberg, Saxony, Sonnenberg in Bohemia.

(d) VERY FINE SLATY GNEISS | All the mineral parts small 5 the

or SLATE-GNEISS. j- numerous parallel flakes of mica
SCHIEPERGNEISS. (Germ.) j occasion very distinct slaty texture.
In the cleavage, mica alone is usually seen.

(e) VERY FINE-GRAINED, ALMOST ) With only indistinct foliated tex-

COMPACT GNEISS. Y ture. Radegrube, near Freiberg,

GNEISS A GRAINS FINS. (Fr.) J Radeberg, near Dresden.

(/) LAGEN GNEISS. j Quartz and felspar on the one hand, and

LAGENGNEISS. (Germ.) L the mica on the other, form thin parallel

GNEISS RUBANE. (Fr.)] ^ mutuaJ Q y altera ating seams or layers,

which, in the cross section, occasion a ribbon striping.

(g) GRANITE-GNEISS or GRANITIC GNEISS. \ With very

GRANTTGNEISS oder GRAXITAHNLICHER GNEISS. (Germ.) } granular and

only indistinctly foliated texture, forming a transition state

between gneiss and granite. Sageritz near Grossenhain, Boxdorf

near Moritzburg, Brambach in the Voigtland, Hofles near Eiger.

Naumann has collected into one class, under the name of

' CORNUBIATES,' several exceptional varieties of gneiss, some

compact, or of very indistinctly compound texture, others of

contorted foliated texture. They occur variously, usually as

contact formations at the margins of more recent igneous rocks.

Saussure called them ' PALAIOPETRE,' Boase ' PROTEOLITE.'

Properly speaking they belong only geologically, and not pe-

trographically to gneiss, and they can only be classed as gneiss

where their position and bedding give them that character.

FELSPAE GROUP. 239

Varieties in Composition.

(ft) GRANULITE-GNEISS. \ With very little mica, and that usually
GKAxcuKiNKiss. (Germ.)) white. Felspar predominates, and is
often intimately combined with quartz. Always belongs to
the gneissite or red gneiss. Grosswaltersdorf near Freiberg,
Lauterbach near Marienberg, Mautern near Molk, Poppenreut
near Miinchberg. Hochberg near Eger; and a variety with
dark-coloured mica, Fahrnleiten, near the Schneeberg, in the
Fichtelgebirge.

(0 MICACEOUS GNEISS. | Forming a transition state into mica-
GLIMMEROXEISS. (Germ.) } schist, with much mica, chiefly dark-
coloured, and little felspar ; usually of a line foliated texture.
Near Kabenau and Dippoldiswalde in Saxony, where it occurs
between strata of ordinary gneiss ; also, in like manner, at
Gastein in the Alps.

(k) GM;ISS VKUV RICH IN QUARTZ, and going over into a kind of
quartz-schist.

(/) SYENITIC GNEISS. ] With characteristic admixture of horn-

SYENITGNEISS. (Germ.) I blende. Neighbourhood of Aschaffen-

Fichtelgebirge.

(m) PROTOGINE-GNEISS. ] With chlorite or talc instead of mica.
PROTOGINGNEISS. (Germ.) ^Oberhasli and Mont Blanc in the Alps.
Fr.) )M tle Q oldber near

Fichtelgebirge, a somewhat indistinct protogine-gneiss encloses

fragments of clay-slate, and from this would appear to be of

igneous (irruptive) character.

(n) ADULARIA-GNEISS. \ With adularia in the place of the usual
ADULARONEISS. (Germ.) \ orthoclase. Very widely spread in the

Alps, e.g. St. Gotthard.

(o) OLIGOCLASE-GNEISS. ^ With oligoclase in the place of ortho-
OLIGOKLASGNEISS. (Germ.) \ c lase. According to v. Hochstetter, the

lofty Adam's Peak of Ceylon (7,000ft.) consists of this rock.

It contains many garnets, and is found in alternate layers with

syenite-gneiss, granulite-gneiss, granulite, and hornblende-slate.
(p) GNEISS WITH TWO KINDS OF MICA, white and black, occurs very

frequently. Seerenbach near Tharand, Lauenstein in the Erz-

gebirge, Steingriin near Eger.
(q) DICHROITE-GNEISS. | With dichroite in the place of mica.

DICHROITGNEISS. (Germ.) Found in the margin of the Saxon

0*1088 AVEC DlCHKOrTK g

selburg.

(r) MICACEOUS IRON GNEISS. | With micaceous iron instead of com-
i-:.>KxLiMiaROKEi.7rm.) } mon m i ca . i n the southern Fichtel-

gebirge.
(a) GRAPHITE-GNEISS. \ With graphite in the place of the mica.

&BU*puBM.(0*m);Neax Passau, on the Danube.
(<) ALPIXITE. | Is a name given by Simler to a schistose com-

ALP (6?i Simler ' [pound of quartz, 'felspar (oligoclase), and a
j flaky green mineral, probably belonging to the
mica species, but certainlv not chlorite or talc (liber die Petro-
geneses. Berne, 1862). Very frequent in the Alps.

240 CRYSTALLINE SCHISTS.

The above are the principal varieties of this very im-
portant rock ; it would neither be possible nor desirable
to enumerate every modification of differing texture and
composition.

Gneiss, in addition to those of its accessory ingredients
which have been already mentioned, sometimes contains
irregular concretions or minute veins of quartz, felspar, or
a kind of granite resembling the graphic granite.

The foliated texture of gneiss is a universal charac-
teristic. Gneiss is also usually stratified or jointed in a
direction parallel to its texture. At all events a divergence
from this direction has not been hitherto observed. Be-
sides this tabular jointing there is sometimes a tolerably
regular oblique parallelopipedic jointing dividing the rock
into irregular rhombs, two of whose faces correspond with
the stratification of the rock.

Gneiss is found in extensive regions in many mountain
districts. The mountains which it forms are of very
various shapes, according to the position and direction of
the foliated texture. If this be horizontal then we have
fiat undulating table-lands where valleys appear like cuts
in the otherwise uniform surface. If, however, the bed-
ding of the rock has been upheaved so that the parallel
planes of the texture assume a vertical position, then it
forms jagged alpine heights. Both the bedding and the
texture are frequently very much contorted.

Gneiss, wherever we can approximately determine its
geological age, is found to be of high antiquity. It occurs
with granite rocks usually lying above them, but often
penetrated and traversed by them. The oldest sedi-
mentary rocks usually overlie the gneiss, but there are
some exceptions where, as in the Alps and the Fichtelge-
birge, the gneiss is found uppermost ; these exceptions
are capable of being explained by disturbances of the
original bedding.

References.

Scheerer, Chemische Untersuclmiigen des Gneisses im Jahrb. d.
k. sachs. Bergakademie z. Freiberg, 1858, p. 210, 1861,
p. 252, 1862, p. 188 ; Berg- u. Hiittenm. Zeitung, 1861,
p. 188 ; and v. L. u. Br. Jahrb. 1861, p. 613 ; Zeitsch. d. d.
geol. Gesells. 1862; also separately published under the
title of ' Die Gneusse des Erzgebirges.'

QUARTZ GROUP. 241

Naumann, Erlauter. z. geogn. Karte v. Sachsen, No. 2, p. 265,

and No. 5, p. 51.
Cotta, Rother u. Grauer Gneiss, in v. L. u. Br. Jahrb. 1844,

p. 681, and 1854, p. 39.

Credner, Syenitgneiss, in v. L. u. Br. Jahrb. 1850, p. 549.
Peters, Syenitgneiss, in Jahrb. d. geol. Reichsanst. 1853, p. 236.
Kittel, Syenitgneiss, Umgegend v. Aschaffenburg, 1840, pp.

11 and 27.
v. Rath, Gneiss in Graubiindten, Zeitschr. d. d. geol. Ges. 1858,

p. 199.
Fournet, Gneiss der Alpen, Me*m. sur la Ge*ol. de la part des

Alpes, p. 29.

Boose, Transact, of the Geol. Soc. of Cornwall, vol. vi. p. 390.
Quincke, Schonfeld and Roscoe, Analysen in Ann. der Chem.

u. Pharm. 1854, vol.xci. p. 306, and 1856, vol. xcix. p. 239 ;

v. L. u. Br. Jahrb. 1855, p. 453.
v. Hochstetter, Oligoklasgneiss, Novarra-Reise, 1861, Th. i.

p. 324

CRYSTALLINE SCHISTS RICH IN QUARTZ.
(Mica-schist, Quartz-schist, Itacolumite.)

23. MICA-SCHIST.

GLIMMERSCHIEFER. (Germ.)
MICASCHISTE, Brvngniart. (Fr.)

A crystalline schistose compound of mica and quartz.

Spec. grav. . . . V ; . 27 3-1
Contains silica . .. > . . ' 6982 p. c.

Its texture is always foliated, but with many varieties of
modification. Its composition varies between two ex-
tremes ; one consisting almost entirely of mica, the other
(quartz-schist) almost entirely of quartz.

The mica is most usually the optically biaxial potash-
mica, but sometimes dark magnesia-mica, damourite, or
paragonite. Two different kinds of mica occasionally occur
together in the same rock. Usually the laminae, whether
large or small, all lie in planes approximately parallel to
each other, and thereby occasion the foliated texture of
the rock ; it is rare to find them in diverging directions.

The mode in w^ich the mica and quartz are united is
somewhat various. In those varieties which contain the
most mica the small grains or lenticular particles of quartz
usually lie hidden in it, and the rock appears almost
exclusively to consist of mica. If the quantity of quartz
be greater, then its larger lenticular masses are dis-
tinctly prominent amongst the mica in a cross fracture of

242 . CRYSTALLINE SCHISTS.

the rock. Again, these lenticular bodies extend and
are elongated into thin parallel layers of granular com-
position, and sometimes themselves enclose small flakes of
mica of divergent direction. Those varieties which are
very rich in quartz consist almost entirely of that mineral,
and only receive a foliated texture from the thin parallel
layers of mica imbedded in the quartz.

Sometimes (and even in varieties very rich in mica) in
addition to the quartz contained in the main mass of the
rock, irregularly swollen-shaped masses and veins of quartz
occur, round which the foliated texture bends itself, or
there are found actual seams of quartz in the rock.
Garnets frequently occur in such abundance as to be
characteristic for certain varieties. They are red or
brown, and occur porphyritically as isolated crystals, un-
usually rhombic dodecahedrons, from the size of a scarcely
visible grain to that of an apple. In each individual rock,
however, these are usually nearly of a uniform size.
The flakes of mica bend round these crystals as if they
had been pushed on one side during the process of their
formation. Near Fahlun, in Sweden, there is a magnesian
variety of mica-schist containing very large dodecahedrons
of garnet, which are sometimes split into two parts which
have become joined together again in a displaced position.

Mica-schist also frequently contains some or other of
the following as accessory ingredients : schorl, staurolite,
disthene,andalusite, hornblende, chiastolite, beryl, chlorite,
talc, and felspar less frequently, also graphite, micaceous
iron, cordierite, pyrites, or cinnabar, &c.

Some of these accessory ingredients are characteristic
for certain varieties of mica-schist, and they also occasion
transitions from mica-schist into other rocks. Thus the
presence of chlorite occasions a transition into chlorite-
schist,of talc into talc-schist, of felspar into gneiss, of schorl
into schorl-schist, of graphite into graphite-schist, of mi-
caceous iron into ferruginous mica-schist. If the mass
becomes compact, and especially if the mica should be-
come indistinctly blended with the other ingredients, then
the rock passes over into argillaceous mica-schist, and finally
into clay-slate, so that we have thus a complete series of
transitions from the most distinct gneiss through mica-
schist into clay-slate. But we know of no transition from

QUARTZ GROUP. 243

mica-schist into the granular greisen, although the com-
position of those two rocks is mineralogically the same.

Varieties in Texture.

(a) COMMON MICA-SCHIST. \ Somewhat unevenly fo-

GEMEINEH GLIMMBBSCHIEFER. (SCHTTPPEN- f liated, of a scaly ap-

GLIMMKKM-HIKFEU.) (Germ.) .,1 V r ,

MICASCHISI-E COMMUN ou NORMAL, (Fr.) J pearauce with very much
mica, but the quartz nevertheless distinct. Of very frequent
occurrence.
(6) MICA-SCHIST, VERY FINE AND]

EVEN IN TEXTURE. Y Also frequent.

PLANGLIMMERSCHIEFER. (Germ.) )

FAI/TENGLIMMERSCHIEFER. (Germ.) L ture. occasions a very dis-

J tine? linear parallelism.

Sometimes there occur larger and more irregular foldings,
windings, and contortions of the texture, but these are fre-
quently very parallel in their main direction. E. g. at Schwarz-
enbach, near Hof in the Fichtelgebirge.

(d) MICA-SCHIST WITH WOOD-LIKE OR \ Or as if the different par-

COARSELY FIBROUS TEXTURE. I tides had been elongated

GEOTRECKTER GLIMMERSCHIEFER oder f by stretchino- This pe-

HOLZGUMMERSCHIEFER. (Germ.) J c il iar textlire is caused by

a special conformation of the quartz stripped into thin and

long strips or stalks.

(e) MICA-SCHIST WITH CONTORTED AND \ The disturbances of the

IRREGULAR TEXTURE. I parallel texture are partly

VKUWORREXSCHIEFRIGER oder WULST- r occasioned by external
GLIMMKUSCIUEKER. (Germ.) ,. , J ,,

1 TEXTURE FROISSEE ou PUSSES (Fr.)) forces, and partly by

many tuberous swellings

of the quartz contained in the rock. Very frequent.
(/) STRATIFIED MICA-SCHIST. j. Thin seams of mica with slaty
LAGBNGLIMMERSCHIEFER. (Germ.* cleavage, alternate with fine-
grained layers of quartz, in which last are sometimes dissemi-
nated flakes of mica not parallel to the stratification. This
rock is very characteristically developed near Eger, in Bohemia,
and between Korbach and Gefrees in the Fichtelgebirge.
(y) MICA-SCHIST OF KNOTTY TEXTURE. I Small nodules or concre-
KjfOTENGLiMMERscHiEFER, (Germ.) > tions pervade the mass and
occasion a knotty texture, disturbing the otherwise parallel
layers of the mica. Occurs in the Fichtelgebirge, between
"W alpenreuth and Hiihnerhof.

Varieties in Composition.
(A) GARNETIFEROUS MICA-SCHIST. \ Rich in garnets. Ofveryfre-

(iHANATGLIMMERSCHIEFER. (Germ.) f nll - nf n^n-rpn-p
MlCASCHIOTE GRENATIFERE. (Fr.) I ^^^ OCCUirCnCC.

(t) GNEISSIC MICA-SCHIST. I With some felspar in the

GNEIBSGUMIDJRSCHIEFER. (Germ.)> compound; forms a transition
state between gneiss and mica-schist. Frequent in the Erzge-
birge.

R 2

244 CRYSTALLINE SCHISTS.

(K) CHLORITIC MICA-SCHIST. ] With some admixture of chlo-

CHLORITGLIMMERSCHIEFER. (Germ.) r rite ; forms a transition into
MICASCHISTE AVEC CHLOMTE. (Fr.) c hlorite-schist. Frequent in

(/) TALCOSE MICA-SCHIST. ) With an admixture of some talc;

TALKGLIMMERSCHIEFER. (Germ.) \ forms a transition into talc-

MICASCHISTE AVEC TALC. (Fr.) j sc hi s t. Occurs in the Alps,
(m) MICA-SCHIST WITH TWO KINDS or MICA (dark and light-
coloured). Zschopau in Saxony.

() GRAPHITIC MICA-SCHIST. \ With admixture of graphite ;

GRAPHITGLIMMERSCHIEFER. (Germ.) r forms a transition into gra-

MlCASCHISTE AVEC GRAPHITE. (Fr.) ' 1

(o) MICACEOUS IRON-SCHIST. \ Forms a transition into

ElSENGLIMMERHALTIGER GlJMMERSCHIEFER. f femiginOUS Schist.

(Germ.) )

(p) SCHORLACEOUS MICA-SCHIST. ] Forming a transition into
SCHORLGLIMMERSCHIEFER. (Germ.) I schorl-schist. Eibenstock
MICASCHISTE AVEC TOURMALINE. (Fr.)) in S axonv>

(q) HORNBLENDIC MICA-SCHIST. } Forming a transition into

HORNBLENDEGLIMMERSCHIEFER. (Germ.) I hornblende-schist. E. g.
MICASCHISTE AVEC HORNBLENDE. (Fr.) J between Goldmiihl and

Brandholz, near Berneck in the Fichtelgehirge.
QTJARTZOSE MICA-SCHIST, forming a transition into quartz-schist.
CALCAREOUS MICA-SCHIST. \ This is either a granular lime-
KALKGLIMMERSCHIEFER, BLAU- [ stone, very rich in mica, and
SCHIEFER. (Germ.) ) therefore of fissile texture (ci-

polline), as it, for instance, occurs in the limestone beds in the
neighbourhood of Zaunhaus in the Erzgebirge, or it is a rock
composed of thin alternate layers of mica-schist and granular
limestone, as is frequently found in the Eastern Alps.

The following varieties differ in the species of their
mica :

(t) PARAGONITE-SCHIST. j The name given by Schafthautl

PARAGONTTSCHIEFER, Schafthautl. j to certain mica-schist of the Alps

(Germ.) n -^r^j^ -j^g ordinar mica is

replaced by paragonite or damourite. To this belongs, e. g., the
beautiful variety found at St. Gotthard, and is distinguished
by its containing many cyanites and staurolites.
(u) AMPHILOGITE-SCHIST. ) The name given by Schaft-

AMPHILOGITSCHIEFER, Schafthautl. r hautl to the delicate 'flaky and
(Germ.) somewhat greenish-white mica-

slate of Zillerthal in the Tyrol, which only contains 40 p. c.
silica.

(v) NACRITIDE. j The name given by Schill to a schist oc-

NACRITID, Schill. j curring at Pike's Peak in Kansas, consisting
(Germ.) Q f q uar ^ z ^fo bi ac k an( j w hite mica. Per-

haps it is the same as the Saxon variety described ante (m) .

Mica-schist is usually more or less stratified or laminated
independently of and more or less parallel to its schistose

QUARTZ GROUP. 245

or foliated texture. Sometimes many different varieties
alternate and are stratified in thin beds or layers one
above the other.

Mica-schist is extensively developed in many mountain
districts, and there it is usually accompanied by gneiss or
talc, and chlorite-schist ; it frequently also contains sub-
ordinate intermediate layers of quartz-schist, hornblende-
schist, granular limestone, or dolomite, ironstone, or even
graphite. The distinctly sedimentary formations usually
overlie the mica-schist, but to this rule there are excep-
tions, as in the case of gneiss. From its bedding and the
rocks with which it is usually associated, we must con-
clude that mica-schist has chiefly been formed by trans-
mutation from very ancient argillaceous and arenaceous
deposits. During this process the quartz has undergone
the least change, the clay has for the most part become
mica, the superfluous substances in the sedimentary rock
appearing, as accessory minerals in the mica-schist. A
clay-slate very poor in quartz might produce a mica-
schist very rich in mica ; and a clay-slate very rich in
quartz (or very sandy) might produce a mica-schist very
rich in quartz. An argillaceous sandstone might perhaps
produce that variety of mica-schist which forms a tran-
sition into quartz-schist. If the original rock contained
lime, then garnet, hornblende, and other minerals might
also be formed. If the original rock contained subordi-
nate strata or layers of limestone, ironstone, coal, or the
like, these would be changed into granular limestone,
ferruginous mica-schist, graphite, &c.

We must assume that these processes of transmutation
have always taken place deep in the earth under the
influence of great pressure, high temperature, and per-
haps that they have been aided by the presence of water
in other words, that they were plutonic or hydro-
plutonic processes. If there were sufficient alkali in the
argillaceous deposit, or if alkalies happened to be within
reach (possibly in a state of solution), then gneiss and not
mica-schist would be the result. If these hypotheses are
well founded, they explain the possible mode of formation
of some mica-schists, which appear to be of considerably
more recent origin than the greater part of those rocks.
The process of transmutation may have been hastened in

246 , CRYSTALLINE SCHISTS.

these exceptional cases by an extraordinary degree of
pressure. Cases of this kind are met with in the Alps,
where between strata of mica-schist certain beds of a
sandy calcareous composition occur containing distinct
remains of Belemnites.

Although mica-schist has been very frequently analysed
and described, there are but few treatises which make it
their principal subject. The following describe certain
special forms of this rock.

References.

Beudant and Naumann (the former in Hungary, the latter in
Scandinavia) have both observed apparent pebbles of quartz
in mica-schist a circumstance which forcibly suggests a me-
chanical origin (Naumann's Geognosie, 2nd. ed. vol. i. p.
527, Anm.). We have also ourselves observed distinct
pebbles of quartz in beds of limestone lying between parallel
beds of mica-schist at Jakobeni in the Bukowina. Jahrb. d.
geol. Keichsanst. 1855, p. 7.

Schqfthautl, on the peculiar varieties of the Alps, Ann. d.
Chem. u. Pharm. 1843, p. 733. (Schonfeld and Roscoe, ibid.
1854, vol. xci. p. 305.)

Schittj on Nacritide, Ann. d. Chern. u. Pharm. 1857, vol. ciii.
p. 119.

24. QUAKTZ-SCHIST.

QUARZSCHIEFEE. (Germ.)
QUARTZ SCHISTEUX. (-Fr.)

A rock chiefly consisting of quartz, but usually contain-
ing some mica.

We regard this rock as more or less belonging to the
mica-schists. It is found to pass over into genuine mica-
schist through the transition grade of quartzose mica-schist.

Mineralogically, this rock has greater affinity to the
siliceous or quartz rocks. Geologically, however, it
undoubtedly belongs to the metamorphic crystalline
schists, with which it is usually interstratified in parallel
but subordinate beds ; and, like the other crystalline
schists, appears to have originated in metamorphosis of
sedimentary rocks (probably sandstone).

We ought, perhaps, on the same principle to include
some other rocks in the metamorphic series (granular
limestone, for instance) ; calcspar, however, does not oc-
cur as an essential ingredient of any crystalline schists,
whereas quartz is contained in most, and we must con-

QUAETZ GROUP. 247

stantly remind our readers that a logically consistent
system of classification is impossible with rocks.

We shall again allude to this rock under the head of
quartz rocks, No. 69 post.

Varieties in Texture,
(a) COMMON QUARTZ-SCHIST. \ Consists principally of com-

CKMKINBB QUARZSCHIEFER. (Oerm.) [ pac t imperfectly - foliated

QUAIO* scm^x COMMUN. (/v.) ) U it 'e qua rtz, containing only

little mica; sometimes with very distinct parallel elongations.

Occurs in the gneiss of Freiberg.

(6) GRANULAR QUARTZ-SCHIST, j Fine-grained, resembling sand-

or QUARTZITE. I stone.

QPARZIT. (Germ.) Jukes says, l Quartz rock or

> quartzite is a compact fine-grained

but distinctly granular rock, very hard, frequently brittle,
and often so divided by joints as to split in all directions
into small angular, but more or less cuboidal, fragments. The
colours are generally some shade of yellow, passing occasionally
into red, and at other times into green. When examined with
a lens it may be seen to be made of grains, which appear some-
times as if they had been slightly fused together at their edges
or surfaces, and sometimes as if imbedded in a purely siliceous
cement. This cementation or semi-fusion of the grains shows
at once that it is a sandstone which has been altered and in-
durated by the action either of heat alone or of heat and water.'

25. ITACOLUMITE.

ITAKOLUMIT. (Germ.)
ITACOLUMITE. (Fr.)

A fine-grained and at the same time schistose compound
of quartz with some mica, talc, or chlorite. In thin
plates it is sometimes flexible.

This rock first received its name from Von Eschwege.
Its principal mass consists of grains of quartz, and re-
sembles a sandstone. The grains of quartz, however, are
bound together by thin crystalline Iamina3 of mica,
chlorite, or talc, and these often assume a parallel arrange-
ment and form thin seams through the rock. Thus its
foliated texture is occasioned, and the somewhat elastic
properties of the mica, chlorite, or talc occasionally give
a flexibility to thin layers or plates of the rock. But not
all varieties of itacolumite are flexible. The prevailing
colour of the rock is yellowish ; sometimes, however, it
has a white-reddish or bluish-grey colour.

As subordinate ingredients, there occur in it mica-

248 CKYSTALLINE SCHISTS.

ceous iron, magnetic iron-ore, martite, native gold, and
even diamond. The quartz also occurs locally in the
form of rounded stones or pebbles enclosed in the rock's
mass, showing clearly the mechanical arenaceous or con-
glomeratic origin of the rock. If the specular or magnetic
iron-ores occur in considerable quantity, then a transition
takes place into ferruginous mica-schist or itabirite (vide
post, No. 62 K) ; and if the quartz be altogether pre-
dominant, into quartz-schist (No. 24).

We may take it as proof of the variable character of
this rock that it has received many different names.
Alexander von Humboldt called it itacolumite or quartz
chloriteux ; Clausen termed it gres rouge, micaschiste
quartzeux, and gres itacolumite ; Von Martius, elastischer
Sandstein (elastic sandstone), Quartz-schist and Gelenk-
quarz (articulated quartz) ; Walchner, quartzose talc-
schist ; Jacquemont, gres schisteux ; Shepard includes it
under the head of mica-schist ; Tourney terms it quartz
rock or the f quartz of the mica slate? and indicates that
it may be a hornstone ; Yan Uxem even appears to have
considered it in South Carolina as a variety of Greissen.

Jukes describes Itacolumite as being a genuine un-
altered sandstone, more or less micaceous like other sand-
stones, but the mica in worn spangles, not in connected
flakes.

Varieties.

(a) COMMON ITACOLTTMITE. \ Firm, not flexible, resembling a
GEMEINER ITAKOLUMIT. (Germ.) L fi rm and somewhat fissile sand-

ITACOLUMITE COMMTJN. (Fr.) )

(6) FLEXIBLE ITACOLUMITE. . Usually very fine-grained, and

j? thin lars or Plates-very
flexible.
(c) CONGLOMERATIC ITACOLUMITE. , ^ , . , , ,

CONGLOMERATARTIGER ITAKOLUMIT. (Germ.)\ Enclosing rounded peb-
ITACOLUMITE GRENu. (Fr.) ( bles of quartz.

Yon Eschwege informs us that in the Brazils itaco-
lumite forms whole systems of strata of great thickness,
extending for several hundred miles in length. The
mountain Itacolumi, near Villa Eica (5,400 feet high),
consists almost entirely of this rock. Shepard and
Lieber found it very extensively developed in North
and South Carolina, where it generally lies between lime-

CHLORITE, ETC., GROUP. 249

stone and clay-slate, and contains subordinate layers or
beds of talc-schist, ferruginous mica-schist, itabirite, ca-
tawbarite, and fine-grained limestone. Von Helmersen
and Hofmann also found the rock in the Ural Moun-
tains ; Von Eschwege in Portugal ; Schulz in Spain ;
Gergens in the slate region of the Rhine.

References.

v. Eschwege. Beitr. z. Gebirgskunde von Brasilien, 1832, p. 174.
O. Lieber, Gangstudien, vol. iii. p. 323.
Shepard, Report of South Carolina, 1854.
Schuh, Bullet, de la Soc. ge*ol. de la France, 1834, p. 416.
Gergens, in v. L. u. Br. Jahrb. 1841, p. 566.
Lucas (as early as 1815) found diamonds in it in the Brazils.

Nouveau dictionnaire d'hist. nat., art. Diamant. The same

fact was confirmed by Heusser and Claraz, in the Zeitschr.

d. d. geol. Ges. 1859, vol. xi. p. 448.
r. Hnmboldt. Gisement des Roches dans les deux Hemispheres.

p. 89.

v. Martius, Reise in Brasilien, vol. ii.
Clausen, Bullet, de 1'Acad. de Bruxelles, 1841.
Walchner, Handbuch d. Geognosie, p. 38.
Tourney, Report on the Geology of South Carolina, 1848, p. 6.
Jacquemont, Voyage dans 1'Inde.

CHLORITE, TALC, AND HORNBLENDE GROUP.

These rocks have been severally termed Chlorite-schist,
Talc-schist, and Hornblende-schist, from the prevalence of
those respective minerals in their composition.

In their chemical composition they resemble the basic
rather than the acidic igneous rocks ; that is, they contain
more magnesia and lime, and, for the most part, less silica
than the acidic rocks.

They occur as subordinate beds in the mica-schist, or
they entirely take the place of mica-schist in some for-
mations.

Serpentine might also be included in this group, by
reason of its chemical and frequently also its geological
character. Nevertheless, inasmuch as serpentine often
occurs under other and very different geological rela-
tions (appearing as the product of igneous rocks), we
prefer to class that rock separately amongst the special
rock formations.

By introducing this group of rocks between the mica-
schists and the argillaceous mica-schists, we interrupt a

250 CRYSTALLINE SCHISTS.

connected series of transition between those two groups,
but such interruption only represents similar inter-
ruptions actually occurring in nature.

26. CHLOKITE-SCHIST and POTSl?ONE.

CHLORITSCHIEFER imd TOPFSTEIN. (Germ.)

SCHISTE CHLORITIQTJE. (Fr.}

A schistose aggregate of chlorite, usually combined with
quartz, sometimes also with felspar, mica, and talc.
It has a greenish colour and scaly appearance.

Spec. grav. . ? ',''- ~- . r V 2-7 2-8
Contains silica V . \ /. * ' 31 42 p. c.

The principal mass of this rock is composed of chlorite
of green or blackish-green colour and greyish-green
streak. It is usually of coarsely foliated texture and soft.
The quartz sometimes transfuses the whole mass, and so
makes the rock hard ; sometimes it only occurs in the
form of thin scattered lamina?, lenticular or irregular
swellings ; sometimes again it traverses the rock in thin
veins. Felspar, mica, or talc are only occasionally to be
distinctly recognised as ingredients ; many other minerals
are, however, found as accessories, and often in very per-
fectly formed crystals ; the most frequent of these are mag-
netic iron-ore, garnet, talcspar, actinolite, and tourmaline.

This rock forms transitions into talc-schist, protogine
gneiss, mica-schist, clay -mica-schist, and slaty serpentine,
and it often lies in alternate strata with these rocks. It
is widely spread in the central chain of the Alps, is very
characteristically developed in the Fichtelgebirge, near
Schwarzbach, Wiersberg, &c., and also in the Eastern
Carpathians. It very often contains subordinate beds
or layers of magnetic iron-ore, ferruginous mica-schist,
copper and iron pyrites, granular limestone, quartz, &c.
It is usually very distinctly stratified.

Chlorite-schist can scarcely be divided into separate
varieties, which have not found a place under other heads,
but some analogous rocks may be annexed to it, and may
almost take the place of varieties.

(a) THE CHLORITE-SCHIST OF HARTHATT (near Chemnitz). The
principal mass of this rock consists of an imperfectly foliated
chlorite-schist of dark-green colour, traversed by many layers
and veins of quartz. Numerous very distinct yellow spots appear

CHLORITE, ETC., GROUP. 251

prominently arranged in certain zones. These were for a long
time taken to be flakes of talc. A. Knop has, however, ana-
lysed this rock more narrowly, and discovered that the spots
do not consist of talc, but mostly of a yellowish-green micaceous
substance, a kind of pinite, which, however, itself appears
to be a product of transmutation from oligoclase (or labra-
dorite), and in many places has preserved its crystalline form
and distinct cleavage. Strange to say, these felspar crystals, in
the process of their transmutation into aggregates of mica,
have even changed their outward shape, and accommodated
themselves somewhat to the foliated texture of the rock. This
rock frequently contains some pyrites, brownspar, and titanic iron
as accessories/ It divides into plates or wood-like fibres. It forms
subordinate beds in the clay-mica-schist of the same district. ^

(6) CHLORITOID SCHIST is the name given by Hunt to a certain
dark-coloured schist, very extensively developed in Canada,
principally consisting of chloritoid, a mineral closely allied to
chlorite, and also to ottrelite.

LAVKZOTEIN, it is only rarely foliated. Specific gra-
I vity, 2-8 (?) ; content of silfca, 30-60
) p. c. (?) The mass is greenish-grey to
blackish ; its streak greenish-white. It is soft, sectile, and
quite infusible. It sometimes contains mica, calcspar, dolo-
mite, and magnetic iron-ore or iron pyrites scattered through
its mass, and hence it sometimes effervesces on the applica-
tion of acid. In fire it loses 7'21 per cent, of its weight, pro-
bably in consequence of the large quantity of water which it
contains (sometimes as much as 11 per cent/).

This rock is easily manufactured into firebricks and fire-
proof utensils. It is found in very characteristic form in the
Alps, together with serpentine as a subordinate stratum in
chlorite-schist, and it forms transition states into serpentine
Chiavenna, Drontheim in Norway (?), Boston in Massachusetts,
Potton in Canada.

References.

Varrentrapp, Poggend. Annalen, 1849, vol. xlviii. p. 189.
Knop, Progr. der Chemnitzer Gewerbschule, 1856. (?) Neues

Jahrb. f. Min. 1863, p. 808.

finish, on Chloritoid Slate, v. Leonhard's Jahrbuch, 1861, p. 574.
Delesse (Potstone), Bullet, de la Soc. ge*oL de France, 1857, [2]

vol. xiv. p. 281.
Studer (Potstone), Bibl. univers. de Geneve, 1856, [4] p. 213.

27. TALC-SCHIST.

TALKSCHIEFER. (Germ.)

TALCSCHISTE (STEASCHISTE, Brongniarf). (jFV.)

A schistose aggregate of talc, usually combined with some
quartz or sometimes with felspar, yellowish or greenish
colour and soft greasy feel.

252 CRYSTALLINE SCHISTS.

Spec, grav 2-62-8

Contains silica 50 57 p. c. ; at Zebernick, in Hungary, only
27-6 j at Hinterbriihl, even 62-1.

The principal mass of these rocks consists of talc, of
light-yellow, yellowish-green, or greenish-grey colour,
with a mother-of-pearl varying to resinous lustre. As
it contains less silica than the mineral talc (which has 64
per cent.), we may infer that some chlorite enters into its
composition.

It contains little quartz ; and only in grains, flat lenti-
cular particles, laminae, or irregularly shaped masses, or
irregular veins, all subordinate as to size and quantity.

Felspar is only to be seen in delicate particles scattered
here and there ; it is not more frequent than several of
the following accessory minerals : chlorite, mica, talcspar,
garnet, actinolite, asbestos, magnetic iron-ore, and iron
pyrites. This rock forms transitions into chlorite-schist,
clay-slate, mica-schist, and protogine-gneiss.

Varieties,
(a) COMMON TALC-SCHIST. ] Not unusual in the Alps. At

GEMEINER TALKSCHIEFER. (Germ.) [ Ochsenkopf, near Schwarzen-
TAX.CSCHISTE COMHUN. (Fr.) j berg ^ the Erzgebirge, a

variety (with corundum) occurs imbedded between strata of
mica-schist.

(6) LISTWENITE is the name which has been given to a variety in
the Ural Mountains, which contains much quartz combined
with talcspar or calcspar, and from that combination assumes
a somewhat granular slaty texture. The same rock, at Bere-
sowsk is displaced and penetrated by veins of Beresite, which
are again penetrated with quartz veins containing some gold.

(c) DOLERINE is the name given by Jurine to a talc-schist with es-
sential ingredients of felspar and chlorite, and according to
Favre this rock is extensively spread in the Pennine Alps.

Talc-schist is almost always stratified, and forms alter-
nating beds with other crystalline schists.

References.

G. Rose, on Liswanit, Reise n. d. Ural, vol. ii. p. 537.
Jurine, on Dolerine, in the Journ. des Mines, vol. xix. p. 374.
Favre, on Dolerine, in v. L. u. Br. Jahrb. 1849, p. 41.
Scheerer, Analyse des Talksch. von Fahlun, in Poggend. Ann.

1851, vol. Ixxxiv. p. 345.
Richter, Anal. d. Talksch. von Gastein, in Poggend. Amu 1851,

vol. Ixxxiv. p. 368.

CHLORITE, ETC., GROUP. 253

Ferjentsik, Anal d. Talksch. v. Zebernick, in Jahrb. d. geol.

Reichsanst. 1856, p. 807.
Raysky, Anal. d. Talksch. v. Hinterbriinl, in Jahrb. d. geol.

Reichsanst. 1854, p. 642.

28. HORNBLENDE-SCHIST and HORNBLENDE
ROCK.

HORNBLENDESCHIEFER und HORNBLENDEFELS, AMPHIBOLTT.

(Germ.)
SCHISTE AMPHIBOLIQUE et AMPHIBOLITHE, Brvngniart. (Fr.)

A schistose or fine-grained to compact rock, consisting
chiefly of hornblende, combined with small quantities
of felspar, quartz, or brown mica. Always dark-green
to black.

Spec, gray , 3 3'1

Contains silica ..... 48 54 p. c.

This rock is most usually of foliated texture. Its prin-
cipal mass is granular and sometimes also fibrous, and
consists of common dark-green hornblende as its principal
ingredient, with which some felspar, quartz, or mica is
usually combined. If the latter are present in considerable
quantity, then transitions take place into diorite (6), dio-
rite-schist (No. 6 a), or syenite-gneiss (No. 22). As
accessories there also occur garnet, pistacite, iron pyrites,
magnetic iron-ore, &c.

The varieties of prevailing schistose character are usu-
ally imbedded between strata of other crystalline schists,
to which they clearly belong, and into which they pass
over by grades of transition.

They also sometimes pass into rocks not of a fissile tex-
ture, such as hardly can be classed with the argillaceous
schists, and which may perhaps be of igneous (eruptive)
origin, especially as they form transitions into diorite.

Varieties of Texture.

(a) HORNBLENDE-SCHIST. ] Usually thickly foliated, and at

HoRNBLENDisscHiEFEB. (Germ.) L the same time fibrous : this tex-
SCHIKTK AMPHXBOLXQUE. (Fr.) J ture being ^j^ V ^ pft _

rallel position of fibres of hornblende of various thickness.
Quartz and felspar occur as a part of the compound of the
principal rock, but also in nests or veins. This rock is often
found (subordinate) in strata of gneiss, mica-schist, and
<-lil< rite-schist ; e. jr., Miltitz, near Meissen, and the district of
Munchberg in the Fichtelgebirge.

254 CEYSTALLINE SCHISTS.

At Hanover in North America hornblende-schist is found,
containing large dodecahedrons of garnet.

(6) HORNBLENDE EocK. ] Without fissile texture. E. g. in

HORNBLENDEFELS. (Germ.) \ the district of Hof in the Fichtel-
AMPHIBO. ^ J gebirge.

Variety in Composition.

STRAHLSTEIN oder ACTING- (therefore entirely fibrous, otherwise
LITHSCHIEFER. (Germ.) f . , ,., , ,, J-. -. . , ' -^

J just like hornblende-schist. Found to

the south of Oberwiesenthal in the Erzgebirge ; also at Clau-
sen in the Tyrol.

We might also include eklogite (No. 44) under this
head, but as it is at least doubtful if its origin be that of
the metamorphic schists, and as it belongs to the rocks of
exceptional character, and by 'reason of its richness in
garnets may be conveniently placed with the other garnet
rocks, we have so classed it.

References.

Eischof's Geologie (1st edition) contains almost the only de-
tailed account of hornblende-schist. See II. p. 130.
On actinolite-schist, see Reuss in v. L. u. JBr. Jahrb. 1840, p. 41.

SCHISTS INDISTINCTLY CRYSTALLINE.

These form the connecting link between the extreme
metamorphic crystalline schists (especially gneiss and the
mica-schists) and the clay-slate and slate-clay rocks,
which latter being much less changed are still distinctly
sedimentary. We therefore term them argillaceous mica-
schists.

29. ARGILLACEOUS MICA-SCHIST, PHYL-

LITE.

THONGLIMMERSCHIEFER, PHYLLIT, URTHONSCHIEFER. (Germ.}
PHYLLADE, D'Aubuissoti. (Fr.}

A schistose aggregate in which mica is usually to be recog-
nised as the chief ingredient^ or in which the peculiar
structure of mica rocks is apparent. Sometimes the
whole mass appears homogeneous, differing only from
clay-slate by its superior lustre.

Spec, grav 2-62-8

Contains silica . . . . 45 74 p. c.

Argillaceous mica-schist is but a transition state between

ARGILLACEOUS MICA-SCHIST. 255

mica-schist and clay-slate, as is apparent from its passing
over into both these rocks. We might term it an imperfect
mica-schist or a very much transformed and somewhat
crystallised clay-slate. Its chemical analysis also agrees
with this definition. But its chemical composition varies
as much as that of mica-schist or clay-slate. Its principal
ingredients are always quartz and mica (or some mineral
of the same character as mica), but the quantitative pro-
portions of these ingredients are very different in different
rocks. With these principal ingredients are associated
chlorite, talc, felspar, hornblende, garnet, &c., which occa-
sion transitions into chlorite-schist, talc-schist, hornblende-
schist, and gneiss.

The colour of these rocks is usually grey, greenish, or
bluish-grey, but sometimes yellowish, reddish, brownish,
and violet. Their lustre varies between the mother-of-
pearl, the silky, and the half metallic. They always have
a distinctly fissile texture, but not by any means a perfect
cleavage. Sometimes they show fine parallel foldings, or
sometimes there occurs a second fissile texture obliquely
traversing the principal direction, occasioning a rough
fibrous cleavage. When the slaty cleavage is perfect, it
is usually not parallel to the stratification.

In the apparently homogeneous principal mass, we dis-
cover grains or irregular lenticular swellings or masses
of quartz, or else veins of quartz or flakes of mica (or
sericite), chlorite, talc, hornblende, felspar, chiastolite,
andalusite, iron pyrites, magnetic iron-ore, or graphite.
When these minerals are considerable in quantity, there
arise varieties in composition. But these varieties are
not peculiar to this rock ; they are necessarily repeated in
mica-schist, as well as in clay-slate.

Varieties in Texture.
(a) COMMON ARGILLACEOUS MICA-SCHIST.

IKINKK THOXGLIMMERSCHIEFKR. (Germ.)
PHYLLADB COMMUN (SATIXE). (Fr.)

(6) FOLDED OR CONTORTED.

I.IKTKR THOXGLIMMERSCHIEFER. (Germ,)

HOLZARTIGER THOXGLIMMERSCHIEFER. (Germ.)

(d) VERY MUCH CONTORTED.

SKHR VERWORREX SCHIEFRIGER oder WULSTIGER THOXGLIMMERSCHIEFER.

(Germ.)
PUBSE, FROIS8E. (Fr.)

256 CRYSTALLINE SCHISTS.

0) NODULAR SCHIST. j Which we also enumerate below, as

(} * a iet ? in comosition.

a iet ? in compositi

Varieties in Composition.
(f) RICH IN MICA. \

Gu ?R. T So M ' Transition into mica-schist.

MICACE. (/>.)

Forms transitions into quartz.

SCHIEFKR. (Germ.) schist.

QTJARTZEUX.

(A) CH CHZmscH E H THoxGUMMEB-l Fo n ? transitions into chloritic

SCHIEFER. (Germ.) SChlStS.

CHLORITIQUE. (Fr.)
(t) TALCOSE. )

TALKIGER THONGLQIMER- I Forming a transition into talc-schist.

SCHIEPER. (Germ.)
TALQUEUX. (Fr.)

(k) A VARIETY CONTAINING HORNBLENDE.

HORNBLENDEHALTIGER THONGLIMMERSCHTKFER. (Germ.)

(I) A VARIETY CONTAINING FELSPAR. x Form i nff a transition
FELSPATHHALTIGERTHONGLIMMERSCHIEFER. I J

(Germ.) j into gneiss.

(6?erm.) j into garnet-mica-schist.

GRENATIFERE. (/V.) /

(w) SERICITE-SCHIST. ] The name given by List to a variety

SERICITSCHIEFER. (Germ.) Iwhose principal mass consists of seri-
SCHISTEASERICITE. (j fr.)) cite ( green m i cace ous mineral, re-
sembling damourite, with a silky lustre, see ante, p. 23), and
which usually also contains quartz and felspar (albite according
to List). The colour of this rock in the Taunus, where it is
very extensively developed, is greenish with green and yellow
spots, or violet. It is often penetrated by veins which contain
quartz and albite. The very considerable quantity of alkalies
which it contains, especially of potash, is remarkable. List
further distinguishes three sub-varieties, according to their
colour.

(a) Violet, very soft, with thin slaty cleavage. Spec. grav.

2-88.

(j8) Green, harder, with thick slaty cleavage (folded), with
little albite, and a microscopic quantity of magnetic
iron-ore. Spec. grav. 2-79.
(y) Spotted, soft ; often decomposed j with much albite and

quartz. Spec. grav. 2-68.

(o) OTTRELITE-SCHIST. ] The principal mass foliated, and usually

OTTRELITSCHIEFER. (Germ.) I grey. It contains greenish laminae of

SCHISM loirsft. (/v.) Jott^^te. This variety is frequently

found in the Ardennes. It has also been discovered by Giim-

bel in the district of Ebnat in Bavaria.

(p) CHIASTOLITE-SCHIST. \ The mass is slaty, and usually

CHIASTOUTHSCHIEFER. (Germ.) ( dark-coloured. It contains many
SCHISTE MACI^ERE. (Fr.) j crygtals of cMastolite disseminated

ARGILLACEOUS MICA-SCHIST. 257

through it in the most opposite directions. The chiastolite-
schist (which also forms a variety of clay-slate) is found on
the contact margins of plutonic igneous rocks, e. g. next to
irranite. Near Gefrees in the Fichtelgebirge. Also abundant
about Skiddaw, Cumberland.

(q) No DULAR or SPOTTED SCHIST. \ This schist contains small con-
KNOTENSCHIEFER, FLECK- oder cretions of different structure,
ScHS C xo^SS R ou ((7 ^^. hardness, and colour to that of
(Fr.) J the general mass. They are, for

the most part, harder and darker, and they either form small
knots or only spots with indistinct margin ; sometimes they
resemble the currants in a fruit-pudding, hence their different
names. Their composition has not vet been determined with
accuracy by the various mineralogical chemical analyses which
they have undergone, according to which they have been suc-
cessively taken for a kind of fahlunite, for hornblende, serpen-
tine, chiastolite, or andalusite. It is very possible that at
different places they are somewhat differently composed. In
reference to their origin, it is of special interest that according
to the careful investigations of Carius, the schist with nodules
does not differ in the quality or proportionate quantity of its
ingredients from the same schist without nodules farther re-
moved from the contact, so that no new substance appears to
have been added to form those concretions, but they appear
rather to have arisen from a new arrangement of the previously
existing ingredients. At the margin of the granite in the
AVestern Erzgebirge and Voigtland, these nodular schists are
very frequent, and are observed there just as much in the clay-
mica-schist as in the ordinary clay-slate. A similar appearance
occurs at Wechselburg in Saxony, in a rock which is decidedly
mica-schist.

(r) ALUM-SCHIST. \ This schist contains much carbon, and

ALAUNSCHIEFER. (Germ.) I i s thereby rendered black. Pyrites is
semen ALUMIXEUX. (Fr.) j alwayg mixed with it in fine particles,
through whose decomposition alum and iron- vitriol are formed.
In the case of this variety, we can only decide from the
bedding whether it belongs to argillaceous mica-schist or tq
clay-slate, for the carbon which it contains thoroughly oblite-
rates the slender landmarks by which the difference might
otherwise be established. It is characteristic of most of the
alum-schists, that they are of very much contorted or displaced
texture, and are frequently pervaded by irregular swollen-
shaped fragments of quartz and lustrous but bent laminae
(mica), and sometimes also lenticular concretions of bitu-
minous limestone or anthraconite. lieichenbach in Voigtland.

(s) CARBONACEOUS SCHIST, BLACK CHALK. ] In the case of this
ZKICHNENSCHIKKER, SCHWARZE KREIDE. (Germ.) I yarietv verv rich in

J carbon, we can only

determine by its bedding whether it belongs to argillaceous
mica-schist or to clay-slate. It is a quartzless and very soft
slate, which, from admixture of carbon, is of a black colour,
and also imparts a black streak, so that it may be used for
S

258 CRYSTALLINE SCHISTS.

drawing or writing. Ludwigstadt in the Thuringian Forest,
where it belongs to clay-slate.

All the above-mentioned varieties in composition are
equally applicable to the ordinary clay-slate as to the
argillaceous mica-schist, and we shall therefore have to
enumerate them again when we come to consider that
rock, but our previous descriptions will suffice for both.

Argillaceous mica-schist is usually also distinctly stra-
tified in addition to its foliated texture, which, as already
said, is not parallel to the stratification ; otherwise, as to
its bedding and extent, it exactly resembles mica-schist,
with this only difference, that it more usually than that
rock is interstratified with the oldest sedimentary and dis-
tinctly fossiliferous rocks.

By the name of argillaceous mica-schist we do but
seek to establish a stage of transmutation between clay-
slate proper and mica-schist.

References.
Frick, Pleischl, Sauvage, and Kjeridf have contributed various

analyses to Poggend. Ann. 1835, vol. xxxv. p. 188 ; in the

Journ. f. prakt. Chemie, 1844, vol. xxxi. p. 45 ; and 1855,

vol. Ixv. p. 192.
List, on Sericitschiefer, in the Jahrb. d. Vereins f. Naturk. in

the Duchy of Nassau, 1850, No. 6, p. 128.
Lipold, on Sericitschiefer in the Alps, Jahrb. d. geol. Keichs-

anst. 1854, pp. 201 and 359.
Giimbel, on Ottrelitschiefer, inCorresp.-Bl. d. zool. mineral. Ver.

z. Regensburg, 1853, p. 53, and on Phyllit, in the same,

1854, p. 12.

Naumann, on Knotenschiefer, Erlauter. z. geogn. Karte v. Sach-
sen, 1838, No. II. p. 264, and 1845, No. V. p. 50.

Kersten, on Knotenschiefer, in Journ. f. prakt. Chemie, vol. xxxi.
p. 108.

Carius, on Knotenschiefer, in the Annalen d. Chemie. u. Pharm.

1855, vol. xciv. p. 45; and in v. L. u. Br. Jahrb. 1856,
p. 595.

Miiller, on Knotenschiefer, in the Berg- u. Hiittenm. Zeitung,

1858, p. 107.
Durocher, on Chiastolith and Knotenschiefer, in Bullet, de la

Soc. geol. de la France, 1846, vol. iii. p. 546.

259

CHAPTER III.

SEDIMENTARY AND FRAGMENTAL ROCKS.

ALL sedimentary rocks are stratified ; or at least, their
beds lie one above the other in parallel planes. The
greater part consists of the debris of older rocks mechani-
cally washed together and deposited from a state of sus-
pension in water. A few only are the result of chemical
precipitate of mineral substances. Many contain organic
remains (fossils) more or less distinct ; some consist entirely
of such.

As a consequence of their origin, the sedimentary rocks
are rarely of genuine crystalline conformation. Some,
however, which appear to be actual chemical precipitates
from aqueous solutions, such as gypsum and rock-salt,
usually possess a crystalline structure.

Following the different origin of these rocks, we may
divide them into

(a) Mechanical deposits.

(b) Chemical precipitates.

(a) Phytogenic, caused by the accumulation of vege-
table matter.
($) Zoogenic, caused by the accumulation of animal

remains.

The minerals which chiefly predominate in sedimentary
rocks are not the same as those which are most abundant
in the igneous and the metamorphic rocks. We find in
the sedimentary rocks little or no felspar, hornblende, or
pyroxene. The following are those which occur with
greatest frequency : Quartz, which in general terms we
may call the most abundant mineral of the earth ; clay
(itself, however, a compound rather than a distinct mine-
ral) ; carbonates of lime and magnesia, as calcspar (lime-
stone) and dolomite ; sulphate of lime, as gypsum and
anhydrite ; chloride of sodium, as rock-salt ; finally, coal
and iron-ores.

Gypsum (or anhydrite), salt, coal, and iron, usually
form distinct and separate beds of comparatively small

8 2

260 SEDIMENTARY ROCKS.

extent : the principal and most important sedimentary
rocks are composed chiefly of the first-named of the above
minerals, quartz, clay, and carbonate of lime (or magne-
sia). They may be accordingly divided into argillaceous
rocks, calcareous rocks, and quartzose rocks. The marl
rocks occupy an intermediate place between the calca-
reous and argillaceous. The quartzose rocks may be
divided into the arenaceous or sandstones, and the con-
glomerates, to which we may add certain other fragmental
rocks containing less quartz, usually termed tufa or tuff.

The material for all these several rocks was mostly
derived from the disintegration of more ancient previously
existing rocks. The igneous rocks, by the decay of their
felspar, hornblende, augite, and mica, have supplied the
following substances towards the formation of the sedi-
mentary rocks : argillaceous mud, and weak solutions
of lime, magnesia, silica, potash, soda, oxide of iron;
their quartz has furnished grains of sand ; in some cases
their mica has remained undecomposed, and is found as
mica in minute Iamina3 in the sedimentary rocks. The
older sedimentary rocks have also in process of time be-
come disintegrated, and have furnished similar materials
to form the more recent, and every solid rock has at times
furnished pebbles, and other fragments for the formation
of conglomerates.

The several sedimentary deposits have been divided
into so-called formations, according to the order of their
superposition, and consequently of their age, and these
again have been gathered into groups, which answer to
longer periods of deposit.

It may therefore be useful here to present the following

TABLE OF GEOLOGICAL PERIODS.*

C Recent Formations of every kind.

'^ | Mud, sand, gravel, calcareous and volcanic tuff, coral reefs,

bog iron-ore, turf, peat, &c., guano, infusorial beds.

Pleistocene) or Post-Pliocene Formation.

Diluvial or glacial deposits, loam and breccias of bone-
caverns, brick-earth and fluviatile loam or loess, valley
gravels, bog iron-ore, calcareous tuff, coral-reefs, &c. '

* In different countries these are somewhat differently divided and
named.

SEDIMENTARY ROCKS.

261

ENGLAND.

Pleiocene Formations.

Red and coralline crag.

Miocene Formations.
Absent in England.

Eocene Formations.

Fluvio-marine strata of Isle of

Wight and Hampshire.
Bagshot series.

London clay and Bognor beds.
Plastic clay or Woolwich and

Reading beds.
Thanetbeds. .f

Cretaceous Formations.

White chalk with flints.
White chalk without flints.
Chalk marl.
Upper greensand.
Gault.

f Lower greensand or neocomian.
\ Speeton clay.

Wealden beds, weald clay, and
Hastings sand.

Oolitic or Jurassic Formations.
Purbeck beds.
Portland beds.
Kimeridge clay.

Coral rag.

Oxford clay.

Cornbrash.

Forest marble and Great or

Bath oolite.
Fullers' earth.
Inferior oolite.
Upper lias sand and clay.
Marlstone or middle lias.
Lower lias clay and limestone.

Triassic Formations.

Penarth or Rhsetic beds.
Dolomitic conglomerate.
Red marls -with rock-salt and

gypsum.
White and brown sandstones

(waterstones) .
Red and mottled sandstones,

pebble-beds of conglomerate.

GERMANY.

Aralo-Caspian deposits.

Molasse formation of the Alps
Tegel, near Vienna.

Browncoal formation in North
Germany.

Nummuliten formation.
Flysch formation.

Maestricht beds.

Turonien, quadersand, planer.
Cenomanien.
Albien, aptien.
Hils-formation.

Deister formation.

White Jura.

Lithographic slate of Solen-
hofen.

Brown Jura.

Black Jura.

Keuper.

Koessen or Upper St. Cassian
beds.

Muschelkalk (absent in Eng-
land.
Buntsandstein.

262

SEDIMENTARY JIOCKS.

ENGLAND.

Dyas or Permian Formations.

Red marls and magnesian

limestone.
Lower sandstone.

Carboniferous Formations.
Coal-measures.
Millstone grit.
Carboniferous limestone
Lower limestone shale.

GERMANY.

Zechstein formation.

Kupferschiefer.

Rothliegendes.

Steinkohlen formation.

Flotzleerer sandstein.
Kohlenkalkstein.
Kohlen formation of Hai-
nichen, or kulm.

Devonian Formations {Old Red Sandstone).

Dartmouth slate group.
Plymouth group.
Liskeard or Ashburton

group.
Old red sandstone.

Cypridinenschiefer, or

Kramenzelstein.
Str5ngocephalen-Kalk.
Calceolaschiefer.
Spiriferen-Sandstein and

Schiefer.

Silurian Formations.

Ludlow group "j

Wenlock group >

May hill group J

Lower Llandovery beds 1

Caradoc sandstone and Bala beds I

Llandeilo flags

Lingula flags

Cambrian Formations.

Gritstone, sandstone, and slate, with few or no organic
remains.

Laurentian rocks of Canada and the north-west of Scotland.

Below the sedimentary rocks are usually found the
crystalline schists.

The entire series of formations is, however, never to be
found in any one locality.

The mere geological age of deposit does not inform us
of the nature of the rock, nor can we, on the other hand,
from the petrographic character arrive at its geological age.
Both attributes are to a certain extent independent of each
other. No kind of rock is restricted to any particular
period, and although there exist some very general differ-
ences between the rocks of recent and ancient deposit, yet
even these do not prevail universally.

ARGILLACEOUS GROUP. 263

ARGILLACEOUS GROUP.

The argillaceous rocks were originally nothing but
sediments of clayey mud, with some admixture of fine
quartz-sand, flakes of mica, hydrated oxide of iron, and
organic remains. These materials, by a slow process of
transmutation and mechanical consolidation, have ulti-
mately become solid rocks, some of them carboniferous or
bituminous.

The principal rocks of this group are clay-slate, argilla-
ceous shale, claystone, clay, and mud or silt (loess), with
their several varieties. To these we must also add the
marl rocks.

To arrange these rocks according to the order of their
origin and development, we should begin with the clay
and loess, from which (perhaps by the simple agency of
pressure) claystone, argillaceous shale, and clay-slate have
been successively formed ; the several varieties of these
rocks being occasioned by the accessory admixtures con-
tained in the original compound.

In the present treatise the order is inverted, and the
metamorphic rocks having been already described, we most
naturally pass first to those of the sedimentary rocks which
are nearest to them, i. e., the most changed, taking the
newer formations last.

We cannot draw a sharp distinction between argilla-
ceous mica-schist, clay-slate, and argillaceous shale, but
the extreme or ideal development of each of these stages
of transmutation has a marked character, distinct from the
others. Characteristic argillaceous mica-schist is still
somewhat crystalline ; clay-slate is not crystalline, and in
fracture it is dull, but yet firm, and has a perfect slaty
cleavage ; characteristic argillaceous shale, on the other
hand, is soft or flexible, separates along the lamination
instead of by slaty cleavage, and is more obviously an
earthy aggregate. Argillaceous mica-schist frequently
contains various crystalline accessory minerals, but genuine
clay-slate much more rarely, and of fewer kinds ; argil-
laceous shale at the most only occasionally contains some
pyrites.

30. CLAY-SLATE.

THONSCHIEFER. (Germ.}

SCHISTE ARGILEUX, SCHISTE ARDOISIER.

264 SEDIMENTARY ROCKS.

A compact fissile rock of a dull blue-grey ', bright red,
purple, green, or black colour ; consists chiefly of clay ;
sometimes with accessory admixtures of quartz, mica,
and other minerals.

The slaty cleavage is usually very perfect, and only
occasionally coincides with the original lamination of
the rock.

Spec. grav. . '.'".' . ... . 2-52-8
Contains silica . . .- .. v . 40 75

The characteristic feature of clay-slate as distinguished
.from other rocks of the argillaceous group is that its slaty
cleavage, frequently very perfect, is altogether inde-
pendent of its original bedding, although in some instances
(which we may regard as accidental) it coincides with the
original lamination. Whether this slaty cleavage is due to
pressure, or to some agency resembling the crystallising
force which has acted on smaller mineral masses, has been
a subject of debate since the time of Sedgwick, who first
called attention to this important phenomenon. It is a
question which is still unsettled, and which must probably
so remain for some time longer.

Varieties in Texture.

(a) COMMON CLAY-SLATE. ) With perfect or imperfect

GEMEIXER THONSCHIEFER. (Germ.) L cleavage, very variously CO-
SCHISTE ARGILEUX OOIUK. (Fr.) J loure( ^ ^ ^ ^ &c _

cessory minerals. It contains, e. g., quartz, in irregular masses
(or swellings), or lenticular masses, or in veins ; pyrites, in
crystals or nodules, &c. Sometimes its slaty cleavage is much
distorted. It is very frequent in all districts of the transition
period (greywacke) in Germany.

(&) ROOFING SLATE. \ The name given to the purest

DACHSCHIEFER und TAFEL- |_ varieties of clay-slate, whose cleav-

SCHIEFER. ((rerm.) t* i t ,1

SCHISTE ARDOISIER, (Fr.) a g e is very perfect and smooth,
' allowing of their being split into

very thin plates, which nevertheless retain a high degree of
firmness and solidity. A dark- coloured variety, containing an
admixture of carbon, is termed in Germany Tafelschiefer.

Roofing slate, with a view to its fitness for the purpose its
name indicates, should be free from accessory crystallised in-
gredients. North Wales, Lehsten in the Thuringian Forest, &c.
(c) PENCIL-SLATE, PINSILL \ A clay-slate of pure composition,
or PENCIL. f soft, but withal firm; separated or

* se P ara ^ le into pencils (the slaty clea-
vage crossing the planes of lamina-
tion), and used for writing on slate.

Found in North Wales, Sonnerberg in the Thuringian Forest,
and other slate districts.

ARGILLACEOUS GROUP. 265

Varieties in Composition.

(d) WHETSLATE, WHETSTONE, HONE/
OILSTONE, NOVACULITE.

WETZSCHIEFER. Germ.

SCHISTB 8IUCEUX (NOVACULAIRE), De

Charpentier. (Fr.)

This is a very highly sili-
ceous clay-slate, perfectly
compact and homogeneous.
Usually only indistinctly
of slaty cleavage, and its
fracture often conchoidal and even splintery. Used for sharpen-
ing knives and other instruments. E. g. Wales, Devonshire,
Katzhiitte in the Thuringian Forest.

0) CARBONACEOUS CLAY-SLATE. ) Passes into alum-schist and

Kon ( r SJ? ) CHER T 110 * 8011 11 - [ black chalk (Zeichnenschiefer),

SCHISTE HOUILLER. (Fr.) ' see p. 257, ante.

(/) ARENACEOUS CLAY-SLATE. ] Passes into argillaceous sand-

SAXUIGER THOXSCHIEFER (GRAU- \ stone. Bv the Germans it

WACKENSCHIETER). (Germ.) I j g frequ / ntly termed ^^

wacke-slate, from its occurrence in the transition or greywacke*
formations.

(g) MICACEOUS CLAY-SLATE. ) Differing from clay-

<-,UMMERREICHER THoxscHUFER. (Germ.) \ mica-schist, in that the

8CHI8TE MICACE (PAILLKTE). (Fr.)

dently only mechanically dispersed. This variety also passes
in Germany under the name of greywacke"-slate.
(A) CALCAREOUS CLAY-SLATE. ) Containing numerous lenti-

KALKKXOTIGER THONSCHIEFER (KRA- L cular or irregular nodules

j of limestone (which fre-

quently owe their origin to fossils) j passes over into nodular
limestone.

The varieties which we have already described under
the head of argillaceous mica-schist we find repeated in
the clay-slate, and accordingly we have : chlorite-slate,
talc-slate, sericite-slate, ottrelite-slate, chiastolite-slate,
nodular and spotted or mottled slate, alum-slate, and
carbonaceous slate.

Clay-slates are usually very distinctly stratified, although
their slaty cleavage does not in general correspond with
the planes of their stratification.

Clay-slates ar not confined to one geological period of
formation ; the genuine clay-slates, however, usually only
occur in the older formations, viz. the transition or grey-
wacke. In the newer formations shales are usually
found. Nevertheless there are exceptions to this rule;
in the Alps there occur genuine roofing slates, also com-
mon arenaceous and micaceous clay-slates (Grauwacken-
schiefer) belonging to the Chalk and even to the Tertiary
periods.

266 SEDIMENTARY ROCKS.

Geological Varieties.

(1) GLAEUS SLATE. \ A genuine clay-slate, in part a

MATTERERSCHTEFEK, Heer. [ roofing-slate, occurring in Switzer-

Scm^^iNE ( LUIS A* T ). l *> ^longing to e of tte ^
(Fr.) i tiary penods.

(2) CYPRIS SLATE. ) A clay-slate with ftmefiJMe, the

CYPRIDINERSCHIEFER. (Germ.) \ upper member of the Devonian
SCHIKTE A CYPRIDINE. (/y-.) J formation at the Rhine and Hartz.

(3) WISSENBACH SLATE. ] A c i ay . s i at e of the Devonian

WlSSENBACHERSCHIEFER. (Germ.) f f , 4.1 TT

SCHISTE DE WISSBNBACH. (Fr.) ) aUttUOUn at the Hartz.

(4) CALCEOLA SLATE. ) A Mack and sometimes calcareous

CALCEOLASCHIEFER. (Germ.) [ clay-slate of the Devonian forma-
SCHISTE 1 CALCEOLES. (Fr.) ) tion at the Hartz.

(5) GREYWACKE-SLATE. ) An arenaceous and usually mi-

GRAUWACKEXSCHIEFER. (Germ.) \ caceous clay-slate of the transi-
GRAUWACKE SCHISTEUSE. (Fr.) > t ion periods.

(6) GBAPTOLITE SLATE. ^ ,4 clay-slate or sometimes a si-

GRAPTOLITENSCHXEFER. (Germ.) I liceous slate (lydian-stone) With
SCHISTE 1 GRAPTOLTTES. (Fr.) ) Graptolites, belonging to the Si-
lurian formation.

31. AKGILLACEOUS SHALE, SHALE.

SCHIEFEETHON. (Germ.)
AEGILE SCHISTEUSE. (Fr.)

A laminated clay-rock ivhose fissile texture is due to its
original stratification and not to slaty cleavage. In
other respects, similar to clay-slate. Shale and clay-
slate pass into each other, and many shales show a
tendency more or less decided towards a slaty cleav-
age. Shales are usually more recent, geologically
speaking, than the genuine clay-slates.

Varieties in Texture.

(a) COMMON ARGILLACEOUS SHALE. \ Is only a softer, less firm,
GEMEINER SCHIEFERTHON. (Germ.) I and more earthy variety of
ARGILE SCHISTEUSE COMMUNE. (Fr.) j clay . slate w ' lih ^t its cleav-

age, but laminated according to the plane of its original
deposition. It is often mixed with quartz grains and with
flakes of mica.

(&) SCHIEFERLETTEN (of German geologists) is a modification of
the usual argillaceous shale in which the clay is still some-
what moist, and the rock therefore is somewhat plastic and
greasy^

ARGILLACEOUS GROUP. 267

Varieties in Composition.

BITUMINOSER SCHIEFERTHON. (Germ.) r ing into Brandschiefer.
SCHISTS BITUMINEUX. (Fr.) '

(d) CARBONACEOUS SHALE, CARBONIFEROUS] Dark-grey to black,

SHALE (BATT or BASS, KELVE). I from admixture of
KOHLENSCHIEFER. (Germ.) r carbonaceous matter ;

SCHISTE HOUIIXER. (Fr.) ) frequentlyarenaceou ;

or micaceous. When many fossil plants occur in the rock, it is
sometimes called in Germany Krauterschiefer. This rock es-
pecially belongs to the Coal formation.

(e) VARIEGATED SHALE. ] Yellow, red, violet, or green,

BUNTER ^^ 1 ON ^^ [ according to the different degrees
rm '') of oxidation of the iron which it

contains.
(/) ARENACEOUS SHALE. 1 Passing into argillaceous sand-

SANIUGER SCHIEFERTHON. (Germ.) \ stone

SCHMTTE 8ABLEUX. (Fr.)

(ff) MICACEOUS SHALE. ) Corresponding with mi-

GLIMMERREICHER SCHIEFERTHON. (Germ.) \ caceous clay-slate.

SCHISTE MICAC6. (Fr.) J

(A) CALCAREOUS SHALE. ) Slightly effervescing with

MBRGELIGER SCHIEFERTHON. (Germ.) f ac id . passing into calca-
IMARNBUX ' *** ] reous slate*"

Geological Varieties.

(1) FLYSCH, an arenaceous and micaceous shale, sometimes approach-

ing the state of a clay-slate. Eocene in the Alps.

(2) FUCOIDAL SHALE ) With remains of Fucoids. Eocene

FUCOIDENSCHIEFER. (Germ.) \ and older in the Alns and Can>a-

SCHI8TE X FUCOlDES. (Fr.) I tjjjjjjjg

(3) ROETH, a term employed by the German geologists for a varie-

gated arenaceous shale, which occurs imbedded between the
Sluschelkalk and variegated sandstone (Thuringia) .

* 'The colliers' and quanymen's terms for shale are bind, blue-
bind, metal, plate, &c. ; when very fine and containing a large pro-
portion of carbonaceous matter, the collier calls it batt or bass, the
geologist carbonaceous (or bituminous) shale, and the coal merchant
often slate. In Scotland the collier's term for shale appears to be
blaes or blues, the shale being often bluish-grey ; when lumpy they
are called lipev blaes. Black argillaceous shales or " batts " are
called " dauks. Fekes or grey fekes seem to be sandy shales such as
would be called rockbinds in South Staffordshire (see Williams'
" Mineral Kingdom.") In the South of Ireland, carbonaceous shale is
called kilve, and indurated slaty shale is termed '' pinsill " or "pencil,"
as it is often used for slate pencils.' Jukes.

268 SEDIMENTARY KOCKS.

(4) WERFNER SCHIEFER, a shale, usually arenaceous and micaceous,

occurs in the Alps in strata, which there represent the varie-
gated sandstone formation.

(5) CARBONIFEROUS SHALE or SLATE. ] This is a geological

KOHLENSCHIEFER (KRAUTExscHiEFEB). (Germ.) \ designation applied

j to all shales of the

Coal formation, whether or not they actually contain carbon
(see ante, e).

(6) POSIDONOMYA SHALE. ~\ A dark-coloured shale of the

POSIDONOMYENSCHIEFER. (Germ.) I Carboniferous formation (that
SCHISTEXPOSIDONOMYES. (FT* J of the Lias formation is a bitu-
minous marl- slate).

(7) WENLOCK SHALE. Silurian formation, England.

The following relate chiefly to chemical analysis of clay-
slates and argillaceous shales.

References.

O. L. Erdmann, Thonschiefer in Thiiringen, Joum. f. techn.

Chem. 1832, vol. xiii. p. 114.
Frick, Thonsch. in Thiir. am Harz in Westphalen, Poggend.

Ann. 1835, vol. xxxv. p. 193.
Pteischly Thonsch. in Bohmen, Journal f. prakt. Chemie, 1844,

vol. xxxi. p. 45.
Delesse, Thonsch. in den Vogesen, Ann. des Mines, 1847, [4]

vol. xii. p. 303 ; 1853, [5] vol. iii. p. 747 j and Bullet, de la Soc.

ge"ol., [2] vol. x. p. 562.
Forchhammer, Thonsch. v. Christiania, Oversigt over det K.

Danske Vidensk Silesk Forhandlinger, 1844, p. 91. Journ.

f. prakt. Chem. 1845, vol. xxxvi. p. 394 ; and on Bornholm,

Berzelius, Jahresber. 1844, [25] p. 405.
Dahl, Thonsch. bei Christiania, Nyt. Mag. f. Naturv. 1848, [5]

p. 317.
Kjerulf, Thonsch. bei Christiania, in Christianias Silurb. 1855,

p. 34.
Jwanhow. Thonsch. bei Christiania, Mem. Acad. de St. Petersb.

1859, [6] p. 325.
Wilson, Thonsch. in Schweden, Phil. Mag. 1855, [4] p. 114 ;

p. 417.
K. v. Hauer, Thonsch. in Steiermark, Jahrb. d. geol. Eeichs-

anst. 1854, pp. 362 and 869.

J^r/ew^'&,Weriher Schiefer, Jahrb. d. geol. Reichs. 1855, p. 852.
Sauvaqe, Ardennenschiefer, Ann. des Mines, 1845, [4] vol. vii.

p. 420.
List, Tannusschiefer, Ann. d. Chem. u. Pharm. 1852, vol.

Ixxxi. pp. 192 to 260.
Kayser, Thonsch. von Clausthal, v. L. u. Br. Jahrbuch, 1850,

p. 682.
Schnabel, Amelung and v. d. Mark, in den Verhandl. d. naturh.

Ver. d. pr. Rheinlande, 1851, pp. 10, 56, and 127 j 1853, p.

127; and 1855, p. 122.
Rissc, Geol. Beschr. d. Gegend von Baden, 1861, p. 47.

ARGILLACEOUS GROUP. 269

32. CLAY and LOAM.

THON und LEHM. (Germ.)
ARGILE. (Fr.)

These are earthy deposits chiefly consisting of clay, and
when moist are more or less plastic.

Loam or lehm is a word of German origin ; between it
and clay there is no sharp distinction. The purest and
therefore the most plastic varieties are called clay (also
potter's clay or pipe-clay). They are usually white or
greyish-blue, but sometimes yellow, red, or greenish,
or (if containing carbon) even black. Those varieties
which contain much fine sand and hydrated oxide of iron
are called loam (in Germany, Lehm), and the iron usually
gives them a yellow or brownish colour.

Varieties in Composition.

(a) CLAY. ) The purest varieties are white or light-bluish

THON. (Germ.) j. grey, and are very plastic. These are called
" ) potter's clay or pipe-clay. Those containing
much silica or fine sand are called fire-clay ; those containing
bitumen, bituminous clay; some are variously coloured by
different oxides of iron, and are then termed variegated clay.
(6) LOAM. ) Contains more or less sand, flakes of mica, and

LEHM. (Germ.) j guc h like admixtures ; is coloured by hydrated
oxide of iron, and is therefore less plastic than clay, almost
earthy and yellow or brown in colour. It sometimes even con-
tains small crystals of felspar (Glasurlehm of the Germans) ;
or it contains particles of lime, marly loam (Mergellehm) j or
nodules of marl (Losskindeln) ; nodules of pyrites (Kiesknollen) ;
microscopic shells, &c. If it contains a very large proportion
of hydrated oxide of iron, then it passes over into yellow ochre
(Gelberde), which is used as a colouring matter,
(c) SALIFEROUS CLAY. j A clav containing chloride of sodium,
SALZTHON. (Germ.) L sometimes with distinct grains or crys-
ARGILK BALiFfcRE. (fr.)J ^ of this salt ; usually occurs together
with rock-salt.

The following are the geological terms of certain
clays :

(1) LOESS, or DILUVIAL LOAM. \ Frequently somewhat calcareous

L^L^ILUVIKN. (Fr.) J ^th marly nodules (Losskindeln).

(2) TILE OR BRICK EARTH. A Miocene or Neogene deposit of clay

TKOBL. (Germ.) i i n the Vienna basin.

(3) BROWNCOAL CLAY. > Usually white. Miocene in North-

BRAUNKOIILENTHON. (Germ.) j ern Germany.

270 SEDIMENTARY BOOKS.

(4) SEPTARIAN CLAY. > Containing septaria of lime, in North-

SEPTARIENTHON. (Germ.)} ern Germany Miocene (or Eocene).

(5) BARTON CLAY. Hampshire, Eocene.

(6) BOGNOR CLAY. Eocene of the Hampshire basin.
7 LONDON CLAY. Eocene in the London basin.

(*.,} Eocene in the Paris basin.
(9) HILS CLAY. \ In the Hils formation (Wealden) of West-

HILSTHON. (Germ.) J phalia.

(10) SPEETON CLAY, in the Lower Greensand formation of England.

(11) WEALD CLAY. ) In the Wealden formation of Sussex.

ARGILE WEALDIENNE. (Fr.) )

(12) ORNATEN-THON. (Germ.) With Ammonites ornatus in the Jura

formation of Swabia.

(13) OPALINUS-THON. (Germ.) With Ammonites opalinus in the

Brown Jura of Swabia.

(14) KIMERIDGE CLAY. \ In the Jura f ormat ion of England.

ARGILE KIMMERIDIENNE. (Fr.) >

(16) AMALTHEEN-THON. (Germ.) With Ammonites amaltheus, in the

Lias formation of Swabia.

(17) TURNERI-THON. (Germ.) In the Lias formation of Swabia.

(18) MIACYTEN-THON. (Germ.) Containing Myacites, and frequently

also remains of plants, the lowest branch of the Keuper forma-
tion in Thuringia.

As clay loses its plasticity when subjected to a strong
pressure, especially if accompanied by high temperature,
the plastic clays are chiefly confined to the recent forma-
tions : the older clays have doubtless been converted into
argillaceous shale, clay-slate, or claystone. There can
be no doubt that all these rocks originally were mud
deposits.

Literary references on the subject of clay and loam
appear unnecessary.

33. CLAYSTONE and HARDENED CLAY.

THONSTEIN, oder VERHARTETER THON. (Germ.)

A compact and tolerably solid mass, chiefly consisting of
clay, not slaty ; its fracture earthy ; very variously
coloured.

The rock designated by this name is not always an
actual sediment, but sometimes a product of the disintegra-
tion of felsitic rock. The nature of its origin is generally
only to be determined by its geological position and sur-

MARL GROUP. 271

roundings. The sedimentary claystones are always stra-
tified sometimes in very thin layers, white, yellowish
grey, red-brown, greenish, or brownish, sometimes with
variegated stripes or spotted. They sometimes contain
nodules of pyrites, flakes of mica, impressions of plants, or
petrified parts of plants.

We have already said that the distinction between the
sedimentary claystones and certain weathered felsitic
rocks is sometimes difficult. In like manner it is fre-
quently difficult to distinguish the former from certain
tuff rocks, e. g. from porphyry-tuff, which indeed is very
often called claystone, especially in England; but the
genuine sedimentary clay rock seems to have at least as
good a title to the name.

MARLS.

These are closely allied to the clays, standing between
them and the limestones. They are in fact compounds of
clay and carbonate of lime, and also sometimes contain
carbonate of magnesia ; they likewise frequently contain
fine particles of quartz, flakes of mica, oxide of iron,
bitumen, or carbon. According to their state or texture,
they may be divided into the slaty, the compact, and the
earthy varieties ; according to the predominance of one or
other of their ingredients, they may be further divided
into the calcareous, dolomitic, arenaceous, micaceous, fer-
ruginous, and bituminous. Of carbon they only contain
very subordinate quantities, serving as a dark colouring
matter.

The original state of these rocks, like that of the clays,
was a muddy sediment somewhat more various in its
character than in the case of those rocks. The same
process of pressure has consolidated them into firm, rocky,
slaty, or sometimes bituminous masses.

The processes of animal and vegetable life have even
participated in the formation of some of these rocks to the
extent of contributing their calcareous and bituminous
ingredients. The calcareous ingredients often show traces
with the microscope of organic remains. Marls as well
as clays occur in the deposits of almost every geological
period; and as to the di Terence between those of different

272 SEDIMENTARY ROCKS.

periods, we can only in general terms say that the older
varieties are usually slaty or fissile, whereas in the more
recent deposits earthy varieties more frequently occur,
but this is by no means a rule without exception.

34. MAKL.

MERGEL. (Germ.)
MARNE. (Fr.)

A compound of clay and lime, earthy, compact, or fissile,
usually soft; crumbles on exposure to air, effervesces
with acid.

Marl is a compound of clay and lime or dolomite, but
its ingredients are blended together and cannot be dis-
tinguished except by chemical agents. The proportion
of lime or dolomite varies from 10 to about 50 per cent.
Outside of these limits the rock ceases to be marl, and does
not crumble on exposure to the air. It will then either
be a clay or a limestone.

The most frequent colour is grey, but marl is sometimes
yellow, brown, red, violet, bluish, or greenish.

Varieties in Texture.
(a) MARL-SHALE. ] In fresh state very similar to argil-

MERGELSCHIEFER. (Germ.) laceous shale, but crumbles on ex-

MAKNEUX. (Fr.)

tains much quartz, sand, mica, or bitumen.

(b) COMPACT MARL, or MAKLSTONE. ] Without distinct fissile

DICHTER MERGEL, VERHARTETER MERGEL, [ s l at y structure, similar to

STEIKMERGEL, Oder MERGELSTEIN. ^^ ^ f^ fo

MARNE COMPACTS. (Fr.) > pieces on exposure to the

air. Admixtures of quartz and mica or bitumen similar to
marl-shale. A modification of compact marl, separates into
small conical concretions (cone in cone). Germ. Tuten- Merc/el.

ERDIGER MERGEL. (Germ.) > is not plastic when wet. Its ingre-
dients are the same as those of the other marls.

Varieties in Composition.

(d) CALCAREOTTS MARL. ) with much carbonate of lime in its

KSfSSiB^P composition.

(e) DOLOMITIC MARL. ) With dolomite, and usually also

DOLOMITMERGEL. (Germ.) r with carbonate of lime. The dif-
MARNE MAGXESIEK.NE. (Fr.) > f erenceg be tween (d) and (e) can
only be determined by chemical analysis.

MARL GROUP. 273

(/) ARGILLACEOUS MARL. ) With little carbonate of lime or dolo-
THOXMEKOKL. (Germ.) \ mite : forms transitions into clay, clay-
MAIIXK AHGILEUSE. (Fr.) J 8t()ne) or ^^0^ shale.

O) ARENACEOUS MARL. ^

SAM.MKHGEL. (Germ.) \ With much sand.
MAKNE SABLEUSE. (Fr.) )

(A) MICACEOUS MARL. % .

GLIMMERMERGEL. (Germ.) \ Contains mucn mica.
MARXE MICACEE. (Fr.) )

(t) BITUMINOUS MARL. ) Usually in the form of shale, al-

BiTUMiNosr.u MKIUJEL. (Germ.) j ways dark-coloured by reason
MARXK r.m M.NK, SK. (Fr.) > of ^ bitumen> sometimes even

black. To this belong the so-called Oelschiefer (oil-slate) and

Kupferschiefer (cupiferous slate) of the Germans ; the latter is

distinguished by the quantity of copper which it contains.

(A') GLAUCONITE MARL. } With much glauconite in its compo-

GLAUKOXITMERGEL. (Germ.) L 8 ition, and by it coloured green. The

MAKXK GU.UCOXIEUSE. (Fr.) | ^^'^^ when examined under

the microscope, appear mostly to proceed from the shells of
microscopic Foraminiferae.

(0 GYPSEOUS MARL. , A marl penetrated by stringy veins of
*!??&. J gyP^m, or thin laminae of the same.

Besides the above-mentioned varieties of composition,
some marls have been named according to their geological
position ; e. g. :
(1) SUB-APENNINE MARL. )

SUBAI-KXNINKX-MEROBL. (Germ.) \ Pliocene in Upper Italy.
NE SUBAPEXXIXE. Fr. '

MABNE SUBAPEXXIXE. (Fr.)

(2) CYRENIAN MARL. ) With many Gyrenes : Miocene, in

)
( ^- } I

the Mayence basin.

(3) CHALK MARL. ) i n the Chalk formations of England

Ki;KinKMEHQEU (Germ.) . TTVoct^linlifl.

CRAIE MARNEUSE. (Fr.) ) and Westphalia.

(4) PLAXER MARL. \ In the Quadersandstone formations of

PLAXEIIMEIIOEL. (Germ.) > Saxony and Bohemia.

(5) FOLKESTONE MARL. I j n the Gault formation of England.

MARXE DC GAULT. (Fr.) >

(6) SPEETON MARL, belonging to the Lower Greensand formation of

England.

(7) FOREST MARL. | j n t h e Lias formation of England.

CALCAIRE MARNEUX. (Fr.) >

(8) LIAS SLATE. ) A bituminous marl-slate of the Lias

LIASSCHIEFER. (Germ.) I formation, sometimes called Oel-

8CHIOTE L1A8IQUE. (Fr.)

(9) JURENSIS MARL. ) With Ammonites jurensis, in the

JIKEXSIS-MEROEL. (Germ.) } Lias formation of Swabia.

(10) POSIDONOMYA SLATE. ) A dark bituminous marl-elate

PosiDoxoMTEN-ScraEFER. (Germ.) i- of the Lias formation of Swa-

J bia, with many Posidonomya.
T

274 SEDIMENTARY ROCKS.

(11) NTJMMISMALIA MARL. \ With Terebratula mtmnwmalis,

NUMMISMALIS-MERGEL. (Germ.) I in the Lias formation of Swabia.

(12) BELEMNITE MAEL. ) A dark bituminous marl -slate in

BELEMNITENSCHIEFER. (Germ.) [ the Lias formation of Swabia,
MARNE A BELEMNITES. (Fr.) J with many ^ tefc

(13) SPOTTED MARL, or ALGAU SLATE. \ In the formation

FLECKENMERGEL, oder ALGAUSCHIEFER. (Germ.) ]" Q the Northern
Alps answering to the uppermost Lias.

(14) KETJPER MARL. ) Chiefly variegated in colour, fre-

f7 quently withypsun,

(15) PARTNACH SLATE, or BACTRILLIAN SLATE. ) A marl formation

PARTNACHSCHIEFER oder BACTRILLIENSCHLEFER. L -with thick slaty

J cleavage, which in

the Northern Alps is found in part answering to the Keuper
formation.

(16) BITUMINOUS MARL-SLATE. ) Of the Zechstein forma-

BITUMINOSER MERGELSCHTEFER. (Germ.) j tion of Thuringia.

(17) COPPER SLATE. \ Is a bituminous marl-slate of the

KUPFERSCHIEFER. (Germ.) j Zechstein formation of Thuringia, in
which various sulphurous compounds of metals are contained.
These sulphur compounds, besides their copper, contain iron,
silver, lead, cobalt, nickel, &c.

It will hardly be necessary to add anything respecting
the occurrence of marl in nature, nor to refer to literature
on the subject.

LIMESTONE GKOTJP.

(Limestone, Dolomite, Gypsum, Anhydrite.)
Pure limestone is an aggregate of particles of calcspar :
it therefore consists of carbonate of lime. Pure dolomite
or magnesian limestone is an aggregate of particles of the
mineral dolomite or bitter-spar : it is therefore a car-
bonate of lime and of magnesia. Gypsum is a sulphate
of lime combined with water ; anhydrite is gypsum with-
out water.

Rocks consisting of pure limestone or dolomite rarely
occur in nature. What we chiefly find are rocks of in-
termediate character, which we may regard as transitions
between the two extremes ; in other words, all limestones
are more or less magnesian, probably consisting of an
intimate compound of the two minerals, calcspar and
bitterspar.

These rocks likewise usually contain other admixtures
in small quantities ; e. g. clay, silica, oxides of iron, or
bitumen. The presence of such minerals occasions many

LIMESTONE GROUP. 275

varieties in colour as well as composition ; there are also
many modifications in texture, so that the limestones
present us with many very dissimilar rocks.

It is not always easy or possible without analysis to dis-
tinguish limestone from dolomite, even if pure, still less
to determine the various rocks of intermediate character.
Many rocks have been long held to be limestone which
later chemical analysis has shown to be dolomite. Never-
theless, the distinction is important enough to be pre-
served, although it may be difficult always to apply it.*
We are compelled to create an arbitrary boundary by
determining how great a percentage of magnesia should
entitle a rock to be called a dolomite. The mineral dolo-
mite contains about 45*7 per cent, carbonate of magnesia
to 54-3 per cent, carbonate of lime. We may therefore
halve the 45*7 per cent., and say that all rocks contain-
ing more than 23 per cent, carbonate of magnesia should
be called dolomites, and those containing less than that
amount retain the name of limestones. Some such divi-
sion must be agreed on for purposes of classification,
although otherwise of little scientific value.

The general difference between characteristic forms of
the two rocks may be briefly stated as follows :

LIMESTONE. DOLOMITE.

Hardness . . 3' Hardness .... 3-5
Spec, jrrav. . 2'6 2-8 Spec. grav. . . . . 2*8 2*9
Crystalline-granular lime- The crystalline-granular and sac-
stone seldom occurs except charoid varieties of dolomite occur in
between strata of crystalline sedimentary formations, as well as
schists. between strata of crystalline schists.
Many beds of limestone of Sometimes these varieties pulverise
Silurian and carboniferous age to a crystalline sand,
are coarsely crystalline ; as are,
also, the limestone of some coral

(reefs and some stalagmites.

Very often compact. Seldom quite compact.

Frequently oolitic. Probably never oolitic.

Lustre, when crystalline, Lustre, when crystalline, vitreous

vitreous. to pearly.

* The quicksilver mines of Idria are in dolomite rock, which
adjoins and is intersected by limestone in many places; and the
difference between the two rocks is there very important, as the ore
is confined to the dolomite, none being ever found in the limestone.
TRANSLATOR.

T 2

276 SEDIMENTARY ROCKS.

LIMESTONE. DOLOMITE.

Effervesces strongly with Solid portions of the rock do not
acid. effervesce with acid. The powder

effervesces, especially if heated.

Its powder, when heated When its powder is heated on
before the blowpipe on pla- platinum foil, before the blowpipe, it
tinum foil, adheres together. tumefies and does not gelatinise.

The circumstances under which these two rocks occur
in nature are very similar. They both occur in a crys-
talline-granular state, imbedded between strata of meta-
morphic schists ; they both form strata in formations of
various geological periods ; but in the sedimentary forma-
tions the dolomites are frequently also found in a crys-
talline-granular state, whereas the limestones, though
often crystalline, are almost always compact, earthy, or
oolitic. Deposits of genuine dolomites are never formed
by springs, but limestones frequently. Limestones, again,
are more frequently fossiliferous, and they are also more
usually distinctly stratified than dolomites.

Gypsum and anhydrite are not so extensively developed
as limestone and dolomite; they are prevalent only in
distinctly sedimentary formations, and are usually crystal-
line, seldom distinctly stratified, seldom fossiliferous. They
are often accompanied by rock-salt. In general they are
much more free from foreign ingredients than either lime-
stone or dolomite.

35. LIMESTONE.

KALKSTEIN. (Germ.')
CALCAIRE. (.Fr.)

A crystalline-granular, compact, earthy, or oolitic ag-
gregate of calcspar ; effervesces strongly icith acid;
easily scratched with the knife.

Spec, grav 2-62-8.

Pure limestone consists of 56 per cent, lime and 44
per cent, carbonic acid. It seldom occurs so pure in
nature, but is usually more or less intimately combined
with dolomite, alumina, silica, peroxide and protoxide of
iron, bitumen, or carbon. By these ingredients its pro-
perties undergo alteration, and there arise distinct varie-
ties in composition when their quantity is considerable.
The texture of the limestone rocks is likewise various,
and gives rise to other varieties, to many of which sepa-

LIMESTONE GROUP. 277

rate names attach. Many limestones consist entirely, and
others partially, of the calcareous shells of animals ; and
it is very possible that this is the case with several whose
original structure is no longer apparent. There are other
limestones which are undoubtedly the product of chemical
precipitate of carbonate of lime from aqueous solutions ;
and some that are the result of consolidation of calcareous
mud proceeding from the mechanical disintegration of
older limestones.

In appearance, many limestones and dolomites much
resemble some siliceous rocks, or compact felsitic rocks,
or gypsum. But from these they may easily be distin-
guished by the difference of their hardness, and by their
effervescence with acids.

Varieties in Texture.

(a) GRANULAR LIMESTONE. ] Including marble. A granular

KORXIGER KALKSTEIX. (Germ.) I aggregate of distinct individual
CALCAIRE SACCHAROSE. (Fr.) f ^J^ ^^ of calcspar .

The grains vary in size from the almost invisibly small (fine-
grained compact varieties) to the size of a nut (coarse-
grained). Most usually the colour is white, but sometimes
yellowish-grey, reddish, greenish, bluish, and even black. By
admixture of dolomite it passes into magnesian limestone
and dolomite. Granular limestone also contains other ad-
mixtures, especially in its crystalline state, and these are then
porphyritically disposed, as, for instance, mica, chlorite, talc,
hornblende, pyroxene, garnet, vesuvian, felspar, chondrodite,
couzeranite, chiastolite, epidote, zircon, titanite, spinel, corun-
dum, quartz, fluor-spar, apatite, magnetic iron-ore, iron pyrites,
zinc-blende, galena, copper pyrites, anthracite, and graphite.
The rock also contains geodes, nests, or veins, with fully
developed crystals of calcspar, aragonite, bitter-spar (dolomite),
asbestus, serpentine, &c.

The following special varieties of granular limestone are
occasioned by the occurrence of some of the above minerals in
considerable quantity and characteristic form.

(</) CTPOLLINO. ] A granular limestone rich in

CIPOLLES. (Germ.) L m i ca , by which a slaty texture is

UN " ( r.) j sometimes occasioned; goes over

into calcareous mica-schist. Zaunhaus, near Alten-

berg in Saxony.

(/3) AXTHRACONITE. ] The name given by v. Moll to

A-NTHHAKOMT, Von L certain carbonaceous black granu-

j lar limestones, which are usually

only found in the form of nesta, lentils, or veins in

other rocks. To this class belongs the Lucullite of the

ancients.

278 SEDIMENTARY ROCKS.

(y) OPHICALCITE. ] The name given by Brong-

OPHICALCIT. (Germ.) I n i ar t to a compound of lime-

o?^, Brongniart. J Bton e and serpentine j itstex-

ture granular to compact.

This is the Verde Antique of archaeologists.

((^) CALCIPHYRE. j The name given by Brong-

CALCIPHYR. (Germ.) I n i ar t to a compound of gra-

Brongniart.

pyroxene, or felspar, usually
porphyritic.

HEMITREKE. ] A granular compound of

HEMTTBEN. (Germ.) I limestone, hornblende, and

(y), ((>), and () are probably
always contact formations.

() HISLOPITE. ) The name given by Samuel Haugh-

HISLOPIT. (Germ.) ] ton to a granular limestone occur-
ring at Takli in the East Indies.

Granular limestone is of irregular massive structure ; it like-
wise usually shows distinct traces of stratification, sometimes
also a fissile texture j it most usually occurs in subordinate beds
between strata of crystalline schists, and is frequently itself the
product of metamorphosis from compact sedimentary deposits
of limestone. The form of its beds is sometimes very irregular,
they assume a swollen shape, or resemble the dykes or veins of
igneous rocks. It would seem as if the limestone, in the pro-
cess of transmutation, had become softer than the surrounding
schist, and that its mass had consequently been squeezed into
the breaches and clefts of the latter. This appearance may
be observed at Miltitz near Meissen, and at Auerbach near
Heidelberg.

In England and Ireland beds of crystalline limestone occur
variously interstratified with the compact limestones of the
carboniferous limestone series through a thickness of from 2,000
to 3,000 feet.

Granular limestone is also found at the margin of those

igneous rocks which have broken through the compact or earthy

limestones. Such may be observed at the Kaiserstuhl in

Breisgau, in County Antrim and Island of Rathlin, Ireland.

(6) COMPACT LIMESTONE. ) The particles of calcspar are in-

DICHTER KALKSTEIN. (Germ.) \ visibly small, and the mass there-

CAI^AIKE COMPACTE. (Fr.) I

fore to be compact> Its

fracture is conch oidal, or splintery, or dull. Its prevailing
colour is grey or yellowish ; it varies, however, to white,
blue, green, red, brown, and even black. Some varieties are
variegated, spotted, or veined, like marble. The following ac-
cessory ingredients are usually intimately blended with the
general mass, viz., dolomite, clay, silica, oxide of iron, bitu-
men, or carbon. If these only occur in small quantity, they
can hardly be recognised, but if their quantity be consider-
able, then distinct varieties of the rock are occasioned, such as
the folio wing:

LIMESTONE GROUP. 279

(rr) DOLOMITIC.

DOLOMITISCHER DICHTER KALKSTKIN. (Germ.)
MAGNESIEN. (Fr.)

63) BITUMINOUS. ) Fetid limestone, swine-

STINKSTELV, STINKKALK, (Germ.) [ stones, always dark-
CAIX.AIRE BITUMINEUX. (Fr.) J co i ouredj and emitting
a bituminous smell when rubbed.

(:/) ARGILLACEOUS or MARLY LIMESTONE. ) With consider-

MERGELKALKSTEIX. (Germ.) [

CAIX^RE ARGI^UX ou MARKED. (Fr.) J
grey, and in fracture dull, almost earthy.

(<>) FERRUGINOUS LIMESTONE. ) Very rich in hydrated
EISENKALKOTEIN. (Germ.) I ox j(fe of iron, which im-
CAXCAIRE FEBKUGINEUX. (Fr.) -,

) parts a brown colour to

the rock.

(*) CHERTT LIMESTONE, or SILICEOUS "I Combined with si-
LIMESTONE. I lica, and therefore

SSSJSSfeM I harder * t ordi -

1 nary limestone,
Very frequently traversed by veins of chert or hornstone.

In all the varieties of these compact limestones there occur,
occasionally, veins, seams, nodules, or nests of calcspar, horn-
stoie (chert), or flint.

Jukes remarks, l Almost all large masses of limestone have
ther Hints or siliceous concretions. These are frequently called
cheft, as in the carboniferous limestone (see post, p. 351), where
the lodules and layers of chert exactly resemble the flints in
chall. Even the tertiary limestones round Paris have their
flints the menilite of that locality being nothing but a siliceous
concrtion (see post, p. 349), found in the calcaire St. Ouen, and
possity other places. Pure siliceous concretions occur even in
the freshwater limestones and gypsum beds of Montmartre.
This invariable, or nearly invariable, accompaniment of lime-
stone jid siliceous deposits, those siliceous parts having a
chemial and not a mechanical formation, strengthens the hypo-
thesis f the organic origin of both, as previously described.
The silca diffused through the calcareous mud, of which the
limestoie was composed, has sometimes remained so diffused
instead -f separating as nodules or layers, producing a cherty or
siliceouslirnestone.'

Page ,ays, ' To the percolation of water charged with car-
bonic aci, we owe the production of rottenstone from beds
of siliceas limestone, the carbonated waters dissolving the
limy porion, and leaving the light porous siliceous residuum
which fonis the rottenstone of commerce.'

The ccnpact limestones are usually distinctly stratified, and
are founc associated with other sedimentary rocks of almost
every age
(e) EARTHY LMESTONES. ) Chalk (in part). Rough to the

ERDIGER KLKOTEIN. (Germ.) I f ee l ; friable ; the white chalk

CAHAIM .UYEUX. (Fr.) J ^^ fapjfa fa ^^ fr my

body agabst which it is rubbed. In chalk the particles consist

280 SEDIMENTARY ROCKS.

of very minute shells of Foraminifera, Polythalamiae, &c., which
may "be recognised under the microscope.

These minute shells constitute a fine earthy mass, in which
larger fossils are likewise found, as well as nodules and layers
of flint or chert, grains of glauconite, or of sand and other mine-
ral substances. The following sub varieties may be named:

() WHITE CHALK.

WEISSE KREIDE. (Germ.)
CRAIE BLANCHE. (Fr.)

(/3) GLAUCONITIC CHALK.

GLAUKOxmscHE KREIDE. (Germ.)
CRAIE GLAUCONIEUSE. (Fr.)

(y) ARENACEOUS SANDSTONE. \ Consisting of remains of

SANDIGER KALKSTEIN. (Germ.) L shells. These earthy and

CALCAIRE ARENACE. {Fr.) J distiuc tly ZOO genic rocks

are more frequent in recent than in old formations.

We may presume that in the older formations they

have been metamorphosed into compact limestone.

(d) OOLITIC LIMESTONE, OOLITE, ROESTONE,^ This variety is en-

PEASTONE, or PISOLITE. tirely composed of

OOLTTHISCHER KALKSTEIX, OOLITH, ROGENSTEIN, f Sma ll anc [ alniOSt

EBBSKSsmif, oder PISOLITE. (Germ.) ""(, . f "- t f

CALCAIRE OOLITHIQUE, CALCAIRE PISOLITHIQUE. J spneneal grams, Irom
( Fr <) the size of a millet-

seed to that of a pea or larger. This granular texture is very
different from the crystalline granular. The single round
grains usually lie close together, but this is not always the
case; they are sometimes wide apart, connected by a com-
pact matrix indeed they are always held together by a matrix.
The individual grains are often of compact structure, more
usually, however, of radial texture; sometimes both radial
and concentric in alternate coats, with a nucleus of foreign
substance, such as a grain of sand; sometimes they are
nothing but fossils. The geological position of these oolites
is identical with that of the compact limestones. The genuine
peastone is, however, an exception. It is (e. g. Carlsbad)
evidently a formation from a spring of water holding in solution
carbonate of lime (see p. 94), and it moreover consists of
aragonite and not calcspar. Jukes remarks, 'Its peculiar struc-
ture gives to oolite the character of a freestone, working easily
in any direction, whence its value as a building stone. Bath
stone, Portland stone, Caen stone are well-known examples of
oolitic limestone.'

The pea-grit of Cheltenham is a marine formation, one of
the oolites, only the spherical nodules are somewhat irregular
and elliptical in shape.

(e) NODULAR LIMESTONE. ] This variety consists entirely of

KNOTENKALKSTEIX. (Germ.) I sma ll compact nodules or irregular
CALCAIRE XODULEUX. (Fr.) 11 . r ., -, -, -,

' J swellings, united and bound to-
gether by a compact limestone mass, or by a matrix of marl or
clay-slate. Its composition, as well as its texture, there-
fore, presents varieties :

(a) NODULES OF LIMESTONE IN LIME-)

STONE or MARL MATRIX. I At Partenkirchen

KALKKXOTEX ix KALK oder MERGEL. f in Bavaria.
(Germ.)

LIMESTONE GROUP. 281

(/3) KRAMEXZELSTEDT. I Nodules of lime in a matrix

KRAMEXZELSTEIN. (Germ.) > O f clay-slate, hence the rock

itself is somewhat slaty. These nodules sometimes

are nothing else than indistinct fossils. Polwand, near

Saalfeld.

(/) SLATY LIMESTONE. ) This is, however, usually not

SCHIEFRIGER KALKOTEIN. (Germ.) I o f genuine slaty texture or
J cleavage, but only a thin strati-
fication (lamination) presenting a slaty appearance ; thus, e. g.,
at Solenhofen in Bavaria, where a finely laminated limestone
is even used for roof-slating.
(g) POROUS LIMESTONE. ) -IT,

POROSER KALKOTEIX. (Germ.) \ We here distinguish between

CALCAIHE CAVEUXEUX. (Fr.) '

() SPONGY LIMESTONE, APHRITE.) Very extensively de-

SCIIAUMKALK Oder MEHLBATZEX. L veloped in the Mu-

j schelkalk formation of
Thuringia, and

(/5) LIMESTONE TUFF, GALCA-) A deposit from springs,

REOUS TUFF. I usually porous by reason of

KALKTUFF. (Germ.) \ j^s orioin as an incrustation

TUF CALCAIRE. (Fr.)

(A) GEODIC LIMESTONE. ] With numerous sparry ca-

DRUSIGER KALKSTEIN. (Germ.) I ^ties of crystallised calcspar,

j brownspar, and the like.

(*) CELLULAR LIMESTONE, or ROUGH j With numerous angular

LIMESTONE. I cells or holes. These latter

ZELLEXKALK oder RAUHKALK. (Germ.) I are sometimes occasioned

CALCAIRE CELLULEUX. (Fr.) ) ^ ^ decfty Qr ^^e^

of fragments enclosed in the rocks, in which case the porosity
of the rock is only at the surface.

(&) BRECCIA-LIMESTONE, or LIMESTONES Fragments of limestone

BRECCIA. I cemented together by

BUIX CIKXKALK oder KALKBREcciE ; TnttM- r limestone. The partial

MER und RUIXEX-MAIOIOR. (Germ.) I i j n ' -t

BRECHE CAWAIRK. (Fr.) ) weakening or decay of

these fragments some-
times causes a cellular tissue on the surface of the rock.
(/) STYLOLITE LIMESTONE. ) Names given by Ger-

STYLOLITHEXKALK und NAOELKALK. (Germ.) [ man geologists to cer-
CAIXAIBE A STYLOLITES. (Fr.) j tftin c J t Umestones

which show peculiar striped jointings, so-called stylolites, or

are made up of small conical or wedge-shaped pieces.

(m) FIBROUS LIMESTONE ] To this variety we may reckon

FASERIGER KALKSTEIN, FASER- I the calc-sinter and aragonite-

CAIQUE r^Sci (Fr.) I sinter, formed by the dripping of

' water contaimng lime m solution,

e. g. at Carlsbad in Bohemia. There also occur seams or layers
of fibrous limestone between beds of marl, which have clearly
some other origin. Stalactitic calc-sinter is frequently sparry
and not fibrous, but as it is a subordinate formation we include
it here because of its origin.

Over and above the varieties in texture and composi-

2S2 SEDIMENTARY ROCKS.

tion which we have enumerated, limestone is very various
in its geological character, and especially in the nature of
the fossils which it contains. The geological varieties are
not of distinct lithological character, but they never-
theless deserve a brief enumeration, as they sometimes
acquire local importance. They are only to be distin-
guished with certainty by means of their fossils ; we will
arrange them as nearly as possible according to their
respective ages.

Geological Varieties.

(1) LIMESTONE TUFF, CAL- \ Usually a porous friable deposit from

CAREOUS TUFF. I springs, and containing many remains

KALKTUFF. (Germ.) rf rdirnta imd imriid

TUP CALCAIRE. (Fr.) ' OI P lants ana animals.

(2) TRAVERTINE. \ A formation in Italy similar to calc-tuff,

TRAVERTIN. (Germ.) I <but usually more compact, hard, and
TRAVERTIN. (Fr.) j sem i-crystalline.' See Bristow's Glossary,

(3) CORAL EEEFS. \

KORALLENRIFFE. (Germ.) \ In tropical seas.
CALCAIRE CORALLIEN. (Fr.) )

(4) FRESHWATER LIMESTONE. \ Containing freshwater shells.

SUSSWASSERKALK. (Germ) < Freshwater limestones have com-

t_/ALCAIRE D EAU DOUCK ^LA- I - i / /

CUSTRE). (Fr.) i monly a peculiarity of aspect from

which their origin may sometimes be suspected, even before
examining their palseontological contents or petrological rela-
tions. They are generally of a very smooth texture, and either
dull white or pale grey ; their fracture only slightly conchoidal,
rarely splintery, but often soft and earthy.' -Jukes.

(5) STEPPE LIMESTONE. \ A very recent semi-marine brackish

STEPPENKALK. (Germ.) J limestone deposit. In Southern Russia.

(6) LEITHA LIMESTONE. \ A tertiary limestone in the Leitha Moun-

LEITHAKALK. (Germ.) ) tains, with corals and marine shells.

(7) LITORINELLA LIMESTONE. \ In the Mayence basin, con-

LITTORINELLENKALK. (Germ.) taining numerous Paludinte.

CALCAIRE A LITTORINELLES. (Fr.)

(8) CERITHITJM LIMESTONE. ) j n the Mayence basin, with many

CERITHIENKALK. (Germ.) f r> pri - f j )1 - f}
CALCAIRE A CERITES. (Fr.) >

(9) CALCAIRE GROSSIER (Grobkalk), sandy, and full of fossil shells.

Eocene in the Paris basin.

(10) NUMMTJLITIC LIMESTONE. \ Consisting almost exclusively

NUMMULITENKALK. (Germ.) \ of Nmnmulites. Eocene; very

CALCAIKE A NUMMULITES. (Fr.) j extensively deve loped in the

South of Europe.

' The nummulitic formation, with its characteristic fossils,
plays a far more conspicuous part than any other tertiary group
in the solid framework of the earthy crust, whether in Europe,
Asia, or Africa. It often attains a thickness of many thousand
feet, and extends from the Alps to the Carpathians, and is in
full force in the North of Africa, as, for example, in Algeria

LIMESTONE GKOUP. 283

and Morocco. It has also been traced from Egypt, where it was
larjjrelv quarried of old for the building of the Pyramids, into
Asia Minor, and across Persia, by Bagdad, to the mouths of the
Indus. It occurs not only in Cutch, but in the mountain ranges
which separate Scinde from Persia, and which form the principal
passes to Cabul ; and it has been followed still farther east-
ward into India, as far as Eastern Bengal and the frontiers of
China.' Page.

(11) ORBITOIPAL LIMESTONE. ) 'As the nummulitic limestone

CALCAIHE X ORBITOLITES. (Fr.) } seems characteristic of the old
world, so the orbitoidal limestone seems characteristic of the
new, mountain masses full 300 feet in thickness, and almost
wholly made up of Orbitoides, occurring near Suggsville, in
North America, and apparently in the same, or nearly the same,
geological horizon.' Page.

(12) MAJOLICA, a white compact limestone.

( 13) SCAGLIA, a red limestone, in the Alps.

(14) OSTRJSA LIMESTONE. \ ? u \\ O f Qstraa. Eocene ; occurs

cSSS^SSi (Fr.) I to the north of Kusstein, in Tyrol.

(15) UPPER AND LOWER CHALK. \ Nearly white. The upper and

KKEIDEKALK, KREIDE. (Germ.) f principal branch of the Chalk
formation in England, containing many flints.

' Chalk flints occur as rounded nodular masses of very irre-
gular and sometimes fantastic shape, and of all sizes, up to a foot
in diameter. They are commonly white outside, but internally
are of various shades of black or brown, sometimes passing into
white. They have sometimes concentric bands of black and
white colours internally, and exhibit markings derived from
organic bodies, round which they have often been formed.
Flint occurs in chalk, not only in nodules, but also in seams or
layers, sometimes short and irregular, sometimes regular over a
distance of several yards. These seams vary from half an inch
to two inches in thickness, and are commonly black in colour.'
Jukes.

(16) HIPPURITIDEA, or HIPPTJRITE x Full of Ilippuritidea ; equiva-

LIMESTONE. lent to the Lower Chalk for-

SESTlSJS^CIh) J tion in Europe, Northern

Afnca, and America.

(17) RUDISTENKALK, oderHiEROGLYPHEN-<| Equivalent to the Lower

KALK. (Germ.} \ Chalk formations.

CRAIE X RUDISTES. (Fr.)

(18) SPATANGUS LIMESTONE. ] Containing many Spatangida ;

SPAT.\N.;KNK.\I.K. (Germ.) [ belonging to the Chalk group in

CAIXUIRE X SPATANGUB*. (Fr.)\ ^ JJ

(19) APTYCHUS LIMESTONE. ") Containing many Aptyclii-, there

AITYCHKXKALK. (Germ.) I are two species of this fossil, one
CALCAIRE X APTYCHUS. (Fr.) J ^^g^f^ t he Chalk, and the
other to the Jura formation.

(20) PLANER LIMESTONE. Thinly stratified, usually somewhat

PLAKEUKALK. (Germ.) j marly, occurs with the Quadersandstein
in Saxony.

284 SEDIMENTARY ROCKS.

(21) SERPTTLITE LIMESTONE. ) Full of fossil Serpulae ; oftheDeister

SERPULTT. (Germ.) \ or Wealden tormation ot West-

CALCAIRE A SERPULES. (Fr.) j phalia.

(22) PORTLAND STONE AND OOLITE.) A limestone belonging to the

PORTLAND-OOLITH. (Germ.) \ upper Jura of England, fre-

CALCAIRE PORTLANDIEN. (Fr.) ) quently Oolitic.

1 A well-known group of the upper Oolite as developed in
the South of England. It consists of shelly freestones of
variable texture underlaid by thick beds of sand, and derives its
name from the Isle of Portland in Dorsetshire, where certain
of the freestones have for centuries been largely quarried for
architectural purposes. The Portland beds abound in fossil
shells, bones of saurians, and drift coniferous wood.'

(23) ASTARTE LIMESTONE. ] Containing many Astartida be-

ASTARTENKALK. (Germ.) [ longing to the upper Jura forma-
CALCAIRE 1 ASTARTES. (Fr.) j ^ Q

(24) DICERAS LIMESTONE. ) Containing Dicers, and belonging

(Fr, ) to the upper Jura formation.

(25) CORAL RAG. \ Frequent in the Jura forma-

KORALLENKALK, PoLYPENKALK, oder L tion, the upper member of
CA^rS. ( 5ET ) ) the Middle Oolite in England.

(26) NERINEA LIMESTONE. ) F U H O f Nerinece of the Jura for-

NERINEENKALK. (Germ.) f ^t^
CALCAIRE 1 NERINEES. (Fr.) > x

(27) AMMONITE LIMESTONE. ) F U H of Ammonites of the Jura or

AMMONITENKALK. (Germ.) I T ia fnrnifltirm
CALCAIRE AMMONITIFERE. (Fr.) > LMB IO^ m atlon.

(28) JURA LIMESTONE. ) .

JURAKALK. (Germ.) \ Usually white, yellowish, or grey.

CALCAIRE JURASSIQUE. (Fr.) '

(29) OXFORD OOLITE. ) Belonging to the Jura or Oolite for-

OXFORD-OOLITH. (Germ.) f . f -p no .l fln ^
OOLITHE D'OXFORD. (Fr.) > ma on 01 Jj^ngiana.

(30) CORNBRASH. )

PLASSENKALK. (Germ.) f The same formation.
CORNBRASH. (Fr.) >

(31) BATH OOLITE. )

GRAND OOLITHE, OOLITHE f Ine 11K6.
DE BATH. (Fr.) >

(32) INFERIOR OOLITE. )

VII^ER KALIC. (Germ.) f I he like.
OOLITHE INFERIEUR. (Fr.) '

(33) LIAS LIMESTONE. ) __ -,-,-,.,.

LEIAS-KALK. (Germ.) \ Usually dark-coloured and bituminous.

CALCAIRE LIASIQUE. (Fr.) '

(34) GRYPHITE LIMESTONE. | Containing numerous Grypha, the

GRYPHITENKALK. (Germ.) L former designation for the Lias
CALCAIRE A GRYPHITES. (Fr.) J limestone<

(35) BELEMNITE LIMESTONE. } Containing numerous Belemnites,

BELEMNITENKALK. (Germ.) and belonging to the Lias for-

CALCAIRE A BELEMNITES. (Fr.)

(36) DACHSTEINKALK (Germ.), a limestone of the Northern Alps,

corresponding with the Lias formation in other parts of Europe.

(37) KLIPPENKALK (Germ.), a limestone occurring in the Carpathians,

its age not to be determined with certainty.

(38) HALLSTATTER LIMESTONE. ) A limestone of the Alps correspond-

HALLSTATTERKALK. (Germ.) > ing with the Keuper of Germany.

LIMESTONE GROUP. . 285

(39) MUSCHELKALK (SHELL \ The middle member of the Trias

LIMESTONE). L j n Germany, usually grey, and very

MUSCHELKALK. (Germ.) OY fpnaivplv <WplrTPrl in \\Wprn

CALCAIRE CONCHYLIEX. (Fr.) ' extensively developed m w estera
Germany.

(40) AN' KLLKXKALK (Germ.), stratified in thin wavy layers, or with

nodular concretions, the lower member of the Muschelkalk in
Germany.

(41) GUTTENSTEINER KALK (Germ.), a limestone of the Alps answer-

ing to the Muschelkalk of Germany.

(42) ENCRINAL or ENCRINITAL LIMESTONE. j Full of remains of

ENCRIXITEN- oder TROCHJTEX-KALK. (Germ.) I Encrinites. an upper

J member of the Mu-
schelkalk formation of Germany.

* The internal calcareous skeletons of the encrinites (in
scattered joints and fragments) are so abundant in some Car-
boniferous limestones as to compose the greater part of the
mass, hence the term encrinal or encrinital limestone. The
minuter joints of the lingers and rays are usually termed en-
trochi or wheelstones, and these when abounding in certain
limestones confer on them the title entrochal limestones. The
stalk having been perforated by a canal which kept the whole
in vital union, tne separated joints present a beadlike ap-
pearance : hence such familiar terms as " St. Cuthbert's beads "
and " wheelstones " for the solid pieces, and " pulley stones " and
" screw stones " for their hollow casts in limestones.' Page.

(43) TEREBRATULA LIMESTONE. ) Almost entirely consisting of Tere-

TEREBRATULAKALK. (Germ.) L foatttla vulqaris. Frequent in the
CALCAIRE 1 Ti BRATULK*. J Mu8chelka k of KorfhSn Germany.

(44) ROESTOXK. ) A rock occurring in the sandstone of

ROOENSTEDT. (Germ.) j Northern Germany.

(45) MAGNESIAN LIMESTONE (DOLOMITIC). ) The term Zechstein

ZECHSTEIXKALK. (Germ.) \ literally translated Slg-

CALCAIRE DU ZECHOTEIN. (Fr.) ) nifies mine-stone, so

called because it has to be mined or cut through to reach
the copper-slate which lies immediately beneath it; usually
dark- coloured and bituminous. The chief member of the
Zechstein formation of Germany.

(46) CARBONIFEROUS LIMESTONE, or MOUN-) hief member of the

TAIN LIMESTONE. L Carboniferous > lime-

KOHLEXKALK, oder BEROKALK. (Germ.) f stone formation in
CALCAIRE CARBOXIFERE. (Fr.) ) England ; when it con-

tains metal, it is called metalliferous limestone ; when it con-
tains much hornstone or chert, it is called chert-limestone.

(47) SCAR LIMESTONE, a lower member of the Carboniferous lime-

stone in Westmoreland and Cumberland.

(48) TRANSITION or GREYWACKE LIMESTONE. ) A limestone of

G-RAUWACKENKALK, Oder UEBERGANOSKALK. (Germ.) f the transition p6-

GIIAUWACKE CALCAIRE. (Fr.) ) jjod, usually com-

pact, solid, and grey.

(49) STRINGOCEPHALUS LIMESTONE. > Containing many StrinyocepJiahis

STRINGOCKPHALENKALK. (Germ.) > Burt'mi in the Devonian forma-
tion of Germany.

286 SEDIMENTAEY KOCKS.

(50) ELFEL LIMESTONE. \ Lying immediately under the pre-

EIFLER KALK. (Germ.) } ceding.

(51) ORTHOCERAS LIMESTONE. ] Full of remains of Orthocera-

ORTHOCERATITENKALK. (Germ.) I tites belonging to the Silurian
CALCAXKEAORTHOCEKES. (Fr.) ^ J formatioil) D e .^ in Scandinavia.

(52) URKALK (aboriginal or primitive limestone) is a general name,

formerly very frequently applied in Germany to denote all
granular limestones, especially those associated with the crys-
talline schists.

Limestones, as we have already remarked, are of various
origin. A few only are direct chemical precipitates from
aqueous solutions; the greater part are probably the
product of certain animals. Some have been occasioned by
the washing together of lime mud. The crystalline lime-
stones owe their state chiefly to a plutonic process of
transmutation.

As to their bedding in relation to that of other rocks, we
have nothing to add to what has previously been stated.

We only adduce a few leading references on the sub-
ject of limestones. It would serve no useful purposes
to cite all treatises respecting their local occurrence.

{References.*

Ehreriberg, on the Animal Origin of many Limestones, Die
fossilen Infusorien, 1837, Mikrogeologie, and v. L. u. Br.
Jahrb. 1861, p. 785.

Darwin, on the Formation of Coral Limestones in his ' Coral
Islands.'

G. Rose, on the heteromorphic State of Carbonate of Lime in the
Abhandl. d. k. Akad. d. Wissenschaft zu Berlin, 1856-1858.

HaugMon, on Hislopite in the Philos. Mag. 1859, [17] p. 66.

Deksse, on Hislopite in the Ann. des Mines, 1861, vol. xx. p. 435.

L. Cordier gives his views on the formation of limestones in an
article published in the Compt. rend. 1862, vol. Ixiv. p. 293.
He takes them to be principally chemical precipitates from
the sea, which formerly held much greater quantities of salts
of lime and magnesia in solution than at present.

Leymerie expounded similar views in his Elements de Mine-
ralogie et de Geologic, 1861, p. 358.

Chemical analyses of limestone exist in great va-
riety ; but they are only of local importance, serving
to decide the character of any given rock : for instance,
whether it be a limestone or a dolomite, or whether it be
fitted for building or other practical use.

As to the formation of oolite, see pp. 94-5, ante.

LIMESTONE GROUP. 287

36. DOLOMITE, MAGNESIAN LIMESTONE.

DOLOMIT. (Germ.)
DOLOMIE. (Fr.)

A granular, compact, or earthy aggregate of bitter-spar
(dolomite), usually combined with some calcspar ; does
not effervesce, or only slightly effervesces with acid ; is
easily scratched with the knife.

Spec. grav. 4 -* * . 2-82-9.

Pure dolomite, or bitter-spar, is a mineral, which we
have already described as such in the earlier part of this
work; chemically it consists of 54 carbonate of lime to
46 carbonate of magnesia. It is very seldom that the
rock occurs in this pure state ; it usually contains a much
larger proportion of carbonate of lime, and most probably
in such case consists of an intimate compound of bitter-
spar and calcspar. It usually also contains small quan-
tities of several other substances, such as clay, silica,
oxides of iron, bitumen, and the like. The chief differ-
ences between limestone and dolomite, and the mode of
distinguishing the two rocks, have been explained (p. 275,
ante). In general terms, we may say that the dolomites
closely resemble the limestones as regards their bedding
and their other attributes, except that they are more
frequently crystalline than the limestones, and sometimes
even are entirely made up of small rhombohedrons.

It was long supposed that all dolomites had been
formed by process of transmutation from limestone. It
is, however, much more probable that dolomites and
magnesian limestones were for the most part formed by
sedimentary deposit, in the same manner as the limestones
proper. Many coralline structures, and probably many
marine shells, contain some magnesia, and therefore may
likewise yield magnesian limestones ; some dolomites
again have very probably resulted from chemical pre-
cipitate from aqueous solutions. Nevertheless the origin
of many dolomites still remains very problematical, and
it is by no means impossible that transmutations of lime-
stone into dolomite may have taken place and may still
take place in the interior of the earth. We know that
magnesia plays an important part in the transmutation of

288 SEDIMENTARY KOCKS.

several rocks, in proof of which we need only instance
chlorite-schist, talc-schist, serpentine, steatite, &c. The
magnesia would appear in such cases to have penetrated
in a state of solution into the pores of the rocks, whose
character it has changed, displacing other substances.
Haidinger has suggested that sulphate of magnesia might
in very high temperature, and under great pressure, de-
compose carbonate of lime, converting it into dolomite
and gypsum ; and Von Morlot has in some measure
confirmed this suggestion by. experiment.

Dolomite, like limestone, has many varieties, most of
which are analogous to those of limestone, and resemble
them also in their geological relations ; we may therefore
treat them briefly. ( See Sterry Hunt, in Report of Brit.
Association for 1860.)

Varieties in Texture.

(a) GRANULAR DOLOMITE. ) Closely resembles granular lime-

KORNIGER DOLOMIT. (Germ.) \- stones, sometimes however sac-

DOLOMIE SACCHAROIDE. (Fr.) J c haroid, consisting of small rhom-

bohedrons, sometimes crumbling into dolomite sand ; usually

more porous than limestone. Frequently penetrated by geodes

and cavities. Its accessory ingredients are similar to those

of limestone, perhaps more abundant and multifarious.

Granular dolomites are more frequently associated with dis-
tinctly sedimentary rocks than are the granular limestones.
(6) COMPACT DOLOMITE. } Difficult to distinguish from com-

DICHTER DOLOMIT. (Germ.) L pact limestone, perhaps more rare.
DOLOMIE COMPACTE. (Fr.) J ^ ccessory admixtures and varieties
of composition are probably the same.

ERDIGER DOLOMIT. (Germ.) I earthy limestone, probably owing
DOLOMIE GROSSIERE. (Fr.) J to ^ m i croscopic J lv sma ll rhom _

bohedral crystals. If it be grey, which is sometimes the case,
by reason of its accessory ingredients, then it is sometimes
called dolomitic sand.

(d) POROUS DOLOMITE.

POROSER DOLOMIT. (Germ.)

(e) CELLULAR DOLOMITE. )

ZELLIGER DOLOMIT (RAUHWACKE). (Germ.) \ Wltn angular Cavities.
CARGNEULE. (Fr.)
(/) BRECCIAN DOLOMITE, or \

DOLOMITE BRECCIA. I Corresponds with limestone breccia

DOLOMITBRECCIE. (Germ.) | (? "81, ante).
BRECHE DOLOMITIQUE. (Fr.)'

(g) CONCRETIONARY DOLOMITE. I Consisting of a number of balls

DOLOMIE CONCRETIONXEE. (Fr.) > touching each other either like

bunches of grapes (when it is called botryoidal), or like

musket-balls, or great piles of cannonshot. Many of these balls

when broken open are found to have a radiated structure. But

LIMESTONE GROUP. % 289

they have been produced subsequently to the deposition of
the mass, as is shown by the fact of the lines of stratification
proceeding through them regularly. (Jukes.)

Dolomite is seldom oolitic, slaty, fibrous, or stylolotic, or
at all events, such varieties are much more rare than in lime-
stone.

The calcareous dolomite is very similar to the dolomitic
limestone. The two may be said to meet half way. The
argillaceous, bituminous, micaceous, siliceous, arenaceous, ferru-
ginous, and carbonaceous varieties, correspond with the similar
varieties of limestone.

Three crystalline varieties of dolomite must, however, be
mentioned.

Varieties in Composition.

( K) CHROMIC DOLOMITE. ) Is the name given by Breithaupt to a
CHROM DOLOMIT. (Germ.) I compound of dolomite, chromite, and
oxide of chromium, occurring at Nischne-Tagilk in the Ural,
and valued as a marble on account of its beautiful green colour.
The chromite appears in the form of delicate grains or crystals,
the green oxide of chromium appears to form thin laminae.
This beautiful rock also contains some iron pyrites and native
gold, and appears to be penetrated by manifold veins of quartz.

(t) DOLOMITE OF THE BINNEN THAL (ALPS). This dolomite occurs
with very rich combination of various minerals. According to
Hugard, it is somewhat phosphorescent in the dark. It con-
tains the following minerals pyrites, quartz, much mica, or-
thoclase, tourmaline, tremolite,chiastolite, garnet, ruby, realgar,
orpiment, blende, antimony-glance, dufre*nite, binnite, celestine,
barytes, and calcspar. (Compt. rend. 1858, vol. xlvi. p. 1261 ;
v. L. u. Br. Jahrb. 1858, p. 591.)

(A;) PREDAZZITE (from Predazzo, \ Is the name given by Petzold

in Tyrol). I to a dolomite occurring at Pre-

PREDAZZTT. (Germ.) f dazzo, in South Tyrol. It ad-

J joins syenite-granite, of which

it is a metamorphic product. It is white and crystalline-
granular, resembling the most beautiful marble. Besides car-
bonate of lime and magnesia, it contains some siliceous clay
and some water. Hence Petzold called it a special mineral :
probably it is a compound of dolomite and brucite. (v. L. u.
Br. Jahrb. 1848, p. 583.)

Geological Varieties.

(1) CORALLINE DOLOMITE. ) Jura formation in England and

KORALLEJJDOLOMIT. (Germ.) f Germany.

DOLOMIE CORALLIENNE. (/V.) ' J

(2) ALPINE DOLOMITE. \ Chief dolomite of the North-

DOLOMDJ ALPINE (cARGNEULEs). (Fr.) j era Alps, corresponding with
the lower part of the Lias formation.

(3) KEUPER DOLOMITE. I in the Keuper of Germany.

KEUPERDOLOMTT. (Germ.) '

(4) Fl 2SSS I Si~, } In the Keuper of Swabia.

DOLOM1E ROUGE. (Fr.) '

290 SEDIMENTARY EOCKS.

(5) MYOPHORIA DOLOMITE. I In the lower division of the

MYOPHORIEN-DOLOMIT. (Germ.) > Keuper formation.

(6) MALBSTEIN or NAGELFELS (Germ.}. A dolomite of the upper

division of the Muschelkalk, in Swabia.

(7) WELLENDOLOMIT (wavy dolomite), belonging to the lower divi-

sion of the Muschelkalk, in Germany.

(8) MAGNESIAN LIMESTONE. > A dolomite limestone of the Per-

CALCAIRE MAGNESIEN. (Fr.) } m i an formation in England.

(9) ZECHSTEIN DOLOMITE. \ In Thuringia and

ZECHSTEIN-DOLOMIT, RAUHWACKE. (Germ). ) Franken

G0) D C Hr} ^ the Zechstein of Thuringia.

Many different varieties of dolomite are known in the Car-
boniferous system, or occur in the Cambrian, Silurian, De-
vonian, and Permian formations. The dolomite of Derbyshire,
Durham, and Yorkshire in the latter formation furnishes the
well-known building-stone of which the Houses of Parliament
are built. In the more recent formations, dolomite would
appear to be less frequent, unless it be that many compact dolo-
mites are still mistaken for limestones.

Much has been written on the formation of dolomites since
the first celebrated treatise on that subject of L. v. Buch, in
Leonhard's Almanack, 1824. Of the various arguments in
favour of the transmutation of limestone into dolomite, perhaps
the most deserving attention is the hypothesis developed by
Haidinger and v. Morlot, according to which the conversion
was effected by means of solutions of sulphate of magnesia
(Epsom salt), and gypsum was produced at the same time.
In many cases this is very probable. (Haidinger's Naturw.
Abhandl. vol. i.) To us it appears very probable that many
dolomites have been formed by crystallisation of coral-reefs, as
v, Eichthofen has ably proved in the case of some of the
dolomites of Southern Tyrol. Vide MM. Seemann and Guyerdot,
Bullet, de la Soc. geol. de France, (n. s.) vol. xix. p. 995,1862.

GYPSUM AND ANHYDRITE.

Gypsum is a combination of sulphate of lime with
water. Anhydrite is sulphate of lime without water.

Gypsum as a rock is much more frequent than anhy-
drite at least ,we seldom find anhydrite on the surface
of the earth a circumstance which is explained by its
readiness to absorb water, and consequent conversion into
gypsum. For the rest, the geological position of the two
is very similar.

37. GYPSUM.

GYPS. (Germ.)
GYPSE. (Fr.)

An aggregate of sulphate of lime, usually crystalline,
sometimes compact or fibrous - 3 soft, and usually white.
Spec. grav. ...'... ',.- 2-3.

LIMESTONE GROUP. 291

Pure gypsum consists of 46*5 per cent, sulphuric acid,
#2 '5 lime, and 21 water. It is so soft that it may be
scratched with the nail, and only gives a dead sound when
struck with the hammer. By these properties it may be
most easily distinguished from white granular limestone,
to which it bears great resemblance. Its texture is most
usually fine-grained (alabaster), sometimes also porphy-
ritic, containing large shining crystals of selenite. It
is only rarely quite compact; in thin layers or narrow
veins it is frequently fibrous or sparry. Its original snow-
white colour is sometimes tinged grey by admixture of
bitumen or clay, or red by oxide of iron. The mass
sometimes (though rarely) contains as accessories some
mica, talc, quartz, boracite, pyrites, copper pyrites, grey
copper, zincblende, and sulphur.

Moreover, in gypsum rock are sometimes found nests
or veins of aphrite, anhydrite, rock-salt, sulphur, and
chert.

The weathered surfaces of gypsum (owing to its solu-
bility in water) are usually much worn or eaten into.

Varieties in Texture.

(a) GRANULAR GYPSUM or ALABASTER. } Almost always white

somewhat translucent. '

(6) PORPHYRITIC GYPSUM. ) With crystals of gypsum in a fine-
POR (SJ,. 1 T IOEH GYP8 ' I g 111 ^ gJP sum matrix.

(c) COMPACT GYPSUM. ) 5 are > usually mixed with clay or
DICHTER GYPS. (Germ.) bitumen, which impart a grey colour
GYPSE COMPACTK. (Fr.) ) to the rock.

(rf) FIBROUS GYPSUM. ) Usually only in the form of thin veins
FASERGYPS. (Germ.) \ or seams occurring in other gypsum,
GYPSE FIBRETJX. (Fr.) ) or j n argillaceous shale or marl.

(e) SPATHIC or SPARRY GYPSUM, or SELENITE. \ Occurs in similar

SPATHIGER GYPS oder BLATTERGYPS. (Germ.). I manner to the

J fibrous variety.

(/) TRIPESTONE. \ Is a variety both of texture and com-

GEKROSESTEIN. (Germ.) I position. It is formed of thin lavers
PIERRE DE TRIPES. (/T.)J g pure white gvpsum) alternating

with grev argillaceous gypsum, the whole twisted or crumpled
to resemble a ruff, whence the German name.

Varieties in Composition.

ARGILLACEOUS GYPSUM.
THONGYPS. (Germ.)
MARXE GYPSEUSK. (Fr.)

u 2

\ Grey, spotted, or striped, by reason

\ o f an admixture of clav.
>

292 SEDIMENTARY ROCKS.

(A) BITUMINOUS GYPSUM. \ Difficult to distinguish, from the
BrruMiNbsER GYPS. (Germ.) v last-named variety.
GYPSE BITUMINEUX. (Fr.) )

(t) MICACEOUS GYPSUM. \ Mixed with mica or talc j analogous to
GIJMMERGYPS. (Germ.) ! micaceous limestone ; of rare occur-
GYPSE NIVIFOKME. (Fr.) J ^^ ^ ^ {a ^^ Q crygtalline

schists, as (e.g.) on the south slope of the St. Gotthard.

Gypsum is rarely distinctly stratified or fossiliferous ;
both facts are in all probability connected with the mode of
its original formation, pointing to a chemical rather than
mechanical origin. It is contained in deposits of the
most different periods, and exceptionally in the crystalline
schist formations. It seldom forms extensive beds parallel
to the other strata, but rather flat lenticular or irregular
masses or accumulations in connection with anhydrite,
rock-salt, and clay, or sometimes with dolomite. Some-
times it even occurs in abnormal bedding between other
sedimentary rocks. From the circumstances under which
it is found to occur, it has been inferred that gypsum
must be a product of the local conversion of limestone.
Chemically, no doubt, this would be possible, if the
requisite sulphuric acid were present, but such origin on a
large scale is not capable of demonstration from any known
facts. Some gypsum rocks may be actually shown to
have been formed by deposit from aqueous solution of
sulphate of lime ; others by the decomposition of pyrites
in the immediate neighbourhood of calcspar ; others,
again, by the absorption of water into anhydrite. Hai-
dinger and Von Morlot have also shown that gypsum and
dolomite may together be formed by the operation of
solutions of sulphate of magnesia (Epsom salt) on lime-
stone ; nevertheless all these different facts or theories of
possible formation hardly suffice to account satisfactorily
for the origin of the great masses of gypsum (frequently
combined with rock-salt and anhydrite) which occur in
the flotz or secondary series. The supposed origin of
gypsum from anhydrite leaves the greater difficulty un-
solved of the original deposit of anhydrous sulphate of
lime.

The exceptional nature of the bedding of gypsum rocks,
as well as the frequent disturbances which appear in the
adjoining strata, are best explained by the action of water
in partially washing away the original deposit of gypsum,

LIMESTONE GROUP. 293

and also the rock-salt with which it is usually accompanied.
The first consequences of such process would be to form
great cavities ; after a time the roofs of these cavities
would break down and cause disruption in the super-
incumbent rocks. This is to us the most probable mode
of accounting for the existing phenomena. Certain it is
that these disturbances of the neighbouring strata are not
of a nature to authorise us to infer an eruptive origin of
the gypsum rock.

The gypsum beds of different geological periods have
not received different names, as they are not petrographi-
cally to be distinguished from each other. It may never-
theless be of interest to compare the different places of
their occurrence in the European geological series. These
are chiefly as follows :

(1) In Miocene deposits, with remains of plants at Paria, in Italy
with sulphur and rock-salt in Sicily.

i2) In Eocene deposits, with bones of animals, in the Paris basin.
3) In the Triassic formations of the French and Swiss Alps with
rock-salt and cargneule (Lory, Favre, &c.)

(4) In the Keuper of Germany, sometimes with rock-salt, but with-

out fossils.

(5) In the Muschelkalk of Germany, with anhydrite and rock-salt,

without fossils.

(6) In the Upper Variegated Sandstone of Germany and the Alps,

with rock-salt and anhydrite, without fossils.

(7) In the New Red Sandstone of England, with rock-salt, without

fossils.

(8) In the Zechstein of Germany, with rock-salt and anhydrite,

without fossils.

(9) In the Permian formations of Russia, with rock-salt.

(10) In the clay-mica-schist of Herren-Grund, in Hungary (of un-

doubted antiquity), with fahlerz and copper pyrites.

(11) In the crystalline schists of the Alps at St. Gotthard, with mica ;

at Bugg, in Switzerland, with mica and talc.

References.

Hausmann, Bemerkungen iiber Gyps und Karstenit, 1847.
Karsten, iiber Gyps und Karstenit 'in his Archiv, 1848, vol. xxii.
pp. 545 and 578.

38. ANHYDRITE, MURIACITE, KARSTENITE.

AMIYDRIT, MURIACIT, KARSTENIT. (Germ.)
ANHYDRITE. (J?r.)

A granular or compact aggregate of anhydrous sulphate
of lime ; harder than gypsum ; white, grey, or blue.
Spec, gray 2-82-9.

294 SEDIMENTARY ROCKS.

Pure anhydrite is white, and may easily be mistaken
for gypsum or dolomite. It may, however, be easily dis-
tinguished from dolomite by its not effervescing with acid
even when pulverised and heated ; and it is much harder
than gypsum. The colour of the grey or blue varieties
is caused by the admixture of clay or bitumen in small
quantities. There are scarcely any distinct varieties of
texture. It occurs in nature under similar relations to
gypsum, except that it is scarcely ever met with on the
surface of the ground, because there, by the absorption of
water, it is converted into gypsum.

For literary references refer to those under the head of
gypsum.

FRAGMENTAL ROCKS.

These rocks are composed of the fragments of older
rocks, which have been broken up by mechanical forces, ,
and their parts deposited and reunited or cemented to-
gether into a solid mass ; they are therefore termed frag-
mental rocks.

A somewhat similar origin may no doubt be ascribed to
the argillaceous rocks, marls, and some limestones, but in
this case the parent rocks have undergone chemical decom-
position, as well as mechanical disintegration, and the dis-
integrated parts have been resolved into very fine mud
before the work of reconstruction commenced, so that the
connection of the new rocks thus formed with those from
which they spring is not so evident or easily traceable as
in the fragmental rocks proper.

SANDSTONES consist of grains of some mineral (usually
quartz) compacted together ; CONGLOMERATES of rounded
stones or pebbles cemented together ; BRECCIAS of angular
fragments likewise bound,

Uncompacted SAND, GRAVEL, SHINGLE, and HEAPS
OF RUBBISH belong to this division of the materials
of which the earth's crust is composed.

TUFA rocks are conglomerates, more or less firmly
united, of fragments thrown from volcanoes of the pre-
sent or an earlier time.

FRAGMEXTAL GROUP. 295

39. SANDSTONE and GRITSTONE.

SANDSTEIN, PSAMMIT. (Germ.)
ORES. (Fr.)

Small grains of some mineral, usually of quartz, are
cemented together by some mineral substance.

The process of the original formation of all sandstones
has consisted jn the washing together of small grains of
some solid mineral, usually quartz, and these were after-
wards bound together into a solid rock by some cementing
medium, or perhaps by simple pressure. In other words,
these rocks were formed from sand, into which they may be
resolved again. The grains are usually rounded off, and
only exceptionally exhibit faces and edges of crystals.

Quartz being the most abundant mineral of the earth,
and at the same time very hard and difficult of decompo-
sition, furnishes the material for the most sandstones ;
these, however, also contain particles of felspar, flakes of
mica, fragments of shells, and grains of glauconite. The
binding medium of these grains usually consists of clay,
marl, or hydrated oxide of iron ; less usually of silica,
carbonate of lime, kaolin, talc, or asphalte. Sandstones
often contain as accessories concretions of hydrated oxide
of iron, frequently in the form of balls (eagle stones*) or
irregular masses, nodules of pyrites, rounded pieces of
amber, coal, and the like.

As all sandstones are mechanical aqueous deposits, they
are always stratified. They frequently are interstratified
with other rocks in alternate beds, such, for instance, as
clay-slate, argillaceous shale, marl, &c. They belong to
no exclusive geological period, but are found in those of
most various age.

Varieties in Texture.

(a) COMMON SANDSTONE. ) With grains about the size of a

SANDSTEIN. (Germ.) j mustard-seed.

* ' " Eagle stone," the ^Elites lapis of the ancients, fabled to have
been laid in the nest of the eagle. A variety of nodular argilla-
ceous iron-ore, having a concentric structure and occasionally so de-
composed within as to have a loose kernel which rattles on being
shaken. This kernel was known by the name of Callimus, and was
supposed to be the young in the womb of the parent nodule ; hence
the fable of the aetites bringing forth young. When there is no in-
ternal kernel the nodule becomes a geode.' Page.

296 SEDIMENTARY ROCKS.

(6) COARSE-GRAINED SANDSTONE. )

GROBKORNIGER SANDSTEIN. (Germ.) h -Passing into conglomerate.

GRES A GROS GRAINS. (Fr.)

FEINKORNIGER SANDSTE^ oder L Or fine sandstone, passing into an

FEINSANDSTEIN. (Germ.) apparently compact state.

GRES A GRAINS FINS. (Fr.) J

(d) CRYSTALLISED SANDSTONE. ( With grains of quartz-crystals

KRYSTALLSANDSTEIN. (Germ.) \ n wni ch the crystalline faces may
GRES CRISTALLIN. (Fr.) ) be recognised.

In all these sandstones the texture varies not only in
respect of the size of the grains, but in respect of their
quantity or abundance compared with that of the cement-
ing medium. Some sandstones, owing to the predomi-
nance of the latter, pass into rocks of a totally dif-
ferent character, such as marl, claystone, &c.

(e) FISSILE SANDSTONE. ^ Flagstone in part j usually owes

SCHIEFRIGER SANDSTEtN oder L jt s texture to a plentiful ad-
GRES^S"" ( ^ I mixture of mica.
(/) GLOBULAR SANDSTONE. ] With ball-shaped concretions of com-
KTTGELSANDSTEIN. (Germ.) L pac t or firm sandstone in a matrix of
GRES NODULEUX. (Fr.) J ^ ^^ stmcture< In Transy l_

yania very extensively developed.

According to differences in the nature of the cementing
material, we have the following varieties :

(ff) ARGILLACEOUS SANDSTONE. ) The most frequent variety.

GRES ARGILEUX. (Fr ' passes into arenaceous clay, ar-

gillaceous shale, or clay-shale.

(A) MARLY SANDSTONE. \ The next most frequent va-

MERGEIJGER SANDSTEIN oder L ^ety. If the marl predomi-

MERGELSANDSTEIN. (Germ.) , J ,-, .,

GRES MARNEUX. (Fr.) ' nat es, then it passes into are-

naceous marl or marl-shale.

(t) CALCAREOUS SANDSTONE. "j With a calcareous cementing

KALKIGER SANDSTEIN oder KALK- L medium ; somewhat rare ;
G^fcS^KE* rT (Fr.) ) Passes into arenaceous lime-

stone.

(k) SILICEOUS SANDSTONE, -j With a very solid hornstone-like
KEESELSANDSTEIN. (Germ.) \ cementino: material, in which the in-
GR6s SILICEUX - (Fr '> } dividual grains of quartz are finely
imbedded and are frequently not to be distinctly recognised.
When these grains are intimately blended with the matrix,
then this variety of sandstone passes into quartzite, quartz-
rock, or a kind of hornstone.

(7) FERRUGINOUS SANDSTONE. \ A sandstone with hydrated

EISENSANDSTEIN oder EisENscHiissiGER [ oxide of iron, or peroxide
GREs A F E N iNESn^.) J of iron, as its cementing

material, which always
gives the rock a red or brown colour. Sometimes it is spotted or

FKAGMENTAL GROUP. '297

striped from the unequal distribution of the iron (Tiger Sand-
stein, Germ. ; Tiger sandstone, Engl}. If the hydrated oxide
of iron should become predominant, as is sometimes the case,
then we even find transitions into brown haematite.
(m) KAOLIN SANDSTONE. \ With kaolin as cementing medium ;

KAOLINSANDSTEIX. (Germ.) ) almost always white. Occurs, e. g.,
at Wissenfels in Thuringia. If sandstones of this description
contain only quartz and kaolin, they form very fine fire-proof
stones, and may be used for lining furnaces j e. g. Steinhaide, in
the Thuringian Forest.
(n) TALCOSE SANDSTONE. ) With a talcose cementing medium.

TALKSANDSTEIN. (Germ.) | This varietv approaches in character

GRES TAIAJUEUX. (Fr.) > io itacolumite, which, as we have
already seen, is a kind of sandstone (vide p. 247, ante).
(o) ASPHALTIC SANDSTONE. \ With asphalte as cementing me-

ASPHAI.TSAM.STKIV. (Germ.) [ dium, a variety only of exceptional

Ctete BITUMINEUX. (Fr.) J

NOTE. It is frequently very difficult to determine the
exact nature of the cementing medium, especially as two or
more kinds often occur together in the same rock.

According to differences in the nature and substance
of which the grains themselves are composed, we have the
following varieties :

(;>) QUARTZ-SANDSTONE. QUARTZ-^ (The quartz-psammit of Nau-
PSAMMIT. QUARTZ-GRIT. mann.) \Vith grains of quartz.

QuARzsANDsrrEiN. (Germ.) I his is the most frequent of

GIIES QUARTZEUX. (Fr.) ' all sandstones.

(The mico-psammit
(?) MICACEOUS SANDSTONE. MICACEOUS GRIT. \ ofNaumann) Con-

GLIMMERSANDSTEIN. Mico-P8AM M rr, Naumann. f

(Germ.) \ taming flakes of

PSAMMITE (GRES MicACE), Brongniart. (Fr.) ) mica with the grains

of quartz.
(r) ARKOSE or FELSPATHIC SANDSTONE.) with g 1 of felspar as

ARKOSK. (Germ.) f well as quartz, combined

ARKOSK. (Fr.) ) i n 8Om e cases with flakes

of mica. This rock thus resembles granite in its composition,
and is therefore sometimes called Regenerated granite.
() GREEN SANDSTONE (GREENSAND).) Containing grains of glauco-
GRtfxsANDSTEiN. (Germ.) I nite with uartz, imarti

(Germ.) nite with quartz, imparting

VKRT. (Fr.) J l

the whole rock, sometimes even a dark-green colour. Ac-
cording to Ehrenberg's microscopic analysis, these glauconite
grains usually consist of the fossils of very minute Testacea.
(0 SHELL-SANDSTONE. x Coral sandstone : the grains are fragments

IU9 ^T DSmN ' f . f shells or coral '. the cementing mate-
GRES COQUILLIER. (Fr.)) rial carbonate of lime. Rare.

The difference between sandstone and gritstone is
a vague and undeterminable one, as must necessarily

298 SEDIMENTARY ROCKS.

be the case where the things themselves are so various
and capricious in composition and texture. The term
gritstone is, perhaps, most applicable to the harder sand-
stones, which consist most entirely of grains of quartz,
most firmly compacted together by the most purely sili-
ceous cement. The angularity of the particles cannot be
taken as a character, since the rock commonly called
4 millstone grit ' is generally composed of perfectly round
grains, sometimes as large as peas and even larger : the
stone then commencing to pass into a conglomerate.'
Jukes.

Jukes gives the following local terms for sandstone :

Rock, used generally in South Staffordshire to denote any
hard sandstone.

Rotclie or Roche, generally used for a softer and more friable
stone.

Rubble means either loose angular gravel, or a slightly
compacted brecciated sandstone.

Hazel is a North of England term for a hard grit.

Post is a similar term for any bed of firm rock, and is usually
applied to sandstone.

Peldon is a South Staffordshire term for a hard, smooth,
flinty grit.

Calliard or Galliard is a northern term for a similar rock.

Freestone is a term in general use which is often applied to
sandstones, but sometimes to limestones and even to granite,
as in the counties of Dublin and Wicklow. It means any stone
which works equally freely in any direction, or has no tendency
to split in one direction more than another.

Flagstone (see ante, p. 296), on the contrary, means a stone
which splits more freely in one direction than any other, that
direction being along the lines of the original deposition of the
rock. These stones are ordinarily sandstones, though often
very argillaceous, and some flagstones are perhaps rather in-
durated clay in their beds than sandstone.

Thin-bedded limestones may also be flagstones.

Independently of the different petrographic varieties of
sandstone, we have numerous geological varieties. These
must always be determined by their bedding or by their
fossils ; and they are frequently only local in their cha-
racter.

(1) THE MOST RECENT MARINE \ mich on some coasts is still
SANDSTONE. in process O f formation.

NEUESTER MEERESSANDSTEIN. (Germ.)) r

FRAGMENTAL GROUP. 299

(2) BLATTERS ANDSTEIN (Germ.), containing impressions of leaves of

trees ; occurs in the Mayence Tertiary basin.

(3) MOLASSE SANDSTONE. \ A sandstone of the Molasse forma-

MOLASSESANDSTEIN. (Germ.) I tion on the northern margin of the
MOLASSE. (Fr.) I Alpg . ugually

(4) BROWNCOAL SANDSTONE. \ Sandstone of the Browncoal

BRA0NKOHLEN8AXD8TE1N. (Germ.) j formation in Bohemia and
Northern Germany. Miocene, Frequently siliceous sandstone.

(5) BAGSHOT ^AND, in 'England. Eocene.

(6) THANET SAND, in England. Eocene.

(7) V ^K^ *.,} P^ Eocene, partly older.

(8) C ^^^grS~.) } *** Eocene, partly older.

(9) FUCOIDAL SANDSTONE. )

FUCOIDBNSANDOTEIN. (Germ.) \ With remams of Fucoids.

- CfefeB 1 FUCOtDES. (Fr.) J

(10) NUMMULITIC SANDSTONE. \ Containing remains of Num-

NUMMUUTENSANDOTEIN. (Germ.) } m ,,)\+ oa

GRES JfUMMULITHIQtJE. (Fr.) ) l XS '

(11) RALLIGSANDSTEIN (Germ.). A sandstone of Switzerland. Eocene.

(12) TAVIGLIANAZ SANDSTONE. . T , 1-1 -p^^n,

TAVioLiANAZ-SANDerEiN. (Germ.) f

(13) MACIGNO. \ _

MACIGNO. (Germ.) I In North Italy. Eocene, or older.
MACIGNO. (Fr.) )

(14) QUADER SANDSTONE. ) So called on account of its rectan-

QUADERSANDSTEIN. (Germ.)} gular jointings. In conjunction with
the planer limestone, with which it is associated and inter-
stratified, it forms a part of the Chalk group in Saxony and
Bohemia.

(15) GREENSAND (UPPER AND LOWER). ] These constitute two di-

GRUNSAND. (Germ.) \ visions of the cretaceous

GRES^VERT (SUPERIEUB ET INFERIEUR). J grQup ^ England-

(16) HILS SANDSTONE. \ The lowest member of the Chalk group

HILSSANDOTEIN. (Qerm.) ) in Westphalia.

(17) TASE^O^ ^^ | A 8an( istone of the Chalk period in Istria.

(18) DEISTER SANDSTONE. i Westphalia, belonging to the Weal-

DEISTERSANDSTEIN. (Germ.) j den formation.
(10) HASTINGS SAND, England. Wealden formation.

(20) PORTLAND SAND. Upper Oolite formation of England.

(21) DOGGER (Germ.). A coarse-grained sandstone, brown, some-

times very argillaceous. Whitby, Yorkshire. W T estphalia.
Jura formation.

(22) LIAS SANDSTONE AND SAND. I Usually light-yellow and fine-

LHASSANDSTEIN. (Germ.) I grained. A lower member of

J the Lias, at Gotha. An upper
member of the Lias of England.

(23) CARDINIA SANDSTONE. ) Containing many Thalassites

THALASSTTKN-SANDSTEIN. [(Germ.)} (Cardmia).

(24)

(25) SCHILF SANDSTONE. I A member of the Upper Keuper in
SCHILFSANDSTEIN. (Germ.) > Swabia.

300 SEDIMENTARY ROCKS.

(26) VARIEGATED SANDSTONE. ) So called on account of its being

BUNTSANDSTEIN. (Germ.) \ frequently particoloured. It is,
GRES BIGARRE. (Fr.) ) however," sometimes of one uniform

colour (white, yellow, or red). It constitutes the chief mem-
ber of the Buntsandstein formation of Germany.

(27) VOSGES SANDSTONE. | Lower division of the Sandstone

VOGESENSANDSTEIN. (Germ.) f formation of the Vosges Mountains.

(rRES VOSGIEN. (/*/*.)

(28) RED SANDSTONE OF THE ALPS] Corresponds with the Varie-

(VERRUCANO). I gated Sandstone of Germany

ROTHER ALPENSANDSTEIN. (Germ.) [ and the New Red Sandstone
GRES ROUGE DES ALPES. (Fr.) J o f En?lancL

(29) NEW RED SANDSTONE. Name applied in England to the whole

series of strata lying between the Lias and the Permian rocks.

(30) NEWENT SANDSTONE. A member of the Keuper series of

Gloucestershire.

(31) WEISS- oder GRAULIEGENDES. (Germ.} A White or Grey

Sandstone (frequently conglomeratic), forming the lowest mem-
ber of the Zechstein in Thuringia, and sometimes containing
copper-ore (Sanderz).

(32) CUPRIFEROUS SANDSTONE. \ A member of the Permian forma-

KUPFERSANDCTEIN. (Germ.) I tion in Russia. Old Red Sand-
GRES CUPRZFERE. (Fr.) J gtone of gout k of Irelan(L

(33) ROTHER SANDSTEIN. (Germ.) Former designation for the Roth-

liegende formation, containing arkose and other sandstones,
usually of red colour.

(34) CARBONIFEROUS SANDSTONE. \ White, brown, yellow, grey,

KOHLENSANDSTEIN. (Germ.) I or almost black, in which case
) it contains carbon. Frequent
in the Carboniferous strata of old countries.

(35) MILLSTONE GRIT. } Lowest member of the Coal

formation sometimes.

(36) GREYWACKE SANDSTONE. \ Usually very firm, with ar-

GRAUWACKEN-SANDSTEIN, oder KOR- I orillaceous cementing medium.

wJKfiSSTillS"* ^hen very fine-grained or

; almost thick, it has been

called grauwacke or quartzite ; sometimes it is very coarse-
grained, even conglomeratic. If the clay medium should
become slaty, then it goes over into greywacke-schist. It is
frequent in Devonian formations. Delesse, however, appears
to have understood something different in the Vosges under
the term of greywacke, since he says that it consists almost
entirely of albite, forming a felspathic matrix, containing
quartz, hornblende, several kinds of mica, chlorite, and occa-
sionally some carbonates. Ann. des Mines, vol. iii. p. 747 ;
v. L. u. Br. Jahrb. 1856, p. 359.

37) BAGGY POINT SANDSTONE (Page}. Upper Devonian.
'38) DURA-DEN SANDSTONES, Fifeshire (Page), with Hdoptychn
and Pterichthys. Upper Devonian.

(39) DUNSE SANDSTONES, Scotland (Page). Red and white. Upper

Devonian.

(40) FLAGSTONES OF FORFAR, with Cephalaspis, Cheiracanthus, and

Pt,erygotus. Lower Devonian.

FRAGMEXTAL GROUP. 301

(41) LTIDLOW SANDSTONE, micaceous, prey. Upper Silurian.

(42) WENLOCK SANDSTONE, Upper Llandovery; gritty. Upper

Silurian.

(43) CARADOC SANDSTONE, frequently quartzite. Lower Silurian.

(44) LLANDEILO and LINGULA FLAGS, laminated sandstone, rich in

mica. Lower Silurian.

(45) STJPER STONES, Shropshire j siliceous sandstones, passing into

quartz rock. Cambrian.

We will cite a few treatises only as to sandstone, re-
lating to special varieties.

References.

Gerhard draws attention to the fact that the grains of quartz

are angular and transparent in many sandstones. Abhandl.

d. berl. Akad. 1810-17, p. 13.
Schafthatctl found grains of amorphous silica in sandstone, v.

Leonhard's Jahrb. 1846, p. 648.
Zeuschncr, Sch<ifthautl, and v. Haver, on Carbonate of Lime

and Magnesia as connecting Media, v. Leonhard's Jahrb.

1843, p. 166 ; 1846, p. 665 j and Jahrb. d. geol. Reichsanst.

vol. v. p. 880.
Gntberlet published a treatise on the crystalline sandstones

formed between the Vogelsgebirge and the Rho'n, in v.

Leonhard's u. Br. Jahrb. 1811, p. 860.
Ehrenberg, on Greensand, Berlin, 1856, in v. L. u. Br. Jahrb.

1855, p. 469 ; and 1857, p. 91.

Bischof considers the mica of the sandstone as a recent forma-
tion. Geologie, vol. ii. p. 1450.

Appendix.

This seems the most appropriate place in which to in-
troduce the mention of loose sand, which consists of in-
coherent grains of quartz, or other mineral, and to a
certain extent is a necessary preliminary state to the
formation of all sandstone.

SAND.

SAND. (Germ.)
SABLE. (Fr.)

Usually grains of quartz, sometimes, however, of other minerals,
e. g. felspar, ^dolomite, calcspar, mica, and the like ; without
binding medium.

These loose aggregates of mineral grains need no further
description, although they may vary considerably in the size
as well as the substance of their individual particles. A
certain coarse sand is called grit.

Sand sometimes derives a special importance from admixture
of metallic grains or precious stones ; these, however, only occur
locally, and are subordinate in quantity j thus, for instance,

302- SEDIMENTAEY HOCKS.

sand is found to contain grains of gold, platinum, tin-ore, mag-
netic iron-ore, diamond, zircon, hyacinth, topaz, emerald, garnet,
pyrope, &c. It is worthy of remark that such admixtures are
almost unknown, except in the newest incoherent aggregates
of sand or clay (stream beds), very seldom in solid sandstone.
It may be, however, that solid sandstones do contain similar
ingredients, and only that .they have been less subjected to in-
vestigation than the loose superficial sand. Traces of gold
have been actually found, e.g. in the Molasse sandstone of
Switzerland, and again, some tin-ore has been discovered in a
sandstone of Brittany.

CONGLOMERATES.
40. CONGLOMEKATE, PUDDINGSTONE.

CONGLOMERAT, POUDDINGSTEIK. (Germ.)
CONGLOMERAT, POUDIKGTJE.

Pebbles or rounded stones of any mineral or rock firmly
cemented together by media of various kinds.

Conglomerates are of very various composition. Al-
most the only restriction to the nature of their materials is
that pebbles can only consist of a very firm substance
capable of resisting decomposing influences. Their bind-
ing medium usually consists of some of the most frequent
and abundant of the earth's materials, such as clay, sand,
quartz, or oxide of iron. The pebbles chiefly consist of
quartz, lydian-stone, granite, gneiss, mica-schist, quartz-
porphyry, greenstone, basalt, compact limestone, and the
like ; much more rarely of sandstone, clay-slate, argilla-
ceous shale, coal, and the like.

A special geological importance attaches to conglome-
rates, from the fact that they must in every case be more
recent than the rocks whence their pebbles were derived.
Thus they often serve to determine the relative age of
individual rocks. By noting the position of the parent
rocks, the geologist is often enabled to draw conclusions
as to the course and direction of former watercourses.
Again, they often present interesting phenomena pointing
to certain special processes in their formation. For
instance, the pebbles are sometimes broken or dislocated,
their parts remaining imbedded close together ; or the
pebbles are found marked with grooves and scratches ;
or they are sometimes indented and forced one into

FRAGMEXTAL GROUP. 303

another (which latter case is the most difficult of expla-
nation). There is a conglomerate at St. Loretta in the
Leitha Mountains, of exceptional character, containing
hollow limestone pebbles, the inside cavities of which are
concentric with the outside surface.

It is difficult to classify conglomerates, on account of
their manifold variety. We can, of course, speak of more
or less coarse textures we may also designate them ac-
cording to the nature of their principal pebbles, or the
character of their binding medium. Some examples will
suffice to explain how such a mode of nomenclature might
be adapted to individual cases. Taking the nature of the
pebbles as the distinguishing feature, we may speak of
quartz-conglomerate, porphyry-conglomerate, gneiss-con-
glomerate, or miscellaneous conglomerate ; or, according
to the character of the matrix, we may call the rock
argillaceous, siliceous, ferruginous, &c.

The following are conglomerates which have been
specially named from their bedding or geological posi-
tion :

(1) NAGELFLUE. ) A conglomerate of the Molasse

NAGELPLUHE. (Germ.) [ formation on the northern margin

CONGIA>MERAT ALPIN. (Fr.). ) o f the Alps, the pebbles chiefly con-
sisting of Alpine limestone, but partly of quartz, lydite, granite,
gneiss, &c.

(2) PLANERCONGLOMERAT (Germ.) in Saxony belongs to the Quader-

sandstone, with pebbles of granite, syenite, or quartz-porphyry
bound together by sandstone cement.

(3) HILSCONGLOMERAT (Germ.), with limestone and ironstone peb-

bles, and likewise many remains of shells, occurring in the
lower division of the Hils formation of Westphalia.

(4) VOSGES CONGLOMERATE. 1 Lower division of the variegated

CONGLOMERAT vosoiEN. (Fr.) > sandstone of the Vosges, with
many pebbles of quartz and lydite.

(5) CONGLOMERATE OF THE WEISSLIEGENDE. I In Thuringia, the

CONGIX>MERAT DBS WEI3SUEGENDEX. (Germ.), ' lowest member of

the Zechstein formation, with numerous pebbles of quartz,
lydite, and clay-slate.

(6) CONGLOMERATE OF THE ROTHLIEGENDE. I In Germany, with

CONGLOMERAT DBS ROTHUEGENDEN. .(Germ.) > pebbleS of " quartz,

lydite, granite, gneiss, mica-schist, and quartz-porphyry, and
a cementing medium of ferruginous sand.

(7) GREY CONGLOMERATE. 1 Lowest member of the Rothlie-

GRAUES CONGLOMERAT. (Germ.) > gende, in Saxony.

(8) CONGLOMERATE OF HAINICHEN. I In Saxony, answering to

CONGLOMERAT VON HAINICHEN. (Germ.) > the Carboniferous Lime-
stone formation j containing clay-slate, mica-schist, gneiss,

304 SEDIMENTARY ROCKS.

granulite, granite, and greenstone j binding medium arenaceous
and of brown colour.

(9) GRETWACKE CONGLOMERATE. j At the Hartz, in Thuringia,
GRAUWACKEN-CONGLOMERAT. (Germ.) \ in Bohemia, and other places,

^ partly Devonian, partly Si-

lurian, with pebbles of quartz, lydite, clay-slate, granite, &c.
Binding medium argillaceous, or arenaceous, and of grey colour.

We should state that there are some so-called pudding-
stones which have altogether the appearance of conglo-
merates, but, in fact, are not such, as they do not consist
of pebbles cemented together, but they contain rounded
concretions of some siliceous or calcareous substance.

We shall confine our references to some treatises con-
taining mention of special phenomena.

References.
Haidinger, on the Lauretta Conglomerate, in Ber. d. k. k.

Akad. d. Wissensch. zu Wien, 1856, July 15.
Lartet, on Pebbles showing Indentations, in v. L. u. Br. Jahrb.

1836, p. 196.

Blum, on the same, ibid. 1840, p. 525.
Daithree, on the same, in Compt. rend. vol. xliv. p. 823.
Cotta, on the same, Geol. Fragen, 1858, p. 204, and on Ver-

worfene Geschiebe in the same account, p. 212.
Wiirtetiberger, on the same subject, in v. L. u. Br. Jahrb. 1859,

p. 153.

Deicke, on the same subject, ibid. 1860, p. 219.
GttrU, on the same subject, ibid. 1861, p. 225.

Appendix.
BOULDERS and PEBBLES.

GESCHIEBE und GEROLLE. (Germ.)

These may consist of very various materials ; and when united by a
cementing medium, they form a conglomerate rock.

Erratic Slocks and Boulders are of especial geological im-
portance ; they are sometimes only partially rounded, and
they are dispersed over the earth's surface, far from their
parent rocks.

They consist of very different kinds of rock, and have for the
most part been transported to their present position by means
of glaciers or of drift-ice.

41. BRECCIA.

BRECCIE. (Germ.)

BRECHE, BRECCIOLA, Brongniart. (Fr.)

A rock composed of angular fragments of minerals or
solid rocks cemented or bound together by some matrix
or binding medium. [BKECCIOLA when the frag-
ments are small.]

FRAGMEXTAL GROUP. 305

Breccias, like conglomerates, may consist of the most
various substances, both in their fragmental ingredients
and their connecting medium, whence a similar richness
in the number of varieties, which are too numerous and
manifold to admit of classification. They must in each
case be named according to the character of their in-
gredients thus, quartz-breccia, gneiss-breccia, limestone-
breccia, &c. or according to the nature of their matrix,
as in the case of conglomerates.

Breccias are geologically important, because in every
case the fragmental parts must be of greater age than
that of the rock itself; also because they indicate violent
disruption of the rocks in their immediate neighbourhood,
and from the circumstance that very angular fragments
can never have travelled very far from the place of their
original bedding.

The following kinds of breccia are noteworthy on geo-
logical grounds.

Geological Varieties.

(1) FRICTION BRECCIAS. ] These are breccias formed

REIBUNOSBRECCIEN. (Germ.) I at the maroin of eruptive

BKfcCHES DK FIU,N (DK FROTTEMHNT). ^ . ^ Jg ftt t he time pf

J their eruption ; the matrix

of the breccia consisting of the substance of the igneous rock,
and the enclosed fragments being pieces of the rocks broken
through. These breccias are very frequently found at the
margin of porphyries, greenstones, basalts, trachytes, &c., and
1 may be designated accordingly.

Simler has given the name of Metamixite to these contact
formations. (Ueber Petrogenese, 1862.)

(2) QUARTZ-BRECCIA. \ Consisting of fragments of quartz

QUARZBROCKENFBLS. (Germ.) \ bound together by quartz or by
BRfccHE 8IUCEIT8B. </v.) f f erru ginous quartz. It very fre-
quently occurs as the filling up of wide gaps or clefts in
the crystalline schists, e.g. at Schwarzenfels in the Erzgebirge.

(3) BONE BRECCIA. ] A breccia whose fragmental por-

KNOCHKNBRECCIE. (Germ.) L tions chiefly consist of fossil bones.

BHfeCHE 1 OSSKMKNTS. (Fr.) j frequently found in clefts ^ cft .

vities of limestones, and, as it would appear, always of very
recent origin.

(4) HASELGEBIRGE (Germ.) is the name griven to certain breccia-

like rocks occurring in connection with the rock-salt forma-
tions of the Northern Alps. They consist of clay as matrix,
and contain very various fragments of the neighbouring rocks.
They have probably arisen from the breaking in of the roof
of cavities caused by partial washing away of the rock-salt.
X

306 SEDIMENTARY KOCKS.

TOPAZ ROCK. } This rock may be treated as a breccia,

TOPASFELS.' (Germ.) I and is therefore placed here. We

TOPAZOLITHE, TOPAZOGEME, f s } 1& \\ a i 80 no tice it again as a sepa-

J rate rock (page 324, post).
Cotta, on Breccia formation, in Geolog. Fragen, 1858, p. 186.

Appendix.

ACCUMULATIONS OK HEAPS OF LOOSE FKAGMENTS OF STONES OR
RUBBISH.

These may be naturally or artificially formed, e.g. naturally
by the fall of a rock or mountain, or artificially by the l tip-
ping ' of stones at the mouth of a mine or elsewhere.

42. TUFA or TUFF.

TUFFBLLDUNGEN. (Germ.)
TUF. (Fr.)

Accumulations of lapilli, fragments, ash, or other sub-
stances, ejected from volcanoes, and more or less firmly
compacted together.

We can hardly, within reasonable limits, give a more
definite description of these rocks, on account of their
great variety both of state and composition. They may
be best understood by a description of the mode of their
origin ; volcanoes during their eruptions cast out masses
or lumps of lava, usually scoriaceous so-called ( bombs '
which are for the most part rounded, and vary in size
from the size of a man's fist to that of a human head and
larger ; but besides these bombs, volcanoes also emit what
is termed ' volcanic sand,' and even dust-like particles of
lava or ( volcanic ash,' often accompanied by non- volcanic
fragments which have been torn away from the sides of
the crater.

In still weather all such products fall on the slopes, or
in the immediate neighbourhood of the volcano ; but in
storms of wind they are often borne to a considerable dis-
tance, and so become separated according to their size and
weight. If the volcano be in the neighbourhood of the
sea, or of a freshwater lake, then they often fall into
these.

They are likewise frequently washed down by floods
of rain from the steeper slopes of the volcano, and are so
accumulated in one or more separate localities. By such
means they cover the land with a loose stratum, or with
the assistance of water they become more or less regularly

FRAGMENTAL GROUP. 307

stratified, form deposits of various thickness ; and some-
times trunks of trees or other substances become imbedded
with them. Again, if these volcanic products are de-
posited in considerable quantity, either in the sea or
freshwater basins, then they envelope such remains of
coral, shells, fishes, and the like, as may happen to come
in their way, these latter being in such case converted
into fossils.

Such is the origin of volcanic tufa, which may therefore
either be a land formation, or a freshwater, or marine
formation. At some very lofty volcanoes, especially some
near Quito, there occur streams of mud, which are oc-
casioned by the rapid melting of the mountain snow or
the bursting of some internal reservoir of water. The
violent rush of water carries with it all loose materials
with which it comes into contact, converting them into
mud, which is deposited where the mountain slopes are
most gradual. The mass thus formed is called Moja. It
is, however, nothing but a kind of volcanic tufa.

Tufas sometimes contain fragments of various kinds,
large and small, angular and rounded, confusedly mingled
together ; sometimes the fragments have become sorted
according to size and weight, so that we find some tufas
consisting entirely of fine dust resembling claystone ;
others of small grains resembling sandstone ; and others,
again, of only coarse fragments resembling conglomerate.

It would be impossible to distinguish and arrange the
manifold varieties of tufa systematically ; we can only in
some measure indicate the local designations for particular
varieties, commencing with those belonging to active
volcanoes, then instancing those associated with the older
volcanoes, or even, as sometimes happens, with plutonic
igneous rocks. A genuine plutonic, i.e. subterranean,
formation of tufa, is not to be imagined as possible.
Therefore, as we nevertheless sometimes find tufas con-
nected with and belonging to plutonic rocks, for instance
with greenstones and quartz-porphyries, we must assume
that these greenstones and quartz-porphyries formerly
had an upper volcanic portion to which the tuff formations
properly belonged, but which has since been destroyed
and washed away, whilst a part of the tufas have been
preserved, being perhaps protected by other deposits.

x 2

308 SEDIMENTARY ROCKS.

We have no tufa formations belonging to the granites,
because they never reached the surface in their melted
state, and tufas and breccias are the result of eruptions
which have taken place at the surface of the earth, or
beneath the waters of shallow seas.

(A) VOLCANIC TUFAS, BASALTIC AND TRACHYTIC.

The materials of which they consist are slags, lapilli, ash,
fragments of pumice, or lava mixed with other substances.
Their structures are rough, earthy to compact, arenaceous,
conglomeritic, or breccian.

(a) PEPERINO. ) Grey wackenitic matrix, enclosing laminae

PEPERIN. (Germ.} j o f black mica and grains or crystals of

augite, leucite, and magnetic iron-ore;

sometimes with angular fragments of basalt, leucite rock,

limestone, and the like. In the Albanian Mountains it occurs

in extensive beds of reat thickness.

BASALT-TUFA, and BASALT-CON-
GLOMERATE, or BRECCIA.

BASALT-TUFF und BASALT-CONGLOMERAT
oder BRECCIE. (Germ.)

TUF BASALTIQUE, CONGLOMERAT BASAL-

Fragments of basalt of
very various sizes, joined
together by pulverised

particles of basalt or by

TIQUE. ~(Fr.) clay, or some other de-

composed rocky matter. This kind of tufa often likewise
contains fragments or pebbles of other rocks, pieces of augite,
hornblende, olivine, mica, and magnetic iron-ore, grains of
glauconite, &c. It is occasionally penetrated by nests and veins
of calcspar, aragonite, or sparry iron-ore. It frequently con-
tains fossils.

pALAGONm-uFF. (Germ.) f v . Waltershausen to a variety of basalt
tufa, first observed by him near Pala-

gonia in Sicily, It is probably the product of transmutation
from ordinary basalt tufa, taken place under water. The prin-
cipal mass of this rock consists of a peculiar mineral formation
termed palagonite, which shapes itself into compact masses,
or into aggregates of small grains ; and it encloses fresh pieces
of basalt, dolerite, or basaltic amygdaloid. Palagonite itself is
amorphous, resembling pitch, with a yellow to blackish-brown
colour, vitreous to greasy lustre, conchoidal or splintery frac-
ture. H. 4-5. Spec. grav. 2-4 2-6. It is a hydrous silicate
of iron, alumina, lime, and magnesia, with little potash or soda.

(d) PUZZULANA. 1 A loosely coherent deposit of volcanic sand,

PUZZULAN. (Germ.) \ ve ry useful in the construction of hydraulic
POUZZOLANE. (Fr.) J mo rtars

(<?) TRACHYTE-TUFA, TRACHYTE-CON- -j Fragments or pebbles of

GLOMERATE, TRACHYTE-BRECCIA. trachyte are more or less

TRACHYTTUFF, TRACHYT-BRECCIE und h firmly cemented together

CONGLOMERAT. (Germ.) "K -fi l i 'A

CHYTIQUE. (Fr.) tides of the same ma-

terial. Or the matrix oc-
curs alone as a compact fine earth mass of a white, yellow, or
even green colour. Sometimes it contains pieces of sanidine

FRAGMENTAL GROUP. 309

hornblende, or magnetic iron-ore in a better state of preserva-
tion. In clefts and fissures of the tuft' an opal-like stone has
found itself at Kaschau in Hungary; for instance, precious
opal. Here and there it contains impressions of plants and
other fossils.

(/) PUMICEOTTS TUFA, PUMICEOUS SAND \ "White, yellow, or grey;
and CONGLOMERATE. f its texture earthy to

BIMSTEINTUFF, BiMSTEiN-SAND und CoNOLo- T compact, very rough

tptte feel. It con-
sists of an aggregate
of pulverised particles of pumice-stone, frequently enclosing
fragments of the same or of trachyte. As accessory ingredients,
it also contains laminae of mica, crystals of felspar, grains of
magnetic iron-ore, less frequently quartz and garnet. The fine
pumiceous tufa has sometimes formed itself into small con-
centric globules (pisolites), as happens at the present day when
rain occurs during a volcanic shower of ash.

(g) TRASS (Rhine), PAUSILIPPO TUFA\ Are only local varieties

(Sicily), TOSCA (TenerifFe). I of pumiceous tufa which

TRASS (DucK&TEiN), PAUSILIPFTUFF, TOSCA. Y sometimes contain car-

I*J?TOTimP40Bum (Fr.) ) bonised trunks of trees

and other organic re-
mains, and usually are well adapted to the construction of
hydraulic mortars. Much of this pumiceous tufa seems to be
the product of volcanic mud-streams, and therefore to answer
to the moja of South America.
(h) ALUM-STONE, ALUM ROCK (Tolfa). } Is the name given to

ALAUNSTEIN, ALAUNFELS, TOLFA. (Germ.) f a certain argilo-tra-

' chytic tufa, containing

alum, occurring at Bereghsacz, in Hungary, and at La Tolfa,
in Italy, &c. But much of what has received this name is
probably only decomposed trachytic rock, and therefore not a
genuine tufa.

(i) PHONOLITE-TUFA, and CON-X Fragments or pebbles of pho-

GLOMERATE. nolite are united together by

PHONOUTTUFF und CONGLOMERAT. L a n aggregate compound of

TuF^^JoijTHiQUB, CONGLOMERAT hy particles, and of earthy

PHONOLITHIQUE. (fr.) > to compact texture, sometimes

containing sanidine, hornblende, augite, &c. It is found, e.g.,

in Hogau and at the southern foot of the Erzgebirge.

(B) TUFF FORMATIONS OF PLUTONIC ROCKS.

(&) PORPHYRY-TUFF, or FELSITE-TUFF \ Sometimes called clay-
(FELSPATHIC ASH), Jukes. [ stone; a compact ag-

PORPHYRTUFF oder FELSTITUFF. (Germ.) [ cn-egate of felsitic parts,

TUF PORPHYRIQUE OU FEUSPATHIQUE. (Fr.) J ^^^ deC ompOSed,

fracture earthy, often variegated in colour, seldom distinctly
stratified, but sometimes containing fossil plants, especially
trunks of trees. At Chemnitz, in Saxony, where this tufa occurs
as the lowest member of the Rothliegende, it is supposed to
belong to the quartz-porphyries of that district- It is, how-
ever, very diificult to distinguish these rocks in themselves
from ordinary claystones, or Jrom certain products of decom-
position of compact or porphyritic felsitic rocks.

310 SEDIMENTARY ROCKS.

Porphyry-tuff sometimes encloses fragments and pebbles of
quartz-porphyry, and thereby passes over into a kind of por-
phyry-breccia or conglomerate. At Fidha, in Saxony, there
occurs a porphyry-breccia of this description, the matrix con-
sisting of crystalline particles of felspar.

(T) GREENSTONE-TUFF, and GREENSTONE-CONGLO-] A compact ag-

MERATE (GREENSTONE-ASH). ( gregate of pul-

GRUNSTEINTUFF und GRUNSTEINCONGLOMERAT. (Germ.) [ verised or sand-

TUF DIOBITIQUE et CONGLOMERAT DIORITIQUE. (Fr.) J -i-i ,- -i P

greenstone j fracture earthy ; colour grey or brownish-green,
sometimes enclosing fragments or pebbles of greenstone, and
frequently organic remains.

At Planschwitz, in Saxony, greenstone-tufa is imbedded
between strata of greywacke slate, and contains many fossils of
the Devonian formation. Probably much of what in Nassau
has been called schalstein belongs to greenstone-tufa. On
account of the indistinct character attached to the name schal-
stein, we have preferred to treat it separately.

In Southern Tyrol, in theFassa district, Von Richthofen
has lately made distinctions between eruptive tufas, sedi-
mentary tuffs, and regenerated tuffs, but they all belong
to augite rocks, and take their geological rank amongst
the deposits of more recent Trias formations.

References.

Natimann, on Porphyry-tufa, in the Erlauter. z. geogn. Karte

v. Sachsen, 1838, No. 2, p. 434
Gruner, Porphyry-tufa with Mica Crystals in the Dep. of the

Loire, Ann. des Mines, 1841, [3] vol. xix. pp. 98 and 122.
Beudant, Voyage min. et geol. en Hong-rie, vol. ii. p. 416.
v. Oeynhausen, on Trass, in the Erlauter. z. geogn. Karte des

Laachner Sees, 1847.

Brongniart has given the name of Brecciole to certain basalt-
tufas of an arenaceous texture, in the Mem. sur les terr. des

sedim. sup. du Vincentin. Paris, 1823.
Sartorim v. Wattershamen, on Palagonittuff : Die submarinen

Ausbr. des Val di Noto, 1846, p. . 34 ; Skizze von Island,

1847, p. 76; Vulk. Gest. in Sicilien und Island, 1853, pp.

179 and 215.
Danvin, Palagonittuff on Chatham Island, in Geol. obs. on the

vole, islands, 1844, p. 98.
SandbergeT) Palagonittuff at Limburg in Nassau, in Geol. Verh.

d. Herzgoth. Nassau, 1847, p. 81.
Girard, Palagouittuff near Montpellier, in v. L. u. Br. Jahrb.

1853, p. 568.

v. Richthofen, Geogn. Beschr. v. Siid-Tyrol, 1861.
W. Evas, Felsittutf von Chemnitz Analyse, v. Leonh. u. Br.

Jahrb. 1861, p. 643.
Mitscherlich iiber den Alaunstein, Zeitschr. der geol. Ges. 1862,

p. 253.

FKAGMENTAL GKOUP. 31 L

Appendix.

Some part at least of what has been called schalstein belongs
to the tufa formations ; we therefore propose here to treat of all
the rocks to which this name has been applied, and we shall
subjoin a few observations on the so-called laterite.

43. SCHALSTEIN.

SCHALSTEIN. (Germ.}

So many rocks have been described under this name,
that we can only say in general that by it is understood a
laminated rock interspersed with small particles of calc-
spar. "We must distinguish them according to their
localities and the authors who have described them.

(A) SCHALSTEIN, or BLATTERSTEIN-SHALE. ) In Nassau. This

SCHALSTTEIN oder BLATTERSTEINSCHIEFER. (Germ.) } rock was certainly
first to receive the name, but it varies greatly in its character.
The base or matrix appears here to be a very fine somewhat
laminated greenstone-tufa, which contains calcspar in grains or
thin layers of green, grey, or variegated spotted colour. In
some places, however, this rock partakes of the character of
breccia, or is porphyritic by reason of crystals of labradorite,
or it is amygdaloidal, or is even penetrated by clay-slate and
chlorite-schist. In the Rhenish grauwacke district it usually
occurs in company with greenstone (diabase) a circumstance
which confirms its origin as a tufa formation.

Sandberger distinguishes the following varieties of
schalstein in Nassau:

) NORMAL SCHALSTEIN.
CALCAREOUS SCHALSTEIN, with much calcspar.
SCHALSTEIN-BRECCIA, with calcspar as the cementing medium.

SCHALSTEIN-CONGLOMERATE.
e) SCHALSTEIN-AMYGDALOID.

(/) PORPHYRITIC SCHALSTEIN, with crystals of labradorite.

These are therefore varieties consisting of what under
other circumstances we should perhaps consider quite
dissimilar rocks, and which here are only classed together
because of their occurring together or under similar cir-
cumstances in the Devonian formation.

(B) SCHALSTEIN, or CALC-TRAP, which is a somewhat slaty diabase

or aphanite, containing grains of calcspar, and therefore may
be classed among those greenstones (see pp. 148, 159).

SCHALSTKIN VON ZELLE BET NOSSEN, oder ScHAi> I clay-slate containing 1

HTEINAHNLICHBK THON8CHIEFEB. (Germ.) j

loids of calcareous spar.

312 SEDIMENTARY EOCKS.

The name of schalstein has been used, or abused, for
many other kinds of rock, and hence we find a tolerably
rich literature on the subject.

References.

Stift, in v. Leonhard's Zeitschr. f. Min. 1825, vol. i. pp. 147 and

*236 ; also in Geogn. Beschr. d. Herzogth. Nassau, 1831,

p. 468.

Oppermann, Dissert, iiber den Schalstein und Kalktrapp, 1836.
Dollfus and Neubauer, Analyses of Schalstein in the Journ. f.

Prakt. Chemie, 1855, vol/lxv. p. 199.
Eglinger, Analyses, in the Jahrbuch des Ver. f. Naturk. in

Nassau, 1856, No. 11, p. 205.
Murchism and Sandberger, Transact, of the Geol. Soc., second

series, vol. vi. p. 249.
v. Dechen, in Nb'ggerath's Rheinland Westphalen, 1822, vol. ii.

p. 71 5 and in Archiv f. Miner. Geogn. &c., vol. xix. p. 516.
Hausmann, on the Formation of the Harz Mountains, 1842,

p. 23.
Sandberger, Ubers. der geol. Verh. des Herzogth. Nassau,

1847, p. 33.

Gumprecht, in v. L. u. Br. Jahrb. 1842, p. 825.
Naumann, Erlauter. d. geogn. Karte v. Sachsen, 1836, No. 1,

p. 60.

Appendix.

We shall here append a rock of somewhat doubtful
character.

LATEEITB. This is the name given by English geologists to
certain rocks of East India, which in part are red traps, very
much resembling brick, but others are the products of the
decomposition of crystalline schists. Upon such uncertain
data, of course, no definite character can be established for a
rock.

References.

GumprecMs Zeitschr. f. Erdkunde, vol. v. p. 160.
According to v. Richthofen, the laterite of Ceylon is decom-
posed calcareous gneiss : v. Leonhard's Jahrb. 1862, p. 739.

313

CHAPTER IV.

ROCKS OF SPECIAL CHARACTER OR BEDDING.

WE propose under this general head to gather together
several formations of very various character, but subor-
dinate extent in point of comparative bulk hardly im-
portant enough to be considered altogether essential
ingredients of the earth's crust. Several of the rocks we
have classed under previous heads are likewise compara-
tively insignificant in point of their extent, but they form
part of larger connected groups, and so enter into the
family of the great rock formations of the globe. In this
chapter we have to deal with more separate and discon-
nected formations, frequently of local character only, and
which we rather force into groups for the sake of conve-
nience than in conformity with the nature of their origin,
which is very various and in many cases doubtful. Some
are of igneous, some of sedimentary or metamorphic
origin, but others, in their bedding and composition, differ
so much from the greater part of the rocks of each of
those three classes, that we are compelled to regard them,
for the present at least, as problematical formations, al-
though we may account for several by supposing a con-
currence of extraordinary and exceptional circumstances
at their first origin or during their mutations.

We have not, therefore, attempted to classify these
special rocks according to origin ; but have arranged
them somewhat arbitrarily in groups in the following
order :

1. Serpentine rocks.

2. Garnet rocks.

3. Greisen and schorl rocks.

4. Coal and carbonaceous rocks.

5. Ironstone rocks.

6. Various minerals as rocks.

314 MISCELLANEOUS DIVISION.

SERPENTINE GROUP.

These are rocks, probably, of very various original
character, but which have all undergone the same special
transmutation. This process has not been one of increase
of crystallisation, nor of actual decomposition : it seems to
have simply consisted in the absorption of magnesia, just
as we know has happened in the case of many and various
minerals. These have been converted from their original
state into serpentine, steatite, or other magnesian com-
pounds, and are pseudomorphs retaining the form of their
original crystallisation.

44. SERPENTINE, OPHIOLITE.

SERPENTIN, OPHIOLITH. (Germ.}
SERPENTINE. (Fr.)

A compact rock } dull in fresh fracture, soft, with greasy
feel, usually dark-green or brown.
Spec, grav ; '''' .' . 2-5 2-7.

It may be doubted whether serpentine exists as an
original and independent mineral ; for the crystals with
amorphous fracture, which some mineralogists call ser-
pentine, according to others are nothing more than
pseudomorphs of chrysolite or some other mineral. If,
however, the existence of serpentine as an independent
mineral were established, the question still remains
whether the rock which we term serpentine is to be re-
garded as consisting of such mineral, because, although
its composition is similar, in many cases it may be dis-
tinctly shown that the rock has been derived by trans-
mutation from other rocks. We know of undoubted
pseudomorphs of hornblende, felspar, augite, &c., con-
sisting of a substance bearing at least a very close resem-
blance to serpentine, and actually so called. We will not
pursue this mineralogical question further, but proceed
to the description of the rock.

Serpentine rock consists of two-thirds silicate of mag-
nesia combined with 12 21 per cent, of water. It also
contains some protoxide of iron, and this, as well as the
water, enters into combination with the silica, supplanting
a part of the magnesia : the proportion of silica varies
from 38 to 43 per cent. ; the magnesia from 34 to 44 ;
lime, clay, manganese, bitumen, and carbon are only

SERPENTINE GROUP. 315

present in small quantity. The mass is so soft and trac-
table, and yet so tough, that it admits of being cut into
various shapes or turned with the lathe. Its unctuous
feel is a very characteristic property of serpentine, and is
caused by the great quantity of magnesia which it con-
tains. Probably the numerous friction surfaces which
often divide the rock in all directions are also owing to
the presence of magnesia. These surfaces have a resinous
lustre and are sometimes striped. The rock is usually of
a dark-green colour, but some varieties are light-green,
grey-green, brown, reddish-brown, or almost black, and
the rock sometimes presents rapid alternation of colour,
causing spots, flames, or vein-like markings.

The principal mass of serpentine often porphyritically
encloses many minerals of various kinds. The most fre-
quent are pyrope, or magnesia-garnet, sometimes accom-
panied by talc, less frequently bronzite, schiller-spar,
chlorite, mica, magnetic iron-ore, pyrites, mispickel,
chromic iron-ore, and very rarely (in the Ural) native
platinum. The quantity of magnetic iron-ore is ex-
ceptionally so considerable, as to influence the magnetic
needle ; for instance, in the Fichtelgebirge, where, how-
ever, the rock is not a very characteristic serpentine. The
mass of serpentine rock is frequently penetrated by veins
consisting of fibrous serpentine (asbestus), chrysotile,
chlorite, or picrolite.

Somewhat more rarely there occur veins or nests of
calcspar, calcareous magnesian spar, magnesite, saponite,
pyknotrope, dermatine, talc, brucite, volknerite, horn-
blende, strahlstein, quartz, chalcedony, jasper, chrysoprase*
opal, pyrites, chalcopyrite, chromic iron-ore, magnetic
iron-ore, and native copper.

Varieties in Texture.
(a) COMMON COMPACT SERPENTINE.

IMI-IITER SERPENTIN. (Germ.)

i-KUPENTINE COMPACTS. (Ft'.)

(6) PORPHYRITIC SERPENTINE. ) Often with crystals of py-

PORPHYRARTK5KR SERPENTIN. (Germ.) \ TOPC.

SERPENTINE PORPHYROU>E. (Fr.) '

SCHIKFRIGER SERPENTIN. (Germ.) \ Of imperfect thick cleavage.
SERPENTINE SCHISTEUSE. (Fr.) )

(d) VEINED SKKI-KNTINE.

GBADERTER SERPENTIN. (Germ.)

SEKPKXTLNE BBECUIVORKE, OPHIOUTHB, Drongniart. (Fr.)

316 MISCELLANEOUS DIVISION.

Inasmuch as all serpentine is probably the product of
the metamorphosis of some other rock, it need hardly be
said that transition states of this metamorphosis are found
which differ not only from the extreme result of the pro-
cess of change the genuine serpentine but from each
other. If, however, this theory of the origin of serpen-
tine be well founded, we cannot always succeed in deter-
mining with certainty the character of the original rock ;
perhaps in these cases the whole of the rock's mass has
undergone change, and if bordered by other rocks of a
different character, no trace is left of its original com-
position.

Several of the transition states of serpentine have
received specific names.

(e) FORELLENSTEIN (Germ.) or TROUT-STONE, at Neurode, in Silesia.
A compact labradorite mass, speckled with spots of serpentine,
which are frequently of angular form, and which Von Rath
believes to have formerly been crystals of labradorite now
converted into serpentine.

(/) RENSLAERITE is the name given by Emmons, in his American
Geology, 1855, to a serpentine-like rock, somewhat more crys-
talline than ordinary serpentine. Its colour ranges from greyish
white to green or black. Specific gravity, 2 - 87 ; composition,
59'2 silica, 32*9 magnesia, 3'4 protoxide of iron, 1 lime, and.
only 2-8 water.

(g) SCHILLER ROCK. \ The name given to a compound of
SCHILLERFELS. (Germ.) L schillerspar and serpentine, which goes
j over into ordinary serpentine. It oc-
curs at the Baste in the Hartz Mountains. It has a serpentine
matrix enclosing crystals of schillerspar of considerable size.
It also contains labradorite, augite, mica, chlorite, and pyrites.
Cocchi proposes that serpentine rocks should be designated
according to the particular rocks from which they sprang ; e.g.
diallage-serpentine, diorite-serpentine, granite-serpentine, &c.
This may be very advisable where it is possible.

Serpentine for the most part is jointed into irregular,
massive, or gnarled masses. Exceptionally it is of co-
lumnar structure, but not unfrequently it shows a kind
of stratification or tabular jointing. This latter may
have been occasioned by actual stratification, since ser-
pentine may well have arisen from stratified rocks. It is
most frequently found in irregular and subordinate beds
between strata of crystalline schist, but it also occurs in

SERPENTINE GROUP. 317

uncrystalline rocks both in the massive form and in veins.
The surface of the little round-topped hills which it often
forms usually shows a very scanty vegetation.

In some places, as already said, its transmutation from
other rocks is very evident, as, for instance, from gabbro
at Siebenlehn, near Freiberg ; from dykes of granite tra-
versing serpentine rocks near Bohrigen and Waldheim
in Saxony, where the main serpentine rock itself is not
improbably a transmuted granulite ; from chlorite-schist
at Zell, in the Fichtelgebirge, where the change does not
appear to be yet complete ; and from gneiss (probably),
or an eklogite rock in the gneiss, at Zoblitz, in the Erz-
gebirge. The processes and causes of the metamorphosis
of serpentine are doubtless very different to those of the
crystalline schists. When serpentine occurs in strata of
crystalline schist, it is usually of later origin than those>
and its conversion may have been occasioned by the con-
tinued infiltration of water, holding magnesia in solution,
during long periods of time. We are therefore unable to
class this rock with the crystalline schists any more than
we can with the igneous or sedimentary rocks. Ac-
cording to Jukes, many serpentines are metamorphosed
magnesian limestone. In the Engadine, a serpentine rock
has been lately found to contain a considerable proportion
of phosphate, so that it is proposed to use it as manure.

Serpentine has been recently discovered by Sir Wil-
liam Logan in the Laurentian limestones of Canada,
replacing the remains of the foraminiferal organism,
Eozoon Canadense.

References.

Scheerer, Mineral Serpentine, Poggend. Ann. 1854, vol. xcii.
p. 287.

Hauf/ht&n, Philos. Mag. 1855, vol. x. p. 253.

Websky, Krystallstructur des Serpentine, Zeitschr. d. d. geol.
Ges. 1858, p. 277.

T. Sterry Hunt, on the Serpentines of Canada and their asso-
ciated Rocks, Lond. Edin. and Duhl. Phil. Mag. vol. xiv.
p. 388, 1857. Quart. Jour. Geol. Soc. vol. xxi. p. 67.

v. Rath, Forellenstein, Poggend. Ann. vol. xcv. p. 652.

Cocchi, in v. L. u. Br. Jahrb. 1857, p. 600.

Emmon*, in Americ. Journ. of Sc. 1843, vol. xlv. p. 122.

A. Streng, Serpentin in Gabbro von Neurode, v. Leonh. u. Br.
Jahrb. 1864, p. 257.

C. W. Fuchs, Schillerfels bei Schriestheim, v. Leonh. u. Br.
Jahrb. 1864, p. 326.

318 MISCELLANEOUS DIVISION.

GARNET GROUP.

The one property which these rocks possess in com-
mon is, that they all contain garnet as an essential, some-
times a predominant, constituent. The minerals with
which the garnet is combined are various, such as am-
phibole, pyroxene, felspar, mica, dichroite, &c. Garnet
rocks frequently occur in subordinate masses, often of
irregular shape and doubtful origin, in strata of crystal-
line schists, or in granitic rocks. We include in this
group the following rocks : Eklogite, Disthene rock,
Eulisite, Garnet rock, Kinzigite, and Dichroite rock.

45. EKLOGITE, OMPHACITE ROCK, SMA-
RAGDITE KOCK, DISTHENE ROCK.

EKLOGIT, OMPHACITFELS, SMARAGDITFELS, DISTHENFELS.

(Germ.}
ECLOGITE, OMPHAZITE, Hauy. (Fr.)

A compound of green smaragdite and red garnet. The
smaragdite forms a finely crystallised matrix., usually
somewhat slaty or fibrous, in which the crystals of
garnet are porphyritically enclosed.

This rock, to which Haiiy gave the name of eklogite, is
usually very firm and coherent, difficult to break with
the hammer. Its fresh fracture presents a peculiarly
beautiful appearance, from the red garnets sparkling in a
light-green matrix. Its accessory ingredients cause it to
vary somewhat in different localities. The beautiful
eklogites of the district of Miinchberg, in the Fichtel-
gebirge, sometimes contain mica ; more rarely they con-
tain zoisite or some other variety of epidote, quartz,
pyrites, and magnetic iron-ore. In the eklogite of the
Sau-Alp mountain in Styria, zoisite and actinolite are
almost its predominant constituents, and it contains in
addition to the crystals of garnet some quartz, corinthine,
and disthene. On the island of Syra, the common eklo-
gite is found in layers or strata, alternating with a rock
consisting of a compound of disthene-garnet and mica of
a silvery white colour : this latter rock has been termed
by Virlet disthene rock ; we might, however, with equal
propriety, call it a variety of eklogite. A rock occurring
at HaslaUj near Eger, which has been sometimes called

GARNET GROUP. 319

eklogite, consists principally or in great part of idocrase
(so-called Egeran).

Eklogite most frequently occurs irregularly imbedded
in strata of crystalline schist, as, for instance, at Miinch-
berg, in the gneiss district of that locality. The direction
of its slaty texture there is in conformity with that of the
prevailing foliation of the schist, and we may therefore
doubt whether it should be regarded as a contempora-
neous formation with the gneiss, or as having forced its
way into the latter at a subsequent period. Owing to its
greater power of resistance to the decomposing influences
of the atmosphere, this rock usually forms prominent
knolls or rocks.

Virkt, in the Bullet, de la Soc. geol. 1833, vol. iii. p. 201.

46. EULISITE.

EULISIT. (Germ.)
EULISITE. (Fr.)

A compound composed of protoxide of iron, resembling
olivine, green pyroxene, and brownish-red garnet.

This name was given by A. Erdmann to a rock which
forms a bed of great thickness in the gneiss at Tunaberg,
in Sweden.

Erdmann, Forsok till en geogn. mineral Beskrifing ofver
Tunabergs Socken, 1849, p. 11.

47. GARNET ROCK.

GRANATFELS. (Germ.)
GRENATITE, Cordier. (Fr.)

A crystalline granular compound of garnet and horn-
blende, usually with some magnetic iron-ore.

Sometimes the brown or yellowish garnet (aplome)
predominates, so that the mass almost entirely consists of
a granular aggregate of that mineral ; sometimes, again,
the rock contains many other minerals besides the horn-
blende and magnetic iron.

This rock only occurs in subordinate matter ; e. g. in
the mica-schist on the Teufelsstein and Klobenstein, near
Schwarzenberg, in Saxony, where it forms small pro-
jecting rocks.

Cotta, Erlauter. z. geogn. Karte von Sachsen. No. 2. p. 225 ;
v. L. u. Br. Jahrb. 1844, p. 413.

320 MISCELLANEOUS DIVISION".

48. KINZIGITE.

KINZIGIT. (Germ.)
KINZIGITE. (Fr.)

A crystalline compound of black mica, garnet, oligoclase,
sometimes passing over into the compact state.

This is a rock which was discovered at Wittichen, at
the Kinzig in the Black Forest. It was formerly con-
sidered to be a garnet rock and so designated, but H.
Fischer pointed out its individual properties, and gave it
a separate name. He afterwards found the same rock at
Gadernheim and Auerbach, in the Odenwald, and certain
rocks occurring at Bodenmais in Bavaria and at Cabo de
Gata in Spain are considered by him to be closely allied
to it.

In some of the above-named rocks, cordierite, fibro-
lite, and mikrocline occur, the last as a substitute for
oligoclase.

Fischer, in v. L. u. Br. Jahrbuch, 1860, p. 796 ; and 1861,
p. 641.

49. DICHKOITE ROCK.

DICHROITFELS. (Germ.)

An irregular compound of felspar, dichroite, garnet,
and mica (the latter in small quantity) ; firm, dark-
coloured.

This rock is allied to dichroite-gneiss. It is found (e.g.)
forming a dyke in the granite of the Erlbachgrund, near
Kriebstein, in Saxony.

Naumann, Erlauter. d. geogn. Karte v. Sachsen, No. 2, p. 13.

GKEISEN AND SCHOKL GROUP.

The rocks of this little group are distinguished by their
consisting principally of quartz, frequently impregnated
with fine particles of tin-ore, or else associated with beds
or veins containing tin-ore. In addition to the quartz,
there occur in these rocks white mica, chlorite, or schorl
as essential ingredients, and wolfram, specular iron, and
topaz as accessories.

The following are the rocks included in this group :

1. Greisen, a compound of quartz and mica.

GREISEN AND SCHORL GROUP. 321

2. Z witter rock, consisting of quartz, chlorite, specular
iron- and tin-ore.

3. Schorl rock, a compound of quartz and schorl.

4. Topaz rock, a breccian variety of schorl rock, with
topaz.

50. GKEISEN.

GREISEN. (Germ.}
HYALOMICTE, Brongniart. (-F/-.)

A crystalline granular compound of quartz and mica.

This, therefore, is granite without felspar, or we may-
say it is the substance of mica-schist, without its foliated
texture and conformation. It is of somewhat rare occur-
rence. It actually passes into granite; that is to say,
some felspar, or at least kaolin, occasionally enters into
its composition. But no transitions into mica-schist are
known ; in other words, it shows no disposition to a fissile
texture ; it is always distinctly granular (coarse or fine^
grained).

The mica of greisen is chiefly lithia-mica. Some tin-
L ore likewise occurs as an accessory ingredient, and the
rock is frequently penetrated with or associated with
veins of tin-ore, as at Zinnwald, in the Erzgebirge, where
this rock occurs very characteristically. Less character-
istically it also occurs near Ober-Pobel, to the west of
Altenberg.

Greisen is of massive structure, without a trace of
stratification. Its constant association with beds and veins
of tin-ore, in the granite districts of Schlaggenwald, Corn-
wall, &c., and its resemblance to the zwitter, lead us to
the conclusion that special circumstances have led to its
formation from granite by decomposition of its felspar,
although in the coarse varieties it is difficult to conceive
how and by what substance the felspar has been replaced.
In this view we might regard greisen but as a variety of
granite. We have separately classed it and the other
tin-bearing rocks in a distinct group, because they pro-
bably all owe their peculiar properties to special and
analogous causes,' although these have not yet been satis-
factorily ascertained.

322 MISCELLANEOUS DIVISION.

51. ZWITTEK ROCK.

ZWITTERGESTEIN, SlOCZWERKSPORPHYR. (Germ.)

A dark-grey aggregate, rich in quartz, texture fine-
grained to compact ; its other ingredients are not to
be distinguished by the naked eye.

By help of the lens, we may recognise in the fine-
grained mass of this rock subordinate quantities of chlo-
rite, tin-ore, arsenical pyrites, and also some micaceous
iron combined with the quartz. To these the dark colour
of the rock is probably owing.

The tin-ore in Altenberg (the only locality where
the rock is known to occur characteristically) is called
zwitter, and the rock therefore was called Zwitter rock
by the miners there. The unsuitable name of Stock-
werksporphyr is another miners' term, given under the
erroneous belief that greisen belonged to the porphyries,
although it has no trace of porphyritic texture.

The celebrated f pinge ' of Altenberg is a large crater-
like hollow, formed by the falling in of extensive mining
works in this rock, which is worked for its tin-ore. At
the margin of this pinge may be observed the gradual
transition from fine-grained granite into zwitter rock. The
granite is first found to be penetrated by numerous and
very irregular cracks or fissures filled with quartz, and on
each side of the quartz there is usually a dark stripe of
from one quarter to one inch thick and upwards. These
stripes, on closer investigation, are found to be zwitter
rock, containing no felspar, although they merge gra-
dually into the surrounding granite, which is of the com-
mon kind. The stripes are evidently the result of influences
proceeding from the fissures, and towards the principal
mine they become broader and broader, so that very little
unconverted granite is left between the numerous clefts. At
length the last remnant of the granite disappears, the whole
mass having been converted into zwitter rock, in which,
however, the quartz veins still remain distinctly perceptible.
It would appear that the transmutation must have been
caused by some solution or vapour impregnated with tin
penetrating the granite through its many fissures.

Dr. Rube has carefully analysed several specimens of
the unchanged granite, of the dark stripes near the quartz,
and of the entirely converted zwitter rock. From these

GREISEN AND SCHORL GROUP. 323

analyses it has appeared that the composition of the dark
stripes and of the genuine zwitter rock were identical.
They each contain 3 p. c. silica and 2 p. c. potash less
than the granite. On the other hand, they contain
4 p. c. protoxide of iron, 2 p. c. alumina, 0'6 oxide of tin,
and 0*5 I/O lime more than the granite. It follows, there-
fore, that in addition to the ingredients which we have
above mentioned as being recognisable in the zwitter rock
it must also contain a silicate of alumina. The pene-
trating solution appears to have decomposed the felspar
and mica, and in their stead to have formed micaceous
iron-ore, chlorite, tin-ore, a silicate of alumina, and also to
have left a deposit of lime. The potash must have been
carried away in solution ; the silica was probably concen-
trated, at least in part, in the cleft of the rock, forming
the veins of quartz which we now see.

Cotta, in Berg- u. Huttenm. Zeitung, 1860, No. 1, and 1862,
p. 74.

52. SCHORLACEOUS SCHIST and SCHORL

ROCK.

SCHORLSCHIEFER und ScHORLFELS. (Germ.)
HYALOTOURMALITHE, Daubrte. (Fr.)

A crystalline compound of schorl and quartz, foliated
or granular to compact.

The schistose varieties are most prevalent, and we have
therefore placed them foremost ; the compact varieties are
rare, and in the absence of transition states they are dif-
ficult of recognition. As accessory ingredients, this rock
contains mica, chlorite, felspar, tin-ore, arsenical pyrites,
and exceptionally, in some places, topaz. These schorl
rocks are (like griesen) almost always accompanied by or
associated with beds containing tin-ore. The proportion
of silica which they contain is very unequal, and depends
on the prevalence of their quartz.

Varieties in Texture.

(a) SCHORLACEOUS SCHIST. Its somewhat indistinct foliated texture
is owing to the parallel disposition or distribution of the acicular
particles of schorl. The quartz sometimes forms itself into
contorted layers quite independent of the schistose texture.
This rock occurs (e.g.) in subordinate beds, alternating with
mica-schist at Eibenstock, in Saxony, where it is traversed by
veins of tin-ore.

T 2

324 MISCELLANEOUS DIVISION.

(b) GRANULAR SCHORL ROCK. This is either a tolerably uniform

compound (fine or coarse-grained) of schorl and quartz ; or it
consists principally of quartz, with small separate columnar
particles of schorl, which are frequently broken.

gredients are too intimately blended to be distinguished, as, for
instance, in the tin mining district of Cornwall.

Varieties in Composition.

(d) TOPAZ ROCK. \ Hitherto only known at the Schneck-

SS^^faT f stein > f t he Voigtland where it
(/y.) ) forms a dyke of considerable thick-

ness in the mica-schist. The composition of the rock is sin-
gular ; large fragments of schorl-schist (containing topaz), with
quartz, lithomarge, and geodes of topaz, are cemented together
to a kind of geodic breccia. The rock likewise contains tin-
ore, apatite, malachite, and azurite as accessories.

Von Eschwege has given the name of Carvoeira to a quartz
rock containing schorl, found in the Brazils.

References.

Freiesleben, Geogn. Arbeiten, vol. iv. p. 1.
Breithaupt, Paragenesis, in v. Leonhard's Jahrb. 1854, p. 787.
oase, Transact, of the Geol. Soc. of Cornwall, 1832, vol. iv.

pp. 240 and 373.

Naumann, Erlauter. d. geogn. Karte v. Sachsen, No. 2, p. 201.
Daubree (Hyalotourmalite), Ann. des Mines, 1841, 3 e ser.

vol. xx. p. 84.

CARBONACEOUS GROUP.

In these rocks carbon is the principal ingredient. They
are always of dark colour, varying between brown and
black. They are usually, but not always, combustible.
They are all of organic origin, and for the most part pro-
ducts of vegetable accumulation ; some (exceptionally)
perhaps are the result of the accumulation of animal
matter. The differences now exhibited are doubtless chiefly
owing to the degree of metamorphosis of the original
organic substance. If we start with this assumption, we
may class these rocks as follows, beginning with those
whose state is the least changed, and proceeding up to
those which are most completely metamorphosed :

1. Peat. The vegetable substance has undergone little
change. We are not authorised to conclude that all coal
has been formed from peat-mosses. On the contrary, we
know of much coal which is the undoubted product of
trunks and leaves of trees, and various other vegetable
substances.

CARBONACEOUS GROUP. 325

2. Browncoal or Lignite, containing much bitumen.

3. Common coal (German, Schwarzkohle), containing
much less bitumen.

4. Anthracite, containing very little bitumen.

5. Graphite, without any bitumen, and not combustible.
Some other differences result from foreign admixtures.
We observe from the above series that the first process

of change (from the peat to the browncoal) was accom-
panied by a development of bitumen, which in the subse-
quent stages of metamorphosis has again gradually disap-
peared, and become lost in all probability by evaporation.
The relative geological ages of the different coals in
general correspond with and confirm this view ; and the
only exceptions of which we are aware are capable of
explanation from special local causes. We may therefore
say that the varying proportion of bitumen contained in
the carbonaceous rocks furnishes us with a series which
at the same time is expressive of their geological age.

In addition to the above, and in some measure the com-
plement of the series, we have

6. Mineral pitch (including asphalte, elastic bitumen,
and mineral oil) consisting of the bitumen which has been
volatilised or distilled from bituminous coal. It is some-
times found separately bedded as a distinct rock, some-
times as an impregnation of other rocks, such as lime-
stone, shale, &c.

The following rocks we add by way of appendix to the
coal group, as bearing an affinity with it in respect of
their origin, or otherwise.

7. Bituminous shale (Brandschiefer), an argillaceous
shale containing very much bitumen, and frequently car-
bon. Also,

8. Kohlenbrandyesteine (burnt clay rocks), which are
not carbonaceous, but are the result of burning coal upon
clay rocks.

9. Guano and coprolite beds. The product of local
accumulations of animal excrement.

We have already stated that the usual and normal bed-
ding of the different kinds of coal entirely corresponds
with the theory of their origin and of the causes of their
different composition and structure. The individual ex-
ceptions only serve to prove the rule ; they may all be

326

MISCELLANEOUS DIVISION.

explained by special circumstances, and when so explained
are in fact necessary consequences of our assumed theory.
The following review of the most important coal forma-
tions will best explain our meaning :

Age.

Post Terti-
ary.

Tertiary.

Usual Coal-beds.

Peat-mosses and beds
turf in many places.

Chalk pe-
riod.

Oolite or
Jura pe-
riod.

Trias pe-
riod.

Coal pe-
riod.

Browncoal in North Ger-
many, Bohemia. Hessen,
&c.

Browncoal containing little
bitumen near Haring, in
Tyrol (Eocene).

Browncoal poor in bitumen
of the Gosau formation
in the Alps.

Bituminous shale and coal
of the Jura and Lias for-
mations in Germany and
England.

Lettenkohle, an impure
browncoal, containing
little bitumen, belonging
to the Keuper formation
in Germany.

Common black coal of the
Coal and Culm forma-
tions in England, Ger-
many, and France.

Transition Anthracite in Scotland and
or Grey- in Ireland,
wack e
period.

Still older. Graphite in the crystalline
schists at Passau in Ba-
varia, &c.

Exceptional Coal-beds.

Anthracite (with basalt) at
the Meissner, in Hessen.

Ordinary pit-coal or ( black
coal ' at Silthal, in Tran-
sylvania.

Ordinary black coal at
Ruszkberg, in the Banat.

Ordinary black coal at
Fiinfkirchen in Hun-
gary, and at Steierdorf
in the Banat.

Anthracite at Schonfeld,
Zaunhaus and Brandau,
in the Erzgebirge, in the
State of Ohio, adjoining
the porphyry at Walden-
berg, &c.

We see from the foregoing that in every geological
period in which any sedimentary deposits have taken
place, there have been accumulations of vegetable matter,
and that these have (occasionally at least) formed beds,

CARBONACEOUS GROUP. 327

and have afterwards become coal. But it is very remark-
able that as far as those countries which have hitherto
been geologically explored extend, the principal coal
formations are confined to two of the great geological
periods, viz., the Tertiary, to which the browncoals be-
long, and the Carboniferous, This would be a fact very
difficult to explain, if it were proved to be true for the
whole globe ; but as only about one-twelfth part of the
surface of the earth has been hitherto explored, we may
be permitted to doubt whether coal may not yet be found
in large quantity in other formations than those at present
known. In the interior of Africa, Asia, and Australia,
and South America, as well as under the ocean, very
extensive beds of coal may exist, which, together with
those we already know of the Chalk, Oolite, Trias, and
transition periods, would fill up all the apparent gaps, and
furnish as uniform a result with reference to the deposit
in all ages of material for coal-beds, as of that for any
other rock.

According to our present experience, we are authorised
to believe that the deposit of material for coal formation
lias taken place in a similar manner and under like con-
ditions in every period. We accordingly find a certain
petrographic uniformity or mutual relationship in the coals
of all ages. The coal-beds are almost universally found
interstratified and alternating with beds of argillaceous
rocks and sandstones, usually of grey colour (never red),
frequently with spherosiderite, or so-called clay-iron-
stone (Blackband) very seldom with limestone. The state
of these argillaceous and arenaceous rocks has undergone
a change corresponding to that of the coal. Their greater
compactness, solidity, and their laminated texture, almost
always correspond with the degree in which the bitumen
has been expelled from the coal, or, in other words, with
the geological age of the latter.

53. PEAT, TURF, BOG.

TORF, DARG. (Germ.)
TOTJRBE. (Fr.)

An aggregate of vegetable growth, interwoven and more
or less compressed and decomposed, of yellow, brown,
or black colour.

328 MISCELLANEOUS DIVISION.

The plants whose remains are usually found in peat
are of marshy origin, and in Germany usually spring
from Sphagnum. The moss is more or less compacted,
felt-like, or almost compact. Sometimes there are found
imbedded in it trunks of trees, or their branches, roots,
leaves, hard fruits, and the like ; some of which have
undergone little or no change. Besides these vegetable
ingredients, peat frequently contains earthy admixtures,
also red ochre, nodules of ' kieselguhr ' (an aggregate of
fossil infusoria), crystallised gypsum and pyrites, or
earthy particles of vivianite.

The following varieties are sometimes distinguished,
though they cannot be definitely characterised and sepa-
rated:

() PEAT-MOSS. \

FILZ- oder MOOSTORF. (Germ.) \ Loose and felt-like.

TOURBE FIBREUSE. (Fr.) J

(6) HEATH-TURF.

HAJDETORF. (Germ.)

RASENTORF. (Germ.)

(d) LEAF-TURF.

PAPIERTORF oder BLATTERTORF. (Germ.)

PECHTORF. (Germ.) I table matter having been much com-

'</) ! (Lm ' J Passed and transformed.

Beds of peat and turf are formed or grow before our
eyes at the present day ; in marshy places we may ob-
serve the mosses springing and growing out of the graves
of their predecessors. The beds of moss are found of
great depth as well as extent ; but they are only known
on the surface of the earth, and as belonging to the most
recent geological period. The older beds have been con-
verted into coal more or less bituminous, only very ex-
ceptionally, as, for instance, at Miihlhausen, in Thuringia,
do we find peat of an older date, covered there by diluvial
loam, not having lost its original character.

References.

Wigmann, iiber Entstehtmg, Bildung, and Wesen des Torfes,

18-37.
Winkler, iiber Zusaimnensetzung der Torfsorten des Erzge-

birges, 1840.

CARBONACEOUS GROUP. 329

Papius, die Lehre vom Torf, 1845.

AW, die Entstehung, Gewinnung u. Nutzung des Torfes, 1847.
Griesbach, Bildung des Torfes in den Emsmoosen, 1846.
Lutteroth, Umgegend von Miihlhausen, 1848, p. 25.
Gaudin, Diluvialtorf bei Biarritz, in v. Leonhard's Jahrb. 1857,
p. 84.

54. BROWNCOAL or LIGNITE.

BRAUNKOHLE und LIGNIT. (Germ.)
LIGNITE.

A compact or earthy mass, very inflammable, brown or
black ; streak invariably brown.

Spec, grav ....... 1'2 1-5.

Browncoal essentially differs from ordinary black coal
in containing a much greater proportion of bitumen x
or the elements which with carbon form bitumen. Hence
its brown colour and streak, its greater inflammability
than ordinary coal, and likewise its burning with more
smoke and smell. Even when very dark-coloured, its
difference from the ordinary coal may be made to appear
by boiling its powder with potash-ley, which it will colour
brown.

Browncoal contains 55 to 75 p. c. of carbon, with hy-
drogen, oxygen, and nitrogen, and earthy admixtures in
very various proportions. Some varieties contain pro-
portionally little bitumen, and so form transition states
between brown and black coal.

The following minerals sometimes occur as accessories :
amber, mellite, asphalte, gypsum, calcspar, pyrites, and
lenticular particles of clay-ironstone.

Varieties in Texture.

(d) COMMON BROWNCOAL. \ ~

GEMEINE DICHTE BRAUNKOHLE, I Compact with dull fracture and

M i ( KKOHLE. (Germ.) brown colour.
LIGNITE COMPACTE, Fayet. (Fr.) '

(6) EARTHY BROWNCOAL. } -^ ., , . ,

ERDIOE BRAUXKOHLE, STRETCH- [ E ^ pulverised to a brown

KOHLS. (Germ.) powder.

LIGNITE TERUEUX. (Fr.)

(V) RESINOUS BROWNCOAL. ] Very compact and dark, almost
PECHBRAUNKOHLE. (Germ.) I black, and its fracture shining like
LIGNITE RESINEUX. (Fr.)

(d) LIGNITE, BITUMINOUS WOOD. ] Retaining the texture of the
LIGMT. IIITUMINOSES HOLZ. (Germ.) I original wood from which it
LIGNITE, orruMiNEux. (Fr.) J w

330 MISCELLANEOUS DIVISION.

(e) LEAF COAL or DYSODILE. ) Laminated in consequence

BLATTERKOHLE, PAPIERKOHLB, oder I O f jt s origin from leaves of
Lia^S^m^S^uDYsoDiL. (Fr.) \ trees, or of strong pressure

' of its vegetable particles
causing a similar effect.
(/) MOOR COAL. )

MOORKOHLE, STREICHKOHLE. L Felt-like and resembling turf.
LIGNITE PICIFORME. (Fr.) '

Varieties in Composition.

(g) COMMON BROWNCOAL.

(K) BROWNCOAL WITH LITTLE BITUMEN, to which many of the brown-
coals of the Alps belong ; e.g. the Molasse coal of Miesbach and
Tolz, and the Eocene coals of Haring iii the Tyrol. Their ap-
pearance is very like that of the ordinary black coal, even the
powder of their streak is very dark, and they only impart a
weak colour to caustic ley.

(i) IMPURE BROWNCOAL combined with much earthy matter, passing
over into bituminous shale. To this class belongs, for instance,
the so-called Lettenkohle in the lowest division of the Keuper
formation.

(k) ALUM EARTH. \ An earthy impure browncoal which con-

AUUJNERDE. (Germ.) I tains pyrites; and has a tendency to
decompose into alum and vitriol.

Browncoal is frequently found in Tertiary deposits,
exceptionally, however, in older ones ; even in the Ter-
tiary strata it is sometimes found to have been transmuted
into anthracite by the influence of heat from adjoining and
more recent igneous rocks ; as, for instance, at the Meissner,
in Hessen, where it is found in contact with basalt, or it
assumes a character very similar to the ordinary black
coal, as in many Tertiary browncoal beds of the Alps.

Browncoal may be clearly proved to have had its ori-
gin in accumulated remains of plants. Some browncoal
is the product of the conversion of beds of peat and turf,
some of more distinctly separate plants and parts of plants
washed together by floods. Subjected to pressure, a slow
chemical change took place in the mass (the formation of
bitumen). In some places, under special circumstances,
this change has proceeded more rapidly than ordinary, and
thus even in Tertiary strata we find it assuming a cha-
racter approaching to the state of the ordinary black coal.

It is hardly necessary to instance localities from
amongst the very many where browncoal is found in
Germany and elsewhere.

CARBONACEOUS GROUP. 331

References.
Zincken. Die Braunkohle und ihre Verwerthung. Hanover.

1865.
Giimbel, Analysen von Alpenkohlen, v. Leonh. Jahrb. f. Min.

1864, p. 52.

55. COMMON COAL, BLACK COAL, or PIT-
COAL.

SCHWARZKOHLE oder STEINKOHLE. (Germ.}
HOUILLE. (Fr.)

A compact black mass, in fresh fracture usually of resinous
lustre ; streak black, usually friable ; not so inflam-
mable as browncoal, but, like it, burns with Jlame,
smoke, and smell.
Spec. grav. .... V .' 1'3 1-6.

The substance of coal is principally carbon. It has less
of the elements of bitumen (oxygen, hydrogen, and ni-
trogen) than browncoal, but more than anthracite. It
forms a transition state between browncoal and anthracite,
and occasionally goes over into each. Like browncoal
and peat, it contains more or less earthy matter, by
which its value is depreciated. The following minerals
occur as accessories in coal : Pyrites, clay-ironstone (in
nodules or septaria), gypsum and calcspar ; frequently
also clumps of fibrous anthracite, stone-coal (Werner's
' mineral charcoal ' ).

Jukes observes : < In many ordinary coals little flakes
of mineral charcoal occur, retaining that part of the vege-
table structure called the vascular tissue. They are
called " mother of coal " by the colliers, in some places.
It is frequently seen in the form of a thin silky coating,
covering some of the surfaces of the coal. Its powder is
black, and if boiled with caustic ley, it scarcely colours
the latter.'

In coal districts a very great number of different kinds
of coal are distinguished according to their special values
for use ' indeed their varieties are often as numerous as
the different seams of a coal-field, and even the different
beds of a compound seam are readily distinguished from
each other by the colliers, who give particular names to
them ; and even small blocks of these varieties can be
recognised by them and identified with the seam or part
of a seam from which they are derived. Neither are

332 MISCELLANEOUS DIVISION.

these distinctions, which are only to be perceived after
long practice, unimportant, since these varieties have dis-
tinct qualities; some of them being better adapted to
smelting, and said to be " good furnace-coal ; " some of
them to blacksmith's work, or " good shop-coal ; " others
to various uses ; while only a few comparatively are best
fitted for domestic purposes, and are brought to market
by the coal-merchant.' Jukes.

6 Some idea of the immense varieties of coal may be
gained from an inspection of the Admiralty Coal Investi-
gation (Mem. Geol. Survey, vol. i.), as well as from the
varying qualities of those we are in the habit of using
daily in our houses. As many as seventy denominations
of coal are said to be imported into London alone.

( All these minute varieties are commonly included
under four principal heads : 1. Caking Coal-, 2. Splint
or Hard Coal] 3. Cherry or Soft Coal:, and 4. Cannel
or Parrot Coal.

f Caking Coal is so named from its fusing or running
together on the fire so as to form clinkers, requiring fre-
quent stirring to prevent the whole mass being welded
together. It breaks commonly into small fragments, with
a short uneven fracture. The Newcastle coal, and many
others from different localities, are caking coals. They
leave many cinders, and a dark dirty ash.

' Splint or Hard Coal is well known in the Glasgow
coal-field. It is not easily broken, nor is it easily kindled,
though when lighted it affords a clear, lasting fire. It
can be got in much larger blocks than the caking coals.

6 Cherry or Soft Coal is an abundant and beautiful
variety, velvet black in colour, with a slight admixture of
grey. It has a splendid or shining resinous lustre, does
not cake when heated, has a clear shaly fracture, is easily
frangible, and readily catches fire. It leaves compara-
tively few cinders, and its ash is white and light. It
requires little stirring, and gives out a cheerful flame and
heat. The Staffordshire coals principally belong to this
variety.

( Cannel or Parrot Coal is called cannel, from its burn-
ing with a clear flame like a candle ; and parrot, in Scot-
land, from its crackling or chattering when burnt. Can-
nel coal varies much in appearance from a dull earthy to

CARBONACEOUS GROUP. 333

a brilliant, shining, and waxy lustre. It is always com-
pact, and does not soil the fingers. Its fracture is some-
times shaly, sometimes compact. The bright shining
varieties often burn away like wood, leaving scarcely any
cinders and only a little white ash. The duller and more
earthy kinds leave a white ash, retaining nearly the same
size and shape as the original lumps of coal. Cannel coal
often takes a good polish, and can be worked into boxes
and other articles. Jet is an extreme variety of cannel
coal in one direction, as batt or carbonaceous shale is in
another. ' Jukes.

In Germany the varieties have been thus classed :

)

(a) GEMEINE STEIXKOHLE, or common Black Coal, compact with

resinous lustre.

PECHKOHLE (or Pitch-coal), compact with resinous lustre.
KANNELKOHLE (GAGAT), Cannel coal.

(d) SCHIEFERKOHLE, a bituminous shale, sometimes composed of

alternate layers of common coal and anthracite.

(e) RTTSSKOHLE (Sooty Coal), an earthy variety, dirty to the touch,

apparently consisting of a compound of common coal and
anthracite.

The origin of coal as a product of vegetable substances
is well established. The texture of the original plants
may sometimes be discovered under the microscope. Beds
of turf or parts of plants accumulated by flood- water have
furnished the material. Geinitz has even endeavoured to
explain the different structure of many coal-beds by the
differences of their original vegetable substance. At
Zwickau, in Saxony, and a few other places, he has dis-
tinguished the following varieties :

(a) FARNENKOHLE (Fern-coal), formed principally of ferns. To this

class belong the four uppermost notz of resinous coal (Pech-

kohle), at Oberhohndorf, many coals of Wettin, Lobejiin

and Ilmenau in Germany.
(/3) CALAMITENKOHLE (Calamitan Coal). To this the Russkohle

of Zwickau belongs, also the so-called mineral charcoal. It

is always very anthracitic and siliceous.
(y) SIGILLARIENKOHLE (Sigillarian Coal). To this belong the

Planitzflotz, and the deep ' Pechkohle ' near Zwickau.
(<;) SAGENNARIENKOHLE (Sagennarian Coal). To this belong, e.g.,

the older coals of Hainichen and Ebersdorf, in Saxony.

The following are the principal typical varieties in
France, according to Leplay :

334 MISCELLANEOUS DIVISION.

(A) HOUILLE SECHE.

(B) HOIJILLE MAKECHALE.

(D) HOUILLE MAIGEE.

Coal chiefly occurs in separate beds or subordinate
strata in the sandstone and argillaceous shale of the Coal
formation. It occurs, however, with very similar rocks
in somewhat older and in much younger formations.
Thus, for instance, at Hainichen in the Kulm formation,
near Fiinfkirchen, in Hungary, and Steindorf, in the
Banat, in the Lias formation ; at Ruszkberg, in the Banat,
between strata of the Chalk formation ; and in Silthal, in
the southern boundary of Transylvania, even in Tertiary
strata. The existence of black coal in these more recent
formations is to be accounted for by exceptional geological
circumstances, which have accelerated the process of
transmutation. The character of the plants themselves
may also have contributed to this result. We find that
the remains of Calamites have usually been converted into
siliceous anthracite ; and it is very possibje that the parti-
cular nature of the original plant-substance may have
affected the character of the coal in many other respects.
In certain localities again, the eruption of recent igneous
rocks have occasioned special phenomena of transmuta-
tion ; as, for instance, at Waldenburg, in Silesia, where
the porphyries have locally converted ordinary black coal
into native coke or anthracite.

Jukes observes : ( Microscopical examination exhibits
not only the vascular, but the cellular tissue of plants in
the substance of many coals, as was shown by Mr.
Witham in his work on the structure of fossil plants, and
by many observers since. All coals have a peculiar
structure, which bears a slight analogy to crystallisation.
They break or split, not only along the bedding, but
across it, along two sets of planes at right angles to the
bedding and to each other. The smooth clean faces pro-
duced by one of those cleavage planes are more marked
and regular than that produced by the other, as may be
seen by examining any lump of coal. The principal of
these division planes are called by the colliers the face
of the coal, the other being called the back, or end, of the
coal. They preserve their parallelism sometimes over

CARBONACEOUS GROUP. 335

very wide areas ; and the mode of working or getting the
coal, and the direction of the galleries, is governed by the
direction of the face.

' It is a structure which is probably the result of the
mineralising process undergone in passing from an or-
ganic to an inorganic state, and may be likened perhaps
to the " cleavage " of a mineral rather than to either the
true " slaty cleavage" of rocks, or to their " foliation" or
"jointing."' Jukes, p, 134.

References.

Tenney has contributed numerous analyses to the New York

Mining Magazine, 1856, p. 15.
Dawson, iiber die Pflanzenstructur der Steinkohle, in v. L. u.

Br. Jahrb. 1860, p. 571.
Neivberry, Entstehung der Cannelkohle, in v. L. u. Br. Jahrb.

1858, p. 852.
Geinitz, Die Versteinerungen der Steinkohlenformation in

Sachsen, 1855, and Geogn. Darst. der Steinkohlenformation in

Sachsen, 1856. Geologic der Steinkohlen Europas. Miinchen,

1865.
Goppert, iiber die Bildung der Steinkohle, im 4. Deel xx.

Tweede Verzammling von naturkundige Verhandlingen

Ton de Hollandische Maatschappij d. Wetenschappen te

Haarlem.

v. Lemhard in the deuts. Vierteljahresschrift, 1838.
Stein, Untersuchung der Steinkohlen Sachsens, 1857.
Ronald and Richardson, Chemical Technology, vol. i. p. 30, &c.
Lovetz, Mineralien in fossilen Brennstoffen, v. Leonn. Jahrb.

1863, p. 654.

56. ANTHKACITE.

ANTHRACTT oder GLANZKOHLE. (Germ.)
ANTHRACITE.

Slack with vitreous to half-metallic lustre, friable, streak
black, not easily ignited, and burns almost without
smoke and smell.

Spec, grav ...... . 1-5 1'7.

Anthracite consists almost entirely of carbon, and con-
tains very little hydrogen, oxygen, or nitrogen ; that is to
say, it is almost free from bitumen a native compact coke.
It contains earthy admixtures in various quantity, as is
the case with other coal. It also contains the following
accessory ingredients : pyrites, clay-ironstone, gypsum,
or calcspar in clefts.

There are scarcely any special varieties of anthracite to

336 MISCELLANEOUS DIVISION.

describe, unless we consider as such the transition states
between anthracite and common coal and the compounds
of the two with each other.

Extensive beds of anthracite are only met with in the
formations of the Greywacke (transition) and Carboni-
ferous periods. Locally, anthracite is sometimes asso-
ciated with browncoal. As a rule, beds of anthracite are
never met with in the Coal formation except in localities
where it appears to have been exposed to special plutonic
influences, as at Zaunhaus, Schonfeld, and Brandau in the
Erzgebirge, Sable and Beaulieu in Marne (France), at
the Stangen Alp in Styria, at Osnabruck, and in the
Alleghany Mountains. The normal position of anthracite
appears to be in the transition formations.

We are not aware of any treatises or works specially devoted
to the subject of anthracite. Much, however, respecting it will
be found in those cited under the head of coal.

57. GRAPHITE, PLUMBAGO.

GRAPHIT. (Germ.)
GEAPHITE. (Fr.}

A greyish-black aggregate, consisting of graphite ; texture
varying from flaky to compact ; soft, gives a black
streak (like lead pencil), greasy feel, not inflammable,
on the contrary capable of resisting fire.

Spec, grav 1-92-2.

Graphite or plumbago is carbon in a state nearly pure,
but differing very widely from that of the diamond. As
a rock, graphite contains admixtures of silica, clay, oxide
of iron, or sometimes small crystalline grains of other
minerals. By these admixtures its properties are, how-
ever, only slightly altered.

Graphite is the last member of the series of transmuta-
tion of the carbonaceous rocks, and is therefore principally
(and normally) found in subordinate beds in strata of
crystalline slate-rocks or as a local admixture in the same
rocks ; at Passau in Bavaria, in Bohemia, at Borrow-
dale in England, &c. It occurs exceptionally in granite,
and is even found to fill fissures in that and other rocks.

We might theoretically regard the diamond as a still
more perfect, that is to say more crystalline and purer
product of transmutation of the carboniferous series. Its
occurrence is however so rare, and so subordinate, that
we cannot here notice it further.

CARBONACEOUS GROUP. 337

References.

Pntisep, Graphite, Calcutta Gleanings of Science. Edin. Phil.

Journ. 1832, vol. xxvi. p. 346.

Glocker, Graphit, Erdmann's Journ. f. Chem. vol. vi. p. 330.
Rcgnault, Graphite, Ann. des Mines, 3e Se>. vol. xii. p. 161.
Herter, Graphitschiefer mit Pflanzenresten, Zeitsch. d. deut.

geol. Ges. vol. xv. p. 459.
Respecting the localities of the occurrence of Graphite, refer

to v. L. u. Br. Jahrb. 1833, p. 552 ; 1836, p. 595; 1838, p.

427; 1839, p. 448; Journ. d. Phys. vol. xliv. p. 301 ; Cor-

respondenzbl. des zool. mineral. Vereins zu Regensburg, 1827.

p. 29, and 1848, p. 158.

58. BITUMEN and MINEKAL PITCH.

BITUMEN und ERDPECH, ASPHALT. (Germ.}
BITUMJE, MALTHE, ASPHALTE.

A pitch-like mass, colour varying from dark-brown to
black) softens with heat.

Spec. grav. bitumen ..... 0-7 0*9
Mineral pitch ...... 1-1 1-2

This bituminous mass consists of 80*82 carbon, 910
hydrogen, and 8*9 oxygen and nitrogen.

Bitumen is very seldom found in mass in the interior
of the earth, but frequently as an accessory admixture in
calcareous, marly, or argillaceous rocks. On the surface
of the earth it occasionally forms small pitch lakes, as at
the Dead Sea, and in the island of Trinidad. To this
class belongs the petroleum, or rock-oil, which in North
America has been recently found streaming in great
abundance from the earth.

The origin of bitumen may be, and probably is, two-
fold. Bitumen or the gaseous elements of bitumen must
of necessity be disengaged where bituminous coals un-
dergo transmutation into coals of a less bituminous cha-
racter, or into anthracite. This bitumen may either
permeate the neighbouring rocks and make them bitu-
minous, or it may rise to the surface of the earth and
become a separate deposit of a fluid or semi-fluid sub-
stance. Again, bitumen will be formed wherever animal
remains gasteropods, fishes, and the like have been
enclosed by stratified beds of rock, and have become
transmuted. And thus some limestones, marls, or clay-
rocks may have become bituminous (being converted into
oil-slate, stinkstein, &c.). Or the bitumen contained in

338 MISCELLANEOUS DIVISION.

such rocks may, under the influence of heat or other
causes, again escape and become deposited elsewhere.

The occurrence of bitumen in nature, taken in con-
nection with the animal and vegetable fossils found in
coal, completes the evidence in support of the established
view of the origin of coal.

Mayer's Asphalt des Val de Travers, 1839, is the only sepa-
rate treatise on bitumen known to us. On rock-oil springs in
North America, Tide Petermann's Mittheilungen, 1861, vol. iv.
p. 151 : and Kane's Zeitschrift d. Erdkunde. 1862, vol. xii.
p. 279.

59. PYROSCHIST(#ww), BITUMINOUS SHALE.

BRANDSCHIEFER. (Germ.)

SCHISTE BITFMINEUX, MARNOLITE, Cordier. (Fr.)

Is the name given to very bituminous and thereby dark-
brown or black-coloured argillaceous shale, which,
although, it burns in five, yet, owing to its containing
so much clay, cannot itself be used as fuel.

These are best classed with the carbonaceous rocks,
together with which they frequently appear, and for which
they have sometimes even been mistaken. Their streak
is of resinous lustre ; they often contain distinct remains of
plants or fishes ; sometimes bitumen may be extracted
from them, and they are then sometimes called oil-slate
( Oelschiefer, Germ.; Schiste oleifere, Fr.).

Bituminous shales of this class are found in Germany,
especially in the lower Rothliegende, e.g. at Oschatz, in
the Lias of Wiirtemburg, and in the chain of the Weser,
and in the Brown-coal formation at many places.

Sterry Hunt, Bitumen and Brandschiefer (Pyroschist), Silliman
and Dana's American Journal, vol. xxxv. p. 157.

Appendix.

We may here add the burnt clays and the beds of
guano or coprolites. The first because they have ori-
ginated from the burning of coal-beds, the latter as accu-
mulations of organic matter.

60. BUENT CLAYS.

GEBRANNTE THONE, KOHLEISTBRANDGESTEIKE, ERDSCHLACKEU

und PORZELLANJASPIS. (Germ.)
THERMANTIDE, Cordier. (Fr.)

CARBONACEOUS GROUP. 339

These are local products of transmutation from clay
rocks produced by burning coal-beds. They are too un-
like in character to admit of a common definition. We,
therefore, separately describe a few principal varieties.

(a) BURNT ARGILLACEOUS SHALE. ) Hard, and resembling

GEBRAN-NTER SCHIEFEHTHON. (Germ.) I buck-colour, yellow,

AK.IILK acmonusE MfcTAMORPHiQUE. (Fr.)

nevertheless, still exhibiting the original laminated texture,
and impressions of plants of the slate-clay. At Planitz, near
Zwickau, in the Coal formation, and at Zittau in Saxony, in
the Browncoal formation.

(&) ROCKSLAG. \ By reason of greater heat the lami-

ERDSCHLACKE, KOHLEXBRAND- I n ated texture has been destroyed.

OLA SE BJ gSj (<?erm I and a scoriaceous slag-like texture

' arisen. Colours similar to the

burnt argillaceous shale. Found in the same localities.

PORZELLAXJASPIS. (Germ.) I trefied, porcelain-like, of

J greasy lustre, pearl-^rey,
bluish-grey, lavender-blue, or brown. The same localities.

61. GUANO and other COPROLITE BEDS.

GUANO und andere KOPROLITHENLAGER. (Germ.)
GUANO. (Pr.)

These deposits must also be enumerated amongst rocks.
In some localities they occupy a considerable place in the
earth's crust.

(a) GUANO. 1 Forms earthy white, grey, or yellowish-

GUANO. (Germ.) L brown accumulations of very disa
GUANO. (Fr.) J smell It ig chie{]y known ag ft

upon certain rocky islands of tropical climates. It consists
chiefly of the excrement of birds, and contains, according to
Boussingault, about 50 53 organic matter and ammonia-salts,
19 20 phosphate of lime, 3 phosphoric acid, 7 alkali, 1 2 silica
and sand, and 15 16 water. These accumulations attain a depth
of more than 100 feet, and frequently contain many other
organic remains of recent date.

References.

v. Etzel, in Gumprecht's Zeitschr. f. Erdkunde, vol. v. pp. 326

and 425, vol. vi. p. 152.

Tifhm, in Petermann's Geogn. Mittheilungen, 1859, p. 173.
Bvu**imi<iHlt, in Compt. rend. 1860, vol. li. p. 844 j v. L. u. Br.

Jahrb. 1861, p. 206.
Sandberger, Sombrero Phosphat (Guano), v. Leonh. Jahrb. 1864,

p. 631.
Jenisch, Guano verschiedener Lander, v. Leonh. Jahrb. 1864,

p. 866.

340 MISCELLANEOUS DIVISION.

(b) COPROLITE BEDS. ] Composed of excrements of fishes, reptiles,

KOPROLITHENLAGER. , and mammalia which inhabited caverns,
J some portions entirely petrified, but yet
containing much phosphoric acid. Found in many sedimentary
strata, also in caverns.

SCHWARZERDE, TscHOR- I although the 6 9 per cent, of organic
NOSEM. (Germ.) j admixtures con tained in this black
clayey earth do not altogether appear to have been derived from
excrement. In Southern Eussia this formation covers a great
extent, and lies on the surface of the earth. It attains a maxi-
mum depth of twenty feet. If subjected to the strong pressure of
overlying strata, it might possibly turn into bituminous shale.

References.

Murchison, Geology of Russia, 1845, p. 547.
Schmid, in v. L. u. Br. Jahrb. 1850, p. 350.
Wangenlieim v. Qualen, ibid. 1856, p. 75.

IRONSTONE GROUP.

These are rocks principally consisting of minerals rich
in iron, so called iron-ores ; these ores contain hydrated
oxide of iron, peroxide of iron, protoxide of iron, or car-
bonate of protoxide of iron, and accordingly are re-
spectively termed brown hematite, red hematite, magnetic
iron, and spathose or sparry iron. Of these varieties there
are many modifications both of structure and composition.
We append to this group pea-iron-ore (Bohnerz) a pisi-
form spherosiderite which consists of a silicate of protoxide
of iron.

These different ironstones occur in the form of strata
or layers, veins or irregular masses, imbedded between
other rocks of various geological antiquity. The different
ironstones themselves, however, have a certain difference
of geological character which may be expressed somewhat
as follows :

Hydrated Oxide of Iron, or Is sometimes an original formation and

Broicn Hematite, sometimes a secondary product. It

occurs in the form of layers, veins, or

irregular masses in formations or rocks

of every age.

Peroxide of Iron. Red He- Is in most cases undoubtedly a secon-

matite. dary product. It occurs in the form of

veins, layers, or irregular masses, but

usually only in the older formations

and rocks.

IRONSTONE GROUP. 341

Peroxide and Protoxide of Forms layers, veins, or irregular masses ;
Iron (combined} or Mag- these only in the crystalline schists
netic Iron-ore. and plutonic igneous rocks. Fre-

quently occurs also as an impreg-
nation in the volcanic rocks.

Carbonate of Protoxide of As clay-ironstone, it forms layers or

Iron, or Cathode Iron. concretions, principally in the Coal

formations ; as spathic iron, it forms

veins and irregular masses in various

different rocks.

Pea-iron ore (Bohnerz). Fills cavities and depressions in lime-

stones.

62. BROWN HEMATITE.

BRAUNEISENSTEIN. (Germ.)
LIMONITE, Beudant. (Fr.}

A compact earthy, porous, or fibrous aggregate of brown
iron-ore (limonite), yellowish-brown to black with
brown streak.

Brown hematite consists entirely, or at least essentially,
of hydrated oxide of iron (Fe*H 3 ) containing 85*6 per
cent, oxide of iron and 14 '4 water. It sometimes, how-
ever, contains admixtures of oxide of manganese, silica,
clay, or lime.

Varieties in Texture.
(a) COMPACT BROWN HEMATITE.

GEMEIXER DICHTER BRAUXEISENSTEIN. (Germ.)

LlMOXlTE COMPACTS. (Fr.)

(6) SCALY AND OCHRT BROWN IRON-ORE, YELLOW OCHRE.

ERDIGEB BRAUNEISENSTEIN, oder EISEXOCKER. (Germ.)
OCRK JAUNE. (Fr.)

FASRIGER BRAUNEISENSTEIN, oder GLASKOPF. (Germ.) i subordinate
HEMATITE mum CONCRETIONNEE FIBREUSE. (Fr.) j qua ntities, as

stalactite.

(d) REXIFORM IRON-ORE. ] Rounded concretions of brown

NIEREXERZ, REKERZ, STOCKERZ. L iron-ore, chiefly found in clay,
J and usually occurring in com-
bination with

(e) PEA-ORE. 1 Made up of globules (about the size

BOHNERZ. (Germ.) I o f peas), mostly of concentric struc-

M^^AI EN GRA^-S. (Fr.) J ^ ^Ael in a mass of clay,
iron-ochre, or limestone.
(/) OOLITIC BROWN ORE. ] Occurs in the form of

/ tioiis.

342 MISCELLANEOUS DIVISION.

(ff) BOG-ORE. A Whicli likewise differs in the

RASENEISENSTEIX, SUMPFERZ, QUELL- mo & e o f jt s occurrence from

55 R .)' WIESENERZ ' Ll - other varieties. It is a porous

MINERAIS DE MARAIS, LIMOXITE. j arenaceous deposit of brown

( Fr '^ iron-ore on the earth's surface,
and is created by springs or stagnant water. Frequently con-
tains some phosphoric acid.

Varieties in Composition.

(h) A. VARIETY RICH IN MANGANESE, \ ,

BLACK IRONSTONE. Frequently quite black,

MANGANREICHEB BRAUNEISENSTEIN, f therefore sometimes called
ScHWARZEisExsTErN. (Germ.) black ironstone.

LlMONITE MANGANESLFERE. (Fr.) >

(i) AN ARGILLACEOUS VARIETY (BROWN OR YELLOW CLAY-IRON-
STONE).

THONREICHER BRAUNEISENSTEIX, THOXEISENSTEIX. (Germ.)

(k) A SILICEOUS VARIETY, PASSING INTO BROWN FERRUGINOUS
QUARTZ.

KlESELREICHER BRAUNEISEXSTEIN. (Germ.)

HEMATITE BRXJNE SIUCEUSE (JASPOIDE). (Fr.)

All these different varieties (with the exception of bog-
ore, which only occurs on the surface of the ground) fre-
quently form subordinate beds or veins filling up clefts in
other rocks. Sometimes, but more rarely, they form local
massive and irregular accumulations especially at the con-
tact of two different rocks (contact formations).

Bog-ore is formed at the present day as a chemical
precipitate from water holding salts of iron in solution ;
this process is occasioned or accompanied by decomposition
of organic substances. If we suppose similar deposits of
brown hematite to have taken place in former periods,
and then to have been covered by other sedimentary
formations, we may easily conceive how in process of
time the thin compact layers of iron-ore which we find
imbedded in other strata would have arisen. Sometimes
brown hematite is evidently a product of transmutation
from spathic iron, or even magnetic iron-ore.

63. EED HEMATITE.

ROTHEISENSTEIN. (Germ.)
HEMATITE ROUGE. (Fr.)

A compact, earthy., or fibrous, or sometimes crystalline,
slaty, aggregate of red iron-ore ; colour red to black ;
streak red.
Spec. grav. 4 5.

Red hematite consists entirely or essentially of peroxide

IRONSTONE GROUP. 343

of iron (70 p. c. iron + 30 p. c. oxygen), sometimes inti-
mately combined with oxide of manganese, silica, or clay.
Its crystalline state is termed specular iron (Eisenglanz),
or micaceous iron (Eisenglimmer).

Varieties in Texture.

(a) COMMON RED HEMATITE. \

GEMEINER DICHTER ROTHEISENSTEIN. I ComDact

(Germ.)
HEMATITE ROUGE COMPACTS. (Fr.) >

(b) EARTHY HEMATITE, or RED IRON-MOULD.

ERDIGER ROTHEISENSTEIN, oder ROTHER EISENMULM. (Germ.)

FASRIGER ROTHEISENSTEIN, ROTHEL oder ROTHER GLASKOPF. (Germ.)
HEMATITE ROUGE FIBREUSE. (Fr.)

(d) OOLITIC HEMATITE, or FERRUGINOUS OOLITE.

OOLTTHISCHER ROTHEISENSTEIN, Oder ElSENOOLTTH. (Germ.)

HEMATITE ROUGE OOLITHIQUE. (Fr.)

(e) MICACEOUS IRON-SCHIST. 1 Consisting of a schis-

EISENGLIMMERSCHIEFKU. (Germ.) I tosc acTgregate of mica-

1 Kit OUGISTE ECAILLEUX OU MICACE. (Fr.) I ceous ij. on e g QU the

Gorgeleu in Marmaros, in Hungary, where it is imbedded
between strata of chlorite-schist and "limestone.

(f) SPECULAR IRON. 'j As rock, an aggregate of specular

i:isKxuLA>-zoEOTEix. (Germ.) I i r() n (iron-glance), usually combined
PER SPECULAIRE. (Fr.) J ^ ^ f^ Qf J^ ^^

rence as a rock ; e.g. on the Island of Elba, and at Picton-nob, r
in North America.

Varieties in Composition.

0) A VARIETY RICH IN MANGANESE r Whence its black

(BLACK HEMATITE). J colour ; sometimes

MANGANHEICHER ROTHEISENSTEIN (SCHWARZ- 1 called black hematite

UiiMATITK MANCrAVKSIF^RE (Fr} V OCll\VflJ*ZGlSCllSLClD )

(A) RED CLAY-IRONSTONE, RED OCHRE.

THONREICHER ROTHEISENSTEIN (THON- L An arefillaceous vanety.
(Germ.) J

OCRE ROUGE. (Fr.)

(i) SILICEOUS HEMATITE. \

KlESELREICIIER ROTHEISEN- I T j. J f

RBV. (Germ.) f Passing into red ferruginous quartz.

HEMATITE ROUGE SHJCEUSE
(JASPOtoE). (Fr.) I

(K) ITABIRITE. \ A compound of specular iron, micaceous

ITABIRIT. (Germ.) I iron, magnetic iron-ore, and some quartz ;

' .) granular, schistose, or compact. As acces-

sories, it contains talc, chlorite, actinolite, and native gold.

Found at Itabira, in Brazil (v. Eschwege, ' Brasilien ').

(7) TOPANHOACANGA (MooRSHEAD ROCK). This rock consists of
angular or somewhat rounded fragments of specular iron, mi-
caceous iron, and magnetic iron-ore, cemented together by a
ferruginous compound. Sometimes it also contains fragments
of quartz, itacolumite, clay-slate, &c., rarely also, grains of
native gold. At Itabira. Villa Rica, and Marianna, in Brazil,
it forms a crust on the surface of the ground of from four to
twelve feet thick.

344 MISCELLANEOUS DIVISION.

Most of the above-mentioned varieties of red hematite
occur in stratifications or veins, like the brown hematite ;
and they are also (though more rarely) found irregularly
massed between other rocks, usually of the transition or
crystalline schist formations never those of very recent
origin.

We may, perhaps, be justified in regarding the red
hematites as products of catogenic transmutation from
brown hematite ; yet it would appear that they have some-
times been formed from spathic iron under special circum-
stances. Certain it is from their anhydrous state we may
safely say that they are never original deposits from
aqueous solution, although they sometimes contain dis-
tinct fossils.

Specular iron, or iron-glance (as a mineral), is some-
times found in the clefts or fissures of volcanoes, where
it is a product of sublimation.

64. MAGNETIC IRONSTONE, MAGNETITE.

MAGNETEISENSTEIN. (Germ.}

MAGNETITE, FEE OXYDFLE, Hauy and Dufrenoy. (-FV.)

A granular or compact aggregate of magnetic iron-ore ;
black ; streak black ; metallic lustre ; influences the
magnetic needle.

Spec, grav 4-5 5-2.

Pure magnetic iron-ore consists of 69 to 75 per cent,
peroxide of iron, and 31 to 25 per cent, protoxide of iron
(therefore it contains about 72 per cent. iron). As a rock
it occurs mixed with specular iron, chlorite, chromic iron-
ore, titanic iron-ore, pyrites, chalcopyrite, quartz, horn-
blende, augite, garnet, or felspar, &c.

Varieties in Texture.
(a) GRANULAR.
(6) COMPACT.

minerals.

Varieties in Composition.

(d) PUKE MAGNETIC IRON-ORE.

(e) CHLORITIC MAGNETIC IRONSTONE.

(/) CHROMIC IRONSTONE, in which chromic iron predominates or

forms the only ingredient.
(g) GARNETIFEROUS IRONSTONE ; passing over into garnet rock.

IEONSTOXE GROUP. 345

(h) PYRITO-MAGNETIC IRONSTONE.

(i) CATAWBIRTTB is the name given by 0. Lieber to a rock found

by him in South Carolina, occurring there in great abundance.

It consists of a compound of talc and magnetic iron, intimately

blended together.

Magnetic ironstone forms subordinate beds or veins in
the crystalline schists. It is very extensively developed
at Schmiedefeld, in the Thuringian Forest, at Arendal in
Norway, at Danemora in Sweden, as a stratum in the
clay-slate at Berggieshiibel in Saxony. Chromic iron-
stone is usually associated with serpentine.

65. SPATHIC IRON; SIDERITE.

SPATHEISENSTEIN. (Germ.)

FER CARBONATE, Haily ; SIDEROSE, Seudant. (Fr.)

A granular or compact aggregate of spathic iron ; yel-
lowish-white, grey, or yellowish-brown; streak white;
effervesces with acid.

Spec. grav. . * . - . . f 37 3-9.

Spathic iron is carbonate of protoxide of iron (62 per cent.

protoxide of iron, and 38 carbonic acid) ; where it occurs

as a rock it is sometimes mixed with ankerite, calc-spar,

clay, specular iron, copper pyrites, &c., in small quantities.

Varieties in Texture.

(a) GRANULAR.

(b) VERY FINE-GRAINED.

IRONSTONE). I curring in the form of

DICHTER SPATHEISENSTEIN, SPHAROSIDERIT. j spheroidal concretions

<<*-> J orsentaria

SIDEROSE COMPACTS. (Fr.) U1 8e p l ' ttilt| "

(d) A SHALY VARIETY OF SPHEROSIDERITE, Or CARBONIFEROUS

IRONSTONE (BLACKBAND).

SCHIEFRIQER SPHAROSIDERIT, Oder KOHLENEI8ENSTEIN. (Germ.)

Varieties in Composition.

(e) ROHWAND (Germ.). A granular spathic ironstone, mixed with

much ankerite or calcspar.

(f) ARGILLACEOUS SPHEROSIDERITE, \

or CLAY IRONSTONE. I Also called clay carbonate

THONREICHER SPHAROSIDERIT, oder J O f i ron<

SEPTARIA AROILEUX. (Fr.) '

(g) CARBONIFEROUS IRONSTONE, BLACKBAND. \ Dark-coloured by

KHHLENEISKNOTEIN. (Germ.) v reason of admixture

J of coal j usually a
slaty spherosiderite or clay ironstone (d).

346 MISCELLANEOUS DIVISION.

This is the black "band of Scotland. < This natural admixture
of coaly matter confers on these rocks their special value, the
raw stone being readily calcined, in fact igniting and slagging
itself without the expensive admixture of coal, as is the case
with the ordinary clay ironstones and hematites.' Page.
Mushet makes a distinction between Blackband and Clayband,

Berg- u. Huttenm. Zeit. 1863, p. 295.

The crystalline varieties occur as subordinate strata,
veins or regular masses, in the crystalline schists or the
older sedimentary formations. The compact spherosi-
derites are most usually found with beds of coal. The
origin of these stratified beds and irregular masses of
spathic iron has not hitherto been satisfactorily explained,
since a carbonate of protoxide of iron could not be de-
posited under atmospheric influences. Probably the car-
bonic acid may have supervened at a later period. On
the other hand, the influence of the air will quickly change
spathic iron into brown hematite, and hence it is that
we find the surface of spherosiderite usually coated with
a brown crust, and many entire beds of brown hematite
appear to have been formed in this manner. A different
process of mutation may, perhaps, in some cases, have
produced red hematite and magnetic iron-ore.

Appendix.

66. DISILICATE OF PROTOXIDE OF IRON.

HALBKIESELSATJRES EISENOXYDTJL. {Germ.}
CHAMOISITE (Chamoison, Valais). (Fr.}

This compound sometimes occurs in the form of pea-iron-ore
contained in ferruginous clay, together with nodules of jasper,
as, for instance, at Kandern, on the western margin of the
Schwarzwald in Germany.
Deffner, zur Erklarung der Bohnerzgebilde, Stuttgart, 1859.

67. SILICEOUS SPHEROSIDERITE.

KIESELIGER SPHAROSIDERIT. (Germ.)
CARBONATE DE FER SILICETJX. (Fr.~)

This is a rock, described by Naumann, of a peculiar and fine
arenaceous character, consisting essentially of spherosiderite
(containing manganese) and siliceous earth or quartz-sand. It
forms a stratum (very rich in fossils) in the Nummulite forma-
tion of the Bavarian Alps between Traunstein and Sonthofen.
Schafthautl, in v. L. u. Br. Jahrbuch, 1846, p. 664.

347

CHAPTER V.

MINERALS AS ROCKS.

WE have in the first three chapters treated of those
rocks which, by reason of their great extent and volume,
may be regarded as the principal ingredients of the earth's
crust. We have seen that they are mostly of compound
character, although some few are essentially simple mine-
ral substances.

In this place we propose to enumerate those simple
minerals which appear as local accumulations in different
parts of the globe, forming essential members of particu-
lar formations, sometimes as stratified beds, sometimes as
veins or dykes, or irregular masses ; their volume being
just sufficient to entitle them to be considered* as members
of the rock family, taking an independent part in the
structure of the solid crust of the earth, although in
comparison with the other rock-formations which we have
hitherto treated, their bulk is for the most part very
inconsiderable.

A description of the formation, texture, &c., of these
mineral rocks will, in most cases, be unnecessary, as they
must be mineralogically determined and recognised. We
shall, therefore, in each case only give the name of the
mineral, adding some short remarks as to its exceptional
lithological character.

68. ICE.

Eis. (Germ.}
GLACE. (Fr.)

Sometimes compact, sometimes granular , fibrous or lami-
nated.

We need not here describe the properties of ice, but it
is not unimportant to consider the conditions under which
perpetual ice occurring in large masses forms part of the
solid crust of the earth.

The snow which falls in the polar regions, and in

348 MINERALS AS EOCKS.

mountain districts above the snow-line, only partially
thaws in summer ; the remainder accumulates year by
year. The successive falls of snow form a series of super-
jacent strata, the fleecy mass becomes consolidated by
pressure, and grains of ice are formed which unite into a
stratified granular ice ; this in the Alps is called firn or
neve. The masses of neve thus formed glide gradually
down over the mountain slopes and precipices into the
ravines and valleys. In the course of their downward
movement their stratification becomes much contorted
and otherwise disturbed ; they are, moreover, transformed
from distinctly granular neve into indistinctly granular
ice, or so-called glaciers.

The glacier continues to glide with a slow movement
down the valley. Its lower extremity, thus arrived in
warmer regions, thaws more rapidly and equalises the
accumulation of snow pressing down in fresh masses from
above. Hence the general extent and size of the glacier
usually remains much the same, although the individual
parts are constantly changing their position. By the mo-
tion of the glacier the traces of original stratification be-
come more and more contorted and effaced. The glacier,
moreover, becomes rent with frequent fissures (crevasses),
and in these the water arising from occasional thawing
accumulates and freezes during night or winter into new
ice, which may be distinguished from the genuine glacier
ice by its more compact structure.

All these phenomena are very instructive, and afford
many analogies to other rock formations and transfor-
mations. From loose accumulations, by means of pressure
and consolidation, masses are formed which become firmer
and more solid, and at last tolerably compact. Strata
are bent, pushed out of place, and overturned. The mass
is torn by cracks and fissures, which are filled by water
rendered fluid by heat. This freezes and constructs ice
veins in ice, somewhat like granite veins in granite, only
that these latter were probably filled from below, and
under a much higher temperature. By a kind of weather-
ing process even the compact venous ice in its turn be-
comes granular or separates into thin columnar parts, and
all these changes take place before our eyes in compara-
tively short spaces of time.

MINERALS AS ROCKS. 349

Very similar phenomena occur on a much larger scale
in the polar regions ; only they are less accessible, and
therefore more difficult of observation.

Besides these permanent masses of ice lying on the
surface of the earth, there occur in the northern plains of
Siberia extensive underground ice strata of great thick-
ness, sometimes interstratified with beds of sand, or they
contain sand mixed with the ice, and occasionally these
strata are covered with a surface layer of soil, which
during the short summer of Siberia supports vegetation.

69. OPAL.

OPAL. (Germ.)
OPALE. (Fr.)

As a rock, usually only forms very subordinate masses,
e.g. the so-called vitrite, which occurs at Meronitz, in
Bohemia, and contains numerous py ropes.

If, however, we reckon under the name of opal all the
various amorphous silicates enumerated by Naumann, we
find amongst them several very important rocks :

Varieties.

(a) SiLiCEOU8 SINTER, or SILICEOUS TUFF. "| Stratified incrustations
KIESKUSINTER Oder KiESELxcFF. (Germ.) i- and porous masses ;

J found as a deposit of

hot springs in Iceland and Kamtschatka, and, according to Hoch-
stetter, still more frequently in New Zealand. (Novarareise,
1862, vol. iii. p. 165.)

(6) SEMI-OPAL. \ Forms independent deposits, e. g. at Bilin,

HALBOPAL. (Germ.) I in Bohemia ; also irregular fillings of clefts
MB-OPALK. (Fr.) ) ^ ^^c rocks, e. g. at Hanau on the
Maine, in the dolerite.

HEXTUT. (Germ.) 1 and beds. It is found there in gypsuin and
rat (Fr.) { in marl ( Eocene ) . in Auvergne, in fresh-
water marl (Miocene).

(d) POLISHING SLATE, TRIPOLI. ] Consists of small shell-shaped

POLIRSCHIEFER, SAUGscHiEFER, KLEB- [ particles of silica of a peculiar
Tmp^ F ??;J Rn>PEU (<7m "' ) I form, only to be distinguished

' with the aid of the micro-
scope, so-called siliceous armour of Diatomacece or Infusoria ;
Nuiiinann therefore calls it Diatomeenpelit. Ehrenberg reckoned
that the polishing slate of Bilin m Bohemia contained in
a cubic inch 41,000 millions siliceous shells of Gattlonella.
Each individual is invisible to the naked eye, so that when
used for polishing metallic surfaces it produces only fine in-
visible scratches. Distinction is made in Bohemia between

350 MIXEKALS AS KOCKS.

tlie polirscliiefer (soft, friable, not adhering to the tongue) and

sangschiefer (adhering to the tongue and more solid, probably

because it is impregnated with opal substance). Both are

only known in very recent deposits; the older ones have

probably been transmuted into hornstein or lydian stone.

(Ehrenberg, Fossil Infusoria, Berlin, 1837, and Mikrogeologie.)

(e) KIESELGUHR. '| The same substance as polishing slate,

EJESELGUHR. (Germ.) [ b u t more dust-like, earthy, generally

^^^551 white or yellow. Found in beds many

* feet thick in the turf deposits at Soos,

near Franzensbad, Bohemia. The rock called RANDANITE by

Salvetat belongs to this species ; it consists of a white powder.

(v. L. u. Br. Jahrb. 1848, p. 124.)

70. QUARTZ.

QUARZ. (Germ.}
QUARTZ. (Fr.)

Occurs as an essential ingredient in many rocks, but it
also occurs as an independent rock in many varieties,
some of which are of considerable extent. We repeat the
mention in this place of several quartz rocks which we
have already noticed and included in other groups.

Varieties.

(a) ROCK CRYSTAL and AMETHYST. \ Sometimes the essential

BERGKRYSTALL und AMETHYST. (Germ.) I ingredient of veins and
CRYSTAL DE ROCHE et AMETHYSTE. (Fr.) I J^Lgg

(b) COMMON QUARTZ. ) Forms independent bed-veins or irre-

QUARTZ COMMUN. (Fr.) ) gular masses. Quartz -schist, see p.
246, ante ; Quartz -breccia, p. 305 ; Quartz-sandstones (siliceous
sandstone), p. 296. Millstone-quartz, freshwater-quartz, or
lemon-quartz, are porous varieties resembling chert, which,
. according to the fossils occasionally found in them, have been
deposited by fresh water, as, e. g., the celebrated millstones of
the Paris basin (Quartz meulier).

EISENKIESEL. (Germ.) [ transition states into iasper. Its

QUARTZ FERRUCHNEUX. (Fr.)) mode o f occurrence in nature is the
same as that of ordinary quartz.

(d) HORNSTONE, CHERT. ") Compact, forms independent beds,

HORNSTEIN; HORNFELS. (Germ.) [ veins, and masses. In Germanv
J thenameofHornfelsispivento

certain rocks, the product of transmutation of argillaceous
deposits, and found adjoining to plutonic rocks, to which they
probably owe the change they have undergone.

(e) LYDIAN STONE, or LYDITE, BLACK j Contains carbon which

CHERT. I gives it a greyish colour

KIESELSCHIEFER oder LYDIT. (Germ.) inclining to black

QUARTZ LYDIEN. (Fr.) ) ^ gtratified in thin

laminse, and hence of a laminated texture ; generally pene-
trated by numerous white veins of quartz j much rent by

MINERALS AS ROCKS. 351

angular fissures, sometimes containing lenticular concretions,
and also sometimes containing laminae of clay-slate. In
fissures it contains wavellite, calaite, variscite. It occurs with
tolerable frequency as a subordinate stratum in clay-slate,
slate-clay, or even mica-schist.
(/) JASPER. \ Compact, variegated, frequently striped or

JASPIS. (Germ.) I flamed (riband -i asper, agate-jasper). Much

JASPE. ( r.) j ^^ ^ een ca |i e( j jasper which properly belongs
to the feLsitic rocks, even to the felsitic tufis. It forms subordi-
nate layers imbedded in other rocks, and nodular concretions.
Jasper may be readily distinguished from petrosilex (which it
otherwise sometimes resembles) by the fusibility of the latter.
(g) AGATE. j The name given to certain combinations of

ACHAT. (Germ.) L chalcedony, carnelian, amethyst, and quartz.

AGATE. (Fr.) j There ^ mftny varieties : _i,anded agate,

fortification-agate, coral-agate, &c. It frequently forms veins or
fills cavities in other rocks.

(h) FLINT. \ Very similar to hornstone, but half amor-

FEUEROTETS. (Germ.) L phous, chiefly yellow, brown, grey, or
J black. Forms nodules, and then are fre-
quently disposed in layers ; very frequent, e. g. in chalk.

71. CORUNDUM.

KORUND oder SCHMIRGEL. (Germ.)
CORINDON. (Fr.)

Forms fine-grained subordinate layers imbedded in
crystalline schists, frequently accompanied by magnetic
iron-ore. Ochsenkopff, in the Erzgebirge ; Gumuchdagh,
in Asia Minor ; Naxos ; Chester, Massachusetts.

72. FLUOR-SPAR.

FLUSSSPATH. (Germ.')
FLUORINE, SPATHFLTJOR. (Fr.)

Frequently an essential ingredient in metalliferous
veins. A compact aggregate of fluor-spar forms a rock
at Rottleberode and Strassberg in the Hartz Mountains.

73. ROCK-SALT.

STEINSALZ. (Gtrm.)
SEL GEMME. (Fr.)

Chloride of sodium occurring as a rock is usually crys-
talline-granular, white, translucent or transparent,
easily soluble in water, and possesses a saline taste.

Spec, grav 2-12-2.

Pure chloride of sodium consists of 60 per cent, chlorine
to 40 per cent, sodium. In nature, however, it almost
always contains sulphate of lime, chloride of calcium,

352 MINERALS AS HOCKS.

chloride of magnesium, and other salts ; frequently ad-
mixtures of bitumen, clay, or boracite. Salt itself some-
times only forms an ingredient of some clays (Salzthon,
saliferous clay).

The colour of rock-salt is variable ; it is sometimes
yellow, red, bluish, or greenish, by reason of small ad-
mixtures of oxide of iron.

Varieties.

(a) GRANULAR ROCK-SALT.

KORNIGES STEINSALZ. (Germ.)

SEL GEMME GRANULAIRE. (Fr.)

(b) SPARRY ROCK-SALT.

BLATTRIGES STEINSALZ. (Germ.)

SEL GEMME LAMrNTAIRE (SPATHIQUE). (Fr.)

FASRIGES STEINSALZ. (Germ.)
SEL GEMME FIBREUX. (Fr.)

(d) KNISTERSALZ. (Germ.)

(e) GRUNSALZ, SPIZASALZ, SZYBIKER SALZ. (Germ.')

Reference.

The origin of the rock-salt of Strassfurt, near Magdeburg, has
been lately treated in a masterly manner by F. Bischof, Die
Steinsalzwerke zu Strassfurt, 1864.

74. TKONA.

TRONA. (Germ.)
SESQUI-CARBOKTATE DE SOUDE. (Fr.)

Occurs in Fezzan, in North Africa, forming a rock
which is even used for building purposes.

75. ALUNITE, or ALUM STONE.

ALTJNIT, oder ALAUNSTEIN. (Germ.)
ALTJNITE.

Forms a rock in the neighbourhood of Tolfa, near
Civita Vecchia. (See p. 185.)

76. BARYTES, or HEAVY SPAR.

BARYT, oder SCHWERSPATH. (Germ.)
BARYTINE, ou SPATH PESANT. (Fr.)

This mineral, which forms an essential part of many
metalliferous veins, was discovered by Yon Dechen, as
constituting a compact rock forming a bed some ten feet
in thickness, in the clay-slate of Meggen in the Lenne-
thal. Its colour was dark-grey.

MINERALS AS ROCKS. 353

Karsten's Archiv, 1845, vol. xix. p. 748 ; see also v. Hoinm-
gen, Verb, der naturh. Ver. d. pr. Rheinl. 1856, vol. xiii. p.
300 ; Sandberyer, geol. Verb. d. H. Nassau, p. 11 j and Zim-
mermann, Harzgebirge, 1834, voL i. p. 151.

77. BORACITE, or STASSFURTITE.

BORACIT, STASSFURTIT. (Germ.)
BORACITE, STASSFURTITE. (Fr.)

Forms irregular layers imbedded in the rock-salt of
Stasfurt.

Zeitschr. d. d. geol. Ges. 1856, voL viii. p. 156.

78. PHOSPHORITE.

PHOSPHORIT. (Germ.)

CHAUX PHOSPHATEE, APATITE. (Fr.)

Sometimes forms compact spheroidal masses, or sub-
ordinate layers, and even dykes or veins. Krageroe in
Norway.

79. CRYOLITE.

KRYOLITH. (Germ.)
CRYOLITE. (Fr.)

Forms considerable veins in the granitic gneiss at
Evigtok, in Greenland. (Journ. of Geol. Soc.)

80. ARAGONITE.

ARAGONIT. (Germ.)
ARAGONITE. (Fr.)

Many so-called calcareous sinters and peastones consist,
properly speaking, not of calcspar, but aragonite. (See
p. 281.)

81. ANKERITE.

ANKERIT. (Germ.)
ANKERITE. (Fr.)

This is most frequently found mixed in subordinate
quantities with spathic iron (vide p. 345, ante) ; and is
sometimes found separately as an independent rock.

82. MAGNESITE.

MAGNESIT. (Germ.)
MAGNKSIE CARBONATEE. (Fr.)

Frequently forms compact masses, but of subordinate
size and extent.

A A

3o4 MINERALS AS ROCKS.

83. DIALLOGITE, CARBONATE OF MANGA-

NESE.

MANGANSPATH. (Germ.')
DIALLOGITE. (Fr)

Frequently forms the principal constituent of metal-
liferous veins, e.g. at Kapnik, in Hungary.

84. MALACHITE.

MALACHIT. (Germ.)
MALACHITE. (Fr.)

Sometimes forms great clumps or masses in beds of
copper-ore in Russia.

85. TALC, or STEATITE.

TALK oder SPECKSTEIN. (Germ.)
TALC ou STEATITE. (Fr.)

Forms independent compact beds, e.g. at Gopfers-Griin,
in the Fichtelgebirge, where it forms a rock which can-
not be classed as a talc-schist.

86. MEERSCHAUM.

MEERSCHAUM. (Germ)

ECUME DE MEK, MAGNESITE. (Fr.)

Forms separate beds in Natolia, Negroponte, Crimea,
&c.

87. AGALMATOLITE, or FIGURE-STONE.

AGALMATOLITH oder BILDSTEIN. (Germ.)
AGALMATOLITHE. (Fr.)

The principal member of a dyke or vein at Dilln, near
Schemnitz. Also in China.

88. KAOLIN, or PORCELAIN CLAY.

KAOLIN oder POKZELLANERDE. (Germ.)
KAOLIN. (Fr.)

This is probably everywhere merely a product of the
decomposition of rocks very rich in felspar. Aue, in
Saxony, where it is a decomposed granite. In some
places a slight change has converted it into clay.

MINERALS AS ROCKS. 355

89. LITHOMARGE.

STEIN MARK. (Germ.)
LITHOMARGE. (Fr.)

Is found in very subordinate quantity between other
rocks.

90. ORTHOCLASE.

ORTHOKLAS. (Germ.)
ORTHOSE.

Sometimes forms independent dykes and accumulations,
e. g. in the granite at Carlsbad.

91. PYCNITE.

PYKNIT. (Germ.)
PYCNITE. (Fr.)

Forms concretions and dykes in the Zwitter rock, at
Altenberg, in Saxony.

92. EPIDOSITE, or PISTACITE ROCK.

EPIDOSIT oder PISTAZITFELS. (Germ.)
EPIDOSITE. (Fr.)

Epidote usually combined with some quartz. A sub-
ordinate formation in the Island of Elba.

93. LEPIDOLITE, or LITHIA-MICA.

LEPIDOLITH oder LITHIONGLIMMER. (Germ.)
LEPIDOLITE (MiCA A LITHINE). (Fr.)

Forms an independent rock of fine-grained and foliated
texture, e. g. at Rozena, in Moravia.

94. ROCK SOAP.

BERGSEIFE. (Germ.)
PIERRE DE SAVON. (Fr.)

Occurs in masses of subordinate extent, e. g. at Bilin,
in Bohemia.

95. BOLE.

BOL. (Germ.)
BOLE. (Fr.)

Occurs in masses of subordinate size in many limestone
rocks.

96. FULLERS' EARTH.

WALKERDE. (Germ.)
TERRE A FOTTLON. ^(Fr.)

AA 2

356 MINERALS AS ROCKS.

A substance resembling clay, somewhat greasy, but not
in the smallest degree plastic, but falling to pieces in
water, usually of yellowish green colour; is probably a
product of the decomposition of basic igneous rocks.
Cilli in Styria ; Nutfield, near Reigate.

97. FERREO-LITHOMARGE.

EISENSTEINMARK. (Germ.)
TERATOLITE. (Fr.)

Occurs in subordinate masses at Zwickau, in Saxony.

98. YELLOW EARTH, or MELINITE.

GELBERDE. (Germ.}

Occurs in small accumulations at Amberg, and other
places.

99. GALMEY, CARBONATE OF ZINC (in part).

GALMEI. (Germ.}
CALAMINE. (Fr.}

This name is indifferently applied to both the principal
zinc-ores : the silicate of zinc and the carbonate of zinc.
They occur together, and they form aggregates of con-
siderable size in the dolomite limestones of Tarnowitz,
Iserlohn, Aix-la-Chapelle, &c.

100. RHODONITE (in part), MANGANESE SPAR

(Bisilicate of Manganese).

KIESELMANGAN oder MANGANKIESEL. (Germ.}
RHODONITE (MANGANESE SILICATE). (Fr.}

Occurs (e. g.) in subordinate beds at Rosenau, in
Hungary; Cummington, Massachusetts, U.S.

101. LIEVRITE, or ILVAITE.

LIEVRIT. (Germ.}
ILVAITE. (Fr.}

Occurs (e.g.) in subordinate beds in the mica-schist of
the Island of Elba.

102. MANGANESE-ORES.

MANGANERZE. (Germ.}
MINERAIS DE MANGANESE. (Fr.}

MINERALS AS ROCKS. 357

One or more of these form veins of considerable thick-
ness, or beds of irregular shape, at Ilmenau, Ilfeld,
Kleinlinden, Warwickshire, &c.

103. RED ZINC-ORE.

ROTHZINKERZ. (Germ.)

MlNERAI ROUGE DE ZlNC (FRANKLnrTTE) . (Fr.)

Combined with Franklinite forms a bed of very con-
siderable thickness at Franklin, in New Jersey.

104. GALENA.

BLEIGLAKZ. (Germ.)
GALENE. (Fr.)

Usually associated with blende and sulphurets ; forms
veins of considerable extent and thickness, and occurs
otherwise in separate beds..

105. ANTIMONY-GLANCE.

ANTIMONGLANZ. (Germ.)
ANTIMOINE. (Fr.)

Forms veins of considerable thickness, e.g. at Magurka,
in Hungary.

106. ARSENICAL PYRITES.

ARSENKIES. (Germ.)
PYRITES ARSENICALES. (Fr.)

Usually associated with other sulphurets ; occurs in
separate formations of considerable thickness.

107. MARCASITE, or HYDROUS PYRITES.

MARKASIT oder WASSERKIES. (Germ.)
MARCASSITE. (Fr.)

Forms subordinate layers imbedded in other rocks, e. g.
in the Browncoal formation at Littmitz, in Bohemia.

108. PYRITES.

ScnWEFELKIES

PYRITES. (Fr
Usually associated with some chalcopyrite ; forms beds,

ScnWEFELKIES, PYRIT. (Germ.)
PYRITES. (Fr.)

358 MINERALS AS ROCKS.

veins, or irregular masses of considerable size, e.g. at
Domokos in Transylvania, Rio Tinto in Spain, Schmoll-
nitz in Hungary, Groslar at the Hartz, Fahlun in Sweden,
Agordo in the Alps.

109. CINNABAR.

ZINNOBER. (Germ.}
CINABRE.

Occurs but rarely in beds of considerable size or thick-
ness, e.g. at Almaden in Spain, Idria, California.

110. SULPHUR.

SCHWEFEL. (Germ.')

SOTTERE.

Forms rounded concretions and layers, in marl forma-
tions, e.g. at Radoboj in Croatia, Sicily, Perticara in
Umbria.

359

PART III.

OBSEEVATIONS ON THE PROCESSES OF
ROCK FORMATION IN NATURE.

THE NATURAL PROCESSES by which rocks have been
formed and are still in course of formation are partly in-
dicated in the foregoing pages. The following are those
known to us from actual observation :

1. CONSOLIDATION OF SUBSTANCES FROM A STATE
OF IGNEOUS FUSION BY PROCESS OF COOLING. This
is the process which all lavas undergo, and by which, pro-
bably, all igneous rocks have been formed. We must
assume that a first crust of the earth was likewise so
formed, but we cannot with certainty point to any of the
rocks remaining to us at the present day as representing
this primeval formation.

2. DEPOSIT OF SUBSTANCES FROM A STATE OF SUS-
PENSION IN WATER, AND OF SUBSTANCES FALLEN
THROUGH THE AIR. Thus are formed the sedimentary
rocks, under which general designation every kind of de-
posit is included.

They may be divided as follows :

(a) Mechanical deposits (actual sediments). To this
class belong deposits of mud, sand, and pebbles of every
kind, which by process of condensation and cementa-
tion produce argillaceous shale, clay-slate, limestone,
sandstone, conglomerate, and other similar rocks.

From the atmosphere are deposited particles of dust
and sand. These are frequently held in a state of
suspension for a considerable time, and transported by
the wind to great distances. Volcanoes vomit detached

360 PEOCESSES OF ROCK FORMATION:

substances or fine particles of dust, which with the aid
of water form volcanic tufas of various kinds.

(b) Chemical precipitates from aqueous solutions.
By chemical agency many kinds of deposit are formed.
For instance, calc-tuff, siliceous tuff, bog iron-ore, in-
crustations of salt, and many mineral formations in
clefts and cavities of rocks. The crystalline particles
of ice which fall from the air in the form of snow may
be considered as a chemical precipitate. Snow, as
we have seen, forms the neve and glaciers of high
mountain regions.

(c) Zoogenic deposits are products of animal agency.
Their massive accumulation is partly a mechanical pro-
cess. Thus we have rocks formed entirely of siliceous
infusoria, also the chalks, banks of shells, coral-reefs,
guano and coprolite beds, &c.

From the condensation of these rocks, hornstone,
lydian-stone, limestone, &c., may have resulted.

(d) Phytogenic deposits are such as consist chiefly of
vegetable substances ; these have either grown in situ,
or have been washed together. From these deposits, by
process of consolidation and subsequent conversion, the
different coal formations have resulted.

The above-mentioned processes of rock-formation are
those which admit of direct observation. There are others
at whose nature we only arrive by reasoning from the
results. Such are :

3. METAMORPHOSIS, OR TRANSMUTATION or PRE-
VIOUSLY EXISTING ROCKS. This is a process constantly
at work it has even begun to affect most of the dis-
tinctly sedimentary rocks. Few of these but have under-
gone some change. Thus the changes from argillaceous
mud to shale and then to clay-slate, from sand to sand-
stone, from loose stones to conglomerate, from calcareous
silt to limestone, from peat-moss to browncoal, or ordinary
black coal, &c., are, properly speaking, all cases of meta-
morphosis, although the rocks we have just named are not
usually termed metamorphic. That term is reserved
for the further stages of transmutation, where the change
is so complete that the first state of the rock can no longer
be easily or with certainty recognised by mere observa-

IGXEOUS ROCKS. 361

tion. The genuine metamorphic rocks are mica-schist,
gneiss, and the other crystalline schists, whose identity
with their originals can only be proved by deduction
from a variety of collateral circumstances.

The foregoing, are the only processes of rock-formation
known to us by observation, or which can be ascertained
by deduction from known facts. These processes are,
however, undoubted and indisputable, and our chief diffi-
culty consists in determining in each instance to which
mode of formation a rock owes its origin. Here many
difficulties and justifiable doubts present themselves. Let
us therefore attempt the application of these experiences
and their consequences to the several groups of rocks
which we have described in the preceding pages.

IGXEOUS EOCKS. ' (Eruptiv-Gesteine.)

No unprejudiced observer of geological phenomena can
doubt that those which we have classed and named as
igneous rocks were once in a fluid or viscous state, and
that whilst in that state they broke through pre-existing
rocks, overflowed them, and afterwards consolidated.
Ample proofs of these operations of nature are found in
the relation of the bedding of the igneous to those of their
surrounding rocks, the disturbances which they have fre-
quently (but not invariably) caused in the rocks broken
through, the fragments of the latter which they enclose,
and the veins or branches which they have thrust into
those adjoining. These general conditions established,
there still remain many special phenomena of formation
to be explained and accounted for, which we propose
briefly to consider in this place.

The great mutual resemblance of all igneous rocks
both chemically and mineralogically bespeaks a like pro-
cess of formation for all, i.e. they were all forced upwards
from the interior towards the surface of the earth in a

362 PKOCESSES OF EOCK FOKMATIOX :

molten state, like the lavas (which are evidently igneous
products) from the active volcanoes of the present ^day.
But although the composition and mode of occurrence of all
these rocks is, generally speaking, of a very uniform cha-
racter, yet special differences show that a great part of
those which are now exposed to our view did not originally
reach the surface and overflow at the time of their up-
heaval in the manner of genuine lavas, but became solid
at a considerable depth underground, where they still were
covered by or imbedded between other rocks ; and we
must assume that their present appearance on the face of
the earth is owing to subsequent destruction and wash-
ing away of the superincumbent rocks. Hence we dis-
tinguish between volcanic and plutonic rocks. The vol-
canic (as we have seen) are those which are known, or
supposed, to have consolidated at or near the surface ; and
the plutonic those which are presumed to have solidified
at a considerable depth in the interior of the earth.
There is no definite depth of measurement which we can
fix as a boundary between these two kinds of formation ;
the question of such depth must remain a subject for
entirely speculative estimate. Nor is the division of
rocks into volcanic and plutonic dependent on their mere
age, although in most cases it corresponds to a certain
extent in fact with their relative antiquity, because most
of the older volcanic formations have decayed away and
disappeared, whilst the newer plutonic formations have
not yet been laid bare, and are therefore inaccessible to
our view. The deeper in the earth that any rock was
formed, the longer would be (cceteris paribus) the time
necessary for its denudation ; and therefore the older will
it be when we meet with it at the surface.

Recent chemical analysis (as we have already had oc-
casion to remark) shows a great uniformity of elementary
composition in all classes of igneous rocks. We have
seen that they all consist of silica, alumina, peroxide
or protoxide of iron, lime, magnesia, potash, and soda,
and frequently some water. Their other ingredients
are but subordinate in quantity, and can only be re-
garded as accessory ; such are protoxide of manganese,
titanic acid, carbonic acid, phosphoric acid, sulphuric

IGNEOUS KOCKS. 363

acid, oxide of chromium, oxide of copper, baryta, lithia,
sulphur, &c.

The quantitative proportions of the essential elements
vary considerably in different rocks, but this variation is
almost as great between different kinds of the same rock
as between the different rocks themselves ; and no igneous
rock is of so invariable or marked a chemical character as
to be distinguishable from the rest by it alone.

Taking the whole range of the igneous rocks, the
average values of their chemical constituents may be
stated somewhat as follows :

Extreme actual values. Ideal average.

45
15
10
6
5
4
4
2

Where the extreme values, as above given, are found
to be exceeded on the one side or the other, the excess or
deficiency appears invariably to have been the result of
change, decomposition, or some similar process subsequent
to the formation of the rock, which, therefore, is no
longer in its original state.

We have already indicated the division of the igneous
rocks, in respect of their chemical composition, into two
principal groups.

1. Poor in silica, or basic.

2. Rich in silica, or acidic igneous rocks.

The distinction between these two groups is deserving
of considerable attention, for they also differ to some
extent both mineralogically and geologically, although
they cannot be very rigidly separated from each other ;
and certain rocks of each group vary so greatly in their
composition as actually to graduate into the opposite
group.

The following proportions may be stated as an approxi-
mate average of the analysis for the two groups :

Silica
Alumina
Peroxide a
Liine
Magnesia
Potash
Soda
Water

mdP

rotox

de oi

Iron

5080
1025
125
015
012
010
7
5

364 PROCESSES OF ROCK FORMATION :

Basic. Acidic

Silica . . * '" ~. 4560 55-80

Alumina 1025 1015

Iron (Peroxide or Protoxide) . 1 25 1 15

Lime J , .'. ! . . . ' , . 115 08

Magnesia 112 4

Potash 19 111

Soda 17 28

Water 04 06

These two groups nearly correspond with the pyroxenic
and trachytic groups of Bunsen, for which he calculated
certain ideal or normal average values of their elementary
constituents.* (See Poggend. Ann. 1851, vol. Ixxxiii.)

Without, therefore," being able to fix any very precise
standard, the distinguishing feature of the basic rocks is,
that they contain less silica, more alumina, iron, lime, and
magnesia, and less alkali than the acidic rocks. Within
the limits of each group we find no constant differences
of chemical composition between the several species.
These only differ in their mineral development, their
texture, or the mode and accidents of their occurrence in
nature.

We may, therefore, say in general terms that all
igneous rocks consist of one or other of two compounds
normally differing in the proportions of their elementary
constituents, but that several intermediate gradations
exist between the two extremes. Each of these two
compounds has produced many different species and mo-
difications of rock which have received different names.
The differences are partly those of texture, partly of
mineral composition. The first may in most cases be very
simply accounted for by the particular circumstances of

* Bunsen's values of the different elements were as follows :

Pyroxenic. Trachytic.

Silica 48-47 76-67

Alumina and Protoxide of Iron 30-16 14-23

Lime ; . . . . 11-87 1-44

Magnesia 6-89 0-28

Soda ... . . . 1-96 3-20

Potash 0-65 4-18

100-00 100-00

IGNEOUS ROCKS. 365

cooling. The quicker the cooling process, the more com-
pact or even vitreous the product would be; and the
slower the process, the more crystalline and coarse-
grained would the rock become. Inequality in the crys-
tallising power of the different ingredients would give a
porphyritic texture ; parallel arrangement of certain of
the ingredients would give a slaty or schistose texture ;
development of gases during the cooling would give a
vesicular or slag-like texture.

The differences of mineral composition are not great.
In most cases the elementary substances are the same ;
and the differences of proportion in which they are com-
bined are so small as to appear unimportant. We are
unable satisfactorily to explain in any particular case why,
with differences of composition so trifling, one particular
species of felspar, of hornblende or pyroxene, or of mica
was produced rather than another, or why, under ap-
parently similar conditions in another rock, other mi-
nerals, such as nepheline, leucite, talc, chlorite, &c., were
formed in their stead. A part only of these differences
can be traced to have any distinct relation to the quan-
titative proportions of the chemical composition of the
whole rock. Other differences consist in the presence of
various accessory minerals. These we may presume to
represent a surplus or residuum of certain elementary
substances remaining uncombined after the crystallisation
of the essential mineral ingredients. Many accessory
minerals are, however, evidently the result of later pro-
cesses of transmutation.

If we disregard the specific but minor differences be-
tween those similar minerals, which, to a certain extent,
occur as substitutes for each other in rocks, we find a
certain correspondence in the mineralogical with the che-
mical phenomena, and that, speaking generally, there are
two principal kinds of rock essentially differing from each
other in the aggregate of their mineral composition,
if only in their normal states of development one a
basic, and the other an acidic compound. These are again
subdivided, according to their texture and recognisable
mineral differences, into rocks of several species, as indi-
cated in the following tabular statement.

PROCESSES OF KOCK FORMATION:

Granular

Porphyritic

Compact

Vitreous, vesicu-
lar, or amygda-
loidal

Slaty-schistose
(chiefly meta-
morphic)

^ /Granite
"1$ Syenitic-
^ j granite
.0 ] Protogine
^ Trachyte
^ V(Greisen)

Granitic-
porphyry
Quartz-
porphyry
Trachyte-
porphyry

Felsite rock
Petrosilex

Pitchstone
Pearlstone
Obsidian
Pumice-stone

Granulite
Gneiss
Protogine-
gneiss
Felsite-schist
(Mica-schist)

4
f.

^Syenite
Diorite
Diabase
Timacite
Dolerite
Nepheline-
dolerite
Gabbro
Miascite
^Mica-trap

Hornblende-
porphyry
Mica-por-
phyry
Porphyrite
Aphanite-
porphyry
Melaphyre

Melaphyre
Aphanite
Basalt

Vesicular
rocks and
amygdaloids

Hornblende-
schists
Chlorite-schist
Talcose schist

As already stated, the mineral differences in the ig-
neous rocks do not appear to have been all original,
but to have been partly produced at a later period by
process of transmutation. In individual cases this has
been very well shown to be the fact by Bischof and
Rose, although both of those distinguished men may, per-
haps, have gone too far in their hypotheses on this sub-
ject. The extent to which such transmutations have
taken place is not yet established by proof, and we
may say generally that it is impossible to be too cau-
tious in admitting the process of transmutation as a suffi-
cient explanation of differences between rocks, unless
we are willing to be content with mere convenient hypo-
theses.

We have already observed that the causes are not yet
satisfactorily ascertained why, from compounds chemically
very similar, in one rock orthoclase has resulted, in others
sanidine, oligoclase, labradorite, anorthite, &c. ; in one
rock a hornblende, in another a pyroxene.

The exact causes of these phenomena can never be
ascertained with certainty. One cause, however, of dif-
ferent forms of mineral development may be well con-
ceived, viz. the different depths at which cooling and
solidification have taken place in rock masses. It cannot

IGXEOUS ROCKS. 367

be doubted that the conditions under which substances
have combined to form minerals were very different at a
depth of 10,000 feet from those which prevailed at a
depth of 10 or 100 feet only from the surface. In the
former case the masses have been subjected to far higher
pressure were shut out from the atmosphere they were
probably exposed in some degree to the action of water,
but their cooling must, in masses of equal bulk, have
been on the average a much slower process than would
have obtained near the surface. Again, not only the
depth of the formation, but the geological period of the
earth's development may have had considerable influence
in determining the character of minerals. For if the
theory is correct that the earth has cooled into a solid
from a previous molten state, its average temperature in
former periods, even at the surface, must have been
higher, and the atmosphere more dense and heavy than
at present. Each cooling process under such circum-
stances would be slower, and would take place under a
different degree of pressure than now. Thus we have
one recognised general cause for the differences we ob-
serve ; but the definite proof of what its precise effects
have been under different circumstances is wanting.

The cause for a division of the igneous rocks into those
poor in silica and rich in silica remains a great problem
for solution. A priori we should expect to find all
igneous rocks of the same composition. Bunsen's theory
of the existence of two separate volcanic furnaces in the
interior of the earth is a mere hypothesis, which, no
doubt, might, if it were true, suffice to explain the exist-
ing differences, but which in itself is very improbable.
Such furnaces, if they existed at all, must have been in
existence through all geological time ; in almost every
part of the globe they must have been placed side by
side or one above the other, and yet have remained dis-
tinct and unmixed. No circumstance, unless it be the
very difference which we are endeavouring to explain,
speaks for such an assumption. Even if the cooling and
solidifying of the fluid mass of the globe should have pro-
ceeded contemporaneously equally from the centre and
surface towards a middle plane, as Bunsen supposes, so
that at last only an intermediate stratum of fluid matter

368 PROCESSES OF ROCK FORMATION :

will remain between the two, the existence of separate
basic and acidic basins of lava will not by this assume
greater probability. For the present we must confess
that the cause of the differences between these two chief
groups of igneous rocks has not yet been satisfactorily
explained.

It has been very ingeniously suggested that a cause
might be sought in the different specific gravity of the
several rock masses, starting with the assumption that in
the former molten state of the earth the ingredients must
have arranged themselves in some measure according to
their specific gravity ; so that the heaviest substances
would be accumulated towards the centre, and the lighter
towards the surface. If the cooling process began with
the outside of the globe proceeding inwards, then it
follows that the specifically lighter bodies would first
attain the solid state, and these we actually find to be
richest in silica ; and that the heavier bodies, which are
at the same time the most basic, would only cool at a
later period. This law, it was considered, must prevail
alike in an incrustation formed under quiet circum-
stances, as in the case of eruptive rocks necessarily emer-
ging from a great and ever increasing depth ; so that the
oldest would be the lightest and most acidic ; the recent
the heaviest and most basic. This theory, which Petz-
bold (in his Geologie, 1840) pushed to the utmost ex-
treme, i. e. to the formation of mineral veins, has been
lately attempted to be applied in a narrower sense by
Von Eichthofen (Greol. Beschreib. von Sud-Tyrol, 1861,
p. 308). It evidently has a great appearance of theo-
retical probability in its favour. But when we come to
test this theory by comparison with ascertained facts, we
at once find it untenable, at least in part, and undoubtedly
altogether insufficient satisfactorily to explain those facts.
Every geological age has produced acidic as well as
basic, specifically light and specifically heavy, igneous
rocks. Where syenite and granite occur together, it is
even most usually the case that the basic syenite is older
than the acidic granite. The basic porphyries in the
Thuringian Forest and the Erzgebirge are on the
average older than the acidic quartz-porphyries which
belong to the same great period. The trachyte-por-

IGNEOUS ROCKS. 369

phyries belong to the most acidic and yet frequently to
the most recent eruptive rocks. According to von
Richthofen's own investigations, they are, on an average,
of more recent formation than the trachytes, which con-
tain less silica and are also somewhat heavier. Therefore,
von Richthofen himself, to support his theory, was com-
pelled to have recourse to various hypotheses, such as a
second fusion and new eruption of old igneous rocks, &c.,
which in themselves are neither probable nor sufficient to
solve all the difficulties of the case. We have yet to seek
the true solution of many important problems relating to
this subject. Nevertheless, we are not of opinion that the
theory of an arrangement of substances according to their
specific gravity should be disregarded as entirely un-
worthy of serious attention. Specific gravity may, and
probably has had, a certain influence in the first arrange-
ment of rock masses ; and if we are unable now to trace
a consistent arrangement deducible from the laws of
specific gravity, it may be only because those traces have
to a great extent been subsequently effaced by other cir-
cumstances which we have not yet discovered. A primary
crust formed by cooling and the first sedimentary deposits,
resulting from the decay of that first crust, may well have
been pre-eminently rich in silica ; more especially if at
the time of those sedimentary deposits animal life had not
begun to act on the calcareous waters, and so cause a
redeposit of the dissolved lime in large masses. If this
primary portion of the earth's crust should at a later date
have been subjected to a second process of fusion under
high pressure, at a considerable depth, it may have
become partially eruptive, and have produced recent
rocks very rich in silica and of very uniform chemical
composition. We may, in fact, reasoning from analogy
to the meteoric stones, which represent to us the small
planetary bodies of our solar system, believe the aggre-
gate of the earth's mass to be far more strongly basic
than that part of it which is open to our observation.

Taking into account composition, on the one hand, and
geological character, on the other, we come to distinguish
four great groups of igneous rocks, which groups are,
however, not divided from each other by exact bounda-
ries. Each may be characterised by some typical rock ;

B B

370 PKOCESSES OF ROCK FORMATION :

and each may be also connected with the other groups by
means of other rocks of intermediate character. We may
represent these groups somewhat as follows :

BASIC -f ^ mmc : Basalt ") Diabase, Porphyrite,

' \ Plutonic : Diorite J Melaphyre

or :

ACIDIC [ ^kamc : Trachyte 1 Trachyte-porphyry
' I Plutonic : Granite J Quartz-porphyry

Vn , .,. {Basic : Basalt \Trachydolerite. Andesite,
C ' \ Acidic : Trachyte JPorphyrite

-r^ {Basic : Diorite | .,

PLUTONIC . . Senite

A ^. Q . Granite

| .,
j Syenit

We must not omit to remark that some considerations
entitled to attention have been started against the igneous
character of certain of the rocks so named, and chiefly
those which contain quartz.

Granite is the principal representative of these rocks.
In the case of this rock, so universally spread over the
surface of the globe, it has been objected that, look-
ing to the mode in which its essential ingredients, fel-
spar, quartz, and mica are joined together, and fitted
one into the other, those minerals could not have been
formed in the order of their respective degrees of rapidity
of solidification from a state of fusion, i. e. first the
quartz, then the felspar, and last the mica ; but, on the
contrary, that it very often appears distinctly that the
quartz, which is the most difficult of fusion, has been
formed the last. It has been further objected that in
granite, as well as in many other, even in certain basic
igneous rocks, there sometimes occur accessory minerals
whose formation by igneous means can scarcely be con-
ceived as possible, or at least is contradicted by all
experience. For instance, pyrites, apatite, pyrochlore,
carbonate of lime, carbonate of magnesia, protocarbonate
of iron, &c. These are found side by side with silicates,
and yet without forming chemical combinations with the
latter. Finally, it has been objected that many so-called
igneous rocks contain some water, and according to the
analyses of Delesse, even small quantities of nitrogen.
(Ann. des. Mines, 1860, vol. xviii.)

Now, as regards the first objection the solidification of

IGNEOUS ROCKS. 371

the quartz subsequently to the felspar Durocher has long
since shown (Gompt. rend. 1845, p. 1275), that in fusing
the compact rock petrosilex, whose composition is often
precisely the same as that of granite, the quartz which it
contains being associated with the other ingredients of
the rock, is quite as readily fusible as felspar alone ; and
hence we may conclude that upon the cooling of such a
mass the quartz would not necessarily separate itself from
the rest of the compound by solidifying sooner than the
felspar. If this be so, in the case of a granitic mass it
might depend on some circumstance, which for want of a
better term we may call accident, whether the quartz
or the felspar should first happen to complete the pro-
cess of its crystallisation, and whichever of those two
minerals first crystallised would necessarily determine
the form of the other. Now the felspar in granite ap-
pears to have been the first to crystallise, and has deter-
mined the form of the quartz in many cases. Bunsen has
lately thrown much light on this question (vide Zeitsch. d.
geol. Ges. 1861, p. 61); he has shown that the melting
and solidifying points of a mineral, when taken singly, by
no means determine those of an intimate compound or
alloy of such mineral with other mineral or minerals. In
a letter to Streng, which appeared in the Berggeist
(1862, p. 1), Bunsen, in illustration of the same law,
adduces instances of aqueous solutions, where heat is ne-
cessary to the solution. The so-called PattinsorCs pro-
cess is the result of a similar experience. It is found that
pure lead crystallises sooner than lead containing a pro-
portion of silver ; and accordingly when the liquid mass
of mixed lead and silver is subjected to a process of slow
cooling, the pure lead congeals first, leaving the richer
metal still in a fluid state (termed ( mother water'). More-
over, high pressure and water (chemically combined) may
have exercised many important modifying influences upon
the process of the formation of the granitic rocks.

The second suggestion referring to the presence of cer-
tain minerals as accessory ingredients in so-called igneous
rocks which appear incompatible with their igneous origin,
loses much of its force from our likewise finding some of
the same minerals in genuine lavas, whose origin is un-
doubted. Moreover, those minerals or substances may

BB 2

372 PEOCESSES OF ROCK FORMATION :

not have been actually present in the rocks in question at
the period of their first formation, but have originated in
them at a later date. As to the water contained in rocks,
Scheerer has clearly proved that water forms a basic in-
gredient of many minerals (e.g. many kinds of mica),
entering into combination with silica and other acids in
precisely the same way as any other basic oxide. Dau-
bree has established the same fact synthetically, showing
that under great pressure at a high degree of temperature,
water may be made chemically to combine with mineral
matter. Whether the very small quantity of nitrogen
contained in many igneous rocks was there originally, or
whether it only insinuated itself into them at a later
period, may, for the present, remain an open question ; all
minor difficulties like this will probably find a satis-
factory solution in time. On the other hand, as regards
the carbonates of lime, magnesia, and iron contained in
igneous rocks, they appear to be invariably the result of
change or transmutation subsequent to the formation of
the rock. Hence we never find them in very recent lavas,
but only in those igneous rocks which have been long
and continuously exposed to the action of chemical in-
fluences, calculated to bring forth those minerals, and
therefore we find them more frequently in the plutonic
than the volcanic rocks. Pyrites, magnetic pyrites, chlo-
rite, and talc, all likewise appear to have been the result
of such transmutations, even if we cannot as yet satis-
factorily so explain every single case of the occurrence
of a particular mineral. These considerations prevent us
from attaching much weight to the objections raised to
the igneous origin of granite an origin which on other
grounds appears so conclusively established.

The differences between the volanic and plutonic rocks
of both principal groups, the basic and acidic (although
smaller and more filled up by transition states than
those between the two groups themselves), deserve a
full share of our attention, and require some explana-
tion. We have already more than once adverted to one
general cause of difference, namely, the unequal condi-
tions, under which the cooling and solidification first took
place, whether under simple or multiplied atmospheric
pressure ; and whether on the surface of the globe, or in
a closed space, where water probably had access.

IGNEOUS ROCKS.

373

Besides these original causes of difference, there are also
the many changes which appear to have taken place in
the state as well as composition of all rocks, subsequently
to their first formation, chiefly no doubt under the in-
fluence of water and gas penetrating and permeating
them.

In the present state of science it is impossible every-
where separately to specify and define the results of all
these different causes, yet we will attempt by contrasting
the characteristic attributes of the two principal groups
to present some general views applicable to the subject.

The original differences may shortly be stated as fol-
lows :

In Volcanic Rocks.

Prevalent compact, porphy-
ritic, vesicular, or vitreous
states. Seldom or never slaty
or schistose texture.

Small content of water.

Seldom crystallised quartz.

Frequent tufa formations.

In Plutonic Hocks.

Prevalent crystalline -granular and
porphyritic, sometimes also schistose
or slaty texture; seldom vitreous or
vesicular.

Greater content of water.

More frequently crystals of quartz.

Seldom tufa formations.

The differences occasioned by gradual metamorphosis
are as follows :

In Volcanic Rocks. In Plutonic Rocks.

There is little or no change. The formation of amygdaloids, by

the filling up of previously existing
vesicular cavities with newly-formed
minerals.

The new formation or transforma-
tion of certain minerals in the in-
terior of the mass, e.g. pyrites, car-
bonates, zeolites, apatite, chlorite,
talc, serpentine, &c. The absorption
of more water. Decomposed wacke-
nitic states; possibly even many
formations of quartz.

To sum up these observations : It appears that in the
present state of science we cannot but regard all the so-
called igneous rocks as parts of the earth's interior mass,
thrust out whilst in a state of fusion, without being able
as yet satisfactorily to explain their division into the two

374 PROCESSES OF KOCK FORMATION :

principal groups of acidic and basic composition respec-
tively, the minor differences inside of these groups being
capable of explanation by the different circumstances
under which the several rocks attained the solid state or
by subsequent process of their transmutation.

In addition to the works cited in the text we will here
only notice the following :

Deksse, on the origin of igneous rocks, in Compt. rend. 1859,
vol. xlviii. p. 955 ; v. L. u. Br. Jahrb. 1859, p. 459 ; and Ann.
des Mines, 1858, vol. xv. p. 459. Delesse distinguishes between
Igneous rocks (trachyte, dolerite), Pseudo-Igneous rocks
(trap), and Non-Igneous rocks (granite, diorite, &c.). If
we wish for extreme precision of nomenclature, the term
Igneous is altogether inappropriate, even for the volcanic
rocks, which have but consolidated from a state of liquid
fusion, without any fire or burning in the ordinary accepta-
tion of the word fire. Hence in Germany the Igneous rocks
are termed Eruptive rocks. One name is as good as another
for practical purposes, if we do not seek to attach theory
too closely to nomenclature.

Daubree, Sur le Metamorphisme et sur la Formation des Roches
Cristallines, 1860.

Scheerer, iiber den Astrophyllit und sein Verhaltniss zu Augit
und Glimmer und Zirconsyenit nebst Bemerkungen iiber
die plutonische Entstehung solcher Gebilde, 1864.

See also Cotta's Geologische Fragen, 1858. The argument
against the igneous origin of granite which has been built on
the score of the specific gravity of the quartz falls to the
ground if we believe that it became solid under high pressure.

SEDIMENTARY ROCKS.

The general character of the processes by which these
rocks were formed is well known and evident. They are
deposits of fallen substances, chiefly precipitated from
water a small part from the atmosphere. This, their
origin, is proved in a variety of ways, by their composi-
tion, their stratification and bedding, and the fossils which
they enclose.

A few words as to their composition may not be out of
place here.

If the views now prevalent respecting the earth's history-
are correct, the igneous rocks must be regarded as the

SEDIMENTARY ROCKS. 375

most original, or rather the only original formations.
Should it appear that any part of the first crust produced
by the original cooling of the earth's surface remains un-
disturbed at the present day, it will properly belong to
the igneous rocks, although not like the other igneous
rocks, eruptive. If we take all the igneous rocks together,
we have products of the eruptions of all geological pe-
riods. To these products we must, therefore, chiefly look
for information as to the nature of the substances con-
tained in the interior earth's mass. They may represent
a part only of that mass, but they constitute our only
evidence on the subject. The nucleus of the earth may
possibly be differently composed, but we possess no means
of investigating it.

In the aggregate composition of the sedimentary rocks,
which we assume to be but the product of decomposition,
re-deposition, and transmutation of the original and first
consolidated igneous rocks, we should expect to find the
same ingredients as in the igneous rocks, and in somewhat
similar proportions. Therefore we should look for silica
as the predominant ingredient, and alumina, oxides of
iron, lime, magnesia, potash, and soda in smaller quanti-
ties. We do, indeed, find these to constitute the sub-
stance of the stratified rocks (although not grouped in
the same manner as in the igneous rocks). We likewise
find other ingredients such as compounds of carbon, sul-
phur, and chlorine ; but these we infer have been derived
from the atmosphere or from water. It is doubtless very
difficult to form a sound opinion, whether in point of fact,
the quantitative proportions of the ingredients we have
first named are in the aggregate about the same in the
sedimentary as in the igneous rocks, since the combina-
tions are for the most part very different in the two classes.
In the sedimentary rocks the lime and magnesia have
vmited with carbonic acid to form the limestones and
dolomites, or with sulphuric acid to form gypsum and
anhydrite ; silica has produced quartzite rocks and the
sandstones ; alumina has combined with silica to form
the argillaceous rocks; oxides of iron, the ironstones
(iron is also much disseminated in other rocks); potash
and soda have become very much distributed amongst
many kinds of sedimentary rock ; soda, again, has united

376 PKOCESSES OF EOCK FORMATION :

with muriatic acid to form rock-salt ; carbon (concentrated
by process of vegetation) has formed coal-beds.

At a cursory glance it might appear as if the sedi-
mentary rocks in the aggregate contained more lime and
less potash than the igneous. We must, however, re-
member that some lime is contained in almost all igneous
rocks (especially the basic rocks), but by no means in all
sedimentary rocks ; again, that the sulphuric acid and
water make up a very considerable part of the bulk of
the limestones, dolomites, and gypsums ; which bulk we
may moreover easily be led to overrate as they are apt
to stand out very conspicuously and prominently amongst
the other sedimentary rocks in separate and excep-
tionally compact masses. Taking all these circumstances
into account we should probably find that the proportion
of lime in the aggregate of the stratified rocks does not
essentially differ from that in the aggregate of the igneous
rocks. As regards the potash we must recollect that its
quantity in the igneous rocks only reaches about 4 per
cent, as an approximate average, that the greater part of
the sedimentary rocks contain some potash, and several
a very considerable quantity. Great quantities of soda
have been converted into rock-salt. We have, therefore,
no sufficient reason to doubt that the aggregate ingre-
dients of the igneous and the sedimentary rocks are
equally balanced.

In the case of all sandstones, stratified conglomerates,
tuff formations, compact and slaty argillaceous rocks, as
well as the greater part of the marls, limestones, dolo-
mites, and coals, their sedimentary origin is so appa-
rent that nobody will doubt it. The matter is less clear
in the case of many granular limestones and dolomites,
also in that of the massive accumulations of rock-salt and
gypsum, although the sedimentary origin of these latter
is now generally admitted. It is most difficult to dis-
tinguish the sedimentary from the igneous rocks in those
cases where the two are found interlying each other in
parallel beds as sometimes happens, the igneous perhaps
indistinctly composite or even somewhat decomposed.

Whilst we thus find no difficulty in pronouncing on the
origin of the sedimentary rocks in general, it is somewhat
difficult to determine what rocks we should reckon as

SEDIMENTARY ROCKS. 377

sedimentary, and in what cases we should apply the terra
* metamorphic.'

The expression ' metamorphic ' will best serve a useful
purpose of distinction if it be reserved for cases where a
rock originally sedimentary (according to our previous
definition) is so essentially changed in its mineral cha-
racter as not to be capable of recognition without the
evidence of collateral circumstances to identify it with the
original formation. From the nature of the case, how-
ever, no distinct division between the sedimentary and the
metamorphic rocks is possible ; on the contrary, gradual
transitions take place from one to the other, and the ex-
tremes alone are distinctly different in their character.

There remains much for investigation as to the parti-
cular circumstances under which the several kinds of sedi-
mentary rock came to be deposited.

\Ve cannot lay down any general law applicable to all
sedimentary rocks as to the conditions under which their
first deposit took place. The case of each rock has to be
separately considered with reference to its bedding, and
the organic remains which it contains. The most that we
can say as a general proposition is, that many of these
rocks have been deposited by the sea some on the coasts,
some at a great distance from the shore ; others have been
deposited in freshwater lakes by means of rivers or springs.
The greater part consist of matter washed together by
floods ; some consist of the ejectamenta of volcanoes ;
some are crystalline precipitates, and some are the result
of processes of animal and vegetable life.

Nor can we in general terms describe the mechanical
forces which have acted on the materials of the sedi-
mentary rocks to fit them for union, the mode of that
union, the separation or combination of the chemical
ingredients, the nature of the substances which have been
introduced or become changed subsequently to the first
deposit, the alterations of level which have taken place
in the beds of those rocks by depression or upheaval,
&c. All these are of great moment to be determined,
but they can only be subjects of separate consideration in
each individual case.

The oldest rocks which are capable of being recognised
at the present day as distinctly sedimentary, are those of

378 PROCESSES OF ROCK FORMATION I

the transition period. Now as these rocks still contain a
considerable number and variety of organic remains, it is
reasonable to conclude that there have been many of yet
more ancient date, for, according to the igneous theory of
the earth's structure there must necessarily have existed
a long period of time in which deposits took place before
any organic remains existed. These oldest deposits would
be the lowest sedimentary formations, and would contain
few or no fossil remains. It is probable that they have
been changed into, and now form the principal bulk of
the metamorphic schists. If we would speculate on their
former probable structure, we should expect their compo-
sition to have been very uniform, because at the time of
their deposit there were fewer causes for difference in
rock formation than in later periods ; many of such
causes having arisen subsequently, such for instance as
organic life, the origin of many calcareous, and all the
carboniferous strata. Reasoning backwards, if we believe
the crystalline schists to have chiefly sprung from the
oldest sedimentary rocks, we may thus account for their
very rarely enclosing calcareous or carboniferous beds
(limestone and graphite). That the composition of these
crystalline schists should much resemble that of the first
igneous rocks, would seem to be but a natural consequence
of their transmutation from the earliest sedimentary rocks,
which themselves were the products of the disintegration
of those first igneous rocks. But these speculations should
be indulged in with caution, as they may easily lead us
too far into the regions of unfounded hypothesis.

METAMORPHIC CRYSTALLINE SCHISTS.

Notwithstanding what we have had occasion to remark
in describing the sedimentary rocks, the true interpreta-
tion of the crystalline schists remains one of the most
difficult problems for the geologist, since the process of
their formation can only be subject of theory, and not of
direct observation.

Various theories as to the nature of their origin have
been advanced. They have .been taken for the original
deposits of a so-called antediluvian age ; for the first cooled
igneous products of the earth ; a part for rocks of eruptive

METAMORPHIC SCHISTS. 379

character ; and finally for sedimentary rocks very greatly
changed or transmuted. These different views have been
put forward at different times, have been more or less
accepted, but all except the last have been very generally
abandoned.

Nobody now holds that the crystalline schists were
deposited in their present state and condition. A few at
most may have been formed by the first cooling of the
earth's crust perhaps some gneiss districts, if any such
can be found entirely free from subordinate interlying
beds. It is improbable that such origin can ever be satis-
factorily proved, and it remains for the present at best
an hypothesis which is possible for certain cases. Some
gneiss certainly appears to be of igneous (eruptive) origin,
but a very large proportion of the known gneiss forma-
tions admit of no such explanation, nor is it applicable
to any of the other crystalline schists. From a geological
point of view we shall therefore do well to consider the
eruptive gneiss as a schistose variety of granite, and
every other (for the present at least) as metamorphic.
Hence, according to the present state of our scientific
knowledge, the only explanation left for by far the greater
part of the crystalline slates is that of transmutation
from sedimentary formations.

The following are some of the principal reasons which
appear clearly to speak for such transmutation, without,
however, giving us certain information as to the manner
of the process :

1. Those rocks the traces of whose sedimentary origin
are evident and distinct, present us with numerous series
of transitions tending towards or rendering possible further
transitions into crystalline schist, or corresponding with
the subordinate beds which are found interlying those
schists. We will give a few instances of such series of
transmutation :

(a) Clay -mud successively passes into (or becomes)
argillaceous shale, clay-slate, argillaceous mica-schist,
and mica-schist. If this be so we should expect in
the final products of this series of transmutations to
find indications of the special composition of the dif-
ferent original clays influencing the character of each
rock, which accordingly should vary with the varying

380 PROCESSES OF ROCK FORMATION:

quantities of sand, lime, magnesia, potash, or soda con-
tained in the original clay. And to such differences of
original composition we do in fact attribute the different
varieties of mica-schist, or the formation in its stead of
gneiss, hornblende-schist, chlorite-schist, or talc-schist
(although the special character of the two latter is pro-
bably in some measure owing to the later accession of
solutions of magnesia).

(#) Sand passes into (or becomes) sandstone, quartz-
ite, quartz-schist, or itacolumite, according to the
character of the substances originally mixed with the
sand, or which have subsequently come to it. A mica-
schist rich in quartz, or a gneiss, might also result from
the transmutation of a sandstone having a copious com-
bining medium.

(c) Calcareous mud, consisting of microscopically
small shells, passes into (or has actually become) chalk ;
chalk (probably by means of pressure) has turned
to compact limestone. Chalk or compact limestone
under pressure, by means of a high degree of tem-
perature, may have been transmuted into granular lime-
stone, beds of which frequently occur in subordinate
layers between the strata of crystalline schists.

(c?) Browncoal, coal, anthracite, and graphite have
without doubt resulted from peat or other vegetable
accumulations. Anthracite and graphite we again find
as subordinate formations imbedded between strata of
crystalline schists.

(e) Hydrated oxide of iron forms a deposit in the
form of bog-ore or brown hematite, and these under
the pressure of thickly overlying masses appear to have
parted with their water, and become converted into red
iron-ore, or red hematite. Further, by the absorption
of one part of oxygen, red iron-ore is converted into
magnetic iron-ore. The latter is found in subordinate
layers between beds of crystalline schists. But in each
of these cases the transmutations are sometimes found
to have been reversed, and other processes have taken
place which have somewhat complicated the actual
phenomena.

2. The several kinds of crystalline schist and their
different varieties are found imbedded in manifold parallel

METAMORPHIC SCHISTS. 381

alternating layers or strata. Between these lie subordi-
nate layers of granular limestone, dolomite, quartzite,
ironstone, graphite, &c., and the whole series are found
stratified in a parallel direction. This alternate bedding
and imbedding correspond exactly with that of the sedi-
mentary rocks their state only is changed, being usually
crystalline. The bedding and stratification of the crys-
talline schists therefore furnishes a second and most im-
portant argument for their metamorphic origin ; in no
other way can the existing phenomena be accounted for.

3. The usual or normal bedding of the crystalline
schists is lower than that of all sedimentary rocks, and
complete gradual transitions between the two are fre-
quently to be observed. These outward indicia alone are
strong evidences of metamorphic origin.

4. Finally, we may bring certain more rare or ex-
ceptional phenomena in proof of the theory of transmu-
tation, e.g. the occurrence in strata of crystalline schist
of beds containing certain still recognisable fossils ; as for
instance the limestone-slate with remains of belemnites
between the mica-schist and gneiss of the Alps, at the
Furca and Pass of Nufenen. At the last-named locality
more recent formations are also found exceptionally very
much changed, but not entirely transmuted.

Taking all these facts together they appear to us to
furnish as complete a chain of indirect evidence in favour
of the transmutation of a very large proportion of the
crystalline schists as we could well expect to find where
from the nature of the case direct observation is un-
attainable.

The causes and manner of the transmutation, however,
constitute a different question.

The first theory of geologists upon this matter was that
the crystalline schists had been formed out of the sedi-
mentary by the operation of great eruptive masses of
igneous rocks thrusting themselves through, over, and by
the side of the sedimentary rocks therefore by the effect
of contact ; and it was also supposed that the felspar of the
gneiss was only forced into it from granitic compounds.
The frequent occurrence of granite in the immediate
neighbourhood of gneiss, the fact that granite districts
are frequently entirely surrounded by gneiss, which latter

382 PROCESSES OF ROCK FORMATION :

gradually merges into mica-schist towards its external
boundary (as for instance, in many parts of the Erzge-
birge) ; all these and like phenomena might no doubt
be cited in favour of such an hypothesis. But on the
other hand, no possible explanation could be afforded on
this assumption for the uniform distribution of the felspar
in the gneiss, nor for the extent of the supposed effect
of the contact without a regular diminution of force cor-
responding with the distance from the transforming cause.
Very frequently the observable mass of eruptive rock
(which according to the theory should be the cause of
the transmutation) bears no adequate proportion to the
extent of the crystalline schist (which has become trans-
muted). Many large districts of crystalline schist are,
moreover, entirely free from granitic or other eruptive
intrusions ; and it would, to say the least, be hazardous in
such cases always to presume the existence of a substratum
of granite which had failed to penetrate to the surface.
Again, many considerable granite districts are not sur-
rounded by gneiss or other crystalline schists, but on the
contrary are immediately in contact with distinctly sedi-
mentary rocks, which latter have remained almost entirely
unchanged by the contact, or at all events are not changed
into crystalline schists, although their bedding shows
clearly enough that they have been actually broken
through by the granite. The Hartz and Saxon Yoigt-
land afford remarkable instances of this kind. Thus we
find clay-slate formations of different ages broken through
by great masses of granite ; at the margin of the granite,
however, we find no trace of gneiss or mica-schist forma-
tions, but only the ordinary clay-slate changed for a
relatively small distance into horns tone, nodular schist
(Knotenschiefer), or chiastolite-schist changes which no
doubt have been caused by contact with the granite,
but which bear no resemblance to gneiss-formations, and
are probably the consequence more of a hydroplutonic
operation than of the high temperature of the granite
alone.

We are aware that Credner (in v. L. u. Br. Jahrb.
1849, p. 8) has described an occurrence at Glasbach on
the Schwarza, in the Thuringian Forest, where it really
appears as if the clay-slate, broken through by a very

METAMORPHIC SCHISTS. 383

considerable dyke of granite, has been transmuted into
gneiss for some short distance from the granite. Under
special circumstances, and if we find the clay-slate to
contain the same elements as the gneiss, we may well
admit the possibility of such an effect of the contact of
granite without our being authorised therefore to con-
clude that all gneiss has arisen from the same or similar
transmuting causes. We should rather regard such an
instance as proving that in particular cases special causes
have been competent to supply those more universal con-
ditions and processes of transmutation by which the
greater part of gneiss rocks have been formed ; just as in
the neighbourhood of basaltic rocks and porphyries ex-
ceptional formations of anthracite have taken place.

From all these considerations we gather that no effect
which could be produced by the contact of eruptive
igneous rocks would be sufficient to have caused the
formation of the great mass of the crystalline schists, but
that we should rather look for causes much more general
in their operation. These are most probably no other
than pressure and heat. We accordingly hold that not
only the crystalline schists but also the subordinate masses
imbedded in them are nothing more than the latest result
of that very general process of transmutation which all
sedimentary deposits have undergone and are still under-
going from the moment that they begin to be covered
more or less thickly with other more recent deposits.

Now a very thick covering with recent deposits can
only be the consequence of a previous depression. But
by the combined effect of depression and the weight of
fresh deposits the underlying strata are subjected not only
to an increased pressure but also an increased temperature.

In the earliest periods of the earth's development,
there probably was also an increased pressure from a
denser and more heavily laden atmosphere, and besides
the increase of heat with the depth from the surface,
there was doubtless a generally higher temperature of the
whole globe, so that the difference which now exists
between older and more recent igneous rocks, and be-
tween volcanic and plutonic rocks, would at that time
be much smaller, all volcanic formations partaking more
or less of the nature of the plutonic.

384 PROCESSES OF ROCK FORMATION:

Therefore, pressure and heat, with the addition, per-
haps, of water (which has either penetrated the earth to
a considerable depth or which chemically formed a part of
its original composition), appear to have worked together
through great periods of time to produce the final result
of the transmutation into crystalline schist; and those
crystalline schists which are now to be seen on the earth's
surface must also have been lifted and partially deprived
of their superincumbent masses. But as each process of
covering, of transmutation, of raising and re-exposure,
must have occupied extensive periods of time, it follows
that all crystalline slates which are now accessible to ob-
servation are of very ancient formation. In general lan-
guage, they may be said to represent the oldest deposits
in a metamorphosed state. Exceptions to this character
can only be attributed to special circumstances. In the
Alps, such exceptions do appear to have taken place. The
deposits of the Jurassic, the Chalk, and the Tertiary periods
exhibit there an extraordinary thickness of development,
and, consequently, belemnitic strata (of the oldest deposits
of the Jurassic period) appear in certain places to have been
so thickly covered as to have been changed into crys-
talline schist ; and very energetic upliftings have also at
a later period exposed them.

In general we may say of the Alps, that the process of
metamorphosis has been there pushed up higher in the
scale of the earth's history than elsewhere is usual. The
Eocene deposits contain firm clay-slate, which is used for
roofing purposes ; the Miocene browncoals of the Mo-
lasse formation appear already to have almost become
ordinary black coal, &c. On the other hand, we find the
converse of this state of things in the low lands of Russia,
where the oldest Silurian formations are still partially in
the state of plastic clay and friable sandstone, probably
because they have never been thickly covered.

The temperature to which the lowest deposits have been
subjected, under very great pressure of thicklying super-
incumbent masses, may even have reached so great a
degree that some or all of the rocks composing such strata
have been softened or perhaps partially fused. In this way,
for instance, we may explain the otherwise singular pheno-
menon of layers of granular limestone which sometimes

METAMORPHIC SCHISTS. 385

lie between beds of crystalline schist; yea, even sili-
ceous rocks may have been softened by this means, en-
tirely losing their slaty texture and stratification.

No doubt, we may be easily led by such speculations
into regions of unfounded hypothesis, but the causes to
which we have referred afford a possible explanation of
many bedding relations between granulite and gneiss,
which cannot be accounted for by simple transmutation
from a sedimentary formation.

Now, granted that we are able to explain the special
state of the crystalline schists by such general plutonic
influences as pressure and heat, there yet remains the im-
portant question whether their chemical composition also
corresponds with this theory of their transmutation; in
other words, whether the sedimentary rocks originally
contained, or could have subsequently absorbed, those in-
gredients which were necessary to the formation of the
crystalline schists. In many of the sedimentary rocks this
is most certainly the case. We need only compare the
ingredients of the crystalline schists with those of the as
yet uncrystalline slates as given in the tables, p. 86,
ante, in order to perceive that, even without the accession
of new ingredients or parting with any which they now
contain, many a clay-slate might be changed into a mica*
schist, and others into a gneiss, if their ingredients could
be so disposed as to combine into crystalline mineral ag-
gregates. The elements are there; the opportunity of
assuming a new shape is the only thing wanting. The
composition of different clay-slates, several of which also
contain some lime and magnesia, corresponds with that
of many different varieties of gneiss, mica-schist, and
hornblende-schist. Doubtless an additional quantity of
magnesia would be necessary to the formation of the
chlorite and talcose schists, but the possibility of the ac-
cession of solutions of magnesia is proved beyond doubt
Ity llie existence of numerous pseudomorphs of certain
well-known minerals. With reference to the formation of
these magnesian rocks (to which serpentine also belongs),
certain special conditions would appear to have been ne-
cessary in their case in addition to the general causes
which contributed to the formation of the great mass of
the other crystalline schists.

c c

386 PKOCESSES OF KOCK FORMATION :

Our hypothesis (to which, however, we lay no personal
claim) by no means excludes the possibility of water as an
auxiliary agent in such transmutations as we have de-
scribed. The comparatively recent experiments of Daubree
have established that water will remain in combination
with other substances, such as silicates, under high atmo-
spheric pressure, even at a white heat ; and that in such
cases it even materially affects the fusing point of sub-
stances ; and Scheerer has proved that the water con-
tained in the mica of gneiss was a part of its original com-
position. This water may have caused many phenomena
in the interior of the earth, which as yet we are not able
accurately to explain or prove.

What thickness of superlying strata should be assumed
as sufficient to produce the transmutation which has re-
sulted, we are unable to say ; and we have fewer data for
any computation, as, according to the igneous theory of
the earth's formation, the average temperature of the
whole globe, including the surface, must formerly have
been much higher, and the atmosphere more compact and
dense, therefore the pressure much greater, than at the
present day. Moreover, in all geological phenomena
the duration of a particular influence will to some ex-
tent supply any deficiency in its energy ; and, as we have
no standard by which to measure the time of geological
processes, we have free scope to assume any duration of
time that appears necessary to explain their operation.

The crystalline schists, if we take their principal repre-
sentatives, gneiss and mica-schist, are more closely allied
to the acidic than the basic igneous rocks. The cause of
this is easily explained. In the igneous rocks, the two
principal bases, whose greater or less proportion chiefly
creates the distinction between the acidic and basic groups,
are lime and magnesia. Now, on the decomposition or
disintegration of the igneous rocks, their lime and mag-
nesia having first been taken up in solution (for the most
part in combination with carbonic acid), have then been
separately deposited in the form of independent beds of
limestone and dolomite. The aluminous and quartzose
ingredients of the igneous rocks have formed the more
mechanical deposits of clay and sand, free from lime, and
appear to have produced the greater part of the crystal-

METAMORPHIC SCHISTS. 387

line schists ; and as the calcareous and magnesian deposits
were originally formed between the strata of clay and
sand, so we again meet with limestone and dolomite rocks
imbedded between the acidic crystalline schists ; and we
may assume that they represent the collective amount of
lime and magnesia in which the average of the crystal-
line schists is deficient as compared with the average of
the igneous rocks. This separate development of the
lime and magnesia may likewise be the reason why com-
binations of hornblende, pyroxene, and labradorite are,
generally speaking, far less frequent in the crystalline
schists than in the igneous rocks.

The crystalline schists, according to our theory, must
represent the most ancient or undermost deposits of the
world's history. They are the oldest rocks of which we
have knowledge, since we find them overlaid by all the
sedimentary rocks, and broken through by every kind of
igneous rock. But the question arises, upon what foun-
dation can these deposits have first rested, if no other
rocks were previously in existence? Doubtless there
must have previously existed a firm foundation or floor of
deposit separating the fused mass of the interior from the
covering of water and air, by whose means alone deposits
could be formed. If, therefore, we acknowledge the fused
state of the whole earth as its most ancient geological
condition, we are necessarily led to assume the existence
of a very thick first crust, caused by the cooling of the
surface of this molten matter before it would be possible
for any sedimentary or eruptive rocks to form. Now
what has become of this first crust, unless it be repre-
sented by the crystalline schists ? It is certainly difficult
categorically to answer a question of this nature, refer-
ring to ages and circumstances long since passed; but
one thing is certain, viz. that such gneiss, mica-schist, or
argillaceous mica-schist, as contain parallel subordinate in-
terlying beds of limestone, dolomite, hornblende-schist,
quartz-schist, ironstone, or graphite, and the like, can-
not have been formed by the first cooling of the earth's
mass. No doubt where such interlying beds are entirely
absent, as, for instance, in some gneiss, it is possible that
such districts may be the remains of a first crust of the
earth. Further, it is not certain that all granite is of

c c 2

388 PROCESSES OF EOCK FORMATION:

eruptive origin ; indeed, there are many circumstances
that point to a contrary assumption in certain districts.
Here, therefore, we have something which may possibly
date from the first cooling of the earth's surface. But
uniform districts of gneiss containing no foreign subordi-
nate beds, and granite districts without recognisable
traces of eruptive origin, are phenomena so rare to our
present geological experience, that they evidently do not
suffice to represent a great primeval crust of the earth.
Under these circumstances, there seems nothing left for
us in the present state of our knowledge but to assume
that the greater part of the first crust, having become
very thickly covered with deposits, has been gradually
remelted and become eruptive, perhaps in the form of
granite. There is, indeed, no reason why the same fate
should not have been shared by the oldest rocks of de-
posit ; and thus it may be that the chronological starting-
point of geological development has frequently been
effaced, and become altogether uncertain.

In what we have said above, we have endeavoured to
develope the plutonic theory of the origin of crystalline
schists. Recently, however, other explanations of the
origin of those rocks have been started, not so much by
geologists as by chemists, who also assume their origin
by transmutation from sedimentary rocks, and differ from
the geologist chiefly in denying all plutonic agency, only
acknowledging the efficacy of such chemical processes as
might have taken place under the conditions existing at
the surface of the globe.

We have already more than once shown, in the course
of this work, that plutonic processes do not exclude the
combined action of water as an auxiliary agent ; and thus
may deserve the name of HTDROPLUTONIC; but, according
to the more recent views of some chemists, water alone is
said to suffice, under circumstances of ordinary pressure
and temperature, to have brought about these transmu-
tations in the course of time.

We do not venture to pronounce upon such theories
from a chemical, but only from a geological point of view,
and in this respect they do not satisfy our mind, chiefly
because they disregard the effect and influence of very
thick overlying strata, therefore of high pressure and

METAMORPIIIC SCHISTS. 389

increased temperature ; because they do not explain why,
for instance, in the Alps, very recent deposits are greatly
altered in character, whereas in other countries very old
deposits where they have remained uncovered are scarcely
changed at all (as, for instance, in Northern Russia);
and finally, because they leave the phenomena of con-
temporaneous mechanical changes, such as condensation,
slaty structure, &c., entirely unexplained. Assuming it
to be the fact that by the agency of water alone, under
circumstances of ordinary pressure and temperature, mica-
schist or gneiss, hornblende-schist, &c., might be produced
from clay (argillaceous shale or clay-slate), it would still
be difficult to believe that by such agency proceeding from
the surface, whole complicated systems of strata should
not have been more locally influenced, and very differently
affected at different depths, instead of having been almost
everywhere equally and uniformly influenced by the trans-
forming cause. Again, if all these important changes
and transmutations were entirely or chiefly due to water,
it would be very extraordinary if we did not find that
they had been occasionally modified by the increase of
temperature and of pressure to which they must have been
subjected, since we cannot shut our eyes to the existence of
such influences in the interior of the earth, and numerous
geological facts sufficiently prove that many rocks which
once were very thickly covered have been subsequently
laid bare by processes of uplifting and denudation.

If we adopt the pure chemical hypothesis, then we must
abandon the idea of that relationship existing between
bedding and transmutation which, according to the plutonic
theory, is an invariable law. It is indeed somewhat sus-
picious that the supporters of the chemical theory, in
order to make the plutonic appear improbable, almost
entirely dispute as a fact the operation of pressure and in-
creased temperature in the interior of the earth, whereas
every unprejudiced person acquainted with the rudiments
of physics must admit these forces to exist inevitably
under the given circumstances. The same persons are
even in the habit of disputing the eruptive character of
the greater number of igneous rocks, from which we
infer that they are deficiently acquainted with geological
facts from personal observation. We purposely use the

390 PROCESSES OF ROCK FORMATION:

word eruptive (not igneous) because the eruptive cha-
racter of the rock is unmistakably proved by the form of
its mass, even if occasional doubts should arise as to the
actual state of some few rocks at the time of their in-
trusion.

In other words, we do not regard those chemists very
competent guides in pure geological questions, who fail
adequately to regard the external phenomena of form and
bedding no less than the elementary composition of rocks.

We would not be understood to depreciate the careful
experiments and researches which we owe to Gr. Bischof
and others on the effect of water in the processes of for-
mation and transmutation of minerals. These are highly
instructive, and they are more especially valuable as
clearing up and explaining very scientifically what was
previously only matter of surmise respecting the nature of
the process of formation of mineral deposits in vesicular
cavities and fissures of some rocks, and respecting the
special formation and transmutation of minerals in the
interior of other rocks, by which latter process, for in-
stance, serpentine, chlorite-schist, talcose schist, &c., may
in many instances have resulted.

In the course of these observations mention has been
made of transmutation by means of contact ; i. e. of such
transmutations as are found at the margin or in the
neighbourhood of eruptive igneous rocks which have
broken through sedimentary rocks. That such exist
cannot be doubted ; as a rule, however, they extend to
only a very limited distance from the eruptive rock.
They may be divided into such as are purely plutonic or
hydroplutonic, and such as are volcanic processes. To
the plutonic processes belong the formations of hornstone,
nodular schist (Knotenschiefer), and chiastolite-slate on
the contact-margins of granite or greenstone. To the
volcanic processes belong special induration, slacking,
vitrefaction, coking and columnar jointing of argilla-
ceous sandy or carboniferous rocks on the margins of
basalt, trachyte, or porphyry. These latter cases appear
to be simply the result of greatly increased temperature
and subsequent rapid cooling without water. The plu-
tonic processes, on the other hand, admit of the combined
agency of water and heat.

METAMORPHIC SCHISTS. 391

Transmutations occasioned by the burning of beds of
coal (as the burnt clays, described p. 338, ante) are pro-
cesses of entirely local character, and there may be many
other such which it is unnecessary further to describe for
our present purpose.

The transmutations of which we have hitherto spoken are
chiefly such as have taken place in the interior of the earth
with exclusion of atmospheric air. For these Haidinger
has proposed the term catogenic in contradistinction to
the anogenic transmutations which proceed from the ex-
terior towards the interior, under the influences of air and
water. These latter correspond in part with the very
general process of weathering the rocks ; they do not,
however, always consist in the decomposition or disin-
tegration of the masses affected, but sometimes rather in
the formation of hydrates. To this belong the coalescing
of the felspathic rocks, the formation of wackes by means
of compounds containing augite or hornblende, the for-
mation of gypsum from anhydrite, &c. These anogenic
transmutations likewise play an important part in the
chain, of processes by which in nature matter circulates
through its various forms.

The most striking of the contrasts between the cato
genie and anogenic transmutations may be stated some-
what in the following manner :

Catogenic. Anogenic.

Condensation and induration. Disintegration.

Crystallisation. Frequent destruction of the crys-

talline state.

Deoxidation. Oxidation.

Loss of water (to a certain Formation of hydrates.

extent).

Formation of slaty schistose or
texture.

The following recent works may be here cited as espe-
cially noteworthy upon the metamorphosis of rocks :

St. Claire Deville, the Operation of Chlorides and Sulphates upon
the Metamorphism of the Sedimentary Rocks, Compt. rend.
1858, vol. xlvii. p. 89.

A. Gages, on the Study of some Metamorphic Rocks, Philos.
Mag. 1859, March, p. 169.

O. Lieber, Critique on the Views of Bischof and Naumann on
the Subject of Metamorphism. in Mining Mag. vol. i. Decem-
ber 1859.

392 PROCESSES OF ROCK FORMATION.

Delesse, Etudes sur le Metamorphisme des Roches, Paris, 1861 :
v. L. u. Br. Jahrb. 1858, pp. 335 and 727, 1859, pp. 222 and
223 ; 1'Institut, 1861, p. 276.

Daubree, Etudes sur le Metamorphisme et sur la Formation des
Koches Cristallines, Paris, 1860.

MINERAL VEINS AND VEINS OF ORE.

These almost form a special group of rocks, and would
be entitled to an equal place by the side of the three
other groups, if the extent of space which they occupy in
nature were not so small. They but fill up narrow fis-
sures in other rocks. Their origin appears, almost with-
out exception, to have been hydroplutonic. They are, for
the most part, chemical precipitates from aqueous solu-
tions formed in the interior of the earth under very dif-
ferent circumstances of pressure and heat than those
which prevail upon the surface.

Having treated these formations, which occupy so sub-
ordinate a space in the composition of the earth's crust,
at length in our book on ' Erzlagerstatten,' we shall not
devote further space to them here.

CONCLUSION.

BEARING in mind the facts and considerations above
stated, if we take a general review of the various forma-
tions and transformations of rocks, we shall discover in
them a perpetual process of circulation or rotation of
substances, and of their different states. The substances
remain, but the forms in which they appear and the mode
of their combinations vary.

Disregarding for the moment the first solid products
of cooling on the earth's surface, as not being capable of
identification at the present day, we may most conve-
niently enter the circle of transmutations with the erup-
tive igneous rocks, as approaching most nearly to original
formations. These then are constantly attacked and de-
composed by chemical and mechanical forces acting from
their surface inwards, and from their cracks and fissures
outwards.

The products of this decay are deposited either in the
form of chemical precipitates or mechanical aggregates.
By chemical process of precipitation cavities and fissures
in rocks become filled up (amygdaloids and veins), depo-
sits are made at the mouths of springs of limestone-tuff,
siliceous tuff, bog-ore, &c. ; or else, other crystalline rocks
are formed, such as gypsum or rock-salt. By mechanical
agency, on the other hand (partly aided by organic pro-
cesses), there arise the much more important and exten-
sive deposits of clay, sand, pebbles, marl, limestone, and
dolomite ; and during the process of deposit, carbon (in
the form of carbonic acid from the atmosphere), water,
chlorine, and some other substances are added to the pre-
viously existing materials.

But, like the eruptive masses, all these deposited masses
in their turn are partly decomposed and washed away by
external forces, and in other part they become greatly
changed internally by pressure and the action of heat.

394 PROCESSES OP EOCK FORMATION.

By means of heat and pressure acting during long periods,
parts which thus in the first instance were only mecha-
nically bound together, enter into new chemical com-
binations with each other, and assume a crystalline state
more or less analogous to that of the crystalline mineral
aggregates of the eruptive rocks. It is even pro-
bable in many cases that the substance of these deriva-
tive rocks has been fused and become eruptive a second
time.

Thus the process of destruction and new formation of
rocks, be it ever so slow, and therefore difficult of ob-
servation, has never, at any time of the earth's history,
been interrupted, but continues at the present day ; and
not only is this true of the original formations, but the
new products of consolidation, of deposit, and of transmu-
tation have always been equally subjected, and are still
subject, to the same processes.

This is the perpetual circulation of matter in the world
of rocks.

In the course of such various and renewed working up
and transformation of the same substances, with the addi-
tion of those others furnished by the air and water, it
cannot be matter of wonder that the variety of their
groups has been always somewhat on the increase ; for, if
certain processes in this rotation are altogether universal
in their character, recurring in the same way, everywhere
and in every age, yet in consequence of the general mul-
tiplication of conditions and circumstances, and the in-
creasing aggregate of their results, special combinations
of the same processes have constantly arisen in later times
and brought about special formations of rocks which were
not previously in existence, or which do not belong to
the normal phenomena of nature.

This increase in variety of the products of later times
is not confined to geological and mineral substances ; a
greater and more rapid increase has taken place in the
organic world, where the forms of life have multiplied in
an ever ascending ratio (partly in consequence of the
change and increase of the conditions of existence from
geological causes).

The processes of change, to which the outward con-
formation of the globe's surface is subject, likewise mul-

CONCLUSION. D95

tiply more rapidly than mere strictly geological pheno-
mena.

Reasoning, therefore, from the past and from analogy
with other kingdoms, we must expect the species of rocks
and kinds of rock-formation to go on increasing inde-
finitely for the future, as they have been increasing con-
tinually ever since the first solidification of our earth's
crust.

INDEX OF LOCALITIES.

AAC

* ACFIEN, smithsonite of, 34
** Aberdeenshire. andalusite of, 35
Adamello Mountains, in Southern Tyrol,

tonalite of, 207
Adam's Peak, Ceylon, oligoclase-gneiss

of, 239

jEcrjna, trachyte of, 186
.<Etna, alum, near the crater of, 50

dolerite of, 137

hematite of, 63

labradorite in the lavas of, 1 1

trachyte of, 186, 188, 192
Africa, limestone of, 282

lower chalk of, 283

nummulitic limestone of, 282, 283

trona of, 59, 352

Acordo, in the Alps, pyrites of, 358
Aix-la-Chapelle, galmey of, 356
Ajaccio, diorite of, 155
Albanian Mountains, leucite rock of,
143, 186

peperino of the, 308

Algarve, in Portugal, foyaite of, 181
Algeria, nummulitic limestone of, 282
Alleghany Mountains, anthracite of, 336
Allgau, allogorite of, 142
Almaden, in Spain, cinnabar of, 358
Alps, adularia of the, 9, 201

alpiniteof the, 239

analcime of the Seisser Alp, 30

anhydrite of the, 48

browncoal of the, 330

chlorite-schist of the, 250

dolomite of the, 289

firn or ne\e of the, 346

fluor-spar of the, 69

gneiss of the, 239

granite of the, 206, 207

greenovite of the, 47

gypsum of the, 49, 292, 293

limestone of the, 283, 284

chalk formation of the, 283

melaphyre of the. 163

mica-schist of the, 244

nagelflue of the, 303

AME
Alps continued

red sandstone of the, 300

pebbles at the foot of the, 102

potstone of the, 251

pyrites of the, 358

roofing slates of the, 265

shale of the, 267, 268

sandstone of the, 299

talc-schist in the, 252

mica-schist of the Eastern, 244

celestine of the Seisser, 48

Alps, Northern, breccia-like rocks of, 305

dolomite of the, 289

glauconite of the, 27

marl of, 274

Alps, Pennine, dolerine of the, 252
Alps, Western, spilites of the, 167
Alpujarras, in Spain, galena of, 70
Alston Moor, aragonite of, 58
Altai Mountains, porphyrite of the, 170
Altenberg, in Saxony, chlorite of, 25

granite-porphyry of, 214

granular limestone near, 277

greisen near, 321

Zwitter rock of, 322

pycnite of, 354

Altenhain, in the Erzgebirge, granite-
porphyry of, 213
Amberg, yellow earth of, 356
America, limestone of, 283

lower chalk of, 283
America, North, alunogen of, 50

apatite of, 53

blue spinel of, 61

catawbirite of, 345

chromic iron-ore of, 62

franklinite of, 357

hornblende-schist of, 254

mispickel, of, 74

nncritide of, 244

itacolumite of, 249

naphtha of, 77

orbitoidal limestone of, 283

petroleum or rock-oil of, 337

rutile of, 66

INDEX OF LOCALITIES.

AME

America, North tontinued

specular iron of, 343

titanite of, 47

trona of, 59

America, South, andesite of, 192

felspar rocks of, 188

itacolumite of, 248

trachyte of, 186

Amiano, in Parma, naphtha of, 77
.Andernach, on the Eliine, leucite rock
near. 143

titauite of, 47
Andes, andesine of the, 1 1

felspar rocks of the, 188
Andreasberg, analcime of, 30

anhydrite of, 48

apophyllite of, 30

harmotome of, 32

Antisana, in South America, andesite
of, 192

trachyte of, 186

Antrim county, granular limestone of, 278

phillipsite'of, 32
Arabia, turquois of, 54
Aragon, nitre of, 55

Ararat, Mount, andesite of. 192
Ardennes, ottrelite-schist of the, 256
Arendai, in Norway, apatite of, 83

graphite of, 75

magnetic iron- ore of, 61, 345

pistacite of, 42

scapolite of, 42

titanite of, 47
Argyleshire, titanite of, 47
Arksatfiord, in West Greenland, cryolite

of, 69

Artern, in Thuringia, mellite of, 77
Ascbaffeaburg, gneiss of, 239

granite-porphyry of, 213

titaniferous iron of, 63
Asia Minor, corundum of, 351

nummulitic limestone of, 283
Aue, in Saxony, kaolin of, 354
Auerbach near Heidelberg, granular

limestone of, 278
Auerbach, in the Odenwald, kinzigite

of, 320

Aulgasse, in Siegburg, dolerite of, 135
Aussig, in Bohemia, natrolite of, 32

phonolite of, 200

Autun, in France, bituminous sub-
stances of, 77
Auvergne, alunite of, 52

apophyllite of, 30

colourless hyalite of, 8

scolecite of, 33

BER

Auvergne continued

zircon of, 41

Averno, Lake of, leucite of, 185

Azores, trachyte in the lavas of the, 190

BADEN, pyrochlore of, 45
perofskite of, 45

Ballybrack, near Dublin, granite of, 206
Baltic, amber on the coasi of the, 76
Bannat, apophyllite of the, 30

coal of the, 334

Barenburg, in the Erzgebirge, granite-
porphyry of, 213

Barnstaple, in Devonshire, wavelliteof, 55

Barre, in Massachusetts, rutile of, 66

Barton clay, 270

Baste, in the Hartz Mountains, schil-
ler-spar of, 19

schiller-rock of the, 316
Bath, stone of, 280
Bavaria, apatite of, 53

cordierite of, 44

columbite of, 46

flint in the Upper White Jurassic
of, 6

glauberite of, 49

graphite of, 336

kinzigite of, 320

nodular limestone of, 280

opal of, 349

ottrelite-schist of, 256

siliceous spherosiderite of the Alps
of, 346

slaty limestone of, 281

vivianite of, 54

Baveno, common felspar of. 10
Baveno, in the Alps, granite of, 206
Belfaly, in the Vosges, aphanite of, 160
Bell, near Andernach, leucite rock of, 143
Bellmansloos, near Tharand, felstone of,

222
Belmsdorf, in Oberlausitz, aphanite of,

161

diorite of, 155

Berchtesgaden, in Bavaria, glaubersalt
of, 51

glauberite of, 49

Beregheacz, in Hungary, alum-stone of,
309

trachyte-porphyry of, 195
Beresowsk, in the Ural, beresite of, 207

talc-schist of, 252
Berggieshiibel, in Saxony, magnetic

ironstone of, 345
Berlin, glauconite of, 27

INDEX OF LOCALITIES.

399

BER

Berneck, in the Fichtelgebirge, diabase
of, 147

mica-schist near, 244

gneiss near, 239

Bex, in Switzerland, gypsum of, 293
Bilin, in Bohemia, aragonite of, 58

opal found in the tripoli of, 8

rock-soap of, 355

semi-opal of, 349

Binnen Thai, in the Alps, dolomite of

the, 289

Birkenlioff, red melaphyre of, 166
Black Forest, kinzigite of the, 320
Blanc, Mont, gneiss of, 239
Blattendorf, in Bohemia, phonolite of,

200
Bleiberg, in Carinthia, galena of, 70

smithsonite of, 34
Blumau, porphyry of, 218

Bocche, Monte, in Tyrol, porphyry of,

218
Bodenmais, beryl of, 39

columbite of, 46

cordierite of, 44

kinzigite of, 320

vivianite of, 54
Bognor, clay of, 270
Bohemia, alum of, 50

amber of, 76

apatite of, 53

aragonite of, 58

basalt of, 141, 142

bituminous substances of, 77

colourless hyalite of, 8

egeran of, 318

epsomite of, 50

felspar of, 10

glaubersalt of, 51

gneiss of, 238, 239

granite of, 202

granulite of, 231

granulite-gnei*s of, 238, 239

marcasite of. 73, 357

marl of, 273

mellite of, 77

mica-schist of, 242

natrolite of, 32

phonolite of, 187

phonolites of, 198, 200

polianite of, 65

polishing slate of, 350

pyrope of, 41

rock-soap of, 355

sandstone of, 299

thomsonite of, 31

titanite of, 47

CAN

Bohemia continued

wavellite of, 55
Bb'hmisch-Wiesemhal, leucite rock of,

143
Bohrineen, in Saxony, gabbro of, 151

serpentine of, 317
Bologna, barytes near, 48
Bonhomme, Col du, albite of, 11
Bonn, alunogen of, 50

bituminous substances of, 77

trachyte of, 184, 190
Borghetto, leucite of, 186
Borrowdale, in Cumberland, graphite of,

75, 336

Borsabanya, in Hungary, timazite of, 156
Boston, in Massachusetts, potstone ot,

251

Botallock, in Cornwall, axinite of, 44
Botzen, in the Tyrol, laumontite of, 32

porphyry of, 218

Boxdorf, near Moritzburg, granite-gneiss
of, 238

Brambach, in the Voigtland, granite-
gneiss of, 238

Brandau, in the Erzgebirge, anthracite
of, 336

Brandholz, in the Fichtelgebirge, mica-
schist near, 244

Brava, Island of, nosean of, 15

Brazil, Carveira of, 234

itabirite of, 343

itacolumite of, 248

moorshead rock of, 343
Brest, kersanton of, 175

Brevig, in Norway, pyrochlore of, 45

wohlerite of, 46

zircon-syenite of, 181
Briesgau, jasper of, 6

granular limestone of, 278
Britain, felstone of, 222
Brittany, kersanton of, 175

staurotide of, 36

Brixen, in the Tyrol, granitite of, 207
Bronzell, in Tyrol, porphyry of, 218
Bnchenberg, in the Uartz, wernerite
rock of, 222

, stone of, 280
Calabria, nitre of, 55
Calais, glauconite of, 27
California, borax of, 53

naphtha of, 77

Canada, chloritoid schist in, 251

naphtha of, 77

serpentine rocks of, 317

400

INDEX OF LOCALITIES.

CAN

Cantal, in France, schistous trachyte of,

184
Capo Loneo, south of. St. Gotthard,

tourmaline of, 37
Caradoc, sandstone of, 301
Carinthia, galena of, 70

smithsonite of, 34

Carlsbad, in Bohemia, aragonite of, 58

common felspar of, 10

fibrous limestone of, 281

glaubersalt of, 51

granite of, 205

marcasite of, 73

orthoclase of, 354

peastone of, 280
Carolina, itacolumite of, 249

catawbirite of, 345

Carpathian Mountains, chlorite-schist of
the, 250

limestone of the, 284

sandstone of the, 299

shale of the, 267

Carrara, common quartz in the marble

of, 6

Castelruth, porphyry of, 218
Castleton, in Derbyshire, elaterite of, 77
Catini, Monte, in Tuscany, trachyte of,

184
Caucasus, andesite of the, 192

trachyte of the, 186

Cavalessi, in Southern Tyrol, porphyritic

rocks of, 170

Cevennes, fraidonite of the, 175
Ceylon, nitre of, 55

oligoclase-gneiss of, 239

precious corundum of, 8

spinel of, 61

Chaux, near Frejus,blue porphyry of, 171
Cheltenham, pea-grit of, 280
Chemnitz, in Saxony, chlorite-schist
near, 250

porphyry near, 217
porphyry-tuff of, 309

Chessy, near Lyons, malachite of, 60
Chiavenna, potstone of, 251
Chili, nitratine of, 55
Chimborazo, andesite of. 192

trachyte of, 186
China, agalmatolite of, 354

precious corundum of, 8

Cilli, in Styria, fullers' earth of, 356
Cimini Mountains, trachyte of the, 184
Clermont. trachyte near, 186
Colima, Mount, in Mexico, trachyte of,

186
Commern, in the Eifel, galena of, 70

DIP

Compain, Pas de. in France, schistous

trachyte of, 184
Connecticut, chabasite of, 31

columbite of, 46

Corbitz, near Meissen, pitchstone of, 224
Cornwall, axinite of, 44

common felspar of, 1

common quartz of, 5

greisen of, 321

kaolin of, 13

malachite of, 60

marcasite of, 73

quartz-porphyry of, 219

saponite of, 26

titaniferous iron of, 64

topaz of, 36

tourmaline of, 38

vivianite of, 54
Corsica, anorthite, of, 12
=- diorite of, 155

porphyry of, 218
Cotopaxi, andesite of, 192

trachyte of, 186
Criffel, zircon of, 41
Crimea, meerschaum of, 354
Croatia, sulphur of, 358

Csetatye, in Transylvania, porphyry of

219
Cumbal Euca Pichincha, in South

America, trachyte of, 186
Cumberland, chiastolite-schist of, 257

galena of, 70

graphite of. 75, 336

limestone of, 285

Cyclopean Islands, near Sicily, analcime
of the, 30

TvANEMORA, in Sweden, magnetic

J ironstone of, 61, 345
Danube, gneiss on the, 239

granite on the, 207
Dead Sea, asphalte of the, 77

bitumen of the, 337
Derbyshire, dolomite of, 290

elaterite of, 77

galena of, 70

smithsonite of, 34

Desert, jasper in the sand of the, 6
Devonshire, andalusite of, 35

wavellite of, 55

Dilln, near Schemnitz, agalmatolite of,

354
Dippoldiswalde, in Saxony, felstone of,

222

gneiss of, 239

INDEX OF LOCALITIES.

401

DIP

Dippoldiswalde continued

minette of, 174

Ditro, in Transylvania, syenite of, 179

wohlerite of* 46

Domokos. in Transylvania, pyritesof, 358
Dore", Mont, augite of, 185
Bore's, Monts, in Ve'lay, trachyte of, 184
Dossenheim, in the Odenwald, granite

of, 207
Draclienfels, sanidine of the, 10

trachyte of the, 184, 185, 190
Dresden, alunogen of, 50

gneiss near, 238

hornblende- porphyrite of, 171, 172

laumontite, 32

oligoclase of, 11

orthite of, 43

syenite near, 176, 178, 179
Drontheim, in Norway, potstone of, 251
Drusenthal, in the Timringian Forest,

granite-porphyry of, 207
Dublin, freestone of, 298

granite near, 206
Dumbartonshire, analcime of, 30

prehnite of, 31

thomsonite of, 31

laumontite of, 32
Dunse sandstones, 300
Dura-den sandstones, 300

Durance, variolitic aphanites of the, 159
Durham, dolomite of, 290

EBERSDORF, in Saxony, coal of,
333

Ebnat, in Bavaria, ottrelite-schist of. 256
Kdenville, in New York, rutile of, 66
Edinburgh, porphyry near, 170
Eibenstock, in the Erzgebirge, granite
of, 206

mica-schist of, 244

schorlaceous schist of, 323
Eifel, galena of the, 70

trachyte of the, 191

Eger, in Bohemia, egeran of, 318

granite of, 205

k'ranulite-gneiss of, 238, 239

gneiss -f, 239

mica- schist of, 243
Egypt, chrysolite of, 38

natron of, 59

nummulitic limestone of, 283
Elba, Island of, epidosite of, 355

lievrite <f, 37, 356

specular iron of. 343
Elbingerode, in the Hart a, graphite of, 75

labradorite-porphyry of, 160

FAR

Elfdalen, in Sweden, chrysolite of, 39
hypersthenite of. 152

porphyrite of, 170

Elgersburg, in Thuringia, braunite of,

Ellenbogen, granite of, 205
Engadine, serpentine of the, 317
England, dolomite of, 289, 290

flint in the chalk of, 6

gypsum of, 293

limestone of, 278

marl of, 273

Portland stone and oolite of, 284

sandstones of, 298, 299

upper and lower chalk of, 283

Wenloc-k shale of, 268

clays of, 270
Epsom, epsomite of, 51
Erlbachgrund, in Saxony, dichroite rock

of the, 320

Erbendorf, porphyry near, 218
Erzgebirge, actinolite-srhist of the, 254

corundum of the, 351

gneiss of the, 233. 234, 236, 239

granite of the, 206

granite-porphyry of the, 213

greisen of the, 321

mica-schist of the. 243. 244

mica-trap rocks of the, 173

nodular or spotted schist of the, 257

phonolite-tufa of the, 309

porphyry of the, 217, 218

protogine of the, 206

quartz-breccia of the, 305

serpentine of the, 317

talc-schist of, 252

Essex, amber on the coast of, 76
Euganean Hills, Lombardy, trachyte of,
184

trachyte-porphyry of the, 195
Europe, lower chalk of, 283

nummulitic limestone of the South
of, 282

Evigtok, in Greenland, cryolite of, 353

FAHLUN, in Sweden, automolite of, 61
gadolinite of, 43

mica-schist of, 242

pyrites of, 358

Fahrnleiten, in the Fichtelgebirge, gra-

nulite- gneiss of, 239
Faroe, apopliyllite of, 30

chabasite of, 31

heulandite of, 33

laumontite of, 32

stilbite of, 33

402

INDEX OF LOCALITIES.

FAS

Fassa Thai, apophyllite of, 30

augite-porphyry of, 160

chabasite of, 31

heulandite of, 33

idocrase of, 41

melaphyre of, 163

prehnite of, 31

stilbite of, 33

Fetlar, Island of, chromic iron -ore of, 62
Fezzan, in North Africa, trona of, 352
Fichtelgebirge, aphanite of the. 159

chiastolite-schist of the, 257

chlorite-schist of the. 250

diabase of the, 147-149

eklogites of the, 318

gneiss of the, 239

granite of the, 202, 205, 207

granulite-gneiss of the, 239

graphite of the, 75

hornblende-schist of, 253, 254

mica-schist of the, 242, 243, 244

porphyry of, 170

serpentine of the, 315, 317

talc, or steatite of the, 354

zoisite of the, 42
Fichtenmahle, near Meissen, pitchstone

of, 224

Figzan, North Africa, trona of, 59
Finland, rappakavi (granite) of, 205

tantalite of, 46

Flbha, in Saxony, porphyry-breccia of,

310
Forfarshire, flagstones of, 300

phonolite of, 201

Foya Mountain, in Portugal, foyaite of,

181
Framont, in the Vosges Mountains, mi-

nette of, 173
France, bituminous substances of, 77

blue porphyry of, 171

boracite of. 52

calcaire grossier of, 282

flint in the chalk of, 6

fluor spar of, 69

granite of, 206

kersanton of, 175

malachite of, 60

menilite of, 278

polianite of, 65

schistous trachyte of, 184

siliceous concretions of, 279

trachyte of, 186

Franconia, in New Hampshire, mispickel
of, 74

Frankenberg, in the Erzgebirge, granite-
porphyry near, 213

GIA

Franklin, in New Jersey, franklinite of,

357
Franzensbad, in Bohemia, polishing slate

of, 350

Frauenstein, granite-porphyry of, 214
Freiberg, epsomite of, 51

galena of, 70

gneiss of, 235, 238

granite-porphyry near, 213

granular- gneiss of, 239

mispickel of, 74

porphyry of, 217, 218

quartz-schist of, 247

serpentine near, 317

wavellite near, 55
Friedrichsroda, in the Thuringian Forest,

porphyry of, 217
Freienhauschen, in the Eifel. trachyte

of, 191

Frejus, blue porphyry of. 171
Fiinfkirchen, coal of, 334

in the Odemvald,
kinzigite of, 320

Gamsigrad, in Servia, timazite of, 156
Gastein, in the Alps, gneiss of, 239

titaniferous iron of. 63

Gata, Cabo de, in Spain, kinzigite of. 320
Gefrees, in the Fichtelgebirge, chiastolite-
schist of, 257

gneiss of. 239

mica-schist near, 243
Germany, alunogen of, 50

amber of, 76

bituminous mar] of, 273
shales of, 77, 338

browncoal clay of, 269

clay-slate of, 264

compact marl of, 272

conglomerate of, 303, 304

disilicate of protoxide of iron of, 346

dolomite of, 289, 290

gypsum of, 293

hornfels of, 350

jasper of, 6

limestones of, 285

peat of, 328

porphyrites of, 169

sandstone of, 299, 300

septarian clay of, 270

Geysers, Iceland, soluble quartz in the, 5
Giant's Causeway, Ireland, analcime of
the, 30

basalt of the, 142

chabasite of the, 31

INDEX OF LOCALITIES.

403

GLA

Glasgow, coal of, 332

Gleichenberg, in Styria, trachyte of, 190

Gloucestershire, Newent sandstone of,
300

Goldberg, iu the Fichtelgebirge, gneiss
of, 239

Golduiiilil, in the Fichtelgebirge, mica-
schist near, 244

Gopfers-Grlin, in the Fichtelgebirge, talc
of, 354

Gb'rgeleu, in Hungary, red hematite of,
343

Goslar, in the Hartz, pyrites of, 358

Gothu, lias sandstone of, 299

Gouverneur, in North America, apatite
of, 53

Greenland, colnmbite of, 46

cryolite of, 69, 353

graphite of, 75

on hit e of, 43

titanite of, 47

Greifenstein, in Saxony, topaz of, 35
Grossenhain, granite-gneiss of, 238
Grosswaltersdorf, near Freiberg, granu-

lite-gneiss of, 239

Guipuscoa, in Spain, glaubersalt of, 51
G umbel, in Bavaria, oltrelite-schist of,

256
Gumuchdagh, in Asia Minor, corundum

of, 351

HAIDA, in Bohemia, phonolite near,
200

Hainersreuth, in the Fichtelgebirge,
porphyry of, 170

Hiiinichen, in Saxony, coal of, 333,
334

Hammond, zircon of, 41

Hampshire, clay of, 270

Hampshire, New, mispickel of, 74

Hanau on the Maine, semi-opal of, 349

Handerloo, near Schemnitz, granitic tra-
chyte of, 184

Hanover, boracite of, 52

Hanover, in North America, hornblende-
schist of, 254

Hanng, in the Tyrol, eocene coals of,
330

Harthau, near Chemnitz, chlorite-schist
of, 250

Hartz Mountains, clay-slate of the, 266

conglomerate of the, 304

diabase of the, 149

fluor-spar of the. 351

galena of the, 70

HUN

Hartz Mountains continued

granitite of the Brocken of the,
207

graphite of the, 75

hausmannite of'the, 64

labradorite, porphyry of the, 160

melaphyre of the, 163, 166

manganite of the, 66

melaphyre of the, 163

porphyrite of the, 170

pyrites of the, 358

schiller-rock of the Baste in the,
316

schiller-spar of the, 19

wernerite rock of the, 222
Haslau, near Eger, egeran of, 318
Hastings, sand of, 299
Heidelberg, granite near, 207

granular limestone near, 278
Herges, in the Thuringian Forest, apha-

nite of, 159
Hermsdorf, in the Erzgebirge, porphyry

of, 218
Herren-Grund, in Hungary, gypsum of,

293

Herrnhut, in Saxony, grannlite of, 231
Hessen, browncoal of, 330

dolerite of, 135

trachyte of, 190
Hinterbriihl, talc-schist of, 252
Hitteroe, in Norway, orthite of, 43

gadolinite of, 43

Hliniker Valley, in Hungary, millstone-
porphyry of, 184

trachyte-porphyry of, 195
Hoboken, New Jersey, chromic iron-ore

of, 62
Hochberg, near Eger, granulite-gneiss

of, 239

Hoch-Eppen, porphyry of, 218
Hof, in the Fichtelgebirge, hornblende-
schist of, 254

mica-schist near, 243

Hbfles, near Eiger, granite-gneiss of,
238

Hbgan, phonolite-tufa of, 309

Hohenelbe, porphyrite near, 170

Hollennmhle, in Saxony, hypersthenite
of, 152

Holstein, boracite of, 52

Huhnberge, in the Thuringim Forest,
diorite of, 155

Huhnerhof, in the Fichtelgebirge, mica-
schist near, 243

Hungary, alunite of, 52, 309

antimony-glance of, 357

D D 2

404

INDEX OF LOCALITIES.

HUN

Hungary continued

basalt of, 187

carbonate of manganese of, 354

coal of, 334

gypsum of. 293 '

millstone -porphyry of, 184

perlite of, 184

natron of, 59

nitre of, 55

oligoclase of, 1 1

opal of, 8, 309

perlite of, 196

pyrites of, 358

red hematite of, 343

rhodonite of, 356

talc-schist of. 252

timazites of, 161

trachyte of, 184, 187, 191

trachyte-porphyry of, 184, 185, 195
Hutberg, near Dresden, hornbleude-por-

phyrite of, 172

TCELAND, apophyllite of, 30
heulandite of, 33

obsidian and pumice-stone of, 197

stilbite of, 33

siliceous tuff of, 349

soluble quartz in the geysers of, 5

trachyte of, 184

trachyte-porphyry of, 195
Idria, epsomite of, 51

Ihlefeld, in the Hartz, hausmannite of,
64

manganite of, 66

Ilfeld, manganese-ores of, 357

melaphyre of, 165

porphyrite of, 1 70

Ilmenau, in Thuringia, braunite near,
64

coal of, 333

ommon felspar of, 10

'lijausmannite of, 64
.manganese-ores of, 357

manganite of, 66

melaphyre near, 164

porphyry near, 219

Ilmensee, near Miask, titaniferous iron

of, 63
Indies, East, hislopite of the, 278

laterite of the, 312

nitre of the, 55

nummulitic limestone of the, 283
Ireland, analcime of, 30

chabasite of, 31

cupriferous sandstone of, 300

KAP

Ireland continued

felspar of, 10

freestone of, 298

fyalite of, 38

garnet of, 40

granite of, 206

granular limestone of, 278

limestone of, 278

phillipsite of, 32

Ischia, trachytic rocks of, 185
Iserlohn, galmey of, 356
Istria, sandstone of, 299
Itabira, in Brazil, itabirite of, 343

moorshead rock of, 343
Itacolumi Mountain, near Villa Rica,

itacolumite of, 248
Italy, alum-stone of, 52, 309

barytes of, 48

gabbro of, 151

gypsum of, 293

marl of, 273

mellilite of, 42

nitre of, 55

sandstone of, 299

trachyte of, 190

travertine of, 282

TAKUBEN, in Bohemia, phonolite of,

J 200

Jena, celestine of, 48

Jersey, New, franklinite of, 357

vivianite of, 54

zircon of, 41
Johanrigeorgenstadtjin Saxony, polianite

of, 65

J7 AISERSTUHL, in Brisgau, granular

-"- limestone of, 278

Kaiserstuhl, in Baden, pyrochlore of,

perofskite at, 45
Kaiserstuhl, sodalite of, 14

trachyte of, 190

Kammerbuhl, in Bohemia, basalt of,

141
Kaintschatka, siliceous tuff of, 349

trachydolerite of, 192

Kandern, on the Schwarzwald, disilicate
of protoxide of iron of, 346

Kansas, nacritide of, 244

Kapnik, in Hungary, carbonite of man-
ganese of, 354

Kappellenberg, trachyte of, 190

IXDEX OF LOCALITIES.

405

KAS

Kasbegk, in the Caucasus, trachyte of,

188

Kaschau, in Hungary, opal of, 309
Katherinenburg, chrysolite of, 39
K it/iiiittf. in tlia Tlmringian Forest,

oilstone of, 265
Kemuath, porphyry near, 218
Kerbersdorf, near Eger, granite of, 205
Killan, in Ireland, garnet of, 40
Killiney Bay, spodumene of, 22
Kilmacolm, ill Renfrewshire, natrolite of,

Kilpatrick Hills, scolecite of the, 33
Kilpatrick, in Dumbartonshire, thoin-

sonite of, 31
Kinzig, in the Black Forest, kinzigite

>f, 320

Kirkcudbright, zircon of, 41
Kleinlinden, manganese-ores of, 357
Klobenstein, in Saxony, garnet rock of

the, 319
Klumpsen Mountain, in Oberlausitz,

diorite of the, 155
Kongbberg, in Norway, analcime of, 30

axinite of, 44

mispickel of, 74

Koi bach, in the Fichtelgebirge, mica-
schist near, 243

Korgon, in the Altai Mountains, porphy-
rite of, 170

Kozelniker Valley, near Schemnitz, tra-
chyte of the, 186

Krageroe, in Norway, phosphorite of,
353

Kremnitz, in Hungary, trachyte of, 184

Kriebstein, dichroite rock near, 320

Kronberg, near Erbendorf, porphyry of,
218

Krummau, in Bohemia, granulite of,
231

Kiinlsbrunnen, in the Siebengebirge, tra-
chyte of, 191

Kusstein, in Tyrol, ostraea limestone of
the, 283

T AACHERSEE, titanite of, 47

L* Lagoda Lake, wernerite of the, 222

Liilni, melaphyre of, 166

Landshut, in Silesia, melaphyre of, 166

Langenstriegis, near Freiberg, wavellite

of, 55
Lauenstein, in the Erzgebirge, gneiss of,

239
Lanrvig, in Norway, zircon-syenite of,

181

LYO

Lauterbach.near Marienberg, granulite-
gneiss of, 239

Lehnau, near Kemnath, porphyry of,
218

Lehsten, in the Thnringian Forest, roof-
ing slate of, 264

Leitha Mountains, conglomerate of the,
303

limestone of the, 282
Lemberg, amber of, 76
Lengefeld, gneiss of, 238
Lenne-Gebiet, in Westphalia, porphyrite

of, 170

Leschtina, Bohemia, basalt of, 141
Leukersdorf, in Saxony, porphyry of,

217
Lherz, Lake, in the Pyrenees, augite

rock of the, 149
Liebenstein, in the Thuringian Forest,

granite- porphyry of, 213
Limoges, kaolin of, 13
Linares, galena of, 70
Liorant, in Cantal, trachyte of, 186
Lipari Islands, perlite of the, 184,

196

obsidian and pumice-stone of the,
197

Lippersdorf. gneiss of, 238

Liscanera, Lsland of, trachydolerite of,
192

Littnitz, in Bohemia, marcasite of, 357

Lizard's Point, Cornwall, saponite of,
26

Llandeilo, flags of, 301

Llandovery, handstone of, 301

Lobau, in Saxony, apatite of, 53

Lobejiin, coal of, 333

Lochwinnock, in Renfrewshire, thorn-
son ite of, 31

Lombardy, trachyte of, 184

trachyte- porphyry of, 195
London, clay of, 270
Lowenherg, melaphyre of, 166
Lb'wenburg, in the Siebengebirge, trachy-
dolerite of the rock of the, 192

Lozere, fraidonite of the, 175
Ludwigstadt, in the Thuringian Forest,

carbonaceous schist of, 258
Ludlow, sandstone of, 301
Lugano, porphyrite near, 170
Luneburg, Hanover, boracite of, 52
Luneville, in France, boracite of, 52
Luschitz, in Bohemia, mellite of, 77
Luxembourg, ottrelite of, 27
Lyons, granite near, 206

malachite near, 60

406

INDEX OP LOCALITIES.

MAG

MAGDEBURG, boracite of, 52
rock-salt near, 352
Magurka, in Hungary, antimony-glance

of, 357
Manebach, in the Thuringian Forest,

porphyry of, 218, 219
Maracaibo, in Peru, trona of, 59
Marebach, aphanite of, 159
Margola, rock of the summit of the, 164
Marianna, in Brazil, moorshead rock of,

343
Marienburg, in Bohemia, granulite-

gneiss of, 239

phonolite of, 200

Marienberg, in Saxony, porphyrite-

wacke of, 171
Markersdorff, in Bohemia, bituminous

substances of, 77
Marmaros, in Hungary, red hematite of,

343
Massachusetts, chabasite of, 31

columbite of, 46

rutile of, 66

titanite of, 47

Matlock, in Derbyshire, smithsonite of,

34
Mautern, near Mblk, granulite-gneiss of,

239
Mayence basin, limestone of the, 282

marl of the, 273

sandstone of the, 299

Megeen, in the Sennethal, barytes of,

352
Meissen, in Saxony, granite of, 207

granular limestone near, 278

hornblende-schist near, 253

mica-porphyrite of, 173

pitchstone of, 225

quartz-porphyry of, 217
M?lfi, haiiynophyry of, 141

leucite of, 186

Menaccan, in Cornwall, titaniferous iron

of, 64

Mendip Hills, smithsonite of, 34
Menil Montant, Paris, menilite found at,

Meronitz, in Bavaria, opal of, 349
Meissner, in Hesse, browncoal of, 330
Messner Mountain, in Hessen, dolerite

of, 135
Mexico, obsidian and pumice-stone of,

197

perlite of, 196

trachyte of, 186
Miask, pyrochlore of, 45

titaniferous iron near, 63

NAS

Miesbach, Molasse coal of, 330

Mileschauer, in Bohemia, phonolite of,
200

Milo Isles, alunogen of, 50

Milsburg, on the Rhon Mountain, pho-
nolite of, 200

Miltitz, near Meissen, granular limestone
of, 278

hornblende-schist of, 253
Mittelgebirge, in Bohemia, basalt of the,

142

phonolite of the, 187, 200

titanite of the, 47

Mittweida, in Saxony, granulite of, 231,

232
Mohorn, near Freiberg, pitchstone-por-

phyry of, 225

porphyry of. 217

Molina, in Aragon, aragonite of, 58
Molk, granulite-gneiss near, 239
Mondhalde, at the Kaiserstuhl, trachyte

of, 190
Monfina, Rocca, leucite of, 186

trachyte doJerite of, 192
Montabaur, in Nassau, trachyte of, 186
Montdore, Auvergne, alunite of, 52
Monte Rosa, granite of, 207
Montmartre, Paris, siliceous concretions

of, 279

Monzoni, pleonaste of, 61
Moravia, lepidolite of, 355
Moritzburg, in Saxony, granite of, 207

granite-gneiss near, 238
Morocco, nummulitic limestone of, 283
Mourne Mountains, Ireland, beryl of, 39

common felspar of, 10

fayalite of, 38

topaz of, 35

Miihlhausen, in Thuringia, peat-beds of,

328

Mulatto, porphyritic rocks of, 170
Miinchberjr, in the Fichtelgebirge, eklo-

gites of the, 318, 319

granulite-gneiss near, 239

hornblende-schist of, 253
Mursinsk, in Siberia, topaz of, 35
Mussa Alp, Piedmont, idocrase of, 41
Muzay, Hungary, alunite of, 52
Muzo, in Columbia, beryl of, 39

NAGYAG, in Transylvania, trachyte
of, 186
Nassau, palagonite of, 19

schal stein of, 310, 311

trachyte of, 186

INDEX OF LOCALITIES.

407

NAT

Natolia, meerschaum of, 354
Naxos, corundum of, 351

emery of, 8

Negroponte, meerschaum of, 354
Neurode, in Silesia, hypersthenite of,
152

troutstone of, 316

Neusohl, trachyte-porphyry of the

Schlossberg ot, 195
Newcastle, coal of, 332
Niedermendiir, on the Rhine, basaltic

lava of, 141

corundum of, 8

haUyneof, 15

Niederschona, near Freiberg, granite-
porphyry of, 213

Nile, jasper in the sand of the, 6

Nischne-Tagilk, in the Ural, dolomite
of, 289

Norway, axinite of, 44

gadolinite of, 43

magnetic ironstone of, 345

mispickel of, 74

norite of, 156 ,

orthite of, 43

phosphorite of, 353

porphyrite of, 1 70

potstone of, 251

pyrochlore of, 45

wohlerite of, 46

zircon of, 41

zircon-syenite of, 181
Nossen, sclialstein near, 311
Nuovo, Monte, leucite of, 185

trachyte of, 190

OBERHASLI, in the Alps, gneiss of,
239

Oberhohndorf, coals of, 333
Oberlausitz, in Bohemia, aphanite of,
161

diorite of, 155

phonolite of, 200

Oberpfalz of Bavaria, apatite of the, 53
Ober-Pobel, near Alteuberg, greisen of,

321
Oberstein, harmotome of, 32

characteristics of amygdaloid of, 166

melapliyre near, 164
Oberweishenthal, in the Erzgebirge,

actinolite-schist of, 254
Ochuenkopf, in the Erzgebirge, corun-
dum of, 351

granite of, 205

talc-schist of, 252

PER

Odenwald, granite of, 207

kinzigite of the, 320

porphyry of the, 2 1 7
Oederan, in Saxony, minette of, 174

porphyry of, 218

Oehrenatock, near llmenau, braunite of,
64

manganite of, 66

Ofen, in Hungary, perlite of, 184
Oisans, St. Gotthard, axinite of, 44
Olibano, Monte, near Pozzuoli, trachyte

of, 190
Orizaba, Mount, in Mexico, trachyte of,

186

Oschatz, bituminous shale of, 338
Osnabruck, anthracite of, 336

PALAGONIA, in Sicily, tufa of, 308

* Pargas, apatite of, 53

crystals of hornblende and pyroxene
disseminated in limestone rocks in
the, 21

Paria, in Italy, gypsum of, 293
Paris, glauconite of, 27

gypsum of, 293

inenilite. 8, 279,349

milistofts of the Paris basin, 350
Paris basin, calcaire grossier of the,

282

plastic clay of the, 270
Partenkirchen, in Bavaria, nodular lime-
stone of, 280

Passau, on the Danube, gneiss of,
239

granite of, 207

graphite of, 336

kaolin of, 14

Pasto, volcano of, alunogen of, 50

trachyte of, 186

Paterno, Monte, near Bologna, barytes

of, 48

Pausilippo tufa, 309
Pelegrin, in Tyrol, porphyry of, 218
Pennig, in Saxony, granulite of, 231

hypersthene of, 19
Pennsylvania, naplitha of, 77
Pentland Hills, near Edinburgh, por-
phyry of the, 170

Perlenhardt, in the Siebengebirge, tra-
chyte of, 185
Persia, naphtha of, 77

nummulitic limestone of, 283

turquoise of, 54
Pern, glauberite of, 49

troiia of, 59

408

INDEX OP LOCALITIES.

PET

Peterhead, spodumene of, 22
Phelegrai, Campi, trachytic rocks of the,

185
Pic Blanc, Monte Rosa chain, granite of

the, 207
Picota Mountain, in Portugal, foyaite of,

181
Picton-nob, in North America, specular

iron of, 343

Piedmont, idocrase of, 41
Pike's Peak, in Kansas, nacrite of,

244

Pinchincha, andesite of, 192
Planitz, in Saxony, burnt shale of, 339

felsite-balls of; 224, 225
Planschwitz, in Saxony, greenstone-tufa

of, 310

Flatten, in Bohemia, polianite of, 65
Plauenschen-Grund, near Dresden, horn-

blende-porphyrite of the, 172

syenite of the, 176, 178, 179
Plombieres, apophyllite of, 30

fluor-spar of, 69

Polwand, near Saalfeld, nodular lime-
stone of, 281

Pontellaria, fibrous trachyte of the,
184

Pont Jean, in the VosgesliMountains,
dioriteof, 156

Ponza Islands, trachyte-porphyry of the,
184, 195

Popayan, trachyte near, 186

Popocatapetl, Mount, trachyte of, 186

Poppenrent, near Miinchberg, granulite-
gneiss of, 239

Potschappel, near Dresden, hornblende-
porphyrite of, 171

Portland, sand of, 299

stone of, 280, 284
Portugal, foyaite of, 181

itacolumite of, 249
Pozzuoli, trachyte near, 1 90
Predazzo, in the Tyrol, chalcopyrite of,

granite of, 207

lievrite of, 37

uralite of, 18

Prese, La, in Upper Italy, gabbro of,
151

Prussia, Rhenish, zircon of, 41

Purace, near Popayan, trachyte of,
186

Pusu, Island of, in the Ladoga Lake,
wernerite of, 222

Puy de Chaumont, near Clermont, tra-
chyte of, 186

ROS

Puy de Dome, domite of the, 184, 188

oligoclase of, 186

trachyte of the, 191
Pyrenees, augite rock of the, 149

QUIMPER, in Brittany, kersanton of,
175
Quito, mud-streams of, 307

RABEN KLIPPEN, in the Hartz,
melaphyre of, 166
Rabenau, in Saxony, gneiss of, 239
Rabertshausen, in Hessen, trachyte of,

190

Radeberg, near Dresden, gneiss of, 238
Radegrube, near Freiberg, gneiss of,

238

Radoboj, in Croatia, sulphur of, 358
Raibl, in Carinthia, smithsonite of, 34
Rathlin, Island of, in Ireland, granular

limestone of, 278

Raubschlb'sschen, near Weinheim, por-
phyry of, 219

Redwitz, in the Fichtelgebirge, gneiss of,
238

granite near, 205

Regenberg, in the Thuringian Forest,

porphyry of, 217, 218
Reiohenbach, in Voigtland, alum-schist

of, 257
Rhine, basaltic lava of the, 141

corundum of the, 8

cypris-slate of the, 266

hauyne of the. 15

itacolumite of the, 249

titanite of the, 47

Rhb'n Mountain, phonolite of, 200
Riccamonfina, in the Albanian Moun-
tains, leucite rock of, 143
Richenstein, in Silesia, leucopyrite of,

Rieden, leucite rock of, 143
Riesengebirge, granitite of the, 207

malakolite of the, 149

Rio Tinto, in Spain, pyrites of, 358
Rocklitz,in the Riesengebirge, malakolite

of, 149
Rome, alunite near, 52

mellilite of, 42

phillipsite near, 32
Rosenau, in Hungary, rhodonite of,

356
Rosswein, in Saxony, gahbro of, 151

granulite of, 231

INDEX OF LOCALITIES.

409

ROT

Rottleberode, in the Hartz, fluor-spar of,

351

Rovigo, near Lugano, porphyrite of, 170
Kozena, in Moravia, lepidolite of, 355
Rumburg, in Bohemia, granite of, 202,

207
Russia, black earth of Southern, 340

cupriferous sandstone of, 300

gypsum of, 293

malachite of, 354

steppe-limestone of, 282

volborthite of, 47

Ruszkberg, in the Banat, coal of, 334

SAAFELD, nodular limestone near,
281

Saalburg, diabase of, 147

Saarbrucken, Bohemia, alum of, 50

Sageritz, near Grossenhain, granite-
gneiss of, 238

Saidhdiutz, in Bohemia, epsomite of, 51

Sainte Marie, in the Vosges, kersanite
of, 176

Salzburg, beryl of, 39

Sau-Alp, in Styria, eklogite of the, 318

SiUtina, diorite of, 155

S ivoy, aphanite of, 159

Saxony, alunogen of, 50

apatite of, 53

basalt of, 140

burnt shale of, 339

chlorite of, 25

coals of, 333

conglomerate of, 303

cordierite of, 44

dichroite-rock of, 320

felsite-balls of, 224

felstone of, 222

ferreo-liihomarge of, 356

jiabbro of, 151

garnet-rock of, 319

gneiss of, 238, 239

granite of, 206, 207

granular limestone of, 277

granulite of, 231

green porphyry of, 214

greenstone-tufa, 310

hornblende-porphynte of, 171, 172

liy}>ersthene of, 19

hypersthenite of, 152

idocrase of, 42

kaolin of, 354

pycnite of, 354

limestone of, 283

magnetic ironstone of, 345

SCH

Saxony continued

marcasite of, 73
"marl of, 273

mica-schist of, 244

mica-porphyrite of, 173

minette of, 174

nodular or spotted schist of, 257

occurrence of emery in, 8

orthite of, 43

polianite of, 65

porphyrite-wacke' of, 171

porphyry of, 217

porphyry-tuff of, 309, 310

pyrope of, 4 1

quartz- porphyry of, 217

sandstone of, 299

schorlaceous schist of, 323

serpentine of, 317

syenite of, 176, 178, 179

topaz of, 35, 36
Scandinavia, limestone of, 286
Schaumberg, tboleite of the, 138
Schellerhau, in the Erzgebirge, granite-
porphyry of, 213

Schemnitz, in Hungary, agalmatolite
near, 354

diorite dL 155

granithffrachyte of, 184

perlit*of, 184, 196

timazifes of, 161

trachyte of, 184, 186

trachyte-porphyry of, 195
Schivelutsch, in Kamtechatka, trachy-

dolerite of the, 192
Schlaggenwald, greisen of the, 321
Schleusenthal, in the Thuringian Forest,

melaphyre of, 1 64
Schlossberg, Saxony, basalt of, 140
Schloitzbachthal, in Saxony, granite of,

206
Schmiedefeld, in the Thuringian Forest,

granite porphyry of, 213

magnetic ironstone of, 345

melaphyre near, 167
Schmollnitz, in Hungary, pyrites of,

358

Schneckenstein, in the Voigtland, topaz
rock of the, 324

Schneeberg, in the Erzgebirge, granite
of, 206

Schneeberg, in the Fichtelgebirge, gra-
nulite-gneiss of the, 239

Schneekopf, in the Thuringian Forest,
porphyry of, 218

Schneidemiillersberg, near Ilmenau, me-
laphyre of, 164

410

INDEX OF LOCALITIES.

SCH

Schonfeld, in the Erzgebirge, anthracite

of, 336
Schwarzbach, in the Fichtelgebirge,

chlorite-schist of, 250
Schwarzenbach, in the Fichtelgebirge,

mica-schist of, 242
Schwarzenberg, in Saxony, garnet-rock

near, 319
Sehwartzenberg, in the Erzgebirge,

gneiss of, 238

talc-schist of, 252
Schwarzenfels, in the Erzgebirge, quartz-
breccia of, 305

Schwarzwald, common quartz in the
sandstone of, 6

disilicate of protoxide of iron of the,
346

Scotland, analcime of, 39

basalt of, 142

cannel or parrot-coal of, 332

carboniferous ironstone, or blacfcband
of, 346

hypersthenite of, 152

laumontite of, 32

natrolite of, 32

phonolite of, 201

porphyry of, 170

prehnite of, 31

sandstone of, 300

thomsonite of, 31

titanite of, 47

Seegeberg, in Holstein, boracite of, 52
Seerenbach, near Tharand, gneiss of, 239
Seisser Alp, analcime of the, 30

inelaphyre of, 163
Servia, timazite of, 156

Shelburne, in Massachusetts, rutile of, 66
Shropshire, stiper stones of, 301
Siberia, epsomite of, 51

malachite of, 60

topaz of, 35
Sicily, analcime of, 30

gypsum of, 293

palagonite of, 19

tufa of, 308, 309
Siebengebirge, trachyte of the, 186, 188,

191

trachydolerite of the, 192
Siebei'.helm,near Freiberg, serpentine of,

317

gabbro of, 151
Siegburg, dolerite of, 135
Siegen, polianite of, 65

Silesia, corundum in the granite of, 8

galena of, 70

hypersthenite of, 152

STE

Silesia continued

leucopyrite of, 73

melaphyre of, 164, 166

native coke or anthracite of, 334

pebbles of, 103

porphyry of, 219

smithsonite of, 34

Silthal in Transylvania, coal of, 334
Skiddaw, in Cumberland, chiastolite-

schist of, 257

Skutsch, in Bohemia, amber of, 76
Skye, Isle of, heulandite of, 33

hypersthene of, 19

hypersthenite of, 152

labradorite of the, 1 1

Slatoust, in the Ural, perofskite of, 45
Solenhofen, in Bavaria, slaty limestone

of, 281
Somma, Monte, anorthite in the lavas

of, 12

leucite rock of, 143, 186

meionite of, 42

spinel of, 61

Sonnenberg, in Bohemia, gneiss of, 238
Sonnerberg, in the Thuringian Forest,

pencil-slate of, 264

Soos, in Bohemia, polishing slate of, 350
Spain, aragouite of. 58

cinnabar of, 358

galena of, 70

glauberite of, 49

glaubersalt of, 51

itac.lumite of. 249

kinzigite of, 320

nitre of, 55

pyrites of, 358
Spechtshausen, in Saxony, felsite-balls

of, 224

pitchstone-porphyry of, 225
Staffa, basalt of, 142

scolecite of, 33
Staffordshire, coals of, 332

peldon of, 298

St. Agnes, Cornwall, vivianite of, 54
Staniren Alf, in Styria, anthracite of,

336
Stassfurt, near Magdeburg, boracite of,

52
St. Austell, Cornwall, common quartz

of, 5

Steindoif, in the Banat, coal of, 334
Steingrun, near Eger, gneiss of, 239
Steinhaide, in the Thuringian Forest,

sandstone of, 297

Stemzelberg, in the Siebengebirge, tra-
chyte of,' 186, 188, 191

INDEX OF LOCALITIES.

411

ST.

St. Gall, pebbles of, 102
St. Gotthard, axinite of, 44

ad ul aria at, 9

corundum of, 8

fluor-spar of, 69

gneiss of, 239

gypsum of, 292, 293

paraeonite-schist of, 244

tourmaline near, 37

St. Loretta, in the Leitha Mountains,

conglomerate of, 303
Stockholm, oligoclase of, 11
Stolpen, basalt near, 140
St. Ouen, Faris, siliceous concretions of,

279
Strassberg, in the Hartz, fluor-spar of,

351
Strassfurt, near Magdeburg, rock-salt

of, 352

boracite of, 353
Stromboli, dolerite of, 137

trachydolerite of, 192
Stroutian, Ar^yleshire, titanite of, 47
St. Stephen's, in Cornwall, kaolin of, 13
Styria, anthracite of, 336

eklogite of, 318

fullers' earth of, 356

graphite of, 75

paragonite of, 58

trachyte of, 190

St. Yiieix, near Limoges, kaolin of,

13
Supgsville, in North America, orbitoidal

limestone of, 283
Sussex, Weald clay of, 270
Swabia, barytes of, 48

celestine of, 48

clays of, 270

dolomite of, 289, 290

marl of, 273, 274

sandstone of, 299
Swarzenbertr, Saxony, idocrase of, 42
Sweden, automolite of, 61

eulisite of, 319

felsite-schist of, 222

hsulandite of, 33

gadolinite of, 43

hypersthenite of, 152

idocrase of, 41

magnetic ironstone of, 345

mica-schist of, 242

porphyrite of, 170

pyrites of, 358

spodumene of, 22

stilbite of, 33

tantalite of, 46

THU

Sweetwater River, Rocky Mountains,
trona of, 59

Switzerland, common quartz in the gra-
nites of, 6

glarus-slate of, 266

gypsum of, 293

sandstone of, 299

staurotide of, 36

Syra, island of, eklogite of the, 318

TABARZ, in the Thuringian Forest,
aphanite of, 159

Takli, in the East Indies, hislopite of,
278

Tannebergsthal, in the Erzgebirge, por-
phyry of, 217

Tarapaca, in Peru, glauberite of, 49

Tarnowitz, in Silesia, galena of, 70

galmey of, 356

smithsonite of, 34

Taunus, sericite-schist of the, 256
Telkebanya, in Hungary, perlite of, 184

perlite of, 196

Teneriffe, peak of, obsidian and pumice-
stone of the, 197

trachydolerite of, 192

trachyte of the, 186, 188

tufa of, 309

Ternuay, in the Vosges, aphanite of,

160

Test-hen, variety of diabase of, 148
Tet.schen, in Bohemia, phonolite, near,

200
Teufelsstein, in Saxony, garnet- rock of

the, 319
Tharand, in Saxony, felsite-balls near,

224

felstone near, 222

gneiss of, 239

granite near, 206

marcasite of, 73

quartz-porphyry of, 217
Thibet, borax of, 53

Thuringian Forest, aphanite of the, 159

carbonaceous schist of the, 257

conglomerate of the, 303, 304

diorite of the, 155

dolomite of the, 290

dolomitic sand of the, 290

granite-porphyry of the, 207, 213

hau.smannite of the, 64

kaolin-sandstone of the,297

magnetic iron-stone of the, 345

manganite of the. 66

marl of ihe, 274

412

INDEX OP LOCALITIES.

THU

Thuringiah Forest continued

melaphyre of the, 163, 164

mellite of the, 77

miacytan clay of the, 270

mica-porphyrite of the, 173

oilstone of the, 265

peat-beds of the, 328

pencil-slate of the, 264

porous limestone of the, 281

porphyries of the, 217, 218, 219

quartz-porphyry of the, 217

quartz-porphyries and mica-porphy-
ries of the, 187

roofing-slate of the, 264

shale of the, 267

white or grey sandstone of the, 300
Tokay, in Hungary, perlite of, 196

trachyte of, 184

Tolfa, La, Italy, alum-stone of, 309,
352

trachyte of, 184

trachytic rocks of, 185

Tolima, in South America, trachyte of,

186
Toluca, Mount, in Mexico, trachyte of,

186

Tolz, Molasse coal of, 330
Totnn Fjeld, in Norway, orthite of,

43
Transylvania, coal of, 334

porphyry of, 219 * _

pyrites of, 358

sandstone of, 296

syenite of, 179

trachyte of, 186, 191

wohlerite of, 46

Trebendorf, near Eger, granite of, 205
Treyalgan, Cornwall, tourmaline of, 38
Triebisch Thai, near Meissen, pitch-
stone of the, 225
Trinidad, asphalte of, 77

bitumen of, 337

Trostburg, in Tyrol, porphyry of, 218
Tumilla, apatite of, 53
Tunaberg, in Sweden, eulisite of, 319
Tunguragua, in South America, tra-
chyte of, 186

Turkey, nephrite and jade of, 18
Tuscany, trachyte of, 184
Tyrol, amphilogite-schist of the, 244

chalcopyrite of the, 74

crystals of hornblende and pyroxene
disseminated in the limestone rocks
in the, 21

eocene coals of the, 330

granite of the, 207

VIT

Tyrol continued

granitite of the, 207

hypersthene in the, 19

lievrite of the, 37

melaphyre of the, 164

oligoclase of the, 11

ostrsea limestone of the, 283

porphyrites of the, 1 69

porphyritic rocks of the, 170

porphyritic syenite of the, 178
porphyry of the, 218

predazzite of the, 289
staurotide of the, 36

tonalite of the, 207

tufas of the, 310

TTNITED STATES,alunogenof the, 50
U Unst, Island of, chromic iron-ore of

the, 62
Ural Mountains, beresite of the, 207

dolomite of the, 289

itacolumite of the, 249

miascite of the, 180

oligoclase- porphyry of the, 160

perofskite of the, 45

talc-schist of the, 252

zircon of the, 41

Uto, in Sweden, apophyllite of, 30

spodumene of, 22

yALENCIA, in Aragon, aragonite of,

Velay, trachyte of, 184

Vesuvius, garnet in the lavas of, 40

hematite of, 63

idocrase in old lavas of^ 41

leucite of, 186

leucite rock of, 143

magnetic pyrites in the lavas of,
72

natron of, 59

thomsonite in the lavas of, 31
Vienna basin, tile- or brick-earth of the,

269

Vienna-sand, 299
Viesembach, in the Vosges Mountains,

kersanite of, 176
Villa Rica, itacolumite of, 248

moorshead rock of, 343

Villa Rubia, in Spain, glauberite of,

49
Visena Valley, in Tyrol, porphyritic

syenite of the, 178
Viterbo, trachyte of, 184

INDEX OF LOCALITIES.

413

VOI

Voigtland, chiastolite-schist of, 257

alum-schist of. 257

diabase of, 1 49

granite-gneiss of, 238

topaz rock of. 324

Volturara, near Melfi, haiiyne, of, 15
Vosges, andesine of the, 1 1

apatite of the, 1 60

conglomerate of the, 303

diorite of the, 156

mica-diorite of the, 179

niinette of the, 173

kereanite of the, 176

sandstone of the, 300

Vulture, near Melfi, haiiynopbyry of,
141

extinct volcano of, leucite of the,
186

WACHENBERG, in the Odenwald,
porphyry of, 217
Waldenberg, in Silesia, porphyry of, 219

native coke or anthracite of, 334

pebbles of, 103

Waldheim, in Saxony, serpentine of, 317
Waldshut, fluor-spar of, 69
Wales, oilstone of, 265

roofing and pencil-slate of, 264
Walkberg, in Bohemia, basalt of, 141
Walpenruth, in the Fichtelgebirge, mica-
schist near, 243

Warwick, in America, rntile of, 66
Wechselburg, in Saxony, gneiss of, 239

nodular or spotted schist of, 257
Weigmannsdorf, in Saxony, gneiss of,

238

Weinheim, porphyry near, 219

Weisig, near Dresden, hornblende-por-
phjrite of, 172

Weissenborn, gneiss of, 238

Weissenfels, in Thuringia, kaolin-sand-
stone of, 297

Weissritzthal, in Saxony, minette of the,
174

Wenlock, sandstone of, 301

Weser Mountains, bituminous shale of
the, 338

Weslau, near Redwitz, granite of, 205

Westmoreland, limestone of, 285

Westphalia, conelomerate of, 303

Hils clay of, 270

Hils sandstone of, 299

marl if, 273

porphyrite of, 170

serpulite limestone of, 284

ZOB

Wettin, coals of, 333

Weiford, garnet of, 40

Whitby, dogger sandstone of, 299

Wicklow, freestone of, 298

Wiegersdorff, black melaphyre of, 166

Wiener Neustadt, granulite of the

Glocknitzer Schossberg at, 231
Wiersberg, in the Fichtelgebirge, chlo-

rite-schist of. 250
Wight, I.sle of, glauconite of the, 27
Wilsdruff, in Saxony, hornblende-por-

phyriteof, 171
Winterstein, in the Tlmringian Forest,

quartz-porphyry of, 217
Wittichen, in the Black Forest, kinzigite

of, 320

Wolkenburg, in the Siebengebirge, tra-
chyte of, 186. 188, 191
Wiirtemburg, bituminous shale of, 338
Wurzen, in Saxony, green porphyry of,

214

yORK, New, rutile of, 66
-*- Yorkshire, amber on the coast of,
76

dogger sandstone of, 299

dolomite of, 299

7AWHAUS, in Saxony, anthracite of,
fl 336

granular limestone of, 277

in the Erzgebirge, mica-schist near,
244

Zbirow, in Bohemia, wavellite of, 55
Zealand, New, nephrite and jade of, 18

olivine of, 39

siliceous tuff of, 349

Zebernick, in Hungary, talc-schist of,
252

Zell, in the Fichtelgebirge, serpentine of,
317

Zelle, near Nossen, schalstein of, 311

Zermatt, perofskite of, 45

Ziegenrucken, near Hohenelbe, porphy-
rite of, 170

Zillerthal, in the Tyrol, amphilogite-
schist of 244

apatite of. 53

Zimpan, in Mexico, perlite of, 196
Zinnwald, in the Erzgebirge, greisen of

the, 321

Zittau, in Saxony, burnt shale of, 339
Zoblitz, in the Erzgebirge, serpentine of,

317

414

INDEX OF LOCALITIES.

zsc

Zschopau, the, in Saxony, granulite of,

231

Zweibrucken, harmotome of, 32
Zwickau, in Saxony, burnt shale of,

339
coals of, 333

ZWI

Zwickau continued

felsite balls of, 224, 225

ferreo-lithomarge of, 356

mica-porphyrite of, 173

porphyry of, 218

pycnite of, 354

GENERAL INDEX.

ACI

4CIDIC rocks, 128
ft- Actinolite, characteristics and oc-
currence of, 17
classy, 17
Adularia, characteristics and occurrence

of, 9, 2C3, 207
Agalmatolite, or figure-stone, occurrence

of, 354
Agate, characteristics and occurrence of,

6,351
Alabaster, characteristics and occurrence

of, 49

Albine. See Apophyllite, 30
Albite, characteristics and occurrence

of, 10
Allanite, characteristics and occurrence

of. 43

Allogovite, 142
A hi iand hie. 40
Alpinite, 239
Alum, characteristics and occurrence of,

Aluminum, oxides of, 5
Alum-schist, 257
Alumstone, 51, 309, 352
Alunite, characteristics and occurrence

of, 51, 352
Alunogen, characteristics and occurrence

of, 50
Amber, characteristics and occurrence

of, 76
Amethyst, colouring matter of, 6

occurrence of, 350
Amphibole. See Hornblende, 16
Amphilogite-schist, 244
Amygdaloid, the term explained, 97

of Oberstein described, 166
Analcime, characteristics and occurrence

of, 29

Analcymite, 138
Auamesite, 134
Andalusite section of minerals,'34

characteristics and occurrence of, 34
Andesine, composition and occurrence

of, 11

BAR

Andesite, 185, 191

Anhydrite, characteristics and occur-
rence of, 48, 290, 293

Ankerite, characteristics and occurrence
of, 57, 355

Anorthite, characteristics and occur-
rence of, 12

Anthracite, characteristics and occur-
rence of, 335

Anthraconite, 277

Antimony-glance, occurrence of, 357

Apatite, characteristics and occurrence
of, 53

Aphanite, characteristics and occurrence
of, 157

varieties in texture of, 158

in composition of, 159

Aplite, or semi-granite, 207

Aplome garnet, 40

Apophyllite, characteristics and occur-
rence of, 30

Aragonite, characteristics and occur-
rence of, 58, 353

Arenaceous, the term explained, 97

Argillaceous fonnationsof rocks,! 1 5, 263

Arsenical pyrites, 357

Arseniurets, 69

Arsenopyrite, characteristics and occur-
rence of, 73

Asbestus, occurrence of, 18

Asphalte, characteristics of, 76

localities of, 77

Augite section of minerals, 16

characteristics and occurrence of, 19,
148

Automolite, 60

Axinite, characteristics and occurrence
of, 43

T) AGSHOT sand, 299

-D Baryt-harmotome, characteristics

and occurrence of, 32
Barytes, characteristics and occurrence

of 47, 352

416

GENERAL INDEX.

BAS

Basalt, characteristics of, 138

varieties in texture of, 140

in composition of, 141

Basaltic rocks, characteristics of, 132
Basic rocks, 128

composition of, 129

Bath-stone, 280

Bedding of rocks, 108

Beresite, 207

Beryl, characteristics and occurrence of,

39
Biotite, characteristics and occurrence

of, 23

Bitter-spar, characteristics of, 57
Bitumen and mineral pitch, character-
istics and occurrence of, 76, 337
Bituminous shale, 338
Blende, characteristics and occurrence

of, 70
Bog, 327
Bog-ore, 342
Bole, occurrence of, 355
Bologna-spar, or Bologna-stone, 48
Boracite, characteristics and occurrence

of, 52, 353
B orates, 52
Borax, characteristics and occurrence

of, 52

Boulders, formation of, 102, 304
Braunite, characteristics and occurrence

of, 64

Braunstein, 64
Breccia, the term explained, 97

characteristics and occurrence of,
304, 308

geological varieties of, 305
Breunnerite, characteristics of, 57
Browncoal, or lignite, characteristics

and occurrence of, 329

varieties of, 329
Brown-spar, characteristics of, 57

C\ AEN stone, 280

^ Calaite, characteristics and occur-
rence of, 54

Calarnine, 58

Calamite, characteristics and occurrence
of, 17

Calcareous spar, 57

Calciphyre, 278

Calcite, 57

Calcspar, characteristics and occurrence
of, 57

Cannel coal, 332

Carbonaceous group, 324

CLA

Carbonaceous group continued

varieties of composition, 324 f

review of the important coal or-

mations, 326
Carbonates, 56

anhydrous, 56

hydrous, 59
Carlsbad twins, 10

Cassiterite, characteristics and occur-
rence of, 65

Celestine, characteristics and occurrence
of, 48

Cerine, characteristics and occurrence
of, 43

Cerusite, 70

Ceylonite, characteristics and occur-
rence of, 60

Chabasite, characteristics and occur-
rence of, 30

Chalcedony, composition of, 6

Chalcopyrite, characteristics and occur-
rence of, 74

Chalk, red, 62

black, 257

white, 280

glauconitic, 280

upper and lower, 283
Chert, characteristics of, 7, 350

formation of, 350

black, 350

Chiastolite, characteristics and occur-
rence of, 34

Chiastolite-schist, 256

Chlorides, 67

Chlorite, characteristics and occurrence
of, 24

Chlorite-schist, and potstone, character-
istics and occurrence of, 250

varieties of, 250

Chromic iron-ore, characteristics and
occurrence of, 62

Chromite, 62

Chrysolite, characteristics and occur-
rence of, 38

Cinnabar, characteristics and occurrence
of, 71, 358

Cipollmo, 277

Clay, characteristics and occurrence of,
269

varieties and composition, 269

geological terms for certain clays, 269
Clay-ironstone, 58

Clay-slate, characteristics and occur-
rence of, 263

varieties in texture of, 264

varieties in composition of, 265

GENERAL INDEX.

417

CLA

Clay -slate continued

geological varieties of, 266
Clays, occurrence of, 14

burnt, characteristics and occurrence
of, 338

varieties of, 339

Claystone and hardened clay, character-
istics and occurrence of, 270
Clink.^tone, 198
Clinochlore, 25
Coal formations, 117

common, black coal, pit-coal, cha-
racteristics and occurrence of, 331

varieties of, 332
Colophonite, 40
Columbates, 45

Coluinbite, characteristics and occur-
rence of, 46

Comptonite, characteristics and occur-
rence of, 31

Cone-in-cone, 99

Conglomerate, the term explained, 97

formations, 1 1 6, 302

characteristics and occurrence of,
302

Copper-ore, blue, 60

Copper-pyrites, characteristics and oc-
currence of, 74

Coprolite beds, composition and occur-
rence of, 340

Coral rag, 284

reefs, 282
Cordierite, 44
Cornbrash, 284

Corundum, characteristics and occur-
rence of, 8, 351

Crichtonite, characteristics and occur-
rence of, 63

Cryolite, characteristics and occurrence
of, 69, 353

T\AMOURITE, character of, 23

Davyne, characteristics and occur-
rence of, 16

Delessite, 25

Dendrites, formation of, 100

Desinine, characteristics and occurrence
of, 33

Diabase, characteristics and occurrence
of, 146

varieties in texture of, 147

in composition of, 148
Diallage, composition of, 19

rock, 150

Diallogite, occurrence of, 354

EUR

Diamond, 336

Dichroite, characteristics and occur-
rence of, 44

rock, characteristics and occurrence
of, 320

Diopside, characteristics of. 18
Diorite, characteristics and occurrence
of, 153

varieties in texture of, 155
Disthene, characteristics and occurrence

of, 36, 318
Dolerine, 252
Dolerite, characteristics of, 134

analysis of, 135

varieties in texture of, 136

variety in composition of, 136
sub varieties ot texture of, 137

Dolomite, characteristics and compo-
sition of, 57, 274, 287

varieties in texture of, 288
in composition of, 289

geological varieties of, 289
Dnnite, 39

Dyke, the term explained, 108

"pAGLE-stone, 295
*-* Earth, black, composition and oc-
currence of, 340
fullers', 355
- yellow, 356
Egeran, characteristics and occurrence

of, 41
Eklogite, characteristics and occurrence

of, 318
Elsoolite, characteristics and occurrence

of, 16

Elaterite, 77
Elements, native, 74
Elvanite, 214
Emerald, characteristics and occurrence

of, 39

Emery, occurrence of, 8
Epidosite, occurrence of, 35, 355
Epidote, characteristics and occurrence

of, 42

Epsom salt, 51
Epsom ite, characteristics and occurrence

of, 51

Erratic blocks, 304
Esbonite, 40
Eukrite, 148
Eulisite, characteristics and occurrence

of, 319

Euphotide, 151
Eurite, 220

418

GENERAL INDEX.

FAH

TUHLUNITE, occurrence of, 44

Felsite rock, 220
Felsite-schist, 220
Felspar, characteristics of, 8

orthoclastic, 9

varieties of colour and lustre, 9

plagioclastic, 10

some aids for distinguishing the
felspar species, 12

Felspar-porphyry, 169
Felstone, characteristics and occurrence
of, 220

varieties of, 222
Ferreo-lithomarge, 356
Figure-stone, 354

Flint, colouring matter of, 6

where found, 6

chalk-flints, 283

Fluor, Fluor-spar, characteristics and
occurrence of, 68, 351

Fluorides, 67

Foyaite, characteristics and occurrence
of, 181

Fragmental rocks, 294

Fraidronite, characteristics and occur-
rence of, 174, 175

Fullers' earth, composition and occur-
rence of, 355

Fyalite, 38

p ABBRO, composition of, 150
^J varieties in composition of, 1 50
Gadolinite, characteristics and occur-
rence of, 43
Gahnite, 60
Galena, characteristics and occurrence

of, 69, 357
Galmey, 33, 58

composition and occurrence of, 356
Garnet section of minerals, 38

characteristics and occurrence of,
39

varieties, 40

Garnet rock, characteristics and occur-
rence of, 319

Glaciers, formation of, 348

Glauberite, characteristics and occur-
rence of, 49

Glaubersalt, characteristics and occur-
rence of, 51

Glauconite, characteristics and occur-
rence of, 27

Gneiss, characteristics and occurrence
of, 232

varieties of, 234

HEM

Gneiss continued

varieties in texture of, 238

in composition of, 239

Gneissite, 234

Gb'thite, 67

Grammatite, characteristics and occur-
rence of, 17
Granite, characteristics of, 203

varieties in texture of, 205

occurrence of, 208

proposed new division of, 209
Granitic porphyry and syenitic por-
phyry, 212

characteristics and occurrence of, 2 1 2
Granitite, 207

Granitone, 150

Granulite, Leptynite, characteristics and
occurrence of, 229

varieties in texture of, 231
Graphite, characteristics and occurrence

of, 75, 336

Gravel, formation of, 102
Green earth, occurrence of, 19
Greenovite, 47
Greenstones, characteristics, varieties,

and occurrence of, 145
Greisen, essential ingredient of, 23

as a variety of granite, 207

characteristics and occurrence of, 32 1
Gritstone, 295

Grossularite, 40

Guano, composition and occurrence of,

339
Gypsum, characteristics and occurrence

of, 49, 274, 290

varieties in texture and compo-
sition of, 291

TTALLEFLINTA, 220, 222.

-*--* Halunogen. characteristics and oc-
currence of, 50

Harmotome, characteristics and occur-
rence of, 32

Hastings sand, 299

Hausmannite, characteristics and oc-
currence of, 64

Haiiyne, characteristics and occurrence
of, 15

Hatty nophyry, 141

Hematite, characteristics and occurrence
of, 62

brown, 67, 341

varieties in texture of, 341

in composition of, 342

red, 342

GENERAL INDEX.

419

HEM

Hematite continued

red, varieties in texture and compo-
sition, 343

Hemitrene, 278

Heulandite, characteristics and occur-
rence of, 33

Hislopite, 278

Hohlspath, characteristics and occur-
rence of, 34

Hone, 265

Honey-stone, 17

Hornblende, characteristics and occur-
rence of, 16, 17

varieties of, 16

differences between hornblende and
pyroxene, 20

Horublende-porphyrite, 171
Hornblende-schist, and Hornblende-rock,
characters and occurrence of, 253

varieties in texture of, 253

variety in composition of, 254
Hornstone, characteristics of, 7, 350

occurrence of, 350

Hyacinth, characteristics and occurrence
of, 41

Hyalite, colourless, where found, 8

Hypersthene, characteristics and occur-
rence of, 19

Hyperstheuite, composition of, 152

TCE, as a rock, formation of, 347
-*- glaciers, 348
underground ice-strata of Siberia,349
Ichthyophthalmite, characteristics and

occurrence of, 30
Idocrase, characteristics and occurrence

of, 41
Igneous rocks, 127

composition of, 129

varieties of, 129

basic, 131

volcanic, 131

plutonic, 144, 201

acidic, 182

volcanic, 182

observations on the processes of

igneous rock-formation, 361
Ilmenite, characteristics and occurrence

of, 63
Ilvaite, characteristics and occurrence

of, 36, 356
lolite, characteristics and occurrence of,

Iron-earth, blue, characteristics and oc-
currence of, 54

LAS

Iron, spathic, 57, 345

oxydulated, 61

specular, 62, 344

red, 62

fibrous, 62

scaly, 62

froth, 62

micaceous, 62

titaniferous, 63

pyrites, 72
white, 72

hydrous, 72

disilicate of protoxide of iron, 346
Iron-ore, sparry, 57

magnetic, 61, 344

red, 62

titanic, 63

brown, 67

Iron-stone group of rocks, 340

geological varieties of, 340, 341
Itabirite, 343

Itacolumite, characteristics and occur-
rence of, 247

varieties of, 248

JASPER, characteristics and occur-

J rence of, 6, 351

Jenite, characteristics and occurrence of,

Jointed structure of rocks, 103
Jointing, various kinds of, 103-105

KAOLIN, characteristics and occur-
rence of, 18, 354

Karren, or Earrenfelder, 101

Karstenite, characteristics and occur-
rence of, 48

Kersantite, characteristics and occur-
rence of, 175

Kersanton, characteristics and occur-
rence of, 175

Killinite, composition of, 22

Kinzigite, characteristics and occurrence
of, 320

Kyanite, characteristics and occurrence
of, 36

T ABRADORITE, characteristics and

" occurrence of, 1 1

Lapis lazuli, characteristics and occur-
rence of, 15

Lasionite, characteristics and occurrence
of, 54

E S 2

420

GENERAL INDEX.

LAS

Lasurite, characteristics and occurrence
of, 60

Laumontite (Laumonite), characteristics
and occurrence of, 32

Lava, the term explained, 96

Lead-ore, blue, characteristics and oc-
rence of, 69

Lepidolite, characteristics and occur-
rence of, 23, 355

Leucite, characteristics and occurrence
of, 15. 142

varieties in texture of, 143
Leucopyrite, characteristics and occur-
rence of, 73

Liebnerite, occurrence of, 44

Lievrite, or Ilvaite, characteristics and
occurrence of, 36, 356

Lignite, 329

Lime-mesotype, characteristics and oc-
currence of, 33

Limestone formations, 116, 274

characteristics and occurrence of,
276

varieties in texture of, 277

geological varieties of, 282
Limonite, characteristics and occurrence

of, 67

Listwenite, 252

Lithia-mica, characteristics and occur-
rence of, 23, 355

Lithionite, characteristics and occur-
rence of, 23, 355

Lithomarge, occurrence of, 355

Loam, 269

Lode, the term explained, 108

Lydian stone, Lydite, black chert, com-
position and occurrence of, 350

MAGNESIA - MICA, characteristics

"- and occurrence of, 23

Magnesite, characteristics and occur-
rence of, 57, 355

Magnetic iron-ore, Magnetite, character-
istics and occurrence of, 61, 344

varieties in texture and compo-
sition of, 344

Magnetic pyrites, characteristics and
occurrence of, 71

Magnetite, 61

Majolica, 283

Malachite, characteristics and occur-
rence of, 59, 354

Malakolite, occurrence of, 19, 149

Manganese-ores, occurrence of, 356

Manganese-spar, occurrence of, 356

MIN

Manganite, characteristics and occur-
rence of, 66

Marcasite, or hydrous pyrites, character-
istics and occurrence of, 72

Margarodite, characteristics of, 23

Marl formations, 116, 271

Marl, characteristics and occurrence of,
272

varieties in texture and composition
of, 272

Marlstone, 272, 274

Meerschaum, characteristics and occur-
rence of, 28, 354

Meionite, 42

Melanite, 40

Melaphyre, characteristics and occur-
rence of, 162

Mellilite, 42, 77

Mellite, characteristics and occurrence
of, 77

Melinite, occurrence of, 356

Menilite, 349

Menachine-ore, 46

Mesitine-spar, characteristics of, 57

Miarolite, 206

Miascite, characteristics and occurrence
of, 180

Mica section of minerals, characteristics
of, 22

binaxial mica, 22

hexagonal or uniaxial, 23
Mica-diorite, 157, 179
Mica-porphyrite, or Micaceous Porphyry,

172

Mica-schist, characteristics and occur-
rence of, 241

varieties in texture and composition
of, 243

Mica-schist, argillaceous, characteristics
and occurrence of, 254

varieties in texture of, 255

in composition of, 256

Mica-trap rocks, 173

Mica-trap, characteristics and occur-
rence of, 174

Microcline, characteristics and occur-
rence of, 9

Mimetisite, 70

Minerals, 1

the principal minerals, 2

the accessory ingredients of rocks, 2

' Paragenesis ' of minerals, 3

mode of classification adopted, 3

chemical symbols used, 4

minerals as rocks, 347

mineral veins and veins of ore, 392

GENERAL INDEX.

421

MIN

Minette, characteristics and occurrence
of, 174

Mirabilite, characteristics and occurrence
of, 51

Mispickel, characteristics and occurrence
of, 73

Mnja, 307

Moorshead rock, 343

Mountain leatlier, 18

Muriacite, characteristics and occur-
rence of, 48

Muscovite. See Potash-mica

VTACRITIDE, 244

-L' Naphtha, characteristics and occur-
rence of, 76
Natrolite, characteristics and occurrence

of, 31
Natron, characteristics and occurrence

of, 59
Nepheline, characteristics and occurrence

of, 1 6
Nephrite, characteristics and occurrence

of, 18
NeVe, 348
Nigrine, characteristics and occurrence

of, 64
Niobite, characteristics and occurrence

of, 46

Nitrates, 55
Nitratine, characteristics and occurrence

of, 55
Nitre, characteristics and occurrence of,

Xorite, characteristics of, 151, 156
Nosean, characteristics and occurrence

of, 15

Nosean-melanite rock, 144
Xovaculite, 267

ABSIDIAN, pure, 185

characteristics and occurrence of,
197

varieties, according to differences of
texture, 197

Ochre, yellow, 341

red, 343
Oilstone, 267

OLgoclase, characteristics and occur-
rence of, 1 1

Oligoclase-dolerite, 138

Olivine, characteristics and occurrence
of, 38

Omphacite rock, 318

PHA

Omphazite, characteristics of, 19
Oolite, formation of, 94

varieties of oolites, 284
Oosite, occurrence of, 44
Opal, characteristics of, 7, 349

occurrences and mode of formation of,
7, 349

varieties of, 349
Ophicalcite, 278
Ophiolite, 314
Ophite, 156

Organic compounds, 76

Ortliite, characteristics and occurrence
of, 43

Orthoclase, characteristics and occur-
rence of, 9, 355

varieties of colour and lustre of, 9
Ottrelite, characteristics and occurrence

of, 26

Ottrelite-schist, 256
Oxides of elements of the hydrogen

group, 60

anhydrous, 60

hydrous, 66
Oxydulated iron, 61
Oxygen compounds, 5

TJALAGONITE, occurrence of, 19
-*- ' Paragenesis ' of minerals, 3
Paragonite-schist, 244
Parrot-coal, 332
Paulite. See Hypersthene
Pea.ore, 341
Peastone, 282

Peat, characteristics and occurrence of,
324, 327

varieties of, 328

Pebbles, formation of, 102, 304

Pegmatite, 206

Pegmatolite, characters and occurrence

of, 9

Peperino, 308
Pencil-slate, 264
Pennine, 25
Peridot, characteristics and occurrence

of, 38
Perlites, and Pearlstone-porphyry, 184

characteristics and occurrence of,
196

varieties in texture of, 196
Perofskite, characteristics and occur-
rence of, 45

Petrosilex, 220

Phacolite, characteristics and occurrence
of, 30

422

GENERAL INDEX.

PHE

Phenakite, or Phenacite, characteristics
and occurrence of, 39

Phengite. See Potash-mica

Phillipsite, characteristics and occur-
rence of, 32

Phlogopite, 24

Pholades, on the sea-coast, 102

Phonolite group of rocks, 198

Phonolite, Clinkstone, characteristics
and occurrence of, 198

varieties in texture of, 200
Phosphates, 53

anhydrous, 53

hydrous, 54

Phosphorite, characteristics and occur-
rence of, 53, 353

Finite, occurrence of, 44

Pinsill, or Pencil-slate, 264

Pistacite in hornblendic and pyroxenic
rocks, 20

characteristics and occurrence of, 42,
355

Pitchstone and Pitchstone-porphyry, cha-
racteristics and occurrence of, 223

varieties in texture of, 225
Pleonaste, 60

Plumbago, characteristics and occurrence
of, 75, 336

Plutonic rocks, 111, 113, 114, 128

Polianite, characteristics and occurrence
of, 64

Porcelain clay, 13, 354

Porphyrite, characteristics and occur-
rence of, 1 68

Porphyrites, 168

Porphyry, 96

Portland-stone, 280, 284

Pot-holes, formation of, 101

Potash-mica, characteristics and occur-
rence of, 22

damourite, margarodite, 23
Potstone, characteristics and occurrence

of, 251

Prehnite, characteristics and occurrence
of, 31

Protogine, 206

Psilomelane, characteristics and occur-
rence of, 67

Puddingstone, 302, 304

Pumice-stone, and its varieties, 97, 185,
197

Puzzulana, 308

Pycnite, occurrence of, 35, 355

Pyrites, characteristics and occurrence
of, 72, 357

in hornblendic and pyroxenic rocks
20

ROC

Pyrites continued

magnetic, 71
white, 73

hydrous, 72, 357

arsenical, 357

Pyroohlore, characteristics and occur-
rence of, 45

Pyromeride, or Ball-porphyry, 218

Pyromorphite, 70

Pyrope, characteristics and occurrence
of, 40

Pyroschist, 338

Pyrolusite, 65

Pyroxene, characteristics and occurrence
of, 18

varieties of, 18

appendix to, 19

hydrous products of the decomposi-
tion of, 19

differences between hornblende and
pyroxene, 20

QUARTZ, characteristics of, 5, 350
common quartz, how found, 5, 350

amethyst, 6, 350

chalcedony, 6

agate, 6, 350

jasper, 6, 350

flint, 6, 350

chert, hornstone, 7, 350

modes of formation of quartz, 7, 350
Quartz-porphyry, Elvanite, characteris-
tics and occurrence of, 215

varieties in texture of, 217

in composition of, 218

Quartz-schist, characteristics and com-
position of, 246

varieties in texture of, 247

RAINDROPS, traces of, on rocks, 101
Randanite, 350
Reddle, 62
Rennsellaerite, 316
Resins, 76

Rhodonite, occurrence of, 356
Rhoetizite, characteristics and occurrence

of, 36
Rbyolite, characteristics and occurrence

of, 193
Ripidolite, characteristics and occurrence

of, 24
Rock-salt, characteristics and occurrence

of, 67, 351

formations, 117

varieties of, 352

GENERAL INDEX.

423

ROC

Rock-soap, occurrence of, 355
Rocks, acidic, analyses of, 85

basic, analyses of, 86

composite, 1

igneous, 127

metamorphic, 227

plutonic, 144, 201

sedimentary, 1 1 5
analyses of, 86

volcanic, 131,182

simple, 1

accessory or non-essential, 1

analyses of, 78

microscopic, 78

magnetic, 78

chemical, 79

physical structure of, 87

texture of, 87

peculiar states of rocks, 95

concretionary structure of, 98

special forms of external structure
of, 99

jointed structure of, 1 03

stratification of rocks, 105

shape and bedding of rock masses,
106

geological formations and groups of
rocks, 111

volcanic, 111

the older, 112

upper plutonic, 1 1 3

lower plutonic, 114

argillaceous, 115

marl formations, 116

limestone formations, 116

sandstone formations, 116

conglomerate formations, 116

coal formations, 117

rock-salt formations, 117

crystalline schist formations,

118

great geological periods of de-
posit, 119

transitions and transmutations of
rocks, 120

classification of rocks, 123

rocks of special character or bedding,
313

observations on the processes of rock-
formation in nature, 359

Roofing-slate, 264
Rottenstone, 279

Rounded stones, formation of, 202
Rubellan, 24

Rutile, characteristics and occurrence of,
66

SED

AL- AMMONIAC, characteristics and
occurrence of, 68

Sahlite, characteristics and occurrence of,
18, 19

Salt, common, characteristics and oc-
currence of, 67, 351

rock, 67

Saltpetre, characteristics and occurrence
of, 55

Chili saltpetre, 55
Sand, varieties of, 299

characteristics and occurrence of f
301

Sandstone, the term explained, 97

formations, 116

characteristics and occurrence of,
295

varieties in texture, 295

in composition, 297

geological varieties of, 298

San id inc. characteristics and occurrence
of, /d

Saponite, characteristics and occurrence
of, 25

Saussurite Qade\ characteristics of,
11

Scaglia, 283

Scapoiite, characteristics and occurrence
of, 41

Schalstein, characteristics and occur-
rence of, 311

varieties of, 311
Schiller-rock, 314

Schist, the term explained, 97
Schists, metamorphic crystalline, 227

composition of, 227

properties of, 228

schorlaceous schist, 323

observations on the processes of for-
mation of metamorphic crystalline
schists, 378

contrasts between the catogenic and
anogenlc transmutations of, 391

Schorl, characteristics and occurrence
of, 37, 323

varieties in texture, 323

in composition, 324

Scolecite, characteristics and occurrence

of, 33
Scoria, 97
Sedimentary and fragmentary rocks,

259

characteristics of, 259

table of geological periods of, 260

observations on the processes of the
formation of, 374

424

GENERAL INDEX.

Selenite, characteristics and occurrence
of, 49

Sericite, 23

Sericite-schist, 256

Serpentine group of rocks, 314

Serpentine, characteristics and occur-
rence of, 26, 314

varieties of, 315

Shale, the term explained, 97

argillaceous, characteristics and oc-
currence of, 268

varieties in texture of, 268
in composition of, 269

geological varieties of, 269

miners' terms for shale, 29 note

bituminous shale, 338
Shingle, formation of, 102

Siderite, characteristics and occurrence
of, 57, 345

varieties in texture and composition
of, 345

Silicates, 8

felspar section, 8

augite section, ] 6

mica section, 22

hydrous magnesian silicates (talc
section), 24

zeolite section, 28

andalusite section, 34

garnet section, 38
Silicon, oxides of, 5
Slag, volcanic, 67
Slate, the term, 97

polishing, tripoli, 349
Slates, varieties of, 264-266, 273
Smaragd, characteristics and occurrence

of, 39

Smaragdite rock, occurrence and com-
position of, 19, 318

Smithsonite. characteristics and occur-
rence of, 33

Soapstone, characteristics and occurrence
of, 25

Soda, carbonate of, characteristics and
occurrence of, 59

Soda-mesotype, characteristics and oc-
currence of, 31

Sodalite, characteristics and occurrence
of, 14

Spar, heavy, characteristics and occur-
rence of, 47, 352

manganese, 356

Spargelstein, characteristics and occur-
rence of, 53
Sparry iron-ore, 57

TIM

Spathic iron, characteristics and occur-
rence of, 57, 345

varieties in texture and composition,
345

Sphserosiderite, 58, 346

Sphalerite, 70

Sphene, characteristics and occurrence
of, 46

Spinel, characteristics and occurrence
of, 60

Spodumene, characteristics and occur-
rence of, 21

Killinite, 22
Stalactites, formation of, 99
Stalagmites, formation of, 100
Stassfurtite, occurrence of, 52, 353
Staurotide (Staurolite), characteristics

and occurrence of, 36
Steatite, characteristics of, 27, 354
Stilbite, characteristics and occurrence

of, 33

Stilpnosiderite, 67
Strahlstein. See Actinolite
Stratification ot rocks, 105
Styolites, 99
Sulphates, 47

anhydrous. 47

hydrous, 49

Sulphur, characteristics and occurrence

of, 74, 358
Sulphurets, 69
Syenite group of rocks, 176
Syenite, characteristics and occurrence

of, 177

varieties in texture of, 178

TALC section of minerals, 24
-*- Talc, characteristics and occurrence
of, 27, 354

varieties of, 27

Talc-schist, characteristics and occur-
rence of, 251

varieties of, 252
Talc-spar, characteristics of, 57
Tantalates, or Columbates, 45
Tautalite, characteristics and occur-
rence of, 45

Teschinite, 148

Tholeite, 138

Thomsonite, characteristics and occur-
rence of, 31

Thumite, characteristics and occurrence
of, 43

Timazite (Trachytic Greenstone), cha-
racteristics and occurrence of, 156

GENERAL INDEX.

425

TIN

Tin-ore, Tinstoue, characteristics and
occurrence of, 65

Tinkal, characteristics and occurrence
of, 52

Titanic iron-ore, 63

Titaniferous iron, characteristics and
occurrence of, 63

Titanite, characteristics and occurrence
of, 46

Titanites, 45

Tonalite, 207

Topanhoacanga, composition of, 343

Topaz, characteristics and occurrence
of, 35

Topaz rock, 306, 324

Tourmaline, characteristics and occur-
rence of, 37

Trachyte group of rocks, 183

varieties of, 184

Trachyte, characteristics and occurrence
of, 189

varieties in texture, 189

in composition, 190

Trachyte-porphyry, characteristics and

occurrence of, 194

varieties in texture of, 195
Travertine, 282

Tremolite, characteristics and occurrence

of, 17

Tripestone, 291
Triphane, characteristics and occurrence

of, 21

Tripoli, 349
Trona, characteristics and occurrence of,

59, 352
Tuff, Tufa, the terms explained, 97

characteristics and occurrence of, 306

volcanic tufas, basaltic and trachytic,
308

tuff formations of plutonic rocks, 309

siliceous, 349
Turf, 327

Turquois, characteristics and occurrence
of, 54

TTLTRAMARINE, characteristics and

occurrence of, 17
Uralite, characteristics and occurrence

of, 18
Urao, characteristics and occurrence

of, 59

ZWI

yANADATES, 45
' Vein, the term explained, 108

Veins, mineral, and veins of ore, 392

Vesuvian, characteristics and occurrence
of, 41

Vivianite, characteristics and occurrence
of, 54

Volcanic rocks, 111, 127, 131

Volcanic tufas, basaltic and tracbytic,
308

Volbortbite, characteristics and occur-
rence of, 47

WACKE, the term explained, 96
Wad, characteristics and occurrence
of, 67

Wavellite, characteristics and occurrence
of, 54

Wernerite, characteristics and occur-
rence of, 42, 222

Whetslate, Whetstone, 265

Wiluit, characteristics and occurrence
of, 41

Wohlerite, characteristics and occurrence
of, 46

Woodstone, material of, 7

^EOLITE section of minerals, cha-
" racteristics, properties, and occur-
rence of, 28

monometric zeolites, 29

hexagonal, 30

t rime trie, 31

monoclinic, 32

Zinc, hydrous silicate of, 33

carbonate of, 356
Zinc-ore, red, 357
Zincblende, 70

Zinc-spar, characteristics and occur-
rence of, 58

Zircon, characteristics and occurrence
of, 41

Zircon-syenite, characteristics and oc-
currence of, 181

Zoisite, characteristics and occurrence of.
41

Zwitter rock, characteristics and occur-
rence of, 322.

F F

LONDON

PRINTED BY SPOTTISWOODB AND CO.
NEW-8TBEET SQUAEE

MR. BRISTOW'S DICTIONARY OF MINERALS.

In crown 8vo. with 486 Figures on Wood, price 12. cloth,

A GLOSSARY OF MINERALOGY.

By HENRY WILLIAM BRISTOW, F.G.S.

OF THE GEOLOGICAL SURVEY OP GREAT BRITAIN.

OPINIONS OF THE PKESS.

' THIS is really a handy book. A con- j
else account of all known minerals is
given in alphabetical order, and references
are added to the cases in which specimens
may be found in the British Museum and
the Museum of Practical Geology. There
is also a useful introduction on the cha-
racters, properties, and chemical compo-
sition of minerals.'

MEDICAL TIMES and GAZETTE.

'WE can recommend Mr. BRISTOW'S
Glossary of Mineralogy to all geologists,
as well as to mining students, and the
cadets of Sandhurst and Woolwich. It
is a real handy book; the arrangement,
being alphabetical, is suited to everyone's

capacity As a work of general utility,

this book is the best of its class, and the
only one we should ever think of opening
by way of amusement. We refer to such
articles as arsenolite, amber, asbestos,
asphalt, avanturine, &c., or to that on the
diamond.' CRITIC.

'THE student in physical science has
long desired a book combining facility of
reference with a concise and familiar
account of all the known minerals. This
want is now fully supplied by the present
work, which is not a mere glossary, as
its title would imply, but is intermediate
between it and a manual. The first fifty
pages contain a description of the general
characters of minerals, their various
properties, composition, and classification ;
whilst the Glossary professes to give in-
formation upon every known mineral
substance, and this information is as
complete as the present state of our know-

ledge will allow The Author's task

has been ably executed, and his work will
be much in request.' LANCET.

' THERE has been hitherto no work in
English at all answering to this Glossary
of Mr. BRISTOW. It is a Dictionary of
Mineralogy of the most complete kind,
and yet in the most portable form, and
must become a fine qua non to every
practical mineralogist. Unincumbered
with any system of classification, it de-
scribes every mineral species or variety
alphabetically, with references to syno-
nymes, English, French, and German.
The description of the minerals is at once
concise and yet sufficient for practical
purposes. It includes their crystalline
and physical characteristics, chemical
composition (shewn both by formula and
analyses), behaviour before the blowpipe,
and their principal localities and uses.
It need scarcely be said that Mr. BRISTOW,
having the resources of the Jermyn Street
Museum at his hand, as well as the assist-
ance of so eminent a mineralogist as Mr.
WARINGTON SMITH, has had great oppor-
tunities of turning out a good book. And
he has certainly done so Notwith-
standing the great body of information it
contains, this little volume has the ad-
vantage of extreme clearness of type and
great portability. For tourists and prac-
tical men interested in mineralogy it will
be indispensable ; among the former we
expect Mr. BRISTOW'S green book will be
seen often side by side with Mr. MURRAY'S
red volumes.'

MIXING and SMELTING MAGAZINE.

London : LONGMANS, GREEN, and CO. Paternoster Row.

NEW EDITION OF BRANDE'S DICTIONARY OF SCIENCE, LITERATURE, AND

ART, RECONSTRUCTED AND GREATLY EXTENDED TO ADAPT IT

TO THE PRESENT STATE OF SCIENCE.

In course of publication periodically, to be completed in 12 PARTS, each containing

240 pages, price 5*. forming THREE VOLUMES, medium 8vo. price 21s. each,

VOLS. I. and II. now ready.

A DICTIONARY

SCIENCE, LITERATURE, AND ART

COMPRISING

THE DEFINITIONS AND DERIVATIONS OP THE SCIENTIFIC TERMS IN GENERAL USE,

TOGETHER WITH THE HISTORY AND DESCRD?TIONS OP THE
SCIENTIFIC PRINCIPLES OP NEARLY EVERY BRANCH OP HUMAN KNOWLEDGE.

EDITED BY THE LATE

W. T. BKANDE, D.C.L. F.E.S.L. & E.

Of Her Majesty's Mint, Honorary Prof, of Chemistry in the Royal Institution of Great Britain.

AND THE

REV. GEORGE W. COX, M.A.

Late Scholar of Trinity College, Oxford ;
ASSISTED BY GENTLEMEN OP EMINENT SCIENTIFIC AND LITERARY ACQUIREMENTS.

LIST OP CONTRIBUTORS.

General Editor W. T. BRANDE, F.R.S. &c. late of Her Majesty's Mint, and

Honorary Professor of Chemistry in the Royal Institution

of Great Britain.
Joint-Editor The Rev. GEORGE W. Cox, M.A. late Scholar of Trinity

College, Oxford.
Agriculture JOHN CHALMERS MORTON, Editor of the 'Agricultural

Gazette,' &c.

Architecture. History, Lan- The Rev. GEORGE W. Cox, M.A.
guage, Mythology, and General
Literature
Astronomy, Observational and E. FRANKLAND, Ph.D. F.R.S. Prof, of Chem. in the R. Inst.

Descriptive, and Meteorology of Great Britain ; and J. N. LOCKTER, Esq.
Biological Sciences, comprising Professor RICHARD OWEN, F.R.S. LL.D. D.C.L. Superin-
Anatomy, Physiology, Zoo- tendent of the Nat. Hist. Depts. Brit. Mus.; and C. CARTER
logy, and Palaeontology BLAKE, Ph.D. F.G.S. For. Assoc. of the Anthropol. Soc.

of Paris.
Botany and Gardening JOHN LINDLEY, F.R.S. F.L.S. late Emeritus Professor of Bot.

in Univ. Coll. London; and THOMAS MOORE, F.L.S.

Curator of the Botanic Garden, Chelsea.
Building and Engineering G. R. BURNELL, Architect and Civil Engineer, F.R.I.B.A.

F.G.S. F.S.A. ; and JOHN BOURNE, Civil Engineer.
General Chemistry and Physics W. T. BRANDE, D.C.L. F.R.S. L. & E. ; E. FRANKLAND, Ph.D.

F.R.S.; JOHN ATTFIELD, Ph.D. F.C.S. Director of the

Laboratories of the Pharmaceutical Soc. of Great Britain ;

JOHN BROUGHTON, B.S.; W. F. BARRETT; and HERBERT

McLEOD.

Geology, Physical Geography, D. T. ANSTED, M.A. F.R.S. F.G.S. &c. Hon. Fellow of King's

and Hydrology Coll. London.

Law, History, and General Lite- HERMAN MERIVALE, M.A. C.B. late Fellow of Balliol

rature College, Oxford.

Law ARTHUR P. WHATELY, M.A. of Lincoln's Inn, Barrister-at-

Law ; late Student of Christ Church, Oxford.
Mathematics, Pure and Applied T. A. HIRST, Ph.D. F.R.S. Prof, of Mathematical Physics in

Univ. Coll. London.
Military Subjects Lieut. H. BRACKENBUHY, R.A. F.S.A. Assistant-Instructor

in Artillery, R.M. Academy, Woolwich.
Mineralogy HENRY WILLIAM BRISTOW, F.R.S. F.G.S. Hon. Fell, of

King's Coll. Lond. of the Geol. Survey of Great Britain.

Music Prof. W. POLE, F.R.S. Mus. Bac. Oxon!

Naval Subjects DENHAM ROBINSON.

Navigation H. W. JEANS, F.R.A.S. R.N. Coll. Portsmouth.

Painting and the Fine Arts .... RALPH N. WOHNUM, Keeper and Secretary of the National

Political Economy JAMES E . THOROLD ROGERS, M.A. Professor of Political Econ.

Tooke Professor of Economic Science and Statistics in

King's Coll. London.
Printing, Bibliography, &c R. J. COURTNEY, Superintendent at Messrs. Spottiswoode

and Co.'s Printing Office.

Theology and Ecclesiastical C. MERIVALE, B.D. Chaplain to the Speaker of the House of
Literature Commons.

London: LONGMANS, GKEEN, and CO. Paternoster Eow.

GENERAL LIST OF WORKS

PUBLISHED BY

MESSRS. LONGMANS, GREEN, AND CO.

PATERNOSTER ROW, LONDON.

Historical Works.

LORD MACAULAY'S WORKS. Complete and Uniform Library
Edition. Edited by his Sister, La-ly TREVELYAN. 8 vols. 8vo. with Portrait,
price 5 5s. cloth, or J23 8s, bound in tree-calf by Riviere.

The HISTORY of ENGLAND from the Fall of Wolsey to the Death
of Elizabeth. By JAMES ANTHONY FROUDE. M.A. late Fellow of Exeter
College, Oxford. VOLS. 1. to X. in 8vo. price 7 2s. cloth.

VOLS. I. to IV. the Reign of Henry VIII. Fourth Edition, 5-1*.

VOLS*. V. and VI. the Reigns of Edward VI. and Mary. Third Edition, 23*.

VOLS. VII. and VIII. the Reign of Elizabeth, VOLS. I. and II. Fourth
Edition, 28*.

VOLS. IX. and X. the Reign of Elizabeth, VOLS. III. and IV. 32*.

The HISTORY of ENGLAND from the Accession of James II.
Lord MACAULAY.
LIBRARY EDITION", 5 vols. 8vo. 4.
CABINET EDITION, 8 vols. post 8vo. 48*.
PEOPLE'S EDITION, 4 vols. crown 8vo. 16*.

An ESSAY on the HISTORY of the ENGLISH GOVERNMENT and
Constitution, from the Reign of Henry VII. to the Present Time. By
JOHN EARL RUSSELL. Fourth Edition, revised. Crown 8vo. 6*.

On PARLIAMENTARY GOVERNMENT in ENGLAND : Its Origin,
Development, and Practical Operation. By ALPHEUS TODD, Librarian of
the Legislative Assembly of Canada. In Two Volumes. VOL. I. Svo. 1G*.

HISTORY of the REFORM BILLS of 1866 and 1867. By HOMERSHAM
Cox, M.A. Barrister-at-Law. Svo. 7*. 6d.

Antient Parliamentary Elections, a History shewing how Parlia-
ments were Constituted, and Representa Lives ol the People Elected, ia
Ancient Times. By the same Author. Svo. 8*.6d.

Whig and Tory Administrations during the Last Thirteen Yean.
By the same Author. Svo. 5*.

2 NEW WORKS PUBLISHED BY LONGMANS AND CO.

The HISTORY of ENGLAND during the Reign of George the Third.
By the Right Hon. W. N. MASSET. Cabinet Edition. 4 vols. post 8vo. 24s.

The CONSTITUTIONAL HISTORY of ENGLAND, since the Acces-
sion of George III. 17601860. By Sir THOMAS EESKINE MAT, C.B. Second
Edition. 2 vols. 8vo. 33s.

HISTORICAL STUDIES. By HERMAN MERIVALE, M.A. 8vo. price
12s. 6d.

The OXFORD REFORMERS of 1498 ; being a History of the Fellow-
work of John Colet, Erasmus, and Thomas More. By FEEDEEIC SEEBOHM.
8vo. 12s.

LECTURES on the HISTORY of ENGLAND, from the earliest Times
to the Death of King Edward II. By WILLIAM LONGMAN. With Maps
and Illustrations. 8vo. 15s.

The HISTORY of the LIFE and TIMES of EDWARD the THIRD.
By WILLIAM LONGMAN. With 9 Maps, 8 Plates, and 16 Woodcuts. 2 vols.
8vo. 28s.

HISTORY of CIVILISATION in England and France, Spain and Scot-
land. By HENEY THOMAS BUCKLE. Fifth Edition of the entire Work,
with a complete INDEX. 3 vols. crown Svo. 24s.

WATERLOO LECTURES: a Study of the Campaign of 1815. By
Colonel CHAELES C. CHESNEY, R.E. late Professor of Military Art and
History in the Staff College. Svo. with Map, 10s. 6d.

HISTORY of GRANT'S CAMPAIGN for the CAPTURE of RICH-
MOND, 1864r-1865 : with an Outline of the Previous Course of the American
Civil War. By JOHN CANNON. Post Svo. 12s. 6d.

DEMOCRACY in AMERICA. By ALEXIS DE TOCQUEVILLE. Trans-
lated by HENEY REEVE. 2 vols. Svo. 2ls.

HISTORY of the REFORMATION in EUROPE in the Time of
Calvin. By J. H. MEELE D'AusiGNE, D.D. VOLS. I. and II. Svo. 28s.
VOL. III. 12s. VOL. IV. 16s. VOL. V. price 16s.

HISTORY of FRANCE, from Clovis and Charlemagne to the Acces-
sion of Napoleon III. By EYEE EVANS CEOWE. 5 vols. Svo. 1 13s.

The HISTORY of GREECE. By C. THIRLWALL, D.D. Lord Bishop

of St. David's. 8 vols. fcp. Svo. price 28s.
The TALE of the GREAT PERSIAN WAR, from the Histories of

Herodotus. By GEOEGE W. Cox, M.A. New Edition. "Pep. 3s. Qd.

GREEK HISTORY from Themistocles to Alexander, in a Series of
Lives from Plutarch. Revised and arranged by A. H. CLOTTGH. Fcp. with
44 Woodcute, 6s.

CRITICAL HISTORY of the LANGUAGE and LITERATURE of

Ancient Greece. By WILLIAM MTJEE, of Caldwell. 5 vols. Svo. 3 9s.
HISTORY of the LITERATURE of ANCIENT GREECE. By Pro-
fessor K. O. MtiLLEE. Translated by the Right Hon. Sir GEOEGE COBNE-
WALL LEWIS, Bart, and by J. W. DONALDSON, D.D. 3 vols. Svo. 21s.

HISTORY of the CITY of ROME from its Foundation to the Sixteenth
Century of the Christian Era. By THOMAS H. DYEE, LL.D. Svo. with 2
Maps, 15s.

NEW WORKS PUBLISHED BY LONGMANS AND CO. 8

HISTORY of the EOMANS under the EMPIRE. By the Rev. C.
MERIVALB, LL.D. 8 vols. post 8vo. 48*.

The FALL of the ROMAN REPUBLIC : a Short History of the Last
Century of the Commonwealth. By the same Author. 12mo. 7*. 6d.

The HISTORY of INDIA, from the Earliest Period to the close of Lord
Dalhousie's Administration. Bv JOHN CLARK MAESHMAN. 3 vols. crown
8vo. 226-. Gil.

INDIAN POLITY : a View of the System of Administration in India.
By Major GEOROE CHESNEY, Fellow of the University of Calcutta, 8vo.
with Map, 21*.

HISTORY of the FRENCH in INDIA, from the Founding of Pondi-
chery in 1674 to its Capturo in 1761. By Lieutenant-Colonel G. B. MALLESOJT,
Bengal Staff Corps. 8vo. 16*.

REALITIES of IRISH LIFE. By W. STEUART TRENCH, Land Agent
in Ireland to the Marquess of Lansdowne, the Marquess of Bath, and Lord
Digby. With Illustrations from Drawings by the Author's Sou, J.
To WK SEND TRENCH. Third Edition, with 30 Plates. 8vo. 21*.

JOURNALS, CONVERSATIONS, and ESSAYS relating to IRELAND.
By NASSAU WILLIAM SENIOR. 2 vols. post 8vo. 21*.

MODERN IRELAND; its Vital Questions, Secret Societies, and
Government. By an ULSTERMAN. Post 8vo. 6s.

IRELAND in 1868 the BATTLE-FIELD for ENGLISH PARTY
STRIFE: its Grievances, Real and Factitious; Remedies, Abortive or
Mischievous. By GERALD FITZGIBBOX. Second Edition. 8vo. 8s. Gd.

AN ILLUSTRATED HISTORY of IRELAND, from the Earliest
Period to the Year of Catholic Emancipation. By MARY F. Ci SACK.
Second Edition, revised aud enlarged. 8vo. 18*. dd.

CRITICAL and HISTORICAL ESSAYS contributed to the Edinburgh
Meviw). By the Right Hon. LORD MAOAULAY.

LIBRARY EDITION, 3 vols. 8vo. 36*.

CABINET EDITION, 4 vols. post 8vo. 24*.

TRAVELLER'S EDITION, in One Volume, square crown 8vo. 21*.

PEOPLE'S EDITION. 2 vols. crown 8vo. 8*.

GOD in HISTORY; or, the Progress of Man's Faith in the Moral
Order of the World. By the late Baron BUNSEN. Translated from the
German by SUSANNA. WINKWORTBT; with a Preface by Dean STANLEY. In
Three Volumes. VOLS. I. and II. 8vo. 30*.

HISTORY of EUROPEAN MORALS, from Augustus to Charlemagne.

By W. E. H. LECKY, M.A. 2 vols. 8vo. price 23*.
HISTORY of the RISE and INFLUENCE of the SPIRIT of

RATIONALISM in EUROPE. By W. E. H. LECKY, M.A. Third Edition,

revised. 2 vols. 8vo. 25*.

The HISTORY of PHILOSOPHY, from Thales to Comte. By
GEORGE HENRY LEWES. Third Edition. 2 vols. 8vo. 30*.

EGYPT'S PLACE in UNIVERSAL HISTORY; an Historical Investi-
gation. By Baron BUNSEN, D.C.L. Translated by C. II. COTTRELL,
With Additions by S. BIRCH, LL.D. 5 vols. 8vo. price 8 14*. 6d.

NEW WORKS PUBLISHED BY LONGMANS AND CO.

MAUNDER'S HISTORICAL TREASURY ; comprising a General In-
troductory Outline of Universal History, and a series of Separate Histories.
Latest Edition, revised and brought down to the Present Time by the
Rev. G. W. Cox, M.A. late Scholar of Trinity College, Oxford. Fcp. 10s. Qd.

HISTORY of the NORMAN KINGS of ENGLAND. Drawn from a

New Collation of the Contemporary Chronicles, by THOMAS COBBE, of the
Inner Temple, Barrister-at-Law. 1 vol. 8vo. [Nearly ready.

HISTORY of the CHRISTIAN CHURCH, from the Ascension of
Christ to the Conversion of Constantine. By E. BURTON, D.D. late
Prof, of Divinity in the Univ. of Oxford. Eighth Edition. Fcp. 3s. Qd.

SKETCH of the HISTORY of the CHURCH of ENGLAND to the

Revolution of 1688. By the Right Rev. T. V. SHORT, D.D. Lord Bishop of
St. Asaph. Seventh Edition. Crown 8vo. 10s. Qd.

HISTORY of the EARLY CHURCH, from the First Preaching of the
Gospel to the Council of Nicaea, A.D. 325. By ELIZABETH M. SEWELL,
Author of 'Amy Herbert.' Fcp. 4s. Qd.

The ENGLISH REFORMATION. By 'F. C. MASSINGBERD, M.A.
Chancellor of Lincoln and Rector of South Ormsby. Fourth Edition, revised.
Pep. 8vo. 7s. Qd.

Biography and Memoirs.

DICTIONARY of GENERAL BIOGRAPHY; containing Concise
Memoirs and Notices of the most Eminent Persons of all Countries, from
the Earliest Ages to the Present Time. Edited by W. L. R. CATES. 8vo. 21s.

LIVES of the TUDOR PRINCESSES, including Lady Jane Grey and
her Sisters. By AGNES STRICKLAND, Author of ' Lives of the Queens of
England.' Post 8vo. with Portrait, c. 12s. Qd.

MEMOIRS of BARON BUNSEN. Drawn chiefly from Family Papers
by his Widow, FRANCES Baroness BUNSEN. Second Edition, abridged;
with 2 Portraits and 4 Woodcuts. 2 vols. post Svo. 21s.

LIFE and CORRESPONDENCE of RICHARD WHATELY, D.D. late
Archbishop of Dublin. By E. JANE WHATELY. Popular Edition, with
Additions and Omissions. Crown Svo. with Portrait, 7s. Qd.

LIFE of the DUKE of WELLINGTON. By the Rev. G. R. GLEIG,
M.A. Popular Edition, 'carefully revised , with copious Additions. Crown
Svo. with Portrait, 5s.

HISTORY of MY RELIGIOUS OPINIONS. By J. H. NEWMAN, D.D.
Being the Substance of Apologia pro Vita Sua. Post Svo, 6s.

FATHER MATHEW: a Biography. By JOHN FRANCIS MAGUIRE,
M.P. for Cork. Popular Edition, with Portrait. Crown Svo. 3s. Qd.

THE LIFE of FRANZ SCHUBERT. Translated from the German
of K. VON HELLBORN, by A. D. COLERIDGE, M.A. late Feliow of King's
College, Cambridge. With an APPENDIX by G. GROVE. 2 vols. post Svo.
with Portrait, 21s.

NEW WORKS PUBLISHED BY LONGMANS AND CO. 5

REMINISCENCES of FELIX MENDELSSOHN-BARTHOLDY; a

Social and Artistic Biography. By ELISE POLKO. Translated from the
German by Lady WALLACE. With additional Letters addressed to English
Correspondents. Post 8vo. with Portrait and View, 10*. 6d.

FELIX MENDELSSOHN'S LETTERS from Italy and Switzerland,
and Letters from 1833 to 1847, translated by Lady WALLACE. New Edition,
with Portrait. 2 vols. crown Svo. 5*. each.

FARADAY as a DISCOVERER. By JOHN TYKDALL, LL.D. F.R.S.

Professor of Natural Philosophy in the Royal Institution of Great Britain.
\\ii a Two Portraits. Crown Svo. to.

MEMOIRS of SIR HENRY HAVELOCK, K.C.B. By JOHN CLARK
MAUSHMAN. Cabinet Edition, with Port rait. Crown Svo. price 5s.

CAPTAIN COOK'S LIFE, VOYAGES, and DISCOVERIES. 18ma
Woodcuts, 2s. 6d.

LIFE of Sir JOHN RICHARDSON, C.B. sometime Inspector of Naval
Hospitals and Fleets. By the Rev. JOHN MC!LRAITH. Fcp. Svo. with
Portrait, 5*.

LIFE of PASTOR FLIEDNER, Founder of the Deaconesses' Institu-
tion at Kaiserswerth. Translated from the German by CATHERINE WINK-
WORTH. Fcp. Svo. with Portrait, 3s. Qd.

VICISSITUDES of FAMILIES. By Sir J. BERNARD BURKE, C.B,

I'istrr King of Arms. New Edition, remodelled and enlarged. 2 vols.
crown Svo. 21s.

THE EARLS of GRANARD: a Memoir of the Noble Family of Forbes.
AVritten by Admiral the Hon. JOHN FORBES, and edited by GEORGE
ARTHUR HASTINGS, present Earl of Granard, K.P. Svo. 10s.

GEORGE PETRIE, LL.D. M.R.I.A. &c. formerly President of the
Royal Hibernian Academy ; his Life and Labours in Art and Archaeology.
Ky WILLIAM STOKES, M.D. &c. Physician-in-Ordinary to the Queen m
Ireland. Svo. 12*. 6d.

ESSAYS in ECCLESIASTICAL BIOGRAPHY. By the Right Hon.
Sir J.STEPHEN, LL.D. Cabinet Edition (being the Fifth). Crown Svo. 7*. 6d.

ESSAYS on EDUCATIONAL REFORMERS: the Jesuits, Locke, J. J.
Roussrau, Pestalozzi, Jacotot, &c. By the Rev. R. H. QUICK, M.A. Trin.
Coll. Cantab. Post Svo. 7s. 6d.

ESSAYS, BIOGRAPHICAL and CRITICAL. By A. L. MEISSNER,
Ph.D. Professor of Modern Languages in Queen's College, Belfast, and in
the Queen's University iu Ireland. [Nearly ready.

MAUNDER' S BIOGRAPHICAL TREASURY. Thirteenth Edition,
reconstructed, thoroughly revised, and in great part rewritten ; with about
1,000 additional Memoirs and Notices, by W. L. R. GATES. Fcp. 10*. 6d.

LETTERS and LIFE of FRANCIS BACON, including all his Occa-
sional Works. Collected and edited, with a Commentary, by J. SPBDDINO,
Trin. Coll. Cantab. VOLS. I. and II. Svo. 24*. VOLS. ill. and IV. price 24*.

NEW WORKS PUBLISHED BY LONGMANS AND CO.

Criticism , Philosophy r , Polity -, &c.

The INSTITUTES of JUSTINIAN; with English Introduction, Trans-
lation. and Notes. By T. C. SANDABS, M.A. Barrister, late Fellow of Oriel
Coll. Oxon. Fourth Edition. 8vo. 15*.

SOCEATES and the SOCRATIC SCHOOLS. Translated from the
German of Dr. E. ZELLEE, with the Author's approval, by the Rev. OSWALD
J. REICHEL, B.C.L. and M.A. Crown 8vo. 8s. 6d.

The ETHICS of ARISTOTLE, illustrated with Essays and Notes.
By Sir A. GRANT, Bart. M.A. LL.D. Second Edition, revised aud completed.
2 vols. Svo.price 28s.

ELEMENTS of LOGIC. By E. WHATELT, D.D. late Archbishop of
Duhlin. Ninth Edition. 8vo. 10s. Gd. crown 8vo. 4s. 6tf.

Elements of Rhetoric. By the same Author. Seventh Edition.
8vo. 10s. 6d. crown 8vo. 4s. Qd.

English Synonymes. By E. JANE WHATELT. Edited by Archbishop
WHATELY. 5th Edition. Fcp. 3s.

BACON'S ESSAYS with ANNOTATIONS. By E. WHATELT, D.D.

late Archbishop of Dublin. Sixth Edition. 8vo. 10s. 6d.

LORD BACON'S WORKS, collected and edited by E. L. ELLIS, M.A.
J. SPEDDING, M.A. and D. D. HEATH. Vols. I. to V. Philosophical Works,
5 vols. 8vo. 4 6s. VOLS. VI. and VII. Literary and Professional Works,
2 vols. 1 16s.

On REPRESENTATIVE GOVERNMENT. By JOHN STUART MILL.
Third Edition. 8vo. 9s. Crown 8vo. 2s.

On LIBERTY. By JOHN STUART MILL. Fourth Edition. Post
8vo. 7s. 6d. Crown 8vo. Is. 4d. i

Principles of Political Economy. By the same Author. Sixth
Edition. 2 vols. 8vo. 30s. Or in 1 vol. crown 8vo. 5s.

A System of Logic, Ratiocinative and Inductive. By the same

Author. Seventh Edition. Two vols. 8vo. 25s.
ANALYSIS of Mr. MILL'S SYSTEM of LOGIC. By W. STEBBING,

M.A. Fellow of Worcester College, Oxford. Second Edition. 12mo. 3s. 6d.

UTILITARIANISM. By JOHN STUART MILL. Third Edition. 8vo.5*.

Dissertations and Discussions, Political, Philosophical, and His-
torical. By the same Author. Second Edition, revised. 3 vols. 8vo. 36s.

Examination of Sir W. Hamilton's Philosophy, and of the Principal
Philosophical Questions discussed in his Writings. By the same Author.
Third Edition. 8vo. 16s.

An OUTLINE of the NECESSARY LAWS of THOUGHT : a Treatise
on Pure and Applied Logic. By the Most Rev. WILLIAM, Lord Arch-
bishop of York, D.D. F.E.S. Ninth Thousand. Crown 8vo. 5s. 6d.

NEW WORKS PUBLISHED BY LONGMANS AND CO.

The ELEMENTS of POLITICAL ECONOMY. By HENRY DUNNING
MACLEOD, M.A. Barrister-at-Law. 8vo. 16*.

A Dictionary of Political Economy ; Biographical, Bibliographical,
Historical, and Practical. By the same Author. VOL. I. royal 8vo. 30*.

The ELECTION of REPRESENTATIVES, Parliamentary and Muni-
cipal ; a Treatise. By THOMAS HAKE, Barrister-at-Law. Third Edition,
with Additions. Crown 8vo. 6*.

SPEECHES of the RIGHT HON. LORD MACAULAY, corrected by
Himself. Library Edition, 8vo. 12*. People's Edition, crown 8vo. 3*. 6d.

LORD MACATJLAY'S SPEECHES on PARLIAMENTARY REFORM

in 1831 and 1832. 16mo. 1*.

INAUGURAL ADDRESS delivered to the University of St. Andrews.
By JOHX STUART MILL. 8vo. 5*. People's Edition, crown 8vo. 1*.

A DICTIONARY of the ENGLISH LANGUAGE. By R. G. LATHAM,
M.A. M.D. F.R.S. Founded on the Dictionary of Dr. SAMUEL JOHNSOW, as
edited by the Rev. H. J.ToDD.'with numerous Emendations and Additions.
In Two Volumes. VOL. I. 4to. in Two Parts, price 3 10*. In course of pub-
lication, also, in 36 Parts, price 8*. 6d. each.

THESAURUS of ENGLISH WORDS and PHRASES, classified and
arranged so as to facilitate the Expression of Ideas, and assist in Literary
Composition. By P. M. ROGBT, M.D. New Edition. Crown Svo. 10*. 6d.

LECTURES on the SCIENCE of LANGUAGE, delivered at the Royal
Institution. By MAX MULLER, M.A. Fellow of All Souls College, Oxford.
2 vols. 8vo. FIRST SERIES, Fifth Edition. 12*. SECOND SERIES, Second
Edition, 18*.

CHAPTERS on LANGUAGE. By FREDERIC W. FARRAR, F.R.S. late

Fellow of Trin. Coll. Cambridge. Crown 8vo. 8*. 6d.

WORD-GOSSIP ; a Series of Familiar Essays on Words and their
Peculiarities. By the Rev. W. L. BLACKLEY, M.A. Fcp. Svo. 5*.

A BOOK ABOUT WORDS. By G. F. GRAHAM, Author of English,
or the Art of Composition,' ' English Synonymes,' ' English Grammar
Practice, ' English Style,' &c. Fcp. Svo. [Nearly ready.

The DEBATER ; a Series of Complete Debates, Outlines of Debates,

and Questions for Discussion. By F. ROWTOIT. Fcp. 6*.
MANUAL of ENGLISH LITERATURE, Historical and Critical. By

THOMAS AHU OLD, M.A. Second Edition. Crown Svo. price 7*. 6d.
SOUTHEY'S DOCTOR, complete in One Volume. Edited by the Rev.

J. W. WARIER, B.D. Square crown Svo. 12*. Qd.
HISTORICAL and CRITICAL COMMENTARY on the OLD TESTA-

Mi:\T ; with a New Translation. By M. M. KALIBCH, Ph.D. VOL. I.

Genesis Svo. 18*. or adapted for the General Reader, 12*. VOL. II. Exodus,

15*. or adapted for the General Reader, 12*. VOL. III. Leviticus, PART I.

15*. or adapted for the General Reader, 8*.
A Hebrew Grammar, with Exercises. By the same Author. PART I.

Outlines with Exercises, Svo. 12*. 6d. KEY, 5*. PART II. Exceptional

Forms and Constructions, 12*. 6d.

NEW WORKS PUBLISHED BY LONGMANS AXD CO.

A LATIN-ENGLISH DICTIONARY. By J. T. WHITE, D.D. of
Corpus Christi College, and J. E. RIDDLE, M.A. of St. Edmund Hall, Oxford.
2 vols. 4to. pp. 2,128, price 42s. cloth.

White's College Latin-English Dictionary (Intermediate Size),
abridged for the use of University Students from the Parent Work (as
above). Medium 8vo. pp. 1,048, price 18s. cloth.

White's Junior Student's College Latin-English and English-Latin
Dictionary. Square 12mo. pp. 1,058, price 12s.
f1 f The ENGLISH-LATIN DICTIONARY, price 5*. Gd.
Separately | Tne LATIN-ENGLISH DICTIONARY, price 7s. Qd.

An ENGLISH-GREEK LEXICON, containing all the Greek Words
used by Writers of good authority. By C. D. YONGE, B.A. New Edi-
tion. 4to.2Ls.

Mr. YONGE'S NEW LEXICON, English and Greek, abridged from
his larger work (as above). Revised Edition. Square 12mo. 8s. 6d.

A GREEK-ENGLISH LEXICON. Compiled by H. G. LIDDELL, D.D.
Dean of Christ Church, and R. SCOTT, D.D. Master of Balliol. Fifth Edition.
Crown 4to. 31s. Gd.

A Lexicon, Greek and English, abridged from LIDDELL and SCOTT'S
Greek-English Lexicon, Twelfth Edition. Square 12mo. 7s. Gd.

A SANSKRIT-ENGLISH DICTIONARY, the Sanskrit words printed
both in the original Devanagari and in Roman Letters. Compiled by
T. BENFEY, Prof, in the Univ. of Gottingen. 8vo. 52s. Gd.

WALKER'S PRONOUNCING DICTIONARY of the ENGLISH LAN-
GUAGE. Thoroughly revised Editions, by B. H. SMART. 8vo. 12s. 16mo. 6s.

A PRACTICAL DICTIONARY of the FRENCH and ENGLISH LAN-
GUAGES. By L. CONTANSEAU. Thirteenth Edition. Post 8vo. 10s. 6d.

Contanseau's Pocket Dictionary, French and English, abridged from
the above by the Author. New Edition, revised. Square 18mo. 3s. Qd,

NEW PRACTICAL DICTIONARY of the GERMAN LANGUAGE;
German-English and English-German. By the Rev. W. L. BLACKLEY, M.A.
and Dr. CARL MARTIN FRIEDLANDER. Post 8vo. 7s. Gd.

Miscellaneous Works and Popular Metaphysics.

The ESSAYS and CONTRIBUTIONS of A. K. H. B., Author of ' The

Recreations of a Country Parson.' Uniform Editions :
Recreations of a Country Parson. FIRST and SECOND SERIES, crown

Svo. 3s. Gd. each.
The Common-place Philosopher in Town and Country. Crown Svo.

3s. Gd.
Leisure Hours in Town ; Essays Consolatory, ./Esthetical, Moral,

Social, and Domestic. Crown 8vo.*3s. Gd.

NEW WORKS PUBLISHED BY LONGMANS AND CO. 9

The Autumn Holidays of a Country Parson; Essays contributed
to Fraser's Magazine and to Good Words. Crown 8vo. 3s. 6d.

The Graver Thoughts of a Country Parson. FIRST and SECOND
SERIES, crown 8vo. 3s. 6d. each.

Critical Essays of a Country Parson. Selected from Essays con-
tributed to Fraser's Magazine. Crown 8vo. 3s. 6d.

Sunday Afternoons at the Parish Church of a Scottish University
City. Crown 8vo. 3s. &d.

Lessons of Middle Age, with some Account of various Cities and
Men. By A. K. H. B. Author of ' The Recreations of a Country Parson.'
Crown 8vo. 3s. &d.

Counsel and Comfort spoken from a City Pulpit. Crown 8vo. 3*. 6rf.

Changed Aspects of Unchanged Truths : Memorials of St. Andrews
Sundays. Crown Svo. 3s. 6d.

SHORT STUDIES on GEEAT SUBJECTS. By JAMES ANTHONY
FROUDE, M.A. latt> Fellow of Exeter Coll. Oxford. Third Edition. Svo. 12s.

LORD MACAULAY'S MISCELLANEOUS WRITINGS:
LIBRARY EDITION. 2 vols. Svo. Portrait, 21s.
PEOPLE'S EDITION. 1 voL crowu Svo. 4s. 6d.

The REV. SYDNEY SMITH'S MISCELLANEOUS WORKS ; includ-
ing his Contributions to the Edinburgh Review. 2 vols. crown Svo. 8s.

The Wit and Wisdom of the Rev. Sydney Smith, a Selection of
the most memorable Passages in his Writings and Conversation. 16mo. 5s.

EPIGRAMS, Ancient and Modern ; Humorous, Witty, Satirical, Moral,
and Panegyrical. Edited by Rev. JOHN BOOTH, B.A. Cambridge. Second
Edition, revised and ei Jarged. Fcp. 7s. 6d.

The PEDIGREE of the ENGLISH PEOPLE ; an Argument, His-
torical and Scientific, on the Ethnology of the English. By THOMAS
NICHOLAS, M.A. Ph.D. Svo. 16s.

The ENGLISH and THEIR ORIGIN : a Prologue to authentic English
History. By LUKE OWEN PIKE, M.A. Barrister-at-Law. Svo. 9s.

ESSAYS selected from CONTRIBUTIONS to the Edinburgh Review.
By HENRY ROGERS. Second Edition. 3 vols. fcp. 2ls.

Reason and Faith, their Claims and Conflicts. By the same Author.
New Edition, accompanied by several other Essays. Crown Svo. 6s. 6rf.

The Eclipse of Faith ; or, a Visit to a Keligious Sceptic. By the
same Author. Twelfth Edition. Fcp. 6s.

Defence of the Eclipse of Faith, by its Author ; a rejoinder to Dr.
Newman's Reply. Third Edition. Fcp. 3s. 6d.

Selections from the Correspondence of R. E. H. Greyson. By the
same Author. Third Edition. Crown Svo. 7s. Qd.

10 NEW WORKS PUBLISHED BY LONGMANS AND CO.

CHIPS from a GERMAN WORKSHOP; being Essays on the Science
of Religion, and on Mythology, Traditions, and Customs. By MAX
MULLEB. M.A. Fellow of All Souls College, Oxford. Second Edition, revised,
with an Index. 2 vols. 8vo. 24s.

ANALYSIS of the PHENOMENA of the 'HUMAN MIND. By
JAMES MILL. A New Edition, with Notes, Illustrative and Critical, by
ALEXANDER BAIN, ANDREW FINDLATER, and GEORGE GROTE. Edited,
with additional Notes, by JOHN STUART MILL. 2 vols. 8vo. price 28s.

An INTRODUCTION to MENTAL PHILOSOPHY, on the Inductive

Method. By. J.D. MORELL.M.A. LL.D. 8vo. 12s.
Elements of Psychology, containing the Analysis of the Intellectual

Powers. By the same Author. Post 8vo. 7s. 6d.
The SECRET of HEGEL : being the Hegelian System in Origin,

Principle, Form, and Matter. By J. H. STIRLING. 2 vols. 8vo. 28s.

The SENSES and the INTELLECT. By ALEXANDER BAIN, M.A.

Professor of Logic in the University of Aberdeen. Third Edition. 8vo. 15s.
The EMOTIONS and the WILL. By the same Author. Second

Edition. Svo.lSs.
On the STUDY of CHARACTER, including an Estimate of Phrenology.

By the same Author. 8vo. 9s.

MENTAL and MORAL SCIENCE: a Compendium of Psychology
and Ethics. By the same Author. Second Edition. Crown 8vo. 10s. Gd.

The PHILOSOPHY of NECESSITY ; or, Natural Law as applicable to
Mental, Moral, and Social Science. By CHABLES BRAY. Second Edition.
8vo. 9s.

The Education of the Feelings and Affections. By the same Author.
Third Edition. 8vo. 3s. 6d.

On Force, its Mental and Moral Correlates. By the same Author.
8vo. 5s.

The FOLK-LORE of the NORTHERN COUNTIES of ENGLAND and
the Borders. By WILLIAM HENDERSON. With an Appendix on House-
hold Stories by the Rev. S. BARING-GOULD, M.A. Post 8vo. 9s. 6d.

Astronomy, Meteorology, Popular Geography, &c.

OUTLINES of ASTRONOMY. By Sir J. F. W. HERSCHEL, Bart.
M.A. Ninth Edition, revised ; with Plates and Woodcuts. 8vo. 18s.

SATURN and its SYSTEM. By RICHARD A. PROCTOR, B.A. late

Scholar of St John's Coll. Camb. 8vo. with 14 Plates, 14s.

Handbook of the Stars. By the same Author. With 3 Maps. Square

fcp. 5s.
CELESTIAL OBJECTS for COMMON TELESCOPES. By the Rev.

T. W. WEBB, M.A. F.R.A.S. Second Edition, revised, with a large Map of

the Moon, and several Woodcuts. 16mo. 7s. 6<Z.

NAVIGATION and NAUTICAL ASTRONOMY (Practical, Theoretical,
Scientific) for the use of Students and Practical Men. By J. MERRIFIELD,
F.R.A.S and H. EVEBS. Svo. 14s.

NEW WORKS PUBLISHED BY LONGMANS AND CO.

DOVE'S LAW of STORMS, considered in connexion with the Ordinary
Movements of the Atmosphere. Translated by R. H.Scow, M.A. T.C.D.
8vo. 10*. 6d.

PHYSICAL GEOGRAPHY for SCHOOLS and GENERAL READERS.

By M. F. MAUEY, LL.D. Fcp. with 2 Charts, 2s. 6d.
A TREATISE on the ACTION of VIS INERTLE in the OCEAN ;

with Remarks on the Abstract Nature of the Forces of Vis Inertia- 'and
Gravitation, and a New Theory of the Tides. By WILLIAM I.I.K-II io.\
JORDAN, F.R.G.S. With 12 Charts and Diagrams. 8vo. 14*.

M'CULLOCH'S DICTIONARY, Geographical, Statistical, and Historical,
of the various Countries, Places, and Principal Natural Objects in the World.
New Edition, with the Statistical Information brought up to the latest
returns by F. MAETIN. 4 vcls. 8vo. with coloured Maps, 4 4*.

A GENERAL DICTIONARY of GEOGRAPHY, Descriptive, Physical,
Statistical, and Historical : forming a complete Gazetteer of the World. By
A. KEITH JOHNSTON, LL.D F.R G.S. Revised Edition. 8vo. Sis. 6d.

A MANUAL of GEOGRAPHY, Physical, Industrial, and Political.

By W. HUGHES, F.R.G.S. With 6 Maps. Fcp. 7*. 6d.
The STATES of the RIVER PLATE : their Industries and Commerce.

By VViLFBJD LATHAM, Buenos Ayres. Second Edition, revised. 8vo. 12*.

MAUNDER' S TREASURY of GEOGRAPHY, Physical, Historical,
Descriptive, and Political. Edited by W. HUGHES, F.R.G.S. With 7 Maps
and 16 Plates. Fcp. 10*. Qd.

Natural History and Popular Science.

ELEMENTARY TREATISE on PHYSICS, Experimental and Applied.
Translated and edited from GANOT'S Elements de Physique (with the Au-
thor's sanction) by E. ATKINSON, Ph. D. F.C.S. New Edition, revised
and enlarged ; with a Coloured Plate and 620 Woodcuts. Post 8vo. 15*.

The ELEMENTS of PHYSICS or NATURAL PHILOSOPHY. By

NEIL AENOTT, M.D. F.R.S. Physician Extraordinary to the Queen. Sixth
Edition, rewritten aud completed. Two Parts, 8vo. 21*.

SOUND: a Course of Eight Lectures delivered at the Royal Institution
of Great Britain. By JOHN TYNDALL, LL.D. F.R.S. Crown 8vo. with
Portrait of M. Chladni and 169 Woodcuts, price 9*.

HEAT CONSIDERED as a MODE of MOTION. By Professor JOHN
TYNDALL, LL.D. F.R.S. Third Edition. Crown 8vo. with Woodcuts, 10. 6d.

LIGHT : Its Influence on Life and Health. By FOKBES WINSLOW,

M.D. D.C.L. Oxon. (Hon.). Fcp. 8vo. 6*.
An ESSAY on DEW, and several Appearances connected with it.

By W. C. WELLS. Edited, with Annotations, by L. P. CASELLA, F.RJLS.

and an Appendix by R. STRACHAN, F.M.S. 8vo. 5*.

A TREATISE on ELECTRICITY, in Theory and Practice. By A.
DE LA RIVE, Prof, in the Academy of Geneva. Translated by C. V. WALKBB,
F.R.8. 3 vols. 8vo. with AVoodcuts, 3 13*.

12 NEW WORKS PUBLISHED BY LONGMANS AND CO.

The CORRELATION of PHYSICAL FORCES. By W. R. GROVE,
Q.C. V.P.R.S. Fifth Edition, revised, and followed by a Discourse on Con-
tinuity. 8vo. 10. 6d. The Discourse on Continuity, separately, 25. Qd.

MANUAL of GEOLOGY. By S. HAUGHTON, M.D. F.R.S. Revised
Edition, with 66 Woodcuts. Fcp. 7s. Qd.

A GUIDE to GEOLOGY. By J. PHILLIPS, M.A. Professor of Geology
in the University of Oxford. Fifth Edition, with Plates. Fcp. 4s.

The STUDENT'S MANUAL of ZOOLOGY and COMPARATIVE
PHYSIOLOGY. By J. BUENEY YEO, M.B. Resident Medical Tutor and
Lecturer on Animal Physiology iu King's College, London. [Nearly ready.

VAN DER HOEVEN'S HANDBOOK of ZOOLOGY. Translated from
the Second Dutch Edition by the Rev. W. CLAEK, M.D. F.R.S. 2 vols. 8vo.
with 24 Plates of Figures, 60*.

Professor OWEN'S LECTURES on the COMPARATIVE ANATOMY

and Physiology of the Invertebrate Animals. Second Edition, with 235
Woodcuts. Svo. 21s.

The COMPARATIVE ANATOMY and PHYSIOLOGY of the VERTE-

brate Animals. By RICHAED OWEN, F.R.S. D.C.L. With 1,472 Wood-
cuts. 3 vols. Svo. 3 1 3s. Qd.

The FIRST MAN and HIS PLACE in CREATION, considered on
the Principles of Common Sense from a Christian Point of View. By
GEOEGE MOOEE, M.D. Post Svo. 8s. Qd.

The PRIMITIVE INHABITANTS of SCANDINAVIA: containing a
Description of the Implements, Dwellings, Tombs, and Mode of Living of
the Savages in the North of Europe during the Stone Age. By SVEN
NILSSON. Translated from the Third Edition ; with an Introduction by
Sir J. LUBBOCK. With 16 Plates of Figures and 3 Woodcuts. Svo. 18s.

BIBLE ANIMALS ; being an Account of the various Birds, Beasts,
Fishes, and other Animals mentioned in the Holy Scriptures. Bv the Rev.

T /~i \\r^^-^ ~\if A Tn T 01 r\ i i iii L i- j i-ii- /-vrT-- _i-r-v i

One Volume, uniform with ' Homes without Hands.

HOMES WITHOUT HANDS : a Description of the Habitations of
Animals, classed according to their Principle of Construction. By Rev. J.
G. WOOD, M.A. F.L.S. With about 140 Vignettes on Wood (20 full size of
page). New Edition. Svo. 21s.

MANUAL of CORALS and SEA JELLIES. By J. R. GREENE, B.A.
Edited by JOSEPH A. GALBEAITH, M.A. and SAMUEL HAUGHTON, M.D.
Fcp. with 39 Woodcuts, 5s.

Mannal of Sponges and Animalculae; with a General Introduction
on the Principles of Zoology. By the same Author and Editors. Fcp. with
16 Woodcuts, 2s.

Manual of the Metalloids. By J. APJOHN, M.D. F.R.S. and the

same Editors. Revised Edition. Fcp. with 38 Woodcuts, 7s. Qd.

A FAMILIAR HISTORY of BIRDS. By E. STANLEY, D.D. F.R.S.

late Lord Bishop of Norwich. Seventh Edition, with Woodcuts. Fcp. 3s. 6d

NEW WORKS PUBLISHED BY LONGMANS AND CO. 13

The HARMONIES of NATURE and UNITY of CREATION. By Dr.

GEORGE HAETWIG. 8vo. with numerous Illustrations, 18s.

The Sea and its Living Wonders. By the same Author. Third
(English) Edition. 8vo. with many Illustrations, 21s.

The Tropical World. By the same Author. With 8 Chromoxylo-
graphs and 172 Woodcuts. 8vo. 21s.

The POLAR WORLD ; a Popular Description of Man and Nature in the
Arctic and Antarctic Regions of the Globe. By Dr. GEORGE ll.uuwiu.
With 8 Chromoxylographs, 3 Maps, and 85 Woodcuts. 8vo. 21s.

CEYLON. By Sir J. EMERSON TEN-KENT, K.C.S. LL.D. Fifth Edition ;
with Maps, &c. and 90 Wood Engravings. 2 vols. 8vo. JE2 10s.

KIRBY and SPENCE'S INTRODUCTION to ENTOMOLOGY, or
Elements of the Natural History of Insects. 7th Edition. Crowu 8vo. 6*.

MAUNDER' S TREASURY of NATURAL HISTORY, or Popular
Dictionary of Zoology. Revised and corrected by T. S. COBBOLD. M J).
Pep. with 900 Woodcuts. 10s. Qd.

The TREASURY of BOTANY, or Popular Dictionary of the Vegetable
Kingdom; including a Glossary of Botanical Terms. Edited by J.LiNDLET,
F.R.S. and T. MOORE, F.L.8. assisted by eminent Contributors. Pp. 1,274,
with 274 Woodcuts and 20 Steel Plates. 2 Parts, fcp. 20s.

The ELEMENTS of BOTANY for FAMILIES and SCHOOLS.
Tenth Edition, revised by THOMAS MOORE, F.L.S. Fcp. with 154 Wood-
cuts. 2s. 6d.

The ROSE AMATEUR'S GUIDE. By THOMAS RIVERS. Twelfth
Edition. Fcp. 4s. '.

The BRITISH FLORA; comprising the Phaenogamous or Flowering
Plants and the Ferns. By Sir W. J. HOOKER, K.H. and G. A. WALKBR-
ARNOTT. LL.D. 12tno. with 12 Plates, 14s. or coloured, 21s.

LOUDON'S ENCYCLOPEDIA of PLANTS; comprising the Specific
Character, Description, Culture, History, &c. of all the Plants found in
Great Britain. With upwards of 12,000 Woodcuts. 8vo. 42s.

MAUNDER' S SCIENTIFIC and LITERARY . TREASURY. New

Edition, thoroughly revised and in great part re-written, with above 1,000
new Articles, by J. Y. JOHNSON, Corr. M.2.S. Fcp. 10s. 6d.
A DICTIONARY of SCIENCE, LITERATURE, and ART. Fourth
Edition, re-edited by W. T. BRANDS (the Author), and GEORGE W. Cox, M.A .
assisted by contributors of eminent Scientific and Literary Acquirements.
3 vols. medium 8vo. price 63s. cloth.

The QUARTERLY JOURNAL of SCIENCE, Edited by JAMES
SAMUELSON and WILLIAM CROOKES, F.R.S. Published quarterly in
January, April, July, and October. 8vo. with Illustrations, price 5s. each

Number.

Chemistry, Medicine, Surgery, and the
Allied Sciences.

A DICTIONARY of CHEMISTRY and the Allied Branches of other
Sciences. By HENRY WATTS, F.R.S. assisted by eminent Contributors.
Complete in 5 vols. medium bvo. 7 3s.

14 NEW WORKS PUBLISHED BY LONGMANS AND CO.

ELEMENTS of CHEMISTRY, Theoretical and Practical. By WILLIAM
A. MILLEE, M.D. LL.D. F.R.S. F.G.S. Prof, of Chemistry, King's Coll.
London. 3 vols. 8vo. 3. PAET I. CHEMICAL PHYSICS, 15s. PART II.
INOEGANIC CHEMISTBY, 2ls. PAST III. OBGANIC CHEMISTEY, 24s.

A MANUAL of CHEMISTEY, Descriptive and Theoretical. By
WILLIAM ODLING, M.B. F.R.S. PAET 1. 8vo. 9s. PAET II. just ready.

A Course of Practical Chemistry, for the use of Medical Students.
By the same Author. New Edition, with 70 Woodcuts. Crown Svo. 7s. Qd.

Lectures on Animal Chemistry, delivered at the Royal College of
Physicians in 1865. By the same Author. Crown Svo. 4s. Qd.

HANDBOOK of CHEMICAL ANALYSIS, adapted to the UNITARY

System of Notation. By F. T. CONINGTON, M.A. P.C.S. Post Svo. 7s. Qd.
CONINGTON'S Tables of Qualitative Analysis, price 2s. Gel.

The DIAGNOSIS, PATHOLOGY, and TREATMENT of DISEASES
of Women; including the Diagnosis of Pregnancy. By GEAILY HEWITT,
M.D. Second Edition, enlarged ; with 116 Woodcut Illustrations. Svo. 2-ls.

LECTUEES on the DISEASES of INFANCY and CHILDHOOD. By

CHARLES WEST, M.D. &c. Fifth Edition, revised and enlarged. Svo. 16s.
A SYSTEM of SUEGEEY, Theoretical and Practical. In Treatises
by Various Authors. Edited by T. HOLMES, M.A. &c. Surgeon and Lecturer
on Surgery at St.'George's Hospital, and Surgeon-in-Chief to the Metro-
politan Police. 4 vols. Svo. 4 13s.

The SUEGICAL TEEATMENT of CHILDREN'S DISEASES. By
T. HOLMES, M.A. &c. late Surgeon to the Hospital for Sick Children.
Second Edition, with 9 Plates and 112 Woodcuts. Svo. 21s.

LECTUEES on the PEINCIPLES and PEACTICE of PHYSIC. By

Sir THOMAS WATSON, Bart. M.D. New Edition in preparation,

LECTUEES on SUEGICAL PATHOLOGY. By J. PAGET, F.R.S.

Edited by W. TUBNEB, M.B. New Edition in preparation.
On CHEONIC BEONCHITIS, especially as connected with GOUT,

EMPHYSEMA, and DISEASES of the HEART. By E. HEADLAM

GEEEXHOW, M.D. F.R.C.P. &c. Svo. 7s. Qd.

A TEEATISE on the CONTINUED FEVEES of GEEAT BEITAIN,

By C. MUECHISON, M.D. New Edition in preparation.
CLINICAL LECTUEES on DISEASES of the LIVEE, JAUNDICE,
and ABDOMINAL DROPSY. By CHAELES MUECHISON, M.D. Post Svo.
with 25 Woodcuts, 10s. Qd.

ANATOMY, DESCEIPTIVE and SUEGICAL. By HENRY GRAY,
F.R.S. With 410 Wood Engravings from Dissections. New, Edition, by
T. HOLMES, M.A. Cantab. Royal Svo. 2Ss.

The THEOSY of OCULAE DEFECTS and of SPECTACLES. Trans-
lated from the German of Dr. H. SCHEFFLEB by R. B. CAETEE, F.R.C.S.
With Prefatory Notes and a Chapter of Practical Instructions. Post Svo.
7s. Qd.

OUTLINES of PHYSIOLOGY, Human and Comparative. By JOHN
MAESHALL, F.R.C.S. Surgeon to the University College Hospital. 2 vols.
crown Svo. with 122 Woodcuts, 32s.

NEW WORKS PUBLISHED BY LONGMANS AKD CO. 15

ESSAYS on PHYSIOLOGICAL SUBJECTS. By GILBERT W. CHILD,
M.D. P.L.8. P.C.S. of Exeter College, Oxford. 8vo. 5s.

PHYSIOLOGICAL ANATOMY and PHYSIOLOGY of MAW. By the
lata R. B. TODD, M.D. F.R.S. and W. BOWMAN, F.R.S. of King's College.
With numerous Illustrations. VOL. II. 8vo. 25..

VOL. I. Now Edition by Dr. LIONEL S. BBALE, F.R.S. in course of publi-
cation ; PART I. with 8 Plates, 7s. 6d.

COPLAND'S DICTIONARY of PRACTICAL MEDICINE, abridged
from the larger work and throughout brought down to the present State
of Medical Science. 8vo. 36*.

The WORKS of SIR B. C. BRODIE, Bart, collected and arranged
by CHARLES HAWKINS, F.R.C.S.E. 3 vols. 8vo. with Medallion and Fac-
simile, 48s.

On ANILINE and its DERIVATIVES: a Treatise on the Manufac-
ture of Aniline and Aniline Colours. By M. RETMANN, Ph.D. L.A.M. To
which is added th^ Report on the Colouring Matters derived from Coal
Tar shewn at the Fr -nch Exhibition of 1867. Edited by WILLIAM CROOKES,
F.R.S. With 5 Woodcuts. 8vo. lQs.6d.

A MANUAL of MATERIA MEDICA and THERAPEUTICS, abridged
from Dr. PEREIRA'S Elements byF. J.FARRE, M.D. assisted by R. BENTLBT,
M.R.C.S. and by R. WARINOTON, F.R.S. 8vo. with 90 Woodcuts, 21*.

THOMSON'S CONSPECTUS of the BRITISH PHARMACOP02IA.

25th Edition, corrected by E. LLOYD BIRKETT, M.D. 18mo. price 6*.

MANUAL of the DOMESTIC PRACTICE of MEDICINE. By W. B.
KESTEVEN, F.R.C.S.E. Third Edition, revised, with Additions. Fcp. 5s.

GYMNASTS and GYMNASTICS. By JOHN H. HOWARD, late Pro-
fessor of Gymnastics, Oomm. Coll. Ripponden. Second Edition, revised
and enlarged, with 135 Woodcuts. Crown 8vo. 10. Qd.

The Fine Arts, and Illustrated Editions.

MATERIALS for a HISTORY of OIL PAINTING. By Sir CHARLES
LOCKE EASTLAKE, sometime President of the Royal Academy. VOL. II.
8vo. 149.

HALF-HOUR LECTURES on the HISTORY and PRACTICE of the

Fine and Ornamental Arts. By WILLIAM B. SCOTT. New Edition, revised
by the Author ; with 50 Woodcuts. Crown 8vo. 8s. Qd.

LECTURES on the HISTORY of MODERN MUSIC, delivered at the
Royal Institution. By JOHN HULLAH. FIRST COURSE, with Chro-
nological Tables, post 8vo. 6s. Gd. SECOND COURSE, on the Transition
Period, with 40 Specimens, 8vo. 16.

SIX LECTURES on HARMONY, delivered at the Royal Institution
of Great Britain in the Year 1^67. By G. A. MACFARREN. With nume-
rous engraved Musical Examples and Specimens. 8vo. 105. Gd.

The CHORALE BOOK for ENGLAND: the Hymns translated by
v KWORTH 5 the tunes arranged by Prof. W. S. BENNETT and
OTTO GOLDSCHMIDT. Fcp. 4to. 12*. Qd.
Congregational Edition. Fcp. 2s.

16 NEW "WORKS PUBLISHED BY LONGMANS AND CO.

SACRED MUSIC for FAMILY USE ; a Selection of Pieces for One,
Two, or more Voices, from the best Composers, Foreign and English.
Edited by JOHN HULLAH. 1 vol. music folio, price 21s.

The NEW TESTAMENT, illustrated with Wood Engravings after the
Early Masters, chiefly of the Italian School. Crown 4to.63s. cloth, gilt top ;
or 5 5s. elegantly bound in morocco.

LYRA GERMANICA ; the Christian Year. Translated by CATHERINE
WISTKWORTH ; with 125 j Illustrations on Wood drawn by J. LEIGHTON,
F.S.A. 4to.21s.

LYRA GERMANICA ; the Christian Life. Translated by CATHERINE
"WINKWORTH ; with about 200 Woodcut Illustrations by J. LEIGHTON, F.S.A.
and other Artists. 4to. 21*.

The LIFE of MAN SYMBOLISED by the MONTHS of the YEAR.
Text selected by R. PIGOT ; Illustrations on Wood from Original Designs by
J. LEIGHTON, F.S.A. 4to. 42s.

CATS' and FARLIE'S MORAL EMBLEMS ; with Aphorisms, Adages,
and Proverbs of all Nations. 121 Illustrations on Wood by J. LEIGHTON,
F.S.A. Text selected by R. PIGOT. Imperial Svo. 31s. Qd.

SHAKESPEARE'S MIDSUMMER NIGHT'S DREAM, illustrated
with 24 Silhouettes or Shadow-Pictures by P. KONEWKA, engraved on Wood
by A. VOGEL. Folio, 31s. 6d.

SHAKSPEARE'S SENTIMENTS and SIMILES, printed in Black and
Gold, and Illuminated in the Missal Style by HENRY NOEL HUMPHREYS.
Square post Svo. 21s.

SACRED and LEGENDARY ART. By Mrs. JAMESON.

Legends of the Saints and Martyrs. Fifth Edition, with 19

Etchings and 187 Woodcuts. 2 vols. square crown Svo. 31s. 6d.
Legends of the Monastic Orders. Third Edition, with 11 Etchings

and 88 Woodcuts. 1 vol. square crown Svo. 21s.
Legends of the Madonna. Third Edition, with 27 Etchings and 165

Woodcuts. 1 vol. square crown Svo. 21s.
The History of Our Lord, with that of his Types and Precursors.

Completed by Lady EASTLAKE. Revised Edition, with 31 Etchings and

281 Woodcuts. 2 vols. square crown Svo. 42s.

Arts, Manufactures, &c.

DRAWING from NATURE. By GEORGE BARNARD, Professor of
Drawing at Rugby School. With 18 Lithographic Plates, and 108 Wood
Engravings. Imperial Svo. price 25s. Or in Three Parts, royal Svo. 7s. Qd.
ach.

eacr

GWILT'S ENCYCLOPEDIA of ARCHITECTURE, with above 1,100
Engravings on Wood. Fifth Edition, revised and enlarged by WTATT
PAPWORTH. Additionally illustrated with nearly 400 Wood Engravings by
O. Jewitt, and more than 100 other new Woodcuts. Svo. 52s. Qd.

NEW WORKS PUBLISHED BY LONGMANS AITD CO. 17

ITALIAN SCULPTORS ; being a History of Sculpture in Northern,
Southern, and Eastern Italy. By C. C. PERKINS. With 30 Etchings and
i:j NVood Engravings. Imperial 8vo. 42*.

TUSCAN SCULPTORS, their Lives, Works, and Times. With 45
Etchings and 28 Woodcuts from Original Drawings and Photographs. By
the same Author. 2 vols. imperial 8vo. 63*.

ORIGINAL DESIGNS for WOOD-CARVING, with PRACTICAL IN-

strnctions in the Art. By A. F. B. With 20 Plates of Illustrations engraved

on Wood. 4to. 18*.
HINTS on HOUSEHOLD TASTE in FURNITURE, UPHOLSTERY,

and other Details. By CHARLES L. EASTLAKE, Architect. With about

90 Illustrations. Square crown 8vo. 18*.
The ENGINEER'S HANDBOOK; explaining the Principles which

should guide the Young Engineer in the Construction of Machinery. By

C. S. LOWNDES. Post 8vo. 6*.
The ELEMENTS of MECHANISM. By T. M. GOODEVE, M.A.

Professor of Mechanics at the R. M. Acad. Woolwich. Second Edition,

with 217 Woodcuts. Post 8vo. 6*. Qd.

LATHES and TURNING, Simple, Mechanical, and ORNAMENTAL.
By W. HENRY NORTHCOTT. With about 240 Illustrations on, Steel and
Wood. 8vo. 18*.

URE'S DICTIONARY of ARTS, MANUFACTURES, and MINES.
Sixth Edition, chit-fly rewritten and greatly enlarged by ROBERT HUNT,
F.R.S. assisted by numerous Contributors eminent in Science and the Arts,
and familiar wv.h Manufactures. With above 2,000 Woodcuts. 3 vols. me-
dium 8vo. price 1 14*. 6d.

HANDBOOK of PRACTICAL TELEGRAPHY, published with the
sanction of the Chairman and Directors of the Electric and International
Telegraph Company, and adopted by the Department of Telegraphs for
India. By R. S. CULLEY. Third Edition. 8vo. 12*. Qd.

ENCYCLOPEDIA of CIVIL ENGINEERING, Historical, Theoretical,
and Practical. By E. CRESY, C.E. With above 3,000 Woodcuts. 8vo. 42s.

TREATISE on MILLS and MILLWORK. By W. FAIRBAIRN, C.E.

Second Edition, with 18 Plates and 822 Woodcuts. 2 vols. 8vo. 32*.
Useful Information for Engineers. By the same Author. FIRST,

SECOND, and THIRD SERIES, with many Plates and Woodcuts. 3 vols.

crown 8vo. 10*. 6d. each.
The Application of Cast and Wrought Iron to Building Purposes.

By the same Author. Third Edition, with 6 Plates and 118 Woodcuts. 8vo. 16*.

IRON SHIP BUILDING, its History and Progress, as comprised in a

Srrios of Experimental Researches. By the same Author. With 4 Plates and

i:]ii Woodcuts, fevo. 18*.
A TREATISE on the STEAM ENGINE, in its various Applications

t< Mini's Mills, Steam Navigation, Rail wavs and Agriculture. By J.BouRNB,

!:. Eighth Edition : with Portrait, 37 Plates, and 646 Woodcuts. 4to. 42*.
Catechism of the Steam Engine, in its various Applications to

Mi-ii-s, Mills, Steam Navigation, Railways, and Agriculture. By the same

Author. With 89 Woodcuts. Fcp. 6*.
Handbook of the Steam Engine. By the same Author, forming a

KEY to the Catechism of the Steam Engine, with 67 Woodcuts. Fcp. *.
c

18 NEW WOHKS PUBLISHED BY LONGMANS AND CO.

A TEEATISE on the SCREW PEOPELLEE, SCEEW VESSELS, and

Screw Engines, as adapted for purposes of Peace and War ; with Notices
of other Methods of Propulsion, Tables of the Dimensions and Performance
of Screw Steamers, and detailed Specifications of Ships and Engines. By
J. BOUEXE, C.E. Third Edition, with 54 Plates and 287 "Woodcuts. 4to. 63s.

EXAMPLES of MODEEN STEAM, AIE, and GAS ENGINES of

the most Approved Types, as employed for Pumping, for Driving Machinery,
for Locomotion, and for Agriculture, minutely and practically described.
Illustrated by Working Drawings, and embodying a Critical Account of all
Projects of Recent Improvement in Furnaces, Boilers, and Engines. By
the same Author. In course of publication monthly, to be completed in ii4
Parts, price 2s. Gd. each, forming One volume 4to. with about 50 Plates and
400 Woodcuts.

A HISTOEY of the MACHINE- WEOTJGHT HOSIEEY and LACE

Manufactures. By WILLIAM FELKIN, F.L.S. F.S.S. Royal Svo. 215.
PEACTICAL TEEATISE on METALLUEGY, adapted from the last
German Edition of Professor KEEL'S Metallurgy by W. CEOOKES, F.R.S. &c.
and E. ROHEIG, Ph.D. M.E. VOL. I. comprising Lead, Silver, Zinc,
Cadmium, Tin, Mercury, Bismuth, Antimony, Nickel, Arsenic, Gold,
Platinum, and Sulphur. Svo. with 207 Woodcuts, 31s. Gd.

MITCHELL'S MANUAL of PEACTICAL ASSAYING. Third Edi-
tion, for the most part re- written, with all the recent Discoveries incor-
porated, by W. CEOOKES, F.R.S. With 188 Woodcuts. Svo. 28s.

The AET of PEEFUMEEY ; the History and Theory of Odours, and
the Methods of Extracting the Aromas of Plants. By Dr. PIESSE, F.C.S.
Third Edition, with 53 Woodcuts. Crown Svo. 10s. Gd.

Chemical, Natural, and Physical Magic, for Juveniles during the
Holidays. By the same Author. Third Edition, with 38 Woodcuts. Fcp. 6s.

LOUDON'S ENCYCLOPEDIA of AGEICULTUEE : comprising the
Laying-out, Improvement, and Management of Landed Property, and the
Cultivation and Economy of the Productions of Agriculture. With 1,100
Woodcuts. Svo. 31s. 6d.

London's Encylopaedia of Gardening : comprising the Theory and
Practice of Horticulture, Floriculture, Arboriculture, and Landscape Gar-
dening. With 1,000 Woodcuts. Svo. 31s. 6d.

BAYLDON'S AET of VALUING EENTS and TILLAGES, and Claims
of Tenants upon Quitting Farms, both at Michaelmas and Lady-Day.
Eighth Edition, revised by J. C. MOETO:S. Svo. 10s. Gd.

Religious and Moral Works.

An EXPOSITION of the 39 AETICLES, Historical and Doctrinal.
By E. HAEOLD BEOWNE, D.D. Lord Bishop of Ely. Seventh Edit. Svo. 16s.

AECHBISHOP LEIGHTOK'S SEEMONS and CHAEGES. With
Additions and Corrections from MSS. and with Historical and other Illus-
trative Notes by WILLIAM WEST, Incuoibent of S. Columba's, Nairn.
Svo. 15*.

The ACTS of the APOSTLES ; with a Commentary, and Practical and
Devotional Suggestions for Readers and Students of the English Bible. By
the Rev. F. C. COOK, M.A. Canon of Exeter, &c. New Edition. Svo. 12s. Gd.

NEW WORKS PUBLISHED BY LONGMANS AND CO. 19

The LIFE and EPISTLES of ST. PAUL. By W. J. CONYBEARE,

M.A. late Fellow of Trin. Coll.Cantab. and the Very Rev. J. S. HOWSON, DJ>.
Dean of Chester.

LIBRARY EDITION, with all the Original Illustrations, Maps, Landscapes
on Steel, Woodcuts, Ac. 2 vols. 4to. 48*.

INTERMEDIATE EDITION, with a Selection of Maps, Plates, and Woodcuts.
2 vols. square crown 8vo. 31*. 6d.

PEOPLE'S EDITION, revised and condensed, with 46 Illustrations and
Maps. 2 vols. crown 8vo. 12*.

The VOYAGE and SHIPWRECK of ST. PAUL; with Dissertations
on the Life and Writings of St. Luke and the Ships and Navigation of the
Ancients. By JAMES SMITH, F.R.S. Third Edition. Crown 8vo. 10*. 6d.

The NATIONAL CHURCH; HISTORY and PRINCIPLES of the
CHURCH POLITY of ENGLAND. By D. MOUNTFIELD, M.A. Rector
of Newport, Salop. Crown 8vo. 4s.

EVIDENCE of the TRUTH of the CHRISTIAN RELIGION derived
from the Literal Fulfilment of Prophecy. By ALEXANDER KEITH, D.D.
37th Edition, with numerous Plates, in square 8vo. 12*. 6d. ; also the 39th
Edition, in post 8vo. with 5 Plates, 6s.

The HISTORY and DESTINY of the WORLD and of the CHURCH.
according to Scripture. By the same Author. Square 8vo. with 40
Illustrations, 10*.

A CRITICAL and GRAMMATICAL COMMENTARY on ST. PAUL'S

Epistles. By C. J. ELLICOTT, D.D. Lord Bishop of Gloucester & Bristol. 8ro.
Galatians, Fourth Edition, 8s. (jd.
Ephesians, Fourth Edition, 8s. 6d.
Pastoral Epistles, Fourth Edition, 10s. 6<i.
Philippians, Colossians, and Philemon, Third Edition, 10s. 6<f.
Thessalonians, Third Edition, 7s. Qd.
Historical Lectures on the Life of our Lord Jesus Christ : being the

Hulsean Lectures for 1859. By the same Author. Fourth Edition. 8vo.

price 10*. Qd.

An INTRODUCTION to the STUDY of the NEW TESTAMENT,

Critical, Eiegetical, and Theological. By the Rev. S. DAVIDSON, D.D.
LL.D. 2 vols. 8vo. 30*.

Rev. T. H. HORNE'S INTRODUCTION to the CRITICAL STUDY

and Knowledge of the Holy Scriptures. Twelfth Edition, as last revised
throughout and brought up to the existing state of Biblical Knowledge
under careful Editorial revision. With 4 Maps and 22 Woodcuts and Fac-
similes. 4 vols. 8vo. 42*.

Rev. T. H. Home's Compendious Introduction to the Study of the
Bible, being an Analysis of the larger work by the same Author. Re-edited
by the Rev. JOHN AYRE, M.A. With Maps, Ac. Post 8vo. 6*.

EWALD'S HISTORY of ISRAEL to the DEATH of MOSES. Trans-
lated from the German. Edit< d, with a Preface and an Appendix, by RUSSELL
MARTINEAU, M.A. Prof, of Hebrew in Manchester New Coll. London.
Second Edition, continued to the commencement of the Monarchy. 2 vols.
8vo. 24*. VOL. II. comprising Joshua and Judges, for Purchasers of the
First Edition, 9*.

20 NEW WORKS PUBLISHED BY LONGMANS AND CO.

The TREASURY of BIBLE KNOWLEDGE ; being a Dictionary of the
Books, Persons, Places, Events, and other matters of which mention is made
in Holy Scripture. By Rev. J. AYEE, M.A. With Maps, 16 Plates, and
numerous Woodcuts. Fcp. 105. Gd.

The GREEK TESTAMENT; with Notes, Grammatical and Exegetical.
By the Rev. W. WEBSTEE, M.A. and the Rev. W. F. WILKINSON, M.A.
2 vols. 8vo. 2 4s.

VOL. I. the Gospels and Acts, 205.

VOL. II. the Epistles and Apocalypse, 24?.

The CHURCHMAN'S DAILY REMEMBRANCER of DOCTRINE
and DUTY : consisting of Meditations taken from the Writings of Standard
Divines from the Early Days of Christianity to the Present Time ; with a
Preface by W. R. FEEMANTLE, M.A. New Edition. Fcp. 8vo. 6s.

EVERY-DAY SCRIPTURE DIFFICULTIES explained and illustrated.
By J. E.PEESCOTT, M.A. VOL. I. Matthew and Mark; VOL. II. Luke and
John. 2 vols. 8vo. 9*. each.

The PENTATEUCH and BOOK of JOSHUA CRITICALLY EXAMINED.
By the Right Rev. J. W. COLENSO, D.D. Lord Bishop of Natal. People's
Edition, in 1 vol. crown Svo. 6s. or in 5 Parts, Is. each.

The CHURCH and the WORLD : Three Series of Essays on Questions
of the Day. By Various Writers. Edited hy the Rev. OEBY SHIPLEY,
M.A. FIEST SEEIES, Third Edition, 15.?. SECOND SEEIES, Seiond Edition,
15s. THIED SEEIES, 1868, price 15s. 3 vols. Svo. 45s.

The FORMATION of CHRISTENDOM. By T. W. ALLIES. PARTS L
and II. Svo. price 12s. each Part.

ENGLAND and CHRISTENDOM. By ARCHBISHOP MANNIKG, D.D.
Post Svo. price 10s. Gd.

CHRISTENDOM'S DIVISIONS, PART I., a Philosophical Sketch of
the Divisions of the Christian Family in East and West. By EDMUND S.
FFOULKES. Post Svo. price 7s. Gd.

Christendom's Divisions, PART II. Greeks and Latins, being a His-
tory of their Dissensions and Overtures for Peace down to the Reformation.
By the same Author. Post Svo. 15s.

The WOMAN BLESSED by ALL GENERATIONS; or, Mary the

Object of Veneration, Confidence, and Imitation to all Christians. By the
Rev. R. MELIA, D.D. P.S.M. With 78 Illustrations. Svo. 15s.

LIFE of the BLESSED VIRGIN; the FEMALL GLORY. By
ANTHONY STAFFORD. Together with the Apology of the Author, and an
Essay on the Cultus cf the Blessed Virgin Mary. Fourth Edition, with
Facsimiles of the 5 Original Illustrations. Edited by the Ilev. OSBY
SHIPLEY, M.A. Fcp. Svo. 10s. Gd.

CELEBRATED SANCTUARIES of the MADONNA. By the Rev. J.
SPENCEE NOETHCOTE, D.D. Post Svo. 6s. Gd.

The HIDDEN WISDOM of CHRIST and the KEY of KNOWLEDGE ;

or, History of the Apocrypha. By EENEST DE BUNSEN. 2 vols. Svo. 28s.
The KEYS of ST. PETER ; or, the House of Rechab, connected with
the History of Symbolism and Idolatry. By the same Author. Svo. 14s.

NEW WORKS PUBLISHED BY LONGMANS A.ND CO. 11

The TYPES of GENESIS, briefly considered as Revealing the
Development of Human Nature. By ANDREW JUKES. Second Edition.
Crown 8vo. Is. Qd.

The Second Death and the Restitution of All Things, with some
Preliminary Remarks on the Nature and Inspiration of Holy Scripture.
By the same Author. Second Edition. Crown Svo.S*. Qd.

ESSAYS and REVIEWS. By the Rev. W. TEMPLE, D.D. the Rev.
R. WILLIAMS, B.D. the Rev. B. POWELL, M.A. the Rev. H. B. WILSON,
B.D. C. W. GOODWIN, M.A. the Rev. M. PATTIBON, B.D. and the Rev. B.
JOWETT, M.A. Twelfth Edition. Fcp. 8vo. 6*.

The POWER of the SOUL over the BODY. By GEORGE MOORE,
M.D. M.R.C.P.L. Ac. Sixth Edition. Crown 8vo. 8s. Qd.

PASSING THOUGHTS on RELIGION. By ELIZABETH M. SEWELL,

Author of ' Amy Herbert.' New Edition. Fcp. 8vo. 5*.
Self-Examination hefore Confirmation. By the same Author. 32mo.

price 1*. Qd.
Readings for a Month Preparatory to Confirmation, from Writers

of the Early and English Church. By the same Author. Fcp. 4s.
Readings for Every Day in Lent, compiled from the Writings of

Bishop JEREMY TATLOE. By the same Author. Fcp. 5*.

Preparation for the Holy Communion; the Devotions chiefly from
the works of JEREMY TAYLOR. By the same. 32mo. 3*.

PRINCIPLES of EDUCATION Drawn from Nature and Revelation,
and applied to Female Education in the Upper Classes. By the Author
of ' Amy Herbert.' 2 vols. fcp. 12s. Qd.

The WIFE'S MANUAL; or, Prayers, Thoughts, and Songs on Several
Occasions of a Matron's Life. By the Rev. W. CALVERT, M.A. Crown 8vo.
price 10s. Qd.

SINGERS and SONGS of the C3URCH : being Biographical Sketches
of the Hymn- Writers in all the principal Collections; with Notes on their
Psalms and Hymns. By JOSIAH MILLER, M.A. New Edition, enlarged.
Crown 8vo. [Nearly ready.

' SPIRITUAL SONGS ' for the SUNDAYS and HOLIDAYS through-
out the Year. By J. S. B. MONSELL, LL.D. Vicar of Ej$ham and Rural Dean.
Fourth Edition, Sixth Thousand. Fcp. 4. Qd.

The Beatitudes : Abasement before God ; Sorrow for Sin ; Meekness
of Spirit ; Desire for Holiness ; Gentleness ; Purity of Heart ; the Peace-
makers ; Sufferings for Christ. By the same. Third Edition. Fcp. 3*. Qd.

His PRESENCE not his MEMORY, 1855. By the same Author,
in Memory of his SON. Sixth Edition. 16mo. 1*.

LYRA DOMESTICA; Christian Songs for Domestic Edification.
Translated from the Psaltery and Harp of C. J. P. SPITTA, and from other
sources, by RICHARD MASSIE. FIRST and SECOND SERIES, fcp. 4. Qd. each.

LYRA GERMANICA, translated from the German by Miss C. WINK-
WORTH. FIRST SERIES, Hymns for the Sundays and Chief Festivals.
SECOND SERIES, the Christian Life. Fcp. 3*. 6d. each SERIES.

22 NEW WORKS PUBLISHED BY LONGMANS AND CO.

LYRA EUCHARISTICA ; Hymns and Verses on the Holy Communion,
Ancient and Modern : with other Poems. Edited by the Rev. OBEY SHIP-
LEY, M.A. Second Edition. Fcp. Is. Qd.

Lyra Messianica ; Hymns and Verses on the Life of Christ, Ancient
and Modern ; with other Poems. By the same Editor. Second Edition,
altered and enlarged. Fcp. 7s. Qd.

Lyra Mystica ; Hymns and Verses on Sacred Subjects, Ancient and
Modern. By the same Editor. Fcp. 7*. Qd.

ENDEAVOURS after the CHRISTIAN LIFE : Discourses. By
JAMES MARTINEATT. Fourth and cheaper Edition, carefully revised ; the
Two Series complete in One Volume. Post 8vo. 7s. Qd.

WHATELY'S Introductory Lessons on the Christian Evidences.

18mo. Qd.
INTRODUCTORY LESSONS on the HISTORY of RELIGIOUS

Worship; being a Sequel to the 'Lessons on Christian Evidences.' By

RICHARD WHATELY, D.D. New Edition. 18mo. 2s. Qd.
BISHOP JEREMY TAYLOR'S ENTIRE WORKS. With Life by

BISHOP HEBEE. Revised and corrected by the Rev. C. P. EDEN, 10 vols.

price 5 5s.

Travels, Voyages, &c.

SIX MONTHS in INDIA. By MARY CARPENTER. 2 vols. post 8vo.
with Portrait, 185.

NARRATIVE of the EUPHRATES EXPEDITION carried on by
Order of the British Government during the years 1835, 1836. and 1837.
By General F. R. CHESNEY, F.R.S. With 2 Maps, 45 Plates, and 16 Wood-
cuts. 8vo. 24s.

The NORTH-WEST PENINSULA of ICELAND ; being the Journal
of a Tour in Iceland in the Summer of 1862. By C. W. SHEPHERD, M.A.
F.Z.S. With a Map and Two Illustrations. Fcp. 8vo. 7s. Qd.

PICTURES in TYROL and Elsewhere. From a Family Sketch-Book.
By the Authoress of ' A Voyage en Zigzag,' &c. Second Edition. Small 4to.
with numerous Illustrations, 21s. ff 3 y+*-

HOW WE SPENT the SUMMER ; or, a Voyage en Zigzag in Switzer-
land and Tyrol with some Members of the ALPINE CLTTB. From the Sketch-
Book of one of the Party. In oblong 4to. with 300 Illustrations, 15s.

BEATEN TRACKS ; or, Pen and Pencil Sketches in Italy. By the
- Authoress of ' A Voyage en Zigzag.' With 42 Plates, containing about 200
Sketches from Drawings made on the Spot. 8vo. 16s.

MAP of the CHAIN of MONT BLANC, from an actual Survey in
18631864. By A. ADAMS-REILLY, F.R.G.S. M.A.C. Published under the
Authority of the Alpine Club. In Chromolithography on extra stout
drawing-paper 28in. x 17in. price 10s. or mounted on canvas in a folding
case, 12s. Qd.

HISTORY of DISCOVERY in our AUSTRALASIAN COLONIES,

Australia, Tasmania, and New Zealand, from the Earliest Date to the
Present Day. By WILLIAM HOWITT. 2 vols. 8vo. with 3 Maps, 20s.

NEW WORKS PUBLISHED BY LONGMANS AND CO. 28

The CAPITAL of the TYCOON ; a Narrative of a Three Years' Resi-
dence in Japan. By Sir RUTHERFORD ALCOCK, K.C.B. 2 vols. 8vo. with
numerous Illustrations, 42*.

The DOLOMITE MOUNTAINS ; Excursions through Tyrol, Carinthia,
Carniola, and Friuli, 1861-1863. By J. GILBERT and G. C CHURCHILL,
F.R.G.S. With numerous Illustrations. Square crown Svo. 21*.

GUIDE to the PYRENEES, for the use of Mountaineers. By
CHARLES PACKE. 2d Edition, with Map and Illustrations. Cr. Svo. 7*. Qd.

The ALPINE GUIDE. By JOHN BALL, M.R.I.A. late President of
the Alpine Club. 3 vols. post Svo. with Maps and other Illustrations :

Guide to the Eastern Alps, price 10s. 6d.

Guide to the Western Alps, including Mont Blanc, Monte Rosa,
Zermatt, &c. Price 6*. Qd.

Guide to the Central Alps, including all the Oberland District. 7*. 6d.

Introduction on Alpine Travelling in General, and on the Geology
of the Alps, price Is. Each of the Three Volumes or Parts of the Alpine
Guide may be had with this INTRODUCTION prefixed, price Is. extra.

NARRATIVES of SHIPWRECKS of the ROYAL NAVY between 1793
and 1857, compiled from Official Documents in the Admiralty by W. O. S.
GILLT ; with a Preface by W. S. GILLY, D.D. Third Edition. Fcp. 6s.

TRAVELS in ABYSSINIA and the GALLA COUNTRY; with an
Account of a Mission to Ras AH in 184S. From theMSS. of the late WALTER
CHICHELE PLOWDEN, Her Britannic Majesty's Consul in Abyssinia. Edited
by his Brother TREVOR CHICHELE PLOWDEN. With Two Maps. 8vo. 18*.

MEMORIALS of LONDON and LONDON LIFE in the 13th, 14th,
and 15th Centuries ; being a Series of Extracts, Local, Social, and Political,
from the Archives of the City of London. A.D. 1276-1419. Selected,
translated, and edited by H. T. RILEY, M.A. Royal Svo. 21*.

COMMENTARIES on the HISTORY, CONSTITUTION, and CHAR-
TERED FRANCHISES of the CITY of LONDON. By GEORGE NORTON,
formerly one of the Common Pleaders of the City of London. Third Edition'
Svo. 14*.

CURIOSITIES of LONDON ; exhibiting the most Rare and Remarkable
Objects of Intere>tin the Metropolis; with nearly Sixty Years' Personal
Recollections. By JOHN TIMES, F.S.A. Now Edition, corrected and en-
larged. 8vo. with Portrait, 21*.

The NORTHERN HEIGHTS of LONDON ; or, Historical Associations
of Hanipstead, Highgate, Muswell Hill, Hornsey, and Islington. By
WILLIAM HOWITT. With about 40 Woodcuts. Square crown Svo. 21*.

VISITS to REMARKABLE PLACES: Old Halls, Battle-Fields, and
Scenes Illustrative of Striking Passages in English History and Poetry.
By WILLIAM HOWITT. 2 vols. square crown Svo. with Woodcuts, 26*.

The RURAL LIFE of ENGLAND. By the same Author. With
Woodcuts by Bewick and Williams. Medium Svo. 12*. Qd.

The IRISH in AMERICA. By JOHN FRANCIS MAGUIRE, M.P. for

Cork. Post Svo. 12*. Qd.

24 NEW WORKS PUBLISHED BY LONGMANS AND CO.

ROMA SOTTERRANEA ; or, an Account of the Roman Catacombs,
and especially of the Cemetery of St. Callixtus. Compiled from the Works
of Commendatore G. B. DE Rossi, with tbe consent of the Author, by the
Rev. J. S. NOETHCOTE, D.D. and the Rev. W. B. BEOWNLOW. With
"numerous Engravings on Wood, 10 Lithographs, 10 Plates in Chromo-
lithography, and an Atlas of Plans, all executed in Rome under the Author's
superintendence for this Translation. 1 vol. 8vo. [Nearly ready.

Works of Fiction.

The WARDEN: a Novel. By ANTHONY TROLLOPE. Crown 8vo. 2s. 6rf.
Barchester Towers : a Sequel to ' The Warden.' Crown 8vo. 3s. 6d.
STORIES and TALES by ELIZABETH M. SEWELL, Author of Amy
Herbert,' uniform Edition, each Tale or Story complete in a single Volume.

AMY HEEBEET, 2s. 6d. j IVOES, 3s. 6d.

GEETEUDE, 2*. Qd. KATHAEINE ASHTON, 3s. 6d.

EAEL'S DAUGHTEE, 2s. 6d. MAEGAEET PEECIVAL, 5s.

EXPEEIENCE OP LIFE, 2s. Gd. LANETON PAESOKAGE, 4s. Qd.

CLEVE HALL, 3s. Qd. \ UESULA, 4s. 6d.

A Glimpse of the World. By the Author of 'Amy Herbert.' Fcp. 7s. 6d.
The Journal of a Home Life. By the same Author. Post 8vo. 9s. 6rf.
After Life ; a Sequel to ' The Journal of a Home Life.' Price 10s. 6d.
UNCLE PETER'S FAIRY TALE for the XIX CENTURY. Edited

by E. M. SEWELL, Author of 'Amy Herbert,' &c. Fcp. 8vo. 7s. 6d.
BECKER'S GALLUS ; or, Roman Scenes of the Time of Augustus :

with Notes and Excursuses. New Edition. Post 8vo. 7s. Qd.

BECKER'S CHARICLES; a Tale illustrative of Private Life among the
Ancient Greeks : with Notes and Excursuses. New Edition. Post 8vo. 7s. 6d.

NOVELS and TALES by G. J. WHYTE MELVILLE :

The GLADIATOES, 5s.
DIGBY GEAND, 5s.
KATE COVENTEY, 5s.
GENEEAL BOUNCE, 5s.

HOLMBY HOUSE, 5s.
GOOD FOE NOTHING, 6s.
The QUEEN'S M ABIES, 6s.
The INTEEPEETEE, 5s.

TALES of ANCIENT GREECE. By GEORGE W. Cox, M.A. late
scholar of Trin. Coll. Oxon. Being a Collective Edition of the Author's
Classical Stories and Tales, complete in One Volume. Crown 8vo. 6s. 6d.

A MANUAL of MYTHOLOGY, in the form of Question and Answer.
By the same Author. Fcp. 3s.

Poetry and The Drama.

THOMAS MOORE'S POETICAL WORKS, the only Editions contain-
ing the Author's last Copyright Additions :
SHAMEOCK EDITION, crown 8vo. price 3s. 6d.
RUBY EDITION, crown 8vo. with Portrait, price 6s.
PEOPLE'S EDITION, square crown 8vo. with Portrait, &c. 12s. Qd.
LIBEAEY EDITION, medium 8vo. Portrait and Vignette, Us.
CABINET EDITION, 10 vols. fcp. 8vo. price 35s.

NEW WORKS PUBLISHED BY LONGMANS AND CO. 25

MOORE'S IRISH MELODIES, Maclise's Edition, with 161 Steel Plates
from Original Drawings. Super-royal 8vo. 31*. 6d.

Miniature Edition of Moore's Irish Melodies with Maclise's De-
signs (as above) reduced in Lithography. Imp. 16mo. 10*. 6d.

MOORE'S LALLA ROOKH. Tenniel's Edition, with 68 Wood
Engravings from original Drawings and other Dlustrations. Fcp. 4to. 21*.

SO^THEY'S POETICAL WORKS, with the Author's last Corrections
and copyright. Additions. Library Edition, in 1 vol. medium 8vo. with
Portrait and Vignette, 14*. or in 10 vols. fcp. 3*. 6d. each.

LAYS of ANCIENT ROME; with Ivry and the Armada. By the
Right Hon. LORD MACAULAT. 16mo. 4*. 6d.

Lord Macaulay's Lays of Ancient Rome. With 90 Illustrations on
Wood, from the Antique, from Drawings by G. SCHARF. Fcp. 4to. 21*.

Miniature Edition of Lord Macaulav's Lays of Ancient Rome,
with the Illustrations (as above) reduced in Lithography. Imp.l6mo.lO*.6<

GOLDSMITH'S POETICAL WORKS, with Wood Engravings from
Designs by Members of the ETCHING CLUB. Imperial IGmo. 7ft. 6d.

MEMORIES of some CONTEMPORARY POETS ; with Selections from
their Writings. By EMILY TAYLOR. Royal 18mo. 5*.

POEMS. By JEAN INGELOW. Thirteenth Edition. Fcp. 8vo. 5*.

POEMS by Jean Ingelow. With nearly 100 Illustrations by Eminent
Artists, engraved on Wood by the Brothers DALZIEL. Fcp. 4to. 21*.

A STORY of DOOM, and other Pems. By JEAN INGELOW. Fcp. 5*.

POETICAL WORKS of LETITIA ELIZABETH LANDON (L.E.L.).

2 vols. 16mo. 10*.

BOWDLER'S FAMILY SHAKSPEARE, cheaper Genuine Edition,
complete in 1 vol. large type, with 36 Woodcut Illustrations, price 14*. or
with the same ILLUSTRATIONS, in 6 pocket vols. 3s. Qd. each.

HORATII OPERA, Pocket Edition, with carefully corrected Text,
Marginal References, and Introduction. Edited by the Rev. J. E.
YONGE, M.A. Square 18mo. 4s. 6d.

HORATII OPERA. Library Edition, with Marginal References and
English Notes. Edited by the Rev. J. E. YONGB. 8vo. 21*.

The JENEID of VIRGIL Translated into English Verse. By JOHN

CONIJIGTON, M.A. Crown 8vo. 9*.
ARTJNDINES CAMI, sive Musarum Cantabrigiensium Lusus canori.

Collegit atque edidit H. DRURY, M.A. Editio Sexta, curavit H. J. HODGSON,

M.A. Crown 8vo. 7*. 6d.

EIGHT COMEDIES of ARISTOPHANES, viz. the Acharnians, Knights,

Clouds. Wasps, Peace, Birds, Frogs, and Plutus. Translated into Rhymed

Metres by LEONARD HAMPSON RUDD, M.A. 8vo. 15*.
PLAYTIME with the POETS : a Selection of the best English Poetry

for the use of Children. By a LADY. Revised Edition. Crown 8vo. 6*.
The HOLY CHILD : a Poem in Four Cantos; also an Ode to Silence,

and other Poems. By STEPHEN JENNEU, M.A. Fcp. 8vo. 6*.
D

26 NEW WORKS PUBLISHED BY LONGMANS AND CO.

The ILIAD of HOMEB TRANSLATED into BLANK VERSE. By
ICHABOD CHARLES WEIGHT, M.A. 2 vols. crown 8vo. 21s.

The ILIAD of HOMER in ENGLISH HEXAMETER VERSE. By
J. HENRY DAET, M.A. of Exeter Coll. Oxford. Square crown 8vo. 21s.

The ODYSSEY of HOMER. Translated into Blank Verse by G. W.
EDGINTON, Licentiate in Medicine. Dedicated by permission to Edward
Earl of Derby. VOL. I. 8vo. with Map, 10s. 6d.

DANTE'S DIVINE COMEDY, translated in English Terza Kima by
JOHN DAYMAN, M.A. [With the Italian Text, after Brunetti, interpaged.]
8vo. 21s.

HUNTING SONGS and MISCELLANEOUS VERSES. By R. E.

EGEETON WAEBUBTON. Second Edition. Fcp. 8vo. 5s.

An OLD STORY, and other Poems. By ELIZABETH D. CROSS.
Second Edition. Fcp. 8vo. 3s. Qd.

The THREE FOUNTAINS, a Faery Epic of Euboea ; with other
Verses. By the Author of ' The Afterglow.' Fcp. 8vo. 3s. &d.

The Afterglow ; Songs and Sonnets for my Friends. By the Author
of ' The Three Fountains.' Second Edition. Fcp. 8vo. 5s.

The SILVER STORE collected from Mediaeval Christian and Jewish
Mines. By the Rev. SABINE BAEING-GOULD, M.A. Crown 8vo. 6s.

Bural Sports, &c.

ELAINE'S ENCYCLOPEDIA of RURAL SPORTS ; Hunting, Shoot-
ing, Fishing, Racing, &c. With above 600 Woodcuts (20 from Designs by
JOHN LEECH). 8vo. 42s.

Col. HAWKER'S INSTRUCTIONS to YOUNG SPORTSMEN in all

that relates to Guns and Shooting. Revised by the Author's SON. Square
crown 8vo. with Illustrations, 18s.

The DEAD SHOT, or Sportsman's Complete Guide ; a Treatise on
the Use of the Gun, Dog-breaking, Pigeon- shooting, &c. By MARKSMAN.
Revised Edition. Fcp. 8vo. with Plates, 5s.

The FLY-FISHER'S ENTOMOLOGY. By ALFRED RONALDS. With
coloured Representations of the Natural and Artificial Insect. Sixth
Edition : with 20 coloured Plates. 8vo. 14s.

A BOOK on ANGLING ; a complete Treatise on the Art of Angling
in every branch. By FEANCIS FEANCIS. Second Edition, with Portrait
and 15 other Plates, plain and coloured. Post 8vo. 15s.

HANDBOOK of ANGLING : Teaching Fly-fishing, Trolling, Bottom-
fishing, Salmon-fishing ; with the Natural History of River Fish, and the
best modes of Catching them. By EPHEMEEA. Fcp. Woodcuts, 5s.

WILCOCKS'S SEA-FISHERMAN ; comprising the Chief Methods of
Hook and Line Fishing in the British and other Seas, a Glance at Nets,
and Remarks on Boats and Boating. Second Edition, enlarged ; with 80
Woodcuts. Post 8vo. 12s. Qd.

The CRICKET FIELD ; or, the History and the Science of the Game
of Cricket. By JAMES PYCBOFT, B.A. Fourth Edition. Fcp. 5s.

NEW WOE*S PUBLISHED BY LONGMANS AND CO. tj

^ ^t

HORSE and MAN. By C. S. MARCH PHILLIPPS, Author of Juris-
prudence,' &.c. Fop. 8vo. 2s. (kfi

The HOESE'S FOOT, and HOW to KEEP IT SOUND. By W.

MILES, Esq. Ninth Edition, with Illustrations. Imperial 8vo. 12*. 6d.

A Plain Treatise on Horse-Shoeing. By the same Author. Sixth
Edition. Post 8vo. with Illustrations, 28. 6d.

Stables and Stable-Fittings. Bythesame. Imp. 8vo. with 13 Plates, 15*.

Eemarks on Horses' Teeth, addressed to Purchasers. By the same.
Post 8vo, la. 6d.

BOBBINS'S CAVALRY CATECHISM, or Instructions on Cavalry
Exercise and Field Movements, Brigade Movements, Out-post Duty, Cavalry
supporting Artillery, Artillery attached to Cavalry. 12mo. 65.

ELAINE'S VETEBINABY AET ; a Treatise on the Anatomy, Physi-
ology, and Curative Treatment of the Diseases of the Horse, Neat Cattle
and Sheep. Seventh Edition, revised and enlarged by C. STEEL, M.R.C.V.SX.
8vo. with Plates and Woodcuts. 18*.

The HOESE : with a Treatise on Draught. By WILLIAM YOUATT.

New Edition, revised and enlarged. 8vo. with numerous Woodcuts, 12*. 6d.

The Dog. By the same Author. 8vo. with numerous Woodcuts, 6*.

The DOG in HEALTH and DISEASE. By STONEHENGE. With 70

"Wood Engravings. Square crown 8vo. 10*. Qd.
The GREYHOUND. By STONEHENGE. Revised Edition, with 24

Portraits of Greyhounds. Square crown 8vo. 10*. Qd.

The OX ; his Diseases and their Treatment: with an Essay on Parturi-
tion in the Cow. By J. R. DOBSON. Crown 8vo. with Illustrations, 7*. 6d.

Commerce, Navigation, and Mercantile Affairs.

BANKING, CUEEENCY, and the EXCHANGES ; a Practical Trea-
tise. By ARTHUR CRUMP. Post 8vo. 6*.

The ELEMENTS of BANKING. By HENRY DUNNING MACLEOD, M.A.
Barrister-at-Law. Post 8vo. [Nearly ready.

The THEOEY and PEACTICE of BANKING. By the same Author.
Second Edition, entirely remodelled. 2 vols. 8vo. 30*.

PEACTICAL GUIDE for BEITISH SHIPMASTEES to UNITED

States Ports. By PIEBREPONT EDWARDS. Post 8vo. 8*. 6d.

A DICTION ABY, Practical, Theoretical, and Historical, of Com-
merce and Commercial Navigation. By J. R. M'CrLLOCH. Esq. New and
thoroughly revised Edition. 8vo. price 63*. cloth, or 70*. half-bd. in russia.

The LAW of NATIONS Considered as Independent Political Com-
munities. By Sir TRAVERS Twiss, D.C.L. 2 vols. 8vo. 30*. or separately,
PART I. Peace, 12*. PART II. War, 18.

NEW WORKS PUBLISHED BY LONGMANS AND CO.

Works of Utility and General Information.

MODERN COOKERY for PRIVATE FAMILIES, reduced to a System
of Easy Practice in a Series of carefully-tested Receipts. By ELIZA ACTON.
Newly revised and enlarged Edition ; with 8 Plates of Figures and 150
Woodcuts. Fcp. 6*.

On FOOD and its DIGESTION ; an Introduction to Dietetics. By
W. BBINTON, M.D. With 48 Woodcuts. Post 8vo. 12s.

WINE, the VINE, and the CELLAR. By THOMAS G. SHAW.
Second Edition, revised and enlarged, with 32 Illustrations. 8vo. 16s.

A PRACTICAL TREATISE on BREWING ; with Formulae for Public
Brewers, and Instructions for Private Families. By W. BLACK. 8vo. 10s. 6d.

SHORT WHIST. By MAJOR A. A thoroughly revised Edition, with an
Essay on the Theory of the Modem Scientific Game by PEOF. P. Fcp. 3s. Qd.

WHIST, WHAT TO LEAD. By CAM. Fourth Edition. 32mo. 1*.

A HANDBOOK for READERS at the BRITISH MUSEUM. By

THOMAS NICHOLS. Post Svo. 6s.

The CABINET LAWYER ; a Popular Digest of the Laws of England,
Civil, Criminal, and Constitutional. Twenty -fourth Edition, brought down
to the close of the Parliamentary Session of 1868. Fcp. 10s. 6d.

The PHILOSOPHY of HEALTH ; or, an Exposition of the Physio-
logical and Sanitary Conditions conducive to Human Longevity and
Happiness. By SOUTHWOOD SMITH, M.D. Eleventh Edition, revised and
enlarged ; with 113 Woodcuts. Svo. 7s. &d.

HINTS to MOTHERS on the MANAGEMENT of their HEALTH
during the Period of Pregnancy and in the Lying-in Room. By T. BULL,
M.D. Fcp. 5s.

The Maternal Management of Children in Health and Disease. By
the same Author. Fcp. 5s.

The LAW RELATING to BENEFIT BUILDING SOCIETIES; with
Practical Observations on the Act and all the Cases decided thereon ; also a
Form of Rules and Forms of Mortgages. By W. TIDD PKATT, Barrister.
Second Edition. Fcp. 3s. 6d.

NOTES on HOSPITALS. By FLORENCE NIGHTINGALE. Third Edi-
tion, enlarged ; with 13 Plans. Post 4to. 18s.

COULTHART'S DECIMAL INTEREST TABLES at 24 Different Kates
not exceeding 5 per Cent. Calculated for the use of Hankers. To which are
added Commission Tables at One-Eighth and One-Fourth per Cent. Svo.
price 15s.

MAUNDER' S TREASURY of KNOWLEDGE and LIBRARY of

Reference: comprising an English Dictionary and Grammar, Universal
Gazetteer, Classical Dictionary, Chronology, Law Dictionary, a Synopsis
of the Peerage, useful Tables, &c. Revised Edition. Fcp. 10s. 6d.

INDEX.

ACTON'S Modern Cookery 28

Afterglow (The) *6

ALCOCK'S Residence in Japnn 2!

ALLiuon Formation of Christendom 2C

Alpine Guide (The) 2S

APJOHN'S Manual of the Metalloids 12

ARNOLD'S Manual of English Literature.... 7

ARNOTT'I Elements of Physics 11

ArundinesCarni 25

Autumn holidays of a Country Parson .. i

AYIIB'S Treasury of Bible Knowledge 20

BACON'S Essays, by WHATELV 6

Life and Letters, by SPRDDINO 5

Works, edited by Sp i. DDINO 6

BA.N'S Mental and Moral Science 10

on the Emotions and Will 10

on the Senses and Intellect lo

on the Study of Character 10

BALI,'. Alpine Guide *3

BARNARD sDrawin? from Nature 16

BATLDON'S Hentsund Tillages If

Beaten Tracks 25

BROKER'S Charicles an/I Callus 24

BENPBY'S Sanskrit Dictionary 8

BLACK'S Treatise on Brewing 28

BLACK LEY'* Word- Gossip 7

BLACKI.EY and FRIBDLANDBR'S German and

Knglish Dictionary 8

BLAINB'S Rural Sports

Veterinary Art 27

BOOTH'S Epigrams J

BOURNE on Screw Propeller ll

BOURNE'S Catechism of the Steam Engine. 17

Handbook ofSteam Entrine 17

Treatise on the Steam Engine.. 17

Examples of Modern Engines . I*

BOWDLBR'S Family SHAKSPFARE 25

BRANDS'* Dictionary of Science, Literature

and Art 13

BRAT'S (C.) Education of the Feelings 10

Philosophy of Necessity 10

onForce 10

BRINTON on Food and Digestion 2f

BRODiB's'PirC.B.) Works 16

BROWNE'S Exposition of the 39 Articles .... 18

BOCKU'J History of Civilization 5

BULL'S Hints to Mothers 18

Maternal Management of Children. 28

BCNSBM'S (Baron) Ancient Egypt 3

Godinllistory 3

Memoirs 4

BUNSBN (E. DB)OH Apocrypha SO

'$ Keys of St. Peter SO

Bi'HK' VicisMtude. of Families 6

BURTON'S Christian Church 4

Cabinet Lawyer S8

CALVBRT'S Wife's Manual

CANNON 's Grant's Campaign

CARPKNTRR'S Six Months in India

CATES'S Biographical Dictionary

CATS' and FARLIB'S Moral Emblems

Changed A speets of Unchanged Truthi. ...

CHK-NRYS Euphrates Expedition *

Indian Polity

Waterloo Campaign \

CHILD'S Physiological Essays ]|

Chorale Book for England

Christian Schools and Scholars '<

< hurchman's Daily Remembrancer..

CLOUOH'S Lives from Plutarch '

COBBB'S Norman Kings of England ........ *

CoLRioiBihop)on Pentateuch and Book

of Joshua SO

Commonplace Philosopher in Town and

Country

CONINOTON'S Chemical Analysis '<

Translation of VIROIL'S jEnetd So

CONTANSBAU'S French- English Dictionnries 8

CONVBBARB and HOWSON'S Work on St. Paul 19

COOK on the Acts 18

COOK'S Voyages A

COPLAND'S Dictionary of Practical Medicine 16

COI-I.TIIART'S Decimal Interest Tables *8

Counsel and Comfort from a City Pulpit .. fl

Cox's (G.W.) Manual of Mythologv 24

: Tale of the Great Persian War 8

.Tales of Ancient Greece 24

(H.) Ancient Parliamentary Elections
Hiotory of the Reform Bills

Whig and Tory Administrations I

CRBSY'S Encyclopaedia of Civil Engineering 17

Critical Esiays of a Country Parson 9

CHOP'S Old Story 26

CROWE'S History of France *

CRHMP on Banking. Currency, & Exchanges 27

CDLLBT'S Handbook of Telegraphy 17

CUSACK'S History of Ireland 3

DART'S Iliad of Homer *6

D'AowMi'i History of the Reformation In

the time of CALVIN S

DAVIDSON'S Introduction to New Testament 19

DAYMAN'S Dante's Di vina Commedia 26

Dead Shot (The), by MARKSMAN M

DR LA RIVE'S Treatise on Electricity 11

Dr. MnROANon Matter and Spirit 9

DB TOCQOBVILI.B'S Democracy in America.. i

DOB*OW on the Ox 27

Dovie on storms 11

DIBR'S City of Rome S

EASTLARB'S Hints on Household Taste .... 17
Histo