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GIFT TO THE LIBRARY

CIVIL ENGINEERING DEPARTMENT

UNIVERSITY OF CALIFORNIA

PROFESSOR FRANK SOULE
1912

L-

WORKS OF PROF. S. E. TILLMAN

PUBLISHED BY

JOHN WILEY & SONS,

Descriptive General Chemistry.

A Text-book for Short Course. 8vo, cloth,
83.00, net.

Elementary Lessons in Heat.

Second edition, revised and enlarged. 8vo,
cloth, $1.50, net.

A Text-book of Important Minerals and Rocks.

With Tables for the Determination of Minerals.
8vo, cloth, 186 pages. $2.00, net.

A TEXT-BOOK .

IMPORTANT MINERALS
AND ROCKS.

WITH

TABLES FOR THE DETERMINATION
OF MINERALS.

S. E. TILLMAN,

of Chemistry \ Mineralogy, ant
U. S. Military Academy, West Point, N. Y.

Professor of Chemistry, Mineralogy, and Geology,

FIRST EDITION.
FIRST THOUSAND.

NEW YORK:

JOHN WILEY & SONS.

LONDON: CHAPMAN & HALL, LIMITED.

1900.

' -•* V: X- ""> "• -

BY
S. E. TILLMAN,

ROBERT DRUMMOND, PRINTER, NEW YORK.

PREFACE.

THIS book is the slow outgrowth of the efforts to meet
the necessities of this institution for a convenient text-book
of the important minerals and rocks. The number of min-
eral species has reached nearly one thousand and is con-
stantly increasing. Of this number less than one-tenth is of
common occurrence or can be considered of much economic
importance, and a small proportion of this same tenth in-
cludes the essential constituents of all roeks. To embrace
in descriptive text all mineral species necessarily results in
an embarrassing mass of matter for the general student.
Similar embarrassment, though to a less extent, is experienced
in complete descriptions of all the rocks/ To reduce these
descriptions to a convenient yet satisfactory form for gen-
eral students is the object of the present effort.

There are described in the book about seventy-five dis-
tinct species of the important and in the main common min-
erals, and the principal members of the different classes of
rocks. It is thought that the selection is extended enough
for general purposes, and it includes abundant material for
the study of both minerals and rocks. The book is prima-
rily prepared to meet the necessities of the Military Academy,
whose students are well fitted for the work when they begin
it, have excellent opportunity for the examination and com-
parison of specimens, and for laboratory work in determin-

iii

785375

IV PREFACE.

ing them. It is hoped that the book may be of conveni-
ence to a larger class of students whose facilities in the
study may be less, but whose aim is the same as ours — to
acquire a fair knowledge of the important minerals and
rocks.

Chapter I of the book contains in brief outline the more
fundamental principles of crystallography, followed by a
description of the different crystalline systems and of some
of the more important crystalline aggregates and irregular
forms. The subject-matter of the chapter can be almost
indefinitely extended by lecture if so desired. The reason
that the crystallographic branch is so briefly treated is stated
in the introduction to the book, no other treatment being
considered appropriate in a short general course.

Chapter II contains a short description of the general
properties of minerals, of the laboratory facilities for de-
termining them, and of the manner of using these facilities.

In Chapter III an effort has been made to give a concise
and accurate statement of the more readily observed phy-
sical properties of the mineral species and of the ordinary
mineralogical tests for distinguishing and determining them.
There are also added many desirable facts relating to the
use and occurrence of the minerals.

A table for the determination of minerals follows this
chapter and is intended for a guide and companion in the
practical examinations and tests of the minerals.

The table merely puts in condensed form the described
properties and characteristics of the minerals as given in
Chapter III. This tabular arrangement has many advan-
tages over a descriptive text-book without tables, or with
tables bound in separate form. A statement of the proper-
ties of each species in the body of the text as well as in the
table has been found advantageous when recitation and
practical work are conducted simultaneously.

The tables have been a slow growth, of nearly twenty
years, from very simple beginnings, and have during that
time been used by our pupils under separate binding. In

PREFA CE. - V

this preparation I have had valuable suggestions from sev-
eral officers who have served as instructors in the depart-
ment, but I would here especially acknowledge my great
indebtedness to Capt. J. P. Wisser, /th U. S. Artillery, who,
as Lieutenant Wisser and while serving as Assistant Profes-
sor in the Department in 1890 and '91, did the larger part of
the work which placed the tables in their present shape.

Part II is devoted to the common rocks. The prin-
ciples of classification, the classes, and the distinguishing
characteristics of each class are given ; the appearance of the
different members of each class is described and their min-
eral composition given, to which are added many important
facts as to occurrence and use and the more prominent con-
clusions as to origin.

The greater portion of the matter contained in the
book, exclusive of the mineral tables and the contents of
Chapter I, has been used at the Academy for the past six
years, and has been frequently added to and revised during
that time.

The arrangement of mineral species in the text is mod-
eled after that of the late Professor J. DrDana in his man-
ual of Mineralogy and Petrography. The mineral com-
pounds of the same metals are brought together, except in
the case of silicates. The important metals and their ores
are consecutively treated, as are the important rock-making
minerals. This arrangement has, from experience, been
found very satisfactory.

In the preparation of this little book I have consulted
many authorities, but would especially acknowledge my
obligations for mineralogical matter to the works of Pro-
fessors J. D. Dana, E. S. Dana, G. J. Brush, S. L. Penfield,
H. Bauerman, W. O. Crosby, D. M. Barringer ; for petro-
graphic material to various published papers of the U. S.
Geological Survey, to the works of Professors J. F. Kemp,
W. B. Scott, and J. D. Dana; for the chapter on Crystal-
lography to the works of Professors G. H. Williams, E. S»
Dana, H. Bauerman, and N. Story Maskelyne.

of the more important crystalline aggregates cj
forms. The subject-matter of the chapter a
indefinitely extended by lecture if so desired,
that the crystallographic branch is so briefly trej
in the introduction to the book, no other tre;
considered appropriate in a short general courj|

Chapter II contains a short description o™JBp"c
properties of minerals, of the laboratory facil™
termining them, and of the manner of using th|

In Chapter III an effort has been made to gj
and accurate statement of the more readily oti
sical properties of the mineral species and of •
mineralogical tests for distinguishing and deter™
There are also added many desirable facts re|
use and occurrence of the minerals.

A table for the determination of minerals
chapter and is intended for a guide and comp
practical examinations and tests of the minerals

The table merely puts in condensed form t
properties and characteristics of the minerals 'Wrcii til
Chapter III. This tabular arrangement has many advan-
tages over a descriptive text-book without tables, or with
tables bound in separate form. A statement of the proper-
ties of each species in the body of the text as well as in the
table has been found advantageous when recitation and
practical work are conducted simultaneously.

The tables have been a slow growth, of nearly twenty
years, from very simple beginnings, and have during that
time been used by our pupils under separate binding. In

PREFA CE. • V

this preparation I have had valuable suggestions from sev-
eral officers who have served as instructors in the depart-
ment, but I would here especially acknowledge my great
indebtedness to Capt. J. P. XVisser, /th U. S. Artillery, who,
as Lieutenant Wisser and while serving as Assistant Profes-
sor in the Department in 1890 and '91, did the larger part of
the work which placed the tables in their present shape.

VI PREFACE.

Through the courtesy of Professor E. S. Dana I have
been permitted to use the crystalline figures shown under
numbers 2, 3, 4, $, 18, 20, 22, 25, and 26, which are taken
from his Text-book of Mineralogy. Figures 19, 31, 32, 33,
and 34 are from Williams's Elements of Crystallography,
through the courtesy of the publishers, Henry Holt & Co.

S. E. TILLMAN,

U. S. MILITARY ACADEMY, WEST POINT, N. Y.,
October i, 1900.

TABLE OF CONTENTS.

PART I.
IMPORTANT MINERALS.

CHAPTER I.

ELEMENTS OF CRYSTALLOGRAPHY.

PAGES

INTRODUCTORY REMARKS 1-3

GEOMETRIC SYMMETRY 3-4

CRYSTALLOGRAPHIC SYMMETRY ~. 4-6

CRYSTALLOGRAPHIC AXES 6-9

CRYSTALLOGRAPHIC LAWS 9-10

CRYSTALLINE SYSTEMS 11-18

CRYSTAL FORMS 18

DISTORTIONS IN CRYSTALS 19-22

CRYSTALLINE AGGREGATES 23-24

CHAPTER II.

PHYSICAL AND CHEMICAL PROPERTIES OF MINERALS.

PHYSICAL PROPERTIES OF MINERALS 25-27

•CHEMICAL PROPERTIES OF MINERALS 27-31

CHAPTER III.

DESCRIPTIVE MINERALOGY.

NATIVE ELEMENTS 32-40

ORES OF SILVER 40-42

ORE OF MERCURY 42-43

COPPER AND ITS ORES 43-48

ORES OF LEAD. 48- r

vti

Vlll TABLE OF CONTENTS.

PAGES

ORES OF ZINC 51-52

ORES OF IRON 53-60

ORES OF ANTIMONY AND MANGANESE 60-61

TIN ORE 61

RARE MINERALS 62-65

COMPOUNDS OF SODIUM AND POTASSIUM 65-67

COMPOUNDS OF CALCIUM 67-74

QUARTZ, SILICA 74-78

SILICATES 78-94

M i NERAL COAL 94-96

DESCRIPTION OF TABLES 96-97

TABLES FOR DETERMINATION OF MINERALS 98-137

PART II.

COMMON ROCKS.

ROCK CONSTITUENTS 139-140

CLASSIFICATION OF ROCKS 140-141

SEDIMENTARY ROCKS 141-152

IGNEOUS OR UNSTRATIFIED ROCKS 152-158

TABULAR CLASSIFICATION OF ROCKS 158

METAMORPHIC ROCKS 159-161

The following abbreviations are used in the text :

Before blowpipe B.B.

Color C.

Hardness H.

Luster L.

Oxidizing Flame , O.F.

Reducing Flame .^, . . R.F.

Sign of inequality — greater than >

Specific gravity G.

PART I.
IMPORTANT MINERALS.

CHAPTER I.
INTRODUCTORY REMARKS.

THE natural objects of the universe can in general be
included in two great groups or kingdoms, the organic and
the inorganic. To the first belong the bodies which origi-
nate through the agency of life, to the second the bodies not
thus originating.

Those bodies occurring in the inorganic kingdom which
have a definite chemical composition are termed minerals.
Mineralogy is the science which describes and teaches how
to distinguish and determine minerals. The distinction of
minerals from each other is based upon the consideration of
the composition, external form, and internal structure, all of
which must be determined and investigated in the full
classification of minerals.

The term ' mineral species ' is generally made to include
all those minerals which have the same composition and a
definite form and structure. With few exceptions minerals
at ordinary temperatures are solids, and all minerals in be-
coming solid, whether from state of vapor, fusion, or solu-
tion, tend, under favorable conditions, to form regular
geometrical solids bounded by plane surfaces. The regular
forms thus assumed by minerals are called crystals. The
natural bounding-plane surfaces of a crystal are called the
faces, the lines in which the faces intersect are called edges,

CR 1 'S TA LLOGRA PH Y.

the angles between edges are plane angles, those between
faces are interfacial angles, and those formed by the meeting
of three or more faces are solid angles.

In the study of crystal forms it was early observed —

i st. That there was a marked symmetry in the arrange-
ment of their parts, as faces, edges, points, etc.

2d. It was discovered that the forms of the same species
obeyed certain laws that made possible a geometrical classi-
fication of the crystals of different species.

It was later developed by studying the physical proper-
ties of the crystals that there is an intimate and complete
accord between these properties and the forms of the crys-
tals, and that the form is but the obvious external evidence
of a definite internal structure ; that it is the structure that
is characteristic, the form and physical properties are the
evidences of the structure.

The consideration of the properties or characteristics
which distinguish minerals (structure, form, composition)
give rise to two distinct divisions of the science of min-
eralogy.

I. Crystallographic mineralogy, which considers the
form and structure of the minerals, and this has two
branches :

(a) Geometric or morphological crystallography, which
considers the external form of minerals and the geometric
relations of their faces and plane surfaces.

(b) Physical crystallography, which investigates the
properties which are mainly the result of structure, i.e.,
physical properties, such as cohesion, elasticity, and the
properties displayed under the action of light, heat, elec-
tricity, etc.

II. Chemical mineralogy, which is primarily concerned
with determining the chemical composition of the minerals.
It also extends to the consideration of the chemical relations
between constitution and form.

The knowledge obtained through all the above branches
of mineralogy when systematically arranged and presented,
together with information as to mode of occurrence, distri-

ELEMENTS OF GEOMETRIC SYMMETRY. 3

bution, and association of the different species, constitutes
Descriptive Mineralogy.

Thorough acquaintance with all branches of mineralogy
are essential to the work of specialists, but for the general
student the essentially chemical branch is far more impor-
tant, for through it the composition can usually be more
readily determined, and it is upon the composition that all
other relations depend. For this reason only brief reference
will be made in this book to the crystallographic branch,
and then only to the most fundamental principles.

CRYSTALLOGRAPHIC CONSIDERATIONS.

Elements of Geometric Symmetry in the Form of Solids. —

The symmetry of form in solids may be considered with
reference to planes of symmetry, axes of symmetry, or cen-
ters of symmetry.

Planes of Symmetry. — The form of a solid is geometri-
cally symmetrical with reference to a plane when the plane
divides the solid into two precisely corresponding parts, so
that every normal to the plane section would meet a cor-
responding point of the solid at the same distance from the
section. A polyhedron placed upon a plane mirror forms
with its image a symmetrical figure, of which the mirror
surface is the plane of symmetry. Again, a plane passing
through the center of a cube parallel to either face divides
it symmetrically, and it is at once evident that there are
three such planes for a cube. So the planes passing through
the diagonally opposite edges of a cube are planes of sym-
metry. There is generally a distinction between the mineral-
ogical symmetry of crystals and the full geometric sym-
metry of figure here defined. This distinction will appear
subsequently.

Axes of Symmetry. — An axis of symmetry of a solid is a.
line about which if the body be rotated it will successively
occupy the same position, or will fill the same place in space..
Axes of symmetry can be distinguished from each other by
the number of times the body occupies the same position^
during a complete revolution about each.

CR YS TA LL OCR A PH Y.

A cube turned about a line joining the middle point of
opposite faces will occupy the same position four times dur-
ing one revolution ; such line is an axis
of quaternary or tetragonal symmetry.
A line joining the middle points of
diagonally opposite edges in a cube is
an axis of binary symmetry. In the
square octahedron, Fig. I, the vertical
axis a is an axis of quaternary sym-
metry, while c and d are axes of binary
symmetry. The axis about which the
third or a higher order exists is a
principal axis of symmetry; other axes
are secondary axes.

FIG. i,

Center of Symmetry. — A center of symmetry
of a solid exists when a line passing through the
center meets similar points in the opposite halves of the crystal at the
same distance from the center. A center of symmetry may exist without
•either axes or planes of symmetry being present.

In every case of a center the crystal polyhedron is bounded by pairs
of parallel planes which are at equal distances from the center, and it
can always be shown that the points in which a line through the center
pierces any two of these planes are corresponding points in two halves
into which the crystal may be divided.

Crystallographic Symmetry. — Geometric symmetry, above
referred to, relates to the external form of the solid. In
crystals, as already stated, the physical properties have a
definite, constant and most intimate connection with the ex-
ternal form. Both form and physical properties are deter-
mined by the structure of the particular body ; the struc-
ture is the most essential physical character of the crystal,
and the form is only the most important external mani-
festation of the structure. A solid in the form of a
crystal, without the related internal structure, does not
constitute a crystal ; such a solid is only a model of the ex-
ternal form.

Natural crystals very frequently exhibit geometric sym-

CR YS TA LLOGRA PHIC S YMME TR Y.

metry in their external form, and it is thought that if crys-
tallization took place without any disturbance of, or inter-
ference with, the most favorable circumstances for the
process, geometric symmetry of form would generally
result. In such cases crystallographic symmetry would be
denned by the relations of geometric symmetry which would
result. Crystallographic symmetry, however, exists with-
out being completely expressed in the external form. The
form is but one indication of the internal structure, the
physical properties are another. The physical character of
minerals have been very carefully studied, and in general
are found to be the same in all parallel directions. This
fact is believed to demonstrate a like internal structure or
molecular arrangement in these parallel directions. The
intimate relations between the physical character and the
faces and planes of a crystal lead to the conclusion that the
planes are but external expressions of the internal structure.
The faces are accordingly definitive because of their direc-
tion or angular position, and not because of their size or
distance from any assumed origin. Thus Figs. 2 and 3 are

FIG. 2.

FIG. 3.

equally symmetrical about a vertical or horizontal plane
passing through their centers. Again, a crystal may be a
crystallographic cube, though departing widely from the
geometric form, as in Figs. 4 and 5, provided it can be
shown that the three pairs of faces are alike ; this would
have to be done from the physical character of the faces, by
the kind of cleavage, or by optical means.

The important point to be grasped in regard to crystal-
lographic symmetry is that the symmetry in crystals about

CR YS TALLOGRAPHY.

FIG. 4.

FIG. 5.

lines or planes is one of direction and not of position. In
consequence of this fact any plane of a crystal may be con-
sidered as shifted parallel to itself without affecting the
crystallographic symmetry : hence
the corresponding symmetrical faces
of a crystal may be of very unequal
size and distance from the origin,
without disturbing the crystallograph-
ic symmetry. In general, for conven-
ience in the discussion and description
of forms it is better to consider
symmetry of position as well as of
direction ; in other words, we may
readily imagine the similar crystal
planes to be shifted in directions parallel to themselves
until a solid of geometric symmetry is produced.

Coordinate or Crystallographic Axes. — For studying and
classifying crystal forms, and for describing the position of
their faces, it is convenient to assume a system of coordinate
axes after the manner of analytical geometry. Different
sets of axes may, for this purpose, be assumed in crystals,
but that set is usually employed which enables expression in
the simplest manner of the position of the faces and the re-
lations between different crystalline forms. These consid-
erations have led to the selection of the axes of symmetry as
coordinate axes whenever the proper number of these axes
are present. If only one axis of symmetry is present, it is
employed in connection with two other assumed directions.
The axes chosen under the above conditions will differ in
their relations to each other in different crystalline forms.
They may intersect at right angles, giving orthometric forms,
or obliquely, giving clinometric forms. They may be all
equal in length, only two equal, or all unequal ; in some
cases they connect the centers of opposite faces, in others
the middle points of opposite edges, or the apices of oppo-
site solid angles. It should be remembered that the axes
usually assumed are not the only ones that could be em-
ployed, but are such as afford the simplest relations for the

LOCATION OF PLANES BY REFERENCE TO AXES. 7

descriptions of forms. The planes in which the coordinate
axes lie are called the axial or diametric planes. They cor-
respond to the coordinate planes of analytical geometry,
and divide the spaces within the crystal into eight solid
angles, and in one system where four axes are used the
space is divided into twelve solid angles.

Location of Planes by Reference to Axes. — The position of
any plane is known when its intercepts on the assumed axial
directions are given. If #, y, z represent the intercepts on
the respective axes of a plane, the position of the plane may
be expressed by x : y : z. The intercepts on the axes are

FIG. 6.

called the parameters of the plane. In general the axes are
lettered a, b, c, the vertical axis usually being represented
by c, that from right to left b, from front to rear by a ; as in
analytical geometry, the positions of the semiaxes on oppo-
site sides of the origin have opposite signs, the plus sign (+)
being applied to the halves in front, to the right, and above
the origin, and the minus sign ( — ) to the opposite halves,
Fig. 6. If definite lengths on the axial directions be
assumed as unit semiaxes, the parameters of any plane may
be expressed in these lengths. The unit semiaxes assumed
are those belonging to a particular crystal form of each

CR YS TA LLOGRA PH Y.

species. This particular form is called the unit form or
fundamental form. The unit form and the crystallographic
axes in the form are so chosen as to give the simplest ex-
pression for the parameters in the different crystals of the
species. If we let a, b, and c represent the unit axes, the
parameters x, y, and z of any plane may be written ma : nb :
re, which is the general expression for a face. The letters
m, ny and r are the ratios of the intercepts to the lengths of
the semiaxes and are called parameter coefficients. It is
evident that the intercepts of all parallel planes bear the
same ratio to each other, and since crystallographic sym-
metry is not affected by shifting a plane parallel to itself,
one of the intercepts of a plane may always be assumed
equal to unity, and the general expression for the face
becomes a : nb \ re. It follows from these considerations
that all parallel planes lying on the same side of the origin
have identical expressions ; parallel planes on the opposite
sides of the origin have the same expressions except as to
sign. Parallelism to any axis is represented by the sign in-
finity associated with that axial symbol. Thus a : oo b : oo c
indicates a plane parallel to two of the axes (b and c}. The
positions of a plane may also be expressed by using the
reciprocals of the parameters ; such reciprocals are termed
indices of the plane. Several systems of notation have beea
devised, the object in each case being to represent briefly
and clearly the position of the faces with reference to the
crystallographic axes. It is not practicable to here describe
the system of notation.

Definitions Pertaining to Crystals. — Cleavage is the quality
which minerals possess of splitting in certain definite
directions along plane surfaces. Cleavage is, of course, a
result of molecular structure, and a consideration of the
molecular arrangements in a mineral which would produce
crystal faces explains also the tendency to cleave in direc-
tions parallel to the faces. Every cleavage plane is a possi-
ble face of a crystal, and is due to the molecular arrange-
ment which produces faces. The more fundamental the
face the more perfect is the cleavage in that direction. The

^%€^e

CRYSTALLOGRAPHIC LAW. $.

natural planes of a crystal are called its faces ; those ob-
tained by splitting are called cleavage planes. As already
stated, the intersections of bounding planes are edges.
When an edge is cut off by a plane it is said to be replaced /
when the replacing plane is equally inclined to the original
faces the edge is truncated ; when the edge is cut off by
two planes equally inclined respectively to the original faces
it is bevelled.

Similar planes are those which can be expressed by the
same notation except as to signs. Similar edges are pro-
duced by the intersection of corresponding pairs of similar
planes. Similar angles are formed by the meeting of the
same number of corresponding similar planes. Planes which
have like positions with respect to the axes, except as to
direction from the center, are like planes.

Similar planes are always like planes ; thus the faces of
the cube are all like planes, but only the opposite faces are
similar planes.

Crystallographic Law — Law of Axial Ratios, or Rationality
of Parmeters or Indices. —From what has preceded we see that
symmetry is inherent in nearly all solid minerals and is part
of their nature. Crystallographic symmetry may be con-
sidered as a natural result of the molecular structure of a
mineral. Certain geometric relations have been found to
connect all the faces which belong to the crystals of any
one mineral.

The law governing these relations is known as the law of
axial ratios, or the law of rationality of parameters or indices.
It is an empirical law, but there are no known exceptions to
it, and it is the basis of mathematical crystallography. The
law may be stated as follows :

The ratios of the intercepts on the same axis by the different
planes of a crystal can only be o, oo, or rational numbers ; these
ratios can never be irrational. The law may also be expressed
thus : The position of all the planes of a crystal, located by their
intercepts, can always be expressed by numbers bearing a simple
ratio to the relative lengths of the axes of the unit form.

The geometric consequences of this law are the exclu-

I O CR YS TA LLOGRA PH Y.

sion from crystalline forms of all but the simpler types of
symmetry about an axis, binary, ternary, quaternary, and
senary. Regular solids of a higher order than the cube or
octahedron are thus excluded.

Constancy of Angles. — Since the planes of a crystal may
be shifted without affecting crystallographic symmetry —
provided each plane is moved parallel to itself — it follows
that the above law, the constant ratio of the intercepts for
the different planes of the crystal, also fixes a constant angle
between the intersecting planes, and we may write as a
second crystallographic law : that the angles of inclination
between like faces of the crystals of the same species are constant.

The unequal development of the faces of a crystal during
its growth has the same effect as the shifting of the planes
in directions parallel to themselves. This does not change
the ratios existing among their intercepts ; hence the angles
between the faces is constant, however much the faces may
vary in size in the different crystals of the same species.

All possible classes of crystalline forms can be deduced
mathematically, in the same manner that possible geomet-
rical polyhedrons are deduced, and the solution is less com-
plex, for the law of axial ratios excludes the higher orders
of symmetry. The possible crystalline classes are found,
under the law, to be thirty-two. Natural representatives of
all the possible classes are not yet known, though nearly all
that do not occur in nature have been produced in the
laboratory.

Zonal Relations. — The planes occurring in crystals are frequently ar-
ranged in belts extending around the crystal in different directions.
A zone includes a series of faces whose intersections are all parallel to
each other. An imaginary line through the center of the crystal, par-
allel to the common direction of intersection, is called the zonal axis.
All the planes which belong to the same zone are said to be tautozonal.
The zonal relation establishes the fact that the parameters of the faces
of the same zone have constant ratios for two of the axes.

(i) When the positions of two planes of a zone are known, the
direction of the zonal axis is determined. The position of a plane be-
longing to two zones is known when the directions of the zonal axes
-are known.

CRYSTALLINE SYSTEMS.

(2) The parameter relations between the faces of a zone make it
always possible to deduce some simple numerical relation between the
faces belonging to the same zone ; the relations so expressed give the
zonal equation. The determination of what planes belong in the same
zone is simple in principle, and not especially difficult in practice, but
the method to be pursued cannot be here explained.

We have seen that the symmetry of form of crystals can be ex-
pressed in their axial relations, according to the number and character
of their axes of symmetry. On this basis the possible groups of crystals
are generally classed in six systems, depending upon the number, rela-
tive lengths, and inclinations of their crystallographic axes.

CRYSTALLINE SYSTEMS.

I. The Isometric System. — This system has three equal
axes at right angles to each other, each axis being an axis of
quaternary symmetry. The simplest forms under this system
are the cube, Fig. 7, the regular octahedron, Fig. 8, and the

---,

FIG. 7,

FIG. 8.

regular dodecahedron, Fig. 9. The positions of the axes
are indicated in the diagrams. Either of these forms can be
assumed as fundamental and the others readily derived from
it ; for example, if in the cube planes be passed parallel to
one lateral axis and through the extremities of the vertical
and the other lateral axis, the octahedron will result, or pass
planes through the extremities of the semi-axes of the octa-
hedron, perpendicular to one axis and parallel to the other
two, and the intersections will form the edges of an enclosing
•cube. The faces of one or more of the above forms are

CK YS TA LLOGRA PH Y.

sometimes found in the same crystal, as shown at Figs. 10
and ii.

Besides the crystallographic axes of quaternary symmetry referred
to in this system, there are other axes of symmetry — six axes of binary

<^\ /

I>\

r " N

/ 1

FIG. 9.

FIG. 10.

FIG. ii.

symmetry, which connect the middle points of diagonally opposite
edges, and four axes of ternary or trigonal symmetry, which join the
vertices of opposite solid angles.

II. The Tetragonal System. — In this system there are
three axes, at right angles to each other; the two lateral
axes are equal in length, and the vertical axis is longer or
shorter. The simple forms in this system are the right
square prisms, Figs. 12, and 13, and the square octahedrons,
Figs. 14, and 15. The cross-sections of these forms, perpen-
dicular to the vertical axes are squares. As mentioned in
the preceding system these forms are derivable from each
other. In this system the vertical axis is an axis of quater-
nary or tetragonal symmetry. The lateral axes may join the
centers of opposite faces or of opposite vertical edges. The
relative lengths of the vertical and horizontal axes may
vary, depending upon whether a long or short octahedron
be assumed as the unit form. The selection of this form
depends upon considerations already mentioned.

III. The Hexagonal System. — This system has two divi-
sions: (a) Hexagonal, (b) Rhombohedral. (a) In the hex-
agonal division there are four axes, one vertical and three
lateral axes ; the lateral making angles of sixty degrees
with each other, and the vertical axis being perpendicular

CRYSTALLINE SYSTEMS.

to the plane of the lateral. The vertical axis is an axis of
senary symmetry, while the lateral axes are of binary sym-
metry. The lateral axes are in sets of three each, the axes
of each set being equal in length, (b) In the rhombohedral

•:^

IG.

FIG. 13.

FIG. 14.

FIG. 15.

division the arrangement of certain planes around the verti-
cal axis are alternate in the upper and lower halves of the
crystal. This arrangement leaves the vertical axis an axis
of ternary or trigonal symmetry instead of hexagonal, with
three horizontal axes of binary symmetry. Some of the
simpler forms of the hexagonal division are shown in Figs.

CRYSTALLOGRAPHY.

16, 17, and 18; Fig. 19 shows the possible positions of the
lateral axes in the hexagonal division; Figs. 20 and 21 show
two forms of the rhombohedral division.

\s '

FIG. 16.

FIG. 17.

FIG. 18.

FIG. 19.

FIG. 20.

IV. The Orthorhombic System.— This system has three
rectangular axes, no two of which are of the same length.
The simpler forms of the system are the right rectangular
prism, Fig. 22, the right rhombic prism, Fig. 23, and the
rhombic octahedron, Fig. 24. The planes of these three
forms, as well as of others not mentioned, are sometimes
found in the same crystal.

In this system each axis is an axis of binary symmetry.

CRYSTALLINE SYSTEMS.

V. The Monoclinic System.— This system has a vertical
and two lateral axes, no two being of the same length. One
lateral axis is oblique to the vertical axis, and the other

^^ I

u \=

FIG. 21.

FIG. 22.

i
i

^_J

-i —

FIG. 23.

FIG. 24.

lateral axis is perpendicular to the plane of the vertical and
oblique lateral axis. The simple forms in the system are
the rhombic prism, Fig. 25, the oblique rectangular prism,
Fig. 26, and the right rhomboidal prism. As in the other
systems, the planes of different forms sometimes occur hi
the same crystal.

CR YS TA LLOGRA PH Y.

In different species belonging to this system the relative
lengths and inclinations of the axes vary.

The system has only one axis of binary symmetry.

VI. The Triclinic System. — This system has three axes of
unequal length, each being oblique to the plane of the other

-i — .f-

:- i —

FIG. 25.

two. A simple form is the oblique rhomboidal prism. In
different species belonging to this system, as in the preced-
ing, both the relative lengths and inclinations of the axes
vary.

There is no axis of symmetry in this system, the symmetry existing
only with respect to a point which is a center of symmetry. In this
case, if an imaginary plane be passed through the center parallel to one
of the faces and the portion of the crystal on one side of the plane be
thought of as rotated 180° about a line perpendicular to the plane and
passing through the center, the two halves of the crystal would then be
mirror images of each other across the plane. The center of symmetry
of the polyhedron is also a center of symmetry for every polygonal
figure formed by the intersection of the faces of the crystal with a plane
passing through the center. Every such polygon rotated in the plane
about the center occupies congruent positions after every turn of 180
degrees.

It will be observed that the above systems can be grouped into three
classes, depending upon the number of their principal axes of sym-
metry. A principal axis of symmetry has already been defined as one
that is of the third or higher order of symmetry. This, as a general
statement, is correct, and any crystal which has trigonal symmetry has
a principal axis of symmetry, but an axis of trigonal symmetry is not
necessarily a principal axis of symmetry in a system where there are
axes of higher symmetry. Thus, in the cube (isometric), the three axes
of tetragonal symmetry connecting the middle point of opposite faces

CRYSTALLINE SYSTEMS. 1 7

are principal axes, while the four axes of trigonal symmetry connecting
diagonal opposite angles are secondary axes in this system.

The groups of the above six systems according to the number of
their principal axes are :

i st. Those without a principal axis of symmetry. Under this group
are included the Triclinic, the Monoclinic, and the Orthorhombic. The
first is without linear symmetry, and the other two have only binary
symmetry.

2d. Those with one principal axis of symmetry. Under this group
are the Hexagonal and Tetragonal ; the principal axis in the first being
one of senary symmetry, and in the second of quaternary.

3d. Those with three principal axes of symmetry. The Isometric is
the only system in this group; the three principal axes of the system
being of quaternary symmetry.

Crystal Symmetry about Planes.— In grouping the crystal forms ac-
cording to their axial relations, only symmetry about lines and points
has been described, but it is evident that symmetry about lines involves
symmetry with reference to planes. The crystallographic axes assumed
in the first four systems of crystallization result from the intersection of
planes of symmetry. In the Monoclinic system there is one axis of
binary symmetry, which must accordingly be perpendicular to a plane
of binary symmetry. In the Triclinic system, there being no axis of
symmetry, there is no plane of symmetry. Axes of symmetry are said
to be like or equivalent when they are of the same order of symmetry
and of the same length. Planes of symmetry are like when they divide
the perfect form into identical halves. In general a plane which con-
tains two or more like axes of symmetry is a principal plane of sym-
metry, the others are secondary planes; this statement must be limited
in the isometric system, so that the like axes shall be those of the
highest symmetry. Principal axes of symmetry are normal to principal
planes of symmetry, and secondary axes to secondary planes. From
the above definition it is seen that in the isometric system the assumed
coordinate or crystallographic axes are the principal axes formed by the
intersections of the principal planes of symmetry. In the tetragonal
system these coordinate axes are formed by the intersection of one
principal plane of symmetry, with two secondary planes of symmetry,
all at right angles to each other.

In the Hexagonal the assumed axes are formed by the intersection of
one principal plane with six secondary planes meeting at angles of 30°.

In the Orthorhombic system the coordinate axes are formed by the
intersection of three secondary planes, all at right angles to each other.
In the Monoclinic system one of the crystallographic axes is the
normal to the plane of symmetry; the other two are in that plane and
so chosen as to give greatest convenience : the positions of these latter
are usually taken as previously stated.

CR YS TA LLOGRA PH Y.

In the Triclinic system there are neither planes nor axes of sym-
metry, and the choice of coordinate axes is arbitrary.

Hexagonal symmetry, of necessity, includes trigonal symmetry, and
tetragonal symmetry includes binary symmetry.

Crystal Forms — Closed and Open Forms. — A form in crystallography in-
cludes all of the like faces in the crystal — like faces, as already denned,
being those which have like positions with reference to the axes, except

FIG. 27.

FIG. 28.

FIG. 29.

FIG. 30.

as to their direction from the origin. If all the faces of the crystal are
like, they constitute a closed form ; that is, the enclosed solid is entirely
bounded by like faces. If the like faces do not enclose the solid, the.

DISTORTIONS IN CRYSTALS. ig

form is open. There are no closed forms in the Monoclinic and Tri-
clinic systems — that is, no crystal forms in which all the faces are like ;
in the other four systems there are closed forms, those in which the
crystal faces are all alike. The maximum number of like faces in the
closed forms of these systems varies with the symmetry of the system.
The number is 48 in the Isometric, 24 in the Hexagonal, 16 in the
Tetragonal, and 8 in the Orthorhombic, which are shown at Figs. 27,
28, 29, and 30. The opposite pairs of the faces in these forms are simi-
lar planes.

Holohedral and Hemihedral Forms. — When a crystal is contained by all
the faces necessary to the complete symmetry of the system, to each
face there is a parallel similar face, the total number being even and
never less than six ; such forms are holohedral. There are occurring
forms in which there are only one-half or one-fourth the number of
faces necessary to complete symmetry; these are called respectively
hemihedral and tetrahedral forms.

These forms, other than the holohedral, may be considered as pro-
duced by the suppression of one-half or three-fourths of the planes of
the complete forms, and the extension of the remaining planes until
they intersect. The surviving and suppressed planes in these forms are
always those which fulfill certain definite conditions. One-half or
three-quarters of the planes of a complete form, arbitrarily chosen for
suppression or extension, will not produce the other forms. The sym-
metry of the hemihedral and tetrahedral forms is of a lower order than
that of the complete forms in the same system. The symmetrical ele-
ments of the lower forms are less in number, but identical with the sym-
metrical elements in the holohedral forms, and well-defined geometrical
laws connect the forms with each other.

DISTORTIONS IN CRYSTALS.

It has been already stated that crystallographic symmetry is not
always accompanied by geometric symmetry. For the purpose of de-
scribing the systems, it is simpler to consider the ideal forms as we
have done, but the perfect forms of the systems seldom occur in nature.
The departures from the ideal forms which are due to the unequal
development of the faces of the crystal and to the unequal dimensions
of like axes are called distortions.

Distortions render more difficult the identification of forms, but the
constancy of interfacial angles and the identical characters of like faces
are the means by which the difficulty is overcome. For example, the
perfect cube is not generally met with in nature; if lengthened or
shortened in the direction of one axis, it assumes the form of a right
square prism ; if varied in the direction of two axes, it becomes a rect-
angular prism (see Figs. 4 and 5). In the first case its geometric form

CR YSTALLOGRAPHY.

would place it in the tetragonal system, in the second case in the
orthorhombic. The physical similarity of its faces, or equal cleavage in
the three rectangular directions, would place it in its proper system.

Other forms more complex than the cube have distortions not so
readily recognized, but the considerations above mentioned, together
with a general familiarity with the more common distortions, usually
serve to place the specimen under consideration. The faces of crystals
are frequently not plane surfaces: they may be either striated or curved,
These imperfections in crystals may result from oscillatory combinations
or twinning, to which reference will be made. Curvature is also some-
times due to mechanical causes, as is thought to be the case in tourma-
line, or to the molecular conditions of crystallization, as in the diamond.

MULTIPLE CRYSTALS.

The crystal individuals thus far considered have all been polyhe-
drons, whose interfacial angles are less than 180°. Such is always the
case with the distinct individual. On many crystalline surfaces re-
entering angles are found which always indicate a combination of two
or more individuals. These groups of crystals conform to certain defi-
nite laws. A few of the important groups will be briefly referred to.

Parallel Grouping. — The simplest cases of parallel grouping consist
of similar crystals so arranged that the line joining their centers coin-
cides with a crystallographic axis or is parallel to it. These forms are
illustrated in Figs. 31, 32, 33. If two cubes were joined as are the forms
in Fig. 31, there would result a right square prism which would appear

FIG. 31.

FIG. 32.

FIG. 33-

as a single crystal. The re-entering angles denote the junction of sepa-
rate individuals in parallel growth.

If the width of the alternating planes is very small, there results what

MULTIPLE CRYSTALS. 21

appears to be a single crystal with striated faces ; this arrangement of
planes in a surface is termed oscillatory combination ; there is an ap-
proximation to this in Fig. 33.

Often complex crystalline forms result from parallel growths. Many
of the delicate dendritic forms are thus brought about. In these par-
allel groupings the crystal as a whole is symmetrical with reference to
some plane which is also a plane of symmetry for each individual form.

Twin Crystals. — In twinning combinations two individual crystals or
two halves of the same crystal are joined so as to have either a common
crystallographic direction or crystallographic plane, but the parts are
not in completely parallel positions. The two crystals or two halves of
the same crystal are accordingly symmetrical with reference to a plane
which is not a plane of symmetry for the individuals, and this is the
main distinction between the parallel grouping and the twinning posi-
tion.

The relation of the parts in a twin crystal may be understood from
Fig. 34, which shows a regular octahedron divided into halves by a plane
parallel to an octahedral face ; in the figure the front half has been
rotated through 180° about an axis normal to the plane.

Contact Twins. — The form of structure shown in Fig. 34 is an exam-
ple of what is designated as contact twins ; this particular form is also
termed a hemitrope crystal. Another form of contact-twinning is-
shown at Fig. 35.

Penetration Twins are those in which the twinning crystals are not
joined along a plane, but more or less completely penetrate each other.
Such forms are shown at Figs. 36, 37, and 38.

Repeated Twinning. — A third individual may be added to one of the
two crystals of a twin according to the same law that joins the first two,
thus causing repeated twinnings, giving rise to trillings, fourlings, five-
lings, etc. The variations of form resulting from the different applica-
tions of the twinning laws are very numerous, and further reference to
them cannot be here undertaken.

Pseudomorphs. — Minerals generally belonging to one crystalline sys-
tem are sometimes found to have the form of another. Such crystals
are called pseudomorphs. They are thought to result sometimes
through a change of composition in the mineral, or else the pseu-
domorph is formed by the filling of a cavity left by the removal of a
crystal of another form.

ISOMORPHISM.

Some of the compounds of certain elements crystallize
in the same form ; and not only this, but one of these ele-
ments may replace the others in a crystal without destroying

CR YS TA LLOGRA PH Y.

FIG. 34.

FIG. 35.

FIG. 36.

FIG. 37-

FIG. 38.

CRYSTALLINE AGGREGATES. 2$

the form ; such elements are said to be isomorphous. Cal-
cium, magnesium, and iron are notable examples.

CRYSTALLINE AGGREGATES.

Most mineral masses are not composed of distinct crystal
forms, but consist of an aggregation of imperfect crystals.
Sometimes the aggregation is wholly irregular, and some-
times more or less regular. There are many varieties of
aggregates. The planes between the individuals in aggre-
gates are simply planes of fracture ; when the fracture gives
rise to a coarse rough surface it is called hackly ; when it
gives rise to a smooth flat surface it is called even; and when
it gives rise to curved surfaces, having shell-like appear-
ances, it is called conchoidal. Some of the more important
and common aggregates are :

1. Dendritic. — Composed of small crystals arranged in
such a manner as to give a tree-like appearance, as in native
gold and silver. The term is also frequently used for simi-
lar forms, whether due to crystals or not, as to those pro-
duced by the oxide of manganese

2. Drusy. — Composed of many small crystals implanted in
a finer ground-mass, giving a very rough surface.

3. Columnar or Fibrous. — Composed of columnar or
fibrous individuals, sometimes aggregated so as to give the
appearance of a heterogeneous mixture, sometimes forming
star-like groups, and sometimes giving rise to globular
forms. These globules are sometimes arranged so as to
give rise to forms resembling bunches of grapes, and there-
fore called botryoidal. If the globular masses be nearly
hemispheres, the form is called mammillary.

4. Lamellar. — Consists of plates or leaves. If the plates
are very thin and easily separable, the structure is foliated,
especially if the plates are minute scales. The varieties of
mica well illustrate this structure.

5. Granular. — Composed of grains, either coarse or fine ;
sometimes so fine that they cannot be detected by the
microscope, then said to be cryptocrystalline ; sometimes of

24 CRYSTALLOGRAPHY.

the size of peas, giving rise to pisolitic forms ; sometimes of
the size of the roe of fish, giving rise to oolitic forms ; some-
times flattened like lenses, giving rise to lenticular forms.

6. Concretions. — Vary in shape from simple spherical
masses to very grotesque aggregations, but always rounded
in form. The more perfect forms often consist of concentric
layers. The individual grains present in the granular for-
mations are often concretions, as in the oolitic. One form of
concretion, intersected by cracks which have been filled by
foreign matter, is called a septarium or turtle-stone.

7. Stalactitic. — Cylindrical or conical in shape, composed
of fine grains, fibers, or lamellae deposited from solution.

7. Stratified. — Composed of layers, sometimes of the same
color throughout, sometimes of different colors, giving
rise to banded forms; the layers are formed by successive
deposition.

8. Geodes. — Forms resulting from incomplete filling of a
cavity by a mineral, the interior often being covered witk
crystals.

*/t«£

CHAPTER II.

PHYSICAL AND CHEMICAL PROPERTIES OF MINERALS,
PHYSICAL PROPERTIES OF MINERALS.

THE properties of minerals which are useful in deter-
minative mineralogy are of two kinds, viz., physical and
chemical. The more important physical properties and
those which can be most readily observed are (i) luster, (2)
color, (3) hardness, (4) streak, (5) malleability, (6) taste, odor,
and feel, (7) specific gravity.

Luster. — There are two general classes of luster, (i)
metallic, (2) unmetallic. Metallic luster includes semi-metal-
lic ; the name of the luster indicates the nature in each case.
Unmetallic luster includes (i) vitreous, (2) resinous, (3)
pearly, (4) greasy ; again, the name indicates the character
in each case.

Color. — The mineral kingdom displays a great variety of
colors. Colors are generally important only in the case of
pure specimens. Some of the more common mineral colors
are red, yellow, white, gray, brown, and black. A mineral
is said to be opalescent when a milky, pearly, or glistening
reflection is obtained from it ; phosphorescent when it emits
light by friction or by being heated ; iridescent when it gives
rainbow colors from the interior. When a mineral reflects
prismatic colors upon being turned in the light it is said to
give a play of colors.

Streak. — This is the name given to the color of the pow-
der obtained by abrading the mineral, or to the color of the
streak obtained by drawing it across a small plate of
white porcelain.

26 PHYSICAL AXD CHEMICAL PROPERTIES OF MINERALS.

Hardness. — The hardness of minerals is determined by the
use of a file. Care must be exercised in selecting a portion
of the specimen to be rubbed with the file, as the true hard-
ness will not be obtained upon very acute angles, or upon
parts altered by exposure. The sound emitted as the file is
drawn across the specimen is often as good a guide as the
ease with which the specimen is abraded. For purpose of
comparison, the following scale of hardness is adopted:
i, talc ; 2, rock salt ; 3, calcite ; 4, fluorite ; 5, apatite ; 6, ortho-
clase ; 7, quartz ; 8, topaz ; 9, sapphire ; 10, diamond.

Malleability. — When portions of a mineral can be flat-
tened under the hammer it is said to malleable.

Brittleness. — When a mineral crumbles under the applica-
tion of a force it is said to be brittle.

Flexibility. — When a mineral, or part of it, will bend and
remain bent upon the relief of the force it is said to be
flexible ; when it will return to the original position upon
the relief of the force it is said to be elastic.

Sectility. — Refers to the property possessed by some
minerals of being cut into thin slices without crumbling, but
which crumble under the hammer.

Odor. — Odors are developed by moisture, heat, or acids ;
only a few common ones need description :

Argillaceous Odor. — That of moist clay, developed when a
clayey mineral is breathed upon.

Alliaceous Odor. — That of garlic, developed when the
arsenical minerals are heated by friction or by the blow-
pipe.

Sulphurous Odor. — That of burning sulphur, developed by
heating some of the sulphides in air, or by burning sulphur.

Feel. — Some minerals have characteristic greasy, rough,
or smooth feel.

Specific Gravity. — The specific gravity of a substance is
the ratio of the weight of a given volume of the substance
to the weight of an equal volume of water at a standard
temperature. One of the simplest ways to determine
specific gravity is to obtain the weight of a small piece of
the mineral, and then to obtain the weight of this same

CHEMICAL PROPERTIES OF MINERALS. 2/

piece immersed in water. These observations are sufficient
to determine the specific gravity for ordinary purposes.
There are specially contrived balances for taking these
weights.

For porous minerals the specific gravity is obtained by
the use of a bottle of standard capacity by weight. A
known weight of water is poured from the bottle and then
the powdered mineral is added until the volume of the
water is the same as before. From the original weight of
water, from the weight of the water removed, and from the
weight of the water with the mineral added the specific
gravity can be obtained.

This method is of course equally applicable to compact
minerals.

For minerals soluble in water a liquid must be used
which will not dissolve them and whose specific gravity is
known.

The physical properties are of great importance in deter-
minative mineralogy and many common species can be
approximately determined by them.

Tables to assist in the determination of the minerals
described are included in the text. These tables have been
prepared by classifying the minerals according to luster,
subclassifying under luster according to color, color of
streak, or hardness. Other physical properties are tabu-
lated, and a column of remarks noting characteristics, not
elsewhere included, is added.

/'. •/

CHEMICAL PROPERTIES OF MINERALS.

£/ ,/ tnr

If a specimen cannot be fully determined by the physical
tests, the chemical properties must be considered. While
the chemical tests will often afford a ready means for
determining a specimen, it is always better to consider
physical characters first.

For examining the chemical properties of minerals the
following facilities are usually to be had in the laboratory :
hammer, anvil, steel mortar, agate mortar, forceps, open and

28 PHYSICAL AND CHEMICAL PROPERTIES OF MINERALS*

and closed tubes, charcoal, blowpipe, platinum wire, fluxes,
and reagents.

Hammer and Anvil. — These are for removing small pieces
from the specimen for subsequent treatment. By holding
the specimen on the anvil a sharp blow properly adminis-
tered will usually separate a suitable fragment.

Steel Mortar. — This is used for powdering the fragment,
and the mortar should always be placed on the anvil for
use. The agate mortar and pestle are used for further pul-
verization by friction of the power obtained from the steel
mortar.

Forceps. — Any forceps provided with platinum tips will
answer ; but those so made that the tips will press together
of themselves will be found most convenient. The forceps
are used in connection with the blowpipe for fusing, or for
detecting a volatile ingredient, which may yield an odor or
color the flame. Only a small thin sliver of the specimen
should be used, and it should be held so as to project well
beyond the point of the forceps. Minerals easily reduced to
the elementary state should not be heated in contact with
the forceps, and as a rule it is well not to use the forceps
with those having metallic luster.

Charcoal. — Charcoal is used as a support upon which
various bodies are heated. The heating may be for the
purpose of fusing, for volatilizing, or for the production of
a sublimate. The odor from the volatilized body and the
color of the sublimate, near and at a distance from the
assay, are often characteristic. An infusible and non-volatile
residue can often be subjected to additional treatment.

Besides serving as a support as above indicated, the
reducing power of the charcoal is often made use of to
deoxidize certain bodies, as metallic oxides. The production
of sublimates is often facilitated by the use of fluxes. Easily
reducible compounds, as those of lead, zinc, arsenic, and
antimony, should always be heated on charcoal and not in
the forceps.

Open Tubes. — These are used to heat the mineral in con-
tact with air. A small fragment, or better some of the

CHEMICAL PROPERTIES OF MINERALS. 2$

powdered mineral, is put in the tube and the tube heated,
being held as highly inclined as possible; the result to be
expected will of course depend upon the particular mineral,
and the observations to be noted are indicated in the tabular
description of the species.

Closed Tubes. — These are used for heating the mineral
out of contact with air and for making tests with liquid
reagents. Only a very small quantity of the mineral must
be used except in cases particularly specified, and only a
small quantity of acid is necessary. Attention is called to
the phenomena to be observed, in the tables above re-
ferred to.

Blowpipe. — The blowpipe is simply a bent tube, with a
very narrow orifice, provided with a platinum tip which can
be removed and cleaned. Only very small pieces or amounts
of mineral must be used before the blowpipe.

In using the blowpipe it is necessary to blow and breathe
at the same time, for results can generally be accomplished
only by continued application of the flame for some time.
This accomplishment is readily acquired by practice. Care
must be taken that the flame be well protected from draft
or anything which would cause flickering. The flame
should be colorless, for the characteristic colors of many
minerals are readily developed before the blowpipe.

Platinum Wire. — This is used for facilitating the action
of the fluxes on the minerals and for affording opportunity
for observing the action ; such action frequently gives
characteristic colors. In general the manner of using the
wire is as follows : Twist it into a small loop at the end, heat
it, and dip it into the flux, and fuse to a clear bead, then
into the powdered mineral, and fuse again ; repeat the opera-
tion and observe carefully the fused mass, which is called
a bead. The blowpipe may or may not be used in heating
the beads; in some cases the beads have one color in
the oxidizing flame and another in the reducing flame, as
described in the tables.

Fluxes. — The common fluxes for making beads are borax,
sodium borate, salt of phosphorus, phosphate of sodium and

30 PHYSICAL AND CHEMICAL PROPERTIES OF MINERALS.

ammonium, and soda, sodium carbonate. They owe their
value to the fact that they dissolve or combine with metallic
oxides, giving characteristic colors ; the mineral should be
roasted before making a bead, so that the oxide will be
formed if it is not already present.

Soda is a very valuable flux for decomposing the
metallic compounds.

Reagents. — The more common and useful reagents are
sulphuric, hydrochloric, and nitric acids, ammonia, am-
monium sulphide, potassium ferrocyanide, and ammonium,
oxalate.

SOME IMPORTANT AND COMMON MINERAL TESTS.

(These should be learned at once by the student.)

Before the Blowpipe — Copper. — Copperminerals moistened
with hydrochloric acid give the flame an azure-blue color ;
heated alone the flame is colored green.

Iron. — Minerals containing iron are converted into mag-
netic oxide in the reducing flame; sometimes soda is re-
quired.

Lead. — Lead minerals heated on charcoal with soda give
a yellow oxide coating on charcoal and leave a lead globule.

Zinc. — Important zinc ores when heated on charcoal
give a coating of oxide, yellow while hot, but white on

cooling.

Open-tube Tests. — Arsenic. — The common arsenical com-
pounds give a white sublimate of arsenious oxide on the
tube, an alliaceous odor, and an acid reaction with litmus
paper.

Sulphur. — Sulphides give an odor of sulphurous oxide
and an acid reaction.

Closed-tube Tests. — Arsenic. — The common arsenic com-
pounds in a closed tube give a coating of arsenic, a coating
of red and yellow orpiments if sulphur be present, and emit
an alliaceous odor.

Carbon. — Carbon mixed with a nitrate and heated will
deflagrate.

MISCELLANEOUS TESTS. 3 1

Copper. — To test for copper treat with nitric acid and add
excess of ammonia ; if copper be present, a blue solution is
given ; copper sulphides must first be well roasted.

Calcium. — To test for calcium treat with hydrochloric
acid, neutralize with ammonia, add a soluble oxalate, and
calcium oxalate will fall.

Iron. — To test for iron treat with hydrochloric acid, add
potassium-ferrocyanide, and a blue precipitate will be
formed.

Mercury. — To test for mercury mix a salt-spoonful with
twice its volume of soda, heat, and globules of mercury will
be deposited on the cool sides of the tube.

Water. — To test for water put the powdered mineral in
the tube, heat the latter held in a nearly horizonal position ;,
if present, water will be deposited on the cool sides of the
tube.

MISCELLANEOUS TESTS.

Carbonates. — Treated with hydrochloric, nitric, or sul-
phuric acid, carbonic acid gas escapes with effervescence ;
decomposition will sometimes take place if a drop is put on
the mineral in mass; but in some cases the mineral must be
pulverized ; in others the application of heat is necessary.

Sulphates. — With few exceptions, heated with hydro-
chloric or nitric acid treated with a soluble salt of barium,
yield a white precipitate of barium sulphate.

Nitrates: — Heated on charcoal deflagration takes place;
or better, heated in a tube with powdered charcoal deflagra-
tion occurs.

Sulphides. — Heated with soda on charcoal, moistening
assay so obtained and placing on a silver plate, the latter will
be tarnished if sulphur be present. The sulphides heated
with nitric acid often give a mass of sulphur floating on the
surface of the acid ; sulphides roasted in air give a sulphur-
ous odor.

CHAPTER III.

DESCRIPTIVE MINERALOGY.

NATIVE ELEMENTS.

Diamond, C.

Isometric. — Commonly in octahedrons, but often in more
complex forms, faces frequently curved.

The diamond varies from colorless specimens through
various shades of yellow, orange, red, green, blue, brown,
and sometimes black. Transparent when white, dark
varieties translucent to opaque. The luster is adamantine to
greasy. H. = 10. G. = 3.516-3.525 in distinct crystals.

Bort is a rounded variety of diamond, with rough exterior
and lacking distinct crystalline structure ; its hardness is
greater than the ordinary form (distinct crystals), but its
specific gravity less.

Carbonado, or black diamond, is massive, but with crys-
talline structure, sometimes granular to compact ; its specific
gravity is sometimes as low as 3.01, but it excels in hardness
all other forms. It is found mainly in Brazil.

The composition of the diamond is essentially pure
carbon, but the different specimens of the gem which have
been tested by combustion leave a small quantity of ash,
showing impurity varying from one-twentieth of one per
cent to two per cent. In this ash, silica and the oxide of
iron have been detected. The black diamond leaves the
greatest amount of ash.

The diamond heated to a very high temperature with
the air excluded is converted into a black mass resembling
graphite or coke, without loss of weight ; highly heated in
the air it is completely oxidized (except the small quantity
of ash) yielding CO,.

UNI V ft ASH' V OF

Mf»*TMKMT or CIVIL CNQI M cam

•KRKCLKY, CALIFORNIA

NATIVE ELEMENTS. 33

The diamond, until the discovery of the South African
fields, was found mainly in alluvial deposits of gravel, sand,
and clay, often associated with gold, platinum, quartz, topaz,
garnets, corundum, tourmaline, and other accessory miner-
als. The frequent presence of itacolumite in the diamond
regions, and the fact that diamonds have been found in this
rock in Brazil, have led to a rather general belief that ita-
columite (flexible sandstone) is the principal original
diamond-bearing rock. The occurrence of diamonds in
place in the South African mines shows that such is not the
case. In these fields the diamonds are found associated and
imbedded in a highly basic, brecciated volcanic rock, and it
is still undetermined whether the diamonds were present in
the original rock from which the breccia came .or whether
they were produced by the action of the volcanic products
upon the carbonaceous material which is found in the region
as shale. Prof. H. C. Lewis, who gave able consideration
to the subject, advocated the latter theory.

The South African mines have yielded more diamonds
than all the previous production of the world. Ninety-five
per cent of the world's yearly supply of diamonds is now
obtained from these mines, the remainder coming almost
entirely from Brazil, India, and Borneo. A few diamonds
have been found in the United States and Australia ; those
obtained in this country have been found mainly in the
Southern Alleghanies from Virginia to Georgia, or in the
Sierra Nevada or Cascade ranges in Northern California
and Oregon.

Graphite, Plumbago, Black Lead.

Hexagonal — In six-sided laminge, commonly imbedded in
foliated masses. Granular to compact and earthy.

Graphite is carbon with from one to five per cent ot
mechanical impurities, generally oxides of iron, manganese,
and silicon. It varies in color from iron-black to steel-gray ;
streak black, shining; luster metallic. H.= i to 2. G. — 2.2^.
Makes dark streak on paper and has greasy feel. It is infu-

34 DESCRIPTIVE MINERALOGY.

sible both alone and with reagents and is not acted upon by
acids. Combustible only at very high temperature. Defla-
grates when thoroughly mixed with niter and heated in a
closed tube. In appearance greatly resembles molybdenite
(MoS), but this gives off sulphurous fumes before the blow-
pipe and is acted upon by nitric acid.

Graphite occurs as scales and grains, nodular masses,,
and in beds, generally in the crystalline rocks. It is found
in New York, Pennsylvania, Massachusetts, Connecticut,,
Rhode Island, New Jersey, North Carolina, South Carolina,
Colorado, and California, and in several other states. It has,
been mined in New York, Massachusetts, Connecticut*
California, and North Carolina. The Ticonderoga mine in.
New York and the Herron mine in North Carolina are the
most important.

Ceylon, Bavaria, and Siberia supply most of the foreign-
graphite and much that is used in this country also. The
English deposit at Borrowdale long furnished a superior
quality of graphite, but is now nearly worked out.

Graphite is largely used for the manufacture of lead-
pencils, being ground up, and generally mixed with some
cementing material and solidified by pressure. Fine clay is.
used in the harder pencils. It is also largely used as a lubri-
cant for machinery, for coating objects to be electrotyped,
for polishing stoves and other iron- work, as a paint for
smokestacks, boilers, etc., and for making crucibles ; for the-
latter purpose being mixed with clay.

Native Sulphur, St

Orthorhombic. — Most common form, right rhombic acute
octahedron. Also various modifications of this form, and
massive.

Sulphur when pure is of a clear yellow color, frequently
somewhat translucent, but sometimes opaque. Its streak is.
yellow, sometimes tinged reddish or greenish ; it is very
fragile and breaks with conchoidal fracture, vitreous or-
resinous luster. G. = 2.1. H. = 1.5 to 2.5. Readily combusr-

NATIVE ELEMENTS. 35

tible, burning with blue flame and producing suffocating,
acrid fumes. In closed tube wholly volatilizes and deposits
on cool part of tube.

The native form is most generally met with as masses or
small grains disseminated in other minerals, or as fine yellow
powder lining cavities. It often contains clay or bitumen
and is sometimes colored orange-yellow by selenium sul-
phide. The largest deposits of sulphur are found in recent
sedimentary strata associated with gypsum or allied rocks,
or in regions of extinct or active volcanoes ; nearly all active
volcanic regions yield it in some abundance. The greater
proportion of the supply of native sulphur is obtained from
the volcanic districts of Sicily. It is usually purified from
earthy impurities by fusion before shipment to the world's
market.

Sulphur deposits are found in many places in the United
States both in the East and the West. Those in the Eastern
States are too small to be of industrial importance except cer-
tain beds in Louisiana, which are, in places, over one hundred
feet thick and contain a large quantity of pure sulphur, but
they are four or five hundred feet below the surface. The
difficulty of mining these deposits has thus far proven so
great that they have yielded only a small quantity of sul-
phur. Deposits in the West are numerous and occur in Cali-
fornia, Nevada, Utah, Wyoming, New Mexico, and Arizona
Those most important as a source of sulphur are at the Rab-
bit Hole mines, in Humbolt County, N. W. Nevada. These
at the present time furnish the greater proportion of the
sulphur mined in the United States. The mines near
Beaver, Utah, are next most productive. Sulphur is very
generally deposited around springs whose waters contain
hydrogen sulphide in solution, especially in volcanic regions.
Immense deposits of sulphur are known to exist in the crater
of Popocatepetl. The sulphur consumed in the United
States comes mainly from Sicily, which also furnishes the.
greater proportion of the world's supply.

36 DESCRIPTIVE MINERALOGY.

Native Gold.

Isometric. — Octahedrons and dodecahedrons, but these
are rarely found.

Gold has a yellow color in mass, but when reduced to
very fine powder it is ruby-red. It is very ductile and mal-
leable. H. = 2.5 to 3, nearly as soft as lead. G. = 19 to 19.3.
Fusing-point slightly above 2000° F. Not acted upon by
any of the common acids ; dissolved by nitro-muriatic acid ;
does not oxidize in the air.

Gold is seldom found pure. It is most commonly alloyed
'with silver, sometimes with copper, iron, rhodium, and bis-
muth. It is occasionally found combined with tellurium.
The silver present in the gold varies from a fraction of a
per cent to one-third of the whole. An amalgam of gold
•and mercury has been found in Colombia, S. A., and in Col-
orado. The native gold of California averages about 88 per
•cent of gold, the remainder being mostly silver. The native
alloys with silver are much lighter in color than gold and
occasionally nearly silver-white.

Iron and copper pyrites may closely resemble gold in
color and have, by the inexperienced, been mistaken for it ;
for this reason they are sometimes called "fools gold."
These minerals are brittle and give off sulphurous fumes
when roasted in the air, which at once distinguish them from
gold.

Gold occurs principally in two ways: i. In quartz veins
intersecting metamorphic rocks, frequently associated with
ores of other metals. 2. As grains and nodules in the gravel
and sands of the rivers and valleys of auriferous regions.
The deposits in the second case result from degradation of
the veins. The quartz veins most commonly occur inter-
secting metamorphic talcose, chloritic and argillaceous
schists, less frequently in diorites and porphyries.

The gold occurs irregularly distributed throughout the
quartz of the vein, in strings, scales, and grains, and is often
invisible to the naked eye. The most perfect crystals and
largest masses generally occur in the cavities of the quartz.

NATIVE ELEMENTS. 37

The most common minerals accompanying the gold in the
vein-stuff are the sulphides of iron, copper, lead, and zinc
and the red oxide of iron. The iron pyrite exceeds in quan-
tity all the other minerals and is usually auriferous, the
others frequently so.

The quartz of the veins, for some distance below the sur-
face, is often cellular and porous owing to the alteration and
removal of the associated minerals by atmospheric agencies.
The gold that was present in the removed mineral is thus
frequently left in strings or scales in the cavities of the
quartz. This weathered portion of the vein is more easily
mined and the gold more easily obtained from it than from
the unchanged portion. In quartz mining the gold is either
obtained from the quartz or from the associated minerals ;
the pyrite of a gold region is often worked as a gold ore, as
is also the galenite.

The method of obtaining the gold from the sands and
gravels constitutes "alluvial washing"; in California called
placer mining. The origin of these deposits is given in
Geology. The gold is obtained from the deposits by taking
advantage of its great specific gravity, the earthy matter
being washed away by water. At first this was accom-
plished by simple pan or cradle washing, but soon in Cali-
fornia it developed into hydraulic mining upon a stupendous
scale ; water for this purpose being often brought from long
distances by artificial channels and turned, under great
pressure, on the gravel-beds. Large bodies of sand could
by this means be washed over; only by such means
would it have been possible profitably to work immense
beds of comparatively ppor material. The most imposing
beds of sand and gravel disintegrate and melt away under
the enormous force, aided by the softening power of the
water.

The cost of handling a cubic yard of auriferous gravel
by the best method of washing employed in 1852 was re-
duced more than fifty times by the introduction of the
California hydraulic process, and as compared with the
simple pan-process the cost was reduced a thousand times.

38 DESCRIPTIVE MINERALOGY.

The auriferous beds thus washed over were often from
one to two hundred feet thick. Up to the present time
the greater portion of the world's supply of gold has come
from the alluvial washing and not from the quartz minings.

Gold is very widely distributed over the globe, being
found to some extent in nearly all countries. It occurs in
crystalline or semi-crystalline rocks of various ages from
the tertiary downward.

Up to the year 1890 the United States, Australia, and
Russia produced by far the greater proportion of the
world's supply of gold ; since that year the gold-fields of
Africa have added largely to the production. In 1897 rich
discoveries were reported on the uper waters of the Yukon,
but the importance of the Klondike deposit is not yet fully
determined.

Gold is mined in many of the States of the United States
and also in Alaska. Since 1849, the nrs^ year after the dis-
covery of gold in California, that State has almost contin-
ually led in the production of gold. The California pro-
duction rose from five millions in 1849 to sixty millions in
1853. In that year the maximum was reached. Between
1872 and 1878 Nevada produced more gold than California,
as did Colorado in 1897 and 1898. At the present time
California, Colorada, South Dakota, Montana, Nevada,
Arizona, Alaska, Idaho, Oregon, and Utah are our principal
producing regions, though many other States are small pro-
ducers.

The localities of gold-mines in the United States are too
numerous to mention in full, but they are spotted from Ala-
bama to Labrador along the Appalachians and are numerous
in the Rocky Mountains and along the western slope of the
Sierras ; the eastern slopes of the Sierras generally produce
silver.

Native Platinum.

Isometric. — Native crystals rare, cubes most common ;
usually in grains, scales, and small masses.

NATIVE ELEMENTS. 39

Pure platinum is nearly silver-white, but the native metal
nearly steel-gray ; streak same ; metallic, shining luster ; duc-
tile and malleable. H. =4 to 4.5. G. = i6to 19; when pure,
about 21. It is the most difficult metal to fuse, and is not
acted upon by the common mineral acids. Native platinum
is usually alloyed with one or more of the metals osmium,
rhodium, iridium, palladium, copper, and iron.

Russia supplies much the larger portion of the platinum
of commerce. It is found mainly in alluvial material in the
Ural Mountains, near Goroblagodat. Brazil, Borneo, Co-
lumbia, and St. Domingo supply a small amount. It has also
been found in the United States at several places, in Canada,
and in Australia. Its great use is for the construction of
chemical and philosophical apparatus.

Native Silver.

Isometric. — In octahedrons without apparent cleavage,
often aggregated into mossy, arborescent, or filiform shapes ;
occasionally into solid masses.

Silver is white, often tarnished black by sulphur.
Malleable and ductile ; streak white and shining. H. = 2.5.
G. = 10.1 to H. Fuses at about 1900° F. It is dissolved by
nitric acid, and the solution gives a white precipitate by the
addition of any soluble chloride. The precipitate blackens
in the light and dissolves in solution of ammonia.

Native silver is frequently alloyed with copper, and
sometimes with bismuth. It is readily distinguished from
tin, bismuth, and other white metals by its high fusing and
volatilizing points, its great malleability, and by the wet test
above given.

Native silver occurs in veins traversing metamorphic
rocks. It is usually accompanied by the ores of silver, and
frequently of other metals. Four-fifths of the product from
the celebrated mine of Kongsberg, Norway, was native
silver. This mine was discovered in 1623, and several
masses of silver weighing from 100 to 500 pounds have been
taken from it.

40 DESCRIPTIVE MINERALOGY.

Silver is found in the Lake Superior region penetrating
the native copper. It there exists in strings and masses,
and is nearly pure silver. It has also been found in similar
forms in the silver-mines of Idaho, Colorado, California, and
Nevada. Peru has furnished much native silver, and much
has come from Northern Mexico. Both gold and silver are
present in sea-water, though to a very small extent.

ORES OF SILVER.

Argentite, Silver Glance, Ag3S.

Isometric. — This important ore of silver generally occurs,
when crystalline, in some modification of the dodecahedron,
also in dendritic, capillary, and reticulated forms, massive.

Argentite has a dull metallic luster ; its color on fresh sur-
face is a blackish lead-gray, streak similar to color, and
glistening. It is malleable and sectile. H. = 2 to 2.5.
G. = 7.2 to 7.4. Fuses before the blowpipe and gives off
fumes of burning sulphur, yielding a bead of silver. Acted
upon by nitric acid with a separation of sulphur ; hydro-
chloric acid added to nitric acid solution gives precipitate
of silver chloride. Solution in NO3H deposits silver on
copper plate. Silver sulphide is distinguished from the re-
sembling ores of lead and copper by its malleability, by
yielding silver on charcoal ; it is also heavier, than resembling
copper ores.

Pyrargyrite, Ruby Silver, Dark Red Silver Ore, Ag3SbS3.

Rhombohedral. — Occurs in columnar crystals, faces often
rounded, also massive.

This ore in thin fragments has a dark cochineal color, in
larger masses nearly black, streak cochineal or brownish
red ; fuses easily before the blowpipe with spirting, giving
white coating of antimony oxide, ultimately a bead of sil-
ver. In open tube gives sulphurous fumes and white

ORES OF SILVER. 4*

sublimate, in closed tube red sublimate. Decomposed by
NO3H, depositing sulphur and the sesquioxide of antimony.

Proustite, or Light Red Silver Ore.

This ore is closely related to pyrargyrite, but contains
arsenic, replacing the antimony in part or whole. The streak
and color are brighter red than in pyrargyrite. Heated in
air gives sulphurous and arsenical fumes, in open tube white
sublimate, in closed tube yellow orpiment.

Stephanite, Black Silver, Brittle Silver Ore.

This ore is also a sulphide of silver and antimony, whose
composition is represented by the formula AgBSbS4 =
5Ag.2S,Sb3S3. It has metallic luster.

Black color and streak; is brittle and usually massive. In
the open tube fuses, giving off sulphurous and antimonial
fumes ; before the blowpipe on charcoal fuses easily, giving
a coating of antimony oxide, with soda a globule of silver.

Cerargyrite, Horn Silver, AgCl.

Isometric. — Usually occurs massive or as incrustations,
also in cubes without cleavage, rarely columnar ; color pearl-
gray to greenish gray and occasionally violet-blue ; by ex-
posure to light color changes to purplish brown, nearly
black. When pure sometimes colorless. Luster waxy, res-
inous to adamantine; in many cases cuts and looks like horn.
H. = i to 1.5. G. = 5.5. Fuses in closed tube without de-
composition, on charcoal reduced to metallic silver. Soluble
in ammonia.

This is a common ore and has been extensively worked
in our Western mines and in Mexico.

The native metal furnishes only a small part of the
world's supply of silver, the larger portion coming from the
other ores of silver, the principal of which are the silver

42 DESCRIPTIVE MINERALOGY.

sulphide, the sulpharsenides, sulph-antimonides, the chlo-
rides and bromides and the mixtures of these with the oxides,
sulphides, arseniates, and carbonates of other metals. The
principal ores of the Comstock Lode were native silver and
gold, argentite (silver sulphide), and stephanite (sulphide of
silver and antimony). Two hundred and eighty millions in
silver and gold were taken from this lode between 1860 and
1880. In the celebrated Ruby Hill mine at Eureka, Nev.,
the silver occurred mainly as argentite and chloride mixed
with limonite, lead sulphite and sulphate and carbonate, and
several other minerals. The most important ore of the
Leadville region is auriferous galena with lead carbonate
and silver chloride. Native gold and silver occur in the
ores at both the places last named.

The United States, Mexico, and South America have, up
to the present time, furnished the greater portion of the
world's silver. For the past dozen years the United States
has furnished considerably over one-third of the world's
product of silver. During this time the silver yield of this
country has varied in value from about 40 to 76 millions of
dollars. Nevada, Colorado, Montana, Utah, the Dakotas,
and Idaho have been the principal contributors.

Cinnabar, HgS.

Cinnabar generally occurs massive with slightly granular
texture ; when pure, it has a bright red to brownish-red color;
streak scarlet; luster adamantine. H. = 2 to 2.5. G. = 9 ;
less when impure. Impure varieties often have slaty struc-
ture with darker color; streak tending to brown. Other
impure varieties are of a yellowish-red color, little luster, and
yellow streak. The hepatic cinnabar or liver ore contains
carbonaceous matter and clay. Almost every variety shows
glistening specks in the mass. Pure cinnabar is completely
volatile. Roasted in air gives sulphurous fumes. Mixed
with soda and heated in closed tube is decomposed and de-
posits globules of mercury on cool sides of tube. These

COPPER. 43

tests readily distinguish it from cuprite and other red
minerals.

Cinnabar is the principal ore from which mercury is ob-
tained. It usually occurs in veins associated with slates and
shales. At Bahknut, in Southern Russia, it occurs impreg-
nating a bed of sandstone, from which considerable mercury
is obtained. The principal other mines are at Idria in Aus-
tria, Almaden in Spain, and New Almaden in California.
Some mercury is also obtained from Borneo, Mexico, and
Servia. Mines, not now worked, exist in Chili, Peru, China
and Japan, and several other countries. The Greeks are^
stated by Pliny to have obtained vermilion from Spain in
700 B.C. Besides being the chief ore of mercury, pure
cinnabar, under the name of vermilion, is used as a
paint; for this purpose it is almost wholly an artificial
preparation.

Metallic mercury in this country is put up at the mines
and transported in iron flasks weighing 76.5 pounds.
Thus expressed, the world's product, for the past ten
years, has been between 100,000 and 110,000 flasks, of
which the United States produced about one-fourth. In
1887 the product of the United States amounted to 80,000
flasks.

Native Copper.

Isometric. — In octahedrons and dodecahedrons, and modi-
fied forms. The dendritic forms are frequently composed
of aggregations of octahedrons.

Copper has a red color and is very ductile and tenacious;
when rubbed, emits a rather disagreeable odor; luster
metallic ; streak red. H. = 2.5 to 3. G. = 8.8 to 8.95. Fuses
before the blowpipe and oxidizes on surface in cooling; is
acted upon by nitric acid, and the solution gives a blue
color on addition of solution of ammonia.

Native copper is widely distributed, and often contains a
little silver. It generally occurs to a greater or less extent

44 DESCRIPTIVE MINERALOGY.

in connection with its ores, especially the carbonates and
sulphides. Siberia and Cornwall have furnished very
beautiful cabinet specimens ; Australia and the South Ameri-
can countries afford it in greater quantity, Brazil especially
having furnished some very large masses. The Lake
Superior region of Michigan, however, is the most impor-
tant locality in the world for native copper. The metal
there occurs in layers, often called veins, distributed through
amygdaloid and conglomerate and also in sandstone. Much
of the copper contains a fraction of a per cent of silver in-
timately alloyed. It also very frequently contains scattered
grains and penetrating threads of silver. This mixture of
copper and silver is found in other countries, and it has not
been artificially imitated. The copper in the Lake Superior
region is nearly all in the native state, and very large masses
have been taken from the mines ; one weighing 420 tons
and containing copper of 90 per cent purity was taken from
the Minnesota mine in 1857.

The gangue-stone contains generally from one to five per
cent of copper. The mining operations of the largest com-
pany (Hecla and Calumet) are simple, consisting of crushing
and stamping the gangue and separating the metal by
difference of specific gravity, the sands being washed away
by running water. The machinery for this purpose is very
extensive and perfectly adapted. The formations in which
the copper occurs are not veins in any proper sense. They
are most probably sedimentary formations whose original,
position has been changed. The most important ores of
copper are given below.

ORES OF COPPER.

The ores of copper are numerous and many of them not
distinctly defined in composition. Only the more important
will be described.

The common wet test for a copper ore is to act upon the
suspected mineral with nitric acid, dilute, and add ammonia;
if copper is present, a blue solution is obtained.

ORES OF COPPER. 45

Chalcopyrite, Copper Pyrites, Copper and Iron Pyrites, CuFeS.y

Is most commonly massive. Has a slighly greenish,
bronze-yellow color, often iridescent by tarnish. Streak
and powder greenish black. H. = 3.5 to 4. G. — 4 to 4.3.
Heated in the air before the blowpipe gives off sulphurous
fumes and fuses to a magnetic globule ; this globule powdered
and further heated on charcoal will reduce to a bead of
iron and copper. Chalcopyrite must be well roasted before
it will give the copper test with nitric acid and ammonia.

It sometimes resembles native gold in color, or again
iron pyrite. It is distinguished from the first by lack of
malleability, and from the second by its softness, richer
yellow color, and its greenish-black streak.

Chalcopyrite is the ore from which the bulk of the
copper of commerce is obtained.

It occurs in veins intersecting metamorphic rocks and
occasionally in cavities or veins in unchanged sedimentary
rocks. Its most common associates are the copper carbon-
ates and the sulphides of iron, lead, or zinc.

Chalcocite, Copper Glance, Vitreous Copper, Cu2S.

Occurs in crystals, but usually massive ; metallic luster ;
color blackish lead-gray, often tarnished blue or green ;
streak same as color, often glistening; slightly brittle.
H. = 2.5 to 3. G. — 3.5 to 5.8. Easily fusible by blowpipe
on charcoal, giving sulphurous fumes and leaving a globule
of copper. Acted upon by hot nitric acid with separation
of sulphur ; nitric acid solution deposits copper on iron sur-
face ; gives the usual copper test.

The ore is not generally found pure, a portion of the
copper being often replaced by iron. It occurs in great
abundance and in nearly a pure form in several of the
Montana mines. It is also an important ore in Arizona,
Colorado, and New Mexico.

46 DESCRIPTIVE MINERALOGY.

Bornite, Erubescite, Variegated Copper 3(Cu,S,Fe2S3).

This in appearance is one of the most striking of the
copper ores when in fresh condition. It then has a brilliant
purplish-brown color, but changes on exposure to the air
to many hues with varied iridescence. When pure it is
represented by the formula 3(Cu2S,Fe,S9), which may be
written Cu,FeS,. The proportions of the constituent
elements vary widely without materially affecting the
general appearance of the ore. Has metallic luster; the
streak is a dark grayish black. H. = 3. G. = 4.5 to 5.5. It
is an important ore of the Butte mines.

Before the blowpipe fuses easily to a black magnetic
globule; this taken with its peculiar color and brilliant
iridescence distinguishes it from chalcocite.

Tetrahedrite, Gray Copper Ore.

This mineral when pure is a double sulphide of copper
and antimony. The antimony is frequently in part replaced
by arsenic, and the copper by iron, zinc, silver, or lead. It
is an unimportant ore in this country except when it
becomes rich in silver, and is then valuable for the silver.
This argentiferous form of the ore is found both in Mon-
tana and Colorado. The pure tetrahedrite is represented
by the formula 4Cu,S,SbaS8.

Tennantite.

This mineral is essentially a sulphide of arsensic and
copper ; it often contains antimony and graduates into the
tetrahedrite. It is of no importance in this country as a
copper ore.

Cuprite, Red Copper Ore, CuaO.

Isometric. — Prevailing form the octahedron, also in the
derived forms.

ORES OF COPPER. 47

It occurs often massive and also earthy. Has different
tints of deep red, often reddish gray ; luster adamantine or
semi-metallic, dull in impure varieties; streak brownish red.
H. = 3.5 to 4. G. — 5.8 to 6.1. Heated on charcoal, reduces
to metallic copper. Frequently occurs with the other
copper ores ; outer surface often converted into carbonate.
Gives copper test with nitric acid and ammonia.

Melaconite, Black Copper Ore, CuO.

Found as cubes in Lake Superior copper region, but
generally in black masses and botryoidal concretions along
with other copper ores. Important ore in some of the
mines of this country, as in Tennessee.

Tenorite is another variety of the same ore, found in the
Vesuvian lavas and in earthy forms about copper lodes.

Malachite, Green Hydrous Copper Carbonate, CuC03,CuO,HaO.

Monoclinic. — Crystals (rare in nature) generally tabular
prisms.

Usually occurs in incrusted masses with reniform,
botryoidal, or mammillary surfaces with fibrous texture,
often showing concretionary structure. Also compact or
earthy. Color varies from emerald to nearly grass-green.
Streak green, but generally lighter than mineral. Luster
vitreous, pearly, or silky ; earthy varieties have little luster.
H. = 3.5 to 4. G. = 3.7 to 4. Acted upon by the common
mineral acids and gives the copper test with nitric acid and
ammonia.

Malachite is generally associated with other ores of
copper; and when in sufficient quantity is a very valuable
mineral. The incrustations made by it often have banded
shades of green which give a very pleasing effect. It is
susceptible of a high polish and is much used in indoor
decorations, making beautiful mantels, table-tops, vases,
etc. It is too soft for jewelry, though it is sometimes

4 DESCRIPTIVE MINERALOGY.

passed off as turquois, The mines of Siberia have given
the largest quantity, though it occurs in a good many
countries to a smaller extent.

Azurite, Blue Hydrous Copper Carbonate.

This mineral is very similar to malachite, but the
color varies from azure-blue (the color of the powder)
to indigo-blue ; its streak is also blue. These charac-
teristics distinguish it from malachite ; it fulfills the tests
given for that mineral. It is valuable when abundant,
but occurs much less abundantly than malachite. Some-
times used as a pigment, but is not very permanent.
Contains a smaller per cent of copper than malachite.

Chrysocolla, Hydrous Copper Silicate, CuOSi03,2H20.

This is an amorphous, compact mineral of bluish-green
color ; sometimes occurs in thin layers, as incrustations ;
and as botryoidal masses. H. = 2 to 4. G. = 2 to 2.4.
Distinguished from the carbonates by its bluish-green
color and no visible action with acids; very frequently
contains the carbonate. Valuable as an ore when abun-
dant.

The world's product of copper in 1897 was about
412,000 tons, of which the United States furnished more
than one-half. Michigan, Montana, and Arizona in that
year gave over eleven-twelfths of the yield of the United
States. Only in the first-named State is the metal ob-
tained in large quantity from the native form, elsewhere
it is from the ores. The principal Montana ores are the
different forms of copper sulphide in a siliceous gangue.
Much silver is associated with the ores. The Arizona
ores are largely the oxidized forms, though they frequently
change to the sulphides in the lower reaches of the
veins.

OKES OF LEAD. 49

ORES OF LEAD.

Lead rarely occurs native, but exists in many compounds.
It occurs combined with oxygen, sulphur, arsenic, tellurium,
selenium, and as carbonates, sulphates, chromates, molyb-
dates, and phosphates. Its principal ore is the sulphide.

Galenite, Galena, Lead Sulphide, PbS.

Isometric, — Usually in cubes or some of the simpler de-
rived forms ; also granular. It has metallic luster, bluish-
gray color, streak slightly darker. H. — 2.5. G. = 7 2 to 7.6.
Before the blowpipe on charcoal it fuses readily and emits
sulphurous fumes, coats the charcoal with lead oxide, and
leaves a globule of lead. It is acted upon by strong nitric
acid with separation of some sulphur ; this solution gives
black precipitate with ammonium sulphide.

Galena is a very widely distributed ore. It occurs both
in veins and in beds or pockets, and both in metamorphic and
unchanged rocks. Galena is very frequently associated with
the sulphides of iron, copper, zinc, and silver. Some silver
sulphide is nearly always present in galena ; when the silver
becomes worth extracting the ore is called argentiferous
galena. The argentiferous galena generally has a more
micaceous appearance than the common ore. The gangue
in lead-mines is generally calcite, quartz, or baryta, and
sometimes fluor-spar.

Abundant lead-ore deposits occur in the States of Iowa,
Wisconsin, Missouri, and Illinois. None of these deposits
come under the head of true veins, but are in sheets or beds
between the strata. The sheets are usually only a few inches
thick and are rarely accompanied by gangue or true vein-
walls. The bed-deposits in this region are large, thick
masses, as though underground caves or chambers had been
filled by the ore. It is probable that the solvent waters that
produced the caves also deposited the mineral from solution.
Casts of fossils in galena are often found in the region,

$0 DESCRIPTIVE MINERALOGY.

showing the aqueous origin of the ore. Galena occurs in
true veins in several of the Eastern States and in many of the
Western. Of late years the greater portion of the lead pro-
duced in the United States has been in connection with the
gold and silver mining of the West, the lead being a by-
product. In 1897 from this source there were obtained
145,000 tons of lead, while only about 50,000 were obtained
from other domestic sources.

The greatest consumption of lead is in the manufacture
of white lead, though large quantities are used in making
pipes, shot, and sheeting. Galena is sometimes used for
glazing coarse stoneware, being finely ground, mixed with
other glaze material and applied to the vessels.

Cerussite, White Lead Ore, Lead Carbonate, PbCO,.

Orthorhombic. — Cerussite occurs in orthorhombic crystals,
often compound, but more generally the ore is found gran-
ular compact, or in earthy masses. The crystalline forms,
when pure, vary in color from white to dark gray, almost
black ; the presence of copper gives blue or green tinge ;
streak uncolored ; luster adamantine, vitreous to resinous,
and pearly. H. — 3 to 3.5. G. = 6.4 to 6.6. Brittle. Fuses
readily before blowpipe and yields lead in reducing-flame ;
acted upon with effervescence by nitric acid ; in closed tube
it decrepitates, loses CO2, and turns brown or yellow.

The lead carbonate is a very important ore at many
mines in the Western States, especially in Colorado, Utah,
and Nevada. The carbonate is formed from galena by
meteoric agencies, and in these mines is generally found as
loose sand or in compact lumps of a yellowish or brown
color, due to the iron present ; clusters of crystals are also
frequently present in the compact masses.

Anglesite, Lead Sulphate.

This ore of lead resembles cerussite and often occurs
with it, both being formed from the sulphide. Its crystal-

ORES OF ZINC. 51

line system is the same as that of cerussite. It fuses readily,
and in reducing-flame or with soda yields metallic lead.
It is slightly soluble in nitric acid, but no effervescence
which distinguishes it from the carbonate. This ore gener-
ally accompanies cerussite in the mines of the Rocky Moun-
tain region.

ORES OF ZINC.

If zinc occurs native, it has not been found in any con-
siderable quantity. It has been reported from Australia,
South Africa, Colorado, and Alabama, but satisfactory infor-
mation has not yet been given in regard to these finds. Its
compounds are pretty widely distributed ; they are the
oxides, sulphides, carbonates, and silicates, all of which are
used for obtaining the metal.

Sphalerite, Blende, ZnS.

Isometric. — Prevailing forms, the octahedron and dodeca-
hedron and modifications. Often massive and sometimes
fibrous.

The color of blende presents various shades of yellow,
red, brown, and black; also gray to white and sometimes
greenish. Luster resinous to waxy and sometimes semi-
metallic. Streak is white to yellowish brown. H. — 3.5 to 4.
G. — 3.9 to 4.2. The purer specimens will often become
phosphorescent by friction in the dark. The sulphides of
iron, cadmium, and lead are often present in it. It is fusible
with difficulty by the blowpipe; heated in open tube gives
sulphurous odor ; on charcoal gives yellow coating which
turns white on cooling. It is acted upon by hydrochloric
acid and emits hydrogen sulphide ; often shows efferves-
cence.

This ore occurs in many localities and in rocks of all
ages. The lead-mines of the Mississippi valley afford it
abundantly, as do the zinc-mines of Missouri arid Kansas.
By oxidation the ore is converted into white vitriol.

52 DESCRIPTIVE MINERALOGY.

Zincite, ZnO.

This ore generally occurs in tabular masses or dissemi-
nated grains. Luster adamantine or semi-metallic ; its color
varies from bright red to dark or brown ; streak is orange-
yellow. H. =4.0 to 4.5. G. = 5.6 to 5.8. Acted upon by
nitric acid. Yields yellow coating on charcoal, which turns
white on cooling. It is a good ore of zinc, and is the ore of
Sussex County, N. J.

Smithsonite, Zinc Carbonate, ZnC03.

Rhombohedral. — Smithsonite seldom occurs distinctly crys-
tallized ; generally botryoidal, reniform, or stalactitic ; some-
times granular or loosely compacted. This ore is of light
color, but seldom white ; generally light gray or brownish
white, sometimes shaded green, blue, or buff ; streak uncol-
ored ; luster vitreous to pearly. Brittle. H. = 2 to 4. G. ='
4.2 to 4.5. It is infusible before blowpipe alone ; with soda
on charcoal gives a coating of zinc oxide ; effervesces in
acid.

This is a valuable ore of zinc, and is found abundantly in
the mines of the Mississippi valley, also in Pennsylvania.
It very generally accompanies galena and sphalerite. Cer-
tain forms of it are termed dry-bone by miners. The carbon-
ate in England is often called Calamine.

Calamine, Hydrous Zinc Silicate.

Orthorhombic. — Crystalline forms seldom distinct. Cala-
mine is a hydrous zinc silicate and closely resembles the
carbonate in appearance and physical properties. It usu-
ally occurs associated with the carbonate, and is found in
the localities named above for that mineral. It gelatinizes,
but does not effervesce with acids. It yields water in
closed tube.

Willemite, Zinc Silicate.

Hexagonal, Rhombohedral. — Occurs in long or short hexag-
onal prisms ; also in massive, granular, and rounded forms.

IRON. 53

This mineral differs from calamine in composition in being
anhydrous.

Willemite varies in color from white and greenish yellow
through light to dark brown. Its streak is uncolored ;
luster vitreous or resinous. H. = 5.5. G. = 3.9 to 4.2. It
fuses with difficulty, and gelatinizes with acids. Its com-
position is ZnaSiO4 ; a part of the zinc is sometimes replaced
by manganese. It is frequently present with zincite and
franklinite being thus found in New Jersey.

Native Iron.

Isometric. — Generally massive. Native iron has gray
color and streak; it is malleable and ductile. H. = 4.5.
G. = 7.3 to 7.8. Acts on magnet.

Native iron is of very limited occurrence ; there are
two varieties, meteoric and telluric. Meteorites contain
native iron usually alloyed with nickel in considerable
quantity, and small quantities of cobalt and copper are often
present. A polished surface of meteoric iron, when acted
upon by nitric acid, will frequently show triangular figures
indicating a coarse octahedral structure in crystallization.
These figures are called Wiedmannstadt's figures, and
when uniform in different specimens indicate an identical
origin. Meteoric iron often contains nodules of iron
monosulphide and the phosphide of iron and nickel
(Schreibersite). Meteorites have been found in many
places varying in size from an ounce in weight up to
twenty tons. They are believed to have a non-terrestrial
origin.

Telluric iron is native iron of terrestrial origin. It is
found as imbedded particles or grains in some basaltic rocks.
Masses have also been found ; one weighing twenty tons
was found on Disco Island, Greenland, in 1870. It is
thought probable that this telluric iron has been pro-
duced by the reduction of the iron-bearing minerals in
the passage of the containing rock through carbonaceous,
strata.

54 DESCRIPTIVE MINERALOGY.

ORES OF IRON.

The ores of iron are the oxides, carbonates, and sul-
phides. The oxidized forms and the silicates are very
widely distributed as the common coloring matter of soils.
The ores, when heated in the reducing flame of a blow-
pipe, become magnetic, and when treated with hydrochloric
acid give a blue precipitate on the addition of potassium
lerrocyanide.

Pyrite, Iron Pyrites, FeS2.

Isometric. — Usually in cubes, faces frequently striated ;
striae of adjoining faces are always perpendicular to each
other. Occurs in forms derived from cube, also in globular
nodules with radiated structure.

Pyrite has generally a brass-yellow color, sometimes
brownish by surface alteration ; is brittle, and has metallic
luster. H. = 6 to 6.5 ; will strike fire with steel. G. — 4 to 5.
Streak is brownish black. Roasted before the blowpipe
gives sulphurous fumes and leaves a globule fusible with dif-
ficulty and attracted by the magnet. It resembles copper
pyrites, but is of a lighter color, harder, and has different
streak. It is readily distinguished from gold by its hardness
and brittleness.

Pyrite is one of the most widely distributed of ores, but
is more generally employed to obtain sulphur than iron. It
occurs in rocks of all ages. In auriferous regions it often
contains gold, and is sometimes worked to obtain that metal.
Owing to its common occurrence in rocks and its change-
able nature it is one of the chief natural causes of rock dis-
integration. No stone containing it should be used for
building purposes. The disintegration of the rock contain-
ing it is brought about by the oxidation of the pyrite and
the solution of the resulting compound. Other sulphides
of iron have the same effect on the containing rock. Pyrite
is used in the manufacture of sulphuric acid, alum, green

ORES OF IRON. 55

vitriol, and sulphur ; occasionally the iron is extracted.
Pyrite is sometimes called mundic and fool's gold by miners.

Pyrrhotite, Magnetic Pyrites, Fe7S8.

Hexagonal. — The crystals of this mineral belong to the
hexagonal system, but well-defined crystals are rare. It
usually occurs massive or disseminated in granular or scaly
aggregates.

Pyrrhotite is a sulphide of iron whose general formula
is FeMSM + I, in which n may vary from 5 to 16; the average
composition is accepted to be indicated by Fe7S8, which
gives the percentage composition S = 39.6, Fe = 60.4. Its
color is generally between bronze-yellow and copper-red ; it
readily tarnishes to a dull bronze ; streak grayish black.
H. = 3. 5 to 4.5. G. =4.5 to 4.7. Brittle and slightly mag-
netic ; powder attracted by magnet. Its color and magnetic
properties distinguish it from chalcopyrite ; these charac-
ters and its inferior hardness from pyrite. It is acted upon
by HC1, yielding H3S ; before the blowpipe on charcoal
gives magnetic globule.

Pyrrhotite is found in small quantities at many places,
and is sometimes used as an ore of sulphur in the manufacture
of sulphuric acid. It is often present in meteoric iron,
though the monosulphide FeS, troilite, is the principal sul-
phide of meteorites.

Mispickel, Arsenopyrite, Sulpharsenide of Iron, FeAsS.

Its color is steel-gray or tin-white. Metallic luster;
streak grayish black. H. = 5.5 to 6. G. = 6 to 6.4. It is
brittle, and the texture often granular, giving slightly hackly
fracture. Heated in closed tube gives red and yellow sub-
limates of arsenic sulphide and also a metallic-like deposit
of arsenic; roasted before the blowpipe gives strong garlic
odor of arsenious oxide and leaves a globule attracted by
the magnet ; when struck sharply with a steel it gives the
same odor. It is very frequently associated with the ores of

56 DESCRIPTIVE MINERALOGY.

silver and lead and the sulphides of iron, copper, and zinc.
Cobalt sometimes replaces some of the iron in mispickel,
such compound being one of the ores of cobalt. Mispickel
is one of the chief ores of arsenic.

Hematite, Specular Iron Ore, Fe203.

Rhombohedral. — Often in granular masses, compact or
friable; also lamellar, micaceous, and earthy; also in botry-
oidal and stalactitic forms.

The color of the metallic varieties varies from iron-black
to steel-gray, the crystals often iridescent. Luster metallic,
of crystals brilliant ; streak cherry-red to brownish red.
H. = 5.5 to 6.5. G. — 4.5 to5.3. Sometimes slightly mag-
netic. The compact and earthy varieties have not the luster
or color of the metallic, but give the same streak. Acted
upon by hydrochloric acid, and gives blue precipitate upon
addition of potassium ferrocyanide.

The more important varieties of the hematite are the
following :

Specular. — With distinct metallic luster.

Red Hematite. — Dark or brownish-red color, semi-metallic
luster.

Micaceous. — In thin scales, schistose structure.

Ocherous. — The red earthy varieties often containing
clay ; when soft and pulverulent, red ocher ; when harder,
compact, and of fine texture, it is red chalk.

Argillaceous. — Includes compact red and brownish-red
varieties, often of semi-metallic luster. Composed of the
oxide, with sand, clay, and often other impurities. The
most compact of these varieties, with a jasper-like texture
and appearance, is the jasper clay ore. The less hard and
jaspery gives the clay iron-stone variety. This last name is
also applied to the clayey siderite and limonite.

When made of flattened concretions or grains it is the
lenticular ore. The argillaceous varieties give the red or
brownish-red streak. When heated in the reducing-flame
hematite easily becomes magnetic. Acted upon by hydro-

O&ES OF IRON. 57

ch/oric acid, and gives blue precipitate with potassium
ferrocyanide. These tests, with its red streak, serve to
distinguish the mineral.

Martite has the same composition as hematite, but crys-
tallizes in isometric forms, octahedrons, dodecahedrons,
which are thought to be pseudomorphous of magnetite ;
the color is iron-black, luster sub-metallic; the streak is
purplish-brown, and the mineral but slightly, if at all, mag-
netic. These characters distinguish it from magnetite. It
is of frequent occurrence in magnetic regions.

Hematite is one of the most common and widely dis-
tributed of ores, and occurs in rocks of all ages. It is found
in so many localities that only a few can be named. The
island of Elba has been celebrated for this ore since before
the Christian era, and it still produces it. The ore of the
two so-called iron mountains of Missouri was mainly hema-
tite ; it is an abundant ore of the Marquette region, Michi-
gan, and is found at many other places in the United
States ; when pure, it is less easy to work than the other
oxidized ores.

The pulverized ore is used for metal polishing. The
artificially prepared oxide furnishes the Venetian-red paint,
and the red chalk is used for crayons and coarse pencils.

Magnetite, Magnetic Iron Ore, Fe304.

Isometric. — Prevailing crystalline forms the octahedron
and dodecahedron ; very commonly massive and granular.

The color of the ore is distinct iron-black, luster semi-
metallic, streak black. H. = 5.5 to 6.5. G. = 4 to 5. It is
magnetic and sometimes endowed with polarity. Acted
upon by hydrochloric acid, and gives blue precipitate upon
addition of potassium ferrocyanide. The weight, streak,
and magnetic properties distinguish this ore from alj other
minerals.

Magnetite occurs in beds, principally in metamorphic
rocks, and is most abundant in the Archean. It is found in
many places throughout the world. It is the principal ore

58 DESCRIPTIVE MINERALOGY.

-of Sweden and Norway, and exists in extensive beds in
New York and to a less extent in several of the New Eng-
land States.

Franklinite.

This ore is similar to magnetite, but some of the iron has
been replaced by zinc and manganese. Its physical proper-
ties are about the same as magnetite, but the streak is
generally not so black, often a reddish brown. This ore
occurs abundantly in New Jersey and often contains zincite.
The franklinite is a valuable ore for the manufacture of zinc-
white and Spiegeleisen.

Limonite, Brown Hematite, 2Fe203,30H2.

This ore occurs in botryoidal, mammillary, and stalac-
titic forms with fibrous texture ; also massive, and as con-
cretions and earthy.

The color is brown to black, and in the earthy varieties
yellowish brown. Streak yellowish brown. Luster, when
present, semi-metallic, sometimes silky ; it is frequently
without luster, especially in the earthy forms. H. = 5 to 5.5.
G. greater than 4 ; pulverulent varieties less hard and less
heavy.

The principal forms of the ore are the following :

Brown Hematite, which includes the more compact forms,
usually with semi-metallic luster, the botryoidal, stalac-
titic, etc.

Ocherous Ore. — All soft, earthy varieties of brown or
yellowish color, giving the brown and yellow ochers.

Impure compact, clayey ores constitute the brown and
yellow clay iron-stone.

Bog Ore is a soft brownish-black ore when pure. It
sometimes takes imitative forms, and when mixed with silica,
which is very frequently the case, is quite hard.

These ores give off water in a closed tube readily, be-
come magnetic before the blowpipe, and give the iron test

OKES OF IRON. 59

with hydrochloric acid and potassium ferrocyanide. These
characters with the streak distinguish the ore.

Limonite is a common and valuable ore and is abundantly
and widely distributed in the United States. The localities
of its occurrence are too numerous to mention. The ore is
the result of the alteration of iron-bearing minerals, brought
about by atmospheric agencies. The yellow ocher is used
for a common paint. The name limonite is from the Greek
word for meadow.

Siderite, Spathic Iron Ore, Chalybite, Iron Carbonate, FeC03.

Rhombohedral. — Occurs also in botryoidal and nodular
forms, in compact masses and earthy. Crystalline form
shows sparry faces which are often curved.

Color of mineral is ash-gray to yellowish gray, yellow
to reddish brown, often brown to brownish black from
exposure. Luster pearly to vitreous, also dull. Streak
light yellow to yellowish brown. H. — 4. G.=4. Before the
blowpipe it blackens and becomes magnetic. When pow-
dered acted upon with effervescence by hydrochloric acid,
and gives a blue precipitate upon addition of potassium
ferrocyanide.

Spathic Ore is the crystallized form with sparry faces.
When the ore is largely mixed with clay it gives the clay
iron-stone, and when bituminous matter is present it is the
black band.

It is a valuable ore, occurring as the gangue in certain
veins, and in beds, and is abundant as clay iron-stone in
the coal formations. It takes the limonite color when
exposed to atmospheric agencies due to conversion into
that form. Chalybeate waters hold it in solution and
deposit it upon coming to the surface, the color around
such springs being due to its conversion into hydrated
sesquioxide.

The clay iron-stone constitutes the great ore of England.
It occurs also in the coal-beds of Pennsylvania, West Vir-
ginia, and Ohio. The United States now produces more

6O DESCRIPTIVE MINERALOGY.

iron than any other country in the world, England coming
next in production with nearly as much.

Chromite, Chromic Iron Ore, FeCr204 or FeOCr203.

Isometric. — Chromite usually occurs in granular or com-
pact masses or in disseminated grains. Color is brownish
black to iron-black ; streak brown. H. = 5.5. G. — 4.3 to 4.6.
Sometimes slightly magnetic. It is distinguished from
magnetite by its streak and by giving a green bead indic-
ative of chromium when fused with borax.

Chromite is the source of nearly all the compounds of
chromium which are so extensively used as pigments, its
principal use being in the production of potassium bi-
chromate.

Stibnite, Gray Antimony, Antimony Glance.

Orthorhombic. — Crystals prismatic, long columnar or acicu-
lar, faces vertically striated ; pyramidal faces curved or
distorted ; common in radiating or divergent groups of
acicular crystals, also massive with columnar fibrous
texture.

Stibnite is the sesquisulphide of antimony, SbaSt. Its
color is lead-gray ; luster metallic, very brilliant on fresh
cleavage surface ; tarnishes black, sometimes iridescent ;
streak lead-gray. H. = 2. G. = 4.55 to 4.65.

Heated in open tube stibnite gives off sulphurous and
antimonial fumes, the latter being partly Sb2O3 and partly
Sb2O4 ; the first oxide is fusible and volatile, the latter
neither. Stibnite is easily fusible and entirely volatile
before the blowpipe ; when pure it is acted upon by
HC1 with evolution of H3S. The above characters dis-
tinguish it from galena and graphite, which it sometimes
resembles.

Stibnite is the chief ore of antimony, besides being
directly used as a substitute for sulphur in some prepara-
tions.

OXIDES. 6 1

Pyrolusite, Black Oxide of Manganese, Mn02.

Pyrolusite occurs in orthorhombic crystals, but may be
pseudomorphous. Generally occurs in short columns, often
parallel fibrous and divergent, granular massive and reni-
form, also compact.

Pyrolusite is the dioxide of manganese, MnOa. Its color
is dark gray to iron-black, sometimes bluish ; luster almost
metallic ; streak black. Crystals have a hardness of 2 to 2.5,
other varieties softer. G = 4.7 to 4.9.

Fused with borax gives violet bead of manganese ; acted
upon by HC1 with evolution of Cl.

Pyrolusite is the most important ore of manganese, being
employed both for its manganese and oxygen, and for
making bleaching-powder.

Manganite is a hydrous manganese sesquioxide. Its
streak is generally less dark than that of pyrolusite ; it is
also harder and yields water in a closed tube.

Psilomelane and wad are minerals largely composed of
oxides of, manganese of varying degrees of purity, but whose
compositions are not definite.

Cassiterite, Tin-stone, Black Tin, Tine Ore, Tin Oxide, Sn02.

Tetragonal. — Occurs in crystals of short pyramidal type
or slender columns acutely terminated, twins common ; also
in reniform and spheroidal masses with divergent fibrous
texture ; in granular masses and in rounded pebbles.

The color is sometimes white, gray, yellow, or red, but
more generally brown or black ; streak light gray to brown.
H. — 6 to 7. G. = 6.8 to 7.1. Before blowpipe infusible
alone, gives globule of tin on charcoal with soda.

Stream-tin ore is the detritus from veins and is found in
the alluvial deposits of streams which drain tin-bearing re-
gions. The globular masses of tin ore with radiating
fibrous texture and concentric structure are sometimes called
wood-tin, from the woody appearance.

62 DESCRIPTIVE MINERALOGY.

Cassiterite is the principal ore of tin. It occurs in veins
intersecting granite and metamorphic rocks. The largest
amounts of tin are produced in the island of Banca and in
Great Britain ; considerable quantities also come from Ger-
many, Austria, Siberia, Australia, and Bolivia. Tin has as
yet been produced only in very small quantity in this
country.

Rutile.

Tetragonal. — Often in twinned crystals ; in prisms of four,
eight, or more sides, faces of prisms usually striated verti-
cally ; often in fibrous acicular aggregates penetrating
quartz ; sometimes massive.

Rutile is the dioxide of titanium, TiO2. Its color is red-
dish brown to red, passing through violet, bluish to black,
sometimes yellowish ; luster adamantine or metallic ; streak
pale brown. H. = 6 to 6.5. G. = 4.2 to 4.3.

It occurs in the more distinctly crystalline rocks, both
metamorphic and plutonic.

It is frequently found penetrating quartz in acicular
needles or hair-like fibers ; polished stones of this kind are
sometimes very beautiful and constitute what the French
have called " fleches d'amour."

Corundum, A1203.

Rhombohedral. — Generally in combinations of six-sided
prisms and acute pyramids, often with uneven and irregular
surfaces, also massive and fine or coarse granular.

Corundum is the sesquioxide of aluminum ; the uncrys-
tallized varieties usually show a small per cent of iron.

Corundum is sometimes colorless, but generally some
shade of blue, red, or yellow, massive forms often brown or
black ; streak uncolored ; luster adamantine to vitreous,
sometimes pearly on bases. H. =9. G. == 3.9 to 4.1. B.B.
infusible.

Corundum is distinguished by its great hardness, infusi-
bility, high specific gravity, and its luster.

OXIDES. 6$

Sapphire or oriental ruby are the names applied to clear
crystals of fine colors; blue is the true sapphire color;
true ruby is red, highly prized as a gem.

Corundum is the name applied to the dull irregularly
colored crystals and masses as well as to the species.

Emery includes the granular varieties, usually of dark
color from presence of magnetite.

Corundum, the species, occurs in crystalline rocks, both
plutonic and metamorphic. Burmah and Ceylon are cele-
brated for their rubies and sapphires ; many fine gems have
been secured in this country, the finds in North Carolina
and Montana being most numerous. Corundum is mined in
North Carolina, and emery in Massachusetts and New
York. Corundum and emery are crushed to powders of
different fineness and used for polishing.

Diaspore is the hydrous oxide of aluminum, A1,O8,H3O ;
it is usually found with corundum.

lswft*£

Bauxite, Beau

Bauxite is a clay-like mineral found also in grains, con-
cretions, and massive. It is a hydrated aluminum oxide,
Al2O3,2HaO; iron is frequently present, replacing some of
the aluminum.

Its color varies from white through gray to yellow and
brown ; in its purer forms it is largely used in France in the
preparation of the alums and also in the manufacture of
aluminum.

Turquois.

Turquois is a hydrous aluminum phosphate. It has a
bluish-green color, vitreous to waxy luster. H. = 6. G. =
2.6 to 2.8. When heated before the blowpipe it gives off
water and turns brown ; infusible, but dissolves quietly in
hydrochloric acid. It often contains from one to five per
cent of copper, also a little iron and manganese.

It has been found in New York, Arizona, and Nevada in

64 DESCRIPTIVE MINERALOGY.

this country, and in several places abroad. It is susceptible
of high polish and is used as a gem.

Monazite.

Monazite is a phosphate of the cerium group of metals.
It has come into considerable prominence in the past years
as the source of cerium oxide and other infusible earths. It
contains cerium, lanthanum, thorium, didymium. It is now
found in greatest quantity in rolled sands in Brazil ; under
similar conditions considerable quantity has been obtained
from North Carolina.

Spinel.

Isometric. — Occurs only in crystals, usually in octa.
hedrons.

Spinel is an aluminate of magnesium (MgO,AlaO3) ; the
magnesium is often partly replaced by iron or manganese,
and the aluminum by iron or chromium. The color is
occasionally white, but more generally some shade of red,
brown, blue, or green ; streak white ; luster vitreous. H. =
8. G. = 3. 5 to 4.1. B.B. infusible. Its most evident dis-
tinctions are its hardness, infusibility, and octahedral form.

Spinel occurs imbedded in granular limestone, serpen-
tine, and other metamorphic rocks ; also in volcanic rocks.
The spinels of fine color are prized as gems ; the red spinel
is the common ruby of jewelry ; it often resembles the true
ruby (corundum), but the latter never occurs in octahedrons.

Chrysoberyl.

Orthorhombic. — Occurs in short columnar or thick tabular
crystals. Often forms compound crystals, like irregular
six-pointed stars.

Chrysoberyl is an aluminate of beryllium. Its color
varies through several shades of green, occasionally rasp-
berry by transmitted light, pleochroic ; streak uncolored ;

COMPOUNDS OF SODIUM AND POTASSIUM. 6$

luster vitreous. H. = 8.5. G. = 3.5 to 3.8. B.B. alone in-
fusible.

Its hardness, infusibility, and tabular crystals and high
specific gravity, taken in connection with its greenish color,
are its most evident characteristics which distinguish it from
resembling minerals.

Chrysoberyl is found in this country in Connecticut,Maine,
New Hampshire, and New York. The finest crystals make
beautiful gems. Two varieties of the species are :

Alexandrite, which is an emerald-green chrysoberyl, sup-
posed to be colored by chromium.

Cat's-eye has a greenish color and exhibits chatoyant
effects.

Halite, Rock Salt, NaCl.

Isometric. — Cube the prevailing form.

Rock salt is sometimes transparent and colorless, though
often tinged some shade of yellow, red, or green. Its taste
is well known. H. = 2. G. — 2.2. Decrepitates when heated,
easily fusible, and colors flame • yellow. It is soluble in
water and gives a white precipitate with silver nitrate.

Salt exists in all geological formations from the Silurian
up. It is found in beds extending over large areas and is
usually associated with gypsum, anhydrite, clays, or sand-
stone. In some places the salt is mined, or taken in the
solid state directly from the beds; in others the waters
from brine-springs are evaporated. The salt-mines of Po-
land and Hungary are the most celebrated in the world.
The first, near Cracow, have been worked for over seven
centuries and are almost of inexhaustible extent. Salt is
mined in this country in Louisiana, and Kansas, and in
Wyoming, Genessee, and Livingston counties, New York.

Most of the salt made in the United States is by the
evaporation of brines or waters from salt-springs. Michi-
gan and New York are the chief producers by this method,
though other States furnish some. The rock salt taken
from mines is generally so impure that it is dissolved and
recrystallized by evaporation before going into the market.

66 DESCRIPTIVE MINERALOGY.

Salt is also made in some places by the evaporation of sea-
water or the water of salt lakes. The consumption of salt
in the United States is about one bushel per capita, and the
productive capacity is considerably more than this.

Cryolite, Ice-stone, Double Fluoride of Sodium and Aluminum,
Na,AlFB or 3NaF,AlF,.

Monoclinic. — Cryolite usually occurs massive, generally
white, though sometimes giving shades from red through
brown to black ; translucent ; has an irregular platy or
fibrous fracture which is very characteristic. It fuses
readily in forceps, coloring flame yellow ; on charcoal easily
yields clear bead ; acted upon by sulphuric acid with evolu-
tion of hydrofluoric acid.

This mineral is largely used in the production of alumi-
num and formerly of sodium. It is principally obtained at
the Ivigtut mines of west Greenland, from which place it is.
largely imported to the United States.

Niter, Saltpeter, KNO.

Orthorhombic. — Niter, when pure, is white and very brit-
tie. It has a saline and cooling taste. H. = 2. G. = 1.97.
Deflagrates when heated with powdered charcoal. Differs
from sodium nitrate in not deliquescing when exposed to
the air.

Niter is sometimes found mixed with the earthy flooring
of caves ; Kentucky, Tennessee, and several Western States
have furnished it in small quantity from this source. It
forms abundantly as an efflorescence on the soil in certain
countries, especially during hot weather after rains. India
and Persia are the most noted countries for this natural
production. In many countries it is artificially prepared as
described in Chemistry.

COMPOUNDS OF CALCIUM. 67

Carnallite.

Hydrous chloride of potassium and magnesium.

This mineral occurs in granular masses. It is of white
color when pure, but generally reddish ; has a bitter taste
and is deliquescent ; showing greasy luster when fresh.

Carnallite is found in large quantity alternating with
beds of common salt at the Stassfurt salt-mines. It is the
principal source of potassium chlorid,e.

Its composition is represented by the formula

KMgCls,6H,0.

COMPOUNDS OF CALCIUM.

These compounds are very abundant in the mineral
kingdom. The most abundant and important are the car-
bonates, sulphates, phosphates, silicates, and the fluoride.
The carbonate is one of the most common of minerals ;
other native compounds are found less commonly. The
compounds named are insoluble or only very slightly solu-
ble in water.

Fluorite, Fluor Spar, CaF2.

Isometric. — Prevailing form is the cube; also frequently
compact and fine granular. It is sometimes colorless and
transparent, but usually has some light color, e.g., some
tint of green, blue, purple, or yellow ; rose-red and violet
shades are rare and highly prized. Streak light. H. = 4*
G. = 3. Below red heat the mineral phosphoresces, but
above that temperature it ceases to phosphoresce and loses
its color. The phosphorescent colors are independent of
the actual colors. That giving a green phosphorescence
is called chlorophane. Before the blowpipe the mineral de-
crepitates. It is very brittle.

Fluorite occurs in veins, also in beds, and sometimes as,
the gangue in metalliferous veins, especially of lead and

68 DESCRIPTIVE MINERALOGY

tin. It is the most abundant native compound of fluorine*
The massive varieties are worked into vases, candlesticks,
and ornamental objects. It takes a high polish, but is diffi-
cult to work because of its brittleness. It is decomposed
by sulphuric acid, with liberation of hydrofluoric acid, and
is used to obtain this acid for etching on glass. It is also
used as a flux in certain metallurgic operations. The Cum-
berland and Derbyshire districts of England are most noted
for its production.

Gypsum, Hydrous Calcium Sulphate, CaS04,20H2.

Monoclinic. — Crystals frequently of arrow-head form.
Occurs massive with foliated and granular texture, also
fibrous and in radiating forms.

Gypsum varies in color from white to yellow, red, brown,
and black. The crystals are generally more or less trans-
parent, other forms translucent to opaque. Luster silky,
vitreous to pearly. H. = 2. G. = 2.3. In thin plates flex-
ible, but not elastic. Before the blowpipe loses water,
becomes white, opaque, and exfoliates. In closed tube gives
off water easily ; dissolves in hydrochloric acid, and after
dilution gives a white precipitate with a soluble barium
salt.

Gypsum is the most widely distributed of the sul-
phates, and there are several varieties.

Alabaster. — This has a very fine granular texture, almost
compact to the eye.

Selenite. — Includes the crystalline forms, usually in trans-
parent plates.

Satin Spar. — A white, finely fibrous variety. Some of
, the fibrous varieties have a radiated structure and are then
called Radiated Gypsum.

Common Gypsum. — Compact and fine granular, may be
white, yellow, brown, red, or black. Gypsum occurs in ex-
tensive beds in limestone and clay strata. Common salt is a
very frequent mineral associate. When three-fourths of its
water is driven off from gypsum by heat it constitutes plaster

COMPOUNDS OF CALCIUM. 69

of Paris, so called because the gypsum quarries near Paris
have long been famous for supplying it. The plaster mixed
with water is used in taking casts, making moldings, etc.
Alabaster is carved into various objects, as statuettes, parlor
ornaments, etc. The name of alabaster is sometimes applied
to a variety of calcium carbonate. Gypsum, finely divided,
is also used as a fertilizer.

Anhydrite, CaS04.

This mineral resembles gypsum, and its tests are the
same except that it gives off no water when heated. It is
also harder and heavier than gypsum, and its crystalline
form is orthorhombic. H. = 3 to 3.5. G. = 3.

Apatite, Calcium Phosphate, with Chlorine and Fluorine.

Hexagonal. — Prevailing form hexagonal prism ; also
massive, sometimes globular with fibrous texture.

Color is usually some shade of green, but may be white,
yellow, reddish yellow, or brown. Luster vitreous to sub-
resinous, streak light. H. = 5. G. = 3.2. It often closely
resembles beryl in appearance, but is softer and more resin-
ous. It is readily soluble in hot nitric and hydrochloric
acids. Solutions treated with sulphuric acid give a
white precipitate. Nitric acid solution added to molybdate
of ammonium in excess gives immediately, or upon warm-
ing, a bright yellow precipitate.

Calcium phosphate is the main constituent of animal
bones. Coprolites and guano are the fossil excrements of
birds, and are chiefly composed of calcium phosphate, but
contain also the phosphates of ammonium, sodium, and mag-
nesium.

Apatite occurs in veins in Quebec and Ontario, often of
great purity, but generally mixed with rock material, such
as pyroxene, hornblende, calcite, and many others. Im-
mense deposits of phosphatic nodules occur in the Tertiary
formations of South Carolina and Florida. These nodules

7O DESCRIPTIVE MINERALOGY.

contain from fifty to sixty per cent of tricalcic phosphate
mixed with sand, calcium carbonate, and some organic
matter. The great importance of guano and apatite is due
to the phosphoric acid in their composition. Both are val-
uable fertilizers. The apatite, before use, is converted into
the soluble superphosphate of calcium by treatment with
sulphuric acid. The phosphate industries of the United
States are very important and extensive.

Calcite, Calcspar, CaCOs.

Rhombohedral. — Often coarse and fine fibrous, granular,
compact, and earthy.

There are many varieties of this mineral, and they vary
very much in color, from transparent white to yellow, red,
and mottled in the crystalline forms ; the compact forms
may be almost any dull shade to black. Typical crystals
have vitreous luster, sometimes pearly; fibrous variety is
often silky ; the others, from common to earthy in appear-
ance. Hardness (of crystals) 3. G. = 2.5 to 2.8. Some of the
earthy forms are very soft. Calcite is infusible, but when
heated gives off carbon dioxide and is reduced to quick-
lime, which when moistened gives alkaline reaction ; it is
acted upon readily, with effervescence, by the mineral
acids even when cold ; the solution in hydrochloric acid
diluted gives a white precipitate upon addition of sulphuric
acid.

Calcite is one of the most abundant and widely distrib-
uted of minerals, probably coming next to quartz in this re-
spect. Some of the most important varieties are mentioned
below.

Limestone. — This term is sometimes, and not improperly,
applied to all calcspars, but it is generally limited to the
granular and compact varieties. The granular include those
of a distinct crystalline granular texture, often glistening
owing to the facets of the grains ; architectural and statuary
marbles are the best examples. The latter must be of fine
grain, homogeneous texture, and pure color. The architec-

COMPOUNDS OF CALCIUM. 71

tural varieties may be of various shades of color and is used
for decorations as well as in structures.

The compact limestones include the crypto- crystalline
and non-crystalline varieties. Hydraulic limestone is one of
these ; it contains clay as an impurity, and produces a lime
that yields a mortar that will set under water. Slow ef-
fervescence, conchoidal fracture, and argillaceous odor inci-
cate, but do not insure, hydraulic properties.

Lithographic Limestone. — A very fine-grained compact
limestone ; its use is indicated by the name.

Oolitic Limestone. — Compact and often composed of con-
cretionary grains somewhat resembling the roe of a fish,
hence the name, from the Greek oon, an egg. If the grains
are larger, the stone is called pisolite, from the Latin pisum^
a pea. The grains are not always concretionary, but some-
times comminuted and rounded fragments. In each case
the grains are cemented together by calcium carbonate.

Chalk. — A compact but soft variety, mainly composed of
rhizopod shells.

Chemically deposited Limestone. — Under this head are in-
cluded the limestones deposited from water holding them in
solution. Some of the most important are: ,

Travertine. — Deposited from rivers and springs ; it is
often in variegated layers and makes a most ornamental
marble. Mexican onyx is an illustration.

Stalactites. — The cones and cylinders found depending
from the roofs of many caves.

Stalagmites. — Calcareous formations over the bottoms of
caves and often rising in cones, meeting similar projections
from above. These cave formations are frequently arranged
in different colored curved layers, and when broken across
give very beautiful effects. The cave deposits are made by
the waters which percolate into the caves. Luray Cave in
Virginia is one of the most celebrated in the world for these
formations.

Calcareous Tufa. — An irregular porous deposit frequently
incrusting twigs or similar objects and usually made by
small springs and rather turbulent waters.

DESCR

v i.

Rock
deposited from spring

In the case of all t h
first taken into solutio 1
solution, and is depos
water, or in some ca ><
itself.

Of the non-massiv •,
only necessary to mention a few :

Iceland Spar. — The name applied to the limpid, crystal-
line specimens.

Dog-tooth Spar. — Composed of crystals of scalenohedral
form ; frequently occurs as an incrustation.

Satin Spar. — The delicately fibrous variety, affording a
fine satin luster after polishing.

In addition to the varieties above described calcite occurs
in many other forms. The living and often fossil shells of
the mollusca are mainly composed of it as well as the many
forms of shell-limestone and coral-rock. It is also an essen-
tial constituent of marls. The granular and compact lime-
stones constitute immense rock formations in nearly all geo-
logical, ages and are found widely distributed. True chalk
is abundant in Europe, especially in England, but has only
been found in Texas and Kansas in this country. Marble is
a term applied to any limestone susceptible of a polish.
Besides its use in structures, limestone is the source of quick-
lime, which is employed in enormous quantity throughout
the world for making common mortar.

Arragonite, CaCOs.

This mineral has the same chemical composition as cal~
cite, but differs in crystalline form, being orthorhombic ; it
is also slightly harder and heavier. The action under the
blowpipe and acids is the same as that of calcite, except
that it crumbles to powder more easily after heating. It
receives its name from Arragon in Spain, where very fine
crystals have been found.

COMPOUNDS OF CALCIUM. 73;

Dolomite, Calcium-magnesium Carbonate, Magnesium Limestone,

CaMg(CO,)a.

Rhombohedral. — Granular and massive.

The massive varieties of dolomite vary in color from white
to gray, yellow, reddish, green to brown or black. The
lighter varieties have vitreous or pearly luster. H. = 3.5 to 4.
G. = 2.8 to 2.9, slightly harder and heavier than calcite.
Before the blowpipe reacts the same as calcite. It gives
sluggish effervescence with cold dilute acid, sometimes has
to be powdered for this action. It often cannot be distin-
guished from calcite without a chemical analysis.

Dolomite is a double carbonate of calcium and mag-
nesium and forms beds in rocks of all ages. It occurs
mainly in two forms :

1. The distinctly crystalline granular variety, usually of
white or yellowish-white colors, is generally designated as
Dolomite. Its external characters are often hard to distin-
guish from granular limestone.

2. The finely granular, almost compact variety is gener-
ally called Magnesium limestone ; it is often difficult to
distinguish from siliceous limestone.

Dolomite is a common marble in New York and the New
England States, and is largely used as a building-stone. It
is also very common in Kansas and other of the Western
States. Dolomite is a good building-stone where anthracite
coal is the fuel, but in cities where bituminous coal is the
fuel the greater amount of sulphur present in the coal is
found to result very injuriously to the stone. This stone
was selected for the new Houses of Parliament in London,
after the old ones were destroyed by fire in 1838. The
effects of the bituminous fuel in London have rendered it
necessary to protect the buildings by artificial preparations
such as soluble glass, etc. Some of the dolomites, such as
the Sing Sing marble, by cautious reduction, reducing the
magnesian carbonate with perhaps some (but not all) of the
calcium carbonate, gives a lime possessing hydraulic prop-
erties.

74 DESCRIPTIVE MINERALOGY.

Witherite, BaCO,.

Orthorhombic. — Crystals nearly hexagonal in form, like
modified hexagonal pyramids, but composed of repeated
twins, as shown by their optical properties, often in com-
pact aggregates of columnar or granular texture.

Witherite is a barium carbonate. Its color is white
through gray to yellowish ; luster vitreous or slightly resin-
ous ; streak white ; brittle. H. = 3 to 3.7. G. = 4.25 to 4.35.
When heated in forceps gives yellowish-green color to flame
and melts to a clear glass, opaque on cooling. Acted upon
by hydrochloric acid, effervesces less violently than calcite ;
the solution gives white precipitate with sulphuric acid,
insoluble in acids.

Witherite is used considerably in glass manufacture, and
the artificial carbonate is used as a poison.

Quartz, Silica, SiOa.

Hexagonal. — Common form, the hexagonal prism with
corresponding pyramidal ends. Granular, cryptocrystal-
line and compact.

Quartz occurs under a great variety of forms, but certain
properties are common to them all. H. = j. G. = 2.5 to 2.8.
Alone it is infusible before the blowpipe, but when heated
with sodium carbonate it fuses with effervescence, due to
the escape of carbon dioxide. It is not acted upon by the
common acids and shows no cleavage. Quartz may be con-
veniently divided into two series, the distinctly crystalline
or vitreous series and the cryptocrystalline or chalcedonic
series. Some of the more important varieties of each series
will be briefly described.

Crystalline or Vitreous Series.

The vitreous series have glassy luster and fracture and
include :

Rock Crystal. — Which is pure quartz, colorless, and trans-

SILICA. 75

parent. It is used in jewelry under the name of white-
stone and occidental diamond.

Amethyst. — Has a purple or bluish-violet color; perfect
specimens are highly prized. Color supposed due to
manganese.

Rose Quartz. — Has rose color, which becomes paler after
long exposure to light. Usually occurs massive, slightly
transparent. Color probably due to titanic acid and
manganese.

Smoky Quartz, Cairngorm. — Of a smoky or brownish-black
tint, believed to be due to organic matter.

Milky Quartz. — Of a milky color and sometimes a slightly
greasy luster, usually massive and almost opaque.

Cat's-eye. — A gray or greenish variety, presenting opa-
lescence when cut in convex form. Appearance due to
penetrating asbestos.

Aventurine. — Aventurine is a form of quartz with glisten-
ing spangles, due to the presence of scales of mica, iron
oxide, or other mineral. The basic color is usually red or
brown. The aventurine is frequently imitated in glass, but
such imitations can be detected by the inferior hardness.

There are several other varieties of vitreous quartz.
Some authors describe all the vitreous varieties as rock
crystal more or less pure.

Cryptocrystalline or Chalcedonic Series.

Chalcedony. — Waxy or horn-like in appearance ; varies
much in color, generally translucent ; frequently shows its
origin by deposition from siliceous waters ; occurs as sta-
lactites, lining cavities, and as incrustations.

Agate. — A mottled or cloudy chalcedony with different
colored layers made by successive depositions. When a
section is made across the layers the colored edges are
shown in more or less regular lines or bands. If the layers
are very irregular the section shows zigzag lines and the
stone is called fortification agate.

An agate containing moss-like or dendritic forms is called

76 DESCRIPTIVE MINERALOGY.

moss-agate. The colored layers are believed due partly to-
organic matter, partly to metallic oxides (Fe and Mn), and
largely to rate of deposition. The colors of agates may be
changed artificially, and this is sometimes done in agates cut
for ornaments.

Onyx. — An agate with plane layers ; these render it suited
for cutting into cameos. If the layers are alternately white
and sard, the stone is a sardonyx.

Carnelian. — A light red chalcedony.

Sard. — A deep red or brownish-red chalcedony, espe-
cially by transmitted light.

Chrysoprase. — An apple-green chalcedony, colored by
nickel oxide.

Flint. — A compact chalcedony usually dark brown or
gray. It occurs in great abundance in nodular forms in
the chalk-beds. It has conchoidal fracture and leaves sharp
edges in breaking.

Jasper. — An impure opaque chalcedony, color some shade
of yellow, red, brown, or black. Occasionally gray or green.
If in striped bands of such colors, it is called ribbon or riband
jasper.

Heliotrope or Bloodstone. — With green color and spots
of red ; the green color is due to some chlorite, and the red
to iron oxide. All the above varieties of quartz are suscept-
ible of polish and are used as gems or in ornamental work.

Granular Quartz. — In addition to the above varieties
many rocks consist of silica nearly pure, or quartz grains
firmly cemented together ; such are quartzite and quartz
sandstone. Buhrstone is a cellular quartz rock having much
the appearance of coarse chalcedony.

Silica is the most common petrifying material. It some-
times replaces calcite and fluorite in their crystalline forms,
thus giving pseudomorphous quartz. Silica is the common
petrifying agent of shells and wood. Silicified wood is
found in great abundance in Arizona, Wyoming (National
Park), Colorado, and other Western States. The petrified
forests of Arizona and Wyoming are very extensive ; the

SILICA. 77

first named have furnished specimens of agatized wood of
unsurpassed beauty.

Tridymite.

Hexagonal. — This mineral is a variety of silica whose
crystalline form belongs to the hexagonal system, but it usu-
ally occurs in minute, thin tabular forms. The crystals are
generally minute and six-sided, often in twins or fan-shaped
groups. Its properties are the same as quartz except that
it is completely soluble in a boiling solution of sodium car-
bonate. It occurs chiefly filling cavities in acidic volcanic
rocks, often associated with sanidin, hornblende, or augite,
and sometimes opal. G. = 2.28 to 2.33.

Opal

is an amorphous form of silica containing from three to
thirteen per cent of water. There are several varieties
differing widely in color. Opal is slightly less hard and
heavy than common quartz, has a glistening, resinous lus-
ter, and dissolves entirely in heated solution of potash ;
frequently decrepitates when heated. The finest specimens
give beautiful internal rainbow-reflections as the stone is
turned in the light.

The luster and the evident amorphous texture usually
sufficiently distinguish opal. Like other silica it is fre-
quently a petrifying material.

Fiorite, Siliceous Sinter.- — These terms include the siliceous
incrustations from hot springs ; they are usually more or
less porous, sometimes almost fibrous.

Geyser ite. — Includes the concretionary siliceous deposits
from geysers ; these deposits are very varied in shape, and
occur in great beauty and abundance in the Yellowstone
Park. The terms fiorite, geyserite, and siliceous sinter are
very often used synonymously.

Tripolite, or Infusorial Earth is another form of opal re-
sulting from the accumulation of diatom shells and the

DESCRIPTIVE MINERALOGY.

spicules of sponges. The polishing powder known as
Electro- silicon is composed of this material.

SILICATES.

Silica is the abundant acid oxide of the earth's crust, and
forms silicates with various metallic bases. The silicates are
the most impotant rock-making minerals.

An entirely satisfactory classification of the silicates,
based upon their composition, has not been accomplished,
as the definite constitution of the acids from which the sili-
cates result is not known.

The ordinary classification of the silicates is based upon
what appears to be the ratio between the oxygen in the basic
and acid anhydride parts of the silicate. The principle of this
classification is readily seen when the formulae of the sili-
cates are written after the dualistic method so as to show
this oxygen relation. Thus representing by R a dyad me-
tallic element, in the following table are written the gen-
eral formulae of the silicates named, with the formulae of
the acids from which they are supposed to be formed :

. . Add.

Orthosilicate ........ R2O2.SiO2 I to i SiO4H2 = SiO2.2H2O Orthosilicic

Unisilicates (Dana)

Metasilicate ......... RO.SiO2 ito2 SiO,H2 =SiO2.H2O Metasilicic

Bisilicates (Dana)

Trisilicate ........... 2RO.3SiOa 1103 Si3O8H4 = 3SiO22H8O Trisilicic

Disilicate ............ RO.2SiO, 1104 Si,O»H2 = 2SiO2.H2O Disilicic

There are many species in which the oxygen ratio is less
than i : i, as 3 14, 2 : 3. Such species are called subsilicates,
and it is evident that they contain a larger proportion of the
basic radicle than the examples given in the table. In addi-
tion it is thought probable that there are other silicic acids
from which natural silicates may result. Neither can a dis-
tinct line of demarcation be drawn between hydrous and
anhvdrous silicates.

SILICA TES. 79

The majority of the silicates come under the head of
metasilicates or orthosilicates, and are considered as derived
from the corresponding- acids, SiO,H2, metasilicic acid, and
SiO4H4, orthosilicic acid. The normal orthosilicates would
then be represented by R3SiO4 or R2O2SiOa, and the normal
metasilicate by RSiO3 or ROSIO,, in which R represents a
dyad metal. When a greater proportion of the acid or
basic radical is contained than the formulae indicate there
result respectively polysilicates or subsilicates. The group-
ing here adopted for the principal silicates is mainly in.
tended to emphasize and fix in mind their relationship and
importance as rock-forming minerals.

PYROXENE AND AMPHIBOLE GROUPS.

The members of these groups are silicates of various
bases, among which generally appear calcium, magnesium,
andiron; manganese, zinc, potassium, and sodium less often,
and aluminum still more rarely. More than one base is usu-
ally present, though some members of the group contain but
one. The two groups are closely related in composition
and crystalline form. Each group shows forms belonging
to different systems of crystallization, either orthorhombic,
monoclinic, or triclinic. The monoclinic species are most
important, the triclinic least important. The amphibole
group has prismatic cleavage of 124° 30' and 55° 30', while
that of the pyroxene group is nearly 90°. This cleavage
angle taken in connection with the build of the crystal
establishes the chief distinction between the groups. With
pyroxene the distinct crystals are usually short prisms,
often complex, in massive specimens lamellar or granular ;
with amphibole the distinct crystals are long prisms
and simple, in massive kinds columnar and fibrous. Only
the more important species of each group are here de-
scribed.

O DESCRIPTIVE MINERALOGY.

(A) Pyroxene Division,
(i) Mono clinic Section. — Pyroxene.

Distinct crystals usually in short stout prisms, often
complex, massive, granular or lamellar, sometimes fibrous
or compact. The more important varieties of this species
are silicates of two or more of the bases calcium, mag-
nesium, and iron, calcium being always present, with either
iron or magnesium or both ; aluminum in certain cases.
The color is usually some shade of green, brown, or black;
also occurs white. Luster varies from dull vitreous through
imperfectly resinous to slightly pearly. H. = 5 to 6. The
rectangular cleavage when evident distinguishes it from
amphibole. The more important varieties are :

Augite. — This is a very abundant and important mineral,
and is a silicate of calcium, magnesium, iron, and aluminum.
It is black or greenish black in color and opaque. It is the
common form of pyroxene in the basic eruptive rocks. The
term augite is sometimes used synonymously with pyroxene,
but more generally it is limited to the variety just
described.

Diallage is a thinly foliated or lamellar variety of augite.

Malacolite. — This is sometimes called white augite, and
is a calcium-magnesium pyroxene. The granular form is
frequently called white coccolite, from coccos, a grain. The
green granular form, green coccolite, contains calcium and
iron.

The varieties of the pyroxene species are very important
rock-making minerals.

(2) Orthorhombic Section.

The orthorhombic pyroxenes are magnesium, or iron
and magnesium, silicates. The species of the pyroxene
group under this section are :

Enstatite. — Which contains the smaller proportion of iron
oxide — not over five per cent — and sometimes iron is
absent. The color varies from grayish, yellowish, or

SILICATES. 8 1

•greenish white to brown. Luster vitreous to pearly.
H. = 5.5. G. = 3.1 to 3.3. It is infusible and not attacked by
acids ; strongly resembles the monoclinic pyroxenes.

Enstatite in a very pure state is a frequent constituent
of meteorites.

Bronzite. — This contains more iron than the preceding
and its color deepens from grayish yellow-green to olive-
green. The amount of iron oxide generally ranges from
5 to 14 per cent ; with a greater per cent of iron the bronz-
ite passes to the next variety.

Hypersthene. — This mineral contains more iron than
either of the preceding, the amount of iron oxide varying
from 14 to 30 per cent. Color is a dark greenish brown or
black, sometimes approaching a copper-red. Streak gray
•or brownish gray. H. = 5 to 6. G. = 3.4 to 3.5.

Hypersthene often has a characteristic iridescence due
to minute, interspersed foreign crystals, symmetrically ar-
ranged. B.B. it fuses to a black enamel, and on charcoal
yields a magnetic mass. This species is a common constit-
uent of certain of the eruptive rocks.

,y ^y^^

(i) Monoclinic Section. — Amphibole.

The species of the amphibole group form a series closely
related to those of the pyroxene group ; the general dis-
tinction between the two groups has already been indicated.
The amphibole species of this group are analogous to the
pyroxene species of the pyroxene group, being silicates of
the same bases, though potassium and sodium are more
frequently present.

Amphibole usually occurs in columns less stout than
those of pyroxene, often in bladed crystals, also fibrous and
granular; the cleavage more oblique than that of pyroxene.
The color of the amphibole varies from black to white
through many shades of green ; streak lighter than color.
Luster vitreous to pearly on fresh surfaces, fibrous varieties

82 DESCRIPTIVE MINERALOGY.

often silky. H. = 5 to 6. G. = 2.9 to 3.4. The principal
varieties of this species are :

Tremolite. — A white lime-magnesia amphibole. It usually
occurs as blades or needles penetrating the gangue with
which they are associated, sometimes radiated or aggregated
into columnar masses of silky luster. Tremolite most
often occurs with dolomite.

Actinolite. — Of the same composition as tremolite with
iron in addition, and occurring in the same way as aggrega-
tions of needles or blades or in radiating forms. It usually
occurs with serpentine.

Asbestus. — Both varieties of amphibole pass into asbestus.
Asbestus includes the finely fibrous forms, fibers easily
separable and resembling flax ; when the fibers are more
like silk it is called amianthus. When the fibers adhere
closely and the stone resembles petrified wood, it is called
ligniform asbestus. When the fibers are interlaced so as to-
make tough sheets, it is called mountain leather.

Asbestus is the only variety of the amphibole species
used in the arts. It is sometimes woven into lamp-wicks^
fire-proof cloths, etc. It is incombustible, and articles made
of it may be cleansed by throwing them into fire. Asbestus
is found at many localities in the United States, but generally
of inferior quality and only adapted for grinding, and use
for paints, cements, boiler and steam-pipe coverings, safe-
linings, etc. The greater portion of the mineral called as-
bestus, suitable for weaving into cloth is a variety of serpen-
tine and does not fall under this species. Canada supplies,
this serpentine form in large quantity.

Crocidolite. — This species of the amphibole group is a
silicate of iron and sodium. It occurs asbestiform, also-
massive and earthy. The color is lavender-blue or light
green. Luster silky or satin to dull. H. — 4. G. = 3. 2 to 3. 3.
In closed tube gives a little water which is slightly alkaline.
B.B. fuses easily with intumescence to a black magnetic glass
coloring flame yellow.

An altered form of this mineral is found abundantly in
South Africa and popularly called " tiger-eye " or " cat's-

SILICA TES. 83

eye." The alteration is due to the oxidation of the iron and
infiltration of silica. The altered mineral has a delicate but
distinct fibrous texture and chatoyant luster, with amber-
yellow to brown color. This form of the mineral has come
into frequent use as an ornamental stone.

Hornblende. — This term is often used as synonymous with
amphibole, but it is more generally applied to the dark-
colored varieties containing a larger per cent of iron ; it
occurs in dark green or black crystals, massive and com-
pact. Hornblende, like pyroxene, is an important rock-
making mineral. It is an essential constituent of the
plutonic rocks. Such difference as exists between horn-
blende and pyroxene is probably mainly due to the different
conditions under which they were formed, the composition
being substantially the same.

Chrysolite, Olivine, Peridot.

Chrysolite is the most important species of a group
of silicates of the same name. It is an iron and magnesium
silicate, color usually olive-green, but has different shades
passing to a yellowish brown or red ; streak uncolored,
sometimes yellowish or brownish. Hardness is about the
same as quartz.

Olivine is the most common variety of chrysolite ; it has
a dark olive-green or yellow-green color. It occurs very
generally disseminated through basaltic rock, sometimes in
masses.

Beryl, Emerald.

Hexagonal. — Prevailing form hexagonal prism, sometimes
massive.

Beryl is essentially a silicate of aluminum and beryllium
(glucinum). There are several varieties of this mineral ;
some are pellucid, but they are generally some shade of
yellow, green, or blue. Luster vitreous to resinous, streak
uncolored. H. =7.5 to 8. G.= 2.67 to 2.76. Infusible, though
it changes color under the blowpipe. The common vari-

84 DESCRIPTIVE MINERALOGY.

eties with less delicate shades of color are all included
under the name of Beryl simply ; color supposed to be due
to iron oxide. Emerald is of a rich green color ; it contains
a small per cent of chromium oxide, to which its color is
generally ascribed. Aquamarine includes the transparent
forms of very delicate shades of green or blue.

Fine specimens of beryl come from Siberia, Ceylon,
Colombia, and Brazil ; they have also been found at many
places in the United States — in Maine, New Hampshire, and
North Carolina, and several of the Western States. Very
large ones have been obtained in the two States first named.
Beryl in color and form often resembles apatite, but is much
harder.

Garnet.

Isometric. — Prevailing forms are the dodecahedron and
trapezohedron. Also occurs massive and granular.

Garnet is a cornplex silicate which may contain two or
more of the metals calcium, magnesium, aluminum, iron,
and chromium, the varieties being due to the different pro-
portions of these elements. Garnets vary much in color.
Luster vitreous to resinous. H.=6.$ to 7.5. G. = 3.i to 4.3.
The darker varieties may be fused without difficulty. The
more important and common forms are the following :

Almandite, or Almandine. — Various shades of light red to
brown. Those with clear color and considerable transpar-
ency are the precious garnets. Almandite is an iron-alumina
garnet.

Essonite, or Cinnamon-stone. — An alumina-lime garnet of a
cinnamon color.

Pyrope. — An alumina-magnesia garnet of a deeper red
color than almandine, sometimes almost black. It is also
called precious garnet when it is fairly transparent and has a
pure color. Pyrope is frequently found in small rounded
masses and grains.

Colophonite. — A lime-iron garnet, consisting of a mass of
grains of a brownish-red to brownish-yellow color ; has
resinous luster and generally gives iridescence when turned
in the light.

SILICATES. 85

The different forms of garnet often occur disseminated
through metamorphic rocks; are found in the gneiss rocks
about West Point. In this class of rocks the garnets are
usually almandine. The fine red garnets constitute the
carbuncle of the ancients.

Garnets are found at many places. Ceylon is noted for
its red garnets, but the richest gems come from Burmah.
Garnets are found at many places in the United States.
Fine specimens of pyrope abound in Arizona, New Mexico,
Colorado, and other Western States, and are the so-called
Arizona rubies.

Lapis Lazuli.

Isometric. — Usually massive. This mineral is a com-
plex silicate of aluminum and sodium and contains copper,
iron, snlphur, and chlorine. It has an azure-blue color and
vitreous luster. Its color is thought to be due to sodium
sulphide. When powdered it is dissolved by hydrochloric
acid with separation of gelatinous silica. The finest speci-
mens are much esteemed for making ornaments and for
inlaid work. The powdered mineral was formerly used as a
paint under the name of ultramarine ; this color is now pre-
pared artificially, and is very much cheaper than the natural
paint.

Mica.

This term embraces a group of minerals which are
essentially hydrous silicates of aluminum and an alkali
metal. Potassium is the alkali metal most abundantly and
commonly present. Sodium is often present, and in one
variety it entirely replaces the potassium. The next most
important constituents are lithium, iron, and magnesium,
the last-named metal being so abundant in some varieties,
that they are sometimes called magnesian micas; in these,,
however, potassium is present. Most of the micas contain
fluorine. The formulas for the different varieties of mica,
have not been precisely determined.

The micas belong to the monoclinic system and are,-

86 DESCRIPTIVE MINERALOGY.

characterized by a highly laminated structure and perfect
cleavage. The laminae are flexible and elastic.

Muscovite is one of the common micas, being a hydrous
silicate of aluminum, potassium, and iron. It has white or
silvery color, passing to various shades of yellow, brown,
and green. H. = 2 to 2.5. It is a common constituent of
granite, gneiss, and mica schist, and in these rocks usually
occurs in minute silvery scales.

Lepidolite is muscovite containing a little lithium, which
gives it a delicate lilac or rose-colored shade found only in
this variety.

Biotite. — Like muscovite, a hydrous silicate of aluminum,
potassium, and iron, but in addition containing a large per
cent of magnesium. It is generally greenish black to black
in color. It is even more common in the granitic arid met-
amorphic rocks.

Mica, in the clear transparent forms, has long been used
for furnace and stove doors and lamp-protectors. It is now
very largely used as an insulator in the construction of
dynamo machines. For this purpose the color is imma-
terial, but perfect cleavage is necessary, as the plates must
be of uniform thickness and often very thin. For insulating
purposes small laminae can be fastened together by suitable
mucilage so as to form large sheets. Mica is also ground
up and used for mural painting and in the manufacture of
wall-paper. It can thus be made to produce a metallic,
frosted, or spangled surface. The ground mica is also used
as an absorbent of nitroglycerin in certain mica powders.
For grinding, waste mica is generally used. Mica is chiefly
mined in this country in New Hampshire, North Carolina,
and South Dakota. Most of that now used in this country
is imported from India and Canada, though this will proba-
bly not be long done.

FELDSPAR.

The feldspars are essentially silicates of aluminum, potas-
sium, sodium, and calcium. They all contain aluminum, the
other metals alternating in the different species. The com-

SILICA TES. 87

mon and important forms of feldspar all belong- to the tri-
clinic system, except orthoclase, which is monoclinic. The
group has a hardness of from 6 to 7, and a specific gravity
of from 2.4 to 2.7.

Orthoclase, Common Feldspar, Potash Feldspar.

Monoclinic. — Prevailing forms, oblique prisms or deriva-
tives. Also massive, with lamellar or granular texture.
Sometimes finely compact.

A silicate of aluminum and potassium containing a
little sodium. Generally light or flesh color, though dark
colors are not uncommon, and there are various intermedi-
ate shades. It is similar in other respects to albite, except
that it has two cleavage planes at right angles to each other,
which, when evident, is sufficient to distinguish it from that
form. It is a common constituent of many of the igneous
and metamorphic rocks ; abundant in the gneiss about West
Point. Ground orthoclase is extensively used' as a glaze
and flux in the manufacture of pottery.

Sanidin. — Is a transparent and glassy form of orthoclase,
frequently in crystals imbedded in lava.

Adularia.—\s a white, clear orthoclase, often with pearly
opalescence.

Albite, Soda Feldspar.

Triclinic. — Usually in crystalline masses with more or
less lamellar structure.

In composition a silicate of aluminum and sodium ; color
generally white or gray, often of shades of blue, red, or
green ; subtranslucent. Is not acted upon by acids ; fuses
with difficulty and colors flame yellow.

Albite is a constituent of many crystalline rocks, such as
diorite, granite, and gneiss. The finest crystalline specimens
occur in granite veins. Albite frequently shows fine striae
on cleavage surfaces due to intersection of faces of crystal-
line laminae.

88 DESCRIPTIVE MINERALOGY.

Microcline.

This species is in composition nearly the same as ortho-
clase, but more generally contains sodium. It is, however,,
triclinic, though the cleavage angle varies but slightly from
a right angle.

There are many other varieties of feldspar, the more im-
portant of which are Anorthite, Labradorite, Andesite, and
Oligoclase. The first named is a calcium feldspar, and the
others are calcium and sodium feldspars. Anorthite and
Labradorite are sometimes called basic feldspars because
they contain less than 60 per cent of silica ; the others are
termed acid feldspars. Plagioclase is a general term often
used to include all the triclinic feldspars except microcline.
The feldspar species is one of the most important rock-mak-
ing minerals.

FELSPATHOID GROUP.

This group includes several silicates of aluminum and an
alkali metal, and in this respect is closely related to the feld-
spars. The group, however, have different crystalline forms
and physical properties, and in the arrangement of the sili-
cates already referred to they do not fall in the same class.
as the feldspars. The more important species of the fel-
spathoid group are given below.

Leucite, Amphigene.

Isometric. — Leucite generally occurs in crystals, grains, or
granular masses. The larger crystals often show inclusions
of foreign matter symmetrically arranged.

Leucite is a silicate of aluminum and potassium, the lat-
ter being sometimes replaced in small quantity by sodium.
Color usually dull white to dark gray ; streak white. H. =
5.5 to 6. G. = 2.4 to 2.5. Brittle with conchoidal fracture..
B.B. infusible, blue color with cobalt solution by ignition.

Generally found in recent eruptive rocks.

ft^ir

SILICATES. 89-

Nephelite, Nepheline.

Hexagonal. — Occurs in white columnar crystals, six- or
twelve-sided, also in granular masses and compact.

Nephelite is a silicate of potassium and sodium ; its color
is white or yellowish, massive varieties dark green, bluish
gray, brown or red ; luster vitreous to greasy. H. = 5.5 to 6.
G. = 2.55 to 2.65. Brittle, with semi-conchoidal fracture.
B.B. fuses to a colorless glass; gelatinizes with acids.

Nepljelite occurs in both recent and ancient lavas, also
in certain plutonic rocks.

Analcite, Analcine.

Isometric. — Occurs in trapezohedra, also massive and
granular ; cleavage cubical but imperfect.

Analcite is a hydrous silicate of aluminum and sodium.
Color is white, sometimes shaded gray, green, yellow, or
red ; luster vitreous. H. = 5 to 5.5. G. = 2.2. Brittle, with
semi-conchoidal fracture. Gives water in closed tube.
B.B. fuses without difficulty to a colorless glass. Gelatinizes
with hydrochloric acid.

Analcite is of frequent occurrence in cavities and seams
in basic volcanic rocks, also in granite and gneiss.

Of the species here included in the felspathoid group,
leucite and nephelite are richer in alkali than the feldspars,
and analcite is a hydrous silicate.

Topaz.

Orthorhombic. — Crystals commonly prismatic, generally
differently modified at the two extremities, faces usually
striated vertically ; also massive in columnar aggregates,
coarse or fine granular. Perfect cleavage parallel to base.

Topaz is a silicate of aluminum with part of the oxygen
replaced by fluorine; also frequently contains hydroxyl.
Its color varies from yellow, through gray and white to
shades of green, blue, or red ; luster vitreous ; streak white ;

pO DESCRIPTIVE MINERALOGY.

brittle. H. = 8. G. = 3.4103.6. B.B. infusible ; not affected
by acids, except partially by H2SO4. Distinguished by its
hardness, infusibility, brilliant and easy basic cleavage.

Topaz most generally occurs in the acidic igneous rocks,
as granite and rhyolite ; also in metamorphic schists. It is
frequently accompanied by fluorite, tourmaline, beryl, and
apatite. The transparent and colorless varieties are used
as gems, the pink crystals being most valuable.

Andalusite.

Orthorhombic. — Crystals generally nearly square prisms,
massive and indistinctly columnar, occasionally radiated and
granular.

Andalusite is a silicate of aluminum ; some of the alumi-
num is often replaced by iron. Color white, pearl-gray,
pink to brownish red and olive-green; luster vitreous;
streak uncolored; brittle. H. = 7.5. G. = 3. i to 3.2. B.B.
infusible ; not affected by acids. Heated with cobalt solu-
tion gives a blue color.

Occurs only as imbedded crystals, most commonly in
schists.

Kaolinite.

Kaolinite is a hydrous silicate of aluminum resulting
mainly from the decomposition of the feldspars. In the
course of time rocks containing these minerals, such as
granite, gneiss, etc., are disintegrated by aqueous and
atmospheric agencies, the disintegration being due to the
decomposition of the feldspars.

The feldspars in passing to kaolinite lose their alkaline
and lime bases and part of their silica and take up water.
It is thought that the carbon dioxide of the atmosphere and
other organic acids are the essential agents in removing the
bases from the minerals. With the change in the feldspar,
the rock crumbles, and both the kaolinite and the associated
constituents are eroded and carried away by the running
waters and eventually deposited.

SILICATES. 91

Kaolinite is ordinarily called kaolin. When pure it has
a soapy feel, white color, and when touched to the tongue
adheres strongly. When breathed upon it gives the well-
known clay odor, it is infusible, not acted upon by acids
under ordinary conditions, and yields water when heated in
a closed tube.

Common clays contain more or less kaolinite mingled
with eroded material from the parent rock and from the
rocks over which the depositing waters have passed. The
minerals most frequently mingled with the kaolinite are
finely divided quartz, feldspar, and mica.

Common clays usually contain some of the compounds of
iron, and if these are of such nature as not to withstand heat,
the clay will generally burn red, due to the transformation
of the iron compound into the red oxide. The ordinary
alterable iron compounds in clay are the limonite, carbon-
ate, or perhaps iron, combined with some organic acid. If
the iron be in some of the silicated forms, the clay does not
change color by heat. The well-known cream-colored
Milwaukee bricks are made of such clay.

The use of clay in brick-making is well known. If of
good clay, brick is one of the best building-stones to resist
heat. Porcelain is made of the purest kaolin, stoneware of
the less pure varieties. Fire-bricks are generally made of a
fine quality of clay, though they are sometimes composed
of a large per cent of silica.

Tourmaline.

Hexagonal. — Prism the prevailing form, with three (or
some multiple of three) sides. Sides usually striated or
channeled. Ends of crystals frequently unlike. Also
occurs massive.

Tourmaline is a complex silicate, essentially of aluminum
and boron, but with several other bases, the proportions of
which are believed to give the many different varieties.

The common forms are usually brown or some shade of
black, but there are various shades of red, yellow, and

92 DESCRIPTIVE MINERALOGY.

green. Generally translucent to opaque. H. = 7.5. It is
brittle, fractured surface uneven. Tourmaline when in
crystals is distinguished by the number of faces being some
multiple of three. Its hardness is usually sufficient to dis-
tinguish the dark varieties from resembling minerals.

Rubellite is the red tourmaline.

Indicolite is the blue tourmaline.

Tourmaline is also found in white, blue, and green colors.

This mineral usually occurs penetrating crystalline rocks;
it is not an essential constituent. The fine specimens are
highly prized as gems.

Specimens that rival any in the world in beauty have
been found in Maine, at Paris and Hebron. Fairly fine
specimens have been found in many other States of the
Union. Ceylon and Brazil have also given celebrated
crystals.

Talc.

Talc is a hydrous silicate of magnesium and nearly
always contains a little iron. Generally occurs in foliated
masses with a pearly luster, readily peeling off in layers ;
masses also compact and of fine scales, occasionally granular
and less often fibrous. Talc is usually of a greenish- white
color, but varies to other shades of green and to nearly pure
white. In the laminated variety H. = i to 1.5. The scales
are flexible but not elastic. Yields water with difficulty
when heated in closed tube. Infusible and not acted upon
by acids. All varieties have a greasy feel.

There is a number of varieties of this mineral, of which
the more important will be mentioned.

Talc. — This term is commonly limited to the more dis-
tinctly foliated varieties.

Steatite, Soapstone. — Fairly compact or finely granular in
texture, usually greenish gray or gray.

French Chalk. — The white laminated variety, used for
marking on cloth.

Indurated Talc. — An impure variety of a somewhat shaly
texture, with hardness of 3 to 4.

SILICA TES. 93

Talc occurs in many of the States and in Canada. Penn-
sylvania furnishes the greater quantity of the steatite,
though it is also mined in Virginia, North Carolina, and
South Carolina. It is trimmed into slabs for various uses —
as bath-tubs, laundry -tubs,, frames to hot-air registers, etc.
In the powdered form it is largely employed as a filler in
mineral paints and in fire-retarding paints. Fibrous talc is
extensively mined at Gouverneur, N. Y., and is largely used
to give weight and filling in the manufacture of paper.
This form passes under the name of mineral pulp. The
powdered form is also used as a lubricant for machinery and
for diminishing machinery friction generally. Boot-powder
is composed of it.

Serpentine.

This mineral, like talc, is also a hydrous silicate of
magnesium, but contains more water and less silica than
talc. It generally occurs massive and compact and finely
fibrous. Color is usually some shade of green, more often
green tinged with yellow, though sometimes nearly white.
Luster faintly resinous to oily. H. = 2.5 to 4; often has
greasy feel, but less so than talc. Yields water readily
when heated in closed tube, and changes color to brown.

Precious Serpentine. — When the color is a bright tint of
yellow-green and the mineral translucent. When the
mineral is opaque and the color dull it is common serpentine.

Chrysotile. — This is the finely fibrous variety and is largely
used under the name of asbestus. This is the mineral that
is, in this country, generally woven into fire-proof roofing,
clothes, etc. It is obtained in New York, but much more
abundantly in Canada, being called asbestus.

Verd Antique, Ophiolite. — This name is applied to a
mineral composed of a mixture of serpentine and lime-
stone. When polished it gives a marble, mottled, and often
of much beauty. Serpentine itself gives a marble, but
generally not so variegated as when calcite is present.
Pennsylvania furnishes a serpentine which is used as a
building-stone.

94 DESCRIPTIVE MINERALOGY,

Chlorite.

Chlorite is a general term applied to a group of minerals
which are hydrous silicates of magnesium and aluminum,
and in which iron and other metals are usually present in
small quantity ; less silica is present than in serpentine.
The term chlorite is also applied to the more important
varieties of this group, which are of extensive occurrence,
but whose compositions are not well determined and whose
forms are not distinctly defined. The distinctly crystallized
species are not of great importance. When the word is
used in the limited sense it refers to the dark green varieties
which occur foliated and massive and also in fine granular,
almost compact forms and finely fibrous. H. = i to 2.
Streak is whitish or slightly greenish, yields water in closed
tube. Color due to the large per cent of iron present.

MINERAL COAL.

This important substance is essentially composed of car-
bon, hydrogen, oxygen, a little nitrogen, and sulphur, to-
gether with some earthy matter which gives the ash. There
may also be a little moisture present and sometimes oc-
cluded hydrocarbons, but these are accidents in the coal.
Coal occurs massive and uncrystallized, is from brown to
black in color. H. = 1.5 to 2.5.

Perfect coal when pure may be divided into two general
classes, Anthracite and Bituminous, depending upon the
per cent of volatile ingredients present.

Anthracite. — This coal has a high luster, between vitre-
ous and metallic, color glistening-black, often iridescent.
H. =: 2 to 2.5. G. — about 1.6. Often gives conchoidal frac-
ture ; it burns with a pale blue flame. In this coal go to 95
per cent of the combustible matter is fixed carbon. It con-
tains from 5 to 12 per cent of earthy matter, which is left as
ash in burning. The volatile matter in the coal ranges from
three to seven per cent. It is sometimes called stone-coal or
glance.

MINERAL COAL. 9£

Bituminous Coal. — This coal has a dull or slightly resin-
ous luster. H. = 1.5 to 2. G. = about 1.3. It burns with a
smoky yellow flame.

In this coal the combustible matter contains from 45 to
85 per cent of fixed carbon, from 15 to 55 per cent of volatile
matter; there is present from i to 8 per cent of earthy mat-
ter. When the combustible matter contains from 80 to 85,
per cent of fixed carbon and 15 to 20 per cent of volatile
matter it is called semi-bituminous. When the volatile mat-
ter rises to 30 or 40 per cent it is full bituminous, and when
beyond this per cent it is highly bituminous.

Common bituminous coals are generally divided into
two kind, caking and non-caking. Caking coal softens
and becomes pasty in the fire, so that pieces in contact ad-
here, forming a solid mass. Non-caking coal burns freely
without softening. These varieties cannot be distinguished
by external characters, nor has the chemical difference be-
tween them been determined.

Cannel Coal. — A highly bituminous variety, of compact
texture, with little luster, and conchoidal fracture. It burns
brightly with much flame. It is very valuable for making
gas as well as for open-grate burning.

Brown Coal. — An imperfectly formed coal, in which the
conversion of the vegetable matter into coal has not beea
completed. It contains from 15 to 35 per cent of oxygen.
It is of a brownish-black or black color, streak brown.
When the woody structure is still clearly visible it is called
lignite.

Jet. — This is a very black, compact variety of brown coal.
It takes a high polish and is used for cheap ornaments.

In addition to these varieties a native coke has been found
in Virginia, probably resulting from the action of eruptive
rocks on bituminous coal. It resembles common coke, but
is more compact.

All the varieties of coal may contain greater or less pro-
portions of mineral impurities, giving other divisions de-
pending upon the degree of impurity. If the ash does not
amount to more than 8 or 10 per cent in anthracite, the coal

9 DESCRIPTIVE MINERALOGY.

may be considered as pure. The pure anthracite gives
more ash than the pure bituminous, which was to be ex-
pected, as the former results from a condensation of the
latter. The mineral matter making up the ash of pure coal
comes from the plants out of which the coal was formed.
It consists mainly of silica, alumina, oxide of iron, lime in
small quantity, and a little potash and magnesia.

The origin of coal and the location of the beds are given
in Geology.

TABLES FOR USE IN THE DETERMINATION
OF MINERALS.

THESE tables have been constructed with the view of
facilitating the determination of the minerals of the text.
The order of arrangement and the directions for use of
the tables are intended .to develop and improve the powers
of comparison and observation, as well as to bring about a
correct determination of the mineral species.

The minerals are classified under three general sub-
divisions, A, B, and C.

A includes all the minerals with a distinctly metallic
luster.

B includes all minerals that have not a distinctly metallic
luster, but have a colored streak.

C includes all minerals with an unmetallic luster and an
uncolored streak.

In the first subdivision (A) the minerals are again clas-
sified according to color ; in the second (B) according to
streak; and in the third (C) according to hardness; and in
each of these smaller classes the minerals are arranged in
the order of their hardness.

The tables consist of two principal parts ; in the first
are given the external characteristics of the minerals ; in
the second are described the effects of acids and of heat.
The former should always be examined first. Some speci-
mens can be determined from external characteristics alone,

TABLES fOR DETERMINATION OF MINERALS. 97

and many others can be limited to a small number of species.
The method of procedure in the determination of minerals
should be as follows:

Take up the specimen and note its luster, whether
metallic, semimetallic, or unmetallic ; if metallic, note its
color ; if semimetallic or unmetallic, determine its streak.
Finally, determine the hardness of the specimen. Now try
to place it as rapidly as possible in the table : in A by its
color first, then by its hardness; in B by its streak first,
then by its hardness ; in C by its hardness alone. When
the specimen under consideration is thus approximately
determined, see if the other characters given in its descrip-
tion correspond to what is observed in the specimen. This
is all that can be accomplished by the use of the first part
of the tables ; for further verification the directions in the
second part of the tables must be followed and the effects
of acids and heat observed. For a proper use of the tables
the student must be familiar with the contents of Chapter
II, which precedes, and must; also have instruction and as-
sistance in the use of the appliances of the mineralogicai
laboratory.

A.— MINERALS WITH

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Streak.

Hardness and
Tenacity.

Remarks.

I.— BED OB BROWN.

Copper

Copper red

H.=2.7

Malleable

Proustite

Scarlet ver-
milion

Scarlet, ver-
milion,

H.=2.5

Brittle

sometimes

orange
yellow

Bornite

(Erubescite)

Brownish
red

Dark gray-
ish black

H.=3.o
Brittle

Cuprite

Red to
brown

Brownish
red

H. =3.5104
Brittle

Rutile

Red to
brownish
red

Gray to
yellowish
brown

H.=6to6.5
Brittle

Cassiterite

Brown to
reddish
brown

Gray to
light
brown

H.=6 to 7
Brittle

Crystals isometric; occurs
usually massive and in
plates or strings penetrat-
ing the gangue; clings to
a file. G.>8

Generally found with other
ores of silver, especially
with pyrargyrite, cerargy-
rite, and native silver

Color decidedly more red
than that of chalcopyrite

Sometimes in octahedrons,
but often massive, gran-
ular,and earthy; frequent-
ly contains iron oxide^
G. = 5.8 to 6.1

Distinguished from tin ore
by not giving tin with
soda on charcoal

Practically the only ore ofi
tin. G.=6.8 to 7.1*

II.— YELLOW.

Gold

Golden yel-

Yellow

H. = 2.5

Crystals isometric, occurs

low

Malleable

usually in grains, strings,

or plates in a gangue of

quartz, the latter being

often discolored by iron-

Clings to a file. G.>i$

Chalcopyrite

Bronze yel-

Greenish

H.=4-2

Often tarnished and irides-

low

black

Brittle

cent, sometimes green on

surface ; purer varieties

have deeper color

METALLIC LUSTER.

No.

Composition.

Action of Acids.

Effects of

Heating.

Ag3AsS3

Cu3FeS3

Cu20

TiO,

SnOj

Acted upon by HNOs, hy-
drogen escaping ; addi-
tion of ammonia to diluted
solution gives blue color

Acted upon by HNO3 with
separation of sulphur

After careful roasting par-
tiallyactedupon by HNO3,
and addition of ammonia
to diluted solution gives
blue color

Acted upon by HNOs and
diluted solution gives blue
color with ammonia

No action

Not perceptibly acted upon
by acids

On charcoal fuses easily
and gives odors of sul-
phur and arsenic oxide;
white sublimate in open
tube. With soda and re-
ducing flame, bead of silver

Fuses readily to a black
magnetic globule

Fuses easily in forceps and
colors flame green; yields
bead of copper on char-
coal

B. B. infusible alone

B. B. alone infusible; with
soda on charcoal reduced
to metallic tin and gives
white coating ; requires
long blowing

CuFeS,

No action

After careful roasting par-
tiallyacted uponby HNO3,
and addition of ammonia
to diluted solution gives
blue color

Fuses without difficulty,
but no action with fluxes

Carefully roasted and'
mixed with soda and
heated on charcoal, gives
a globule of copper

100

A.— MINERALS WITH

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Streak.

Hardness and
Tenacity.

Remarks.

II. -YELLOW.

9 Pyrrhotite

Pyrite

Bronze yel-

Grayish

H. =3.5104

low

black

Brittle

Brass yel-

Brownish

H.=6

low

black

Brittle

III.-WHITE.

Silver

Silver white

H.=2.5

Malleable

Arsenopyrite

(Mispickel)

Tin-white
to gray-
ish

Grayish
black

H. = 5-5
Brittle

Usually slightly magnetic.
Composition varies, but
conforms to the general
formula FenSn-| i

Isometric; sometimes mas-
sive, but generally in
crystals disseminated
through rocks. Sides of
cubes often striated at
right angles to each other.
Harder than chalcopyrite

Isometric; occurs in strings
or plates disseminated
through the gangue;
clings to a file; generally
tarnished on exposed sur-
face. G. = 10.5

Hard, strikes fire with steej
and emits odor of garlic.
G.=6

IV.-GRAY.

Graphite

Iron gray

Black, shin-
ing

H. = i

Friable

Feels greasy, soils paper;
micaceous or scaly, rarely
compact. Often dissemi-
nated through rock in fine
scales. G. = 2.25

Molybdenite

Lead gray,
inclining
to black

Bluishgray,
shining

H. = i.5

Friable

Feels greasy; occurs thin,
tabular, or scaly; soils
paper. G.>4

Stibnite

Lead gray

Dark gray-
ish black

H.=2.5
Brittle

Burns in flame of candle;
slightly sectile. Princi-
pal ore

METALLIC LUSTER. '. ,,•/»*,

I £ 10 1

No.

Composition.

Action of Acids.

Effects of

Heating.

Fe7S6

FeS2

Acted upon by HC1 with
liberation of hydrogen
sulphide

Roasted first; slightly acted
upon by HC1; addition of
K4FeCy6 gives blue pre-
cipitate

B. B. fuses easily to a black
magnetic globule

B. B. sulphurous odor and
fuses to magnetic globule

FeAsS

Acted upon by HNO3; ad-
dition of HC1 gives a
white curdy precipitate,
soluble in ammonia. Cop-
per plate placed in nitric
solution becomes coated
with silver

On charcoal alliaceous
odor, giving white coating
on coal; leaves magnetic
globule. In closed tube
gives a black sublimate of
arsenic; sometimes red
and yellow sublimates

No action

MoSa Acted upon by HNO8, giv

ing a grayish residue of
molybdic oxide

Sb-Sa When pure, acted upon by

HC1; HNO3 causes a sep-
aration of sulphur and
antimony pentoxide

Mixed with niterand heated
in closed tube, deflagrates

In forceps colors flame
green; finely powdered,
gives sulphurous odor in
open tube

Fuses easily and gives
white fumes and volatile
white coating on charcoal

102

A.— MINERALS WITH

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Streak.

Hardness and
Tenacity.

Remarks.

IV.-GBAY.

Argentite

Blackish
lead gray

H.=2.5
Malleable

Galenite

Bluish gray

Dark gray

H.=2.7
Friable

Chalcocite

Blackish
lead gray

Dark lead
gray to
black

H. =2. 5103
Brittle

Tetrahedrite

Dark gray
to black

Dark gray
to black,

H.=3to 4
Brittle

and inclin-

ing to red

Tennantite

Blackish
lead gray
to black

Dark gray
to black,
sometimes

H.=3to 4
Brittle

reddish

Hematite

Specular
iron ore

Between
iron black
and dark

Cherry red,
brownish
red

H.=6.5
'Brittle

steel gray

Can be cut like lead when
massive; is usually finely
disseminated through the
gangue. Most common
ore of silver. G. - 7.3

Is chief ore of lead. Often
has characteristic cubical
cleavage which is easily
obtained. Also occurs in
granular masses; very of-
ten contains some silver
sulphide. The ore be-
comes more micaceous as
the silver sulphide in-
creases. G. > 7 «

Somewhat resembles argen-
tite, but is not sectile

Often a valuable ore of sil-
ver, the copper being in
part replaced by silver

Closely related to tetrahe-
drite, the antimony being
wholly or partly replaced
by arsenic

Hexagonal; occurs com-
pact, scaly, fibrous; some-
times slightly magnetic*
G.=4-9 t° 5-3

V.— BLACK.

Graphite

Iron black

Black, shiny

H. = i
Friable

Other characteristics the
same as the gray variety,
13 above

METALLIC

LUSTER.

103

No.

Composition.

Action

of Acids.

Effects of

Heating.

Ag,S

PbS

Cu,S

Cu8S7Sba

Cu8S7As2

Fe,03

Acted upon by HNO3, with
separation of sulphur; ad-
dition of HC1 gives a
white curdy precipitate,
soluble in ammonia. Cop-
per plate placed in nitric
solution becomes coated
with silver

Acted upon by HNO3, with
separation of sulphur and
formation of some lead
sulphate; addition of am-
monium sulphide gives
black precipitate

Acted upon by hot HNO3,
with separation of sul-
phur; solution coats knife
blade with copper

Acted upon by HNO3, and
addition of ammonia to
dilute solution gives blue
color. (Copper test)

Acted upon by HC1; addi-
tion of K4FeCy« to dilute
solution gives blue pre-
cipitate

Sulphurous odor in open
tube; fuses easily on char-
coal and gives globule of
silver

On charcoal decrepitates;
sulphurous odor; gives
yellow coating on coal
and yields globule of lead

On charcoal powder gives
sulphurous odor and
leaves globule of copper

Fuses easily on charcoal,
giving sulphurous odor
and white sublimate; a
globule of copper after
long heating with soda

Infusible, but easily be-
comes magnetic on char-
coal

No action

Same as 13 above

104

A.— MINERALS WITH

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Streak.

Hardness and
Tenacity.

Remarks.

V.— BLACK.

Argentite

Grayish

black

Gray black

H.=2t02.5

Malleable

Same as 16 above

Pyrolusite

Iron black
to bluish
black

Black, blu-
ish black,
sometimes
shining

H.=2t02.5

Brittle

The common ore of manga-
nese ; occurs compact to
unconsolidated. G.— 4.8

Pyrargyrite

Black, red
by trans-
mitted
light

Purplish
red

H.=2to 2.5
Brittle

Occurs with other ores of
silver. G. = 5.8

Stephanite

Black to
iron black

H.=2 to 2. 5
Brittle

Brittle with uneven frac-
ture. G. >6

Chalcocite

Grayish
black

H. = 2. 5 to 3
Brittle

Often tarnished blue or
green. G. = 5-5 to 5.8

Melaconite

Black to
gray

Black

H. = 3 to 4
Brittle to
earthy

Black masses and concre-
tions along with other
ores of copper. G. = 5.8
to 6.2

Chromite

Black, iron
black,
brown
black

Yellow,
gray or
dark
brown

H. = 5 to 5. 5
Brittle

Generally magnetic, some-
times strongly so. G.=
4-3

Magnetite

Iron black

Black

H. = 5.5
Brittle

[sometric ; granular or com-
pact ; black streak and
magnetic property usually
distinguish it. G. >5

Franklinite

Iron black

Brownish
black

H. = 5.5 to
6.5
Brittle

Isometric. Resembles mag-
netite, but generally has
more earthy black color,
usually feebly magnetic

Hematite

Between
iron black
and dark
steel gray

Cherry red,
brownish
red

H.=6.5
Brittle

Hexagonal. Occurs com-
pact, scaly, fibrous, some-
times slightly magnetic.
G. =4.9 to 5.3

METALLIC LUSTER.

ios

No.

Composition.

Action of

Acids.

Effects of

Heating.

23
24

Ag2S
MnOa

Ag3SbS<

Ag,SbS<

Cu2S

CuO

FeCr204

Fe,04

Oxides of
iron, zinc,
and manga-
nese

Fe303

Same as 16 above

Acted upon by HC1 with
evolution of chlorine

Same as 16 above

Amethystine bead with
borax in oxidizing flame

Acted upon by HNOa, with On charcoal fuses easily
separation of sulphur and with spurting, giving
antimony oxide. Copper
plate in nitric solution be-

comes coated with silver

Acted upon by HNO8, with
separation of sulphur.
Copper plate in nitric so-
lution becomes coated
with silver

Same as 18 above

Acted upon by HNOj, and
gives copper test with am-
monia as in 4 and 8

Not acted upon

Acted upon by HC1. Gives
iron test, same as 21 above

Acted upon by HC1 with
occasional evolution of
chlorine. Gives iron test
as in 21

Gives iron test with
K4FeCy6, same as 21

white coating of antimony
oxide. With soda in re-
ducing flame gives silver;
red sublimate in open
tube, white in closed

On charcoal gives sulphur-
ous odor; fumes and coat-
ing of antimony. With
soda a globule of silver

Same as 18 above

Gives copper with soda on
charcoal

Gives emerald green color
to bead of borax and salt
of phosphorus

B. B. infusible

Amethyst bead with borax,
bluish green bead with
soda

Same as 21

io6

A.— MINERALS WITH

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Streak.

Hardness and
Tenacity.

Remarks.

V.-BLACK,

Rutile

Black

Gray to

light
brown

H. =6 to 6.5
Brittle

Distinguished from tin ore
by not yielding tin with
soda on charcoal. G.=

4-2

Cassiterite

Black

Gray to
light
brown

H=6to7
Brittle

Principal ore of tin. G.=
6.8

B.— MINERALS WITHOUT

EXTERNAL CHARACTERISTICS.

No.

Species.

Luster and
Color.

Streak.

Hardness and
Tenacity.

Remarks.

I.-STREAK GRAY, BLACK, OB GREEN.

35 • Graphite

L. Semi-

Black or

H. = i

Luster sometimes dull or

metallic

dark gray

Friable

earthy black, other char-

C. Iron

acters same as 13

black to

dark gray

Coal

L. Resinous

Grayish

H. = 2.5

Usually shows lamination;

(Bitumin-

to vitre-

black

Friable

the cannel coal is compact

ous)

ous; some-

Brownish

Brittle

with large conchoidal

times

black

fractures. Decomposing

silky

pyrite in coal produces a

C. Black

gray or yellowish powder

with inky taste. G. =1.03

Melaconite

L. Unmetal-

Black

H.=2.5

A black powder or massive

Tenorite

lic

Friable

and compact; often stained

C. Black

greenish; soils fingers

when massive or pulver-

ulent. G.>5.5

Coal

L. Semi-

Black

H.=2.75

Hard, with high luster;

(Anthracite)

metallic;

Very

breaking with small con-

vitreous

brittle

choidal fracture. G. = i.6

C. Black

Amphibole

L. Vitreous

Dark gray

H. = 5-6

Monoclinic; crystals long

(Horn-

C. Black to

to green-

Tough

and slender, cleavage ob-

blende

greenish

ish gray

Brittle

lique, 124°; massive spe-

black

cimens have black color,

common luster, are often

made up of bladed crystals

intersecting in all direc-

tions. G.=3.3

METALLIC LUSTER.

107

No.

Composition.

Action of Acids.

Effects of

Heating.

33 TiOa No action

SnOa

Not perceptibly acted upon
by acids

Infusible alone

B. B. alone infusible; with
soda on charcoal yields
metallic tin and gives
white coating ; requires
long blowing

METALLIC LUSTER; STREAK COLORED.

No.

Composition.

Action of Acids.

Effects of Heating.

Carbon with
some hydro-
gen and
oxygen

CuO

Carbon

Magnesium,
calcium,
iron and
aluminum
silicate

No action

Acted upon by HNO3; ad-
dition of ammonia to dil-
uted solution gives blue
color

Thoroughly mixed with
niter deflagrates in closed
tube

In forceps burns with yel-
low flame. Thoroughly
mixed with niter, defla-
grates in closed tube

Gives copper with soda on
charcoal. Moistened with
HC1, colors B. B. pipe
flame azure blue

Burns without flame; gives
no odor. Thoroughly
mixed with niter, defla-
grates in closed tube

Anhydrous , fusible with
intumescence in forceps
or on charcoal

io8

B._ MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

No.l

Species.

Luster and
Color.

Streak.

Hardness and
Tenacity.

•_ Remarks.

I.— STREAK GRAY, BLACK, OR GREEN.

Pyroxene
(Augite)

L. Vitreous
C. Gravish
black,
greenish
black

Dark gray,
greenish
gray

H.=6
Tough
Brittle

Franklinite

L. Semi-
metallic to

Black

H.=6.25
Brittle

dull vitre-

ous

C. Black

Magnetite

L. Semi-
metallic,

Black

H.=6.25
Brittle

vitreous

C. Black

Monoclinic; crystals short
and stout, cleavage
nearly rectangular; gran-
ular varieties are called
coccolite; massive speci-
mens are often composed
of stout crystals with
ends projecting on the
surface. G.=3.4

Isometric; occurs in octa-
hedrons; usually slightly
magnetic due to Fe3O4.
Often occurs with red
zincite

Isometric; in small octahe-
drons; usually in granular
masses; magnetic, heavy.
G.>5

II.— STREAK BROWX.

Lignite

L. Dull,
generally ;
if shining,
resinous
C. Brown,

Brown,
verging
on black

H.=2.5
Friable

Sometimes laminated; gen- '
erally showing woody
structure; often earthy;
peat contains rootlets;
air-dried contains con-

black

siderable water. G. = i.2

Cuprite

(impure)

L. Common
C. Brown

Brown

H.=4

Brittle

Impure with clay; often
stained green on surface.
G.>4

Sphalerite

L. Resinous
Adaman-

Yellow to
brown

H.=4
Brittle

Isometric; cleavage dis-
tinct. G.=4

tine

Vitreous

C. Black,

brown

LUSTER; STREAK COLORED.

IOQ

No.

Composition.

Action

of Acids.

Effects of

Heating.

Magnesium,
calcium,
iron, and
aluminium
silicate

Oxide of Zn,
Fe, and Mn

Fe804

Same as for 31

Acted upon by HC1; after
dilution addition of
K4FeCy6 gives blue pre-
cipitate

Anhydrous; fusible with
intumescence in forceps
or on charcoal

Becomes magnetic; when
fused with soda and some
niter on platinum foil the
manganese present usu-
ally colors the mass green

Borax bead is bottle-green
in R. F., in O. F. it is yel-
low while hot, colorless
when cold

43 .

Carbon,
hydrogen,
oxygen

Cu,0

ZnS

Acted upon by HNO8; after
dilution, addition of am-
monia colors solution
blue

Effervesces in hot HC1 with
evolution of H2S

Burns with yellow flame in
forceps; gives off empy-
reumatic odors. Mixed
with niter deflagrates in
closed tube

Fuses easily in forceps and
colors flame green. Yields
bead of copper on char-
coal

Pulverized and heated on
charcoal gives sulphur-
ous odor ; slight zinc
fumes; coating near assay
which is yellow while hot,
white on cooling. In open
tube, very little (if any)
sublimate of sulphur;
slight odor of SO2 and an
acid reaction

110

B.— MINERALS WITHOUT

EXTERNAL CHARACTERISTICS.

No.

Species.

Luster and
Color.

Streak.

Hardness and
Tenacity.

Remarks.

II.— STREAK BROWN.

Limonite

L. Vitreous,

Yellowish

H. = 5-5

resinous,

brown

Brittle

silky,

pearly

C. Brown

Amphibole

L. Common

Yellowish

H. = 5.5

(Basaltic

C. Black

brown,

Brittle

hornblende)

issr

brown

Cassiterite

L. Adaman-

Gray to

H.=6.5

tine

light

Brittle

C. Brown

brown

to black

Rutile

L. Adaman-

Light

H.=6to6.5

tine

brown

Brittle

C. Reddish

brown to

red, black

III.— STREAK RED.

Usually earthy or botry-
oidal, with a fibrous tex-
ture. G. >4

Monoclinic ; cleavage of
crystals oblique 124°;
massive specimens often
are made up of bladed
crystals intersecting in all
directions. G. = 3.3

When of composition given
sometimes called basaltic

Principal tin ore. G.=6.8

Very like tin ore, dis-
tinguished as stated in 33

Hematite

(Red chalk)

L. Common
C. Dark red

Brownish
red

H.=2

Friable

Massive, pulverulent, or
compact; earthy; rather
light

Cinnabar

L. Adaman-
tine
C. Cochi-
neal red

Scarlet

H.=2 102.5
Friable

Massive granular, glisten-
ing in specks; earthy
when impure; volatile.
G. from 3 to 8, > 8 when

pure

METALLIC LUSTER; STREAK COLORED.

i u

No.

Composition.

Action of Acids.

Effects of

Heating.

46 2FeaO3,3HaO

Magnesium,
calcium,
iron, and
aluminum
silicate

SnOa

TiO5

Acted upon by HC1; after
dilution addition of
K4FeCy6 gives blue pre-
cipitate

Not perceptibly acted upon
by acids

Not acted upon

Gives off much water easily
in closed tube. Borax
bead is bottle green in R.
F. ; in O. F. yellow while
hot, colorless cold. On
charcoal becomes black
and magnetic

Anhydrous. In forceps or
on charcoal fuses with in-
tumescence

B. B. alone infusible; with-
soda on charcoal yields
metallic tin and gives
white coating; requires,
long blowing

Infusible alone

Fea03

HgS

Slightly acted upon by
HC1; addition of K4FeCy6
to dilute solution gives
blue precipitate

Not acted upon by either
nitric or hydrochloric
acid: attacked by aqua
regia with separation of
sulphur

On charcoal becomes mag-
netic if not too impure.
Often gives off water in
closed tube, due to clay
present

Heated in closed tube with
sodium carbonate gives
sublimate of i^ercury in
small globules; alone
gives a black sublimate,
wholly volatile when pure.
In open tube gives sul-
phurous odor

112

B.— MINERALS WITHOUT

EXTERNAL CHARACTERISTICS.

No.

Species.

Luster and
Color.

Streak.

Hardness and
Tenacity.

Remarks.

III.— STREAK RED.

Proustite

'54

Pyrargyrite

Cuprite

Hematite

L. Adaman-
tine to dull
C. Scarlet
vermilion

Scarlet ver-
milion

H.=2 tO 2. 5

Brittle

Generally found with other
ores of silver. See 2, G.
= 5-6

L. Adaman-
tine todul]
C. Black to
deep red

Purplish
red

H.=a.S
Brittle

Occurs with other ores of
silver, G.=5.8

L. Adaman-
tine, semi-
metallic,
common
C. Carmine
red, red-
dish lead

Brownish
red

H.=4

Brittle

Cleavage distinct; often
impure from clay; .copper
ores are often stained
green on the surface. G.
= .5.8 to 6.1

gray

L.Common,
semi-me-
tallic
C. Dark
red. Part-
ly steel
gray

Brownish
red

H. =5 (vari-
able)
Brittle

Massive, granular, fibrous,
lenticular, pulverulent,
rarely botryoidal. G.>4

IV.-YELLOW.

Limonite

L. Common

Yellow

H. = i

Usually earthy, containing

(Yellow

C. Yellow

Friable

much clay; very light

ocher)

Sulphur

L. Resin-

Straw yel-

H.=2

G.-2

ous, ada-

low '

Brittle

mantine

Friable

C. Sulphur

yellow,

grayish

yellow

METALLIC LUSTER; STREAK COLORED. 113

No.

Composition.

Action of Acids.

Effects of

Heating.

52 AgaAsSs

AgsSbSs

CuaO

Fe,0s

Acted upon by HNO3, with
separation of sulphur

Acted upon by HNO3, with
separation of sulphur.
Copper plate in nitric so-
lution coated with silver

Acted upon by HNOs; ad-
dition of ammonia to di
lute solution gives blue
color

Acted upon by HC1; addi-
tion of K4FeCy« to dilute
solution gives blue color

On charcoal fuses easily
and gives odors of sul-
phurous and arsenic
oxides. White sublimate
in open tube. With soda
and reducing flame bead
of silver

On charcoal fuses easily,
with spurting, giving
white coating of antimony
oxide. With soda in re-
ducing flame gives silver;
red sublimate in closed
tube, white in open

B. B. colors flame green
and fuses readily, yield-
ing metallic copper on
charcoal

Anhydrous; becomes mag-
netic on charcoal

Acted upon by HNOs; ad-
dition of K4FeCy6 to di-
lute solution gives blue
precipitate

Becomes magnetic, if not
too impure. Gives much
water easily

Burns with blue flame and
sulphurous odor

114

B.— MINERALS WITHOUT

EXTERNAL CHARACTERISTICS.

No.

Species.

Luster and
Color.

Streak.

Hardness and
Tenacity.

Remarks.

IV.-YEL.L.OW.

Cinnabar
(impure)

L. Common
C. Yellow-
ish red,
cochineal

Yellow

H.=2.25

Friable

Massive granular, glisten-
ing in specks; earthy,,
containing clay

red

Sphalerite

L. Resin-
ous, ada-
mantine
C. Gray,
brown

Light yel-
low to
brown

H.=4
Brittle

Isometric ; cleavage of
crystals eminent; massive
Missouri blende is glis-
tening on a fresh surface;
often contains iron.

G.=4

Siderite

L. Vitreous
to pearly
C. Yellow,
yellowish

Pale yellow,
brown
when
weathered

H.=4
Brittle

Rhombohedral; crystals
often curved; often brown
or black by weathering.
G.=4

gray to
yellowish

brown

Zincite

L. Adaman-
tine
C. Red,

Orange
yellow,
brownish

H.=4
Brittle

Cleavage distinct, often in
laminated aggregations;
occurs with Franklinite.

orange,
brown

yellow

G.>4

Limonite

L.Common,
silky
C. Brown

Brownish
yellow,
ocher
yellow

H. = 5.5
Brittle

Usually earthy or botry-
oidal, with a fibrous tex-
ture; bog ore is sometimes
loose, porous and earthy.
G.>4

Amphibole
(Basaltic
horn-
blende)

L. Common
C. Brown-
ish black

Grayish
yellow,
ocher
yellow

H. = 5.5
Brittle

Monoclinic; cleavage
oblique, 124°; crystals
usually long and slender,
often acicular or bladed;

massive specimens are
nearly black and some-
times made up of bladed
crystals intersecting in
all directions. When of

composition given some-
times called basaltic horn-

blende

METALLIC LUSTER; STREAK COLORED. 115

No.

Composition.

Action

of Acids.

Effects of

Heating.

HgS

ZnS

FeCO3

ZnO

2FeaO3,3H2O

Magnesium,
calcium,
iron, and
aluminum
silicate

Not acted upon by either
nitric or hydrochloric
acid. Attacked by aqua
regia with separation of
sulphur

Acted upon by HC1, pro-
d u c i n g effervescence,
evolving H2S

When powdered, hot HC1
acts upon it, producing
effervescence; addition of
K4FeCye to dilute solution
gives blue precipitate

Acted upon by acids

Acted upon by acids; addi-
tion of K4FeCye to dilute
solution gives blue pre-
cipitate

Mixed with soda and heat-
ed in closed tube gives
small globules of mercury
on side of tube; alone
gives a black sublimate.
In open tube gives sul-
phurous odor

On charcoal sulphurous
odor, zinc fumes; coating
(near assay) which is yel-
low while hot, becoming
white on cooling

Blackens and becomes
magnetic in reducing
flame

On charcoal, zinc fumes;
coating (near assay) which
is yellow while hot, be-
coming white on cooling

Becomes magnetic in re-
ducing flame; gives much
water in closed tube

Anhydrous; on charcoal or
in forceps fuses with in-
tumescence

B.— MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

No.

Species.

Luster and
Color.

Streak.

Hardness and
Tenacity.

Remarks.

V.— STREAK GREEN.

Chlorite

L. Common,

Grayish

H. = 2.s

Schistose in structure; often

pearly

green

Friable

earthy by weathering; its

C. Dark

fracture is micaceous,

green

compact, or earthy; cleav-

age eminent, folia flexible

but not elastic

Serpentine

L. Resinous

Grayish

H.=3

Amorphous; massive; when

(impure)

(weak)

green

(variable)

impure it is earthy, when

C. Green,

Friable

pure its fracture is splin-

yellow,

Brittle

tery; unctuous feel; when

and some-

breathed upon smells bit-

times

ter; often mixed with cal-

white;

cite

rarely

dark

^>-~

^Chrysocolla

L. Vitreous

Bluish

H.=2.4 to 3

Amorphous; often reni-

to earthy,

green to

Friable

form; compact in texture

resinous

white

Brittle

and fracture; accompanies

C. Green

when pure

other ores of copper, es-

pecially malachite; seldom

pure

Malachite

L. Vitreous,

Emerald

H.=3.5

Often reniform ; compact,

pearly,

green,

Brittle

fibrous, or earthy. G.=4

silky

paler than

C. Emerald

color

green

Crocidolite

L. Silky to

Same as

H.=4

Opaque

dull

color

Fibers

C. Laven-

slightly

der blue

elastic

or leek

green

Pyroxene

L. Common

Grayish

H.=5.S

Monoclinic; crystals short

(Common

C. Blackish

green

Brittle

and stout, cleavage dis-

augite)

green

tinct, nearly rectangular;

usually massive granular

or composed of stout crys-

tals with ends projecting

on surface

LUSTER; STREAK COLORED.

117

No.

Composition.

Action

of Acids.

Effects of

Heating.

Hydrous,
magnesium
iron, and
aluminum
silicate

Hydrous,
magnesium
silicate

Hydrous,
copper
silicate

Hydrous,
copper
carbonate

Iron and so-
dium sili-
cate; a form
of asbestos

Magnesium,
calcium,
iron, and
aluminum
silicate

HaSO4 and HC1 act upon it
with a separation of silica

Acted upon slightly by
HNO3 ; addition of am-
monia to dilute solution
gives blue color. In HC1
decomposes with separa-
tion of SiO2 without gelat-
inization

Acted upon by HNO3
diluted, addition of am
monia colors solution
blue. Effervesces with
acids

Not acted upon by acids

Gives off water readily;
does not change color

Gives off much water very
readily; color changes to
brown

Gives off much water read-

B. B. decrepitates and
blackens ; colors flame
green; gives off much
water easily

In closed tube gives a little
water. B. B. fuses to a
black magnetic glass, col-
oring flame yellow

Fusible with intumescence.-

B.— MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

No.

Species.

Luster and
Color.

Streak.

Hardness and
Tenacity.

.Remarks.

V.-STREAK GREEN.

Amphibole

L. Common

Grayish

(Common

C. Blackish

green

horn-

green

blende)

. = 5.5

Brittle

Monoclinic ; crystals long
and slender, often acicu-
lar; cleavage oblique, 124°;
granular or lamellar; usu-
ally a mass of bladed crys-
tals

TI.-STREAK BLUE.

Chrysocolla

L. Vitreous,

Greenish

H.=2.4to 3

Amorphous ; often reni-

resinous

blue, smalt

Friable

form; compact in texture

C. Blue

blue

Brittle

and fracture , accompa-

nies other ores of copper,

especially malachite

Azurite

L. Vitreous

Smalt blue

H.=3-75

Often in incrustations; com-

C. Lazuli

Brittle

pact, fibrous, or earthy.

blue

G.=4

Lapis Lazuli

L. Vitreous

Smalt blue

H.=5.5

Often contains scales of

C. Lazuli

Brittle

mica ; usually compact.

blue

G. = 2.5

C.— MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Luster.

Hardness and
Tenacity.

Remarks.

I.-VERY SOFT.

Calcite

White

Common

H.— 0.5 to i

Usually a soft, white, por-

(Rock milk)

Pulverulent

ous, earthy mass ; very

light

LUSTER; STREAK COLORED.

119

No.

Composition.

Action of

ids.

Effects of

Heating.

Magnesium,
calcium,
iron, and
aluminum
silicate

Fusible with intumescence

Hydrous,
copper sili-
cate

Hydrous,
copper car-
bonate

Sodium, alu-
minum
silicate, with
sodium sul-
phide and
sulphate

Acted upon by HNO3; addi-
tion of ammonia to dilute
solution gives blue color.
In HC1 decomposes with
separation of SiO2, with-
out gelatinization

Acted upon by HNOsI solu-
tion diluted, gives blue
color on addition of am-
monia. Effervesces with
acids

Slowly acted upon by HC1,
giving odor of HaS

Gives off much water easily

B. B. decrepitates and
blackens ; colors flame
green. Gives off much
water easily

Fusible; loses its color

LUSTER; STREAK WHITE OR LIGHT GRAY.

No.

Composition.

Action of Acids.

Effects of

Heating.

CaCO,

Acted upon with efferves-
cence by HNO3 and HC1;
addition of H2SO4 to di-
luted solution gives white
precipitate

Infusible; assay after igni-
tion reacts alkaline

120

C.— MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Luster.

Hardness and
Tenacity.

Remarks.

I.-VEBY SOFT.

Kaolinite

White

Pearly

H. = i

Usually a soft, white, im-

Friable

palpable earthy mass, with

unctuous feel and clayey

taste and odor. Ordinary

clay consists largely of

kaolinite

Talc

White,

Eminently

H. = i

Usually in foliated or com-

green

pearly

Friable

pact masses, with an unc-

Sectile

tuous feel; folia flexible;

cleavage eminent

Calcite

White, gray

Common

H. = i

Usually a compact, white

(Chalk)

to brown

Friable

mass, composed of shells.

of foraminifers

Cerargyrite

Gray to

Resinous to

H. = i to 1.5

Very valuable ore of silver;

(Horn sil-

brown,

dull

Highly

easy of treatment; com-

ver)

green, and

sectile

mon in South America,

blue

when pure

Mexico, and southern

United States. Plate of

iron rubbed with it be-

comes silvered. G. = 5-5

Niter

White

Vitreous

H. = i.75

Taste saline and cooling ;

Friable

occurs in incrustations or

Brittle

crystallized in right rhom-

bic prisms

80"

Gypsum

White,

Vitreous,

H.=2

Occurs compact, fibrous,

gray, yel-

silky,

Friable to

and foliated, sometimes

low, red,

pearly

brittle

fine granular; cleavage

and

eminent; folia flexible.

brown

G. = 2.3

Sulphur

Yellow,

Adaman-

H.=2

Compact, in crusts or pul-

grav»

tine, resi-

Brittle to

verulent. G.=2

brown

nous

friable

Mica

Gray,

Pearly

H.=2.5

Usually in foliated or mica-

(Muscovite)

white,

Friable

ceous masses or thin

pale yel-

sheets; cleavage eminent;

low or

folia tough and elastic

brown

LUSTER; STREAK WHITE OR LIGHT GRAY.

No.

Composition.

Action of Acids.

Effects of

Heating.

Hydrous, alu-
minum sili-
cate

Hydrous,
magnesium
silicate

CaCO,

AgCl

KN09

CaSO4,2H2O

Hydrous, po-
tassium,
aluminum
silicate

No action

Gives off much water read-
ily

Exfoliates before blowpipe.
Yields very little water (if
any) with difficulty

Acted upon by HNO3 and Infusible; assay after igni-
HC1 with effervescence ;! tion reacts alkaline
H2SO4 added to dilute so-l
lution gives white precipi-
tate

Not acted upon by HNOs or Fuses in flame of candle ; on
HC1, but soluble in am- charcoal, metallic bead of
monia silver

Fuses in closed tube; bits
of charcoal dropped in
cause deflagration

Fuses; leaves assay which
is alkaline. Gives off wa-
ter easily

Dissolves in hot HC1 or
HNO3; after dilution ad-
dition of barium chloride
gives white precipitate

Burns with a blue flame
sulphurous odor

Yields little water in closed
tube

122

Q— MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Luster.

Hardness and
Tenacity.

Remarks.

I.-VERY SOFT.

•83

Mica

Black

Pearly

H.=2.5

Usually in foliated or mi-

(Biotite)

Brittle to

caceous masses or thin

friable

sheets; cleavage eminent;

folia tough and elastic

Chlorite

Green;

Pearly

H.=a.5

Schistose in structure; of ten

rarelv

Friable

earthy by weathering; its

bluish

fracture is micaceous,

red

compact, or earthy; cleav-

age eminent; folia flexi-

ble but not elastic

«5

Halite

White,

Vitreous to

H. = 2.0

Isometric, in cubes; mas-

gray, red

resinous

Brittle to

sive, compact, or granular;

friable

taste saline

Cryolite

White to

Vitreous to

H.=2.5

Massive; fracture uneven.

brown

greasy

Brittle

G.=3

Anglesite

White,

Adaman-

H.=2.7 to 3

G.=6.i to 6.4

gray to

tine to

Brittle

yellowish

vitreous

Carnallite

Red

Vitreous to

H. = 2.7

Soluble in water, bitter

greasy

Sectile

taste, deliquescent

II.— SOFT.

Calcite

All colors;

Vitreous

H.r=3

Crystals and cleavage

white,

Brittle

rhombohedral ; usually

gray, and

compact, granular, or

reddish

fibrous ; sometimes tufa-

common

ceous ; impure varieties

often contain clay and sil-

ica. G. = 2.7

Anhydrite

Gray,

Vitreous,

H.=3

Usually compact ; harder

white, and

resinous,

Brittle

and heavier than gypsum;

bluish

pearly

fracture often splintery.

gray

G.=3.o

123
LUSTER; STREAK WHITE OR LIGHT GRAY.

No.

Composition.

Action of Acids.

Effects of

Heating.

Hydrous,
potassium,
magnesium
iron, alu-
minum
silicate

Hydrous,
magnesium,
iron, alu-
minum
silicate

NaCl

Fluoride of
sodium and
aluminum

PbSO4

Mixture of
potassium
and mag-
nesium
chlorides

Soluble in H2O; addition of
solution of silver salt
gives white, curdy precipi-
tate of silver chloride.

Yields little water in closed
tube

Gives off a moderate quan-
tity of water rather read-
ily; does not change color

Fusible ; colors flame yel-
low

Fuses easily in flame of
candle ; colors flame yel-
low

Fuses easily; metallic lead
on charcoal

Fuses easily

CaCOs

CaS04

Acted upon by HC1 and
HNOs, effervesces. Solu-
tion diluted, addition of
HaSO4 gives white precip-
itate

Dissolves in hot HC1 and
HNO3; addition (after di-
lution) of barium chloride
gives white precipitate

Infusible; assay after igni-
tion reacts alkaline

Fuses; assay after ignition
reacts alkaline ; gives off
little or no water

124

C.— MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Luster.

Hardness and
Tenacity.

Remarks.

II.-SOFT.

Cerussite

White to
gray

Adaman-
tine to

H. = 3 to 3.5
Brittle

Occurs massive and stalac-
titic. G.=6.5

vitreous

Witherite

White

Vitreous
to resi-

3 to 3.5
Brittle

G.=4.3

nous

Chrysocolla

Verdigris
green, sky
blue

Shimmer-
ing (vitre-
ous, silky)

H.=3-5
Brittle

Amorphous ; often reni-
form; compact in texture
and fracture; accompanies
other ores of copper, es-
pecially malachite

Aragonite

White,gray,
pale yel-
low

Vitreous,
silky

H.=4
Brittle

Common in columnar ag-
gregations ; harder than
calcite. G.=2.9

Serpentine

Yellow,
green, and
sometimes
white;
rarely
dark

Resinous
(weak)

H.=4

Brittle,
friable

Amorphous; massive; when
pure its fracture is splin-
tery, when impure it is
earthy ; unctuous feel ;
when breathed upon
smells bitter; often mixed

green

with calcite

Sphalerite

Yellowish

Adaman-
tine

H.=4

Brittle

Isometric, cleavage of crys-
tals eminent ; massive

Missouri blende is glisten-
ing on a fresh surface.
G.=4

Fluorite

White,
grayish,
light
greenish
and
bluish,

Vitreous

H.=4

Brittle

Isometric ; cleavage octa-
hedral, distinct ; occurs
crystallized, also massive,
granular ; generally 1'ght
colors. G.=3

common

Dolomite

White or
grayish

Vitreous,
pearly

H.=4
Brittle

Rhombohedral ; usually a
crystalline mass ; often
brown by weathering ; a
little harder and heavier

than calcite. G.=2.g

125-

LUSTER; STREAK WHITE OR LIGHT GRAY.

No.

Con

Q position.

Action of Acids.

Effects of

Heating.

'93

'94

•96

PbCO5

BaCO,

Hydrous,
copper
silicate

CaCO<

Hydrous,
magnesium
silicate

ZnS

CaF,

CaMg(C03),

Readily acted upon
HNO3, effervesces

by Yields lead with soda on
charcoal, alone if heated
carefully

Acted upon by HC1 with
effervescence and dilute
acid solution gives white
precipitate with H2SO4

Acted upon by HNO3; ad-
dition of ammonia colors
solution blue. Decom-
posed by HC1 with separa-
tion of white silica, with-
out gelatinization

Acted upon by HC1 with
effervescence ; after dilu-
tion, addition of sulphuric
acid gives white precipi-
tate

Effervesces with HC1
strong odor of HaS

Dissolves quietly in HC1
solution diluted, netraliz-
ed with ammonia and ox-
alic acid added, gives a
white precipitate

When powdered, acted upon
by HC1 with efferves-
cence; after dilution, addi-
tion of H2SO4 gives white
precipitate

Fuses easily, color flame to
yellowish green.

Gives off much water easily

Infusible; assay after igni-
tion reacts alkaline
Anhydrous

Gives off much water very
readily; changes color to
brown

Pulverized, heated on char-
coal, sulphurous odor;
slight zinc fumes; coating
(near assay) yellow while
hot, white on cooling

Phosphoresces and decrep-
itates; fuses; assay after
ignition reacts alkaline

Infusible ; assay after igni-
tion reacts alkaline

126

C— MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Luster.

Hardness and
Tenacity.

Remarks.

II.-SOFT.

99 Siderite

100

101

Smithsonite

Calamine

Yellow,
yellowish

Vitreous to
pearly

H.=4
Brittle

gray,
yellowish
brown

Gray, green,
blue,
brown to

Vitreous,
pearly to
dull

H. =4.5 to 5
Brittle to
friable

white

Gray, yel-
low to

Vitreous to
dull

H. =4.5 to 5
Brittle

brown

Rhombohedral; crystals of-
ten curved; often brown
or black by weathering.

Found in veins, but more
generally in deposits of
limestone; usually results
from alteration of ZnS.

Stalactitic, botryoidal, fib-
rous, also massive and
granular. G.=3.5

III.-HARD.

102

Pyroxene

Dark green,

Semi-metal-

H.=4.75

Monoclinic; lamellar or

(Diallage)

brown or

lic, pearly

Brittle

tabular; cleavage nearly

gray

rectangular. G.=3«4

103

Amphibole

White gray,

Vitreous,

H.=4-75

Monoclinic; crystals long,

(Tremolite)

greenish

silky

Brittle

slender and bladed, often

white

fibrous (asbestos); fre-

quently in crystals dis-

seminated through a mass

of dolomite; cleavage

oblique, 124°. G.=3

104

Amphibole

Green

Vitreous,

H.=4-75

Monoclinic; crystals long

(Actinolite)

silky

Brittle

and slender, sometimes

fibrous (asbestos); usually

in fibrous crystals dissemi-

nated through a mass of

talc or serpentine. G.=3

105

Analcite

White to

Vitreous

H. =4.5105.5

Isometric; trapezohedrons,

pale red

Brittle

rarely massive. G. = 2.3

to 2.4. Transparent to

opaque

127

LUSTER; STREAK WHITE OR LIGHT GRAY.

No.

Composition.

Action

of Acids.

Effects of Heating.

100

FeC03

ZnCOs

Hydrous,
zinc silicate

When powdered acted upon
with effervescence by hot
HC1; after dilution addi-
tion of K4FeCy6 gives blue
precipitate

Acted upon by HC1, effer-
vesces

Gelatinizes perfectly in HC1

Blackens and becomes mag-
netic in reducing flame

Coating of zinc oxide with
soda on charcoal

Yields water in closed tube

102

Calcium,

Fusible with intumescence

magnesium,

iron, silicate

103

Magnesium,

Fusible with intumescence

calcium,

silicate

104

Calcium,

Fusible with intumescence

magnesium,

and iron

silicate

105

Hydrous,

Water in closed tube; fuses

silicate of

easily to colorless glass

sodium and

aluminum

-128

Q— MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Luster.

Hardness and
Tenacity.

Remarks.

III.— HARD.

106

Apatite

Usually

Vitreous to

H. = 5

Hexagonal; crystals are

green,

somewhat

Brittle

hexagonal prisms with

sometimes

resinous

pyramidal terminations,

brown,

having a more resinous

etc.

luster than beryl ; often

massive. G.=3.2

107

Willemite

White to

Vitreous

H.=5-5

Usually massive ; also in

gray, yel-

Brittle

hexagonal crystals.

low, green,

G.=3.g to 4.2

brown

108

Enstatite

Gray, yel-

Vitreous to

H.=5.5

Orthorhombic; occurs mas-

low, green

pearly

Brittle

sive, fibrous, and lamel-

to brown

lar; translucent to opaque.

G. = 3.i to 3.3

109

Bronzite

Gray, yel-

Vitreous to

H. = 5.5

Enstatite contains little or

low, green

pearly

Brittle

no iron, bronzite contains

to brown

over 5 per cent of iron

no Monazite

Red to dark

Adaman-

H. =5 to 5.5

Monoclinic; generallyfound

brown,

tine or

Brittle

as rounded grains of sand,

reddish

resinous

sometimes known as tho-

or yellow-

rium sand; translucent

ish brown

Hypersthene

Darkish

Vitreous,

H.=5to 6

Orthorhombic ; massive,

green to

resinous,

Brittle

tubular and lamellar.

brown and

pearly,

G.=3.4 to 3.5

black

almost

metallic

112

Amphibole

Black

Vitreous

H.=5-75

Monoclinic ; crystals long

(Horn-

Tough

and slender; cleavage ob-

blende)

lique, 124°; granular; mas-

sive specimens have com-

mon luster and often con-

sist of a mass of interlaced

bladed crystals. G.=3-3

I29

LUSTER; STREAK WHITE OR LIGHT GRAY.

NO.

Composition.

Action

Acids.

Effects of Heating.

106 Calcium

phosphate

Zinc silicate

Magnesium,
iron silicate

Phosphate of
cerium,
lanthanum,
and didym-
ium

Iron and
magnesium
silicate, alu-
minum
sometimes
present

Magnesium,
aluminum,
calcium,
iron silicate

Soluble in hot HC1 or
HNO3. Solution treated
with H2SO4 gives precipi-
tate of calcium sulphate.
The nitric acid solution
added to excess of ammo
nium molybdate produces
immediately, or by gentle
warming, a bright yellow
precipitate, which shows
the presence of phosphor-
ic acid

Soluble with difficulty in
HC1

Anhydrous. Fuses with
difficulty ; coating of zinc
oxide with soda on char-
coal, yellow while hot,
white on cooling

Fusible with difficulty

B. B. infusible

B. B. on charcoal fusible
with difficulty to a black
magnetic mass

Fusible with intumescence

130

C.— MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

Species.

Color.

Luster.

Hardness and
Tenacity.

Remarks.

III.— HARD.

113

Pyroxene

White or

Vitreous

H. = 5.75

Monoclinic ; crystals short

(Malacolite)

gray

Brittle

and stout; cleavage near-

ly rectangular ; granular

varieties are called cocco-

lite ; massive specimens

often composed of crystals

with ends projecting on

surface. G. =3.4

114

Leucite

White to

Vitreous to

H. =5.5106

Isometric; trapezohedrons,

gray

resinous

Brittle

sometimes massive, trans-

lucent to opaque

Nephelite

White to

Vitreous to

H. = 5.5106

Hexagonal; transparent to.

gray or

greasy

Brittle

opaque

yellow

Ii6

Pyroxene

Grayish

Vitreous

H.=6

Monoclinic; crystals short

(Augite)

black,

Tough,

and stout; cleavage nearly

greenish

brittle

rectangular; granular va-

black

rieties are called coccolite;

massive specimens are

often composed of crystals

with their ends projecting

on the surface. G.=3.4

*I7

Orthoclase

Reddish,

Vitreous,

H.=6

Monoclinic ; two cleavage

gray,

pearly on

Brittle

planes at right angles ;

white, yel-

cleavage

cleavage eminent, seen

low, rarely

surface

when broken with a ham-

green

mer ; breaks into pieces

resembling rhombohe-

drons. G. =2.6

118

Albite

White

Vitreous,

H.=6

Triclinic; usually a mass of

pearly on

Brittle

interlacing bladed crys-

cleavage

tals. G.:=2.62

surface

119

Turquois

Bluish

Somewhat

H.=6

Massive, reniform, without

green

waxy

Brittle

cleavage. G.=2.y

120

Opal

White, yel-

Resinous

H. = 5-5 to

Amorphous ; generally in

lowish, or

6.5

rounded masses with a

brownish,

Brittle

compact, conchoidal frac-

common

ture; opalescent, present-

ing internal reflections

LUSTER; STREAK WHITE OR LIGHT GRAY.

No.

Composition.

Action of Acids.

Effects of Heating-.

114

116

Magnesium,
calcium sil-
icate

118

119

120

Silicate of
aluminum
and potas-
sium

Magnesium,
calcium,
iron, alu-
minum sili-
cate

Potassium,
aluminum
silicate

Sodium, alu-
minum sili-
cate

Hydrous,
aluminum
silicate

SiO2

Decomposed by HC1 with-
out gelatinization

Gelatinizes with acids

No action

No action with acids

Soluble in HC1

No action with acids

Fusible with difficulty, in-
tumescence

B. B. infusible

B. B. fuses quietly to a
colorless glass

Fusible with intumescence.
Anhydrous

Fuses with difficulty

Fusible with difficulty, col-
oring flame yellow

Infusible; becomes brown.
Gives off water

Gives off water; fuses with
effervescence when heated
with soda on charcoal

132

C.— MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Luster.

Hardness and
Tenacity.

Remarks.

III.-HAKD.

Microline

122

Rutile

White to
light
cream yel-
low, also
red, green

Vitreous,
sometimes
pearly

H.=6to6.5
Brittle

Red to
brown

Adaman-
tine

H.=6to6.5
Brittle

Same in composition as
orthoclase, but triclinic;
translucent to transparent

Tetragonal, often prismatic
and striated; translucent
to opaque. G.=4.2

IV.— VERY HARD.

123

Olivine

Green, yel-

Vitreous

H.-6.75

Occurs usually in grains,

(Chrysolite)

low

Brittle

or granular disseminated

through basalt in small

glassy crystals; transpar-

ent to translucent.

124

Quartz

White,

Vitreous

H.=7

Hexagonal, rhombohedral

(Vitreous)

gray, light

Brittle

division; crystals trans-

pink, and

parent, in hexagonal

amethyst

prisms with pyramidal

blue are

terminations; no cleavage

common

apparent; occurs also

massive, either compact

or granular

125

Quartz

Brown,

Somewhat

H.=7

Cryptocrystalline; translu-

(Chalce-

yellow,

waxy

Tough

cent; mamillary, nodular,

donic)

white, and

or in layers lining cavities;

red are

compact, breaking with

common

conchoidal fracture

126

Quartz

Red, brown,

Common

H.=7

Cryptocrystalline; opaque;

(Jaspery)

green, and

dull

Tough

usually in compact masses,

yellow are

sometimes banded

common

127

Garnet

Yellow,

Vitreous to

H.=7

In separate disseminated

brown,

resinous

Brittle

crystals (dodecahedrons

red, and

or trapezohedrons) or in

black are

granular masses; trans-

common

parent to opaque. G.>3

and <5. Pyrope is in

small granules

133
LUSTER; STREAK WHITE OR LIGHT GRAY.

No.

Con

aposition.

Action of

Acids.

Effects of

Heating.

121! Potassium,
aluminum
silicate

122

TiOs

No action with acids

Not acted upon

Fuses with difficulty

Infusible alone

123

124

125

126

127

Magnesium,
iron silicate

SiO2

SiO5

SiO2

Calcium,
magnesium,
iron,

aluminum
silicate

No action with acids

Infusible (whitens).

Fuses with effervescence
with soda on platinum
wire or on charcoal

Dark varieties are fusible,
usually leaving a mag-
netic globule; others in-
fusible

134

C— MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Luster.

Hardness and
Tenacity.

Remarks.

IV.— VERY HARD.

128

Tourmaline

In all

Resinous to

H.=7

Usually in separate crys-

colors.

vitreous

Brittle

tals disseminated through

black most

quartz, etc.; number of

common

sides of crystals some

multiple of three; termin-

ations low three-sided pyr-

amids ; aggregations of

crystals often coarse col-

umnar; faces of crystals

deeply striated. G.=3 to

3-2

129

Andalusite

White to

Vitreous to

H.=6 107.5

Orthorhombic, often in

gray, red,

dull,

Brittle

square prisms transparent

yellow,

earthy

to opaque. G. = 3.i to 3.2

green,

brown

130

Beryl

Green to

Vitreous;

H.=7-5

Sometimes massive; usu-

yellowish

yellow

Brittle

ally in separate crystals

and bluish

varieties

(hexagonal), terminated

green,

sometimes

by plane bases; faces

white to

resinous

often striated; usually

light yel-

shows cleavage parallel

low, some-

to base when broken. G.

times blue

= 2.7

and red

I31

Spinel

Black, red,

Vitreous

H.=7-7 to 8

Isometric; usually in octa-

gray,

Brittle

hedrons and rounded

yellow,

grains, transparent to

green,

opaque. G. =3. 5 to 4. 1

blue

132

Topaz

Pale yel-

Vitreous to

H.=8

In right rhombic prsims

low, white,

adaman-

Brittle

usually differently modi-i

blue, red,

tine

fied at the two extrem-

and green

ities. G.=3-4 to 3.66

133

Chrysoberyl

Various

Vitreous

H.=8.5

Orthorhombic; transparent

shades of

Brittle

to translucent. G.=3-5 to

green to

3-85

yellow

• .

134

Corundum

Blue, red,

Adaman-

H.=9

(Sapphire,

white,

tine to

Brittle to

Rough hexagonal crystals,

ruby)

gray, yel-

vitreous

tough

massive to fine granular,

low, green,

transparent to opaque.

and brown

G. — 3.9 to 4.1

135

LUSTER; STREAK WHITE OR LIGHT GRAY.

No.

Composition.

Action of Acids.

Effects of Heating.

128

Complex
silicate

No action

Dark varieties are fusible
with difficulty; and after
fusion decomposed by
HaSO45 others infusible

I29
130

Silicate of
aluminum

No action

Infusible
Infusible

Beryllium,
aluminum
silicate

No action

131

Aluminate of
magnesium

No action

Infusible

132

Aluminum
silicate with
silicon
fluoride

No action

Infusible

133

Aluminate of
beryllium

No action

With borax fuses
great difficulty

with

^34

Al,03

No action

Infusible

136

C.— MINERALS WITHOUT METALLIC

EXTERNAL CHARACTERISTICS.

No.

Species.

Color.

Luster.

Hardness and
Tenacity.

Remarks.

IV.— VERY HARD.

135

Diamond

White or

Adaman-

H. = io

Isometric ; commonly in

colorless,

tine,

Brittle

octahedrons; usually

sometimes

greasy,

transparent, translucent

pale

brilliant

to opaque; conchoidal

shades of

fracture. G. =3.516 to

yellow,

3-525

red,

orange,

green,

blue,

brown, and

occasion-

ally black

. 137
LUSTER; STREAK WHITE OR LIGHT GRAY.

No.

Composition.

Action of

Acids.

Effects of

Heating.

135 Pure carbon No action

At temperature of electric
arc in air burns to CO2;
out of air changes to a
sort of coke

PART II.
THE COMMON ROCKS. -

The term rock is applied to the more extensive mineral
masses which make up the earth's crust. Some of these
constituent masses are composed of a single mineral, but
most rocks are mineral aggregates. Pure limestone or pure
siliceous sandstone are examples of rocks consisting of a
single mineral; the first is composed of calcium carbonate
and the second of silica. Nearly all rocks, however, are
mineral aggregates, being composed of two or more min-
erals ; even those composed essentially of a single mineral
usually contain small quantities of other minerals. The term
rock is ordinarily held to imply a solid, hard mass, but in
geological usage it is not so restricted, but is equally ap-
plicable to soft clay, loose sand, and hard granite.

Although there have been distinguished and more or less
fully described about nine hundred distinct mineral species,
a small number of these make up the great mass of the
earth's crust : only about twenty species are of prime im-
portance as rock constituents ; these are the essential constit-
uents of the rocks ; all other species are accessory or acci-
dental minerals.

CONSTITUENTS OF ROCKS.

The principal rock-making minerals may be included
under two general heads, siliceous and calcareous minerals.
The first includes silica and the silicates ; the second the car-
bonates, sulphates, and phosphates of calcium.

The principal rock-making minerals are :

SILICA, quartz, the most abundant mineral of the earth's
•crust.

139

140

THE COMMON ROCKS.

THE
SILICATES.

CALCA-
REOUS
MINERALS.

rp, f Monoclinic, — Orthoclase.
Feld \ Triclinic— ( Albite, Oligoclase, Ande-
spart KSSS2, °rthlte' Labr"

Feldspath- ( Nepheline.
old < Leucite. •
group. ( Analcite.
The Micas, — Biotite, Muscovite, and Hydrous

Mica. r .

Amphibole group.
Pyroxene group.
Talc.

Serpentine.
Chlorite.

f Calcite and Aragonite.
I Dolomite.
1 Gypsum.
[Apatite.

In addition to these most abundant rock-making species,
the metallic ores, coal, peat, salt, and a few other minerals
form limited, but, from an economical point of view, most
important rock deposits. The metallic ores and coal have
been already described as minerals.

THE CLASSIFICATION -OF ROCKS.

The classification of rocks can be based upon their phys-
ical condition and texture, as crystalline and uncrystalline ;
upon their mineral characters, as calcareous aud siliceous ; upon
their mode of origin, as igneous and sedimentary; upon their
structure and texture, as stratified and unstratified ; upon
whether transformed from original condition, as metamorphic
or not.

A classification from any single point of view is unsatis-
factory, because it fails to display important relationships
among rocks and fails to give much desirable information.
in regard to the characters and properties of rocks.

For the purposes of the general student the most useful
and instructive arrangement must involve to a certain
degree all of the above distinctions. While, therefore, none

SEDIMENTARY ROCKS. 141

of these distinctions are ignored, the fundamental divisions
here observed are geological and depend upon structure,
mode of origin, and transformation.

GENERAL CLASSES.

The three most general classes under this arrangement
are :

I. Sedimentary or stratified rocks.
II. Igneous or unstratified rocks.
III. Metamorphic rocks.

The sedimentary rocks appear far more extensively at
the surface of the earth, and as a rule their constituents
have simpler composition than those of the other classes;
they will be first described.

I. SEDIMENTARY ROCKS.

The sedimentary rocks have resulted from the deposition
of sediments or comminuted material, the material being
primarily derived from the decomposition and disintegra-
tion of pre-existing rocks. The rocks are therefore deriv-
ative or secondary. The sedimentary rocks have been
generally deposited from water, and one of their most
obvious and common characteristics is stratification. So
common is this origin and structure that the terms aqueous,
stratified, and sedimentary are frequently used synony-
mously.

All the sedimentary rocks, however, have not been laid
down under water; very limited masses have been accumu-
lated on land : this fact gives rise to two divisions of the
sedimentary rocks :

A. Aqueous ; those laid down under water.

B. Terrestrially deposited; those accumulated on land.
It is true only in a very general sense that some of the

aqueous rocks can be termed stratified, and the same is true
to a greater extent as regards the terrestrial. It is evident,
therefore, that the terms aqueous, sedimentary, and stratified
are not strictly synonymous.

142 THE COMMON ROCK'S.

A. AQUEOUS ROCKS.

The aqueous rocks may be further subdivided into :

(a) Fragmental or mechanically deposited.

(b) Chemically deposited.

(a) Fragmental Rocks.

The fragmental rocks are uncrystalline and are usually
either arenaceous or argillaceous, and are mechanically
deposited.

I. Arenaceous.

The arenaceous, mechanically deposited rocks are com-
posed of angular or worn fragments resulting from the dis-
integration and wear of older rocks. The principal com-
ponent of the arenaceous rocks is silica, though small
quantities of the more common silicates are often present, as
feldspar, mica, etc. To the arenaceous group the following
varieties belong :

SAND. — Sand is comminuted rock material in an in-
coherent state ; common sand is mainly quartz-grains, though
some sands contain fragments of other minerals, as feldspar,
mica, garnet, and iron oxide. Calcareous matter is also
sometimes present. The roundness of the grains of sand
depends upon the attrition to which they have been sub-
jected ; river and land sands are accordingly less likely
to be round than those of sea-beaches.

GRAVEL.— Gravel is composed of water-worn pebbles
which range in size from a pea to a hen's egg. Various
rock material may be present in the gravel, but, owing to
its permanence, quartz is most common. A gravel beach
usually has some sand mixed with the pebbles. The larger
pebbles and cobblestones with or without gravel are usually
called shingle.

SANDSTONE. — Sandstone is a consolidated rock made
from sand. The cementing material may be calcium car-

SEDIMENTARY ROCKS. 14$

bonate, clay, ferric oxide, or silica. The two cements last,
named give the more durable stone.

Varieties of sandstone are extensively used as a building-
stone. It is quite durable and is easily quarried and cut.
The " brownstone " used much in New York city and else-
where for building is quarried in Connecticut and New
Jersey. Sandstones when used for a building or wall should
be placed with the bedding horizontal, since that is the
position in which the stone will stand the greatest pressure
and absorb the least moisture from the foundation. When
pyrite is present in a building-stone it is likely to cause dis-
integration. Sandstone is usually more or less laminated,
especially if it contains clay.

When sandstone splits readily into even plates or slabs,,
it is called flagstone or paving-stone. Even-grained, friable-
sandstones of various degrees of fineness are used as grind-
stones or scythe-stones.

NOVACULITE. — This is an exceedingly fine-grained sand-
stone, often called oilstone. It is found extensively in
Arkansas and is valuable for whetstones. Sandstones often
contain a considerable amount of clay, to indicate which
they may, very properly, be termed argillaceous sandstones.

QUARTZ CONGLOMERATE. — A siliceous rock made up of
sand, pebbles, or angular fragments of rocks cemented
together. If the pebbles are rounded the conglomerate is a
pudding-stone ; if angular, a breccia. The term " conglomerate "
is often appled to the pudding-stone alone.

GRIT. — A grit is a hard, siliceous conglomerate, the
grains being less rounded than in common sandstone. It is
composed of vitreous quartz and was formerly sometimes
used for millstones.

2. Argillaceous.

CLAY. — Soft, very fine grained, almost impalpable, more
or less plastic material, chiefly kaolinite in composition, and
of various colors, as white, gray, yellow, red, brown, or
black. When wet it can be kneaded between the fingers;

144 THE COMMON ROCKS.

when dry it is soft and friable and adheres to the tongue.
It often contains much quartz-sand, and pulverized feldspar.
Marl is a clay containing carbonate of lime, and the amount
of carbonate may be so large as to place the rock among
the chemically deposited.

SHALE. — Shale is a soft, fragile, argillaceous rock, having
an uneven, slaty structure, splitting along planes parallel to
the planes of deposit. Gray, brown, black, red, and other
shades ; consists essentially of clay with some fine sand or
pulverized feldspar. It is fine mud consolidated. Shales,
by the addition of sand, graduate into fissile sandstones ; by
the addition of calcareous matter into limestones ; by the
addition of carbonaceous matter into coaly shales.

FIRE-CLAY. — A clay nearly free from alkalies and iron
and capable of standing a great heat without fusing. It is
usually of a light color and is found abundantly beneath the
coal beds.

(b) Chemically Deposited Rocks.

OOLITE. — Is a limestone composed of minute spherical
grains resembling the roe of a fish, each grain being com-
posed of concentrically deposited layers of calcite. PISO-
LITE is a similar rock in which the grains are as large as
peas. The unconsolidated oolitic grains are found as beach
sand at Pyramid Lake, Nev.; similar but finer sand is now
forming at Great Salt Lake. An oolitic rock is also found
composed of calcareous, rolled sand cemented by calcium
carbonate. This last is a fragmental rock. Extensive
deposits of oolitic rock are known to exist.

f GYPSUM. — Is composed of calcium sulphate, and is a
chemically deposited rock formed by the evaporation of the
water holding it in solution. The decomposition is hastened
by the presence of an abundance of common salt in the solu-
tion.

SALT. — Common salt, like gypsum, is deposited by
evaporation from waters holding it in solution. Salt and
gypsum are generally associated, the latter being deposited

SEDIMENTARY ROCKS. 145

first. Salt occurs as an ingredient of other deposits, as salt
shales ; also in thin sheets and enormously thick beds.

TRAVERTINE. — A massive limestone, formed by deposi-
tion from calcareous springs or streams. It is usually cel-
lular and more or less concretionary. A handsome com-
pact, banded kind, translucent and of great beauty, comes
from Mexico, and is sometimes called Mexican onyx.

STALACTITE AND STALAGMITE.— These are deposits,
usually more or less columnar, formed on the roofs and floors
of caves by deposition from solution.

SILICEOUS SINTER. — Is composed of opal silica. Occurs
in compact, porous, and concretionary forms. It is deposited
from hot siliceous waters, and is thus frequently found
around geysers, forming mounds and occasionally terraces.
From this fact it is sometimes called GEYSERITE. The .de-
posit is mainly due to the evaporation of the water, but in
some cases to the action of algae.

CHERT, FLINT. — A dark, compact rock occurring in
nodules and in beds and composed almost entirely of chal-
cedonic quartz. Its mode of origin is not thoroughly under-
stood. Under the microscope the siliceous spicules of
sponges and siliceous shells of diatoms, also calcareous shells
or spines converted into silica, have been observed in it.
The first two facts would indicate that the rock is, in part
at least, formed from the segregated remains of organisms,
while the last indicates a substitution of silica by a chemical
process. The mass of the rock is believed to come more
properly under Chemical Deposits, though in some cases it
might be placed among those .organically formed. The
nodules occur abundantly in chalk formations.

BUHRSTONE. — Is a highly siliceous, compact, though cel-
lular rock. It is principally found in the Tertiary rocks of
the Paris basin, and occurs in beds associated with sand and
argillaceous marl deposits. The rock often abounds in land
and fresh-water shells as well as in the stems and seeds of
land and aquatic plants, all converted into silica. The exact
mode of deposition is not known, but it was probably the
action of siliceous waters on a previously existing fossilifer-

146 THE COMMON ROCKS.

ous rock, the silica replacing other material. The rock is
chalcedonic quartz and is largely used for millstones in
flouring-mills, cement-factories, potteries, chemical works,
and other similar establishments. It has also been found in
the Tertiary of South Carolina.

MARL. — Marl is a clay containing a greater or less pro-
portion of CaCO3 , from a small per cent to over one-half.
Though testacea are usually abundant in marl beds, the
CaCO3 has more generally been deposited from waters
holding it in solution ; to this extent marl is a chemically
deposited rock. When the clay is taken into consideration
marl might be classed, as already stated, as an argillaceous
sedimentary rock. The marls are used as fertilizers.

The rocks of organic origin are those mainly composed:
of the remains of organisms. These remains have in many
cases been acted upon, and to a certain extent the rocks
formed by mechanical agencies, so that some of them might
properly be classed as mechanically deposited rocks, but
their essential origin rather than their accumulation is their
more distinctive characteristic.

LIMESTONE. — This is a general term which includes all
those rocks mainly composed of CaCO8, though they vary
greatly in degree of purity.

Most limestones are of organic origin and are marine
deposits, though, as already seen, some are chemically de-
posited by streams or springs. The organic limestones
show every gradation of structure and texture. The de-
posits range from thin laminae to beds several thousand feet
in thickness. In some the organic remains are shown in
almost perfect preservation, in others the organic origin is
only evident under the microscope, and in still others the
organic structure is no longer visible. From formations
now being made in coral regions it is known that rocks of
evident organic origin do not always show this origin in.

SEDIMENTARY ROCKS. 147

their texture ; oome of the more important and distinctive
organic limestones are the following :

SHELL-MARL. — This is a friable rock mainly composed of
shells and their fragments cemented together by calcium
carbonate. Clay and sand are usually present. Such de-
posits are generally formed in lakes and ponds. When com-
pacted into solid stone they constitute fresh-water lime-
stones.

COQUINA. — Shell-limestone. Coquina is a marine, porous
shell-limestone made up almost entirely of fragments of
shells, though occasional shells are entire. When first re-
moved from the ground the rock is soft and may be easily
cut; by exposure to the air it is greatly hardened. This
rock is found in Florida and is extensively used in the forts
and structures of St. Augustine. In the Florida rock the
spaces between the shells are often partially filled with clear
quartz sand. The stone is now being formed at numerous
points along the Florida coast. Shell-limestones are formed
at other places, but they differ from coquina in that they
are more compacted ; such a rock is found along the Genesee
river, near Rochester, N. Y.

CHALK. — Is a white earthy, friable limestone, composed
mainly of the shells and shell-remains of rhizopods.

HYDRAULIC LIMESTONE. — This is an impure limestone
containing clay and which, when calcined, yields a lime
which furnishes hydraulic cement ; that is, a cement which
sets under water. The indications of hydraulic properties
in a limestone are compact texture, argillaceous odor, con
choidal fracture, and sluggish effervescence.

DOLOMITE. — Is not distinguished by the eye alone from
calcite limestone. It is calcium-magnesium limestone and
occurs in beds often associated with gypsum and rock salt,
also in irregular bands traversing limestone. The origin of
dolomite is not fully understood. In some cases it seems to
have been deposited as calcium carbonate and subsequently
a portion of the calcium carbonate was replaced by magne-
sium carbonate, by the chemical action of the magnesium
salts in sea- water.

148 THE COMMON ROCKS.

In other instances this action seems highly improbable,
and the rock was more likely formed as suggested by Hunt,
being deposited in closed oceanic basins whose waters were
rich in magnesium carbonate. Dolomite contains less than
fifty per cent of magnesium carbonate, the remainder being
calcium carbonate. Sing Sing marble, a typical dolomite,
gives an hydraulic lime by cautious reduction, reducing
the MgCO3 with perhaps some of the CaCO,. Reduction at
high temperature gives a fat lime.

CALCAREOUS CONGLOMERATE. — A rock composed of
fragments of calcite or dolomite cemented by calcium car-
bonate. If the pebbles are rounded the conglomerate is a
pudding-stone ; if angular, a breccia. The term " conglomerate"
is often applied to the pudding-stone alone.

Other massive limestones are often named from the char-
acter of the predominating organic remains — such are coral
rock, which consists of fragments of coral and other marine
remains cemented by CaCO3 ; crinoidal limestone is composed
largely of the disks and stems of crinoids cemented together ;
mummulitic limestone is a cream-colored rock consisting of
nummulites, little flattened, disk-shaped fossils, cemented by
calcite. Some of the pyramids of Egypt, including that of
Cheops, are made of this rock.

GREENSAND. — An olive-green sand-rock, friable, con-
sisting mainly of grains of glauconite (hydrous silicate of
aluminum, iron, and potassium) with more or less sand.
Many of the glauconite grains, under the microscope, are
seen to be the casts of foraminiferous shells, and the proba-
bilities seem to be that the glauconite was originally de-
posited in organisms.

SILICEOUS LIMESTONE. — A limestone containing sili-
ceous sand. It has a gritty feel under the fingers and may
be distinguished by dissolving the pulverized rock in hy-
drochloric acid, when the sand will be left as a gritty
powder which is capable of scratching glass.

MARBLE. — Any limestone which occurs in large masses
and is capable of receiving a polish is included under the
-general term marble ; a more restricted use confines it to

SEDIMENTARY ROCKS. 149

the metamorphic, crystalline limestones. If the marble has
colors distributed in blotches or streaks it is called varie-
gated ; if it contains angular fragments it is called brecciated
marble. Many of the calcareous rocks referred to give
marbles.

TRIPOLITE. — An infusorial earth, consisting chiefly of
siliceous shells of diatoms with the spicules of sponges, and
is silica in the opal state. It resembles clay or impure
chalk in appearance, but is a little harsh between the
fingers and scratches glass when rubbed on it. It forms
thick deposits, and is often found in old swamps beneath
the peat. It derives its name from Tripoli in Africa, where
it was first obtained.

CARBONACEOUS DEPOSITS. — Peat and the various forms
of coal come under this head, all being of vegetable origin.
Peat is a mass of partially disintegrated and decomposed
vegetable matter. It has a black or brown color and is
much richer in carbon than unchanged vegetable matter.
In recent peat, or that in which the carbonization has not
greatly progressed, the vegetable structure is readily de-
tected by the unaided eye, but in the more perfect forms it
can only be seen by the microscope. It occurs in many
places and is valuable as a fuel. The various forms of coal
have been already referred to as minerals.

B. TERRESTRIAL OR LAND-FORMED ROCKS.*

This division includes the rocks accumulated on land
or areas not habitually covered by water. ,Such rocks are
principally produced and accumulated by meteoric agen-
cies. The most important of this class is the soil.

SOIL. — This is a general term for the products which
result from the subaerial decomposition and disintegration
of the more compacted rocks of the earth's surface. It is

* There is no general agreement in the classification of the rocks here
included under the term terrestrial. Nearly the same formations have
been included under the terms aerial, subaerial, and ceolian, but none of.'
these is thought to be as appropriately applicable as that adopted.

15° THE COMMON ROCKS.

an intimate mixture of such material and generally contains
some animal and vegetable matter. The mineral matter of
the soil often results from the rocks immediately below it,
but it may be more or less transported. All fertile soils
contain organic matter.

ALLUVIUM. — Is a term applied to the soil brought to
gether by the ordinary operations of water, especially
during times of flood. It generally constitutes the flats on
either side of streams and is usually in layers varying in
fineness, due to successive depositions.

BLOWN SANDS. — Loose sands, of whatever origin, may
be blown into mounds or heaps, forming dunes or downs,
and if they be calcareous sands or contain considerable cal-
careous matter, they may by the action of rain-waters be
converted into compact stone.

LOESS. — Is a term applied to certain widely distributed
deposits which have the same general characteristics, but
probably all have not been deposited in the same way.
The material under consideration is a light-colored loamy
earth, generally unstratified. It covers immense areas in
northern China, in the pampas of South America, and
occurs as extensive bluff-deposits along the Mississippi and
its tributaries, along the Rhine, Danube, and other Euro-
pean rivers. Somewhat similar deposits occur in the basin
regions of our western country. The origin of these for-
mations is not yet solved. In some regions they have been
ascribed to the action of the wind, which is known to have
deposited immense quantities of dust after carrying it
through great distances. In certain arid regions dust-
storms have been known to fill the atmosphere with dust
for days, even obscuring the sun. Wind-blown dust is
probably one of the sources of loess deposit ; another is
thought to be rain-washed sediment from bare slopes. The
loess of river-valleys generally was probably laid down in
water during the periods of flooded lakes and rivers.

GUANO. — This substance is a mixture of organic matter^
ammonium salts and phosphate, of lime. It is a brown, light,
porous body with an ammoniacal odor. The deposits of

SEDIMENTARY ROCKS. !$!

guano occur in rainless regions and are the droppings of the
immense flocks of sea-fowl that have for centuries frequented
the regions. South America and the rainless islands off the
western coast of that continent contain the most noted de-
posits. If the underlying rock is calcium carbonate it may
be gradually converted into calcium phosphate. Similar
•deposits made by bats have been found in many caves.

VOLCANIC TUFA is a rock formed from the comminuted
fragmentary material ejected from volcanoes. These mate-
rials are consolidated partly by pressure and partly by infil-
trating waters. Vast quantities of fine matter are often
ejected from volcanoes, the finest being termed ashes. There
is a gradation from this through sand into the coarser vari-
eties of ejected matter. The term " ash " is used because of
its resemblance to the ash from wood or coal, but no result
of combustion is implied. The tufas, or " tuffs " as the word
is sometimes written, include the rocks formed from the
consolidated ashes, sand, and finer material.

The ejected material may fall into bodies of water, thus
giving aqueous as well as terrestrial tufas. The finer ejected
material, especially that of a sandy nature, is sometimes
called peperino. The erupted matter from volcanoes and
fissures forms other extensive land deposits, but thev cannot
be included under the head of sedimentary rocks.

TALUS. — This is a term applied to the piles of earth and
bowlders generally seen at the base of cliffs and mountain-
slopes. Talus results from the unceasing action of gravity
and meteoric agencies in dragging down the higher eleva-
tions. In the case of cliffs, if the debris is not removed from
the base, the precipice will in time be converted into a
slope.

DETRITUS. — Detritus is the general term for earth, sand,
alluvium,* silt, gravel, and mud. The material is derived to

* The alluvial material is constantly carried into lakes, bays, etc., at
the mouths of the rivers and streams. It is not under such circumstances a
terrestrial deposit. In bays and harbors these shore deposits are usually
called silt. They tend to delta formation and may eventually give rich
alluvial lands.

I $2 THE CO MAI ON ROCKS.

a great extent from the wear of rocks through disintegrating
agencies, attrition and decomposition.

DRIFT. — Drift is the unstratified sand, gravel; and stones,
with more or less clay, deposited by glaciers ; it is also called
TILL.

II. IGNEOUS OR UNSTRATIFIED ROCKS.

The first of these terms is applied to this class of rocks
because heat has evidently been concerned in their origin,
and the second because of the entire absence of true strati-
fication. These rocks are believed to have consolidated from
a fused or semi-fused condition. The term eruptive is some-
times used as synonymous with the above terms, but eruptive
is also used as the equivalent of volcanic, and will be so
understood in this text.

EVIDENCE OF ORIGIN. — The igneous origin of these rocks
is primarily involved in the accepted theory of the earth's
origin, and they are believed to have been the rocks first
formed and to have resulted from the cooling and solidifica-
tion of the molten globe ; they are therefore the primitive
rocks from which all others have been derived and must of
necessity, at greater depths, underlie all superficial rocks.
Subsequently and up to the present time all exposed igneous
rocks have been produced from within the earth's crust, and
there is the strongest ground for thinking that all have been
in a molten or a pasty condition. The effects which the
igneous rocks have frequently produced upon the sedimen-
tary deposits with which they have come in contact, and the
extreme similarity of these rocks, in many cases, to modern
lavas, leave little doubt that heat has been an agent in their
production.

CHARACTERISTICS OF IGNEOUS ROCKS. — The igneous
rocks in general differ from the sedimentary by the absence of
all lamination, due to the sorting of material ; by the texture,
which is more or less crystalline, glassy, or compact ; by the
absence of fossils, and by the marked difference in the,
manner of occurrence.

IGNEOUS OR UNSTRATIFIED ROCKS. 153;

Besides the general terms of coarse and fine texture,
descriptive of rocks, the igneous rocks display four distinct
types of texture with gradations from one to the other.
These types are designated as follows :

ist. Glassy, in which the rock is a glass mixture, not
showing distinct minerals ; is devoid of crystalline masses and
has that texture which is best described by the term itself
and thus universally recognized. The incipient stages of
crystallization are often shown under the microscope in
native glasses, by hair-like formations (trichites) and minute
grains (spherulites). When the fused glass material is sub-
jected to the action of escaping gases, there may be pro-
duced a fine cellular or vesicular mass, thus giving rise to.
pumiceous or scoriaceous texture.

2d. Compact, in which the mass is made up of minute
crystals too small to be seen by the eye alone. When the
microscope reveals the crystals the rock is macrocrystalline,
and when they cannot thus be seen, cryptocrystalline. Compact
rocks are homogeneous and stony, not glassy in appearance.

3d. Porphyritic, in which distinct crystals are inter-
spersed throughout a ground mass which is glassy, minutely
crystalline, or both. The large crystals are called pheno-
crysts. This texture is thought to indicate two periods of
crystallization, the phenocrysts forming first and the magma
solidifying later. In some cases, if not all, the phenocrysts
were formed before the rock was erupted and hence are
said to be intratelluric.

4th. Granitoid, in which the texture is wholly crystalline
without any amorphous ground-mass.

CLASSIFICATION OF IGNEOUS ROCKS.

The igneous rocks for the purposes of the general
student can be best and most significantly divided into two
primary groups, plutonic and volcanic, with a less distinctly
defined group forming an intermediate series. The typical
members of the first two groups are distinctly different,
but other members of the group approach each other
by insensible gradations until they might with equal

154 THE COMMON ROCKS.

propriety be assigned to either ; these form the intermediate
series and are sometimes classed as intrusive rocks. These
divisions of the igneous rocks involve distinctions both in
mode of occurrence and in the texture of the kinds.

i. Plutonic Rocks.

The plutonic rocks occur in the greater masses and have
cooled and solidified at greater depths than the other groups
and consequently more slowly. They have never been
erupted on the surface. This slow cooling has led to a more
perfect and wholly crystalline texture. They have the
granitoid texture; that is, the rocks are made up of an
aggregate of crystals more or less perfect without any un-
crystallized ground-mass between the crystals. They are
coarsely crystalline (macrocrystalline) and granular. The
constitutent minerals are mainly quartz, the feldspars, mica,
and hornblende. The principal rocks of this group are :

GRANITE. — Common granite consists of quartz, feldspar,
and mica. Massive, with no appearance of layers in the
arrangement of the mineral ingredients. G. = 2.5 to 2.8.
The quartz usually transparent, bluish glassy, without
cleavage ; the feldspar (usually orthoclase) opaque white or
reddish with glistening cleavage surface ; the mica in glisten-
ing scales, either whitish or black. When all the crystals
are small and the rock evenly granular it is sometimes
called eurite or granulite. When the feldspar is in well-
defined crystals in a finer but still crystalline ground-mass,
it is called porphyritic granite. When the rock also contains
hornblende it is called syenitic granite. When the mica is
replaced by hornblende it is called hornblende granite.
Granite is generally plutonic, but sometimes metamorphic.

PEGMATITE (Graphic Granite] consists mainly of quartz
and feldspar with little or no mica or hornblende, the
quartz existing as bent plates in the feldspar, giving in
cross-section the appearance of Hebrew or Arabic charac-
ters.

SYENITE is a rock composed essentially of orthoclase

IGNEOUS OR UNSTRATIFIED ROCKS. 155

and hornblende. The hornblende may be replaced by
biotite or augite, giving mica or augite syenite.

The term syenite has been, in many places, used to
describe the rock above referred to as hornblende granite.
It still has a wide popular use in this sense in this country.

DIORITE. — A dark, speckled, greenish or grayish black
rock, generally consisting of a crystalline aggregate of
triclinic feldspar (oligoclase) and hornblende, though some
varieties contain pyroxene or biotite. Quartz frequently
present ; if in large quantity it makes quartz-diorite. Usu-
ally granitoid in texture, though much finer than granite.
Generally plutonic, sometimes metamorphic.

DIABASE. — A dark, greenish, crystalline rock, similar in
appearance to diorite, but containing augite in place of
hornblende. Usually fine-grained. Often contains olivine.

GABBRO. — A coarse-grained variety of diabase.

The above selections include the more typical rocks of
the plutonic group, but they graduate into each other and
give rise to many varieties.

Diorite and diabase are often intrusive, and accordingly
fall also in the intermediate series of trappean rocks.

2. Eruptive or Volcanic Rocks.

The volcanic rocks have been brought to or near the
surface by volcanic action and thus have been subjected to
more rapid cooling than the plutonics. This has generally
resulted in a wholly glassy or only a partially crystalline
texture ; when partially crystalline, the crystals are im-
bedded in an amorphous or glassy paste ; they are usually
micro- or cryptocrystalline, and have a minutely speckled
appearance. While generally the characters are as stated
above, some of the volcanics are holocrystalline, but even
then the principal mass of the rock is likely to be of very
minute crystals. The difference in texture between the
volcanic and plutonic rocks is due to their modes of oc-
currence, which involves difference in the conditions of
cooling.

OBSIDIAN. — Lava which has been completely fused and

156 THE COMMON ROCKS.

cooled rapidly. A volcanic glass. Gray to black. Breaks
with a conchoidal fracture, the splinters often transparent.
Most of the obsidians are essentially composed of ortho-
clase. Its dark color and opacity are due to vast numbers
of incipient crystals.

Pitchstone has much the appearance of obsidian, but
contains water.

PUMICE. — A finely vesicular, light-colored variety of
scoria. It is so light that it will float upon water. A
strikingly similar substance can be produced by injecting
steam into certain iron slags. Pumice may result from
different magmas, but the more common kind is composed
essentially of orthoclase. It is often capillary or in thread-
like masses, even silky.

RHYOLITE. — This is one of the most common kinds of
lava erupted when the original igneous material is granitic
in composition. The ground-mass is mainly orthoclase in
minute crystals with more or less glass. It has the por-
phyritic texture, the isolated crystals (phenocrysts) being
of quartz and sanidin. Rhyolites are exceedingly abundant
in the western United States. When coarsely granular it
is sometimes called nevadite. Liparite and quartz trachyte
are also names applied to forms of rhyolite.

TRACHYTE. — A light-colored, ash-gray rock. It consists
of a ground-mass which is mainly minute orthoclase crys-
tals, with little or no glass, with phenocrysts of sanidin of
glassy luster. Often contains amphibole, pyroxene, or bio-
tite, and is slightly porphyritic in texture. It graduates
into rholite.

PHONOLITE. — A compact, grayish-blue or brown feld-
spathic rock, somewhat slaty in structure. It clinks under
the hammer. It differs in composition from trachyte in
containing nepheline and sometimes leucite and horn-
blende. It is a rare rock in this country.

BASALT. — This term is applied to many varieties of the
volcanic rocks, which differ considerably in appearance.
As most commonly applied it is a dark, almost black,
cryptocrystalline rock, breaking with a dull, slightly con-

IGNEOUS OR UNSTRATIFIED ROCKS. 1 57

choidal fracture. It contains microscopic crystals of labra-
dorite, augite, and usually olivine, in a ground-mass of the
same. Magnetite is often an abundant constituent.

DOLERITE, has the same composition as basalt, except
the olivine, and is more coarsely crystalline. Its color is
dark grayish. It is commonly called trap-rock, a term
which is applied to several other granular volcanic rocks.

ANDESITE. — A dark-grayish rock, consisting essentially
of triclinic feldspar (oligoclase or andesite), with horn-
blende (or augite).

3. Intermediate, Intrusive Rocks.

In the plutonic and volcanic groups we have described
only the more typical varieties, but there are many other
igneous rocks which cannot with more distinctness be
assigned to one rather than to the other of these groups.
Many of these ill-defined rocks, in their mode of occurrence
as well as their texture, are intermediate between the plu-
tonic and the volcanic. The volcanic are generally the
superficial igneous rocks ; the plutonic are the profound
masses underlying the surface ; the intermediate series
form the connecting conduits and sheets between them.
Sometimes they are driven like wedges between the strata
which rest upon the plutonics and are overlaid by the
volcanics. The most common of the intermediate rocks are
intrusive forms of dolerite, diorite, and diabase. They
differ from the plutonic varieties only in their modes of
occurrence, which may also affect their texture. The
terms trap and greenstone are often applied to the basaltic
intrusive rocks.

FELSTTE is a light-colored intrusive rock, usually red-
dish or gray. It is compact, fine-grained, and composed
chiefly of feldspar and quartz without glass. It is often
porphyritic in texture, the phenocrysts being of quartz or
feldspar. The first is sometimes called quarts-porphyry, and
the second porphyrite. The term porphyry is applicable to
any rock which consists of a homogeneous base, with well-
defined crystals of the same material or another mineral.

158

THE COMMON ROCKS.

We thus often have greenstone porphyry as well as felsitic
porphyry. The term porphyry is very generally employed
by miners in our West for any rock that occurs in what
they call veins.

OTHER MODES OF CLASSIFICATION OF IGNEOUS ROCKS.

No single common system for the classification of
igneous rocks has been adopted. In addition to the divi-
sions based upon their mode of occurrence, above given,
other divisions, based upon chemical and mineralogical com-
position, are very generally recognized, and are more fun-
damental to the special student. This method of classifying
gives the following groups for the rocks described:

i(i) f Obsidian. ") The principal minerals

j Pitchstone. present are orthoclase
Granite-rhyo- J Pumice. and quartz, oligoclase

lite family. , Rhyolite. { in subordinate quan-
| Felsites. tity, with some horn-

(_ Granites. J blende and mica.

Principal minerals pres-
ent are orthoclase and
hornblende, some oli-
goclase, pyroxene, and
biotite. Quartz gener-
ally absent; orthoclase
predominating mineral'

-syenite belongs to this
nepheline and leucite

replacing orthoclase.

"] Plagioclase (soda-lime)
feldspar is the predomi-
nating mineral, with
hornblende in consider-
able quantity. Pyrox-
ene and biotite may
occur. Quartz in small
quantity.

Principal minerals pres-
ent, plagioclase feld-
spar (labradorite or
}• anorthite) and pyrox-

Iene. Magnetite and
olivine are often pres-
ent.

(2)

S y enite-tra-
chytefamily.

Trachyte.
Phonolite.
Syenite.

I n t e r media t e
group, contain-
ing between -
55 and 65 per
cent of silica.

(3)

Nephelit<
family,
largely

Diorite-Ande-
site family.

Andesite.
Diorite.

(4)

Basic group, con-
taining be-
tween 45 and •
55 per cent of
silica.

Basalt-Gab- ^
bro family.

Basalt.
Dolorite.
Diabase.
Gabbro.

Ultra-Basic, con-
taining gener-
ally less than
45 per cent of

silica.

(5)

Rocks composed almost entirely of pyroxene or horn-
blende and olivine.

Serpentine rocks.

METAMORPHIC ROCKS. 159

III. METAMORPHIC ROCKS.

The metamorphic rocks are those which have been
produced by the transformation without disintegration of
pre-existing rocks. This transformation generally involves
one or more and often all the following changes — greater
hardness, different and more crystalline texture, develop-
ment of different minerals.*

One of the most important characteristics of many of the
metamorphic rocks is a foliated structure. This term gener-
ally refers to that structure brought about by the presence
of minute scales, such as produce the fissile character of
schists, but the term is now often used in a more general
sense and is made to include cleavage.

Until quite recently it was thought that metamorphic
rocks were all originally sedimentary rocks, but it is now
known that the original rocks often belonged to the igneous
classes. Metamorphic rocks may be said to have had two
dates, one of formation and one of transformation.

The metamorphic rocks have great extent and thickness
at many places throughout the world. The more important
kinds are the gneisses, schists, clay slate, marbles, quartzite,
and serpentine. The gneisses, schists, and slates have the
foliated structure, the other kinds have not. The foliation
in slates is usually termed cleavage.

COMMON GNEISS. — This rock has the general appearance
and mineral composition of granite, but the ingredients are
arranged in layers. Gneiss grades insensibly on the one
hand into granite and on the other through the schists into
sandy clays or clayey sands. It is now thought that gneiss
has frequently resulted from the metamorphism of granite.

If hornblende is also present as a constituent in the rock
it becomes syenitic gneiss.

*The term metamorphic has recently been used to include rocks altered
by decomposition and disintegration. Such use greatly enlarges this class
of rocks, but also makes the use of the term very general and less definite.

l6o THE COMMON ROCKS.

THE SCHISTS. — More or less fissile rocks, made up largely
of scales or thin crystals of the minerals from which they
derive their names. The structure is called schistose, and
differs entirely from that of slates.

The structure is included under the general term of folia-
tion. It is now thought that schists may have been derived
either from igneous or sedimentary rocks.

The varieties of schists are :

Mica Schist. — This is a grayish fissile rock consisting of
mica, considerable quartz, and frequently some feldspar. It
often contains garnets. Some varieties are used for flag-
stones.

Hydromica Schist. — Composed chiefly of hydrous mica or
of this with some quartz. The surface nearly smooth, pearly
to faintly glistening in luster, grayish in color.

Chlorite Schist. — Grayish green, smooth but not greasy to
the feel. Consists of chlorite with usually some quartz and
feldspar. Often contains crystals of magnetite.

Talcose Schist. — Composed essentially of talc. Has the
appearance and feel of talc.

Hornblende Schist. — Schistose, dark-colored, rough to
the feel, composed of hornblende.

CLAY SLATE (ARGILLITE). — An argillaceous rock, split-
ting into thin even slabs, the planes of cleavage running
athwart the stratification planes. Many of the common
slates contain considerable quantities of mica and hydro-
mica in scales. They are generally derived from sediment-
ary argillaceous rocks, but it is believed that they may
result through the transformation of volcanic tufas.

THE MARBLES. — The marbles were originally common
limestone, but metamorphism has produced in them a crys-
talline-granular texture. They are either calcite, dolomite,
or calcite-dolomite. They often contain mica, tremolite,
talc, pyroxene or apatite. Some of the common marbles
are:

Statuary Marble. — Pure white and fine grained.

Architectural Marble is coarse or fine grained, white
and mottled of various colors.

METAMORPHIC ROCKS. l6l

Verd Antique, Ophiolite. — A marble containing serpentine.

QUARTZITE is a changed siliceous sandstone, usually
firm and hard. The grains and the cement holding them
together are both silica. It generally requires the micro-
scope to recognize the fragmental nature of the rock, but
sandstones and quartzites graduate into each other.

ITACOLUMITE is a schistose quartzite through which
are distributed scales of mica, chlorite, and talc. The rock
is often only slightly compacted and almost friable. It is
sometimes the matrix in which diamonds are found in Brazil.
It is slightly flexible, due to the schistose scales.

SERPENTINE ROCK is composed of serpentine. Fine
granular, easily scratched with a knife. Generally of a dark
oil-green color and slightly greasy on a smooth surface.
The massive compact varieties which receive a good polish
are termed serpentine marbles. The origin of serpentine is
not well understood ; in some cases it appears to be derived
from magnesian clays, but perhaps more often by the altera-
tion of chrysolitic, augitic, and hornblendic rock.

INDEX TO TABLES.

Table A — Minerals with metallic luster 98-106

41 B — " without" " , streak colored 106-118

C— " " " " , " white or light gray 118-136

Actinolite, 126

Albite. 130

Amphibole, (Actinolite) 126, (Basal-
tic hornblende) no, 114, (Horn-
blende), 106, 118, 128, (Tremolite)
126

Analcite, 126

Andalusite, 134

Anglesite, 122

Anhydrite, 122

Anthracite coal, 106

Apatite, 128

Aragonite, 124

Argentite, 102, 104

Arsenopyrite, (Mispickel) 100

Augite, 108, 116, 130

Azurite, 118

Basaltic hornblende, no, 114
Beryl, 134
Biotite, 122
Bituminous coal, 106
Bornite, 98
Bronzite, 128

Calamine, 126

Calcite, 118, 122; (Chalk) 120, (Rock

milk) 118
Carnallite, 122

Cassiterite, 98, 106, no

Cerargyrite (Horn-silver), 120

Cerussite, 124

Chalcedonic quartz, 132

Chalcocite, 102, 104

Chalcopyrite, 98

Chalk, 120; red, 114

Chlorite, 116, 122

Chromite, 104

Chrysoberyl, 134

Chrysocolla, 116, 118, 124

Chrysolite, 132

Cinnabar, no, 114

Coal Anthracite, 106; Bituminous,

106

Copper, 98

Corundum (Sapphire, Ruby), 134
Crocidolite, 116
Cryolite, 122
Cuprite, 98, 108, 112

Diallage, 126
Diamond, 136
Dolomite, 124

Enstatite, 128
Erubescite, 98

Fluorite, 124
Franklinite, 104, 108

163

1 64

INDEX TO TABLES.

Galenite, IO2

Garnet, 132

Gold, 98

Graphite, 100, 102, 106

Gypsum, 120

Halite, 122

Hematite, (Specular iron ore) 102,

104, 112, (Red chalk) no
Hornblende, 106, no, 114, 118, 128
Horn-silver, 120
Hypersthene, 128

Jasper, 132
Kaolinite, 120

Lapis Lazuli, 118
Leucite, 130
Lignite, 108

Limonite, no, 114, (Yellow ocher)
112, lib

Magnetite, 104, 108

Malachite, 116

Malacolite, 130

Melaconite, 104, 106

Mica, (Muscovite) 120, (Biotite) 122

Microcline, 132

Mispickel, 100

Molybdenite, 100

Monazite, 128

Muscovite, 120

Nephelite, 130
Niter, 120

Ocher, yellow, 112
Olivine (Chrysolite), 132
Opal, 130
Orthoclase, 130

Proustite, 98, 112

Pyrargyrite, 104, 112

Pyrite, 100

Pyrolusite, 104

Pyroxene, (Augite) 108, 116, 130,,

(Diallage) 126, (Malacolite) 130
Pyrrhotite, 100

Quartz (Vitreous, Chalcedonic, Jas-
pery), 132

Red chalk, no

Ruby, 134

Rutile, 98, 106, no, 132

Sapphire, 134
Serpentine, 116, 124
Siderite, 114, 126
Silver, 100
Smithsonite, 126
Specular iron ore, 102
Sphalerite, 108, 114, 124
Spinel, 134
Stephanite, 104
Stibnite, 100
Sulphur, 112, 120

Talc, 120
Tennantite, 102
Tenorite, 106
Tetrahedrite, 102
Topaz, 134
Tourmaline, 134
Tremolite, 126
Turquois, 130

Willemite, 128
Witherite, 124

Zincite, 114

GENERAL INDEX.

PACK

Actinolite • 82

Adularia • . • • 87

Agate, common 75

fortification 75

, moss 76

Alabaster 68

Albite 87

Alexandrite 65

Alluvium 150

Almandine, almandite 84

Amethyst 75

Amianthus 82

Amphibole 81

group . 80

Amphigene 88

Analcime, analcite 89

Andalusite 90

Andesite 88, 157

Angles, constancy of 10

, interfacial 2

, plane, solid 2

Anglesite 50

Anhydrite 69

Anorthite 88

Antimony, glance 60

, gray ...... 60

Anthracite . 94

Apatite . . . 69

Aquamarine 84

Argentite, silver glance 40

Argillite 160

Arragonite 72-

165

166 GENERAL INDEX.

PACK

Arsenopyrite 55

Asbestu s 82

Asbestus, ligniform 82

Augite 80

Aventurine . 75

Axes, crystallographic 6

of symmetry 3

, principal 17

Azurite 48

Basalt 156

Bauxite 63

Beauxite 63

Beryl 83

Biotite 86

Bituminous coal 95

Black copper ore 46

silver ore, stephanite 41

Blende, zinc 51

Bloodstone 76

Blown sand 150

Blowpipe test for iron, lead, zinc 30

, use of 29

Bog-iron ore 58

Bornite 44

Bort 32

Breccia 143

Brittleness, property of 26

Bronzite 81

Buhrstone 76, 145

Cairngorm 75

Calamine 52

Calcite 70

Calcium, compounds of 67

phosphate 69.

sulphate, hydrous 69

Calcspar : 70

Carbonaceous deposits 149

Carbonates 32

Carbuncle 85

Carnallite 67

Carnelian 76

Cassiterife 61

*"at's eye, chrysoberyl 65

quartz 75

GENERAL INDEX. l6/

PACK

Cerargyrite, horn-silver • 41

Cerussite 50

Chalcedony 75

Chalcocite 45

Chalcopyrite 45

Chalk . 71, 147

, French 92

Chalybite 59

Chemical properties of minerals 27

Charcoal, use of 28

Chert 145

Chlorite. '«. 94

Chloropfcane 67

Chromite Bo

Chrysoberyl » 64

Chrysocolla 48

Chrysolite 83,

Chrysoprase 76

Chrysotile 93

Cinnabar 42:

Cinnamon-stone 84

Clay, common 90, 143,

, fire 144

Cleavage 8, 9

Coal, anthracite 94

, bituminous 96

Coal, brown 95

, cannel 95

, mineral 94

Colophonite 84

Color of minerals 25

Columnar structure 23

Concretions ' 24

Conglomerate, calcareous 148

, quartz 143

Copper, common, test for 44

glance 45

, native, occurrence of 43

ores 44

pyrites 45

, variegated 46

, vitreous 45

Corundum 62

Coquina 14?

Crocidolite 82

Cryolite 66

168 GENERAL INDEX.

PAGE

Crystalline aggregates 23

systems. i !

Crystallography, geometric .,.. 2

, physical 2

Crystals, definition I

, relating to 8

, distortion in 19

, multiple 20

, parallel grouping 20

, twins, contact, penetration 21

Cuprite 46

Dendritic structure 23

Detritus 151

Diabase . • 155

Diallage 80

Diamond 32

, source of 33

Diaspore 63

Diorite 155

Distortions in crystals 19

Dog-tooth spar 72

Dolerite 157

Dolomite 73, 147

Downs 150

Drift 151

Drusy surface 23

Dunes 150

Edge, beveled 9

, replaced 9

. , truncated 9

Edges I

Electro-silicon 78

Emerald 83

Emery 63

Enstatite :, 81

Erubescite. 46

Essonite 84

Eurite 154

Faces 1,9

, curved, striated 20

Feldspar 86, 87

, common, potash 87

, soda > 87

GENERAL INDEX. 169

PAGE

Telsite 157

Felspathoid group 88

Fibrous structure 23

Fiorite 77

Flagstone , 143

Flexibility, property of 26

Flint 76, 145

Fluorite 67

Fluorspar 67

Fluxes , 30

Foliated structure 158

Forceps, use of 28

Forests, petrified 76

Forms, clinometric 6

, closed, open 18

, fundamental 8

, holohedral, hemihedral 19

, orthometric 6

, unit 8

Franklinite 58

Gabbro 155

Galena 50

Galenite 50

Garnet , 84

, precious i- 84

Geodes 24

Geyserite 77, 145

Glauconite 148

Gneiss, common , 159

, syenitic .._• • • .*. 159

Gold, method of obtaining 37

, native ... • . 36

, occurrence of 36

, production in U. S 38

Granite 154

, graphic , 154

, hornblendic 155

, porphyritic 154

, syenitic 154

Granular structure 23

Granulite 154

Graphite 33

Gravel 142

Gravity, specific » 26

'Gray antimony. 66

GENERAL INDEX.

PACK

Gray copper ore 46

Greensand ' 148

Greenstone, trap 157

Grindstones 143

Grit * 143

Guano 150

Gypsum 68, 144

Halite....* 65,

Hammer, and anvil, use of 28

Hardness table of 26

Heliotrope 76

Hematite, brown 58

, red 56

Hemihedral 19,

Holohedral \ 19

Hornblende 83,

Horn-silver, cerargyrite 41

Hypersthene 81

Ice-stone 66

Iceland spar 72

Indices, rationality of 9,

Indicolite 92

Infusorial earth 79

Iron carbonate 59

, native 53

, ores of 54

Pyrites 54

Isomorphism 21

Itacolumite 161

Jasper 76

Jet....- 95

Kaolinite 90

Labradorite 88

Lamellar structure 23

Lapis lazuli. 85

Law of axial ratios ; gfr

Lead carbonate 50

, ores of 49

sulphate 50

sulphide 49

Lepidolite 86,

GENERAL INDEX.

Leucite 88

Lewis, H. C 33

Limestone, chemically deposited 71

, crinoidal 148

, hydraulic 147

, lithographic 71

, nummulitic 148

, oolitic 71

, origin organic 146

, siliceous 148

Limonite 58

Liparite 156

Lithographic limestone 71

Loess I5a

Magnesium limestone 73

Magnetic pyrites 55

Magnetite 57

Malachite 47

Malacolite 80

Malleability, property of 26

Manganese, black oxide of 60

Marble 148, 160

, architectural 160

, brecciated 149

, serpentine 161

, statuary 160

, variegated 149

Marl 146

, shell- 147

Martite 57

Melaconite 47

Mica 85

, uses of 86

Microline 88

Milky quartz ; ... 75

Mineralogy, chemical 2

, crystallographic 2

, definition i

, descriptive , 3

Mineral species I

Minerals, definition I

Mispickel 55

Monazite 64

Mortar, steel , 28

, agate 4 28

1/2 GENERAL INDEX.

PAGE

Moss-agate ....».••*»»••• , 76

Mountain leather , , • 82

Multiple crystals , 20

Mundic. 56

Muscovite 86

Nepheline, nephelite. 89

Niter * 66

Novaculite 143

Obsidian 155

Ocherous ore, iron .. 58

Odors of minerals 26

Oilstone -. » • 143

Oligoclase 89

OH vine * 83

Onyx *. 76

Oolite 144

Oolitic limestone , 71

Opal ,...,, , 77

Opalescence... ...... ,.,..,., ....... 25

Ophiolite ... ., 93, 161

Orthoclase 87

Parallel grouping 20

Parameters, rationality of 9

Paving-stones , , 143

Peat , , 149

Pegmatite , 154

Peperino ... 151

Peridot 83

Phonolite ,. 156

Phosphorescence , 25

Physical properties of minerals,. 25

Plagioclase • • .,..• t . . . . 88

Planes, like , 9

, location by axes 7

, similar... , 9

Platinum, native. , .,.,.. 38

Play of colors , , 25

Plumbago 33

Porphyrite 157, 158

Porphyry, quartz- 15^

Proustite, red silver ore ^ 41

Pseudomorphs 21

Pudding-stone. ., ... ..,..,. 143

GENERAL INDEX. I 7$

PAGE

Pumice 156

Pyrargyrite, ruby silver • . . 40

Pyrites, iron.. . . 54

Pyrolusite 61

Py rope 84

Pyroxene division . . 79

group 80

Pyrrhotite 55

Quartz 74

, chalcedonic series 75

, crystalline series 74

, granular 76

Quartzite 161

Reagents 30

Red copper ore 46

Rhyolite 156

Rock crystal 74

-forming minerals. 139, 140

milk 72

Rocks, aqueous 142

, chemically deposited 144

, classification of 140

Rock salt * 65

Rocks, common 139

, constituents of ; 139

, eruptive ^ . * , 155

, general classes of 141

, igneous, classification of •. 153

, characteristics of . . . . i. 152, 153

, origin of. ; < 152

, unstratified < ***«.»• 152

, intermediate ;....* *... 157

r intrusive « « -. • 157

, land-formed • . * 149

, metamorphic 159

organic in origin 146

, plutonic < * 154

, sedimentary 141

, tabular classification of... 157

, volcanic f 155

Rose quartz ...*........ 75

Rubellite •. 92

Rubies, Arizona. ................ 4 85

Ruby, common ...;;*.....-.... * ..«.-.<..•« * 66

174 GENERAL INDEX,

PAGE

Ruby, oriental 63

Ruby silver, pyrargyrite 40

Rutile 62

Salt, common rock 66, 144

Saltpeter 66

Sand 142

Sands, blown 149

Sandstone ' 142

, flexible, itacolumite 161

Sanidin 87

Sapphire 63

Sard 76

Sardonyx 76

Satin spar, calcite 72

, gypsum * . 68

Schists 160

chlorite 160

hornblende 160

hydromica 160

mica 1 60

talcose 160

Scythestone 143

Sectility, property of 26

Selenite 68

Serpentine, precious, common 93

rock 161

Shale 144

Siderite 59

Silica 74, 139

Silicates, classification of 78

Siliceous sinter 77

Silver glance, argentite 40

Silver, native 39

, ores of , 40

, sources of 41

Slate, clay 160

Smithsonite 52

Smoky quartz 75

Soapstone 92

Soil 149

Spathic iron ore 59

Specific gravity 26

Specular iron ore 56

Sphalerite 51

Spinel 64

GENERAL INDEX. 1/5

PAGE

Stalactites 71, I4g

Stalactitic structure 24

Stalagmites ylt I45

Steatite 92

Stephanite, black silver ore 41

Stibnite 60

Stratified structure 24

Streak of minerals.. . . . 25

Sulphur, native ^4

, sources of 35

Syenite I55

Symmetry, axes of 3

, center of 4

, crystallographic 3

, elements of 3

, planes of 3, 17

Systems, crystalline, isometric n

, monoclinic 15

, orthorhombic ..... 14

, tetragonal, hexagonal 12

, triclinic 5

Tables, description of use 96

Talc 92

, indurated 92

Talus 151

Tennantite < 46

Tests, miscellaneous •. < 31

Tetrahedrite 45

Till 152

Tin ore, black 61

oxide 61

stone • 61

Topaz 89

Tourmaline 91

Trachyte 156

, quartz 156

Trap-rock 157

Travertine 71, 145

Tremolite 82

Tridymite 77

Tripolite 77

Tubes, closed 29

, test with 31

, open 29

, test with 30

176 GENERAL INDEX.

PAGE:

Tufa, calcareous 71

, volcanic ;.. 151

Turquois 63

Ultramarine 85

Verd-antique v 93i 161

White lead ore 5°

Willemite 52

Wire, platinum, use of 29

Witherite 74

Zinc blende 53

carbonate 53

, ores of 5i

silicate 52

Zincite 52

Zonal relations » Jo

Zone • 10

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ists 16mo, morocco, 2 00

Stockbridge's Rocks and Soils 8vo, 2 50

* Tillman's Elementary Lessons in Heat 8vo, 1 50

Descriptive General Chemistry 8vo, 3 00

Turneaure and Russell's Public Water-supplies 8vo, 5 00

Van Deventer's Physical Chemistry for Beginners. (Boltwood.)

12mo, 1 50

Walke's Lectures on Explosives 8vo, 4 00

Wells's Laboratory Guide in Qualitative Chemical Analysis.

..8vo, 1 50

" Short Course in Inorganic Qualitative Chemical Analy-
sis for Engineering Students 12mo, 1 50

Whipple's Microscopy of Drinking-water ; 8vo, 3 50

Wiechmann's Sugar Analysis Small 8vo, 2 50

" Lecture-notes on Theoretical Chemistry. . . .12mo, 3 00

Wilson's Cyanide Processes 12mo, 1 50

" Chlorination Process 12mo, 1 50

Wulling's Elementary Course in Inorganic Pharmaceutical and

Medical Chemistry 12mo, 2 00

CIVIL ENGINEERING.

BRIDGES AND ROOFS. HYDRAULICS. MATERIALS OF
ENGINEERING. RAILWAY ENGINEERING.

Baker's Engineers' Surveying Instruments 12mo, 3 00

Bixby's Graphical Computing Table Paper, 19£x24£ inches. 25

Davis's Elevation and Stadia Tables 8vo, 1 00

Folwell's Sewerage. (Designing and Maintenance.) 8vo, 3 00

Freitag's Architectural Engineering 8vo, 3 50

Goodhue's Municipal Improvements 12mo, 1 75

Goodrich's Economic Disposal of Towns' Refuse 8vo, 3 50

Gore's Elements of Geodesy 8vo, 2 50

Hayford's Text-book of Geodetic Astronomy .8vo, 3 00

Howe's Retaining-walls for Earth 12mo, 1 25

Johnson's Theory and Practice of Surveying Small 8vo, 4 00

Stadia and Earth- work Tables 8vo, 1 25

Kiersted's Sewage Disposal 12mo, 1 25

Mahan's Treatise on Civil Engineering. (1873.) (Wood.) . .8vo, 500

* Mahan's Descriptive Geometry 8vo, 1 50

Merriman's Elements of Precise Surveying and Geodesy. . . .8vo, 2 50

Merriman and Brooks's Handbook for Surveyors. . . ,16mo, mor., 2 00

Merriman's Elements of Sanitary Engineering 8vo, 2 00

Xugent's Plane Surveying. (In preparation.)

Ogden's Sewer Design 12mo, 2 00

Patton's Treatise on Civil Engineering 8vo, half leather, 7 50

Reed's Topographical Drawing and Sketching 4to, 5 00

Rideal's Sewage and the Bacterial Purification of Sewage . . 8vo, 3 50

Siebert and Biggin's Modern Stone-cutting and Masonry . . 8vo, 1 50

Smith's Manual of Topographical Drawing. (McMillan.) . .8vo, 2 50

* Trautwine's Civil Engineer's Pocket-book. ... 16mo, morocco, 5 00
Wait's Engineering and Architectural Jurisprudence 8vo, 6 00

Sheep, 6 50

" Law of Operations Preliminary to Construction in En-
gineering and Architecture 8vo. 5 00

Sheep, 5 50

" Law of Contracts 8vo, 3 00

Warren's Stereotomy — Problems in Stone-cutting 8vo, 2 50

Webb's Problems in the Use and Adjustment of Engineering

Instruments 16mo, morocco, 1 25

* Wheeler's Elementary Course of Civil Engineering 8vo, 4 00

Wilson's Topographic Surveying 8vo, 3 50

BRIDGES AND ROOFS.

Boiler's Practical Treatise on the Construction of Iron Highway

Bridges 8vo, 2 00

* Boiler's Thames River Bridge 4to, paper, 5 00

Burr's Course on the Stresses in Bridges and Roof Trusses,

Arched Ribs, and Suspension Bridges 8vo, 3 50

Du Bois's Stresses in Framed Structures Small 4to, 10 00

Foster's Treatise on Wooden Trestle Bridges 4to, 5 00

Fowler's Coffer-dam Process for Piers 8vo, 2 50

Greene's Roof Trusses 8vo, 1 25

" Bridge Trusses 8vo, 2 50

" Arches in Wood. Iron, and Stone 8vo, 2 50

Howe's Treatise on Arches Svo, 4 00

Johnson, Biyan and Turneaure's Theory and Practice in the

Designing of Modern Framed Structures Small 4to, 10 00

Merriman and Jacoby's Text-book on Roofs and Bridges:

Part I.— Stresses in Simple Trusses 8vo, 2 50

Part II.— Graphic Statics 8vo, 2 00

Part III.— Bridge Design. Fourth Ed. (In preparation.} , .8vo, 250

Part IV.— Higher Structures 8vo, 2 50

Morison's Memphis Bridge 4to, 10 00

WaddelPs De Pontibus, a Pocket Book for Bridge Engineers.

16mo, mor., 3 00

Specifications for Steel Bridges 12mo, 1 25

Wood's Treatise on the Theory of the Construction of Bridges

and Roofs 8vo, 2 00

Wright's Designing of Draw-spans:

Part I. — Plate-girder Draws 8vo, 2 50

Part II. — Riveted-truss and Pin-connected Long-span Draws.

8vo, 2 50

Two parts in one volume 8vo, 3 50

HYDRAULICS.

Bazin's Experiments upon the Contraction of the Liquid Vein

Issuing from an Orifice. (Trautwine.) 8vo, 2 00

Bovey's Treatise on Hydraulics 8vo, 5 00

Church's Mechanics of Engineering 8vo, 6 00

Coffin's Graphical Solution of Hydraulic Problems. . 16mo, mor., 2 50

Flather's Dynamometers, and the Measurement of Power. 12mo, 3 00

FQ! well's Water-supply Engineering 8vo, 4 00

Frizell's Water-power 8vo, 5 00

Fuertes's Water and Public Health 12mo, 1 50

" Water-filtration Works 12mo, 2 50

Ganguillet and Kutter's General Formula for the Uniform
Flow of Water in Rivers and Other Channels. (Her-

ing and Trautwine.) 8vo, 4 00

Hazen's Filtration of Public Water-supply ^^ 8vo, 3 00

Hazleurst's Towers and Tanks for Water-works 8vo, 2 50

Herschel's 115 Experiments on the Carrying Capacity of Large,

Riveted, Metal Conduits 8vo, 2 00

Mason's Water-supply. (Considered Principally from a Sani-
tary Standpoint.) 8vo, 5 00

Merriman's Treatise on Hydraulics 8vo, 4 00

* Michie's Elements of Analytical Mechanics 8vo, 4 00

Schuyler's Reservoirs for Irrigation, Water-power, and Domestic

Water-supply Large 8vo, 5 00

Turneaure and Russell. Public Water-supplies 8vo, 5 00

Wegmann's Design and Construction of Dams 4to, 5 00

Water-supply of the City of New York from 1658 to

1895 4k>, 10 00

WTeisbach's Hydraulics and Hydraulic Motors. (Du Bois.) . .8vo, 5 00

Wilson's Manual of Irrigation Engineering Small 8vo, 4 00

Wolff's Windmill as a Prime Mover 8vo, 3 00

Wood's Turbines 8vo, 2 50

" Elements of Analytical Mechanics 8vo, 3 00

MATERIALS OF ENGINEERING.

Baker's Treatise on Masonry Construction 8vo, 500

Black's United States Public Works Oblong 4to, 5 00

Bovey's Strength of Materials and Theory of Structures. . . .8vo, 7 50

Burr's Elasticity and Resistance of the Materials of Engineer-
ing , . . 8vo, 5 00

Byrne's Highway Construction 8vo, 5 00

" Inspection of the Materials and Workmanship Em-
ployed in Construction 16mo, 3 00

Church's Mechanics of Engineering 8vo, 6 00

Du Bois's Mechanics of Engineering. Vol. I Small 4to, 10 00

Johnson's Materials of Construction Large 8vo, 600

Keep's Cast Iron. (In preparation.)

Lanza's Applied Mechanics 8vo, 7 50

Martens's Handbook on Testing Materials. (Henning.)

2 vols., 8vo, 7 50

Merrill's Stones for Building and Decoration '. . 8vo, 5 00

Merriman's Text-book on the Mechanics of Materials 8vo, 4 00

Merriman's Strength of Materials 12mo, 1 00

Metcalf s Steel. A Manual for Steel-users 12mo, 2 00

Patton's Practical Treatise on Foundations 8vo, 5 00

Rockwell's Roads and Pavements in France 12mo, 1 25

Smith's Wire: Its Use and Manufacture Small 4to, 3 00

Spalding's Hydraulic Cement 12mo, 2 00

Text-book on Roads and Pavements 12mo, 2 00

Thurston's Materials of Engineering 3 Parts, 8vo, 8 00

Part I. — Non-metallic Materials of Engineering and Metal-
lurgy 8vo, 2 00

Part II.— Iron and Steel 8vo, 3 50

Part III. — A Treatise on Brasses, Bronzes and Other Alloys

and Their Constituents 8vo, 2 50

Thurston's Text-book of the Materials of Construction 8vo, 5 00

Tillson's Street Pavements and Paving Materials 8vo, 4 00

WaddelFs De Pontibus. (A Pocket-book for Bridge Engineers.)

16mo, morocco, 3 00

Specifications for Steel Bridges 12mo, 1 25

Wood's Treatise on the Resistance of Materials, and an Ap-
pendix on the Preservation of Timber 8vo, 2 00

" Elements of Analytical Mechanics 8vo, 3 00

RAILWAY ENGINEERING,

Berg's Buildings and Structures of American Railroads. .4to, 5 00

Brooks's Handbook of Street Railroad Location. . 16mo, morocco, 1 50

Butts's Civil Engineer's Field-book 16mo, morocco, 2 50

CrandalPs Transition Curve 16mo, morocco, 1 50

Railway and Other Earthwork Tables 8vo, 1 50

Dawson's Electric Railways and Tramways . Small 4to, half mor., 12 50
" "Engineering" and Electric Traction Pocket-book.

16mo, morocco, 4 00

Dredge's History of the Pennsylvania Railroad: (1879.) .Paper, 5 00
* Drinker's Tunneling, Explosive Compounds, and Rock Drills.

4to, half morocco, 25 00

Fisher's Table of Cubic Yards Cardboard, 25

Godwin's Railroad Engineers' Field-book and Explorers' Guide.

16mo, morocco, 2 50

Howard's Transition Curve Field-book 16mo, morocco, 1 50

Hudson's Tables for Calculating the Cubic Contents of Exca-
vations and Embankments 8vo, 1 00

Nagle's Field Manual for Railroad Engineers. . . .16mo, morocco, 3 00

PhSbrick's Field Manual for Engineers 16mo, morocco, 3 00

Pratt and Alden's Street-railway Road-bed 8vo, 2 00

Searles's Field Engineering ISrno, morocco, 3 00

" Railroad Spiral 16mo, morocco, 1 50

Taylor's Prismoidal Formulae and Earthwork 8vo, 1 50

* Trautwine's Method of Calculating the Cubic Contents of Ex-

cavations and Embankments by the Aid of Dia-
grams 8vo, 2 00

* The Field Practice of Laying Out Circular Curves

for Railroads 12mo, morocco, 2 50

* " Cross-section Sheet Paper, 25

Webb's Railroad Construction 8vo, 4 00

Wellington's Economic Theory of the Location of Railways. .

Small 8vo, 5 00

DRAWING.

Barr's Kinematics of Machinery 8vo, 2 50

* Bartlett's Mechanical Drawing .8vo, 3 00

Durley's Elementary Text-book of the Kinematics of Machines.

(In preparation.)

Hill's Text-book on Shades and Shadows, and Perspective. . 8vo, 2 00
Jones's Machine Design:

Part I. — Kinematics of Machinery ." 8vo, 1 50

Part II.— Form, Strength and Proportions of Parts 8vo, 3 00

-MacCord's Elements of Descriptive Geometry 8vo, 3 00

Kinematics; or, Practical Mechanism 8vo, 5 00

Mechanical Drawing 4to, 4 00

Velocity Diagrams 8vo, I 50

* Mahan's Descriptive Geometry and Stone-cutting 8vo, 1 50

Mahan's Industrial Drawing. (Thompson.) 8vo, 3 50

Reed's Topographical Drawing and Sketching 4to, 5 00

Reid's Course in Mechanical Drawing 8vo, 2 00

" Text-book of Mechanical Drawing and Elementary Ma-
chine Design 8vo, 3 00

Robinson's Principles of Mechanism 8vo, 3 00

Smith's Manual of Topographical Drawing. (McMillan.) .8vo, 2 50
Warren's Elements of Plane and Solid Free-hand Geometrical

Drawing 12mo, 1 00

Drafting Instruments and Operations 12mo, 1 25

Manual of Elementary Projection Drawing 12mo, 1 50

" Manual of Elementary Problems in the Linear Per-
spective of Form and Shadow 12mo, 1 00

" Plane Problems in Elementary Geometry 12mo, 1 25

" Primary Geometry 12mo, 75

" Elements of Descriptive Geometry, Shadows, and Per-
spective 8vo, 3 50

General Problems of Shades and Shadows 8vo, 3 00

Elements of Machine Construction and Drawing. .8vo, 7 50
" Problems, Theorems, and Examples in Descriptive

Geometry 8vo, 2 50

Weisbach's Kinematics and the Power of Transmission. (Herr-
mann and Klein.) 8vo, 5 00

Whelpley's Practical Instruction in the Art of Letter En-
graving 12mo, 2 00

Wilson's Topographic Surveying 8vo, 3 50

Wilson's Free-hand Perspective 8vo, 2 50

Woolf's Elementary Course in Descriptive Geometry. . Large 8vo, 3 00

ELECTRICITY AND PHYSICS.

Anthony and Brackett's Text-book of Physics. (Magie.)

Small 8vo. 3 00
Anthony's Lecture-notes on the Theory of Electrical- Measur-

ments " 12mo. 1 00

Benjamin's History of Electricity 8vo. 3 00

Benjamin's Voltaic Cell Svo. 3 00

Classen's Qantitative Chemical Analysis by Electrolysis. Her-

rick and Boltwood.) ". 8vo. 3 00

Crehore and Squier's Polarizing Photo-chronograph Svo. .3 00

Dawson's Electric Railways and Tramways..Small 4to, half mor.. 12 50
Dawson's " Engineering " and Electric Traction Pocket-book.

16mo, morocco, 4 00

Flather's Dynamometers, and the Measurement of Power. . 12mo. 3 00

Gilbert's De Magnete. (Mottelay.) Svo, 2 50

Holman's Precision of Measurements Svo, 2 00

Telescopic Mirror-scale Method, Adjustments, and

Tests Large Svo. 75

Landauer's Spectrum Analysis. (Tingle.) -. Svo, 3 00

Le Chatelier's High-temperature Measurements. (Boudouard —

Burgess.) 12mo. 3 00

Lob's Electrolysis and Electrosynthesis of Organic Compounds.

(Lorenz.) ". 12mo. 1 00

Lyons's Treatise on Electromagnetic Phenomena Svo, 6 00

* Michie. Elements of Wave Motion Relating to Sound and

Light Svo. 4 00

Niaudet's Elementary Treatise on Electric Batteries (Fish-
back.) 12mo. 2 50

* Parshall and Hobart's Electric Generators-Small 4ta, half mor., 10 00
Thurston's Stationary Steam-engines Svo. 2 50

* Tillman. Elementary Lessons in Heat Svo, 1 50

Tory and Pitcher. Manual of Laboratory Physics. .Small Svo. 2 00

LAW.

* Davis. Elements of Law Svo. 2 50

* " Treatise on the Military Law of United States. .Svo, 7 00

Sheep, 7 50

Manual for Courts-martial IGmo, morocco, 1 50

Wait's Engineering and Architectural Jurisprudence Svo, 6 00

Sheep, 6 50

" Law of Operations Preliminary to Construction in En-
gineering and Architecture ; < Svo, 5 00

Sheep, 5 50

" Law of Contracts Svo, 3 00

Winthrop's Abridgment of Military Law 12mo, 2 50

MANUFACTURES.

Beaumont's Woollen and Worsted Cloth Manufacture. .. .12mo. 1 50
Bernadou's Smokeless Powder — Nitro-cellulose and Theory of

the Cellulose Moleeule f2mo, 2 50

Bolland's Iron Founder 12mo, cloth, - •"><>

" The Iron Founder " Supplement 12mo, 2 50

" Encyclopedia of Founding and Dictionary of Foundry

Terms Used in the Practice of Moulding. .. . 12mo. 3 00

Eissler's Modern High Explosives Svo, 4 00

Effront's Enzymes and their Applications. (Prescott.) (In preparation.)

Fitzgerald's Boston Machinist ISmo, 1 00

Ford's Boiler Making for Boiler Makers 18mo, 100

Hopkins's Oil-chemists' Handbook Svo, 3 00

Keep's Cast Iron. (In preparation.)

Metcalf s Steel. A Manual for Steel-users 12mo, 2 00

Metcalf's Cost of Manufactures — And the Administration of

Workshops, Public and Private Svo, 5 00

Meyer's Modern Locomotive Construction . 4to, 10 00

* Reisig's Guide to Piece-dyeing Svo, 25 00

Smith's Press-working of Metals 8vo, 3 00

" Wire: Its Use and Manufacture Small 4to, 3 00

Spalding's Hydraulic Cement 12mo, 2 00

Spencer's Handbook for Chemists of Beet-sugar Houses.

16mo, morocco, 3 00

Handbook for Sugar Manufacturers and their Chem-
ists 16mo, morocco, 2 00

Thurston's Manual of Steam-boilers, their Designs, Construc-
tion and Operation 8vo, 5 00

Walke's Lectures on Explosives 8vo, 4 00

West's American Foundry Practice 12mo, 2 50

" Moulder's Text-book 12mo, 2 50

Wiechmann's Sugar Analysis Small 8vo, 2 50

Wolff's Windmill as a Prime Mover 8vo, 3 00

Woodbury's Fire Protection of Mills 8vo, 2 50

MATHEMATICS.

Baker's Elliptic Functions 8vo, 1 50

* Bass's Elements of Differential Calculus 12mo, 4 00

Briggs's Elements of Plane Analytic Geometry 12mo. 1 00

Chapman's Elementary Course in Theory of Equations.. .12mo, 1 50

Compton's Manual of Logarithmic Computations... 12mo, I 50

Da vis's Introduction to the Logic of Algebra 8vo, 1 59

Halsted's Elements of Geometry Svo, 1 75

Elementary Synthetic Geometry 777 Svo, 1 50

Johnson's Three- place Logarithmic Tables : Vest-pocket size, pap., 15

100 copies for 5 00

Mounted on heavy cardboard, 8 X 10 inches, 25

10 copies for 2 00
Elementary Treatise on the Integral Calculus.

Small Svo, 1 50

Curve Tracing in Cartesian Co-ordinates 12mo, 1 00

" Treatise on Ordinary and Partial Differential

Equations Small Svo, 3 50

Theory of Errors and the Method of Least

Squares 12mo, 1 50

Theoretical Mechanics , ... 12mo, 3 00

* Ludlow and Bass. Elements of Trigonometry and Logarith-

mic and Other Tables Svo, 3 00

Trigonometry. Tables published separately. .Each, 2 00

Merriman and Woodward. Higher Mathematics Svo, 5 00

Merriman's Method of Least Squares Svo, 2 00

Rice and Johnson's Elementary Treatise on the Differential

Calculus Small Svo, 3 00

Differential and Integral Calculus. 2 vols.

in one Small Svo, 2 50

Wood's Elements of Co-ordinate Geometry Svo, 2 00

" Trigometry: Analytical, Plane, and Spherical. .. .12mo, 1 00

MECHANICAL ENGINEERING.

MATERIALS OF ENGINEERING, STEAM ENGINES
AND BOILERS.

Baldwin's Steam Heating for Buildings • 12mo, 2 50

Barr's Kinematics of Machinery 8vo, 2 50

* Bartlett's Mechanical Drawing 8vo, 3 00

Benjamin's Wrinkles and Recipes 12mo, 2 00

Carpenter's Experimental Engineering 8vo, 6 00

Heating and Ventilating Buildings 8vo, 3 00

Clerk's Gas and Oil Engine Small 8vo, 4 00

Cromwell's Treatise on Toothed Gearing 12mo, 1 50

Treatise on Belts and Pulleys 12mo, 1 50

Durley's Elementary Text-book of the Kinematics of Machines.

(In preparation.)

Flather's Dynamometers, and the Measurement of Power . . 12mo, 3 00

" Rope Driving 12mo, 2 00

Gill's Gas an Fuel Analysis for Engineers 12mo, 1 25

Hall's Car Lubrication 12mo, 1 00

Jones's Machine Design:

Part I. — Kinematics of Machinery 8vo, 1 50

Part II. — Form, Strength and Proportions of Parts 8vo, 3 09

Kent's Mechanical Engineers' Pocket-book. .. .16mo, morocco, 5 00
Kerr's Power and Power Transmission. (In preparation.)

MacCord's Kinematics ; or, Practical Mechanism 8vo, 5 00

Mechanical Drawing 4to, 4 00

Velocity Diagrams 8vo, 1 50

Mahan's Industrial Drawing. (Thompson.) 8vo, 3 50

Pople's Calorific Power of Fuels 8vo, 3 00

Reid's Course in Mechanical Drawing 8vo, 2 00

" Text-book of Mechanical Drawing and Elementary

Machine Design 8vo, 3 00

Richards's Compressed Air 12mo, 1 50

Robinson's Principles of Mechanism 8vo, 3 00

Smith's Press-working of Metals 8vo, 3 00

Thurston's Treatise on Friction and Lost Work in Machin-
ery and Mill Work 8vo, 3 00

Animal as a Machine and Prime Motor and the

Laws of Energetics 12mo, 1 00

Warren's Elements of Machine Construction and Drawing. .8vo, 7 50
Weisbach's Kinematics and the Power of Transmission. (Herr-
mann—Klein.) 8vo, 5 00

" Machinery of Transmission and Governors. (Herr-
mann—Klein.) i '. 8vo, 5 00

Hydraulics and Hydraulic Motors. (Du Bois.) .8vo, 5 00

Wolff's Windmill as a Prime Mover '. 8vo, 3 00

Wood's Turbines 8vo, 2 50

MATERIALS OF ENGINEERING.

Bovey's Strength of Materials and Theory of Structures. .8 vo, 7 50
Burr's Elasticity and Resistance of the Materials of Engineer-
ing 8vo, 5 00

Church's Mechanics of Engineering 8vo, 6 00

Johnson's Materials of Construction Large 8vo, 6 00

Keep's Cast Iron. (In preparation.)

Lanza's Applied Mechanics 8vo, 7 50

Martens's Handbook on Testing Materials. (Henning.) . . . .8vo, 7 50

Merriman'd Text-book on the Mechanics of Materials .... 8vo, 4 00

Strength of Materials 12mo, 1 00

Metcalf's Steel. A Manual for Steel-users 12mo, 2 00

Smith's Wire: Its Use and Manufacture Small 4to, 3 00

Thurston's Materials of Engineering 3 vols., 8vo, 8 00

Part II.— Iron and Steel 8vo, 3 50

Part III. — A Treatise on Brasses, Bronzes and Other Alloys

and their Constituents 8vo, 2 50

Thurston's Text-book of the Materials of Construction. .. .8vo, 5 00
Wood's Treatise on the Resistance of Materials and an Ap-
pendix on the Preservation of Timber 8vo, 2 00

" Elements of Analytical Mechanics 8vo, 3 00

STEAM ENGINES AND BOILERS.

Carnot's Reflections on the Motive Power of Heat. (Thurston.)

12mo, 1 50
Dawson's " Engineering " and Electric Traction Pocket-book.

16mo, morocco, 4 00

Ford's Boiler Making for Boiler Makers 18mo, 1 00

Hemenway's Indicator Practice and Steam-engine Economy.

12mo, 2 00

Hutton's Mechanical Engineering of Power Plants 8vo, 5 00

" Heat and Heat-engines 8vo, 5 00

Kent's Steam-boiler Economy 8vo, 4 00

Kneass's Practice and Theory of the Injector 8vo, 1 50

MacCord's Slide-valves 8vo, 2 00

Meyer's Modern Locomotive Construction 4to, 10 00

Peabody's Manual of the Steam-engine Indicator 12mo, 1 50

Tables of the Properties of Saturated Steam and

Other Vapors 8vo, 1 00

" Thermodynamics of the Steam-engine and Other

Heat-engines 8vo, 5 00

Valve-gears for Steam-engines 8vo, 2 50

Peabody and Miller. Steam-boilers 8vo, 4 00

Pray's Twenty Years with the Indicator Large 8vo, 2 50

Pupin's Thermodynamics of Reversible Cycles in Gases and

Saturated Vapors. (Osterberg.) 12mo, 1 25

Reagan's Locomotive Mechanism and Engineering 12mo, 2 00

Rontgen's Principles of Thermodynamics. (Du Bois.) . . . .8vo, 5 00

Sinclair's Locomotive Engine Running and Management. . 12mo, 2 00

Smart's Handbook of Engineering Laboratory Practice. .12mo, 2 50

Snow's Steam-boiler Practice 8vo, 3 00

Spangler's Valve-gears 8vo, 2 50

Notes on Thermodynamics 12mo, 1 00

Thurston's Handy Tables 8vo, 1 50

Manual of the Steam-engine 2 vols., 8vo, 10 00

Part I.— History, Structure, and Theory 8vo, 6 00

Part II. — Design, Construction, and Operation 8vo, 6 00

Thurston's Handbook of Engine and Boiler Trials, and the Use

of the Indicator and the Prony Brake 8vo, 5 00

Stationary Steam-engines 8vo, 2 50

Steam-boiler Explosions in Theory and in Prac-
tice 12mo, 1 50

Manual of Steam-boilers, Their Designs, Construc-
tion, and Operation 8vo, 5 00

Weisbach's Heat, Steam, and Steam-engines. (Du Bois.). .8vo, 5 00

Whitham's Steam-engine Design 8vo, 5 00

Wilson's Treatise on Steam-boilers- (Flather.) 16mo, 2 50

Wood's Thermodynamics, Heat Motors, and Refrigerating

Machines 8vo, 4 00

MECHANICS AND MACHINERY.

Barr's Kinematics of Machinery 8vo, 2 50

Bovey's Strength of Materials and Theory of Structures. .8vo, 7 50

Chordal.— Extracts from Letters 12mo, 2 00

Church's Mechanics of Engineering Svo, 6 00

Notes and Examples in Mechanics Svo, 2 00

Coinpton's First Lessons in Metal-working 12mo, 1 50

Compton and De Groodt. The Speed Lathe 12mo, 1 50

Cromwell's Treatise on Toothed Gearing 12mo, 1 50

Treatise on Belts and Pulleys 12mo, 1 50

Dana's Text-book of Elementary Mechanics for the Use of

Colleges and Schools 12ma, 1 50

Dingey's Machinery Pattern Making 12mo, 2 00

Dredge's Record of the Transportation Exhibits Building of the

World's Columbian Exposition of 1893 4to, half mor., 5 00

Du Bois's Elementary Principles of Mechanics:

Vol. I.— Kinematics Svo, 3 50

Vol. II.— Statics 8vo, 4 00

Vol. III.— Kinetics Svo, 3 50

Du Bois's Mechanics of Engineering. Vol. I Small 4to, 10 00

Durley's Elementary Text-book of the Kinematics of Machines.

(In preparation.)

Fitzgerald's Boston Machinist 16mo, 1 00

Flather's Dynamometers, and the Measurement of Power. 12mo, 3 00

" Rope Driving 12mo, 2 00

Hall's Car Lubrication 12mo, 1 00

Holly's Art of Saw Filing 18mo, * 75

* Johnson's Theoretical Mechanics 12mo, 3 00

Jones's Machine Design:

Part I — Kinematics of Machinery Svo, 1 50

Part II. — Form, Strength and Proportions of Parts. .. .Svo, 3 00
Kerr's Power and Power Transmission. (In preparation.)

Lanza's Applied Mechanics Svo, 7 50

MacCord's Kinematics; or, Practical Mechanism Svo, 5 00

" Velocity Diagrams Svo, 1 50

Merriman's Text-book on the Mechanics of Materials Svo, 4 00

* Michie's Elements of Analytical Mechanics Svo, 4 00

Reagan's Locomotive Mechanism and Engineering 12mo, 2 00

Reid's Course in Mechanical Drawing Svo, 2 00

" Text-book of Mechanical Drawing and Elementary

Machine Design Svo, 3 00

Richards's Compressed Air 12mo, 1 50

Robinson's Principles of Mechanism Svo, 3 00

Sinclair's Locomotive-engine Running and Management. .12mo, 2 00

Smith's Press- working of Metals Svo, 3 00

Thurston's Treatise on Friction and Lost Work in Machin-
ery and Mill Work Svo, 3 00

Animal as a Machine and Prime Motor, and the

Laws of Energetics 12mo, 1 00

Warren's Elements of Machine Construction and Drawing. .Svo, 7 50
Weisbach's Kinematics and the Power of Transmission.

(Herrman— Klein.) Svo, 5 00

" Machinery of Transmission and Governors. (Herr-

(man— Klein.) Svo, 5 00

Wood's Elements of Analytical Mechanics Svo, 3 00

" Principles of Elementary Mechanics 12mo, 1 25

" Turbines Svo, 2 50

The World's Columbian Exposition of 1893 4to, 1 00

METALLURGY.

Idlest on's Metallurgy of Silver, Gold, and Mercury:

Vol. I —Silver 8vo, 7 50

Vol. II.— Gold and Mercury 8vo, 7 50

Keep's Cast Iron. (In preparation.)

Kunhardt's Practice of Ore Dressing in Lurope 8vo, 1 50

Le Chatelier's High-temperature Measurements. (Boudouard —

Burgess.) 12mo, 3 00

Metcalf's Steel. A Manual for Steel-users 12mo, 2 00

Thurston's Materials of Engineering. In Three Parts 8vo, 8 00

Part II.— Iron and Steel 8vo, 3 50

Part III. — A Treatise on Brasses, Bronzes and Other Alloys

and Their Constituents 8vo, 2 50

MINERALOGY.

Barringer's Description of Minerals of Commercial Value.

Oblong, morocco, 2 50

Boyd's Resources • of Southwest Virginia 8vo, 3 00

" Map of Southwest Virginia Pocket-book form, 2 00

Brush's Manual of Determinative Mineralogy. (Penfield.) .8vo, 4 00

Chester's Catalogue of Minerals 8vo, paper, 1 00

Cloth, 1 25

Dictionary of the Names of Minerals 8vo, 3 50

Dana's System of Mineralogy Large 8vo, half leather, 12 50

" First Appendix to Dana's New " System of Mineralogy."

Large 8vo, 1 00

Text-book ftf Mineralogy 8vo, 4 00

Minerals and How to Study Them 12mo, 1 50

Catalogue of American Localities of Minerals . Large 8vo, 1 00

" Manual of Mineralogy and Petrography 12mo, 2 00

Egleston's Catalogue of Minerals and Synonyms 8vo, 2 50

Hussak's The Determination of Rock-forming Minerals.

(Smith.) Small 8vo, 2 00

* Penfield's Notes on Determinative Mineralogy and Record of

Mineral Tests . . ; 8vo, paper, 50

Rosenbusch's Microscopical Physiography of the Rock-making

Minerals. (Idding's.) .8vo, 500

* Tillman's Text-book of Important Minerals and Rocks . . 8vo, 2 00
Williams's Manual of Lithology 8vo, 3 00

MINING.

Beard's Ventilation of Mines 12mo, 2 50

Boyd's Resources of Southwest Virginia 8vo, 3 00

" Map of Southwest Virginia Pocket-book form, 2 00

* Drinker's Tunneling, Explosive Compounds, and Rock

Drills 4to, half morocco, 25 00

Eissler's Modern High Explosives 8vo, 4 00

Goodyear's Coal-mines of the Western Coast of the United

States 12mo, 250

Ihlseng's Manual of Mining 8vo, 4 00

Kunhardt's Practice of Ore Dressing in Europe 8vo, 1 50

O'Driscoll's Notes on the Treatment of Gold Ores 8vo, 2 00

Sawyer's Accidents in Mines 8vo, 7 00

Walke's Lectures on Explosives 8vo, 4 00

Wilson's Cyanide Processes 12mo, 1 50

Wilson's Chlorination Process 12mo, 1 50

Wilson's Hydraulic and Placer Mining 12uio, 2 00*

Wilson's Treatise on Practical and Theoretical Mine Ventila-
tion 12mo, 1 25

SANITARY SCIENCE.

Fol well's Sewerage. (Designing, Construction and Maintenance.)

8vo, 3 0(V

Water-supply Engineering 8vo, 4 00

Fuertes's Water and Public Health 12mo, 1 50

Water-filtration Works 12mo, 2 50

Gerhard's Guide to Sanitary House-inspection 16mo, 1 00

Goodrich's Economical Disposal of Towns' Refuse. . .Demy 8vo, 3 50

Hazen's Filtration of Public Water-supplies 8vo, 3 00

Kiersted's Sewage Disposal 12mo, 1 25

Mason's Water-supply. (Considered Principally from a San-
itary Standpoint 8vo, 5 00

" Examination of Water. (Chemical and Bacterio-
logical.) 12mo, 1 25

Merriman's Elements of Sanitary Engineering 8vo, 2 00

Nichols's Water-supply. (Considered Mainly from a Chemical

and Sanitary Standpoint.) (1883.) 8vo, 2 50

Ogden's Sewer Design 12mo, 2 00

Richards's Cost of Food. A Study in Dietaries 12mo, 1 OO

Richards and Woodman's Air, Water, and Food from a Sani-
tary Standpoint 8vo, 2 00

Richards's Cost of Living as Modified by Sanitary Science . 12mo, 1 00

Rideal's Sewage and Bacterial Purification of Sewage 8vo, 3 50-

Turneaure and Russell's Public Water-supplies «• 8vo, 5 00

Whipple's Microscopy of Drinking-water 8vo, 3 50

Woodhull's Notes on Military Hygiene 16mo, 1 5Q

MISCELLANEOUS.

Barker's Deep-sea Soundings 8vo, 2 00

Emmons's Geological Guide-book of the Rocky Mountain Ex-
cursion of the International Congress of Geologists.

Large 8vo, 1 50

FerreFs Popular Treatise on the Winds 8vo, 4 00

Haines's American Railway Management 12mo, 2 50

Mott's Composition, Digestibility, and Nutritive Value of Food.

Mounted chart, 1 25

" Fallacy of the Present Theory of Sound 16ma, 1 00

Ricketts's History of Rensselaer Polytechnic Institute, 1824-

1894 Small 8vo, 3 00

Rotherham's Emphasised New Testament Large 8vo, 2 00

" Critical Emphasised New Testament 12mo, 1 50

Steel's Treatise on the Diseases of the Dog 8vo, 3 50

Totten's Important Question in Metrology 8vo, 2 5Q

The World's Columbian Exposition of 1893 4to, 1 00

Worcester and Atkinson. Small Hospitals, Establishment and
Maintenance, and Suggestions for Hospital Architecture,

with Plans for a Small Hospital 12mo, 1 25-

HEBREW AND CHALDEE TEXT-BOOKS.

Green's Grammar of the Hebrew Language 8vo, 3 00

" Elementary Hebrew Grammar 12mo, 1 25

" Hebrew Chrestomathy 8vo, 2 00

Gesenius's Hebrew and Chaldee Lexicon to the Old Testament

Scriptures. (Tregelles.) Small 4to, half morocco, 5 00

Letteris's Hebrew Bible 8vo, 2 25

YC 32865

785375

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UNIVERSITY OF CALIFORNIA LIBRARY

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Full text of "A text-book of important minerals and rocks. With tables for the determination of minerals"

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