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UNIVERSITY OF CALIFORNIA.

^ c cessions No. <3^- ^ Shelf No.

APPLETONS'
SCIENCE TEXT-BOOKS

APPLIED GEOLOGY.

APPLETONS' SCIENCE TEXT-BOOKS.

The following works of this new series will be im-
mediately issued ; others are to follow :

The Elements of Chemistry.

BY PROF. F. W. CLARKE,
Chemist of the United States Geological Survey.

The Essentials of
Anatomy, Physiology, and Hygiene.

BY ROGER S. TRACY, M. D.,

Author of " Handbook of Sanitary Information for Householders,"
Sanitary Inspector of the New York City Health Department.

A Compend of Geology.

BY JOSEPH LE CONTE,

Professor of Geology and Natural History in the University of
California ; author of " Elements of Geology," etc.

Elements of Zoology.

BY C. F. HOLDER,

Fellow of the New York Academy of Sciences, Corresponding
Member of the Linnaean Society, etc. ;

AND J. B. HOLDER, M. D.,

Curator of Zoology of American Museum of Natural History,
Central Park, New York.

Descriptive Botany.

BY ELIZA A. YOUMANS.

Applied Geology.

BY SAMUEL G. WILLIAMS,
Professor of General and Economic Geology in Cornell University.

jftcinite fat-0oks.

APPLIED GEOLOGY.

A TREA TISE

ON THE

INDUSTRIAL RELATIONS OF GEOLOGICAL STRUCTURE;

AND ON THE

NATURE, OCCURRENCE, AND USES OF SUBSTANCES
DERIVED FROM GEOLOGICAL SOURCES.

SAMUEL G. WILLIAMS,

PROFESSOR OF GENERAL AND ECONOMIC GEOLOGY
IN CORNELL UNIVERSITY.

NEW YORK:
D. APPLETON AND COMPANY.

I, 3, AND 5 BOND STREET.
1886.

'N/

PREFACE.

So far as the author of this book has observed,
no work has yet been published in this country
which aims to give a connected and systematic
view of the applications of geology to the various
uses of mankind. A number of European and
American treatises have appeared which limit
themselves to special departments of applied geolo-
gy, some of them discussing the modes of occur-
rence and distribution of metallic ores or mineral
fuels ; others treating of agriculture in its geologi-
cal aspects, or dealing with the geological materials
of chemical industries, or devoting themselves to
building and ornamental stones, to mortars, or to
gems. The work of D'Orbigny and Gente on ge-
ology applied to the arts and to agriculture, pub-
lished more than a quarter of a century ago, is not
only in a foreign language, but is now obviously in-
complete ; and the excellent treatise of Dr. Page,
which reviews the entire field of applied geology,
is naturally too much devoted to English and Euro-

vi PREFACE.

pean materials and sources of supply to be wholly
satisfactory to the American student.

Meanwhile an immense amount of work has
been done in revealing the geological structure of
the American Continent, and in making known its
rich and varied resources — a work in which many
independent investigators and explorers have added
much of value to the information gained by the
various State and national surveys. The knowledge
thus acquired of the existence, the nature, the
abundance, and the distribution of substances of
practical utility, as well as of the important relations
which are sustained by geological structure to hu-
man well-being and to the successful pursuit of
many important callings, is scattered so widely in
geological reports, in scientific and technical jour-
nals, and in the transactions of learned associations,
as to be in a great measure inaccessible to the stu-
dent and the practical man, unless a large library
is at hand and abundant leisure to consult it. It
seems evident, therefore, that there is need of a
treatise such as this aims to be, which, avoiding
minute detail, shall give a systematic and compre-
hensive account of the most important relations
which geology sustains to human interests.

This book is written most largely from an
American stand-point, yet care has been taken, in
the case of all important substances, to give the
chief foreign as well as the domestic sources

PREFACE. vii

whence they may be obtained, since those who
may, it is hoped, consult its pages for business pur-
poses, will naturally desire to know both where to
look for their supplies and whence their sharpest
competition is likely to come. With this view,
also, tables of the annual production of many lead-
ing minerals have been carefully compiled from the
most recent attainable data, and for these the excel-
lent tables published by the " Engineering and
Mining Journal " have furnished the largest part of
the materials.

A work of this kind is in its very nature a dis-
cussion and arrangement of materials derived from
various sources, and verified, so far as is practicable,
by personal observation and inquiry. The author
has endeavored to use the rich materials afforded
to him with proper discrimination. If somewhat
more space has been given to the chapters on " Agri-
culture," on " Materials of Construction,'' on " Min-
eral Fuels," and on "Ore Deposits" than to other
topics, it will probably be conceded that the wide-
reaching and important interests to which they relate
will fully warrant this greater fullness of treatment.
Where the works from which information has been
most largely obtained were likely to be within the
reach of those persons for whom this book is chiefly
intended, they have been mentioned in the lists of
works of reference appended to many of the chap-
ters. This has necessarily precluded any specific

viii PREFACE.

mention of many valuable papers published in scien-
tific journals and in the " Transactions of the Ameri-
can Institute of Mining Engineers," to which this
book is indebted for many items of interest. For
the arrangement of the seemingly heterogeneous
materials of some of the later chapters, useful hints
were derived from the " Geology of Canada," 1863,
and from some features in the classification of the
economic collection of the Ecole des Mines in
Paris. The author wishes also to acknowledge his
indebtedness to the kindred works of D'Orbigny
and Gente, and of Dr. Page, for many important
suggestions, and to the first-named work especially
for valuable aid in the preparation of the chapter
on agriculture.

CORNELL UNIVERSITY, October i, 1885.

ANALYSIS OF CONTENTS.

CHAPTER I.

PAGE

INTRODUCTION — ROCK-FORMING MINERALS — CLASSIFICATION . i

Quartz, feldspars, micas, hornblende, pyroxene, calcite, dolo-
mite, talc, chlorite, serpentine, clay— Classification of rocks-
Sedimentary rocks and consolidation — Crystalline rocks and their
structure— Tables of classification and means of consolidation.—
Structure and texture of rocks.

CHAPTER II.

DESCRIPTION OF ROCKS 15

Mechanical sediments— Chemical sediments — Organic sedi-
ments— Metamorphic rocks — Igneous rocks — Key for proximate
determination of rocks.

CHAPTER III.
ARRANGEMENT OF ROCK-MASSES . . . . . .27

Stratified and definitions — Unstratified — Included or vein-like
— Relative age of rocks — Table of ages and periods.

CHAPTER IV.
ECONOMIC RELATIONS OF GEOLOGICAL STRUCTURE ... 44

Economic geology defined and illustrated — Accessibility de-
pendent on dip, faults, uplifts — Facility of extraction — Expense
of excavation and tunneling — Foundations of structures— Water
supply — Springs — Wells — Artesian wells — Drainage.

CHAPTER V.
MATERIALS OF CONSTRUCTION ....... 66

Building-stones—Properties of— Strength— Table of strength
— Durability — Beauty — Ease of working — Selection of building-

x ANALYSIS OF CONTENTS.

PAGE

stones — North American building-stones — Geological positions
and distribution — Granitic — Marble and slate — Sandstones — Lime-
stones— Brick, terra-cotta, and drain-pipes — Materials for mortar
and cement.

CHAPTER VI.
RELATIONS OF GEOLOGY TO AGRICULTURE . . . . 101

Soils, origin of — Ingredients — Nature and amelioration — Table
of ash analyses — Composition of soils — Fertilization— Geological
fertilizers — Drainage and subsoils.

CHAPTER VII.

RELATIONS OF GEOLOGY TO HEALTH 129

Water supply of households and communities — Drainage of
dwellings, cities, and districts.

CHAPTER VIII.

MINERAL FUELS 135

Coals, classification — Analyses of twenty-two — Geological as-
sociations— Geological horizons — American coal-fields — Foreign
coal-fields — Impurities in coals — Fuel-value of coals— Adaptation
to special uses— Peat— Coal product of 1881.

CHAPTER IX.
GEOLOGICAL MATERIALS FOR ILLUMINATION . . . .165

Petroleum— Mode of occurrence— Geological horizons— Re-
gions— Mode of exploitation — Bituminous shales — Natural gas —
Ozocerite.

CHAPTER X.
MODE OF OCCURRENCE OF METALLIFEROUS DEPOSITS . . 183

Metallic ores— Ore associations and gangues— Structure of ore
deposits — Beds and placers — Impregnations — Mass deposits —
Veins of segregation— Fissure veins— Origin of fissures and con-
tents— Arrangement of contents— Positions relative to country
rock— Disturbances of deposits— Surface changes— General distri-
bution—Prospecting—Value, on what dependent — Erroneous
ideas regarding ore deposits.

CHAPTER XI.
224

Ores — Mode of occurrence— Geological horizons and localities
—Production— Uses.

ANALYSIS OF CONTENTS. xi

CHAPTER XII.

PAGE

COPPER 231

Ores — Mode of occurrence— Distribution, geological and topo-
graphic— Chief foreign localities — Production in 1882 — Uses.

CHAPTER XIII.
LEAD AND ZINC 241

Ores of lead — Nature of deposits and geological horizons —
American centers of production — Foreign regions— Production —
Uses— Zinc ores — Mode of occurrence — American localities — For-
eign centers — Production—Uses.

CHAPTER XIV.

TIN AND MERCURY • . 254

Tin ore — Mode of occurrence — Localities — Production and use
— Ore of mercury — Form of deposits — Three regions of — Produc-
tion of 1882— Uses.

CHAPTER XV.
SILVER 262

Ores — Forms of deposit — American silver regions — Table of
production — Foreign silver regions — Table of world's product —
Uses.

CHAPTER XVI.
GOLD . .- . . . . ' 273

Associations — Mode of occurrence — Regions of gold produc-
tion— Tables of United States product, and of that of the world —
Uses of gold — Table of gold values — Table of uses of gold and
silver — Extraction of gold.

CHAPTER XVII.

PLATINUM AND OTHER METALS 284

Platinum — Nickel — Cobalt — Antimony — Bismuth — Magnesium
— Aluminium — Chromium — Manganese — Arsenic — Iridium —
Tungsten.

CHAPTER XVIII.
SUBSTANCES ADAPTED TO CHEMICAL MANUFACTURES OR USE . 296

Pyrites— Sulphur— Salt — Potash and soda — Borax— Alum-
Magnesia— Strontia — Titanium.

xii ANALYSIS OF CONTENTS.

CHAPTER XIX.

PAGE

FICTILE MATERIALS 319

Potter's clay — Table of analyses — Properties — Origin — Locali-
ties— Pottery mixtures and glazes — Composition of glass — Glass-
sand — Granulite— Coloring materials.

CHAPTER XX.

REFRACTORY SUBSTANCES . 334

Fire-clays — Analyses — Geological occurrence— Dinas bricks —
Canister — Fire-stones — Floating brick — Graphite — Lime and
Magnesia — Soapstone — Mica — Asbestus.

CHAPTER XXI.

MATERIALS OF PHYSICAL APPLICATION 347

For roads and walks — Abrasives: Grindstones, whetstones,
millstones, bort, corundum and emery, sand, pumice and tripoli
— Graphic materials: Graphite, chalk, etc., lithographic lime-
stone— Pigments : Whiting, ochre, umber, barytes — Lubricators : '
Graphite, petroleum, talc, felsite — Molding-sand.

CHAPTER XXII.

ORNAMENTAL STONES AND GEMS 365

Quartz — Amethyst — Agates — Moss-agate — Onyx — Jasper-
Feldspar — Nephrite — Lapis lazuli — Malachite — Fluorite — Jet-
Amber — Marbles — Onyx marble — Alabaster — Verd-antique mar-
ble— Porphyry. Gems : Diamond, corundum, spinel, topaz, beryl,
zircon, garnet, tourmaline, hiddenite, turquoise, opal.

APPLIED GEOLOGY.

CHAPTER I.

INTRODUCTION — ROCK-FORMING MINERALS — CLASSIFICA-
TION.

THE science of geology has both a theoretical and
a practical side. Theoretically, it aims at an exhaustive
study of the phenomena presented by the earth's crust,
together with the order in time in which they originated,
and the forces to whose combined or successive action
they are due. It investigates the composition, the struct-
ure, the origin, and the arrangement of the earth's rocky
masses. It strives to refer the present phenomena of the
earth's crust to their appropriate causes. It reconstructs
the history of the earth and of its successive inhabitants,
using structure as its guide, and the present action of the
unchanging forces of nature as its interpreter.

On the practical side, geology uses the knowledge of
the earth's structure, and of the mode of occurrence and
properties of its various products, to subserve human
needs and promote human enjoyment. It guides the
architect and the builder in the selection of fitting mate-
rials for construction — good building-stones, mortars, ce-
ments, and sands. It reveals to the agriculturist the ori-
gin of his soils, and points him to the cheapest and most

2 APPLIED GEOLOGY.

effective means for correcting their defects. It teaches
the civil engineer that the feasibility and expense of most
of his important undertakings, the obstacles that he must
overcome, and the aids of which he may avail himself,
will depend in large measure on the geological structure
of the region in which he must operate ; and that he
needs to take this into careful consideration, if he would
guard against ruinous disasters, or almost equally ruinous
miscalculations as to expense. It furnishes to the mining
engineer the only available guide in his arduous calling,
teaching him the nature and the modes of occurrence of
those valuable substances for which he must seek, the
laws to which they are subjected, and the irregularities
and dislocations to which they are liable ; and supplying
him with those general principles, by applying which, he
may make the technical experience gained in any one lo-
cality available under other and widely different circum-
stances. It aids the sanitarian in securing the two most
subtile yet essential conditions of public health — pure air
and wholesome water — both of which depend largely on
circumstances purely geological.

Not only does practical geology hold such intimate
relations with these very important interests, but, more-
over, when we consider how large a proportion of the sub-
stances which civilized man utilizes for the supply of his
multifarious wants is drawn from the bosom of the earth,
we shall see how wide-reaching and vital are its connec-
tions with the very sources of human progress. Among
these substances are the fuels that we burn ; the materials
that we use for illumination ; the salt with which we pre-
serve or season our food, and which becomes the basis of
vast manufactures, some of whose products reach every
family ; the clays and sands that we fabricate into myriads
of useful and ornamental forms, a number of which are
found in every household, even the humblest ; the ores
that we smelt to provide ourselves with those implements

ROCK-FORMING MINERALS.

by whose ever-widening use we are daily exten<
mastery over the blind forces of nature ; and, finally, but'
by no means least, those substances by which a cultured
taste seeks for itself a refined pleasure — brilliant pigments,
sparkling gems for jewelry, and handsome stones for do-
mestic and architectural adornment. The withdrawal of
any one of these classes of materials would seriously crip-
ple human resources, and the lack of some of them would
have made human advancement very difficult, if not im-
possible ; for the stages of man's progress are well marked
by the character of his pottery, and, better, by the nature
and material of his implements.

It is but natural that a science which touches so vitally
the interests of nearly all classes should attract the atten-
tion of enlightened governments ; and we accordingly
find that most civilized states have carried on to some
extent geological surveys, which, while primarily revealing
the geological structure of their domains, have also care-
fully sought out their various mineral resources. The pub-
lications of these surveys, giving an authoritative statement
of the localities where valuable substances might be found,
have naturally attracted capital to the development of
such means of wealth, and have, doubtless, repaid mani-
fold their cost by the increase in the taxable property of
the communities that have carried them on. The two
States of Ohio and Illinois published reports of their re-
sources, beginning the one in 1870 and the other in 1866.
The coal-trade alone of these two States increased from
two and a half million tons each in 1870 to more than
nine million tons each in 1882 ; and this industry in Illi-
nois gave employment to 19,400 men and $8,230,000 capi-
tal. There is no good reason to doubt that this great
increase in the coal-trade of those States was due in large
measure to the reliable information furnished by their
surveys.

Incidentally, also, such surveys have been of great

4 APPLIED GEOLOGY.

service in discouraging misdirected and expensive explo-
rations after substances not likely to be found in certain
localities ; for, second only in importance to the knowl-
edge of what we may fairly expect to find in a given place
is the certainty of what we ought not to expect to find.
Large sums have been expended in New York by men
unacquainted with its geological structure, in a futile
search for coal in certain black, slaty rocks, holding geo-
logical positions such as have never yet furnished coal,
nor are ever likely to do so. Any man would show him-
self ignorant indeed who should now undertake a search
for coal in New York.

From what has already been said, it will be evident
that at least an elementary knowledge of the earth's geo-
logical structure is essential as a guide in the intelligent
prosecution of many great branches of industry. It will
be necessary for our purpose, therefore, first to examine
the most essential points of geological structure, and after-
ward to show their application to the various arts, draw-
ing our materials as largely as possible from American
sources.

Rocks : their Composition and Classification.

Geology deals with the rocks which form the earth's
framework ; and what is most essential to be known about
rocks for our present purpose is — (i) their composition, i.e.,
the mineral substances which enter into them and impart
to them most of their properties; (2) their texture and
structure, or the characteristics which distinguish them
both as rock-individuals and as rock-masses ; (3) their ori-
gin, or the agencies through which they assumed their
present form ; (4) their mode of arrangement ; and (5) the
order in which they occur.

Rock-Forming Minerals. — Some careful examina-
tion of the rocks most commonly met with will prepare
the observer to admit that all rocks, whatever their origin,

ROCK-FORMING MINERALS. 5

are composed of mineral species ; and, furthermore, that
the minerals which play the chief part in their composi-
tion, and which most largely condition their use and dura-
bility, are comparatively few in number. These minerals,
in particles varying greatly in size and regularity of form,
aggregated in the most variable proportions, and consoli-
dated by many different agencies to the most widely differ-
ing degrees of firmness, from mere incoherent masses of
sand, to the hardest quartzite and the toughest trap, make
up the chief bulk of the most important rocks of the
globe. Ready acquaintance with them in their smallest
discernible particles, and by their most obvious and easily-
tested properties, is highly essential to the practical geolo-
gist. Chief among such minerals is quartz, with its most
widely-disseminated compounds, viz. : the varieties of
feldspar, mica, hornblende, and pyroxene, to which may
be added talc, chlorite, and serpentine. Calcite and dolo-
mite are the essential components of the various kinds of
limestone and marble ; while pyrite, though not largely
present in rocks, should be known because of the injuri-
ous manner in which it affects their characters. The im-
portant ores and other minerals of economic use will be
considered in other connections.

For a complete knowledge of these minerals, and others
that will be mentioned in this treatise, the student should
study the minerals themselves — all easy to be obtained —
with the aid of some good treatise on mineralogy, Dana's
" Manual of Mineralogy " being the best. The properties
to which especial attention should be directed are, color
and luster, hardness, cleavage and fracture, behavior with
acids, and sometimes fusibility.

Quartz is readily distinguished by its glassy luster, its
hardness, so great as not to be scratched by a knife, and
by the fact that its fracture gives never flat but always
curved surfaces (conch oidal fracture). It will scratch all
the other minerals named above, being 7 on a scale of

6 APPLIED GEOLOGY.

hardness beginning with talc, i, easily impressed with the
finger-nail, and ending with diamond, 10.

The hardest of the remaining minerals named as chief
components of rocks, the feldspars, can be scratched with
considerable difficulty by a knife, and their hardness is
counted 6. Besides this, the feldspars can be split with
flat, shining surfaces — cleavage — in two directions, making
a right angle with each other in orthoclase, the most com-
mon kind, and in the other two important varieties, oligo-
clase and labradorite, varying but a few degrees from a
right angle. The last two, in a good light, usually show
on the face of easiest cleavage fine parallel lines, while
orthoclase does not. The color of orthoclase and oligo-
clase varies from white to light red, while labradorite is
usually gray or brown, with a beautiful internal reflection
from smooth surfaces. Their luster differs somewhat from
that of quartz, inclining to pearly. Their slightly inferior
hardness and their flat cleavage surfaces usually make them
easily distinguishable from quartz ; but if any doubt still
remains, a thin, pointed splinter should be strongly heated
with the blow-pipe. Any of the feldspars can be fused
with more or less difficulty, while quartz can not.

The micas are readily distinguished by their very easy
cleavage into thin, elastic, shining leaves. Muscovite mica
is usually of light to brownish silvery colors, biotite black,
and phlogopite of bronze-color. All are easily scratched
with a knife.

Pyroxene, of which augite is the most abundant
variety, and hornblende, as they are commonly found in
rocks, are black, brown, or dark-green minerals, though
some varieties are lighter green and white, a little more
easily scratched than feldspar — their hardness being about
5.5 — and more easily fused. Both cleave in two directions,
making in pyroxene a little less than a right angle, and in
hornblende a very obtuse angle of 124° 30'. Hence, when
the angle of cleavage can be seen, the two minerals can be

ROCK-FORMING MINERALS. 7

easily distinguished, otherwise not. It is helpful, however,
to note that the cleavage of hornblende is easier than that
of pyroxene, hence gives usually more complete surfaces
and brighter luster ; also that hornblende is frequently
found associated in rocks with quartz and orthoclase,
while augite, the most common form of pyroxene, is rarely
so associated. Both are heavy minerals, and give more
than usual weight to rocks in which they occur abun-
dantly.

Calcite and dolomite are easily known by their ready
cleavage in three directions, when crystallized, giving rise
to a six - sided oblique - angled figure ; by being easily
cut with a knife — hardness 3 to 4 ; and by effervescing
rapidly, from the escape of carbonic acid, with dilute hy-
drochloric acid. Their usual color is white. Dolomite
is a little harder and a little heavier than calcite, and
while calcite effervesces freely in cold acid, dolomite
effervesces but slightly, if at all, until the acid is heated.
Both are very important minerals, being, as has already
been said, the essential constituents of all limestones and
marbles.

Pyrite, or iron pyrites, is a mineral of metallic luster
and light-yellow or golden color, whence it is often mis-
taken for gold — hence called " fool's gold " — but is readily
distinguished from it by its great hardness, nearly equal
to that of quartz, and by its giving when heated the odor
of sulphur. It is little likely to be mistaken for any other
mineral save copper pyrites, from which it may be distin-
guished by the fact that copper pyrites is much softer
and its color is a deeper yellow.

Talc is a green, gray, or white mineral of pearly luster,
so soft as readily to be scratched by the finger-nail, greasy
to the touch, and usually of a scaly, foliated, or fibrous
texture. Its softness and its soapy feel render it easy to
be distinguished.

Chlorite, as it occurs forming a characteristic constit-

8 APPLIED GEOLOGY.

uent of rocks, is usually a dark-green earthy mineral, but
little harder than talc, and of a pearly luster when cleav-
able.

Serpentine is usually a massive though sometimes
fibrous mineral, of an oily green color, sometimes red or
nearly black, of greasy luster and slightly greasy feel, easily
scratched with a knife, its hardness being about 3, and with
a conchoid or splintery fracture.

To these materials of rocks should be added clay,
an indefinite mixture of kaolin, which is a soft, unctuous
substance resulting from the decomposition of feldspar,
with varying amounts of quartz -sand often exceedingly
fine, powdered feldspar, iron oxide, and occasionally other
substances. It is plastic when wet, shrinks on drying or
when strongly heated, and emits an earthy odor when
breathed on. The rocks into which it enters are often
described as argillaceous rocks, from the Latin name for
clay : e. g., slate is an argillaceous rock, and a limestone
containing a considerable amount of clay would be termed
an argillaceous limestone. Also the following adjective
terms are of frequent occurrence, viz. : Quartzose or sili-
cious, applied to rocks containing quartz ; calcareous, to
those containing calcite ; ferruginous, to those colored by
iron oxide — usually red, yellow, or brown ; and arenaceous,
to those containing sand.

Rocks. — The minerals here described, with occasion-
ally quite subordinate amounts of some other minerals,
make up the rocks of chief economic importance. As
constituents of rocks they are found, sometimes as crys-
tals of usually imperfect outline, sometimes in the form of
broken and worn grains, of sizes varying from those so
minute as not to be perceptible to the unaided eye, to
masses of considerable size. Hence, according to the con-
dition of the composing substances, we may distinguish
crystalline rocks and fragmental, or, as they may with
equal propriety be termed, sedimentary rocks, because de-

ROCK-FORMING MINERALS. g

posited from suspension or solution in water. The rocks
of the latter class are found always arranged in layers
or beds, and hence called stratified ; while the crystalline
rocks may occur either in beds more or less apparent, or
without any signs of a bedded structure, when they may
be termed massive. Stratified rocks, i. e., those having a
layered structure, are much the most common, and exam-
ples of them may be studied in most localities where the
rocks appear above the covering soil.

Sedimentary Rocks. — The sedimentary rocks are of
three general kinds : (i) those formed from the worn frag-
ments of pre-existing rocks, which may be called mechani-
cal sediments, e. g., sandstones and shales ; (2) those de-
posited from solution in water, or chemical sediments, as
some limestones, many quartz rocks, and probably most
beds of iron-ore ; and (3) organic sediments, those formed
from the worn and subsequently consolidated results of
vegetable and animal growth, as most limestones and coal-
beds. Beds of the second class are formed of welded and
interlocked crystals, and have a degree of solidity equal to
that of the composing mineral. Beds of the two remain-
ing classes, though sometimes found as mere incoherent
or slightly cohering masses like sand, gravel, and chalk,
have more generally been consolidated by various means
to a greater or less degree of hardness. The following
are the chief means of consolidation :

Some rocks seem to be consolidated solely by the great
and long-continued pressure of the overlying beds, caus-
ing the particles to adhere to each other, as is the case
with many shales. When, as is often the case in sand-
stones, some finely-disseminated clay is present, making the
contact among the sand-particles more complete, pressure
gives the rock a greater degree of firmness. The presence
of this clay can be detected by subsiding the finely-pow-
dered rock in water, when the clay will remain long sus-
pended, making the water turbid. A common means of

I0 APPLIED GEOLOGY.

consolidation is calcite, which has been introduced in solu-
tion, as in all sedimentary limestones and some sandstones.
Its presence as a consolidating ingredient in rocks other
than limestones can be readily detected by its efferves-
cence with dilute acids. Silica consolidates mjfciy sand-
stones and conglomerates to a very high degree of hard-
ness ; and iron oxide is also a frequent means of consoli-
dation, giving to rocks a red or yellow color. When red
or yellow sandstones are pulverized and heated for a little
time in strong hydrochloric acid, the cementing iron is
dissolved, giving a deep yellow solution, and colorless
grains of quartz remain.

Crystalline Rocks. — The crystalline rocks, other
than the relatively small amounts of chemical sediments,
are made up usually of imperfect crystals, sometimes of
one mineral, but more commonly of two or more, welded,
interlocked, or felted together to a mass as firm at least as
the softest abundant constituent, unless a prevailing direc-
tion of some readily cleavable mineral like mica, talc, or
hornblende, may dispose the rock to split more easily in
certain directions. Some of these crystalline rocks have
a more or less observable bedded character, often with
foliation or schistose structure, and are generally believed
to have once been ordinary sedimentary rocks, which, hav-
ing been rendered somewhat plastic by heated water under
enormous pressure, have crystallized in their present form.
Hence they are termed metamorphic rocks, i. e., rocks
which have been changed from their original condition.
Other crystalline rocks show no signs of bedding what-
ever, their condition being probably due to a softening or
fusion so complete as to have obliterated all traces of bed-
ding, if they ever existed. In this condition they have
often been thrust in among or through other rocks, emerg-
ing frequently at the surface. Where the subsequent cool-
ing has proceeded at a very slow rate, and usually at very
considerable depths, the resulting texture is coarsely and

ROCK-FORMING MINERALS.

obviously crystalline ; where the rate of cooling has been
relatively rapid, the crystalline texture may be so fine and
close as not to be apparent to the unaided eye, or the text-
ure may in some cases be partly or entirely glass-like, i. e.,
vitreous. Rocks of this kind are termed igneous or erup-
tive, and those obviously crystalline are also frequently
called Plutonic rocks, a term which implies the opinion
that they were consolidated at great depths, and that our
present opportunities for becoming acquainted with them
are due to very great subsequent changes in the earth, in
consequence of which they have become surface-rocks.

To give a connected view of what has just been said,
a tabulated summary of rocks in general is here presented,
classified according to origin, with their structure as rock-
masses and the usual condition of their materials :

Classification on Origin.

Structure.

Condition of Materials.

C Mechanical,
Sedimentary \ Chemical,
I Organic.
Metamorphic.
Igneous.

Stratified.

Stratified.
Massive.

Fragmentary, sometimes
crystalline.

Crystalline.
Crystalline or vitreous.

Means of Consolidation :

1. Pressure.

2. Clay and pressure.

3. Silica.

4. Calcite.

5. Iron oxides.

6. Welding, interlocking, or felting of crystals.

Structure and Texture of Rocks. — By the struct-
ure of rocks is meant those characters which distinguish
them as rock-masses, and which are usually best displayed
on the large scale.

Most important of structural characters is stratifica-
tion, which is the arrangement of rock-masses in tolerably

12 APPLIED GEOLOGY.

parallel sheets or layers, varying in thickness from the
fraction of an inch to several feet, and separating readily
from each other. Layers of the same kind of rock lying
together form a stratum, and alternations of different kinds
of rock produce strata (plural of stratum). A stratum of
some valuable material, e. g., coal, is frequently termed a
seam or bed. Stratified rocks were undoubtedly formed
in all usual cases by deposition of their materials from
water, in precisely the same way that successive layers of
mud and sand are being deposited now in seas, lakes, and
rivers ; and it is altogether probable that the division into
layers is due to some considerable pause in the act of depo-
sition, whereby the lower layer became somewhat com-
pacted before the succeeding one was deposited ; while
the succession of strata marks changes in the conditions
of deposit by which materials of different kinds came to
be laid down.

The massive structure is contradistinguished from the
stratified, and belongs to igneous rocks, or to those which
have been so greatly changed from their original condi-
tion as to have lost all signs of bedding. The term mass-
ive is also used sometimes in contradistinction from lami-
nation. Lamination is where rocks reveal the thin succes-
sive layers of which they are made up, either by some
slight differences of color or texture in the several layers,
or by splitting more readily on certain planes, usually par-
allel to the bedding. This structural character is a com-
mon one in sandstones, especially where they are argilla-
ceous, and is occasionally seen in limestones. An excess
of lamination in highly argillaceous rocks, causing them
to split into thin, irregular, fragile slabs, constitutes the
shaly structure.

Foliation, or the schistose structure, is a character of
metamorphic crystalline rocks, analogous to lamination in
the sedimentary series, and is due to the arrangement of
the crystalline constituents in more or less definite planes,

ROCK-FORMING MINERALS.

which often, no doubt, if not always, correspond
nal planes of lamination, since these are likely to be the
planes of easiest penetration and circulation for fluids.
The slaty structure is one which belongs to argillaceous
rocks that have been doubled up into folds, and so changed
by intense pressure as to develop a tendency to cleave
into hard, even slabs, in a direction at right angles to the
pressure, and corresponding with the direction of the
folds. The planes of cleavage rarely correspond with the
original planes of lamination, though they may occasion-
ally do so.

Joints are divisional planes in rocks, usually but not
always nearly vertical, which divide the rocks of many
regions into blocks that separate somewhat readily at these
planes. These blocks, in regions of jointed structure,
vary in width from an inch, or even less, to many feet, the
main joints forming the faces of the cliffs and the back
walls of the quarries ; and where, as is frequently the
case, there are two series of joints, cutting each other at
nearly right angles, the weathered faces of the cliffs pre-
sent a singular resemblance to regular piles of masonry.
This structure is not confined to any one of the great
classes of rocks that have been named, but may be found
in all of them, occasionally even giving to massive rocks
a false appearance of bedding. Practically considered,
while the jointed structure greatly facilitates the operation
of the quarryman, it also strictly limits the dimensions of
the blocks that can be obtained.

The columnar structure often seen in volcanic rocks,
especially the basalts, seems to be a variety of the jointed
structure, in which, by the intersection of several jointing
planes, the rock is divided into a series of rude pillars
which are at right angles to the original cooling surfaces
of the rock.

The concretionary structure is one which is displayed
in some rocks by the collection of some mineral, notably

I4 APPLIED GEOLOGY.

silica, calcite, pyrite, or iron carbonate, into spherical,
spheroidal, or irregular forms, e. g., the flinty nodules in
chalk and limestone, the silicious balls in some sandstones,
the calcareous and pyritous masses in some clay rocks, and
the kidney-shaped masses of clay iron-stone.

By the texture of rocks is meant the internal arrange-
ment of their constituents. The granular texture is dis-
played by rocks which are composed of worn grains or
irregular crystals. These grains or crystals may vary
from those of considerable size, giving a coarse-grained
texture, to very minute ones, giving rise to the compact
texture, as in many sedimentary limestones, and to the
aphanitic or crypto-crystallim texture, as in some igneous
rocks in which the really crystalline texture is revealed
only by the microscope.

The term granitoid is applied to thoroughly crystalline
rocks whose crystals are of approximately equal size, as
in granite ; while the term porphyritic describes those
which contain distinct crystals, notably of feldspar, im-
bedded usually in a very fine-grained base or ground-mass.
The vitreous or glassy texture resembles artificial glass,
and is found only in some eruptive rocks. The terms
porous, fibrous, earthy, and vesicular, as applied to text-
ure, hardly need explanation. Some eruptive rocks, origi-
nally vesicular, have had their rounded cavities subse-
quently filled by various minerals, giving rise to a vari-
ety of texture called the amygdaloidal, from the resem-
blance of many of the filled spaces to the almond, Latin
amygdala.

CHAPTER II.

DESCRIPTION OF ROCKS.

Mechanical Sediments. — Sand is an unconsoli-
dated mass of fine, worn grains of the harder minerals and
crystalline rocks, in which quartz usually plays by far the
largest and often the almost exclusive part, since it is the
hardest and most enduring of the ordinary rock-forming
minerals. Where the worn fragments range from the size
of a pea to that of an egg, it is called gravel, still coarser
gravel being sometimes termed shingle. Most sand con-
tains particles of magnetic iron- ore, which can be de-
tected by their clinging to a magnet. Sand, consolidated
in any way, forms sandstone. In some sandstones
pressure seems to be the sole consolidating agent, though
doubtless a minute amount of silica cements the points
of contact of the granules, producing a porous and
often friable rock. The presence of a small amount of
clay, forming a film which coats the grains of sand, or
of a larger amount partially imbedding them, makes a
firmer rock, often highly laminated — an argillaceous sand-
stone. Iron oxide, usually mingled more or less with clay,
is a somewhat common cement, forming a red or yellow
sandstone. When silica is the cementing material filling
the spaces among the grains, it makes an exceedingly
hard rock called a silicious sandstone ; or where it oc-
curs, as it usually does, among metamorphic rocks, it is
called quartzite. Calcite is not often found as the chief

l6 APPLIED GEOLOGY.

cementing material of sandstones ; but when it is present,
it is readily recognized by its effervescence with acids.
A sandstone which works equally well in all directions,
without a tendency to split, is often called freestone — a
name which is also sometimes applied to other rocks of
like character. A thin-bedded laminated sandstone is a
flag-stone. Coarse, rough-textured sandstones are often
called grits — a term, however, not very definitely used.

A conglomerate, sometimes called pudding-stone, is
formed of rounded pebbles, from the size of a pea to a
foot or more in diameter, consolidated in any way, and
with the spaces filled usually with cemented sand. Where
the pebbles, instead of being rounded, are angular, the
rock is called a breccia.

A shale is a highly laminated argillaceous rock, con-
solidated often by mere pressure, and so returning to mud
when exposed for some time to the weather. Where it
contains a considerable proportion of sand, it becomes an
arenaceous shale, and so may graduate into an argillaceous
sandstone.

Chemical Sediments. — These rocks deposited from
solution in water by evaporation or cooling of the water,
or by dissipation of the chemical agent that held them
dissolved, although forming no great proportional amount
of the rocks of the earth, still furnish several substances of
great economical importance.

Calcareous deposits from water in which lime is held
in solution by carbonic acid, when porous and friable,
often incrusting twigs and leaves, are called calcareous
tufa ; when forming pendants from the roofs of caverns,
and incrustations on their floors, are called stalactites and
stalagmites ; when forming compact beds, are named trav-
ertine, which, when banded with various colors, becomes
onyx marble ; and when composed largely of rounded
concretionary grains, little larger than a mustard-seed, are
termed oolites.

DESCRIPTION OF ROCKS. ij

Gypsum is a sulphate of lime, which, when crystalline,
is much softer than calcite, being easily scratched by the fin-
ger-nail, and cleaves easily in one direction, forming trans-
parent, inelastic plates which quickly whiten when held in
a flame. It forms considerable beds, or lenticular masses,
which in some cases have been deposited by evaporation
of the water that held the gypsum dissolved, and in
others have been formed by a change of ordinary lime-
stones through infiltration of sulphuric acid from sulphu-
retted springs. In the latter case, the gypsum forms a
soft, earthy rock, usually of a gray color. When ground
fine and heated, gypsum gives off much water, and leaves
a powder that will set with water.

Salt occurs in beds or masses, sometimes of enormous
thickness, which have doubtless been formed by the evapo-
ration of inclosed bodies of sea-water. It is usually asso-
ciated with beds of gypsum and of anhydrite — a mineral
like gypsum, but containing no water.

The waters of some springs, especially in regions of
volcanic disturbance, deposit silica, sometimes on the sur-
face as hard, porous incrustations, called silicious sinter, as
about hot springs and geysers; sometimes filling fissures
in other rocks, forming common vein-stones that are con-
nected with many valuable ore-deposits.

Iron-ores, which occur usually as beds associated with
various other rocks, doubtless owe their origin to chemical
deposition. Siderite, i. e., iron carbonate or spathic iron,
occurs crystallized in the same form and with the same
cleavage as calcite, but is somewhat harder and of con-
siderably greater comparative weight — specific gravity —
besides being of a brownish color ; also, when heated in
a test-tube, it turns black and becomes magnetic. When
it occurs in kidney-shaped concretions, it is termed kid-
ney-ore or spherosiderite j when mixed with clay, it is clay
iron-stone ; and when forming a black, bituminous, shaly
mass, it is called black-band.

1 8 APPLIED GEOLOGY.

Limonite is an iron oxide containing some water, and
forms masses of a fibrous or earthy texture, and of a color
varying from brown to black; but its powder and the
streak which it makes on an unglazed porcelain surface
are of a dull yellow color. When heated in a test-tube,
it yields steam which condenses in the upper part of the
tube, and becomes magnetic, though not so before heating.

Hematite has the composition of limonite, but without
water, and forms beds of a red, steel-gray, or black color,
and of a texture varying from earthy or compact, to those
mica-like, or to thin, tabular, very brilliant crystals. The
streak and powder are of a dark cherry-red.

Magnetite is black, has a black streak and powder,
and attracts the magnet strongly. It forms a crystalline,
granular, or sometimes compact rock, of great weight, and
is easily known by its magnetism and its black powder.
The last three iron-ores form very heavy rocks, and, when
crystalline or compact, are of about the hardness of feld-
spar, being scratched with some difficulty by a knife.

Organic Sediments. — These rocks, formed of the
hard parts of very minute organisms, or of the remains of
any organic growth ground up or macerated, and after-
ward consolidated either by pressure or by partial solu-
tion of their own substance, embrace all the coal-beds of
the world, and all extensive deposits of limestone, besides
those peculiar silicious deposits called tripoli.

The limestones, usually composed mainly of calcite,
form beds of a drab, gray or blue color, sometimes red
or black, and of a texture varying from earthy to sub-
crystalline or compact, which last are the most common.
These rocks almost always contain a greater or less quan-
tity of some impurity — iron, giving them a red color ; car-
bonaceous matter, making them dark ; or clay and silica,
which are often found in such amounts that when the rock
is burned for lime it will not slack with water, but when
ground and mixed into mortar will set under water to a

DESCRIPTION OF ROCKS. ig

mass of great hardness, and is hence called hydraulic lime.
Many limestones, besides calcite, contain also a consider-
able proportion of dolomite, or are made up almost wholly
of dolomite. Such are called magnesian limestones or
dolomites. Chalk is a very soft, earthy limestone, usually
white, made up of the calcareous skeletons of very minute
organisms. The limestones, when burned properly, lose
their carbonic acid and become quicklime, which, on ap-
plication of water, falls into a powder, i. e., slakes, with the
evolution of considerable heat, which is greater in the
case of the calcitic than in that of the dolomitic limes.
Hence the former are called " hot limes," while the mag-
nesian are termed " cool limes."

The limestones that are found associated with crystal-
line rocks have been metamorphosed by the action of heat,
are of prevailing white or light colors, though often clouded
or tinted by impurities, and are of a crystalline granular
texture ; sometimes of very fine grain, as in the best stat-
uary and architectural marbles, sometimes coarse-grained.
Any limestone which is susceptible of a fine polish is usu-
ally called a marble^ the crystalline limestones furnishing
probably the largest proportion of these. The crystalline
limestones frequently contain certain disseminated miner-
als, forming mixtures, some of which are prized for orna-
mental purposes, like the verd-antique marble or ophiolite
formed by the intermingling of calcite and serpentine.

Mineral coals are formed of former vegetable growths
which have been more or less macerated, subjected to a
peculiar, partially smothered decomposition, and consoli-
dated by the pressure of the superincumbent rocks. A
rude but convenient commercial classification of them is
made according to the amount of volatile combustible mat-
ter that they contain. Those that contain little volatile
matter, and hence are hard and lustrous, kindling with dif-
ficulty, and burning with but slight blue flame, no smoke,
and intense heat, are called anthracites. Semi-bituminous

20 APPLIED GEOLOGY.

coals are those that contain from ten to about eighteen or
twenty per cent of volatile matter, and bituminous coals
have a still higher percentage than this. Both these latter
kinds kindle easily, and burn with a yellow flame and
much smoke. Some of these coals soften while burning,
and the pieces fuse together into a mass, which needs to
be broken up to admit of ready burning — these are called
caking coals ; others do not soften while burning — such
are the non-caking coals, named, from various qualities,
splint or block coal, cherry coal, and cannel. The coals
will be more fully considered in another place, and are
mentioned here merely in their place as organic sedi-
ments.

Metamorphic or Stratified Crystalline Rocks.
— A brief description only can here be given of the most
widely disseminated and important species of metamor-
phic as also of massive crystalline rocks. Many of the
varieties to which distinctive names are given by litholo-
gists are not frequently met with, and are of little practical
importance ; it will not be expedient, therefore, to burden
the attention of the student with them in a treatise like
this.

As has already been said, the metamorphic rocks are
those which are thought once to have been ordinary sedi-
mentary rocks, and to owe their present crystalline con-
dition to a more or less profound change caused by the
agency of heat and moisture. They still show their origi-
nal bedded structure with more or less distinctness, but
the beds are invariably much disturbed, thrown out of
their original nearly horizontal position, bent and folded,
testifying to the action of enormous mechanical forces.

The most widely-diffused and most profoundly changed
of these is gneiss, a foliated, crystalline compound of quartz,
feldspar — usually orthoclase — and mica, the foliated ar-
rangement of the minerals, sometimes very perfect, giving
the rock a highly schistose structure, sometimes so indis-

DESCRIPTION OF ROCKS. 2I

tinct as to make the mass difficult to distinguish from gran-
ite, which has the same composition, and which differs from
gneiss only in the absence of all traces of bedding. Indeed,
some masses of gneiss are believed by careful observers to
be of eiuptive origin, while it can hardly be doubted that
some granite is only the extreme stage of metamorphism
of rocks which once were stratified. Where hornblende
replaces the mica of gneiss in whole or in part, we have
hornblendic or syenitic gneiss.

Mica schist is a highly foliated rock composed of quartz
and mica, the mica often highly prominent and enveloping
the quartz, which is in irregular plates, knots, and seams ;
while in other cases the quartz predominates, the mica
being present in only sufficient amount to give the mass a
schistose structure. Where the mica almost wholly disap-
pears, the rock still retaining the schistose structure, it is
sometimes called quartz schist, which is therefore a rock
consisting almost wholly of quartz, and showing a tendency
to split into parallel layers.

A rock composed of grains of quartz, sometimes of
considerable size, bound together by a silicious cement
into a mass of flinty hardness, is called quartzite. It is a
sandstone, metamorphosed by the infiltration of a silicious
solution, or by the softening of the outlines of its grains,
into a rock breaking with the characteristic glassy fracture
of quartz, while its granular texture and bedded structure
testify to its original condition.

A variety of mica schist, in which the quartz is usually
in small amount, and the mica is a hydrous variety, i. e.,
containing water, is called by Dana hydro - mica schist.
These schists have usually a grayish or greenish color, a
pearly luster, and a greasy feel like talc, whence they are
commonly called talcose schist. A true talcose schist is
not a common rock. It is a foliated aggregate of scaly
talc, with small amounts of quartz or feldspar, of whitish
to greenish colors, and unctuous to the touch.

22 APPLIED GEOLOGY.

Chlorite schist is a foliated rock composed of chlorite
and some quartz, with occasionally small amounts of other
minerals. Its usual color is a dark green. It is commonly
a soft rock, but sometimes the quartz, which usually occurs
in scattered leaves or bunches, so interpenetrates and inter-
locks the entire mass as to give it a considerable degree of
hardness.

Hornblende schist is a black or dark-green foliated
rock, composed of dominant granular or fibrous horn-
blende, having a foliated arrangement, with minor quan-
tities of quartz or feldspar. When the foliated structure
is wanting, a rock of similar composition would be called
amphibolite or hornblende rock.

Serpentine is a dark-green or reddish-brown rock, of
compact texture and greasy feel. It is so soft as easily to
be scratched by a knife. The mineral serpentine of which
it is composed is probably, in all cases, a product of the
metamorphism of other minerals or rocks. It usually
occurs in irregular beds among metamorphic "schists.

The Igneous or Massive Crystalline Rocks. —
Most important of these is granite, already alluded to un-
der gneiss. It is a compound of quartz, feldspar (mostly
orthoclase), and mica ; feldspar is usually the predominant
ingredient, of an impure white or reddish color, while
mica is the least prominent. The quartz varies from white
to smoky-brown in color, and may readily be distinguished
by its fracture, hardness, and luster. The texture of gran-
ite varies from very fine-grained to one made up of crys-
tals of considerable size, the crystals being interlocked, or
welded together at their surfaces, so as to form a mass of
great firmness. The mica in granite may be partially or
entirely replaced by hornblende, giving rise to a usually
darker-colored granite, called syenitic granite. Where the
quartz disappears from a granitic rock it is called minette
or mica trap ; where feldspar dies out we have greisen — a
rock interesting only from its association with tin-ores ;

DESCRIPTION OF ROCKS. 23

while the disappearance of mica gives rise to a rock called
aplite and pegmatite ; or, if of foliated structure, granulite.

Felsite is an intimate mixture of feldspar with some
quartz, of an exceedingly fine-grained — i. e., aphanitic or
flinty — texture, and of a variety of colors, from yellowish
to nearly black. It greatly resembles some quartz rocks,
from which it may be distinguished by its slightly inferior
hardness, its hardness being that of feldspar, and by the
fact that in thin splinters it can be fused like feldspar be-
fore the blow-pipe, while quartz can not.

Syenite is a granular crystalline rock, composed of
orthoclase and hornblende, the orthoclase predominating,
and, from its usually being of a reddish color, giving the
rock a prevailing red tint. Sometimes, however, feldspar
of a lighter color occurs, yielding grayish syenites.

Trachyte is a grayish, or sometimes reddish or brown-
ish, rough-textured compound, in which feldspar predomi-
nates, often showing glassy crystals, united with some
hornblende or augite and dark mica, while magnetite is
rarely absent. A trachytic rock of highly silicious charac-
ter, and often displaying quartz-granules, but rarely con-
taining hornblende, with a matrix usually very compact,
or even enamel-like, is called rhyolite or liparite.

Diorite is a granular, dark-green, tough rock, composed
of oligoclase feldspar and hornblende, with usually some
magnetite. It differs from syenite in its kind of feldspar,
in its usual range of color, and in being usually of finer
texture.

Dolerite is a granular rock of gray to black colors,
composed of labradorite feldspar and augite, with usually
some magnetite. When it is exceedingly fine-grained and
compact, it is called basalt. Basalt often contains grains
of a bottle-green mineral called chrysolite. When dolerite
contains chlorite, giving it a greenish color, it is often
called diabase.

The rocks described above are by far the most widely

24 APPLIED GEOLOGY.

distributed, and therefore most commonly met with ; and
with them have been named a few of less frequent oc-
currence, as exhibiting interesting variations of composi-
tion or structure.

Key for Approximate Determination of Rocks.*

The following brief key for rock determination, based
on (i) texture, (2) hardness, and (3) structure and compo-
sition, may prove useful to the beginner :

1. Examine freshly broken, angular fragments with a lens.

A. Components not perceptible. See 2.

B. Components perceptible. See 4.

2. Test hardness of i A with a knife :

a. H i to 3^, easily scratched with a knife — sedi-

mentary or decomposed :

a' — Very soft, earthy aspect, plastic when wet, Clay,

b' — Harder, in thin, irregular, fragile laminae, Shale.

c' — Cleaving to thin firm plates, Slate.

d' — H 3, effervescing strongly with cold acid, Limestone.
e' — H 3 to 4, effervescing sluggishly with cold

acid, rapidly with hot, Magnesian Limestone.

f — H 2.5 to 3.5, usually green, somewhat soapy

to the touch, not effervescing, Serpentine.

b. H 5 to 6, heavy, becomes black and magnetic by

heat:

g' — Streak and powder yellowish brown, luster

earthy to silky, Limonite.

h' — Streak and powder red, luster earthy to me-
tallic, may be perceptibly crystalline, Hematite.

c. i' — Not scratched by knife, glassy luster, con-

choid fracture, Quartz Rock.

j' — H 5 to 6, black or gray, often holds green

grains of olivine, Basalt.

k' — H 6, fusible in thin splinters. See 3, or pos-
sibly, Felsite.

* The idea of this key was suggested by Geikie's excellent " Text-
Book of Geology."

DESCRIPTION OF ROCKS. 2$

3. 2 k' may be glassy, when if —

T — Of uniform texture, dark color, translucent on

edges, of glassy aspect, Obsidian,

m' — Of pitchy aspect, various colors, slighty trans-
lucent, Pitchstone.
n' — Of rounded grains, of frequent concentric

structure, in enamel matrix, Perlite.

n" — Of enamel-like matrix, often holding grains of

mineral, especially quartz, Rhyolite.

NOTE. — The exact determination of hard, very fine-grained rocks
usually requires microscopic and chemical examination.

4. Test hardness of I B.

o' — Soft, gray to white, crystalline to earthy,

heated yields vapor and whitens, Gypsum.

p'— Easily scratched, effervesces readily with

acid, Limestone.

q' — Slightly harder than p', effervesces sluggishly

with acid unless hot, Dolomite.

r' — H about 4, brown, effervesces with hot HC1,

giving yellow solution, Siderite, etc.

s' — Of hard, rounded grains, chiefly quartz, ce-
ment various, Sandstone.

t' — Of hard, rounded, or angular pebbles,

Conglomerate or Breccia.

u' — Of quartz-grains cemented by silica, fracture

usually glassy, Quartzite.

v' — H 6, color and streak black, heavy, magnetic, Magnetite.

w' — H variable, schistose, with glistening surface,

of mica and quartz, Mica Schist.

x' — Soft, color white to light green, soapy feel,

schistose or massive, Talc.

y' — Easily scratched, dark green, slightly soapy,

schistose, Chlorite Schist or Hydro-Mica Schist.

z' — Hard, greenish black, rather heavy, schistose,

chiefly hornblende, Hornblende Schist.

a" — Hard, chiefly quartz, but schistose from a lit-
tle mica, Quartz Schist.

b" — Scratched with difficulty, of interlocked or
welded crystals. See 5.

26 APPLIED GEOLOGY.

5. Rocks of 4 b" alternate with other crystalline rocks

or show some foliated arrangement of their
crystalline constituents — metamorphic. See 6.
Rocks of 4 b" do not alternate, are massive, send
branches into other rocks — igneous. See 7.

6. Composed of the following minerals, more or less

distinctly foliated :

c" — Quartz, feldspar, and some mica, Gneiss,

d" — Quartz, feldspar, and hornblende (mica),

Syenitic or Hornblenclic Gneiss.

e"— Quartz, feldspar, and chlorite or talc, Protogine Gneiss,
f" — Quartz and orthoclase, often garnets, Granulite.

7. Rocks eruptive or intrusive, composed of —

g" — Quartz, feldspar, and mica, Granite,

h" — Quartz, feldspar, and hornblende (mica),

Syenitic Granite.

i" — Orthoclase and hornblende, often red, Syenite,

j" — Oligoclase and hornblende, dark green or

black, Diorite.

k" — Labradorite and augite, gray to black, Dolerite.

1" — Feldspar base and clear crystals of orthoclase,

rough to the feel, Trachyte.

m" — Aphanitic base holding crystals of feldspar or

quartz, Porphyry or Quartz Porphyry.

This key is intended only as a convenient aid to the
student in finding the probable variety of rock with which
he has to deal. His specimens should with this aid be
carefully compared with descriptions in works on geology
or lithology, and much critical study and comparison will
be necessary to avoid the probability of error. It is well
to be slow and painstaking at first, that one may be rapid
later.

For a wider study of rocks, the student is referred to
the following works : Von Cotta, " Rocks Classified and
Described," translated by Lawrence ; Geikie, " Text-Book
of Geology," Book II ; Dana, " Manual of Mineralogy and
Lithology."

CHAPTER III.

ARRANGEMENT OF ROCK-MASSES.

ROCK-MASSES may be built up into the structure of the
earth's crust in any one of three ways : First, and far the
most widely diffused, as stratified rocks, or those occurring
in nearly parallel beds of various thickness ; second, as great
unstratified masses like granite, exhibiting no signs of true
bedded structure ; and, third, as included or vein-form
sheets, or masses of rock-material, differing from the inclos-
ing rocks in composition or in structure, or in both respects,
and occupying what were once apparently open fissures or
cavities in these rocks.

Stratified Rocks. — The most striking character that
marks the stratified rocks, and that from which they de-
rive their name, is their occurrence in parallel sheets or
strata piled one upon another to form masses often of vast
thickness. These beds, when not metamorphic, usually
contain indubitable evidences that they have been gradu-
ally and successively deposited in water, and mostly in the
waters of the sea, in a manner exactly analogous to that in
which beds of mud, sand, gravel, peat, and limestone are
being accumulated at the present day. Most convincing
of these evidences of formation in water is the frequent
occurrence in the bedded rocks, at the most various
depths, of the remains of animals, most commonly marine,
and occasionally of plants, which often retain their struct-
ural characters in a high degree of perfection. Such

28 APPLIED GEOLOGY.

traces of the former plants and animals of the globe are
called fossils ; and they not only give us some glimpses of
the life-history of the usually remote periods during which
the rock-materials were accumulated, but they also furnish
valuable evidence of the conditions under which they
were formed, whether in marshes, or in water, marine,
brackish or fresh, clear or turbid, and at greater or less
depths. It is obvious that of the beds thus superimposed
on each other the lower will have been the earlier formed,
while the overlying beds will be successively younger.
Thus in stratified rocks whose normal position is obvious,
or can by any means be made out, superposition is re-
garded as a reliable evidence of relative age. The sev-
eral beds in any series of stratified rocks are usually sep-
arable from each other with little difficulty at their plane
of junction, probably indicating that the lower bed had
been somewhat consolidated before the materials of the
succeeding one were deposited. A character peculiar to
stratified rocks, because it results from successive depo-
sition, is lamination, as already defined. It belongs more
especially to the finer-grained sediments, like shales, fine-
grained and somewhat argillaceous sandstones, and to
some argillaceous limestones. Commonly the planes of
lamination are parallel, or nearly so, tc> those of bedding ;
but in some rocks, especially sandstones, they may be di-
agonal to the bedding, giving rise to what is called false
bedding or current bedding. Usually, but not invariably,
rocks split more easily on the lamination than in other di-
rections ; and such rocks, when used in structures, should
always be laid with their edges to the weather, as they
will be more durable in that position.

When a stratified rock becomes metamorphic, lamina-
tion gives place to foliation, the planes of mineral ar-
rangement, in most cases, probably following the original
planes of deposition ; or slaty cleavage takes the place of
the original tendency to split on lamination planes, while

ARRANGEMENT OF ROCK-MASSES.

the laminae may still frequently be displayed in bands of
different shades of color.

Position of Strata and Definition of Terms. —
The original position of the beds of stratified rocks must
have been nearly horizontal ; but, as the result of the
action of forces, for a discussion of which the student
should refer to general treatises on geology, the strata in
all metamorphic regions, and in many localities where the
rocks have undergone no noteworthy transformation, are
no longer horizontal, but are bent, doubled, and crumpled
on the large scale, and often broken, with the fractured
ends slipped past each other. The disturbances of strata,
and the changes to which they have been subjected, give
rise to the use of several terms, the meaning of which it is
important to understand.

The dip of strata is the amount of their departure from
a horizontal plane.

Where the dip is considerable, it is conveniently meas-
ured by means of an instrument called a clinometer, a
convenient form of which is that of a foot-rule, two inches
wide, folding to six inches, in one face of which is hung
a delicate pendulum, swinging on the center of a graduated
semicircle. (Fig. i.)

This instrument held before the eye, and its lower

FIG. i.

edge made to agree in direction with the slope of the in-
clined rocks — or, better, set on its edge on a slip of board
laid upon the rocks and shifted carefully about until the
pendulum shows the greatest possible inclination — will give
the dip of the strata with a good degree of accuracy.

30 APPLIED GEOLOGY.

Where, however, the dip of the rocks is slight, as in much
of New York, in western Pennsylvania, and in several
Western States, it is found by ascertaining the height of
some persistent stratum above a fixed plane like the sea-
level, at several points where it appears in natural ex-
posures, or is revealed in borings or excavations. The
mutual distances of these points being found, the dip per
mile and the direction of the dip can be ascertained. The
amount and direction of dip are points of great practical
as well as scientific importance, and should be carefully
observed.

The strike of rocks is a direction at right angles with
their dip, so that when the second is given the first may
be known. For example : the dip of the rocks in a large
part of New York is south, inclining a little west. Hence,
the strike or the direction in which the rocks range across
the State is nearly west ; and it would be the same if the
dip were in an exactly opposite direction, or to the north.

A monoclinal fold is one in which the strata dip in
but a single direction. A common case in our Western
Territories is that which is sketched in the following dia-
gram, where horizontal strata are sharply folded up into a
somewhat steep ridge, and then resume their original nearly
horizontal position :

An anticlinal fold is one in which the strata dip away
from an axis, forming an arch, as in Fig. 3, where a repre-
sents the axis of the fold from which the strata dip each
way. A common occurrence with such folds is that the
strata are broken at the axis, when the agencies of wear
either plane down the fold to a level, its presence being

ARRANGEMENT OF ROCK-MASSES. 31

indicated only by the opposite dip of the strata ; or, where
hard beds occupied the surface, the strata may be cut out

FIG. 3. — Anticlinal.

along the axis, as indicated by the dotted line in Fig. 3,
leaving two more or less marked ridges.

A synclinal fold is where the strata dip from opposite
directions toward an axis, forming a trough, as in Fig. 4.

FIG. 4. — Synclinal.

In greatly disturbed regions, these folds are often so
thickly set as to give the strata a crumpled appearance,
visible even in hand specimens.

Frequently, also, not only in folded regions, but also
in those in which the strata retain a nearly horizontal po-
sition, the strata are found to have been broken across,
and the beds on one side of the break to have been
dropped below those on the other, so that the two halves
of the same bed no longer occupy the same plane. Such
an occurrence is called a fault, and the faulted beds are
said to be thrown. Thus we speak of the downthrow and
the upthrow. The plane of fracture, though sometimes

32 APPLIED GEOLOGY.

vertical, is usually inclined more or less from the vertical.
The amount of this inclination from the vertical is called
the hade of the fault. Vertical faults, therefore, have no
hade. In the great majority of cases, " faults hade in the
direction of the downthrow," so that the upper surface of
the beds that have slid down makes an acute angle with
the plane of fault. (See Fig. 5, in which a and b are
planes of fault, of which b has no hade, while a h hades at

FIG. 5.— Faults.

an angle of 50° with the vertical.) The beds c d e f have
it may be seen, slid downward along the planes of fault
so that the upper surface of the downthrown beds g makes
an acute angle with the plane a h. Such a fault is called
a normal fault, while the much less frequent case in which
the downthrow side makes an obtuse angle with the plane
of fault is called a reverse fault. Hence, in mining faulted
beds, like those of coal or iron, in the absence of other
indications, the continuation of the bed is to be sought
down the fault-plane when it slopes from the workings,
and up it when it slopes toward the workings, as may be
seen from the left side of Fig. 5. The walls of fault-fis-
sures, when they consist of firm rocks, are often smoothed
or glazed, and striated in the direction of movement. Such
glazed surfaces are called slickensides.

Where strata are laid open to observation by the re-
moval of loose materials, the point of appearance is called
their outcrop or basset. Frequent places of outcrop
are along the shores of bodies of water, or in the banks
of deep-cut streams, or on the eroded sides and summits
of hills and mountains.

ARRANGEMENT OF ROCK-MASSES.

Conformable strata are those which succeed each
other in the regular and parallel order of superposition.

Unconformable strata are those in which (i) the
overlying beds rest against the upturned and eroded sur-
face of the lower beds, not agreeing with them in dip, as

FIG. 6. — Unconformity by Upthrow.

in Fig. 6 ; and (2) the overlying beds rest upon the much-
eroded surface of the underlying ones, agreeing with them
in dip, as in Fig. 7.

In either case, " the base of the one set of beds rests in

FIG. 7. — Unconformity by Erosion.

different places on different parts of the other set of beds."
The first kind of unconformability is the more commonly
observed, and doubtless always includes what is essential
in the second, viz., the erosion or denudation of the lower
beds, before the deposition of the upper ones. Uncon-
formability testifies unmistakably to a considerable lapse of
time, during which important physical changes occurred,
including notable changes of level, as intervening between
the periods of deposition of the two sets of beds.

The term denudation is applied to the waste and

APPLIED GEOLOGY.

wear df/#cks by weathering and by the agencies of water
atmosphere. (See Fig. 3 for illustration.) Denu-
dation is a phenomenon which is going on constantly be-
fore our eyes, not more obviously in the tremendous rend-
ing and grinding action of the waves than in the silent
activity of rivers, brooks, and rills, whose turbidity testifies
that they are tearing down and carrying away to valley or
ocean the materials of the uplands. The amount of denu-
dation in all elevated parts of the earth is enormous, and
to it is due almost wholly the present aspect of the land-
surface of the globe.

Unstratified Rocks. — The structure of these rocks
is massive, and, as their name implies, they show no
signs of bedding or of successive accumulation, their only
divisional planes, where they occur, being of a jointed
character. Though it can hardly be doubted that unstrati-
fied rocks form the foundation on which all stratified
rocks rest, yet they are of far less frequent occurrence as
surface appearances than those of the stratified series ;
and it is probable that our opportunities for knowing them
are due in many cases to great uplifts and enormous denu-
dations. They owe their origin in all cases, perhaps, to
igneous agencies or to a metamorphism pushed to such an
extreme as to become essentially igneous. They occur,
sometimes as great bosses, like granite, surrounded by
other rocks into which they frequently send out arms ;
sometimes as the central portions of great mountain-chains,
as in parts of the Sierra Nevadas and the Alps ; some-
times as vast sheets of enormous thickness, as in portions
of our Western plains ; sometimes as great cake - like
masses, called laccolites, thrust into the midst of stratified
rocks and bulging them up into dome-like eminences, as
in the Henry Mountains of Utah ; and sometimes as great
interbedded sheets overlaid by beds deposited apparently
since they were poured out as lavas, as in the so-called
melaphyre rocks of northern Michigan, whose amygda-

ARRANGEMENT OF ROCK-MASS,

loidal portions furnish in some cases rich
native copper.

Included or Vein-like Rocks. — The masses here
called included fill what, in the great majority of cases if
not in all, appear once to have been open fissures or cavi-
ties in the inclosing rocks. In some cases the filling mate-
rials have evidently been introduced in a state of igneous
fusion, such included masses being called dikes. In
other cases the fissure or cavity has apparently been filled
from solution in water or by sublimation, such inclusions,
where they fill fissures of greater or less extent, being
called veins, and, where they fill irregular cavities, being
called by the German name Stbcke, or stocks.

Dikes are usually nearly vertical in position, and have
a more regular and wall-like form than veins, whence
the name dike, signifying a wall. Indeed, irregular and
branching fissures filled with material apparently injected
in a plastic state are usually called veins rather than dikes,
as in the case of granite veins. The fissures filled by
dikes not unfrequently follow pretty closely for consider-
able distances the bedding planes of stratified rocks, giv-
ing to such dikes the appearance of beds. The rocks
which form the walls of dikes have usually been metamor-
phosed to varying distances by the heat, common changes
being consolidation, baking, and crystallization. The ma-
terial of dikes is frequently fissured by joints, which pass
often into a columnar structure, the columns being per-
pendicular to the walls. Dolerite with its varieties, ba-
salt and diabase, is a common dike-forming rock, though
some other varieties of igneous rocks are occasionally
found forming dikes.

Some veins, usually in granite, gneiss, or the crystal-
line schists, are filled with material similar to that of the
surrounding rock, though in a somewhat different crystal-
line state, often coarser ; and their composing minerals
were apparently separated from the inclosing rock to fill

36 APPLIED GEOLOGY.

rents of small extent during the process of consolidation.
Such are called veins of segregation.

True veins, called frequently mineral veins, fill what
have once been open fissures of variable extent, both ver-
tically and horizontally, some veins cutting the rocks to
unknown depths, while others are quite shallow ; some be-
ing traceable for miles, while others die out in a few rods.
The materials with which they are filled usually differ
notably from the inclosing or country rock. iThey are
usually of a crystalline granular texture, though often
earthy from decomposition or other causes, and have often
a banded structure of different minerals arranged parallel
to the walls. They are frequently the repositories of valu-
able metallic ores, and hence they, as also stocks, will be
more fully discussed in a subsequent chapter under the
head of ore deposits.

Relative Age of Rocks. — Probably the most fre-
quent question asked about rocks by persons little versed
in geological science is with regard to the approximate age
of certain strata, the marks of whose great antiquity have
been so obvious as to impress even the casual observer.
To this question it is not probable that any very satisfac-
tory answer can ever be given. It can only be said, in a
vague and general way, that the time embraced in the
events to which geology testifies is very long even to those
computations which would make it briefest. The relative
age, however, of the stratified rocks can be made out
with a good degree of certainty, not only for limited
districts, but for all that portion of the globe which
has been geologically explored ; and the various strata
have been arranged in a series which expresses ap-
proximately the order of their appearance in time. This
series has also been separated into larger and smaller
subdivisions or groups, which, while based on certain
interesting facts in their life-history or lithological con-
stitution, are of vital importance as affording a means

ARRANGEMENT OF ROCK-MASSES. 37

of ready reference for both scientific and economic pur-
poses.

These groups of strata, which, if piled upon one an-
other successively, would make a stupendous mountain-
mass more than a hundred thousand feet in height, are
nowhere found forming a complete and connected series ;
but rather, certain portions are found in one region, while
other parts of the series must be studied in other and per-
haps distant localities. The reasons for this fragmentary
distribution may be briefly stated. They are (i) that
during the vast periods of time embraced in geological
history, the regions where rock - materials might be de-
posited have been slowly but constantly changing, by rea-
son of fluctuations of level which have caused great and
often repeated changes in the distribution of land and
water. Thus, the areas where rocks were laid down have
been repeatedly shifted from age to age, regions which had
taken no part in rock-making, because they were dry land
while certain series of rocks were deposited, subsequently
changing places with former water areas, and becoming
themselves the theatres of deposition.

To this may be added (2) the probability that many
strata, once deposited in certain regions, have been en-
tirely or partially removed by denudation in the course of
subsequent changes.

The means by which an orderly arrangement of the
members of a series so essentially fragmentary into a con-
nected system has been effected are chiefly the following :

i. Superposition. — From what has already been said
about the mode of formation of stratified rocks, it is ob-
vious that the lowermost strata will have been first formed,
while the overlying ones must be successively more recent.
Hence, in any region where the natural succession of the
strata has not been too much confused by uplifts and
faults with subsequent denudation, the observed order of

superposition of the strata, as studied in tolerably con-
8

38 APPLIED GEOLOGY.

tinuous outcrops, will give their relative age ; and, if then
some well-marked bed or stratum of this region can be
positively recognized in some other locality where addi-
tional strata occur, the two series may be connected in
the order of time, and ultimately the same mode of obser-
vation may be extended to include other and far more
remote areas. Thus the observed order of superposition
is not only a very valuable but wholly indispensable
means of studying the relative age of strata. But it fre-
quently happens that over wide spaces the succession of
the strata can not be directly observed because they are
covered by surface accumulations, or separated by bodies
of water : how, then, shall we recognize strata already well
studied in certain localities, when we come upon them in
regions somewhat remote ? Or, again, from what is ap-
parently a completely continuous series of strata, whole
groups of beds may be wanting from the causes men-
tioned above, without leaving anything to mark their ab-
sence : how, then, shall we be able to detect this absence,
and to assign the strata that would make the series really
complete ? This recognition at distant localities of kin-
dred strata, that is, those having like positions in similar
series, this detection of groups missing from a seemingly
consistent series is accomplished by a second and highly
important means :

2. The Use of Fossils. — Throughout a very large
portion of the time during which the stratified rocks have
been accumulating, it is certain that forms of life have ex-
isted on our globe ; and the fossil evidences of their exist-
ence have been preserved, to a very useful degree, in nearly
all stratified rocks which are not metamorphic. Now, the
various distinguishable stages in the great series of rocks,
arranged in the order of their relative age, are character-
ized by the prevalence of certain forms of life, species or
genera not found in other members of the series ; or by
certain groupings of forms which do not exist elsewhere

ARRANGEMENT OF ROCK-MASSES.

in like relations ; so that by the careful comparative study
of the fossils of localities separated from each other more
or less widely, the rocks which contained them may be
placed in their proper relative place in the chronological
series. For figures and lists of the fossils which character-
ize the several members of the geological system, the stu-
dent will do well to refer to some one of the excellent
treatises on geology, like Dana's " Manual of Geology,"
Geikie's " Text-Book of Geology," Lyell's " Elementary
Geology," or Le Conte's " Elements of Geology." Some
examples of their use may be profitable. A large and
peculiar family of crustaceans called Trilobites, because
the body is divided lengthwise by de-
pressions into three lobes (see Fig. 8),
while found somewhat abundantly in the
rocks below the coal-measures, has not
yet been seen in any higher rock ; and
some of its genera, and nearly all its
species, are limited in their range to
certain sets of rocks : hence the family
of Trilobites is characteristic of the
rocks from the coal-measures down-
ward ; and its species, and in some cases
genera, become distinguishing marks for
the groups of rocks to which they are confined. So the
Spirifer (see Fig. 9), an easily recognized genus of shells,
which is confined to the strata from
the Upper Silurian to the Lower
Jurassic (rock groups presently to
be mentioned), has well-marked
species which are confined to the
several groups of strata, and hence
are used as landmarks for these

groups, while the genus as a whole distinguishes all the
rocks within the limits named.

3. The lithological characters of strata, though in

FIG. 8.

40 APPLIED GEOLOGY.

many cases they furnish very unreliable marks for recog-
nizing rocks, save within quite limited spaces, from the
fact that they do not remain constant, but frequently
change, so that within a comparatively short distance a
conglomerate may be seen to pass >into a sandstone and
then to shade off even into a shale, yet in some cases,
and especially among the older rocks, show such persist-
ency as to make them very convenient guides for the
rocks of certain districts. Thus, in central New York, a
band of limestone called the Tully, usually not more than
ten to fifteen feet thick, though occasionally rising to as
much as twenty-five or thirty, is persistent in character
over more than eighty miles from east to west, and fur-
nishes a most valuable guide to the relative age of the
rocks throughout its extent. So, likewise, in tracing coal-
beds from one valley to another, use is made of certain
somewhat persistent beds, usually of sandstone or lime-
stone, as &ry-rocks, within tolerably regular distances above
or below which the coal-beds are likely to be found. The
availability of these key-rocks is greatly increased if, in ad-
dition to pretty uniform lithological characters, they also
contain some well-marked distinguishing fossils ; but, in
any case, lithological characters, if carefully used within
limited areas, are of great use in giving guesses at truth, to
be afterward confirmed by other and more reliable evidence.
By the careful use of the three means just described,
the relative ages of the stratified rocks are made out. By
the use of characters derived from the last two sources,
but chiefly from the second, the entire series of strata is
also separated into greater and smaller groups, for con-
venience of reference, the larger divisions holding the
same relative position and bearing the same names over
the entire earth; while the smaller subdivisions, which
usually differ widely in details in regions very remote
from each other, are apt to receive in every country
special names of local significance, and are afterward

ARRANGEMENT OF ROCK-MASSES. 41

paralleled with each other, as far as possible, by a careful
comparison of fossils. Thus the crystalline schists, which
underlie all the fossiliferous stratified rocks, are generally
termed Archaean ; the fossiliferous rocks which succeed
these, and which are characterized throughout by a pro-
fusion of invertebrate fossils, a few remains of fishes being
found only in the upper beds, are called Silurian, and
admit of a generally used division into Lower and Upper
Silurian ; the succeeding groups of strata, in which fishes
of strange aspect are the dominant though by no means
the most abundant forms of life, are called Devonian ; to
which succeeds the Carboniferous formation, characterized
by the abundance of its coal-beds, and by the prevalence
of land-plants belonging mostly to the highest cryptogams.
Overlying the Carboniferous are found in many places
great series of strata, which, with an abundance of other
fossils, are characterized by the remains of reptiles, often
of great size and uncouth forms. These rocks, termed
usually Mesozoic, are susceptible of a threefold divi-
sion, universally used, into Triassic, Jurassic, and Creta-
ceous periods. To the Mesozoic succeed the rocks called
Tertiary or Cainozoic, which are characterized by the
prevalence of mammals, forms of life which up to these
rocks are represented only by a few very rare fragments,
and in which the invertebrate remains have usually a
strong resemblance to, and often identity with, creatures
now living. Its widely recognized divisions are called
Eocene, Miocene, and Pliocene, Lying upon the Terti-
ary deposits, where these occur, are found the more recent
and usually unconsolidated surface materials, including
drift-clays and bowlders, beach and terrace deposits, and
other accumulations of kindred -character, containing in
some parts the remains of man or his works, and called
Post-Tertiary or Quaternary.

The whole series of formations, from the top of the
Archaean to the top of the Carboniferous, is usually called

APPLIED GEOLOGY.

collectively the Palaeozoic — i. e., the age of ancient life —
because all the forms of life found in it resemble so re-
motely those now prevalent on the globe ; the term Meso-
zoic, applied to the succeeding rocks, signifying their
approximation in forms of life to the existing state of
things ; while the name Cainozoic (recent life), given to
the Tertiary strata, is significant of the resemblance of its
fossils to living species.

Subjoined is given, in tabulated form, the more com-
prehensive divisions just described, with the larger sub-
divisions, as recognized by American geologists :

Quaternary or Post-Tertiary,

Tertiary or Cainozoic,

Secondary or Mesozoic,

f Carboniferous,

Primary or
Palaeozoic,

Devonian,

Upper Silurian,

Lower Silurian, including
Cambrian or Primordial,

Archaean,

Recent or terrace,

Champlain,

Glacial.

Pliocene,

Miocene,

Eocene.

Cretaceous,

Jurassic,

Triassic.

Permian or Permo-car-

boniferous,
Coal-measures,
Sub - carboniferous or

Lower Carboniferous.
Catskill,
Chemung,
Hamilton,
Corniferous,
I Oriskany.

(Lower Helderberg,
Salina,
Niagara.
Hudson,
Trenton,
Canadian,
Primordial, Potsdam

most important.
Huron ian,
Lauren tian.

ARRANGEMENT OF ROCK-MASSES.

Of a number of the divisions given, there are sub-
divisions of much local interest, for which, as well as for
the European subdivisions, the student can, if he desires,
consult the treatises mentioned on page 39. By the stu-
dent familiar with German, the elaborate tables of Euro-
pean strata given in Credner's " Elemente der Geologic "
can be consulted with advantage.

CHAPTER IV.

ECONOMIC RELATIONS OF GEOLOGICAL STRUCTURE.

HAVING now briefly considered those portions of
structural geology which seem essential to the ready com-
prehension of what is to follow, let us consider how geo-
logical science may make men's practical endeavors more
effective.

Economic geology may be defined to be that de-
partment of science which treats of the earth's structure
and mineral products as they are related to the supply of
human wants.

The economic geologist considers structure as it con-
cerns the adaptability of rocks and strata for certain pur-
poses, or as it is related to the occurrence and accessibility
of valuable deposits. He regards rocks as in themselves
fitted for certain uses, or as the probable repositories of use-
ful materials. He is interested in the relative age of strata,
and the means by which it may be determined, because it
furnishes him an available guide to their possible desirable
contents. He aims at an accurate and extended knowl-
edge of those geological deposits which have practical
utility. Nay, more : these deposits bear to each other
practical and often very essential relations. Of these he
takes careful note — for example, the proximity of metallic
ores to the fuels and fluxes necessary for their beneficia-
tion, or to the kindred ores with which they may profitably
be mixed. Moreover, useful materials are valuable or value-

ECONOMIC ASPECTS OF STRUCTURE. 45

less, according to their relations to the currents of human
industry and to the means of profitable utilization. What
value has an excellent quarry-stone, remote from transpor-
tation and from the great centers of construction ? Of what
present worth is an ore of moderate richness, at a long dis-
tance from the means of smelting or of easy concentration ?
What avails a rich placer deposit, without an abundant
water-supply for its cheap separation ? To such consid-
erations, and others like these, little noted by the ordinary
geological observer, the economic geologist must be keenly
alive, for they are what constitute the relations of structure
and products to the supply of human wants. Nor are
these wants, as signified by demand, by any means con-
stant. The progress of discovery or invention may change
very greatly the economical estimate of a substance once
little regarded. The naphtha and Seneca oil of thirty
years ago are the petroleum of to-day. Iron pyrites has
become a substance of great commercial importance, since
its recent use as a source of sulphur in the manufacture
of sulphuric acid. The ores of molybdenum and tung-
sten, till lately regarded only as interesting minerals, are
now called to the attention of the United States geolo-
gists by their use as pigments ; while all deposits of nickel
have recently become of greatly increased interest since
the wide use of this metal in electro-plating. Hence it
is desirable that the economic geologist should always bear
in mind " that, much as may already have been utilized,
there are still many substances in the earth's crust which
can be turned to account in the increasing requirements
of modern civilization." (Page.)

Economic Relations of Geological Structure. —
The economic bearings of geological structure are numer-
ous, and of the most obvious importance. Structure, for
example, conditions the relative accessibility of desirable
substances ; the facility with which they may be worked ;
the ease and consequent expense with which excavations

46 APPLIED GEOLOGY.

and tunnels may be made, and their durability when fin-
ished ; the reliability of the foundations of important en-
gineering and architectural structures ; the accessibility,
the abundance, and the continued purity of deep-seated
water-supplies ; and not unfrequently the possibility of
effective drainage.

Accessibility. — Among stratified rocks, it is obvious
that their dip must exert a paramount influence on the
accessibility of any particular bed from the surface. If
the dip is slight, the depth below the surface of a bed will
increase but slowly as we recede from the outcrop in the
direction of dip ; while, if the dip is considerable, the
depth, and consequently the difficulty of access, increases
rapidly. A dip of one degree carries the strata down
ninety-two feet in a mile. The following table shows the
descent for a surface-distance of one hundred rods for
dips of from one to twenty degrees, and for every five de-
grees thereafter up to forty. It will be obvious that when
we pass beyond the outcrop of a bed in the line of its as-
cent, this bed will disappear and give place to underlying
beds :

Dip i° descent for 100 rods, 28.8 feet.

3° >> » 86.5

4° „ „ II5-4

5° » » J44-3

6° „ „ 173

7° „ „ 202.6

8° » » 232

9° » ,, 261.3

10° „ „ 291

XI° » » 32I-5

I2° » » 35°-7

13° » „ 381

14°

442

ECONOMIC ASPECTS OF STRUCTURE.

Dip 1 6° descent for 100 rods, 473 feet.
» J7° » >, 5°4-5 »

„ 18° „ „ 536 „

»» J9° „ ,, 568

» 20° » » 600.5 »

» 25° „ „ 769-4 >,

» 30° „ ,i 952-7 „

» 35° » „ ii55-4 „

» 40° „ ,, J334-5 »

It may be seen from this table that even small dips
make an important difference in accessibility at some dis-
tance from the outcrop, while dips of 5° and upward make
necessary, before mining operations are begun, a careful es-
timate of the cost of sinking shafts, and the after perpetual
expense of hoisting to the surface the water and the min-
eral which is the object of search. In all cases, therefore,
where the dip of the rocks is known or can be ascertained,
it needs to be taken into careful consideration in judging
of the depth at which valuable deposits may be reached.
In making this estimate also it should be remembered that
the rate of deepening below a given plane is greatest di-
rectly down the dip, and diminishes each way from this
line.

Faults also affect the accessibility of deposits relatively
to our workings. They may bring the continuation of a
bed nearer to the surface or remove it farther from the
surface, or, bringing it within reach of denuding agencies,
they may have caused it to be entirely removed. In even
the most favorable cases, since they interrupt the continu-
ity *of beds, faults derange the underground approaches
and means of transportation and increase the expenses of
working.

Great uplifts with subsequent denudation have likewise
in many regions brought within easy reach deposits which
must otherwise have remained utterly inaccessible. In-
deed, it is reasonably certain that the great class of crys-

48 APPLIED GEOLOGY.

talline rocks with their valuable stores of building and
ornamental stones, and the still more valuable veins of
metallic ores which many of them inclose, have by this
means alone been made accessible to man. In other cases
the agencies of denudation, by excavating deep valleys in
undisturbed and nearly horizontal strata, have, while sweep-
ing utterly away great masses of valuable deposits, made
the outcropping edges of the remainder easy of access
and of drainage by tunnels driven into the hill-sides where
they are found. Numerous examples of this kind may
be found in mining for coal and iron-ores.

Relations of Structure to Facility of Extrac-
tion.— Useful substances, whether building-stones, min-
eral fuels, or ores, are extracted from their repositories
either by open workings called quarries or by underground
mining operations ; and the ease with which these pro-
cesses can be carried on, and the resulting materials re-
duced to merchantable dimensions, depends in an impor-
tant measure on structural characters. In many cases the
workings may be so arranged with reference to the dip of
the strata as to clear themselves of water or to collect it
where it can be most conveniently removed, while the
handling of the materials is facilitated by a descending
grade. The bedded and jointed structure of many rocks
greatly aids the operations of the quarryman, enabling
him, where there are two sets of joints at nearly right an-
gles, to extract, with little waste of material, tolerably regu-
lar blocks of a size limited by the distance apart of the
joints and the thickness of the beds. Where the bedding
or the jointed structure, one or both, is wanting, recourse
must be had to the laborious operations of channeling or
drilling, with subsequent wedging or blasting, in the last
case often with great waste of material. The jointed struct-
ure of coal, called the cleat or face, and the end, is of such
importance that the workings must agree with it in direc-
tion. Where the beds are very thin, or the joints very

ECONOMIC ASPECTS OF STRUCTURE.

closely set, the rock may be unfitted for any useful pur-
pose, while the presence of a single system of joints at
suitable distances may adapt a thick-bedded or massive
rock for being extracted for large columns or for mono-
liths. The laminated or schistose structure of many rocks
is an important aid in reducing them to proper dimen-
sions. Availing himself of this, the workman, by repeated
blows along the edges, causes thick masses to split parallel
with the bedding, and thus with no great difficulty brings
them to the thickness desired. The presence of concre-
tions or of a concretionary tendency, as also of cross or
current bedding, should be carefully noted, as they meas-
urably or entirely unfit a rock for use.

Relations of Structure to Expense of Exca-
vation, Tunneling, etc. — The ease and consequent ex-
pense with which excavations, tunnels, shafts, and other
engineering works of like character can be accomplished,
and their permanence when finished, will depend very
largely on the nature and structure of the rock formations
through which the works must be pushed ; and all esti-
mates of expense should be based on the best attainable
knowledge in these respects. The hardness of the rocks
that must probably be penetrated ; their firmness or ability
when cut through to sustain the pressure of the masses
above and around them without artificial support ; their
durability in sides and roof when exposed to the atmos-
phere and weather ; the position of beds, whether hori-
zontal or highly inclined ; and their succession* whether
tolerably uniform or in alternations of firm beds with
others that are friable or of ready disintegration; their
permeability^ whether close-grained and solid, or porous
and seamed with fissures and joints, so as to make them
ready water-ways — these and other considerations of like
import are of vital interest in all undertakings of this
character, and they present questions which can be satis-
factorily answered only by a careful geological examina-

50 APPLIED GEOLOGY.

tion. Beds of hard, firm rocks with few or no joints will
be difficult and expensive to penetrate ; but they will be
self-supporting throughout and durable when finished,
and in cuttings only a minimum of material needs to be
removed. The first cost, therefore, is likely to be the
only cost ; while incoherent strata of gravel and sand,
though easy of excavation, require support at every step
by expensive curbing or by arches of masonry, or, in cut-
tings, materials must be removed until the angle of rest is
attained, so that the cost in the two cases may eventually
prove not very unequal. Friable sandstones, fissile and
easily decomposed shales, and not unfrequently the cut
edges of highly inclined strata, will need proper support
in both sides and roof, while fissured and porous water-
bearing beds must have due provision made for carrying
away the superfluous water, or must be masked by imper-
vious walls.

The cutting of one of the most extensive tunnels in
this country passed through many vicissitudes, and was
ultimately completed only after years of delay, presum-
ably through insufficient knowledge on the part of its
projectors of the obstacles likely to be presented by the
region through which it had to be driven, and consequent
insufficient estimates of probable expense ; and the con-
tractors for driving a tunnel to supply one of our great
lake cities with water, meeting with an unsuspected water-
way in the tough clay through which they were cutting,
were forced to close the end of their workings by a strong
bulkhead, and make an expensive dttour to avoid the
obstacle thus unexpectedly presented, yet which careful
previous trials would probably have revealed. The his-
tory of many similar works would doubtless furnish addi-
tional illustrations of the importance of a knowledge of
geological structure to those engaged in engineering enter-
prises of the kind here considered.

Foundations of Engineering and Architectural

ECONOMIC ASPECTS OF STRUCTURE. ^

Works.— It is evident that the stability of the founda-
tions of engineering and architectural structures must de-
pend entirely on their adaptation to the geological char-
acter of the underlying formations. If firm rock can be
reached at reasonable depths, the best possible foundation
is gained. Thick beds of tough and homogeneous clay
also afford good foundations. But, where a great depth of
loose, uncompacted materials is encountered, expensive
preparations must be made to insure the stability of heavy
structures. The great viaduct in Cleveland, constructed
at a cost of more than two million dollars, was built across
an alluvial flat, where immense sums had to be expended
in deep excavations, driving close-set piles, and building
up a substructure of grouting, before the piers of the
bridge could be commenced. Every considerable town
can furnish numerous examples, in the cracked and dis-
torted walls of buildings, not always large nor heavy, of
the need of using precautions proportioned to the native
instability of the substratum on which the structure must
rest. So, too, one occasionally sees important retaining
walls yielding to the easily foreseen thrust of alternating
beds of clay and quicksand, partly from insufficient at-
tention to the character of the beds to be sustained, and
partly from the lack of due provision for draining off the
water which, in heavy rains, heightens manifold the natu-
ral instability of such deposits. In structures intended to
hold or convey water, such as dams, reservoirs, and canals,
minute attention is needed to the character and structure
of the underlying beds. For such constructions, no sub-
stratum can be better than tough and compact clay, or
close-textured and massive rocks, nor could anything well
be worse than loose sands and gravel, or porous, fissured,
and jointed rocks. In the first case, little care is needed,
save to secure the requisite strength and thoroughness of
work ; while in the second no precaution can be too great
to remedy the innate defects of the foundation. Espe-

52 APPLIED GEOLOGY.

cially is this true when high dams are to be built, in which
the pressure of a great column of water will heighten the
permeability of the substratum and exaggerate its every
defect, and where any defect unremedied is sure to lead
to terrible disasters.

Structure and Water-Supply.— An abundant sup-
ply of wholesome water, free from risk of organic contami-
nation, is of vital importance to individuals and communi-
ties ; and it is a provision which the growth of population
and its concentration on limited areas render every day
more needful and more difficult. The usual sources of
supply for families and small communities, aside from cis-
terns filled from roofs, are wholly geological in their nature,
and depend for their character, their permanence, and their
safety, on the structure of the region in which they are found.
They are springs, wells dug or driven in drift or other sur-
face accumulations, and artesians bored through drift or
rock, often to very considerable depths, in which the water
either overflows at the surface, or rises within easy reach
of pumping apparatus. The term artesian is often con-
fined to wells of this class that overflow, though with no
very good reason ; for it will presently be seen that what
is really characteristic about wells of this kind is that they
derive their water from sources deeper seated than usual,
and that the origin of their supplies is not local, but more
or less remote.

Springs. — These are sources of water arising from the
underground circulation of the water that penetrates the
earth from rain and snow. This water descends through
the loose and porous materials until it meets with an im-
pervious bed, usually of clay, along which it flows, until
it gushes forth in a valley, or on the eroded edge of some
hill. Such springs are liable to contamination from im-
purities on or near the surface into which their waters
first sink ; but, if the point of issuance is at a consider-
able distance, the impurities are likely to be removed,

ECONOMIC ASPECTS OF STRUCTURE.

largely through the chemical agen-
cy of the air circulating in the per-
meable beds.

In Fig. 10, a and b are springs,
represented as issuing on the side
and at the base of the hill, at the
junction of the sand and gravel
beds i and 2 with the impenetra-
ble clay-beds 4 and 5. The por-
ous bed 3 is also a water-way, but
does not produce a spring because
the valley c is not eroded deep
enough to intersect it. The water
issuing at a is liable to contami-
nation from any sources of impur-
ities found between a and 4, and
that at b from the area between 4
and 5 ; but the latter, having a
greater distance to flow, would be
surer to be freed from organic con-
taminations by the action of the
air circulating in its bed. Both
will be likely to take into solution
portions of any soluble minerals,
like lime or gypsum, which they
may meet with in the beds through
which they percolate ; and, if such
minerals occur in any considerable
amount, the water of the springs
will be hard ; but, if little or no
soluble minerals are met with, it
will be soft — the terms hard and
soft, applied to water, being used
to describe the extent to which they
are charged with or are free from
dissolved minerals, with certain

54 APPLIED GEOLOGY.

other properties dependent on this. The abundance and
permanence of the flow of such springs will depend on (i)
the thickness of their porous beds, (2) the freedom of
percolation through these beds, dependent on their texture,
(3) the extent of the gathering ground from which their
supplies are derived, and (4) the amount of rainfall of the
district.

Springs are occasionally met with, like those at Union
Springs, New York, and the " Big Springs," so abundant in
northern Alabama, one of which supplies Huntsville with
water, which issue apparently from the mouths of caverns
in the solid rock. Such springs, because of the great
depth of their source and the extent of their gathering
ground, are apt to be of very considerable volume and of
great permanence. Also fissured rocks, such as jointed
limestones, resting on impermeable strata, cause lines of
springs or of wet ground on the sides of hills where they
outcrop in the direction of their dip.

Another class of springs is found in many regions, ris-
ing in strata of moderate dip, along lines of fault or on
open joints cutting down to porous, water-bearing strata.
They are often very copious, and are usually both durable
and of reliable purity. They are indeed a kind of natural
artesians.

In Fig. n, D represents a spring rising along the plane
of fault, D C, and deriving its waters from the porous sand-
stones 2 and 4, which are inclosed above and below by
the impervious strata i, 3, 5, while B represents a spring
rising along a jointing plane which penetrates to the porous
bed 2. The broken ends of the water-bearing beds, by
reason of the downthrow on the right of the faulting plane,
have been brought opposite to strata not easily penetrated
on the left, and hence the water with which they are satu-
rated rises along the fault or joint from hydrostatic press-
ure. The water at B having but little head would merely
well out of the ground, while that at D would be likely to

ECONOMIC ASPECTS OF STRUCTURE. 55

gush out with considerable force,
since its sources at 2 and 4 are
elevated above the point of out-
flow. The force and abundance
of outflow and the quality of the
water will depend on the same
circumstances as in the case of
artesians presently to be de-
scribed.

Wells.— The chief source of
water-supply for domestic uses,
for isolated dwellings, and small
towns, where springs are not at
hand, is found in wells, open ex-
cavations of varying depths,
reaching either to some water-
bearing stratum confined by im-
pervious beds of clay, or to a
common water-level of the dis-
trict, below which all the beds
are saturated with water. The
depth of the well in either case
will naturally depend on the
depth below the surface of the
general water-level, or of the
special water-bearing stratum.
In many localities the unconsoli-
dated materials are of little
depth, and do not carry water,
so that the well-excavation, if it
succeed at all, must be pushed
through rock to some porous or
open-jointed water-bearing stra-
tum, the probability of reaching
which within reasonable depth
through means so expensive

5 6 APPLIED GEOLOGY.

should be carefully considered beforehand, in the light
of the geological structure of the district as revealed in
ravines and quarries. Otherwise, a costly excavation may
end in complete failure, or be forced to depend on the
scanty and uncertain supplies oozing from the joints and
bedding-planes of close-grained rocks. In still other locali-
ties the loose surface materials rest immediately on fissured
or even cavernous rocks, through which their water, de-
scending unchecked by any impervious bed, are drained
away beyond the reach of wells. Such are the so-called
dry lots found especially in some limestone regions.

In any case, this widely used and convenient, if not
essential, source of water-supply is liable to become a
source of extreme danger to health, and even life, unless
more than usual care is used as regards its location, its
surroundings, and its construction, and unless the nature
and extent of the precautions that are used are based
upon the structure of the locality in which the excavation
is made. Where the excavation has passed through a con-
siderable thickness of impervious clay before reaching the
water-bearing beds, this is highly favorable to security;
but even here there is danger that the water may be con-
taminated by organic impurities leaching into it through
porous beds nearer the surface. This should be guarded
against by laying the retaining wall in hydraulic cement,
at least from the middle of the clay-seam to a sufficient
height above the mouth of the well to be secure from any
possible surface inflow; special care being taken where
the cemented wall begins in the clay to fill the entire space
around the wall with puddled clay or cement. If such
precautions are needed to insure safety from vitiation,
even in situations favored by the underground structure,
what shall be said of those wells excavated wholly through
sand and gravel down to the water-level, located, as they
too often are, in close proximity to house-drains, cess-
pools, and yards where animals are kept ? In such cases

ECONOMIC ASPECTS OF STRUCTURE.

an outbreak of certain too well-known types of disease, is
usually only a question of time and of the power of hu-
man beings to resist poisonous influences. In all such
localities it would be safer to obtain water for household
purposes from well-constructed cisterns, into which the
water should be admitted through a filter easily construct-
ed with washed gravel, sand, and coarsely powdered char-
coal ; but, if a well is to be dug, it should be carefully
located as remote as possible from every probable source
of contamination ; and, because of the extra hazard, spe-
cial precautions should be used in the way of water-tight
walls to secure filtration through as wide a space as possi-
ble. In a situation like that here described, and such are
frequently to be found, even the degree of care here recom-
mended may not secure perfect immunity ; less than this
is sure to expose health and life to needless hazard. Nor
should it be forgotten that the apparent purity and clear-
ness of water afford no reliable criterion to its freedom
from dangerous contamination. The germs of disease
lurk unsuspected in many a bright and sparkling draught ;
and it is to use very moderate language to say that a very
considerable proportion of the ailments with which human
beings are afflicted arise from the tainted waters which
they drink. Indeed, in most long-settled, highly culti-
vated, and densely peopled districts, the soil becomes so
saturated with organic substances that no comparatively
shallow and open surface-wells can be considered safe.

Driven Wells. — These wells, made by driving down
to a water-bearing bed an iron pipe shod with an iron
point, and pierced with holes around the bottom to admit
the water when it is reached, are practicable in unconsoli-
dated beds of sand, gravel, and clay, where there are no
bowlders to obstruct the driving ; and present some great
advantages over the usual open excavations, not only in
the ease and rapidity with which they may be made, but
in their freedom from risk of contamination from above,

5 8 APPLIED GEOLOGY.

by the access of those surface-supplies of water which are
liable to be loaded with organic impurities. If they reach
to considerable depths, and in their descent pierce through
beds of tough clay, the water that they furnish is likely
to be excellent and reliable. In some of the southward-
reaching valleys of the lakes of central New York, deeply
filled as they are with stratified beds of unconsolidated ma-
terials, wells of this kind are often sunk to depths of from
sixty to more than a hundred feet ; and, in many cases,
the structure of the containing beds causes them to over-
flow at the surface, sometimes with considerable force,
constituting them veritable artesians. The water of these
wells, though sometimes very slightly sulphurous, is ex-
cellent.

Driven wells are feasible only under the conditions
mentioned in the first sentence of this paragraph ; but
there are large areas in the United States where such con-
ditions are presented, and where the driven well would
doubtless yield more wholesome water-supplies than those
furnished by the common surface excavations. The
chances that the water will overflow in any given case
will depend on the conditions presently to be mentioned
as conditioning the outflow from artesian borings.

Artesian Wells. — These wells are essentially borings,
often of very great depth, which penetrate porous water-
bearing strata of moderate dip, confined both above and
below by other strata that are practically water-tight, the
entire series of water-bearing and impervious beds out-
cropping at its elevated edge, often many miles distant
from, and at a considerable elevation above, the points
where borings are made. In some cases the series of
water-bearing beds with their impervious cover form great
basin -shaped depressions, around which their elevated
edges outcrop on all sides, covered only by loose surface
accumulations ; but this kind of structure is by no means
essential to success, provided only that the confined waters

ECONOMIC ASPECTS OF STRUCK

do not find easy egress at some point
down the dip of the strata, or provided
that the porous strata gradually change
their character below the boring, as is
frequently the case, and become prac-
tically water-tight.

In Fig. 1 2, which represents an ideal
section across a basin-formed depres-
sion, i, 2 is a water-bearing sandstone
confined between impervious strata of
shale, 4, 5, and 6, 7 ; and 3 is also a stra-
tum of porous sandstone, which, near
the center of the basin, thins out and
becomes merged in the shale ; while
the dotted line C, D, marks the level
of the opposite edges of the strata. It
is evident that water entering at the
outcropping edges i, 2, and 3 of the
porous beds, and filling them to satu-
ration, will, at any points, as A and B,
be subjected to a pressure equal to
that of a column of water reaching from
the dotted line to the top of the bed at
that point ; and that, if borings be ex-
tended to the water-bearing strata at
these points, the water will overflow
through them with a force proportioned
to the height of the head above the
mouth of the well. Should a boring
be made at D through both water-bear-
ing beds, the water in it would barely
reach the surface, because its mouth
would be on a level with the upper
edges of the beds, while at A the water
would be under a great head, and
would issue with much force. At

60 APPLIED GEOLOGY.

point's between A and D, water would issue with a force
varying from that at A to a mere quiet outflow. From this
it may be seen that the possibility of obtaining water-sup-
plies by artesian borings is entirely dependent on the larger
geological structure of the region ; and that this needs to
be studied by the aid of the best attainable means, to
make success in such necessarily expensive undertakings
anything but a mere lucky chance. A brief review of the
conditions which insure success will render this more obvi-
ous. These are :

1. The existence of porous strata to serve as collectors,
conductors, and reservoirs of the water supplied by the
rainfall of the region. The most reliable water-bearing
beds are usually porous sandstones and conglomerates;
or, where the water is derived from deep accumulations
of uncemented materials, the same substances as sand and
gravel, the materials of ancient beaches. Artesians may
occasionally derive their supplies from fissured and cav-
ernous limestones ; but the chances of striking such water-
pockets are usually too slight to encourage explorations.
The thicker such beds are known to be in the region, and
the more open their texture, the better will be the chances
of success so far as this condition is concerned.

2. An equally essential condition of success is that the
water-bearing strata should be covered and underlaid by
continuous, impervious strata, confining the waters, and pre-
venting their dissipation by percolation either above or
below. The most reliable strata for this purpose are thick
masses of clay or shale ; though compact rocks of other
kinds, when free from fissures, like some limestones, may,
in certain regions, prove useful auxiliaries. The continuity
of impervious cover throughout the entire extent of the
beds, while they retain their character as water-ways, is a
point of great importance.

3. A third essential condition is, that the series of
strata should have a moderate dip from their outcrop to-

ECONOMIC ASPECTS OF STRUCTURE. 6l

ward the point where the boring is proposed. A dip of
one degree, as has been said on a former page, will carry
the strata down about ninety-two feet in a mile, and one of
two degrees one hundred and eighty-five feet per mile.
Hence, any very considerable dip would, in no great dis-
tance from the outcrop, carry the strata beyond the reach
of practical exploration. The table given on pages 46 and
47 will, where the dip is known, aid in estimating approxi-
mately the depth to which the boring must be carried. The
inclination of the beds, as it may carry the outcrop of the
water-bearing strata above the level of the well-mouth, will
cause the water to overflow, or bring it within the reach
of pumps. A deduction, however, of several feet for a
distance of a number of miles, needs always to be made
from the height to which the water might theoretically be
expected to rise, on account of friction, and the resistance
which even the most porous beds oppose to the free flow
of water.

4. A consideration of much importance as regards the
abundance of the water-supply that may be looked for
from any porous beds, and one also which depends on the
amount of dip, is the breadth of absorbing surface which
these beds expose at their outcrop. The breadth of ex-
posure on a level surface of beds one hundred feet thick,
with a dip of one degree, would be a trifle more than a
mile, and for two degrees dip, about half a mile, the breadth
of surface exposure varying inversely as the dip. Hence
a moderate degree of dip will give a greater extent of
gathering-ground, or area of catchment, as it is often termed.

5. A fifth essential condition is, that there shall be no
obstructions to a free flow between the site of the boring
and the outcrop of the water-bearing beds. Such obstruc-
tions may be presented either by faults interrupting the
continuity of the strata and rendering possible springs of
the kind described in a preceding paragraph, or by dikes

of volcanic origin cutting across the strata, and rendering
4

62 APPLIED GEOLOGY.

hopeless any flow below the obstruction, although success
may be achieved above. Fig. 13, in which A represents a
volcanic dike intersecting the water-bearing stratum B,

FIG. 13.— Illustrating effect of an Obstruction. (After Page.)

will illustrate the effect of this kind of obstruction. In
this case, a boring between A and B, as at the point i,
would be likely to succeed, while one below A, as at 2,
would be hopeless. Such obstructions, in regions where
they are likely to occur, are usually not difficult to dis-
cover, and should be sufficient to deter men from under-
takings that are sure to be futile.

6. The last consideration to be mentioned, which is
meteorological rather than geological, has reference to the
usual amount of rainfall which may be depended on to
supply with water the gathering-ground of the porous
strata. In large areas west of the Mississippi, the average
rainfall is but small, yet it may be sufficient, under condi-
tions otherwise favorable, to make artesian borings fairly
successful ; but in all the region east of the Mississippi
the usual annual amount of rainfall is so abundant as to
make the question of sufficient supply, under proper con-
ditions, a reasonable certainty. A rainfall of thirty inches
per annum, which is well within the average rainfall of the
Eastern United States, would supply to the gathering-area
of a hundred-foot stratum, dipping at an angle of one de-
gree, 3,400 barrels of water a year for every foot in width
across the outcrop ; of which, if but one third is taken up
by the stratum, upward of 1,100 barrels per year will be
stored in every foot of its width. Hence the enormous

ECONOMIC ASPECTS OF STRUCTURE. 63

flow from some noted artesians need excite no surprise.
An artesian well in the city of Louisville is said to yield
330,000 gallons every twenty-four hours from a depth of
2,086 feet ; one in the city of Paris, the Crenelle well, dis-
charges over half a million gallons per day, from a depth
of i, 806 feet ; while one, bored by a French engineer in
the Sahara Desert, is said to have yielded at the outset
1,000 gallons per minute, or about 1,500,000 gallons per
day.

The quality of the water yielded by such borings will
naturally depend on the character of the strata which form
the water-ways. In many cases it is very good ; but in oth-
ers the water derived from certain strata is found to be too
heavily charged with mineral substances to be adapted for
domestic use. It is usually difficult to predict the quality
of the water that is likely to be obtained from a given set
of beds ; but a single test is commonly sufficient for a
large district, for these deep-seated water-ways are apt to
underlie extensive regions with strata of a tolerably uni-
form composition.

From what has been said of the structural characters
which are essential conditions of the success of artesian
wells, it may easily be understood that they should not be
undertaken without a careful consideration of the geologi-
cal character of the region. Much indispensable informa-
tion may be gained with regard to the nature, thickness,
order of succession, and dip of the strata, and the direc-
tion of their inclination, by consulting the geological re-
ports and maps published by many of the States, and now
being issued by the United States for the Western States
and Territories. This, supplemented by such local obser-
vations as may be possible, will enable a careful person to
form a judgment as to the probabilities of success in any
given case. To enter upon such undertakings without
such care would be to incur a great and needless hazard.

The student desiring larger information on the impor-

64 APPLIED GEOLOGY.

tant subject of water-supply and artesian wells is referred
to the " Reports of the Geological Survey of New Jersey"
for 1876, 1882, and 1884, the last two of which are espe-
cially valuable ; and to the first volume of the " Geologi-
cal Survey of Wisconsin" (i873~'79), P- 689, from which
Fig. 12 was copied: the second volume of the same re-
port, pp. 149-171, has several interesting sections, show-
ing the conditions under which artesian borings have suc-
ceeded in that State. Also the second "Report of the
Geological Survey of Arkansas," pp. 52-67, has much of
interest on this same topic ; and notices of wells and bor-
ings may be found in many places in the " Final Reports
of the Ohio Geological Survey."

Structure and Drainage.— The matter of effective
drainage, so important for both sanitary and agricultural
purposes, has also its geological aspects, though these may
not in the majority of cases be the chief ones. The neces-
sity for drainage, in not a few cases, arises from causes
purely geological, and in many of these the evil may be
remedied by means suggested by a knowledge of the geo-
logical structure. Fields rendered wet and cold by an
impervious hard-pan may be found capable of ameliora-
tion by the mere use of the subsoil-plow, breaking through
a thin crust to porous beds below. House-drainage on
clay sites may be found practicable by sinking cess-pools
to beds of sand and gravel beneath, in which case it is
well to remember that the water-supply derived from
neighboring wells will naturally be endangered. Districts
may be rendered swampy and malarious by impervious
strata at no great depth below the surface, where the to-
pography of the region is not such as to offer outlets for
drains. In some instances of this kind effectual relief has
been found in the existence of deeper-seated porous or fis-
sured strata, wells sunk to which have furnished the requi-
site outlets for drains. Still other districts have been made
pestilent marshes by the presence of outcrops of rock or

ECONOMIC ASPECTS OF STRUCTURE. 65

tough clay obstructing the natural drainage by streams,
where the removal of such obstacles might reclaim to fer-
tility large tracts of land, with immediate improvement of
the health of the surrounding region. A work of this kind
has recently been completed in New Jersey, while others
are suggested — all justly regarded as legitimately belong-
ing to the geological survey of the State. (See " Geologi-
cal Reports of New Jersey " for 1869, 1870, 1877, and 1884.)
From what has been said in the preceding pages, it
will be apparent that questions of geological structure are
of deep concern to many prominent branches of human
industry ; and that in some matters of paramount im-
portance they touch the interests of nearly every family.
Other highly interesting relations of geological structure
will be more appropriately treated of hereafter, when we
come to consider the mode of occurrence of ore deposits.

CHAPTER V.

MATERIALS OF CONSTRUCTION.

AMONG the many useful substances which the earth's
crust yields for the supply of human wants, the materials
of construction may justly claim a leading place, both on
account of their wide diffusion and their very general and
highly important uses in both architectural and engineer-
ing structures. These, leaving out of view for the present
iron, so largely used in modern structures, as rather an in-
direct than a direct geological contribution to the arts of
construction, are the various kinds of building and or-
namental stones, the brick clays, the mortars, and the
cements.

Building-Stones.— The qualities which fit a building-
stone for its various uses may be conveniently considered
as belonging to two classes : (i) the necessary qualities,
which are obviously strength and durability ; and (2) the
desirable ones, which are facility of working and beauty,
whether of color, texture, or susceptibility of finish. Un-
less a rock has strength sufficient to endure any strains to
which it may probably be subjected, and such powers of
resistance to the usual agencies of decay as to enable it to
withstand them for long periods under the conditions in
which it is to be placed, it is wholly unfit for use in any
important structure. When these essential qualities are
assured, any properties which it may possess that will fa-
cilitate the work of reducing it to desirable forms will

MATERIALS OF CONSTRUCTION. 67

diminish largely the expenses of construction, while what-
ever may make it pleasing to the eye will greatly enhance
its value for architectural purposes and for many orna-
mental uses.

I. Strength. — Let us first consider those properties
on which the strength of stones depends. These are (i)
Closeness and compactness of texture, in virtue of which all
the grains of the stone being closely approximated touch
each other at many points, and thus mutually sustain each
other. Where such grains are large and loosely arranged,
the tendency of strain is to press them more closely to-
gether, and so to tear them loose from their consolidating
means, and when this is done the stone crumbles. (2)
Degree and means of consolidation. The more completely
the consolidating medium enwraps the particles of the
stone and fills all the spaces among them, the stronger it
will be. Some of the porous sandstones and earthy lime-
stones have evidently but a small proportion of cementing
material ; a thin film of clay or of clay and iron oxide, a
minute amount of silica or calcite at the points where the
grains touch each other, seems to be all that holds them
together ; and, in the case of some friable rocks, it would
seem that the particles are consolidated merely by the ad-
hesion of their faces. Such rocks are not likely to have
any great amount of strength, though some of them may
be used for purposes where no considerable strength is
required. Again, among the several consolidating mate-
rials, some like silica have greater inherent firmness than
others, and this they are likely to impart to the stones
which they cement. (3) Hardness and deavability of
grains. It is natural to expect, especially in the case of
crystalline rocks whose grains are held in place by the
interlocking or felting of the crystals, or by the welding
together of their faces, that the intrinsic hardness of the
grains and their susceptibility to cleavage will determine
in a great degree the strength of the rocks. Moreover,

68 APPLIED GEOLOGY.

where cleavable minerals are largely present, the smaller
the size of the grains the more varied will be the direction
which the planes of cleavage will be likely to have within
a given compass, and the less the liability to yield to
crushing from this cause. (4) Direction of strain. The
great majority of bedded rocks offer a decidedly greater
resistance to crushing when the strain is exerted in a di-
rection at right angles to their planes of bedding ; and the
difference in the power of resistance to transverse or par-
allel strains is the greater the more distinctly laminated or
foliated the rock is. This fact affords a good reason why
such stones should always be laid on their natural bed.
(5) Elasticity. The results of experiments recently pub-
lished in the Geological Report of Indiana for 1881, indi-
cate that where weight is to be sustained by stones with
only the ends supported, as in the case of lintels and
beams, elasticity is an important consideration, and that
the elasticity of limestones is probably greater than that of
sandstones or even of granite.

The strength of building-stones is determined by crush-
ing cubes of a given size, usually of two inches edge, in a
press which indicates the amount of force applied, and
then reducing the result to terms of the force exerted on
a square inch of surface. A table of the strength of sev-
eral well-known building-stones, derived chiefly from the
determinations of General Gillmore, is given below, with
the percentage of water absorbed by each. Where the
absorption is given as " very little," as in the marbles and
granites, it is far below one per cent. The extremes of
strength in the stones tested by General Gillmore are : for
granites, from 9,500 pounds to 24,040 pounds ; for mar-
bles, from 7,612 pounds to 20,025 pounds ; for limestones,
from 3,450 pounds in a Caen freestone to 25,000 pounds ;
and for sandstones, from 4,250 pounds in a stone which
absorbed nearly seven per cent of water to 17,250 pounds
in No. ii of the following table. It will be seen from

MATERIALS OF CONSTRUCTION.

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;0 APPLIED GEOLOGY.

this table that, in the uncrystalline rocks, the limestones
and sandstones, there is an obvious relation between the
ultimate strength and the porosity as shown by amount of
water absorbed, the more porous being generally the weak-
est, and where deviations from this occur they are prob-
ably due to differences in degree and means of consolida-
tion.

2. Durability. — The durability of building-stones de-
pends chiefly on certain assignable properties inherent in
the rock ; but it is affected also in a very considerable
degree by the conditions to which the stone is subjected.
These are now to be considered. The inherent qualities
which condition the durability of building-stones are the
following: (i) Sufficient consolidation. This quality of a
proper degree of firmness is a condition as well of dura-
bility as of strength. A slightly cemented stone, though
sometimes a favorite for certain uses, because of the ease
with which it may be worked, is peculiarly liable to mis-
haps in the somewhat rough usage to which stones in
structures are likely to be subjected in the course of years.
Accidental blows mar it or break fragments from its an-
gles and edges ; slight inequalities of pressure cause it to
crack and crumble ; and mere attrition, in places exposed
to the contact of men and animals, or even to the force
of wind-blown sand and dust, may slowly remove particles
from its surface. All this, too, even though its lack of
firm consolidation should not be correlated, as it is quite
sure to be, with the lack of a second requisite of durability
now to be mentioned. (2) Density \ or closeness of texture.
In a dense or compact stone, the cementing material, what-
ever it may be, is present in sufficient quantity to fill en-
tirely the space between its grains ; or, if it is of crystal-
line character, its crystals are so interlocked as to leave
no vacant spaces. Density is shown by the relative im-
perviousness of a stone to water, and from this arises its
importance as a condition of durability. Water is the

MATERIALS OF CONSTRUCTION. ^

chief medium through which the chemical agencies of de-
cay in rocks gain access to their pores ; and though proba-
bly no mineral substance is wholly impermeable to water,
still, if the texture of a building-stone is close, the change
from this cause will be very slow. The exclusion of water
from the interior of a rock is even more important where
the climate is liable to extreme cold, because of the violent
rending effects due to the expansion of water in freezing.
Water, in freezing, expands about nine per cent, with a
force sufficient to tear asunder the grains of a stone with-
in which it finds lodgment, and so causes its surface to
crumble, or its laminae to separate. Were it not that a
marked degree of porosity in a stone promotes also rapid
drying, and permits a considerable portion of the expan-
sive force to be expended otherwise than in pushing apart
the grains of the stone, the disaggregating effects arising
from this cause would doubtless be greater and more rapid
than they are ; but, in any case, a very porous stone
should have given undoubted proofs of durability before
being used in important structures, where it must be ex-
posed to the vicissitudes of a highly variable climate, like
that of the Northern United States. (3) Fineness and
uniformity in size of grains. It is undoubted that this
quality exerts a decided influence upon the durability of
building-stones ; due, probably, in a considerable degree,
to the weakening effect of large and irregular-sized grains
which offer unequal resistance to pressure at different
points ; but it can hardly be doubted that, in a rock com-
posed of two or more minerals, and exposed to great and
sudden changes of temperature, the inequalities in the ra-
tio of expansion of the constituent minerals must cause a
tendency to disaggregation, which will be heightened by an
increase in the size or in the inequality of the grains, and
which will be likely to be reduced to a minimum when the
grains are small and of uniform size. (4) Freedom from in-
jurious minerals. It is obvious that the presence in a build-

72 APPLIED GEOLOGY.

ing-stone of any substance which is subject to decomposition
when exposed to the weather, will seriously affect its dura-
bility. Of such substances pyrites is one of the most dan-
gerous and yet widely diffused. Where it occurs lining
seams, or in nodules and crystals of some size, its decompo-
sition leaves unseemly holes and crevices, and gives the stone
a disagreeable stain. Where it is disseminated in minute,
almost imperceptible grains, it is often even more dele-
terious, since its ultimate decomposition produces a wide-
spread disaggregation of the stone. So, too, iron carbon-
ates and other protoxide compounds of iron are injurious
to the rocks, chiefly bluish or greenish gray sandstones, in
which they occur, through their tendency to pass to a higher
state of oxidation. Many reddish and brown sandstones
show little durability, and this is commonly attributed to
the iron oxide, which acts as a coloring agent and also as
a cement ; though it is quite possible that the lack of dura-
bility may be due quite as much to the superabundant
clayey matter which is apt to be also present in such
rocks. Clay, which when present uniformly disseminated
through a stone, to the amount of but a few hundredths
of the mass, as in many limestones and sandstones, is
rather beneficial than injurious, where it occurs in too
great abundance, forming seams in sandstones or knots and
irregular crevice-fillings in limestones, becomes a source
of serious injury, not only by its own ready disintegra-
tion under atmospheric agencies, but also, through the
tenacity with which it retains any water that it may take
up, offering occasion for the destructive action of frost on
the surrounding stone. Especially when a rock is some-
what porous, clayey matter, by its retentiveness for moist-
ure, may become very destructive in severe climates, as
has been suggested above in the case of brown sandstones.
But, besides those conditions affecting the durability
of building-stones which are inherent in them, there are
others which arise from the circumstances under which

MATERIALS OF CONSTRUCTION. 73

they are used in structures : (i) The great majority of the
bedded rocks are most durable when laid upon their natu-
ral beds, that is, with their edges exposed. This is due,
not merely to the fact that most such stones are thus laid
in the position in which they are strongest, as has been
stated in a preceding paragraph, but also to this, that the
planes of bedding in rocks which are in any degree po-
rous are naturally also the planes of easiest penetration for
water. Hence, when they are set with the planes of bed-
ding vertical, water soaks into them most freely, and the
exposed surface is apt to show a disposition to crumble off
in grains, or even, where they are distinctly laminated, to
peel off in flakes, mostly from the effects of freezing ;
whereas, when laid with the edges exposed, they admit
water much less readily. (2) Stones, when used in con-
structions, are doubtless much less affected by the solvent
action of water than when they are in their native beds,
for they are then no longer exposed to its constant perme-
ation, and to the attacks of those chemical agents with
which water is apt to become charged in passing through
the soil. Yet it is believed, and apparently with good rea-
son, that in great cities, the rains and fogs, charged with the
sulphurous gases which the consumption of coal furnishes
to the atmosphere, become active agents of destruction to
some classes of building-stones, especially magnesian lime-
stones. To this is attributed the rapid deterioration of the
magnesian limestone used in constructing the new Houses
of Parliament in London, a material which had endured for
centuries in ancient structures, very little affected by the
pure air of the country. (3) Again, building-stones, while
conducting heat very slowly, are yet subject to expansion
and contraction from variations of temperature. Experi-
ments on the linear expansion of granite, limestone, and
sandstone, conducted in 1832, under the direction of Gen-
eral Totten, the results of which were published in vol.
xxii of "American Journal of Science," showed that a fine-

74 APPLIED GEOLOGY.

grained granite varied .000004825 of its length for a change
of i° Fahr., that white, fine-grained, crystalline limestone
from Sing Sing, N. Y., varied .000005668, and that a some-
what coarse-grained red sandstone from Chatham, Conn.,
varied .00000944, or nearly twice as much as granite. Eng-
lish experiments, quoted by Geikie in his " Text-Book of
Geology," show that gray Aberdeen granite has nearly the
same rate of variation (.00000438) as the above, and white
Sicilian marble a somewhat greater rate (.00000613) than
the above stone of the same class ; while a Welsh slate va-
ried .00000576 for i° Fahr. Hence, in a climate of great
and sudden variations of temperature, the difference of
temperature and of consequent tension between the inter-
nal and external portions of a building-stone, and between
its surfaces differently exposed to heat and cold, must sub-
ject it to a severe and often-recurring strain, to which it
must eventually yield. Livingstone says, in his " Travels
in South Africa," that the rocks in those tropical regions
are exposed to so great variations of temperature between
day and night, that fragments, varying in weight from a
few ounces to upward of a hundred pounds, split and fly
off. It can hardly be doubted that, in a climate like that
of the Northern United States, this cause of dilapidation
must seriously affect the ultimate durability of building-
stones ; and that, if the sandstone tested by General Tot-
ten shows even approximately the relative variation of
sandstones under temperature changes, they may be ex-
pected to be most affected by this agency. Doubtless,
also, those stones which possess the highest degree of elas-
ticity, which has been referred to on a preceding page,
may be expected to resist most successfully great extremes
of heat and cold. The expansion and contraction of
stones in structures naturally has an unfavorable effect on
the tightness of joints and the adhesion of mortars and ce-
ments. Besides what has just been said, investigations
prosecuted chiefly by German physicists on the ratios of

MATERIALS OF CONSTRUCTION. 75

expansion of several of the most important rock-forming
minerals, like quartz, orthoclase, hornblende, and calcite,*
have revealed in them marked differences in expansibility
by heat, a fact which shows that the movements which
must take place among the constituents of a rock com-
posed of two or more minerals, when exposed to consider-
able variations of temperature, may be expected ultimately
to lead to its gradual disaggregation. This fact will also
explain the well-known tendency of granite, one of these
composite rocks, to burst in pieces when exposed to the
heat of conflagrations, though, in this case, something is
probably due also to differences of temperature in differ-
ent parts of the stone. (4) Prof. James Hall, in his excel-
lent " Report on Building-Stones," calls attention also to
the effects produced on stones by the growth of lichens
in the small surface inequalities, thus affording a lodg-
ment for dust, and detaining moisture to act slowly on the
surface.

Beauty of Building and Ornamental Stones. —
In the choice of stones designed for architectural uses,
those qualities that please the eye naturally exert a great
influence on the estimate in which they are held. Much
depends, of course, on individual tastes, and something
on the currents of fashion ; but in the matter of color,
the neutral tints, the grays, the buffs, and drabs, usually
please longest ; the reddish browns are also pleasing tints
and largely sought after ; but great care is needed in the
selection of stone of this color, since experience has shown
that it is liable to disintegrate from the influence of its ce-
menting material. Dark colors give a heavy and somber
appearance to buildings, which may be judiciously relieved
by the use of light trimmings. White is glaring and painful
to the eye in the blazing sunshine of American climates,
and is besides apt to become soiled and dingy in the at-

* " Constants of Nature," Part III, " Smithsonian Miscellaneous
Publications."

76 APPLIED GEOLOGY.

mosphere of cities, especially if the stone is somewhat
porous. This remark is also true of many neutral-tinted
porous sandstones. In the selection of colors, it is also a
matter of much interest, by the observation of long-exposed
outcrops, to note the tint which the stone may be expect-
ed to acquire by weathering, since some stones which are
pleasing when recently quarried, become, when long ex-
posed, of a dead and disagreeable hue. Besides mere
color, certain qualities of texture which adapt a stone to
receive a fine finish, like some sandstones and earthy
limestones, or to develop by polishing a beautiful surface
or a pleasing variety of figures and colors, like some fos-
siliferous limestones, marbles, granites, and porphyries,
place the stones which possess them in the category of
ornamental materials ; and some stones, like the highly
esteemed Caen stone, may be judiciously chosen for pur-
poses of interior decoration which would be perishable if
exposed to the weather.

Facility of Working.— This is a quality of very
considerable importance in a building-stone when it can
be secured without a sacrifice of the essentials of sufficient
strength and durability, for on this depends in a large de-
gree the expense of construction. Indeed, the ultimate
durability of important structures is not unfrequently over-
looked in the effort to diminish present expense, and fa-
cility of working becomes a controlling rather than a sub-
ordinate consideration in determining the choice of a
stone. The ease with which a stone may be wrought into
desired forms depends : (i) On the hardness of its con-
stituent minerals and the means by which they are ce-
mented. Thus the granites and the silicious sandstones
and limestones are, as a class, more difficult to dress than
the nearly pure granular limestones and the sandstones of
somewhat open texture, or those whose chief cementing
material is a small amount of thoroughly disseminated
clay. (2) A second condition, adapting a stone to the

MATERIALS OF CONSTRUCTION. 77

mode in which it is desirable that it should be worked, is
often presented by its structure and mode of fracture.
Thus, a laminated or foliated structure is a very important
aid in reducing a stone to the desired thickness, to which
if a tendency to a somewhat even cross-fracture be added,
a hard stone may be dressed at reasonable expense. So,
too, a conchoidal fracture facilitates the labor of the work-
man in dressing a stone for a rough-faced wall ; while,
where fine carving and delicate tracery are intended, the
stone should be without brittleness, and should possess
that complete homogeneity of both structure and texture
which will adapt it to being cut with equal ease in any di-
rection, and which is an essential character of the class
called freestones, whether silicious or calcareous.

As is well known, all stones are more easily dressed
when but recently removed from the quarry, as the surface
hardens somewhat on exposure to the air, and in some
cases in a very marked degree.

The manner in which a building - stone should be
dressed is a matter chiefly technical, belonging to the archi-
tect and stone-cutter ; but from one point of view it has
a geological bearing, since upon it depend in a considerable
degree the strength and durability of the stone. A mode
of dressing which attacks the stone by blows directed
against its face affects injuriously both its strength and
durability. General Gillmore's experiments on the strength
of granites showed that polished cubes were on an average
twenty-five per cent stronger than cubes of the same stone
that had been reduced to size by dressing ; and experi-
ments instituted in Indiana, on the oolitic limestone se-
lected for the State Capitol, showed a difference of more than
one third in strength and nearly one half in elasticity be-
tween sawed and tool-dressed stone. Nor should this seem
surprising when we consider that any stone may be broken
by repeated blows along a definite line. The effect of the
blows directed against the stone is to weaken or destroy

78 APPLIED GEOLOGY.

the cohesion of all the grains to which the jar is communi-
cated. In like manner such blows crush the surface and
measurably loosen the cementation of the stone for some
distance inward, giving easier admission to water, and thus
lessening its durability.

Selection of Building-Stones. — In the selection of
a stone for construction, attention should be paid first of
all to its durability^ for, when this is made sure, sufficient
strength will rarely be wanting. In the examination need-
ful for this, while careful heed should be given to the quali-
ties and conditions which have been enumerated as those
on which durability depends, the most helpful and reli-
able indications may be obtained by observing the manner
in which the stone has endured the weather in old struct-
ures, and especially its condition in its natural outcrops.
If in these exposures the edges and angles of the stone re-
main sharp — if its surface shows no signs of flaking or
crumbling, no cracks nor holes where pyrites or clay has
lurked, nor dark stains from the change of iron compounds
— it may be relied upon for structures if proper care is
used to reject suspicious blocks ; but if a contrary state
of things be revealed by such an examination, and if in
old natural exposures the edges of the stone are furrowed
by unequal weathering, while heaps of crumbled material
are piled at the base of the cliff, the stone should be re-
jected. It is well to remember, however, in examining
natural exposures, that some argillaceous sandstones, which
are very durable if properly dried before being exposed to
freezing, split up on their planes of lamination from the
action of frost on their quarry-water in exposed cliffs, and
that in their case the examination should be extended to
determining whether the splitting reveals any gathering of
the clay in seams.

As regards strength, a very large margin for safety is
always allowed over the force needed to crush the stone,
and it is probably very rare that a building-stone is sub-

MATERIALS OF CONSTRUCTION. 79

jected to even one twentieth of the load under which it
would be likely to yield. The extreme pressure on stone
in a wall fifty feet high is from fifty to sixty-five pounds
per square inch. In a tower of stone two hundred feet in
height, the strain at the base would be from two hundred
to two hundred and fifty pounds per square inch, about
one fourteenth the strength of the weakest stone given in
the table on a preceding page.

Attention has already been directed to the error of se-
lecting a stone for its beauty rather than for its durability.
It should also be borne in mind that pleasing effects may
be produced with a stone of a somber color by the judicious
use of light-colored materials for trimmings, while even
the more agreeable tints lose much of their effect if unre-
lieved by contrasting colors.

By attention to the suggestions already given, stone of
a reasonable degree of facility in dressing may be secured
in many localities ; and it is well to bear in mind that the
harder kinds of rocks commonly produce their best effects
in buildings when rough dressed, and so with a minimum
of expense in working. When elaborate ornamentation is
proposed, the question is usually one of fitness of materials
rather than of expense.

After all, in the majority of cases where stone is used
in constructions, local supplies must be the chief depend-
ence, on account of the great expense of transportation ;
and the suggestions here made are intended mainly to aid
in the selection of the best materials from the supplies
afforded by the rocks which may exist in the vicinity.
Many stones also may do fairly well for cellars and foun-
dations, where they are not exposed, which, from various
causes, would not be durable if exposed to the weather ;
and others may serve a useful purpose in rough construc-
tions, like bridge-abutments, retaining walls, and under-
pinnings of farm-buildings, which from their coarseness
of texture, their faults of color, or their hardness and ir-

8o APPLIED GEOLOGY.

regular fracture, would be unsuited for a better class of
structures. Indeed, many regions may furnish materials
for these wide-reaching and very essential uses, which
would yield none suitable for higher purposes.

North American Building-Stones. — A general
idea of the relative amounts of the several classes of build-
ing-stones that are used in the United States from impor-
tant quarries may be gained by observing the production
reported in the census returns for 1880. The number of
cubic feet of marketable stone reported was over 115,000,-
ooo. Of this, considerably more than a half, or 65,500,-
ooo cubic feet, was limestone and marble ; a little less
than 25,000,000, sandstone ; about 20,500,000, granite and
other crystalline rocks of the same class ; while the slate
product was somewhat more than 4,500,000 cubic feet.
These amounts would be largely increased, could the local
supplies derived from numerous small quarries be known ;
but it is not likely that the relative amounts of the sev-
eral stones would be materially changed. Hence it would
seem that limestones and marbles are much more largely
used than any other class of building-stone — a fact which
is due, partly to their wide distribution, and partly to the
comparative ease with which they may be dressed.

A general view may also be obtained of the distribution
of building-stones of special value, by observing the States
reporting the largest production of the several classes.
Thus, in the production of limestones, Illinois leads in
amount, followed by Ohio, Iowa, Indiana, Missouri, and
Wisconsin, in the order named ; while Vermont, which
stands twelfth in amount of product, leads the list in point
of value, her product of about 1,200,000 cubic feet, chiefly
marble, being worth somewhat more than the 13,000,000
cubic feet of Illinois limestone. In sandstone, Ohio ranks
first in both amount and value, Pennsylvania second in
amount, New York third, New Jersey fourth, and Con-
necticut fifth. In stones of the granite class, Massachu-

MATERIALS OF CONSTRUCTION. 8 1

setts ranks first in amount and value of product, followed
in order of value by Maine, Rhode Island, Connecticut,
Virginia, and New Hampshire ; while in the production
of slate, Pennsylvania is foremost, yielding, with Vermont,
over 83 per cent of the total product, minor amounts
being supplied by Maine, New York, Maryland, and Vir-
ginia.

It will be seen from this that the production of gran-
ite, slate, and marble is chiefly confined to the Appalachian
belt from Maine to Georgia — Colorado and California also
producing small amounts ; that the greatest limestone pro-
duction is from the north central group of States ; while
the chief supplies of merchantable sandstones are, at pres-
ent, derived from the region between these areas. A brief
review of the geological distribution of the various classes
of building-stones will not only reveal the reason for this
grouping of productive areas, but will also be likely to
suggest additional areas whence valuable building mate-
rials for both local use and commercial distribution may
be derived, as the progress of settlement and the supply
of easy means of transportation encourage their develop-
ment.

Geological Position of Granitic Rocks. — The
oldest rocks on this continent are found occupying much
of British America, in a great V-shaped area with the
point near the eastern end of Lake Ontario, extending
into Labrador with its shorter branch, which covers most
of the explored region north of the St. Lawrence, and
with its longer branch skirting the north sides of Lakes
Huron and Superior, and stretching away northward
to the Arctic Ocean. From the point of the V, these
rocks extend across the St. Lawrence at the Thousand
Islands, and occupy a large area in northeastern New
York — the well-known Adirondack wilderness. Rocks of
similar character, but a portion of which are probably of
somewhat later age, occupy parts of Nova Scotia and

82 APPLIED GEOLOGY.

New Brunswick, most of New England, the southeast cor-
ner of New York and northwestern New Jersey, and
extend along the Appalachian range through Virginia,
North and South Carolina, and Georgia, into eastern Ala-
bama. These most ancient rocks also occupy a large part
of northern Michigan, cover much of northern Wisconsin
'and Minnesota, and are extensively developed in the
Rocky Mountains, the Wahsatch, the Sierra Nevada, and
in many parts of the ranges of the Great Basin. This
very ancient series of deposits, called the Archaean or
Azoic, consists wholly of crystalline rocks of various kinds,
arranged in rude beds, showing that they were once or-
dinary sediments which owe their present condition to
metamorphism ; and they have been penetrated in many
places by vast masses of granite which have been thrust
through them in a plastic state. Granitic rocks of several
kinds form some of the series of beds also, as well as oc-
casional crystalline limestones that furnish marbles. In
the areas, chiefly Archaean, then, which have been de-
scribed above, and in a few other limited exposures that
have not been mentioned, but which lift themselves like
islands from the midst of the newer rocks that surround
them, and in these only, may we expect to find building-
stones of the granitic class — the granites, the syenites, the
gneisses, and the highly silicious schists. In several parts
of these areas, rock of this class is now quarried in large
amounts ; in many others stone of fine quality and great
beauty is known to exist, though not yet worked ; and
doubtless building-stone of equal merit will be found in
many other localities not yet explored. Considerable
amounts are already quarried in Colorado, and in Cali-
fornia on the line of the Central Pacific Railroad. Be-
sides our domestic supplies, considerable amounts are
imported for monumental and ornamental uses, especial-
ly from Aberdeen and Peterhead in eastern Scotland.
These rocks, composed of two or more of the minerals

MATERIALS OF CONSTRUCTION. 83

quartz, feldspar, hornblende, and mica, are as a class very
durable, though some of them, in which feldspar is largely
present and has microscopic pores, giving easier admission
to water, weather somewhat rapidly. Pyrites should also
be guarded against, in these as in other rocks, for it is
sure to impair their durability. Where the constituents
are very coarsely crystalline also, the rock is unfit for
building purposes. Those granitic rocks which are com-
posed of quartz and feldspar, or quartz, feldspar, and horn-
blende, with mica in small proportion, if present at all, and
with the ingredients in small or moderate-sized grains, are
the best. These rocks are harder than the other classes of
building-stones ; but most, and perhaps all of them, split
with comparative readiness in one direction, called by the
workmen the rift, and break most easily at right angles to
the rift, thus making the dressing easier. They vary much
in color, according to the color and proportions of their
constituents, those composed chiefly of quartz and light-
colored feldspars, with but little black mica, being of a gray
or grayish-white color ; those containing much reddish
feldspar are reddish, and often very ornamental ; while
hornblende imparts to granites and syenite its own dark
hue, as in some of the Quincy granites. Many of the gran-
ites are susceptible of a high polish, and are on this account
considerably used for internal ornamentation in expensive
buildings, as also for monumental purposes. Where the
feldspar in a granite occurs in well-formed crystals of
pleasing color, as in the so-called shap of Cumberland in
England, it increases its value for ornamental purposes.
Granites of this character can doubtless be obtained also
at some localities in this country. Besides the silicious
building-stones here described, trachyte, a volcanic rock
composed chiefly of feldspar, is said to be used as a build-
ing-stone at Virginia City, in Nevada ; and porphyry, an-
other volcanic rock containing crystals of feldspar imbed-
ded in a fine-grained matrix, chiefly of feldspar, with some

84 APPLIED GEOLOGY.

hornblende or augite, though little suited for building, has
long been used for ornamental purposes, for which some
kinds have an ancient and deserved celebrity. Handsome
porphyry is reported to be found in Grenville, Province
of Ontario.

Geological Position and Localities of Marble
and Slate. — Although the crystalline marbles and slates
are chiefly derived from Silurian rocks, later in age than
those from which the granitic building-stones are obtained,
still their local distribution, and in some cases their geo-
logical position, is so closely related to these that they
may conveniently be considered in this place. Excellent
roofing-slates are quarried near Huron Bay, in northern
Michigan, from rocks of the later Archaean, and others, it
is said, in Minnesota, probably from rocks of the same
age. Likewise the first " Annual Report on Mineral Sta-
tistics of Michigan, 187 7-^ 8," states that desirable mar-
bles may be obtained from the Archaean, not far from
Marquette. So also the Archaean limestones of eastern
Canada, at a number of localities, yield marbles suited
for building and ornament, though these limestones are
apt to be too much contaminated with various minerals,
or too coarsely crystalline, to be desirable for such pur-
poses. But the metamorphic rocks of the Lower Silurian,
stretching along the east side of the Archaean in eastern
Canada, Vermont, and southeastern New York, and along
the same range in west Massachusetts and Connecticut,
furnish the chief present supplies of handsome marbles
for building and for ornamental uses ; and in some locali-
ties the marble is veined with serpentine, making an es-
teemed ornamental stone called verd-antique marble. The
serpentinous limestones of the Canadian Archaean can also
yield supplies of this stone at some localities ; while beau-
tiful serpentines occur in Wake County, North Carolina,
and in some of the western counties of that State. The
Lower Silurian rocks of East Tennessee likewise yield

MATERIALS OF CONSTRUCTION. 85

highly esteemed marbles of various colors, which are ex-
ported chiefly from Hawkins and Knox Counties, though
several other counties near the western base of the Appa-
lachians can, it is said, furnish stone of equal beauty. The
colored marbles for the interior decoration of the Capitol
extension in Washington were obtained from Hawkins
County, while that which was used in the construction of
the building was dolomitic marble from Lee, Mass. Beau-
tiful marbles are also reported from the western part of
North Carolina, and a recent display (1883) of some of
these in Boston attracted much attention.

Cleavable slates are obtained from argillaceous rocks
that have been folded and subjected to great pressure,
thus rendering them very compact, and developing in
them a tendency to cleave at various angles with the origi-
nal bedding-planes. The largest supplies are derived, as
has already been stated, from Pennsylvania and Vermont.
The slate region of eastern Pennsylvania is along the
southeast base of the Appalachians, the chief quarries
being in Lehigh and Northampton Counties, the adjacent
part of New Jersey also furnishing some, and in Lancaster
and York Counties. The remaining States mentioned be-
fore as furnishing slates yield them under similar geo-
logical conditions in regions where the rocks have been
much disturbed and folded. It is quite probable that
other localities of good roofing-slates will be found in the
disturbed regions along the Appalachians, the Rocky
Mountains, and the Sierra Nevadas. Indeed, slates are
said to be already obtained in California near the base of
the last-named range. The best British supplies of slate
are obtained from the folded rocks of the Lower Silurian
in northern Wales.

Slate should be susceptible of being split easily into
thin, even plates ; should be free from seams and strings
of quartz, which interrupt the cleavage, and from crystals
of pyrites, which would be likely to weather out, leaving

86 APPLIED GEOLOGY.

holes, and should be so firmly compacted as to endure
weathering without change. The softer cleavable beds,
which, though sound, would not endure exposure to the
weather, are wrought into school-slates and tablets.

Among the crystalline marbles, the very fine-grained
and homogeneous kinds are the best, and have a high de-
gree of durability, save possibly in moist climates. Those
of coarse grain and friable texture, or those contaminated
with foreign minerals, or containing soft spots of " talc-like
mineral," are not only difficult to polish, but are apt to
endure exposure to the weather badly. The older stones
in cemeteries long occupied afford convenient opportu-
nities for observing the behavior of marbles under ex-
posure.

Besides the true marbles of crystalline texture, some
compact limestones of pleasing and varied colors, fre-
quently owing much of their beauty to sections of fossils
contained in them, are polished and used for ornamental
marbles. Of this kind is the marble from East Tennessee,
mentioned above (Safford).

Besides our domestic supplies, considerable amounts
of very fine marble are imported from Italy, chiefly from
Carrara in, the Apennines. Greece is also famous for fine
statuary marble from the island of Paros, and from Mounts
Pentelicus and Hymettus.

Sandstones and Limestones. — In studying the
geological relations and topographical distribution of the
two remaining and very important classes of building-
stones, the sandstones and limestones, it will be helpful to
remember that in the vicinity of the great Archaean re-
gions, described in a preceding paragraph, which consti-
tuted the land areas of succeeding geological ages, and
which directly or indirectly furnished the ground-up or
dissolved materials of all later rocks, the chief strata are
mechanical sediments — sandstones and shales — the lime-
stone bands, important though they are, forming but sub-

MATERIALS OF CONSTRUCTION. 87

ordinate parts of the great thickness of strata. On the
other hand, the area now occupied by the great central
group of States, from central Ohio westward into Kansas,
seems to have been a vast interior sea of no great depth, in
which chiefly limestones were formed through the agency
of corals and other sea creatures ; sandstones and shales
being here but subordinate members in the series of strata.
While, therefore, limestones furnish the chief building ma-
terials of the latter region, sandstones are the chief ma-
terials of the former — Ohio, which lies between the two,
furnishing excellent varieties of both kinds of stone from
her eastern and western sections, being the foremost pro-
ducer of desirable sandstones, and second to but one State
in amount of limestone quarried. In the first-named
area, sandstone is furnished from several geological hori-
zons, and at very numerous localities. The lowest un-
changed formation, the Potsdam, affords much good stone
of red and light gray colors, across the northern parts of New
York and the adjacent portions of Canada ; and it borders
nearly the entire south shore of Lake Superior with sand-
stone of a brown color, which at Marquette, Mich., and
Fond du Lac, Minn., is quarried, yielding an admired
building-stone, and which will doubtless afford stone of
equal quality at many other points along this shore. South
of the Archaean, in central Wisconsin and Minnesota, this
formation covers large areas, but furnishes little good
building-stone, being usually too friable. The two suc-
ceeding periods offer, in parts of the Quebec and Hudson
River groups, sandstones usually argillaceous, and suitable
for flagging and for foundation-walls ; the former chiefly in
eastern Canada, the latter across New York from Oswego
eastward. Next in ascending order, the Medina sand-
stone, along the south shore of Lake Ontario, yields, in
one of its members, a usually hard but excellent sandstone
of light gray and reddish-brown colors, which is largely
quarried west of Rochester at Albion, Medina, Lockport,

88 APPLIED GEOLOGY.

and'Other places, and is widely used both for buildings
and for paving, promising great durability where carefully
selected. The same geological formation in Canada,
where it is called the "Gray Band," stretches across the
Province of Ontario from Queenstown to Collingwood, and
yields an excellent building-stone wherever it has been
quarried. In the southern counties of New York, and in
northern Pennsylvania, the Portage and Chemung groups
yield, in many places and at various horizons, beds of
dark gray,~olive, and dark brown argillaceous sandstones,
suitable for all ordinary building purposes, though of some-
what somber colors unless properly relieved by trimmings.
Like all argillaceous sandstones, they need careful selec-
tion to avoid blocks containing seams of clay which soon
disintegrate ; but when properly selected, and seasoned be-
fore being exposed to frost, they give promise of great du-
rability. The Sub-carboniferous yields, in parts of Pennsyl-
vania and in eastern Ohio, beds of good sandstone, which
in Ohio is the fine silicious freestone so largely quarried
in the vicinity of Cleveland for ornamental building-stone,
for grindstones, and for sawed flagging. It is easy to work,
takes a fine surface, and is susceptible of delicate carving ;
and though very porous, seems, from its purely silicious
character, to promise a good degree of durability. Along
the Atlantic slope of the Appalachians, apparently filling
long, narrow valleys formed by their folding, and running
parallel with them, are found thick deposits of sandstone
and shale of earlier Mesozoic age, in the Connecticut River
Valley, and stretching across New Jersey, Pennsylvania,
Virginia, and North Carolina. These deposits furnish, at
many places, beds of a handsome brown freestone, easily
worked, but not usually very durable. This freestone is
largely quarried in Connecticut and New Jersey for use
in New York and other cities. Deposits of similar and
somewhat later age are extensively developed along the
eastward side of the Rocky Mountains, in the so-called

MATERIALS OF CONSTRUCTIO.

" hog-backs " of Colorado and Wyoming, where t
capable of furnishing excellent freestones of various agree-
able shades of color. These freestones are already quar-
ried at two or three points, notably at Morrison in the
vicinity of Denver, for use in the public buildings of that
city. California is also said to have, at several points,
useful sandstones in the later geological formations, as well
as an abundance of handsome marbles and limestones.

The precautions that should be observed in selecting
sandstones for exposed parts of constructions 'are chiefly
these : to choose the more purely silicious, and those of
finer and closer texture ; to avoid those containing pyrites,
a large proportion of clayey matter, or seams of clay ; to
be suspicious of those in which a dark reddish coloring-
matter is a principal means of consolidation ; and, among
porous sandstones, to select only those of proved dura-
bility, since, though some porous sandstones of purely sili-
cious character are very durable, the durability of stone in
general is inversely proportioned to its porosity.

Like the sandstones, the limestones, in the region bor-
dering the Archaean, occur at certain geological horizons
only, and even in the great central limestone area the
stone which has been found to be adapted to the higher
class of uses in construction is found mainly in a few geo-
logical formations. The lowest geological period which
affords good limestones is the Canadian, which in its low-
est group, called the Calciferous, furnishes in Minnesota
the desirable stone quarried chiefly at Frontenac, Kasota,
and Mankato, and in southeastern Missouri forms the
magnesian limestone beds. The uppermost group of the
same period, called the Chazy, furnishes a limestone which
is quarried at many points in the northeast corner of New
York and the adjacent parts of Canada, yielding an es-
teemed building-stone. The Trenton limestone, which
extends across New York just north of the Mohawk River,
and passes northwestward through Herkimer County into

APPLIED GEOLOGY.

St. Lawrence, is quarried at many places, yielding a gray
and a dark-blue stone, and in eastern Canada it furnishes
most of the building-stone used in Montreal and much of
that which is used in Quebec. The limestones of the
same formation, which occupy a large part of southern
Wisconsin, are too much interlaminated with clay to yield
much good building-stone ; but in Minnesota the upper
beds are said to be free from clay-seams, and to be capable
of furnishing reliable stone. The best limestones of Wis-
consin are obtained from rocks of the Niagara period,
which stretch along Lake Michigan in the eastern part of
the State, and furnish an excellent building-stone at many
points. Limestone of the same age is largely quarried in
several parts of Illinois, furnishing the Joliet stone and
Athens marble, in southeastern Indiana and in southwest-
ern Ohio, yielding in the latter State the highly valued
Dayton stone, as well as that obtained at Springfield and
other places. The higher strata of this formation are also
quarried in the western part of New York, at Lockport
and other places ; and, in the Province of Ontario, these
beds, extending northwestward from Niagara Falls to
Lake Huron, are capable of furnishing an excellent mag-
nesian limestone at many points. In ascending order,
the Lower Helderberg period is composed of limestones
which have their chief development in eastern New York,
where the lower members are quarried for local use from
Schoharie County westward to Oneida County. The Cor-
niferous limestone which succeeds this is of great extent
and importance, stretching across New York from near
Albany to Buffalo and thence across the Province of On-
tario, and sending a branch down through the Lake Erie
islands and central Ohio to a considerable distance south
of Columbus, a second branch being found farther west in
the same State. Throughout this wide extent it is quar-
ried at many points for both building-stone and for lime,
yielding, where free from quartz-nodules, with which some

MATERIALS OF CONSTRUCTION. 91

of its beds are thickly set, a strong and durable stone.
This is the last of the limestones of the eastern division of
States which is much used for building purposes. The
Tully limestone of the upper part of the Hamilton period
is confined to central New York, and can be used only for
rough work, while the beds of limestone that occur in the
coal-measures of Pennsylvania seem to be little used for
construction. In the Western States it is different, for
there the Sub-carboniferous limestones afford excellent
building materials in Indiana, Illinois, Missouri, and Iowa,
though in the last-named State the best supplies of build-
ing-stone are obtained from rocks of the Niagara period.
In the Sub-carboniferous of Indiana, beds of highly es-
teemed oolitic limestone are largely quarried in several
counties, extending from Montgomery County southward
to Harrison, and this stone has been used in many im-
portant buildings, among which is the new State Capitol of
Indiana. The same formation yields good building-stone
at three different horizons in Illinois and at two in Mis-
souri,

Although the limestones most highly esteemed and
most widely used for construction in England, France,
and southern Europe are obtained largely from forma-
tions younger than those named above, viz., the Permian,
the Jurassic, and the earlier Tertiary, it is not known that
any younger than the Carboniferous have yet been consid-
erably used in this country.

In the ranges that have been described, limestones
suitable for buildings can by no means be found in all
places where the formations are exposed, for limestones,
like other formations, are apt to present important differ-
ences at different exposures. In some places their bed-
ding may be such as to unfit them for use ; in others their
texture may expose them too much to the attacks of frost
or to the solvent action of carbonated waters. Some are
contaminated with pyrites, or contain so considerable a

92 APPLIED GEOLOGY.

proportion of argillaceous matter as to impair their dura-
bility, while others contain clay in thin seams or irregular
crevices, which, if it does not lead to their early decay,
soon gives them a cracked and unsightly appearance. This
seems to be more largely true of the gray sub-crystalline
limestones. In other cases the strata may contain crystals
and nodules of quartz, unfitting them for regular working ;
yet some silicious limestones in which the silica in fine
particles is uniformly disseminated throughout the mass,
though somewhat harder to dress, will doubtless be found
possessed of desirable qualities in point of durability and
strength. The points here mentioned are those that need
to be carefully observed in choosing places for opening
large quarries, and in selecting those seams that it is pro-
posed to use for building purposes, while careful attention
should always be given to the condition of all seams that
have long been exposed to the elements. Of the lime-
stone formations of North America, the Niagara and Cor-
niferous appear to be the most generally useful over wide
extents of country, the others being either limited in their
range to certain regions, or presenting great differences of
condition in sections remote from each other. Thus the
more valuable Sub-carboniferous limestones are limited to
the Western States, while the Trenton, which furnishes
good building-stones in northern New York, in Canada,
and in East Tennessee, is worthless in Ohio and Indiana,
and of doubtful repute in Wisconsin, Minnesota, and
Iowa.

Brick, Terra-Cotta, and Drain-Pipes. — These
articles, so widely used for house construction, ornamen-
tation, and drainage, are fabricated, as is well known, from
clays possessing sufficient plasticity to permit of their be-
ing shaped in molds, and then burned in kilns to the requi-
site degree of hardness. Coarse clays, suited for bricks
and drain-pipes, are widely distributed over our country.
In the regions covered with drift deposits north of the

MATERIALS OF CONSTRUCTION. 93

parallel of 39°, they are found as large parts of these de-
posits, which, when free from stones, and from pebbles of
limestone, can be used for brick-making. They are also
found as a result of the weathering of shales, or of the
disintegration of gneissose and other rocks, in the recent
deposits of rivers and smaller streams, and in some lacus-
trine deposits formed when the lakes occupied a consider-
ably higher level than at present as, for example, along
the shores of Lake Michigan. Besides these wide-spread
deposits, clays, some of which are adapted for much
choicer uses, and which will be described in another con-
nection, but the coarser of which make superior bricks,
terra-cotta, and drain-pipes, are found in the Cretaceous
deposits of New Jersey, Minnesota, and doubtless of some
Western States and Territories ; others may be found in
the Tertiary deposits along the Atlantic coast and the
Gulf of Mexico ; while clays of great excellence may be
obtained by the proper weathering of some of the under-
clays of coal-beds, both of the coal-measures and of the
Cretaceous deposits of Colorado, Wyoming, New Mexico,
Montana, and some of the Pacific States and Territories.
As may readily be inferred from the wide differences in
origin of clays, they present also wide differences in com-
position and character. Essential ingredients in all of
them are a sufficient proportion of kaolin, or true clay, to
give them the requisite adhesiveness and plasticity, and of
quartz sand to correct the tendency of clay when burned
to excessive shrinking, warping, and cracking. The relative
proportion of these ingredients may vary, however, within
wide limits, and they are mingled besides with variable
amounts of iron oxide, of the alkalies potash and soda,
and of the alkaline earths lime and magnesia. The iron
usually gives to bricks, as they are commonly burned,
their well-known red color, by becoming the red oxide ;
but when a considerable proportion of lime and magnesia,
or of these with potash, is present, these substances at a

APPLIED GEOLOGY.

high temperature form with the iron and silica a com-
pound which partially fuses, giving to the bricks a greater
degree of solidity, and imparting to them the agreeable
cream-color which is so favorably known in the so-called
Milwaukee brick. As examples, both of the essential in-
gredients of clays and of their differences of composition,
it may be said that the common brick-clays from the New
Jersey Cretaceous contain about 45 per cent of kaolin, 30
per cent or more of sand, and 8 to 10 per cent of iron and
the alkaline ingredients ; that the ordinary clays of Wis-
consin contain usually less than 25 per cent of kaolin, 60
per cent and upward of sand, and about 9 per cent of
iron and alkaline substances, both these kinds of clay
yielding red bricks; while the clay from which is fab-
ricated the cream-colored Milwaukee brick has only
about 20 per cent of kaolin, 4 per cent of iron oxide, and
more than 40 per cent of lime, magnesia, and potash ; this
last clay being the more noteworthy because of the preva-
lent opinion that any considerable proportion of lime and
potash is fatal to the excellence of a clay, whereas, in
the use of this clay, the presence of these substances is
counted a great advantage, not only as giving the bricks a
greater solidity and an agreeable color, but as furnishing
a reliable test of the thoroughness with which they have
been burned ; since, with insufficient burning, they have a
red color, while the creamy tint appears only with a tem-
perature that produces an incipient fusion. Brick clays
are much improved by weathering. They are then tem-
pered with a sufficient amount of clean, sharp sand, if the
clay is deficient in this ingredient, ground in a pug-mill
to secure uniformity of composition, and molded for burn-
ing either by hand or by a machine which is capable of
shaping many thousands in a day. In the common mode
of burning, a considerable portion of the product is apt to
be unfit for use, partly from being overburned, and so glazed
and cracked, and partly from being underburned, with the

MATERIALS OF CONSTRUCTION.

result of being weak and crumbling. In the Geological Re-
port of New Jersey, for 1870, a perpetual kiln is figured
and described, which appears to be ingeniously devised
for securing uniformity of product with great economy of
fuel. It is said to be capable of turning out from three
to five millions of brick per year, at an expense for fuel of
less than forty cents per thousand, waste coal being used
for this purpose.

In the year 1880 over four thousand millions of com-
mon and pressed brick are reported to have been manu-
factured in the United States, the States which were fore-
most in that industry being New York, Pennsylvania,
Ohio, Illinois, Indiana, New Jersey, Missouri, and Massa-
chusetts. In the manufacture of drain-pipes Ohio leads,
while New Jersey produces fully eighty per cent of all the
terra-cotta. The manufacture of this last article requires
the superior kind of refractory clay fitted for fire-brick,
and a variety of colors is produced by the judicious admix-
ture of clays having slightly different ingredients. Sewer-
pipes are also made from the same kind of clay, both arti-
cles requiring to be burned at a high temperature.

Materials for Mortar. — The materials for the mortar
to be used in various kinds of construction are sand, quick-
lime, and hydraulic cements, both natural and artificial.
The type of a good sand for mortar-making is an aggre-
gation of clean, sharply angular granules of quartz, of
somewhat coarse texture ; and the more closely a sand
approximates to this type the better it is. In many sec-
tions an impure mixture of quartz sand with rounded
grains of other substances and some clay is used, pro-
ducing great annoyance by the crumbling of the mortar
and the frequent fall of portions of the plastering of
houses. It would be better, and in the end cheaper, to
bring good sand from a considerable distance, rather than
to use such inferior materials. Sands for mortar are found
widely distributed in various superficial deposits along

96 APPLIED GEOLOGY.

stream-courses, and on the shores of the ocean and other
bodies of water, in the modified drift, in unconsolidated
beds of Tertiary and Cretaceous age, and occasionally in
the incoherent sandstones of much greater geological age.
Quicklime for use in mortar is obtained by properly cal-
cining in kilns any of the limestones and dolomites, whose
general distribution has been given on a preceding page,
and which are of a reasonable degree of purity ; i. e., which
contain no more than six to eight per cent of silicious and
earthy impurities. Doubtless, limestones less pure than
this are frequently burned when nothing better can be ob-
tained ; but it is obvious that the nearer a limestone is to
absolute purity, the better it is for lime-making. A rough
test of the purity of a limestone may be made by dissolv-
ing small fragments, chipped from various parts of the
stone, in hydrochloric acid, applying a little heat if mag-
nesian, and noting the nature and amount of the residue.
This test can of course be made much more accurate if
means can be had for weighing the stone fragments, and
then weighing the filtered and dried residue. Quicklime
obtained from ordinary limestone differs in some marked
respects from that obtained from dolomites or highly mag-
nesian limestones. The former, called hot limes, on the
application of one third their volume of water, slack, i. e.,
fall rapidly into a fine, whitish powder, with great evolu-
tion of heat ; and when made into a paste with water, with
which paste is thoroughly incorporated from three to five
times its volume of clean, sharp sand, form a mortar which
sets or hardens very quickly in the air. The latter, called
cool limes, require less heat for their thorough calcination,
slack less rapidly and with smaller evolution of heat, and
form a mortar which sets more slowly, and so admits of more
deliberate work on the part of the mason. While equally
good with the other for all common uses of mortar, the
dolomitic limes have evidently a special adaptation to the
operations of the plasterer. Lime would undoubtedly

MATERIALS OF CONSTRUCTION.

make better mortar could it, after being slacked, be thor-
oughly covered from the air, and left for some months to
ripen before being mixed. In this way, and with very
coarse, angular sand, is said to have been made the mortar
found in many ancient European structures, which rivals
the firmness of the stones which it cements. A vast frag-
ment of the old castle of Heidelberg, comprising nearly
one half of one of the enormously thick towers, blown up
by the French in 1688, still lies in the moat into which it
slid, the entire mass firmly welded by the adhesion of its
mortar, whose stony hardness seems unimpaired by an
exposure of nearly two centuries. Our modern mortars,
quickly made, can bear no comparison with such endur-
ance as this. Indeed, in the removal or alteration of
somewhat recent structures, the adhesion of the mortar
too often opposes little resistance to the operations of the
workmen, and not unfrequently, after the lapse of a few
years, it crumbles spontaneously from between the stones
which it was intended to cement.

In the selection of a limestone for calcination, after a
sufficient degree of purity is assured, it is better to choose
such beds as, without being friable, possess a somewhat
granular and porous texture, since they burn to lime most
easily and uniformly. The magnesian limestones have this
constitution more generally than others, furnishing another
reason for their selection where they are attainable. The
Census Reports of 1880 show that lime suitable for mortar
is found in greater or less abundance in every State and
Territory of our Union, though it would appear that Ore-
gon and Washington are least abundantly supplied.

While the mortars made from the kinds of lime just de-
scribed, when immersed in water, remain soft and without
cohesion, and gradually part with their lime by solution,
that made from hydraulic limes and cements, either with
or without admixture with sand, possesses the singular and
valuable property of setting more or less quickly under

98 APPLIED GEOLOGY.

water to a mass of stony hardness and great strength.
Hence, in all constructions where moisture is to be with-
stood, as in damp foundations or submerged structures,
the mortar should contain the latter kind of lime to the
extent of at least half that which is used in the mixture,
and in many cases the whole of it. This difference in be-
havior between common and hydraulic limes is due to an
important difference in their composition. Common lime
is burned from carbonate of lime or carbonate of lime and
magnesia as nearly pure as can be obtained ; and the hard-
ening of the mortar made from it is due in part to the re-
formation of lime carbonate, in part to the crystallization
of hydrate of lime upon the grains of sand, and probably
in part to the slow formation, during ages, of lime silicate,
in virtue of which a good mortar grows harder with age.
Hydraulic lime, on the other hand, is burned from lime-
stones notably impure, containing, as analyses show, from
twenty to about fifty per cent of silica, alumina, and iron
oxide ; it either does not slack at all with water, or slacks
very slowly, and with great difficulty, needing, therefore, to
be ground to a fine powder before being used ; and its hard-
ening in mortar is due to a chemical combination of lime,
or lime and magnesia, with silica and alumina, partially
effected during the burning, and partially by the agency
of water, forming hydrated silicates and aluminates of
lime and magnesia, which are insoluble in water. The im-
pure limestones suitable to yield hydraulic lime by proper
burning naturally constitute, as General Gillmore remarks,
transition beds between mechanical sediments like sand-
stones and shales, and the purer limestones ; and in such
geological positions they are usually found. From their
nature as transition beds, also, and dependent as their
properties are upon a due intermingling of substances
from two very distinct sources, they possess, as might be
supposed, but " little uniformity of composition over any
wide areas, or through any considerable thickness of

MATERIALS OF CONSTRUCTION.

strata," and consequently need great care in selection, to
secure stone which, when burned, will yield a good hy-
draulic lime. Indeed, some of the most reliable and
highly esteemed materials of this class, like the celebrated
Portland cement, are made artificially by burning a care-
fully proportioned and thoroughly incorporated mixture
of clay and chalk. Where, however, natural stone can be
found which, by proper care in selection and burning,
will yield hydraulic limes and cements of good quality, it
can be more cheaply obtained, and is good enough for all
practical purposes. The United States, fortunately, has
such limestones occurring at several different horizons,
and of somewhat extensive distribution. The lowest of
these horizons is in the Calciferous group, which at Utica
in La Salle County, 111., and at several points in Ma-
ryland and Virginia, furnishes hydraulic limes of satis-
factory quality, and may be expected to do the same at
points on the same range in eastern Pennsylvania. The
Water- Lime group, at the base of the Lower Helderberg,
with some kindred limestones belonging just beneath it in
the geological series, furnishes nearly ninety per cent of all
the hydraulic lime and cement produced in the United
States, being largely burned in Ulster County, N. Y., fur-
nishing the esteemed Rosendale cement, also in Oneida,
Madison, Onondaga, and Erie Counties, and near San-
dusky, in Ohio; while the well-known Louisville cement
is obtained, according to Prof. James Hall, from beds
of the Corniferous period belonging just above this in
the geological series. A limited outcrop of rocks of the
Hamilton period at Milwaukee, Wis., furnishes the Mil-
waukee cement. The St. Louis limestone, of the Sub-car-
boniferous, is said to give promise of possessing hydraulic
properties at several points in Illinois ; while impure lime-
stones of the coal-measures furnish "Parker's cement"
in Belmont County, O., and the " Johnstown cement " in
Cambria County, Pa. A volume on " Mineral Resources

100 APPLIED GEOLOGY.

of the United States," published by the United States
Geological Survey in 1883, states that limestone suitable
for hydraulic cements is found also in California, Oregon,
and Washington Territory. The same work gives the
United States production of cement for 1882 as about
3,250,000 barrels, of about 300 pounds each, of which
New York is credited with 2,000,000 barrels, Ulster Coun-
ty alone furnishing over 1,500,000 barrels; the vicinity of
Louisville, Ky., ranking second as a great producing center.

Works on building materials which students are recommended to consult.

" Tenth Census of the United States," Vol. X.

Prof. James Hall's " Report on Building-Stones."

Hull, " Building 4fcd Ornamental Stones of Great Britain," etc.

" Geology of Wisconsin, i873-'79," Vol. I, Part III, chap. iv.

" Mineral Resources of the United States, 1883," p. 450, et seq.

Gillmore on " Limes, Hydraulic Cements, and Mortars."

Totten on " Mortars."

" Report on Clays of New Jersey," 1878.

" Geological Report of Minnesota," N. H. Winchell.

The student should also carefully consult the geologi-
cal reports of his own State, by the aid of the index with
which they are usually furnished.

CHAPTER VI.

RELATIONS OF GEOLOGY TO AGRICULTURE.

IN the organization of the geological surveys of the va-
rious States, the advancement of agriculture has in nearly
all cases been made one of the leading objects to be at-
tained ; yet it is doubtful whether the importance of the
relations of geology to the tillage and improvement of the
soil is fully realized, especially by those most immediately
concerned. Questions as to the origin and distribution of
soils ; their character, and how it originated, and by what
means it may be most cheaply improved ; the means by
which the reproduction of a proper arable surface may be
made to keep pace with the natural processes of waste
through tillage and other agencies; and the sources of
supply and the proper use of mineral fertilizers to make
good the necessary losses incurred in cropping — all involve
considerations of a geological character, and it may easily
be seen that they are of no secondary importance.

Those superficial portions of the unconsolidated sur-
face-materials of the earth's crust, usually of but little
depth, which are termed soils, with the subsoils extending
to variable depths beneath them, are composed chiefly of
exceedingly variable mixtures of sand and clay, with con-
siderable proportions of vegetable mold and iron oxide,
and usually smaller but very important amounts of lime,
magnesia, the alkalies potash and soda, and phosphoric
acid.

102 APPLIED GEOLOGY.

These soils and subsoils, like all other unconsolidated
earthy materials, have originated from the decay, the dis-
aggregation, and the wear of rocks once solid. Rocks de-
cay through the chemical action on some of their con-
stituents of water holding in solution carbonic acid and
other chemical agents, which, penetrating deeply into their
pores and crevices, unites with some of their components,
and carries them away in solution, leaving the residue in
an incoherent state. They are disaggregated, to some
extent, by the roots of trees and vegetables, which insinu-
ate themselves into their crannies and larger pores, and
split them in pieces by progressive growth ; but much
more rapidly, in frosty latitudes, by the expansion in freez-
ing of water, which is present in some amount in the sub-
stance of nearly all rocks. This agency of destruction,
which has already been mentioned as a chief cause of
dilapidation in building-stones, is a very efficient instru-
mentality in the formation and comminution of soils.
Rocks are worn away and ground to powder by the fric-
tion of sand and of loose fragments of other rocks, dragged
over them by moving water, or by blocks and sheets of ice,
or which are swept along and dashed against them by the
wind. These fragments of rock-materials, set in motion by
any of the agencies that have been named, not only wear
away the solid rocks, but also, by their mutual rubbing,
grind each other down to an ever-increasing degree of
fineness, until what were once large angular fragments
become rounded pebbles, and ultimately fine mud or sand.
Abundant examples of this mode of formation of the ma-
terials for soils may be seen, not only in the deep valleys
and ravines that have thus been produced, but in the gul-
lies filled with worn stones which every rain-storm is
likely to make on cultivated slopes ; and also in the rocks
of some regions, which are worn and rounded, and even
under-cut, by the agency of wind-swept sand.

The materials of soils and subsoils, originating in the

RELATIONS OF GEOLOGY TO AGRICULTURE. 103

ways described above, may in some cases occupy very
nearly their original position, when their character will
naturally be dependent largely on that of the underlying
rocks ; while in other cases they have been removed to
greater or less distances from their place of origin, and so
bear no relation whatever, in character or composition, to
the rocks on which they rest. Considered, therefore, with
reference to this circumstance only, we have soils of disin-
tegration, or those owing their existence to the waste of
rocks in place ; and soils of transportation, whose materials
have been brought to their present position by agencies
such as ice and water from regions often quite remote. The
soils of those portions of the eastern and central United
States which lie south of the thirty-ninth parallel of lati-
tude belong largely to the first class ; while north of this
parallel the soils are chiefly soils of transportation.

Soils of Disintegration. — Soils derived from the
disintegration of sandstones are, as might be supposed,
sandy, containing only those proportions of clay which
were present in the original rock. These are frequently
sufficient, in the argillaceous sandstones, to form a light
sandy loam, lending itself easily to tillage, but apt to be
less retentive than could be desired. Shales and soft slates
form by weathering clay soils, which, where the rocks
are pretty purely argillaceous, are heavy and undesirably
compact, difficult to work, but highly retentive both of
water and fertilizers. Where, however, shales contain a
large proportion of sand, their disintegration produces
either clay loams, or those very desirable soils called
loams, in which the proportions of sand and clay are so
happily adjusted as mutually to correct the defects arising
from an excess of either ; and which, while sufficiently
easy of cultivation, are also properly retentive of all ele-
ments of fertility. The disintegration of limestones is
due usually to the gradual solution and removal of the
lime which forms their characteristic ingredient. Hence,

104 APPLIED GEOLOGY.

the soil which arises from their destruction contains no very
marked amount of lime, but is composed mostly of the
original impurities of the rock, chiefly clay and iron, with
sometimes silica, forming usually a reddish clay with rarely
more than from one to five per cent of lime. Indeed,
some shale soils contain a larger percentage of lime than
those derived from the decomposition of limestones, prob-
ably because from their retentiveness they have not readily
permitted it to be carried away in solution. Soils derived
from the wear rather than the disintegration of limestones
contain a larger proportion of lime in fine or coarse grains
and pebbles ; but these, from the manner of their forma-
tion, have been borne to some distance from their place of
origin, and have usually been mingled with materials from
other sources, to which they impart a useful modification.
Soils derived from the disintegration of rocks of the gra-
nitic class owe whatever mineral elements of fertility they
may possess to the decomposition of the feldspathic, mica-
ceous, and hornblendic constituents of these rocks, which
furnish a clayey matter retaining some of the alkaline, cal-
careous, and ferruginous ingredients of the original miner-
als ; and this, mingled with the silica of the rock, may fur-
nish, where the decomposition is unusually rapid, a soil of
a good degree of fertility. More commonly, the native soil
of granitic areas is thin and poor. On the contrary, the
soils derived from the decomposition of the traps and other
volcanic rocks are usually excellent, having a good texture
and color, and being abundantly charged with the alkalies,
lime, magnesia, and iron of the minerals entering into such
rocks, with almost always favorable amounts of phosphoric
acid.

Soils of Transportation.— Soils such as have just
been described, which owe their leading characteristics to
the nature of the underlying rocks and to the agencies to
which these have been subjected, and which often at but
little depth beneath the surface exhibit the same essential

RELATIONS OF GEOLOGY TO AGRICULTURE. 105

structural characters as the parent rock, into which they
gradually merge by a diminution in the degree of disin-
tegration, differ widely in origin, topographical position,
and in some marked features of constitution, from the
second kind of soils which have been called soils of trans-
portation. The former, with some general exceptions
presently to be noted, constitute the fundamental soils of
our Southern and central range of States south of a line
coinciding rudely with the thirty-ninth parallel of latitude.
The latter cover, with few exceptions, those parts of the
United States lying north of this limit and all of British
America.

It will be obvious to any one who attentively considers
the surface appearance's presented by this latter region,
that some widely operative and exceedingly powerful
agency has, within a comparatively recent geological pe-
riod, been active in shaping its surface features and in ac-
cumulating, mingling, and distributing the great irregular
sheets of unconsolidated materials with which its rocks are
more or less thickly covered. The thoughtful observer
will note that the upper surface of the harder rocks ex-
posed in quarrying or by the wash of rains is curiously
smoothed and scored with fine parallel scratches, or some-
times with wider grooves usually running in a nearly north
and south direction. His attention will be attracted by
the great rudely rounded blocks of stone, sometimes of
several tons weight, scattered here and there in the fields,
which he can readily see are strangers to his vicinity, and
which, if his geological knowledge permits, he may often
recognize as similar to the rocky formations of regions far
northward of that where they are now found. He will ob-
serve that thick sheets of blue and yellow clay, often thick-
ly studded with blocks of stone, or irregularly alternating
beds of sand and gravel and loam, or sometimes ridges of
confusedly intermingled earth and stones, now rest on rocks
of widely different character and of much simpler constitu-

106 APPLIED GEOLOGY.

tion than the materials which cover them. He may even
learn from well-excavations, and deep borings in the val-
leys of rivers and streams, that many of these now flow
scores of feet above their original rocky beds in channels
cut in the unconsolidated materials with which they have
by some agency been filled. These facts, and some others
of similar import which he would probably observe, would
be likely to suggest to him that the agent which produced
them, whatever it may have been, proceeded from the
north ; and that the loose superficial materials which now
veil the rocks and fill deep the valleys, and whose fertile
upper surface constitutes the soils, probably had their ori-
gin to the northward of their present locality. The only
known agent that could have produced effects so great and
so enormously wide-spread, planing and scoring rocks over
areas hundreds of thousands of miles in extent, and trans-
porting far from their birthplace great blocks of stone, is
the power of a great, slowly-moving sheet of ice, such as
that which now envelops a large part of Greenland ; and
to such an agent these phenomena are now very generally
ascribed. This vast ice-sheet, whose thickness, as judged
by the heights which it overtopped, must have been many
hundreds or even thousands of feet, enveloped and bore
along with it all loose or projecting materials which it en-
countered or which dropped upon its surface ; and, armed
with these, its under surface became a grinding instrument
of enormous power, like a gigantic rasp, by which in its
slow progress southward the surfaces of all underlying
rocks were worn away and reduced to a fine rock paste,
while the pre-existing valleys either were obliterated or
were widened and deepened, according as their courses
opposed or coincided with the direction of movement of
the vast abrading mass. By this means were formed, dur-
ing the unknown ages of duration of unusual cold called
the glacial period, enormous amounts of what has not in-
aptly been called " rock-flour," which, when a warmer cli-

RELATIONS OF GEOLOGY TO AGRICULTURE. 107

mate again prevailed and the ice-sheet slowly melted, was
intermingled more or less completely with the other sub-
stances previously frozen into the glacial mass, and cov-
ered the surface with the raw materials of a soil of highly
complex and varied constitution. With regard to these
materials thus brought together it is obvious, — first, that,
being the result not of disintegration but of wear, they
must at the outset have contained the constituents of the
parent rocks unchanged ; second, that, from the manner
in which they were formed, substances from widely differ-
ent sources were likely in most cases to be commingled, so
that their composition might be expected usually to be
more complex and variable than that of soils derived from
rocks in place ; and, third, that they have no relationship
to the rocks on which they at present repose other than
that of mere accidental juxtaposition. The surface por-
tions of these crude materials of soils have since their depo-
sition been subjected to the usual atmospheric agencies
of disintegration, which have broken up and comminuted
in various degrees their coarser portions, have made solu-
ble and subjected to the processes of plant-growth parts
of their alkaline, calcareous, and phosphatic ingredients,
and have mingled the whole with the organic residues de-
rived from the decay of successive generations of plants,
forming soils such as we now find them in areas not yet
subjected to tillage. The subsoils have been subjected in
a less degree to these atmospheric agencies, and retain
more nearly their original constitution. They are likely,
therefore, to be charged with a number of ingredients
necessary to plant-growth, in greater abundance than the
surface soils, and may, by proper mechanical treatment
and by the action of certain natural agencies, restore to
them elements of fertility of which they constantly tend
to become exhausted, not only by the growth of crops,
but also by that slow but incessant removal of the surface
to which cultivated fields are subjected by the wash of

108 APPLIED GEOLOGY.

rains. The most obvious mechanical means by which the
proper renewal of the surface soil may be secured is deep
tillage and subsoiling. By this means materials hitherto
untouched are brought within reach of atmospheric influ-
ences which compel them to yield to agriculture any fer-
tilizing principles they may possess. Among the natural
agencies through which the subsoil appears to react bene-
ficially upon the soil may be mentioned the capillary ac-
tion of well-conditioned soils and earth-worms. The fine
pores of a soil of proper texture not only furnish channels
through which the rains sink into the earth, but also, when
the surface has become dry, the deeper seated supplies of
moisture ascend through their minute tubes by an action
termed capillary to supply the losses occasioned by evap-
oration, bringing up with them in solution small but im-
portant amounts of fertilizing elements obtained from the
subsoil which their evaporation leaves in the surface soil.
Hence, after periods of drought, when this capillary action
is more than usually active, the farmer frequently observes
that his fields show more than usual fertility, due without
doubt to this cause, which yet in ordinary seasons is con-
stantly operating to augment the fertility of well-tilled
lands. The humble earth-worms will, doubtless, seem to
many a very insignificant agent in promoting the fertility
and renewal of soils ; yet the careful observations of the
distinguished naturalist, Charles Darwin, have left no room
for doubt, not only that the active burrowing of their in-
numerable myriads plays a very important part in loosen-
ing the soil and making it readily accessible to atmos-
pheric agencies of change, but also that their digestive
action on the finer soil particles is a highly influential
agency in the formation of vegetable mold, and in bringing
to the surface sorne deeper seated elements of fertility
contained in the subsoil.

Another kind of soils of transport, by no means con-
fined to the region of glacial action that has just been de-

RELATIONS OF GEOLOGY TO AGRICULTURE. 109

scribed, but found covering areas of considerable extent
in all regions, is that which finds its type and exemplar
in " bottom-lands." These soils are due to the carrying
power of flowing water, which in times of rain collects the
wash of the uplands into rivulets, streams, and rivers, all
rushing downward, turbid with the earthy matters with
which their waters are loaded, until they reach the low-
lands, where, when their flow is checked, they deposit first
the coarser and then the finer materials that they have
transported, gradually filling the hollows and coating the
flood-plains of streams and rivers with a soil of exuberant
fertility, and whose mass is augmented with every period
of flood. Soils originating in this way are not confined
wholly to lowlands and to the valleys of rivers and streams ;
but, especially in the glacial region, they may be found oc-
cupying apparently the ancient sites of vanished pools and
lake-like expanses, which were probably formed by the
waters of the great melting glacier.

It may thus be seen that our present arable soils owe
their origin, their renovation, and much of their present
condition, to the disintegration and wear of rocks ; and
that the means by which this work has been done are the
chemical action of the atmosphere, and the mechanical
force exerted by freezing water, and by moving water and
ice. It is needful also to bear distinctly in mind that the
mechanical agents, by their own unaided action, can not
produce a fertile soil. Their efficiency is limited to their
aid in reducing rock materials to a suitable degree of fine-
ness, and there it ceases. But the plant-food, locked up
in even the finest particles of rock, must be offered to
plants in a soluble form before it can be used ; to accom-
plish this solution, the co-operation of those native chemi-
cal agents contained in the atmosphere must be invoked.
The mechanical agencies merely prepare the materials for
the freer and more effective action of the real soil-makers,
the chemical ones. Now, the agency of man, aided by

HO APPLIED GEOLOGY.

such natural helpers as capillarity, the roots of deep-grow-
ing plants, and burrowing animals, is a mechanical one,
and consists in putting the soils which he tills into the
best possible condition for the action of the needed chemi-
cal agents. The more truly, then, he copies nature, and the
more thoroughly he learns to accelerate the slow-moving
operations which geological agencies effect, the more suc-
cessful his labor is likely to prove. Deferring, then, for the
present, any consideration of the fertilizing ingredients of
soils, it may be profitable to direct our attention first to
their nature and physical condition, and to consider how
this may best be improved.

Nature and Amelioration of Soils. — The physical
properties, in virtue of which a soil lends itself kindly to
culture, are (i) easy penetrability to roots, to moisture, to
air, and to fertilizers ; (2) a sufficient retentiveness to pre-
vent the ready escape of moisture and of fertilizing ingre-
dients ; and (3) readiness to absorb and utilize the solar
warmth, for which last property color and texture are essen-
tial conditions, dark-colored and permeable soils and light-
colored tenacious ones being the opposite extremes in this
respect. These physical characters depend essentially on
the relative proportions of three substances, viz., silicious
sand, day, accompanied usually with a notable amount of iron
oxide, and those residues of organic decay which are termed
humus. An undue preponderance of sand gives rise to a
light soil easy of cultivation, and readily dried and warmed
by the heat of the sun, but tending constantly to sterility
from the ease .with which it permits all soluble substances
to be leached from it by the rains. A like excess of clay
forms what is called a heavy soil, very tenacious, retentive
in a high degree of moisture and fertilizers, and capable
of giving a firm foothold to plants, but cold, impermeable,
and difficult to till. Where humus preponderates, we have
a peaty or turfy soil, which, when properly drained, is
warmed and dried with wonderful rapidity, but which

RELATIONS OF GEOLOGY TO AGRICULTURE, m

gives little support to plants, is apt to be sour from car-
bonic and other acids, and is usually deficient in some
highly essential mineral elements of plant-food. So far
as physical constitution is concerned, therefore, that soil
is best " whose condition, equally removed from too great
compactness and too great permeability, fits it to absorb
and retain the due amount of moisture while giving easy
exit to any overplus, to permit the ready access of air, and
to absorb and utilize the warmth proper to its location."
To judge from a comparison of many analyses, such a soil
would contain from sixty to eighty-five per cent of sand,
from ten to thirty per cent of clay and iron oxide, and
from five to ten per cent of humus. Where a soil, from an
excess of any component, does not naturally possess a
proper texture, it stands in need of amelioration ; and the
means by which this may be best and most cheaply effected
will naturally depend on the nature of its defect : it is also
well to observe that amendments of the soil, i. e., bene-
ficial changes in its condition and texture, should precede
the application of manures, inasmuch as they prepare it in
some cases to retain the fertilizing principles, and in all
cases to derive the fullest benefits from their use.

An obvious means for improving sandy soils is mixture
with clay to increase their retentiveness, and where this is
found, as is sometimes the case, at no great depth in the
subsoil, this improvement may be effected at no undue
expense. Very great benefit may also be derived by treat-
ing such a soil with either variety of quicklime, or with
clayey marls, either of which, while improving its texture,
adds to it an important element of plant nutrition, in which
such soils are apt to be deficient. The tillage of sandy
soils should also be shallow, three inches in depth being
probably quite sufficient, and every means should be used
both to retain and increase any original solidity they may
possess.

Turfy or peaty soils and swamp mucks contain a su-

112 APPLIED GEOLOGY.

perabundance of humus, in virtue of which their materials
may be profitably composted with manures, and used to
improve other soils which are deficient in this ingredient.
Mucky soils need first of all as careful drainage as is prac-
ticable, and then thorough treatment with quicklime and
mixture with coarse, gravelly sand and animal manures.

Heavy clay soils need first of all thorough under-drain-
ing to remove the superfluous water with which they are
apt to be clogged, and by which they are rendered both
adhesive and difficult to be warmed. By the removal of
this superabundant moisture, the texture of such soils is
at once very materially improved. Their texture may then
be further loosened and made more pulverulent by treat-
ment with quicklime, by admixture with coal-ashes, or by
burning portions of the surface in ridges or heaps with
dried leaves and weeds or brush, and then mingling the
burned portions with the remaining soil. Deep and rough
plowing of heavy soils in the late autumn permits advan-
tage to be taken of the powerful pulverizing action of
winter frosts. It has also been suggested that, in the vi-
cinity of iron - furnaces, their slags, previously rendered
pulverulent by being run from the furnace into shallow
pools of water, could be utilized advantageously for light-
ening the texture of heavy soils, adding to them also
some elements of value in the compounds of lime and
iron, and the small amounts of phosphorus which they
contain. Doubtless the slags from the basic process, re-
cently devised for the elimination of phosphorus from
iron, containing as they do a considerable percentage of
this element, will be found especially useful for this pur-
pose, because of their unusual content of this valuable
fertilizer.

Besides that proper physical condition which has just
been described, with some of the means for its promotion,
and which fits a soil to give suitable support to growing
plants, to permit the easy spread of their roots in search

RELATIONS OF GEOLOGY TO AGRICULTURE. 113

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114 APPLIED GEOLOGY.

of nourishment, to favor a proper circulation of air, and
to retain the moisture needed for plant-growth while yield-
ing ready outflow to all excess, every fertile soil must pos-
sess also sufficient amounts of the inorganic substances
and nitrogen which enter into the tissues of plants. What
are the inorganic substances appropriated from the soil
by the various cultivated plants can be learned from the
analyses of their ashes, and a table of such analyses for a
number of common plants, derived from French authori-
ties, is given on the preceding page.

Tables of the mineral components of the above plants,
derived from the ash analyses of Emil Wolff, may also be
found in the Geological Report of Ohio for 1870, pages
366 and 367, which, while differing somewhat from the
above in the relative proportions of some constituents,
present no material differences in the substances them-
selves, and these, as they are present in some proportion,
doubtless subject to considerable variations, in the tissues
of all cultivated plants, are obviously essential to their
growth and health. These substances must, with slight
exceptions, be supplied by the soil ; and a very impor-
tant part of scientific agriculture consists in knowing by
what means to keep up in the soil a due amount of these
important constituents, which would otherwise tend to ex-
haustion by successive cropping. Some of these, like silica
and iron, need little attention, being present in sufficient
amounts in nearly every soil, and being rendered readily
available for plant- growth by natural causes. In many
soils, lime and magnesia also are found in proportions
sufficient to supply the needs of a long series of crops,
while in others there is a deficiency of these substances.
An average soil will give about two million pounds per
acre, for a depth of eight inches. If, then, it contains one
per cent of lime, this will make available with ordinary
cultivation at least 20,000 pounds per acre. It will be
seen, by reference to the table, that tobacco is the most

RELATIONS OF GEOLOGY TO AGRICULTURE. 115

exhaustive of lime among the common crops, containing
about 9^ pounds per hundred of dried leaves, or 190
pounds per ton. It would require, therefore, one hun-
dred crops of a ton per acre — much more than the usual
crop — to exhaust this element from a soil containing one
per cent. It is obvious that this is an extreme case for
any soil ingredient. For an ordinary rotation of crops,
one per cent of lime or magnesia in a soil would suffice
for a long succession of crops. It may be observed that,
among the cereals, lime predominates in the straw and
magnesia in the grain. Hence the latter is likely to tend
to more rapid exhaustion than the former, since, in good
farming, the straw is mostly returned to the soil in the
form of manure.

Of the mineral ingredients of soils, those that need
most attention are phosphoric acid and the alkalies potash
and soda, especially potash, which, as may be seen by the
table, enters largely into most cultivated plants. It is
justly thought, therefore, that phosphates, potash, and ni-
trogen are vital points in the art of fertilization ; and a
high authority says, " A fertilizer may be considered com-
plete when it contains lime, potash, lime phosphate, and
a nitrogenous substance." Before considering the geo-
logical means which may be made available for keeping
up the fertility of the soil, it will be well to examine a few
analyses of soils of various kinds ; for, although questions
are often raised as to their practical value, based on the
local variability of soils, yet there can be no reasonable
doubt that, when properly made after careful sampling,
they may be of the greatest service to the agriculturist
in revealing to him the capabilities of his soils and their
needs.

The soil No. 3 of the Barrens is striking, from its de-
ficiency in phosphoric acid, the alkalies, and organic mat-
ter ; and its very small proportion of alumina, the basis of
clay, shows it to be excessively leachy, whence, doubtless,

APPLIED GEOLOGY.

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RELATIONS OF GEOLOGY TO AGRICULTURE. 117

its deficiencies originate. Soil No. 5 probably owes its
exhaustion to its low proportion of organic matter and of
lime. Nos. 7, 8, and 9 abound in fertilizing elements, but
would be likely to need attention to their physical condi-
tion. No. 4, which is considered still good after a cent-
ury of culture, though evidently not abounding in organic
matter, has in eight inches of depth, on the moderate
estimate of two million pounds to the acre —

Phosphoric acid, 3,000 pounds per acre.
Potash, 14,800 „ „

Lime, 19,400 „ „

Magnesia, 15,000 „ „

Using now the table of ash analyses and per cent of
ash given on a preceding page, it may be seen that a
crop of twenty-five bushels of wheat = 1,500 pounds, if
the straw, etc., equals fifty-six per cent of the crop, will
take from the soil —

Phosphoric acid, 11.175 pounds in grain and 4.1 pounds in straw.
Potash, 5^ „ „ „ 18.1

Lime, -j% „ „ „ 4j „ „

Magnesia, 2j „

Several other crops draw much more of these ingredi-
ents from the soil. An estimate made in the " Geological
Report of New Jersey," 1879, at page 116, of the amounts
of important minerals withdrawn from the soil by a five
years' rotation, of clover two years, and Indian corn, pota-
toes, and wheat, each one year, gives 581 pounds potash,
259 pounds lime, and 179 pounds phosphoric acid, of which,
however, nearly all the lime, and considerably more than
one half of the potash and phosphoric acid found in the
clover, straw, corn-stalks, and potato-tops would, in care-
ful farming, be retained on the estate and returned to the
soil in the form of manure. The tables that have been
given, and the specimen of computations that may be
based on them, will serve to indicate the proportions of

Il8 APPLIED GEOLOGY.

essential mineral elements that are found in various fertile
soils, the approximate amounts that are certain to be with-
drawn from them by various crops, and the importance of
restoring to them in some form the fertilizing principles
that have been withdrawn, to prevent a progressive ex-
haustion. An examination of Table I will show that,
while lime preponderates over magnesia in the straw of
the various cereals, the reverse is true for the grain ; and
when to this is added the fact that magnesia, from its great
power of absorbing and retaining moisture, tends to give
freshness to soils, it will suggest the expediency of testing
magnesian quicklime on soils in which lime is deficient,
despite the prejudice against it.

Geological Fertilizers. — Recalling now to mind the
native composition of fertile soils, and that the constant
tendency of the most judicious cultivation is to withdraw
from them certain substances of capital importance, espe-
cially nitrogenous compounds, the phosphates, the alkalies
potash and soda, as also lime and magnesia, it becomes a
question of much importance what materials the earth's
crust can supply to enhance the fertility of the soil without
undue expense. Among these substances, one of the most
widely distributed and cheaply available is peat, or swamp-
muck. There are few localities in the Northern United
States or Canada where it does not occur, and often in de-
posits of very considerable extent, in marshy spots, or at
small depths beneath the surface, occupying the sites of for-
mer swamps and ponds. It not only improves the color of
soils, making them more readily warmed, and their texture,
rendering them more pulverulent and more retentive of
moisture, but it also adds to them small but important
amounts of alkalies, and often phosphoric acid, while by
its decomposition it furnishes to growing plants supplies of
nitrogen and carbonic acid ; and it is claimed that it also
absorbs ammonia from the air. It should be weathered in
heaps for some months before being used ; or, better, it

RELATIONS OF GEOLOGY TO AGRICULTURE. 119

may be composted in various ways. It may be composted
with barn-yard manures, to which it not only adds its own
fertilizing principles, but aids very materially in retaining
the nitrogenous substances which might otherwise be dis-
sipated in the process of fermentation. It is also com-
posted with quicklime, or with lime and a small amount
of salt, a good mixture being, it is said, a bushel of freshly
slaked quicklime, or of lime slaked by brine, to twenty
bushels of peat. " Experience has fully sustained its
claims as a useful fertilizer, and chemical analysis shows
that it contains the elements needed to stimulate the growth
of farm-crops." (" Geology of New Jersey," 1868, p. 486.)

Another widely diffused mineral fertilizer, previously
mentioned in another connection, is lime, which is already
much used in agriculture, and is destined, doubtless, to a
much wider application, with the spread of better methods
of tillage. Not only those wide-reaching formations of cal-
citic and magnesian limestones, mentioned in the section
on building materials, but also thinner and more locally
developed seams, little regarded as building-stones, and
somewhat too largely charged with impurities to be favor-
ites for mortars, may furnish cheap local supplies for agri-
cultural uses, benefiting the soil as well by the silicates
and sulphates of lime developed in the burning, as by the
caustic lime and magnesia which they furnish in their most
finely divided and active form. These, as has already
been remarked, make clay soils lighter and silicious ones
more firm, lighten and sweeten damp and turfy soils, and
contribute to the destruction of weeds and insects, while
furnishing elements which analysis shows to be essential
to the growth of most cultivated plants. Their efficiency
in promoting the solution of other constituents of the soil
is also, doubtless, very considerable. To derive the fullest
benefits from their use, their application should usually be
followed by that of organic manures.

Besides the use of quicklime as a fertilizer, a stimulant,

120 APPLIED GEOLOGY.

and a solvent, benefit would doubtless be derived by many
soils from the application of calcareous marls, where they
may be obtained in the immediate neighborhood. Such
marls may be found, usually in small ponds, in some por-
tions of the Northern and Eastern States, where they are
occasionally burned for lime ; but their original pulveru-
lent condition permits their application to the soil in their
raw or unburned state, where their action as a source of
lime is more gradual and prolonged than that of caustic
lime. Also, under many peat-beds is found a calcareous
marl, formed of fresh-water shells, which may be advan-
tageously used for the same purpose. Beds of calcareous
marls of marine origin are extensively developed in the
Cretaceous and Tertiary formations of the States bordering
the Atlantic and the Gulf of Mexico, from New Jersey
southward, which, besides their carbonate of lime, contain
often important amounts of potash and phosphoric acid,
and which are destined to be largely used in the regions
where they occur.

Of greater importance, however, than these last-named
marls are the greensand or glauconitic marls, which are
found in similar geological formations and in the same re-
gions, and which derive their chief value from the very im-
portant proportions of potash and phosphoric acid with
which they are charged. These marls have been very largely
used in New Jersey, where they abound in three beds of
somewhat different properties ; and the effects that have
followed from their use are thus strongly stated by Prof.
Cook, "Geology of New Jersey," 1868, page 442 : " The
marl which has been described in the preceding pages has
been of incalculable value to the country in which it is
found. It has raised it from the lowest stage of agricult-
ural exhaustion to a high state of improvement. . . . Lands
which in the old style of cultivation had to lie fallow, by
the use of marl produce heavy crops of clover and grow
rich while resting. Thousands of acres of land which had

RELATIONS OF GEOLOGY TO AGRICULTURE. 121

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122 APPLIED GEOLOGY.

been worn out and left in commons are now, by the use
of this fertilizer, yielding crops of the finest quality. In-
stances are pointed out everywhere in the marl district, of
farms which in former times would not support a family,
but are now making their owners rich from their produc-
tiveness. Bare sands, by the application of marl, are made
to grow clover, and then crops of corn, potatoes, and
wheat." The work from which this is quoted gives, in the
succeeding pages, an account of the mode of using this
fertilizer and its results, which the student can profitably
consult ; as also Prof. Kerr's " Report on North Carolina
Geology," 1875, in which will be found an account of the
Tertiary calcareous marls of that State and their great value
in agriculture. On page 121 are given a few analyses of
greensand marls from New Jersey which may be found use-
ful, those being selected which have been approved in use.
It will be observed that in all these marls phosphoric
acid is present in considerable proportion, and to this sub-
stance much of their efficiency is ascribed. In many of
them, -also, potash is found in very considerable amounts,
and there is no good reason to doubt that its liberation in
the soluble form, in the course of the decompositions that
go on in the soil, gradually furnishes to plants this impor-
tant element in their nutrition. Of the silicic acid, a very
considerable proportion exists in an easily soluble condi-
tion ; and when it is considered how large a proportion of
this substance is found in the stems of plants, the prob-
able significance of this fact will be apparent. Doubt-
less, some other elements in these fertilizers, especially
lime, aid in enhancing their value. The use of these marls
in New Jersey is fully 100,000 tons per year, 1,080,000
tons having been dug in that State in 1882 for use and ex-
port ; and it is certain that with the advancement of agri-
culture in the Southern seaboard and Gulf States, in which
these and other marls are known to occur, they will be
sought out and used with great benefit to agricultural in-

RELATIONS OF GEOLOGY TO AGRICULTURE. 123

terests ; though, from the few analyses at present attain-
able, it would seem that the greensand marls are not there
so rich in phosphoric acid and potash as those of the more
northern localities.

A rich supply of the phosphates needed in agriculture
is obtained from the region in the vicinity of Charles-
ton, S. C, where it is estimated that nearly eight hundred
square miles are underlaid more or less abundantly
with phosphatic masses, of which twenty thousand acres
are counted worth working with the present appliances for
obtaining it. In this region, the phosphatic nodules are
found along the courses and in the beds of streams, from
which they are dredged, or underlying the surface at vary-
ing depths in a stratum which, according to Prof. Holmes,
averages about fifteen inches in thickness. It is reported
that, in 1883, 332,079 gross tons were produced, the rock
being sold on a guarantee of containing not less than
55 per cent of lime phosphate, or about 25 per cent of
phosphoric acid ; and in the same year the shipments
of manufactured fertilizers from Charleston are reported
as amounting to 130,000 tons. These figures will give an
idea of the vast extent to which the supply of this valu-
able fertilizer has already attained, from a source whose
importance had not come to be understood so recently as
1868.

Another source of phosphoric acid which is rapidly
attaining importance in this country is found in the mineral
apatite, which occurs as beds and veins in rocks, chiefly of
Archaean age. Deposits which may prove of economic
importance occur at Bolton, Mass., and at Crown Point,
N. Y., the latter of which is said to be extensive and has
been mined to a limited extent. The deposits of greatest
present importance are those found in Canada, in a region
extending northeastwardly from near Kingston in Ontario,
into Ottawa County, Province of Quebec. The deposits
here occur in both beds and veins, of which the former

124 APPLIED GEOLOGY.

afford the largest and purest supplies. The amount mined
in 1883 reached, it is said, 23,000 tons of rock, containing
from 75 to 85 per cent of lime phosphate. A small por-
tion of this comes to the United States, but most of it is
sent to England, where it is made available for agriculture
by treatment with sulphuric acid.

Guano, also, which attains to the rank of a kind of
geological deposit on certain islands off the coast of Peru,
and to some extent of Africa, may pioperly be mentioned
here. These deposits, formed from the droppings and
remains of sea-fowls, during countless generations, in re-
gions nearly rainless, are very rich in compounds of am-
monia and phosphorus, and have for forty years been
largely imported into Europe, and to some extent into this
country, for use in agriculture. According to estimates
made in 1873 of the amounts then remaining available, the
supply is destined to speedy exhaustion, as at that time
less than twenty years' supply could apparently be count-
ed on.

A geological source of the nitrogen so needful for plant-
growth may be found in the waste from the distillation of
bituminous coal in gas-making and coking. Nearly all
the bituminous coals of Ohio and Indiana which have
been fully analyzed show a content of nitrogen amounting
to an average of about one and a half per cent, and the
same is doubtless true of other coals of this class. In
the process of distillation this nitrogen is driven off in the
form of ammonia, which may be converted into the sul-
phate or used to increase the ammonia in the compost-
heap.

A mineral fertilizer very largely used as a top-dressing
for various crops, especially clover and Indian corn, is
ground gypsum, commonly known as land-plaster. This
substance is a sulphate of lime, and there is a wide diversity
of opinion as to the cause of the surprising results attending
its use in many cases. The Atlantic seaboard States are

RELATIONS OF GEOLOGY TO AGRICULTURE.

12$

supplied with it from Nova Scotia, where it is found in
enormous beds in rocks of Lower Carboniferous age.
New York has large deposits in rocks of the Salina period,
ranging from Oneida County westward, near the line of
the Erie Canal ; and it is quarried at many places and
shipped to considerable distances, both ground and un-
ground. Near Sandusky, O., it is obtained from rocks of
the same age, and prepared both for agricultural use and
for plaster of Paris. The great deposits in Michigan,
along Saginaw Bay and near Grand Rapids, are found in
rocks of the Lower Carboniferous ; and those at Fort
Dodge, Io., are associated with rocks of the same age,
these last deposits being of especial interest, because fur-
nishing this fertilizer to an extensive region otherwise
nearly destitute of it. Important beds of gypsum occur
in two sections of Kansas, in the western part of Virginia
on a branch of the Holston River, and in Pike County,
Ark., while vast supplies of it are known to exist in the
Triassic rocks of Texas. Great beds and lenticular masses
of this substance, often of wonderful purity, are known to
exist in nearly all the States and Territories of the far
West, partly, as in Arizona, in rocks of the Carboniferous
period, but chiefly in beds of the Triassic or of still later
geological age. It will thus be seen that most sections of
the United States and of the British Provinces are abun-
dantly supplied with this mineral fertilizer, and that it
occurs chiefly in rocks of the Salina, the Lower and Upper
Carboniferous, and Triassic periods. The European de-
posits are found chiefly in the Permian and Triassic, some
also occurring in the Eocene Tertiary. Besides their use
as fertilizers, many of these gypsum deposits are of suffi-
cient purity to be available for use in the arts as plaster of
Paris, more particular mention of which will be made in
another connection.

Common salt, also largely used as a fertilizer to supply
to plants soda and chlorine, is very widely distributed

126 APPLIED GEOLOGY.

over the United States and Canada, being obtained chiefly
from brine-wells sunk in rocks of the Salina period, in
western New York, largely at Syracuse and Warsaw, and
at Goderich in the Province of Ontario ; and in rocks of
the Lower Carboniferous and Carboniferous periods in
eastern Michigan, West Virginia, and the adjacent part of
Ohio. Great deposits of rock-salt are found at Petit Anse
in Louisiana, in materials of somewhat recent geological
formation, and throughout the far Western and Pacific
States and Territories abundant supplies await the devel-
opment of those regions. In these latter regions are also
found at several points mixtures of salt with sulphates and
nitrates of potash and soda, affording substances which
must ultimately become of great importance in agriculture
as sources of nitrogen and potash. Similar crude salts
are obtained for use in agriculture and for other purposes
from South America in the rainless western regions ; and
crude salts of potash used in European and American ag-
riculture are obtained from beds occurring in the Permian
salt deposits of Stassfurt in Germany.

What have here been briefly enumerated and described
are the chief fertilizers supplied to agriculture from geo-
logical sources, and the judicious use of which may be ex-
pected to increase largely the productive capacity of the
soil. The beneficial effects of some of these are produced
at once, and are quite limited in their duration, while
others, acting more gradually, constitute a permanent im-
provement of the soil. Both of these classes of fertilizers
may be used with advantage; but questions of expense
incurred, as compared with benefits received and returns
obtained, depend on many circumstances which belong
rather to the science and art of agriculture than to applied
geology.

Drainage and Subsoils. — The geological considera-
tions which influence drainage, whether undertaken in the
interests of agriculture, or for the promotion of healthful

RELATIONS OF GEOLOGY TO

surroundings, or for the reclamation of waste lan<
already been suggested on page 64. They consist in the
presence of a sufficient declivity to insure the easy passage
of water through under-drains, and ultimately the free
outflow of the collected waters of drainage, or, in the case
of flat-lying districts, in the possible existence in the sub-
soil or underlying rocks of porous beds or fissured and
jointed strata, which may serve as water-ways and afford
an underground outlet to drains and cess-pools ; or, on a
larger scale, in the removal of geological barriers and ob-
structions caused by geological agencies, such as have con-
verted tens of thousands of acres in central New York
into the pestilent fen called the Montezuma Marsh. An
example of the reclamation of a similar district by the re-
moval of a barrier has recently been presented by the suc-
cessful draining of the " Great Meadows " in Warren
County, N. J., where an area of five thousand five hun-
dred acres has been opened to cultivation, while the sur-
rounding region has been freed from a fruitful breeding-
place of malarial diseases. In all cases of difficult drainage
examination should be made of the structure of what lies
beneath the soil. Not unfrequently it may be found that
the need of drainage arises from the presence of a com-
paratively thin crust of hard-pan, and that if this be broken
up the difficulty will disappear. In a much greater pro-
portion of cases than would be supposed, also, porous or
fissured strata at no very considerable depths will furnish
an easy outlet for both farm and house drains, promoting
at the same time agricultural fertility and personal health
and comfort. Prof. Emmons, in his report on New York
agriculture, vol. i, calls marked attention to this too often
neglected means of drainage. Such an examination can
be easily and cheaply made, and, though it may not be
needed for the purpose of facilitating drainage, it will re-
veal to the agriculturist the nature and resources of his
subsoils, giving him information which is second in im-

128 APPLIED GEOLOGY.

portance only to a knowledge of the capabilities and needs
of the soil ; for the subsoil may aggravate the defects of
the arable surface by its tenacity or its permeability, or,
on the other hand, it may furnish a ready means of reme-
dying these defects by beneficial mixtures. Very fre-
quently it will be found capable of restoring to the soil
elements of fertility of which it may be measurably ex-
hausted, or it may even be found to contain at no great
depth unsuspected deposits of valuable fertilizers, as has
been found true already in many sections of our country.
Expedient as such careful examinations clearly are in all
ordinary cases, their importance becomes especially great
in regions where valuable fertilizers are known sometimes
to occur, as well as in those where it may reasonably be
suspected that deposits of valuable minerals like iron and
coal may exist. It has frequently happened that estates
have been sold merely for their value as farming-lands,
from the mineral resources of which well-instructed in-
vestors have derived great wealth — wealth, too, which the
former owners might have shared had they taken the pains
to make or procure a proper examination of their lands.
Scientific surveys made by governments can afford little
benefit to those who permit themselves to be ignorant of
their results, or who neglect to apply their teachings by
such careful local examinations as they ought obviously to

suggest.

Works which may profitably be consulted.

In general, the Geological and Agricultural Reports of one's own
State. " Natural History of New York, Agriculture," vol i ; " New
Jersey Geological Report," 1868, pp. 378-500; and 1879, pp. 103-
120; "Ohio Geological Report," 1870, pp 320-381 and pp. 452-
459; "Second Geological Report of Arkansas," p. 42-54 and pp.
171-179, etc. ; " Geological Report of North Carolina," 1875, pp.
162-217. The " Annual Report of New Jersey for 1870 " also con-
tains an account of the drainage of marshes. I have also been greatly
indebted in the preparation of this chapter to the following French
works : Meugy, " Geologic Applique"e a 1'Agriculture," and D'Orbigny
et Gente, " Geologic Applique"e aux Arts et a 1'Agriculture."

CHAPTER VII.

RELATIONS OF GEOLOGY TO HEALTH.

Two highly essential conditions of health for both in-
dividuals and communities are supplied by wholesome
water and pure air. Indeed, it can not be doubted that a
large part of the diseases to which human beings are liable
is due to the lack of one or both of these essentials. Both
are very largely dependent on geological agencies, or on
geological structure ; and hence it is proper that the im-
portant subject of sanitation should be considered here in
its geological aspects.

The purely geological sources of water-supply have al-
ready been discussed in the chapter on springs, wells, and
artesians, in which also were pointed out the dangers of
contamination, and the precautions needed in some cases
to secure a tolerable degree of purity. The importance
of the subject is so great, however, that there is little dan-
ger of its being pressed too strongly upon public attention ;
since, even with the wide diffusion of information with
regard to it, large numbers of people thoughtlessly persist
in exposing both health and life to imminent risk by the
use of readily obtainable water-supplies from sources pe-
culiarly liable to contamination, while quite generally also
showing a disposition to attribute the disorders resulting
from this carelessness to some other than the real cause.
Doubtless, a considerable portion of diseases incident to
the settlement of some of our new territories could be

130 APPLIED GEOLOGY.

avoided by the use of filtered rain-water ; while in thick-
ly settled villages and cities, the water of all wells, save
those most favored by the underground structure, and
most carefully guarded, can be used only at great risk
to health. Even in the case of deep driven wells passing
through thick beds of clay, a source of danger has re-
'cently been revealed, in the occasional corrosion of the
iron tubing by foul superficial waters, which may thus
gain unsuspected access to the domestic supply, suggest-
ing the expediency of a frequent examination of these
tubes, possibly by drawing up to view the portion that is
exposed to risk of corrosion. In any use of the water
from wells and from springs, save those from exception-
ally deep-seated and remote sources, safety can be assured
only by the exercise of intelligent care at the outset, and of
constant vigilance afterward. So limited, however, is the
supply from most of the geological sources, and so great
is the risk of dangerous contamination in those most
widely used, that nearly all large cities seek their water
from other sources. Many, like Philadelphia and St.
Louis, draw their supplies from the higher reaches of riv-
ers on which they are situated, trusting to the purifying
effects of atmospheric exposure to so far free the waters
from the organic impurities with which they are more or
less largely charged as to bring them within reasonable
limits of safety ; this source of supply being open to the
obvious objection that, whatever may be the present con-
dition of the water, it is sure to undergo a progressive de-
terioration from the growth of cities, villages, and manu-
factories on the upper course of the river, all of which will
discharge their waste into it ; not to speak of the impor-
tant increase in amount of organic matter that must find
its way into it from fields coming more widely into a high
state of cultivation. Other cities, like Chicago and Cleve-
land, drive expensive tunnels far out beneath great bodies
of fresh water, where the geological nature of the bottom

RELATIONS OF GEOLOGY TO HEALTH. 131

makes this feasible, deriving thereby abundant and unob-
jectionable supplies. Still others, like New York, construct
costly dams and reservoirs and aqueducts, to gather and
bring water from distant, sparsely settled, and elevated dis-
tricts ; in which case many important circumstances need
to be carefully weighed, some of which, and those of no
minor importance, involve questions of geological structure.
For not only is it necessary to consider the average amount
of rainfall and the extent of gathering-ground, but also the
geological character of the entire area becomes a matter
of serious importance, since it is sure to influence the
character of the water derived from it, and to condition
both the feasibility and the expense of the dams that are
to be constructed, and the ability of reservoirs to retain
the water that may be collected into them. The water
derived from a granitic area of catchment will differ
greatly from that drawn from a limestone region, or from
one underlaid with ferruginous sandstones and shales, and
containing, it may be, considerable tracts of swampy
ground. It is worthy of observation, also, that those dis-
tricts which are likely to yield the most unobjectionable
supplies of water are those least likely in the course of
time to attract a numerous population, and thus to furnish
an ultimate source of defilement. So, too, " the rocks of
one glen may be retentive and eminently suited for a
reservoir, while those of another may be so porous as to
cause perpetual leakage ; the rocks and springs of one
tunneled aqueduct might be innocuous to the supply,
while those of another might contaminate it with sa-
line and metallic impurities." (Page's "Economic Geolo-
gy.") It is evident, then, that the problem of wholesome
water-supply is by no means a very simple one, requiring,
in the case of small communities, the intelligent applica-
tion of geological principles and precautions ; while,
where great numbers are to be provided for within small
areas, it may tax the resources of the highest engineer-

132

APPLIED GEOLOGY.

ing ability, aided by no slight knowledge of structural
geology.

The securing of pure and healthful atmospheric condi-
tions is, in a very large degree, a matter of proper drain-
age. Malarious localities are usually wet or at least damp
ones, those in which certain forms of vegetation flourish
and decay, giving rise to unhealthful exhalations, to which
any organic waste from neighboring dwellings adds a deep-
er taint. When the damp spot is dried, the wet or marshy
tract drained of its superfluous water, the peculiar prod-
ucts of organic decomposition which cause disease cease
after a time to be supplied, and the region becomes more
salubrious. Drainage for sanitary purposes, as well as for
agricultural improvement, depends in numerous cases on
expedients suggested by facts of geological structure. Ac-
cording to the testimony of the Geological Survey of New
Jersey ("Report" of 1880), the drainage of the Great
Meadows in that State by the removal of a geological ob-
struction has been quite as marked a success for sanita-
tion as for agriculture, as is shown in the striking decrease
of malarial diseases in the surrounding region. This is
but one of many instances that could be given, where the
sanitary improvement of considerable tracts of *' drowned
lands " could be effected by the removal of geologically
formed barriers to drainage. The reports of engineers
show that the vast malarial region previously mentioned
as the Montezuma Marshes, in central New York, owes
its existence to such a barrier, and that its restoration to
healthfulness can be effected only by the removal of this
barrier. Of similar import is the necessity for sanitation,
in grading portions of cities where great hollows occur
surrounded by impervious barriers, of making sufficient
provision for the under-drainage of these hollows before
filling them up for building. Otherwise, even if unobjec-
tionable materials are used in the filling, they are destined,
through percolation from the streets and leakage from im-

RELATIONS OF GEOLOGY TO HEALTH.

133

perfect sewers, to become ultimately subterranean reser-
voirs of filth, the emanations from which can not but affect
unfavorably the health of such localities. The sewerage
systems of cities will always present some questions of
geological significance. The course of the main sewers is
naturally dictated by the slope of the ground, the oppor-
tunities for safe outlet, and, not unfrequently also, by the
relative expense of excavation. Besides this, in some lo-
calities, the only desirable object may be the safe convey-
ance of sewage, while in others it may be highly desirable
to provide also for the drainage of wet tracts ; such con-
siderations, in either case, controlling the choice of the
materials with which the sewer should be constructed. In
villages and small cities, where no general sewerage sys-
tem is provided, the needful sanitary arrangements for
dwellings must depend mainly upon supplying subterra-
nean outlets through porous beds for superfluous or con-
taminated fluids. Where, from the nature of the under-
ground structure, such drainage is not practicable, careful
provision should be made for the frequent disinfection and
proper discharge of impervious receptacles. When porous
beds are made the outlets for house-drainage, it should
always be borne in mind that any water-supplies derived
from them will inevitably be contaminated. Sewage, how-
ever filtered and diluted, is not a fit beverage for human
use. Numerous cases of severe and often fatal illness can,
with a little care, be traced to this cause.

Should any one think that such careful provision for
pure water and untainted air as has here been suggested is
unnecessary, or too troublesome, it will be well to reflect
that it accords with the uniform experience of civilized
mankind ; and that matters of such vital consequence as
the health and happiness of human beings are too serious
to be trusted to chance. All experience has shown that
regions well drained and supplied with wholesome water
are healthful ones ; that cities kept properly clean and

134 APPLIED GEOLOGY.

abundantly supplied with pure water show a diminished
death-rate ; that great epidemics, like cholera and yellow
fever, either leave such cities and regions unscathed, or
visit them with greatly mitigated violence, having their
breeding-places in regions of filth, and confining their
ravages chiefly to uncleanly and badly watered localities ;
and that diseases like diphtheria and typhoid fever can
usually be traced to defective drainage and impure water.

CHAPTER VIII.

MINERAL FUELS.

AMONG all the mineral substances procured from the
earth, the mineral fuels doubtless hold a foremost rank in
importance, contesting even with iron for the supremacy
in supplying the wants of civilized man. Indeed, the in-
dustrial rank of nations may be very accurately judged
from the extent to which they utilize their fuel supplies.
Great Britain, the United States, and Germany, the three
foremost manufacturing nations, produce four fifths of the
mineral fuels of the entire globe.

These highly important substances, whether anthra-
cites, bituminous coals, lignites, or peat, are generally con-
ceded to have resulted from a peculiar decomposition of
vegetable tissues. There are a number of questions as to
the particular mode in which these deposits originated,
and the special forms and portions of vegetation that fur-
nished their chief materials, which, although they are of
much theoretical interest, are yet not of such practical im-
portance to the student of economical geology as to claim
our consideration here. It is sufficient for our present
purpose to observe that the chief constituents of all vege-
table tissue are carbon, oxygen, and hydrogen, with small
proportions of nitrogen and some earthy substances.
When these tissues decay or are burned with free access of
air, their elements are dissipated in the form of carbonic
acid and watery vapor, and ultimately nothing remains

136 APPLIED GEOLOGY.

but an inorganic residue constituting the ash of the
plants. When, however, vegetable substances undergo
decay out of contact with the air, whether covered with
earth or heaped together in wet places, and partly or
wholly covered with water, the changes that take place in
them are due mainly to chemical rearrangements that
occur among their own elements. Of these, the oxygen
unites with somewhat more than one third its own weight
of carbon and with one eighth its weight of hydrogen to
form carbonic acid and water. A portion of the hydrogen
also unites with one third its weight of carbon to form
marsh-gas, the fire-damp of coal-mines. The result of
these several changes is that the relative amount of oxygen
in the mass is diminished, while that of carbon, originally
about one half of the whole, is increased ; the color be-
comes darker, first brown, then nearly or quite black,
from the increasing preponderance of coaly carbon, while
the relative proportion of hydrogen is but slightly changed.
The resulting substance, in the slow process of ages of this
kind of change, passes through the condition of peat or
brown coal, to become what is known as bituminous coal,
or ultimately to be converted into anthracite, in some
much-disturbed regions where probably heat accelerated
the dissipation of most of the oxygen and hydrogen still
remaining in the coal. That this process of chemical
change is a gradual and protracted one, continuing even
to the present day, is shown by the fact that marsh-gas
and carbonic acid, or " choke-damp," are still eliminated
from most coal-beds, and present some of the most
dreaded dangers of coal-mining, against which careful
provisions for ventilation, and the use of safety-lamps, do
not always avail to prevent frightful casualties. Thus
oxygen, useless as a fuel, is progressively eliminated, while
the combustible elements, carbon and hydrogen, become
ever more dominant, during the process by which coal is
formed. By reference to the table of analyses given on a

MINERAL FUELS. 137

subsequent page, it may be seen that, in the course of this
series of changes, the carbon, from being originally a little
less than 50 per cent of the whole, becomes 60 per cent in
well-formed peat, more than 66 per cent in brown coal»
from 70 to more than 80 per cent in ordinary bituminous
coal, and finally 90 per cent or more in anthracite ; that
the hydrogen, originally 6^ per cent, remains tolerably
uniform in relative amount till the anthracites are reached,
when it becomes, together with other volatile ingredients,
not more than from 3 to 10 per cent, while oxygen dimin-
ishes from 43 per cent to an average of about 10 per cent
in bituminous coals (a considerable portion of this being
due to the presence of water), and to a much smaller
amount in anthracite.

Now, these progressive changes in the relative propor-
tions of the constituent elements are attended with con-
siderable differences in the physical character of the suc-
cessive products, and in their behavior when used as fuels.
On these differences has been based a convenient prac-
tical classification of those variable substances called
collectively mineral coals. This classification is primarily
into anthracite and bituminous coal, the first of which
neither softens nor swells in burning, yielding no smoke
and little or no yellow flame, while the second softens and
often swells in the fire, emitting much smoke and abun-
dant yellow flame. These two great classes admit of a
somewhat convenient subdivision, not always observed in
practice, into hard and semi-anthracites, semi-bituminous
and bituminous coals — a subdivision which is based on the
relative proportion of volatile combustible substances con-
tained in them, together with certain tolerably well-marked
differences in their physical characters.

The hard anthracites, which usually contain less than
5 per cent of combustible gases, kindle with difficulty, and
burn with an intense heat and little blue flame, have a
more or less marked conchoidal fracture, a brilliant luster,

138 APPLIED GEOLOGY.

and a specific gravity of from 1.5 to 1.8, being the heaviest
and hardest of all coals.

The semi-anthracites, containing from 5 to 1 1 per cent
of volatile combustible materials, kindle and burn more
readily than the former class, giving a strong heat, often
accompanied at first with a little yellow flame. They
have a specific gravity of from 1.4 to 1.5 and sometimes
more, are softer and less lustrous than the hard anthra-
cites, and have usually an angular fracture with a tend-
ency to break up while burning.

The semi-bituminous coals have from 12 to 20 per cent
of volatile constituents and a specific gravity between 1.3
and 1.45, while the bituminous coals have more than 20 per
cent of volatile matter, and their specific gravity is from
1.2 to 1.35, that of some of the Ohio coals being even
more than 1.4, though the average gravity of this class of
coals is less than 1.3. Both these kinds of coal liberate a
part of their volatile matter, when heated, in the state of a
dense oily liquid resembling bitumen, whence their name ;
they also emit a bituminous odor when burning. A further
subdivision of the bituminous coals is made on physical
characters of much economical importance, into caking,
cherry, splint or block, and cannel coals.

The caking coals, when heated, soften greatly, and the
fragments fuse together, or agglutinate into an adhesive
mass, which is puffed up, by the gases liberated by the
heat, into a hard and highly cellular substance called
coke, consisting of the fixed carbon and mineral matters
originally present in the coal. This property fits them to
be used for the manufacture of coke, and for purposes
where a " hollow fire " is desirable, as in blacksmithing,
while rendering them much less convenient for domestic
use.

The cherry coals, which owe their name to the beauty
of their appearance, are usually highly lustrous but very
brittle coals, which do not agglutinate when heated.

MINERAL FUELS.

139

Their brittleness gives rise to a great amount of waste in
mining and transportation, while their lack of adhesive-
ness when heated fits them for use as a domestic fuel.

The splint or block coals are hard, highly laminated,
and difficult to be broken across, have a dull luster, and
do not agglutinate when heated. Their properties adapt
them especially for use in iron-smelting, for which they
are largely utilized. They are often called dry-burning or
open-burning coals, a name equally applicable to any of
the non-agglutinating coals.

The cannels, of which Prof. H. D. Rogers proposed to
make a distinct primary class under the name of hydro-
genous coals, are characterized by their large proportion
of volatile matter and their small amount of coke-like
residue, their dull luster, their conchoidal or slaty fracture,
and their tendency to split when burning with a crackling
noise, somewhat like the chatter of a parrot, whence they
are often called parrot-coals. They derive the name can-
nel (i. e., candle) coals from the readiness with which they
take fire, and the cheerful flame with which they burn.
This makes them favorites for use in open grates ; they
are also largely used in making illuminating gas.

The lignites or brown coals are of much more recent
geological origin, and usually much less completely car-
bonized, than those which have just been described.
They are called lignites, because they frequently exhibit
the woody structure of the plants from which they are de-
rived, from the Latin word for wood, and brown coals,
from their color or that of their powder. They burn read-
ily without fusing, and emit a sooty smoke and a disagree-
able smell. The lignites, as a class, contain a much larger
proportion of water than other coals — a circumstance
which greatly diminishes their value as fuel, since so large
a portion of their heating power is wasted in converting
into steam the water which they contain. The lignitic
coals, which occupy vast areas in the western part of this

140

APPLIED GEOLOGY.

continent, differ widely in quality. Some are hardly dis-
tinguishable in appearance or character from the true bi-
tuminous coals, having but a small per cent of water, and
being sometimes capable of yielding a good coke ; while
others have a high per cent of water, often from 12 to 20
per cent, and crumble to a coarse powder when exposed
to the air, being on both accounts very indifferent fuel.

It will be convenient, for purposes of reference, to re-
sume in tabular form the classification of the mineral
fuels, with the characters on which chiefly it is based, omit-
ting for the present any consideration of peat :

Anthracites — do not soft-
en ; no smoke ; little

flame.

Hard anthracite — volatile to 5 per cent ;
sp. gr. 1.5 to 1.8; hard; lustrous;
conchoidal fracture.

Semi-anthracite — volatile 6 to n per
cent ; sp. gr. 1.4 to 1.5 ; less hard ;
luster dull ; fracture angular.
Semi-bituminous — volatile 12 to 20 per

cent ; sp. gr. 1.3 to I 45.
Bituminous — volatile above 20 per cent ;

sp. gr. 1.2 to 1.4.
Caking — agglutinates.
Cherry — non-agglutinating ; lustrous ;

brittle.
Splint or block — non - agglutinating ;

dull ; tough ; laminated.
Cannel — largely volatile ; dull luster ;
I conchoidal or slaty fracture.

Lignite — brown powder ; usually contains much water ; no fusion ;
sooty smoke ; bad smell.

Bituminous — soften ; yield
oily fluid ; much smoke
and flame. . . .

The following table of analyses, derived from various
sources, is given to illustrate the composition of the vari-
ous classes and kinds of mineral fuel ; to which is added
an average analysis of woody tissue derived from several
different kinds of tissue. About one half of these are what
are called proximate analyses, i. e., those giving only the per-
centages of fixed carbon, volatile constituents, and ash,
with sometimes those also of water and sulphur. The re-

MINERAL FUELS.

141

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I42 APPLIED GEOLOGY.

mainder are ultimate analyses, giving the percentage of all
the elements ; while five of them, taken from the " Geo-
logical Report of Ohio," 1870, combine both forms of
analysis :

Geological Associations of Mineral Fuels.— The
coals and lignites occur as beds of varying thickness, in-
terstratified with other beds of sandstones, shales, fire-
clays, and occasionally limestones. The coal-beds, or
seams, as they are frequently called, vary in thickness
from the fraction of an inch to many feet. The Mammoth
bed, in the Pennsylvania anthracite region, measures, at
two points mentioned by Ashburner, one hundred and one
hundred and fourteen feet, ranging between sixty and ninety
feet over a large area in the Black Creek basin ; while at St.
Etienne, near Lyons, France, the main coal, according to
Geikie, averages forty feet in thickness, and swells out oc-
casionally to as much as one hundred and thirty feet. The
main seam at Pictou, Nova Scotia, is about forty feet in
thickness, and the Xaveri seam in Upper Silesia is, ac-
cording to Credner, sixteen metres or over fifty-two feet
thick. On the other hand, in every coal-region there are
large numbers of very thin seams which are economically
worthless, a thickness of three feet being usually consid-
ered as small as can be profitably worked by underground
operations. Of the eighty or more seams found along the
head of the Bay of Fundy, not more than four or five are
workable. Southern Wales has twenty-three workable
seams out of more than eighty. Southern Russia is said
to have, on the river Donetz, as many as two hundred and
twenty-five coal-seams, of which but forty-four are consid-
ered worth working ; while of the one hundred and thirty-
two seams in the Westphalian coal-field, near the Rhine,
seventy-four are workable. These few examples, which
could be greatly multiplied, will serve to show both the
wide variations in thickness which coal-beds, like other
strata, may assume, and also the extent to which they may

MINERAL FUELS.

143

alternate with other rocks in the series of strata or meas-
ures in which they occur. Very thick coal-seams, like
some of those mentioned above, are by no means made up
entirely of coal. They are nearly always separated, by
seams of shaly matter or of very impure coal, into several
subordinate layers or benches, which often differ consider-
ably in character. Thus the Mammoth seam, where it is
one hundred and fourteen feet thick, has eight feet of
rock other than coal interlaminated with it ; and the Pictou
main seam, where nearly forty feet thick, affords but about
twenty-four feet of good coal, being interstratified with six
bands of shale and ironstone or coarse impure coals.

Besides the seams of coal, the rock series, constituting
coal-measures, is made up of various alternations of sand-
stones, fire-clays, shales containing not unfrequently valu-
able deposits of clay ironstone, and, less frequently, strata
of limestone. Occasionally, also, there occur in some re-
gions seams of highly bituminous iron carbonate called
black-band iron-ore, highly esteemed as a source of iron.
The coal-seams are almost invariably found to be under-
laid by a bed of fire-clay, or of clayey sandstone, varying
from a few inches to several feet in thickness, and contain-
ing usually great numbers of fossil roots and curiously
pitted stumps, called stigmarice, which are evidently the
remnants of a former vegetation that grew on them as
soils. These under-days are therefore generally believed
to be the ancient dirt-beds from which sprang the vegeta-
tion that was transformed into coal. The under-clays are
often found to be clays of such purity as to be capable,
after being properly disintegrated by weathering, of being
wrought into pottery, or molded into highly refractory
fire-brick, whence their name of fire-clays. Their refrac-
tory character is, in all probability, due to the circumstance
that the vegetation of the coal-beds withdrew from them
those ingredients, like potash and lime, which cause clays
to fuse at very high temperatures. (Newberry.)

144 APPLIED GEOLOGY.

Aside from the usual position of the under-clays, there
is no fixed order of sequence of the strata which make up
coal-measures ; though it is very common to find a layer,
sometimes quite thin, of bituminous shale, or very shaly
coal filled with leaves and fragments of plants, resting im-
mediately on the coal-seam. The nature of the strata
which immediately overlie the coal is a matter of great
practical importance, since upon it depend very much the
ease and safety with which the coal may be mined. A
roof of firm, thick-bedded sandstone greatly facilitates
mining operations; while one of slippery and shivery
shales is sure to cause difficulty and danger. Sandstones?
however, sometimes present a curious danger of their own,
in the form of what are called coal-pipes, the skeletons of
ancient trunks of trees extending in a nearly vertical di-
rection through the strata, the place of the bark being
occupied by a tender film of coal, while that of the wood
is filled with a solid column of sandstone. These, enlarg-
ing downward and generally destitute of branches, are
easily dislodged, and in their fall crush whatever may be
underneath, a peculiar example, as Lyell remarks, of the
long-deferred action of gravity.

But though the various kinds of rocks which make up
coal-measures in general present no settled order of rela-
tive arrangement, yet in any particular coal-field the lead-
ing strata, though often varying considerably in thickness,
commonly show a surprising and very helpful degree of
persistency in character and relative position. This is
true, within limited areas, of some of the more important
sandstone strata, but is more widely true of the leading
seams of coal and limestone. For instance, Prof. H. D.
Rogers estimates .that the great Pittsburg seam of the Ap-
palachian coal-field underlies an area of not less than
fourteen thousand square miles, in a continuous sheet of
varying thickness, some other coal-seams showing a simi-
lar constancy of position, though probably more limited in

MINERAL FUELS. 145

extent. In like manner, some of the limestones of the
Pennsylvania coal series are recognized in similar posi-
tions in Ohio, where they are found persistent over large
areas. Thus these persistent strata, whether of coal, of
limestone, or sometimes of sandstone, become valuable
standards of reference, or key-rocks, for determining the
existence and the position of the useful rocks, which have
been observed at some points to lie at a certain distance
below or above them, due allowance being made for possi-
ble local changes in character and thickness of strata.

To illustrate what has been said as to the mode of oc-
currence and associates of coal-seams, and as to persistent
strata, the following general section of the lower coal-
measures of Ohio has been taken from the second volume
of the Ohio Geological Report :

Thickness in feet.

36. Red and gray shales of barren measures

35. Stillwater sandstone, often conglomerate o to 50

34. Gray shale alternating with No. 35 o „ 50

33. Buff limestone, ferruginous " mountain ore ".... o „ 10

32. Blackband iron-ore, often replacing No. 33. ... o „ 14

31. Coal No. 7, " Cambridge," etc., seam 2 „ 7

30. Fire-clay 3 „ 5

29. Limestone in eastern and southern counties. ... o „ TO

28. Shale and sandstone 40 „ 50

27. Coal No. 6 a, or " Norris" coal, sometimes with

limestone over it o „ 6

26. Fire-clay 3 „ 5

25. Mahoning sandstone, often conglomerate o „ 50

24. Gray or black shale, alternating with No. 25... . 5 „ 50
23. Coal No. 6, " Straitsville " or "Big Vein" —

Upper Freeport of Pennsylvania 3 „ 12

22. Fire-clay 3 „ 5

21. Limestone in eastern counties = Freeport of

Pennsylvania 2 „ 8

21. Gray or black shale, nodular ii-on-ore at base ... 25 „ 50
20. Coal No. 5, " Mineral Point," " Newberry "

= " Lower Freeport " of Pennsylvania 2 „ 5

19. Fire-clay, often non-plastic and excellent 3 „ 6

18. Shale and sandstone 20 ,,4°

I46 APPLIED GEOLOGY.

Thickness in feet.

17. Limestone, " Putnam Hill " or " Gray " 2 to 8

16. Coal No. 4, often double, " Flint Ridge cannel "

= " Kittanning " of Pennsylvania i „ 7

15. Fire-clay 2 „ 12

14. Shale and sandstone, sometimes with coal 3 a. . 20 „ 90
13. Blue limestone with iron-ore = Ferriferous of

Pennsylvania 2 „ 6

12. Coal No. 3, " Creek vein " i „ 3

II. Fire-clay, extensively used for pottery 5 „ 15

10. Shale and sandstone, " Tionesta " sandstone.. . 30 „ 50

9. Coal No. 2, generally thin, " Strawbridge " coal I „ 5

" 8. Fire-clay I „ 3

7. Shale 20 „ 50

6. Massillon sandstone 20 „ 80

5. Gray shale 5 ,,40

4. Coal No. i, " Brier Hill," " Massillon " 3 „ 6

3. Fire-clay 3 „ 5

2. Sandstone and shale 10 ,, 50

I. Conglomerate — —

The average thickness of the rocks in this section is
about four hundred feet, and a considerable number of
the strata included in it are recognized as identical with
those holding corresponding positions in the lower coal
series of Pennsylvania. In this series of four hundred
feet of strata there is a maximum thickness of fifty-one
feet of coal, with a probable average of about twenty-five
feet or one foot of coal to sixteen feet of the measures.
This is doubtless considerably above the average ratio of
coal to rock. In the Pictou coal-field there is one foot
of good coal to about twenty-six feet of poor coal and
rock ; in that of Illinois, one to twenty-five or thirty feet ;
in the Saarbriick area, the ratio is one to twenty-six ; in
that of Westphalia, one foot of workable coal to thirty-
two feet of rock ; and in the Southern Wales coal-basin,
if the entire thickness of the Carboniferous rocks be con-
sidered, which is said to be twelve thousand feet, the ratio
is about one to one hundred.

In nearly all cases, areas of coal-measures are basin-

MINERAL FUELS. 147

shaped — that is, they thin out on all sides as they approach
their limits, and are surrounded by older rocks, somewhat
like a picture set in a frame. They owe this form occasion-
ally, it is probable, to the original form of the area in
which they were deposited. This appears to be true of the
great Appalachian coal-field as a whole, which seems to
have been deposited in a long and shallow trough, inclosed
on one side by land which now forms the crests of the
Appalachians, and on the other by a low anticlinal ridge,
extending through western Ohio and central Kentucky,
the bottom of this trough having evidently been lowered
by gradual subsidence to permit the deposition of the suc-
cessive strata. In a case like this, the chief upper coal-
seams would be likely to be more extended than those
lower in the series, as is true of the Pittsburg seam. In
much the greater number of instances, however, the basin-
form is due to disturbances of position that have taken
place since the rocks were deposited ; the strata, by move-
ments of the earth's crust, having been thrown into folds,
sometimes wide and gentle, sometimes very abrupt; and
when the crests of these folds have been removed by subse-
quent denudation, areas once continuous have been left
as isolated, basin-shaped remnants. A striking illustra-
tion of this is presented in the sharply folded and denuded
anthracite basins of Pennsylvania ; while it is probable
that the present separation of the coal areas of Illinois
and Missouri is due to the denudation of a wide and
gentle fold, cutting away the strata down to the rocks that
underlie the coal. In these latter cases, the chief lower
coal-beds would be likely to be most extended and contin-
uous, the upper ones being largely swept away.

Geological Horizons of Mineral Fuels. — Al-
though thin layers of carbonaceous matter are occasion-
ally met with in rocks of Silurian and Devonian age, and
even, as stated by Murchison, a small deposit of anthra-
cite, from one to twelve feet thick, occurs in the Lower Si-

1 48 APPLIED GEOLOGY.

lurian of Ireland, the material for which has apparently
been derived from masses of sea-weeds, yet no beds of
mineral fuel, of any considerable economic importance or
reliability, have yet been found below that series of rocks
which is called the Carboniferous, from the great preva-
lence in it of land-plants and beds of coal. The strata
of the middle portion of this series are frequently called
the coal-measures par excellence, because they furnish very
much the largest part of the mineral fuel of the world,
although coal-measures of great importance occur at sev-
eral other geological horizons presently to be mentioned.
The carboniferous rocks, omitting the upper or Permian
portion, which is not coal-bearing and has little develop-
ment on this continent, admit of the following subdivisions,
recognizable in a general way in most American localities
of these rocks, and nearly all of which, under various
names, are found also in the European Carboniferous :

7. Upper barren measures — with thin coals ; Washing-
ton seam workable in West Virginia.

6. Upper productive measures — Pittsburg seam the
chief, in Appalachian area.

5. Lower barren measures — Mahoning sandstone at
base, with thin coals.

4. Lower productive coal-measures.

3. Millstone grit, or conglomerate.

2. Sub-conglomerate measures — coals of Arkansas;
Sharon coal of Pennsylvania ; lower or " edge coals " of
Scotland ; coal horizon of Russia and northern Spain.

i. Sub-carboniferous limestone, etc.

The uppermost of these subdivisions is thought by
Messrs. White and Fontaine to show Permian characters
in West Virginia, where it contains a three-foot seam of
coal, besides several thin seams.

The upper productive coal-measures (6) have their
greatest economic importance in the Appalachian coal
area, and in western Kentucky. The lower productive

MINERAL FUELS.

149

coal series is the most widely reliable of all, in both
America and Europe ; while the millstone grit, usually
considered the base of the coal-bearing series, and hence
sometimes called the Farewell rock, because when it is
reached in mining the miners consider that they bid fare-
well to further hopes of coal, still has beneath it the coal-
bearing rocks of Arkansas and northern Spain, most if
not all those of Russia, and the lower or " edge coals " of
Scotland.

Above the geological horizon of the Carboniferous, val-
uable measures of coal of the usual character are found in
rocks of probable Triassic age, in central Virginia and
North Carolina, and also in the Lower Oolite, a subdivision
of the Jurassic, of Great Britain. Next in importance to
the Carboniferous, on this continent, as a horizon of min-
eral fuel, is the rock series of probable Upper Cretaceous
age, whose vast and wide-spread measures of lignitic coal
are of so great importance to the development of the re-
gion lying west of the Missouri River.

Valuable deposits of brown coal are found in Europe
in the Middle Tertiary, and are extensively utilized in
Germany and Austria, but none of importance have yet
been found in the Tertiary of North America. Thus the
geological horizons of mineral fuels are :

7. Middle Tertiary — brown coals.

6. Upper Cretaceous — lignitic coals.

5. Lower Oolite in Great Britain — bituminous.

4. Triassic — bituminous chiefly.

3. Upper productive measures of Carboniferous.

2. Lower productive measures of Carboniferous.

i. Sub-conglomerate coal of Carboniferous.

Regions of Mineral Fuel. — The easternmost coal
area of North America is that of northern Nova Scotia,
east New Brunswick, and Cape Breton Island. It covers
about eighteen thousand square miles, much of which
seems likely to be of little value. There is a small area in

150 APPLIED GEOLOGY.

Rhode Island, extending a little way into Massachusetts,
and containing about five hundred square miles, the coal
of which is a very hard variety of anthracite. It is not
largely worked, the product reported in 1882 being only
ten thousand tons.

In Jhe extent, variety, and excellence of its coal-beds,
the Appalachian area surpasses any other on this conti-
nent, or indeed in the world. This vast coal-field, covering
nearly fifty-nine thousand square miles, occupies a large
part of western Pennsylvania and West Virginia, the western
extremity of Maryland and Virginia, southeastern Ohio,
the eastern part of Kentucky and Tennessee, and northern
Alabama, with a corner of Georgia. The northeast ex-
tremity of this area furnishes the anthracite of Pennsyl-
vania, the best in the world, in several detached basins
carved out of the folds of the Alleghanies, and contain-
ing in all about four hundred and seventy square miles.
In the Appalachian area, workable coal is obtained from
all the coal-bearing horizons of the Carboniferous that
have been enumerated, stretching from the Sharon sub-
conglomerate seam in No. 2 of our section, p. 148, to the
Washington seam in the upper barren measures, No. 7.
The Pittsburg seam, so celebrated for its vast extent, its
considerable thickness, and the superiority of its coal for
coking purposes, is at the base of the upper productive
measures, No. 6 ; while most of the coal of Ohio is ob-
tained from the lower productive measures, No. 4.

The Illinois coal-field covers a large part of central
and southern Illinois, the southwestern part of Indiana,
and the western portion of Kentucky, occupying somewhat
more than forty-seven thousand square miles. This area
is producing large and rapidly increasing amounts of bitu-
minous coals, chiefly from the lower productive measures,
with some in Kentucky from the upper productive.

The largest in superficial extent of the Carboniferous
coal areas is the Western one, occupying, it is estimated,

MINERAL FUELS. 151

seventy-nine thousand square miles, in southwestern Iowa,
northern and western Missouri, eastern Kansas and In-
dian Territory, northern Texas, and western Arkansas.
Over much of this area the coal-seams are thin, and the
coal not of the best quality. The producing horizons are
chiefly the sub-conglomerate measures in Arkansas, some
of -whose coals are semi-anthracites, and the lower pro-
ductive measures in Missouri and Iowa. The largest pro-
duction is from Iowa and Missouri, Kansas also furnish-
ing nearly a million tons annually.

Besides these there is a rudely circular area in central
Michigan, covering about six thousand seven hundred
square miles with Carboniferous coal-measure rocks, about
three hundred feet in maximum thickness, which contain,
at several points, one seam three to four feet thick of bi-
tuminous coal, somewhat sulphurous, but considered a
good fuel for steam purposes. The area seems not to be
very promising for a large coal production.

The Triassic coal-fields of Virginia and North Caroli-
na occupy four narrow, elongated basins running parallel
with the Blue Ridge Mountains in the east central part
of those States. These areas, although some of them have
been long known, have been as yet but little developed.
The one best known and most largely worked is in the
near vicinity of Richmond, where one of its seams attains
sometimes a thickness of forty feet. The coal is highly
bituminous, as is also that of the other basins, save that
of the Dan River in North Carolina, stretching into Vir-
ginia, which is shown by analyses to be semi-bituminous.
The productive area of the several basins does not proba-
bly reach five hundred square miles.

The lignitic coal-fields of probable Upper Cretaceous
age, in the far Western States and Territories, have not yet
been sufficiently explored to give more than a vague ap-
proximation to their extent ; but they are known to cover
vast areas, especially in Colorado, Wyoming, Dakota, and

152 APPLIED GEOLOGY.

Montana. Those best known and most largely worked at
present are those along the eastern base of the Rocky
Mountains, through much of Colorado, and extending
some distance into New Mexico ; those along the Union
Pacific Railway in southern Wyoming ; those on the Weber
River, and at other points, at no great distance from Salt
Lake City in Utah ; on Bellingham Bay and Puget Sound,
in Washington Territory ; and at Mount Diablo, near San
Francisco, California. Several seams of superior anthra-
cite and bituminous coal occur twenty-five miles south-
west of Santa Fe, New Mexico.

Valuable deposits of anthracite and coking bituminous
coal are found at Crested Butte, on the upper branches
of the Gunnison River in Colorado, and are coming into
extensive use ; while near Durango, in the same State,
and extending south into New Mexico, are enormous de-
posits of lignitic coal of excellent quality, some of the
seams being said to range from twelve to near ninety feet
in thickness. Valuable deposits occur also at Coos Bay
in Oregon, and in Vancouver's Island. Rough estimates
assign to the lignitic measures of Colorado about thirty
thousand square miles of area, and to those of Wyoming
twenty thousand square miles ; but those which claim for
Montana sixty thousand square miles, and for Dakota one
hundred thousand square miles of coal-bearing territory,
appear likely to be great overestimates.

As has already been remarked, the lignitic coals pre-
sent very wide variations in character and value. Some,
like parts of the seams of Crested Butte and Santa Fe, are
anthracites, apparently equal in quality to those of Penn-
sylvania ; others, like those of southern Colorado and ad-
jacent parts of New Mexico, and part of those at Crested
Butte, are coking coals which furnish a superior coke.
Some, like those of Cafion City, Colorado, and part of
those in Wyoming, are firm and open-burning, with a low
per cent of water, much resembling " block-coal " ; while

MINERAL FUELS. 153

many others have much water, and crumble readily on ex-
posure, hence furnishing an inferior fuel. All kinds, with
the increase of population and the growth of mining and
other industries, are destined to be eagerly sought out,
and to furnish supplies of inestimable value to a vast re-
gion otherwise scantily supplied with fuel. Six of the
Western States and Territories had already, in 1882, a re-
ported production of two million three hundred and fifty
thousand gross tons, ranging from about one hundred and
fifty thousand tons each in California and New Mexico,
to nearly a million tons in Colorado, and two thirds as
much in Wyoming.

Foreign Coal-Fields. — The chief coal areas of Eu-
rope are those of Great Britain, Belgium and France,
Germany and Austria, southern Russia, and Spain. The
coal-fields which have long given England its industrial
supremacy occupy an area of less than twelve thousand
square miles, and extend, in many separate basins, from
South Wales, northeasterly through western England to
the great Newcastle coal-field on the North Sea, with
areas of sub-conglomerate coals in southern Scotland.
All these areas of any considerable importance belong to
the Carboniferous age, and the coal is mostly bituminous,
with some valuable anthracite in South Wales.

The Belgian coal-field, of five hundred and eighteen
square miles area, extends in a lengthened belt eastward
from near Valenciennes, in France, to Aix-la-Chapelle ;
and its apparent eastern continuation across the Rhine
forms the great Westphalian coal-field northeast of Diis-
seldorf.

The coal-fields of Germany, with an area of about
eighteen hundred square miles, consist of several basins,
mostly small in extent, the chief of which are those of West-
phalia and Saarbruck, near the Rhine, Upper and Lower
Silesia, and some small basins in Saxony. There are also
important deposits of lignite in the Tertiary of North

154 APPLIED GEOLOGY.

Germany, some of them of great thickness. Austria has
coal-fields and deposits of lignite of considerable extent in
Bohemia.

Russia, which is credited with about thirty thousand
square miles of coal territory, has a large portion of this in
the more central provinces, supplied with but a few thin
seams of inferior coal ; its most valuable coal area being
about eleven thousand square miles on the river Donetz,
with one hundred and fourteen feet of workable coal, at
the geological horizon of the millstone grit. (Credner and
Murchison.)

The coal-fields of France aggregate two thousand and
eighty-six square miles, in many isolated basins, scattered
widely over its territory, some of which contain anthracite
coal. Some of the more noteworthy are those of Valen-
ciennes near the borders of Belgium, of Autun, and of
St. Etienne, previously mentioned, in the southern part.
In some of these basins the coal series occurs in the sub-
conglomerate, but in most, at the usual horizon of the
Carboniferous coal-measures.

The Spanish Peninsula has three thousand five hun-
dred and one square miles of 'coal area, chiefly in the
province of the Asturias, in the north part of the king-
dom, and on the southern declivity of the Sierra More-
na, both in rocks subordinate to the Carboniferous con-
glomerate.

India is reported to have about two thousand square
miles of coal-fields, chiefly of Triassic age, and Japan five
thousand square miles in the Tertiary. China is known
to be exceptionally rich in coal, of Triassic or Lower Ju-
rassic age, with some Carboniferous coal in the province
of Hunan ; but our knowledge of that country is too im-
perfect to permit any estimate of the area which bears
coal-seams. The map published by Prof. Pumpelly, in
the " Smithsonian Contributions," indicates the possibility
that a very large portion of China proper is covered by

MINERAL FUELS.

155

rocks pf the same age with those that bear valuable coal-
seams at many known points. Further than this our
knowledge does not extend. It is also reported that coal-
beds, of Carboniferous, Jurassic, and Tertiary age, occur
in Siberia.

True Carboniferous rocks with coal-seams are found
in the eastern colonies of Australia, and especially in New
South Wales, where there are said to be a number of beds
of coal ranging from three to thirty feet in thickness.
The following table, the materials for which are taken
with slight change from the report on mineral resources
of the United States, will give in compact form the prob-
able areas of fossil fuels in the various countries, with
their reported or estimated production in 1881 :

AREAS.

Square miles.

PRODUCTION.

Gross tons.

Great Britain

II,QOO

I £4 184 7QO

United States . ... ....

IQI QQ4

76 67Q 4QI

I.77O

6l ^4O 47^

France .

2 086

IQ QOO O^7

Austria ..

I 8OO

19 ooo ooo

5l8

1 7, c OO.OOO

India . .

2 OO4

4 ooo ooo

Russia

3O,OOO'

a 2<CR OOO

24,840

1,771:, 224

Nova Scotia, etc .... . .

18 oco

I 124 27O

Spain . ...

•i CQI

800 ooo

Japan

«5,ooo

8OO,OOO

Vancouver's Island

•2QO

390

q2C OOO

China

293,803 *

360,892,817 f

The coal area of the United States, given above, does
not include the lignitic coal-fields; but their product is
included in the second column. The areas of United
States coal-fields, known and estimated, are as follow :

* Exclusive of China and Western America, f Exclusive of China.

1 56 APPLIED GEOLOGY.

New England area 500 square miles.

Appalachian „ 58,731 „

Michigan „ 6,700 „

Illinois, etc. ,, 47,138 „

Missouri, etc. „ 78,430 ,,

Virginia and N. Carolina area 495 „ = 191,994 sq. miles.

Colorado „ 30,000? „

1 Wyoming „ 20,000? „

Montana „ 60,000? ,,

Dakota „ 100,000? „ = 2 10,000 sq. miles.

No guesses seem yet to have been hazarded as to the
extent of coal lands in Washington, Oregon, California,
Arizona, Utah, and New Mexico. It will probably be no
exaggeration to concede to the entire lignitic coal area an
extent of one hundred and seventy-five thousand square
miles.

Impurities in Coal. — Besides their fuel constituents,
carbon and hydrogen, all coals contain variable propor-
tions of other substances. Some of these, like nitrogen
and the mineral ingredients which constitute the ash, are
inert, acting merely to diminish by so much the fuel value
of the coal ; some, like moisture and oxygen, which in
combustion is removed as water, carry away a portion of
the heat evolved, as the latent heat of steam ; still others,
like sulphur and phosphorus, are directly injurious to the
fuel, both from evolving offensive gases in combustion,
and from acting injuriously upon iron.

Ash. — The ash in good coals may range from not
more than i per cent to 5 or 6 per cent, or somewhat more
in anthracite. The ash of one hundred and fifty-two
bituminous coals, examined in Ohio, averaged somewhat
less than 5 per cent, ranging from .77 per cent to 17 per
cent, ten of the samples yielding more than 10 per cent ;
while that of eighty-three bituminous coals, analyzed by
the present Geological Survey of Pennsylvania, gave an
average of 5.45 per cent, ranging from i-j- per cent to 19
per cent. It is probable that, in bituminous coals, ash

MINERAL FUELS. 157

not exceeding 5 per cent may be due almost wholly to
the mineral constituents of the original woody tissue, but
that much more than 5 per cent of ash would indicate the
probable presence of foreign earthy matter, either dissem-
inated, or occurring as thin laminae of shale.

Anthracite coals, from their greater loss of the original
constituents of woody tissue, in which loss the mineral
constituents could obviously take no part, will naturally
have a larger average of ash than the bituminous coals.
Analyses of twenty-seven anthracites and semi-anthra-
cites, recorded by the first Geological Survey of Penn-
sylvania, show an average of 6.13 per cent of ash ; analy-
ses of six, given in vol. Ma of the second survey, show
a 9 per cent average, ranging from 4^- to 14 per cent.
Probably about 7 per cent would be a fair average for
the ash in an anthracite free from foreign admixture.

Ash which contains any considerable proportion of iron,
lime, and alkalies, is apt to cause serious difficulty, where
high temperatures are required, from its tendency to fuse
and form clinkers, which clog the grates and adhere to
the fire-proof linings of stoves and furnaces. Coals which
yield a white ash are less likely to give trouble of this
kind, being nearly free from iron ; while red-ash coals
owe the color of their ash to a considerable amount of
iron, and are liable to clinker.

Water and Oxygen. — The amount of water in vari-
ous coals shows great variations, corresponding, doubtless,
to the porosity of their texture. The average amount of
water, shown by ninety-seven Pennsylvania bituminous
coals, is about i per cent ; by one hundred and twelve
Missouri coals, is 3.4 per cent ; by one hundred and fifty-
nine Ohio coals, is 4.65 per cent ; and by sixty-four Iowa
coals, is 8.57 per cent. In combustion, both this water and
the oxygen which is present to some extent in all coals
must be driven off in the form of steam, diminishing pro-
portionally the effective heat of the fuel.
8

158 APPLIED GEOLOGY.

Sulphur and Phosphorus. — These two directly in-
jurious substances are present in variable proportions in
almost every coal — phosphorus, the more deleterious of
the two, in much the smaller proportion. Both generate
offensive gases in combustion, and both act injuriously on
iron, one tenth of one per cent of phosphorus present in
iron causing it to be brittle when cold, or cold short ;
while the presence of sulphur in iron makes it brittle when
hot, red short, and any marked amount of it in coal cor-
rodes the iron-work of stoves, furnaces, and smoke-pipes,
causing serious inconvenience and expense. Phosphorus
is rarely present in the coals that have been examined
with reference to it in Ohio and Pennsylvania, to the ex-
tent of .001 of the coal ; usually its amount is much less
than this, and it is quite probable that the recently de-
vised basic process for eliminating it from iron will make
its presence in coal a matter of small moment to iron-
smelters ; although for domestic use, where its products
are liable to escape into inhabited rooms, even small
amounts of it are objectionable. The amount of sulphur
in coal rarely falls below a half of one per cent, an
amount which is not seriously injurious ; while it some-
times reaches as much as 6 or even 8 per cent, making
the coal worthless for most ordinary uses. Analyses of
eighty-two Pennsylvania bituminous coals show an aver-
age of 1.41 per cent of sulphur, ranging from .425 to 8.43
per cent ; and of fifty-six Ohio coals a range from . n to
6.19 per cent, giving an average of 1.9 per cent. The
sulphur in coal exists in at least two different states, a con-
siderable portion being combined with iron to form py-
rites, or with lime as gypsum, while the remainder is in
some obscure form of combination, as yet little under-
stood. A portion of the sulphur can be eliminated by
coking, but the proportion that can be so removed varies
greatly in different coals, adapting them to different uses,
as will be shown in a subsequent paragraph.

MINERAL FUELS.

159

Fuel Value of Coals. — Although some valuable ex-
perimental investigations of the heating power of a con-
siderable number of coals of different kinds, based on the
number of pounds of water evaporated from the boiling-
point by one pound each of the various coals, have been
made for the United States Government by Prof. W. R.
Johnson in 1842, and by General Meigs quite recently,
yet the lack of any general series of experimental tests
will make it convenient for the student to have at hand a
theoretical method of reaching a tolerable approximation
to the heating values of various fuels. Such a method is
based on finding the sum of the heating powers of the
two combustible constituents, carbon and hydrogen, of
any coal, shown by its ultimate analysis, and subtracting
from this sum the amount of heat wasted in driving off its
oxygen in the form of steam. Experiments have shown
that the complete combustion of one pound of carbon
will heat 8,080 pounds of water i° centigrade, and of one
pound of hydrogen will produce a like effect on 34,462
pounds of water. The oxygen in the coal, during com-
bustion, unites with one eighth its own weight of the hy-
drogen of the coal to form water, and the expulsion of
this water requires 537° C. of heat per pound. Hence
the formula for the theoretical heating power of any coal
will be C X 8,080 + (H - \ O) X 34,462 -40X537 =
heating power, in which C, H, and O stand for the re-
spective percentages of the carbon, hydrogen, and oxygen.

For example, coal 9 of the table on p. 141 contains in
one pound .7145 of a pound of carbon and .0547 of a
pound of hydrogen, of which .0201 will form with the
.1607 of oxygen .1808 of a pound of water, leaving
.0346 of hydrogen available as fuel. Hence .7145 X 8080
+ .0346 X 34,462 — .1808 X 537 = 6868.45° C. for the
theoretical heating power of this coal ; and, since 537° C.
of heat are required to convert one pound of water at the
boiling-point to steam, this would theoretically evaporate

160 APPLIED GEOLOGY.

12.79 pounds of water. Similar computations may be
made on any other coal of the table whose ultimate analy-
sis is given. For example, No. 12 has a heating power of
8171.15°, sufficient to convert 15.21 pounds of boiling
water to steam ; and woody tissue, No. 22, has a heating
power of 4077.3°, or an evaporative power of 7.56 pounds
of water. The theoretical heating power of fuels can,
however, by no means ever be attained in their practical
use. Indeed, the loss of heat by conduction, by imper-
fect combustion, and by excess of air in the draft, is so
great that it is rare that so much as two thirds of the abso-
lute heating power is realized in practice, with even the
best of appliances. The best results attained by Prof.
Johnson were from five semi-bituminous coals, which
evaporated each from n to 11.62 pounds of water per
pound of fuel, equaling within a trifle the theoretical heat-
ing power of the fixed carbon alone. The highest result
obtained by General Meigs was the evaporation of about
ten pounds of water with one pound of fuel. Prof. John-
son was inclined to think, from the results of six closely
agreeing tests, that the practical heating power of coals
is no greater than that which is due to their carbon, an
opinion in which Prof. H. D. Rogers concurs. Others
think that the heating power of the fixed carbon, given by
proximate analyses of coals, may afford a useful approxi-
mation : an examination, on this basis, of the table of
forty-four coals given by Prof. Johnson, shows certainly
some striking agreements, and some equally striking dis-
crepancies. On the basis of the heating power of the
fixed carbon only, the two coals, already used as exam-
ples, would have an evaporative power respectively of
8.66 and 10 pounds of water, or about two thirds of
their theoretical heating power. It seems probable that
two thirds of the theoretical result obtained by the formula
given above will prove to be as convenient an approxima-
tion as can be gained.

MINERAL FUELS. 161

Adaptation to Uses. — In selecting a coal for any of
the multifarious purposes which fuel subserves, due regard
being always had to relative cost and accessibility, it will
usually be found that the combination of qualities pos-
sessed by the several classes of coals gives them special
adaptations to certain uses for which they can be most
economically employed. For all uses, except perhaps the
coarsest, like the burning of lime and brick, it is essential
that a coal shall be as free as possible from sulphur and
phosphorus, as also from an undue amount of ash, espe-
cially of that kind which is liable to clinker at the temper-
ature that must be maintained. For most purposes, also,
it is highly desirable that coal should possess sufficient
strength to bear handling and transportation without un-
due breakage and consequent waste, the caking coals being
those in which breakage is of least consequence.

For domestic and kindred uses a coal should be non-
agglutinating, free from sooty smoke and light ash, and of
a high degree of heating power ; and it should be capable
of maintaining a steady combustion without too frequent
attention. This combination of qualities is found in a
high degree in the anthracites, and, for burning in close
stoves and furnaces, no coal could be better. With proper
appliances they are used also in open grates, the semi-an-
thracites being somewhat the better for this use, on account
of their freer combustion. Cannel and open-burning bi-
tuminous coals are also adapted to open fires, the cannels
being favorites for this use on account of their cheerful
flame, despite their usual abundance of ash, and their
somewhat low degree of heating power. These last-
named species of coal, also, do not produce the unpleasant
dryness in the atmosphere of rooms which is observable
where anthracite is used in open grates.

For the generation of steam a coal should combine,
with a high degree of evaporative power, the qualities of
easy kindling and a free combustion. There should be no

1 62 APPLIED GEOLOGY.

tendency to agglutinate, but rather to split up moderately
in burning, thus exposing a larger surface to the fire ; where
the coal is to be used on long voyages, it is highly essen-
tial also that it should be susceptible of compact stowage —
much steam-making power in little bulk — a property in
which coals differ as much as 15 or 20 per cent. The
semi-bituminous and free-burning anthracite coals are
well adapted for steam purposes, the former class, accord-
ing to the investigations of Prof. Johnson, excelling both
in evaporative power and in capability of compact stow-
age ; while Prof. H. D. Rogers inclines to give the prefer-
ence to the latter class. Hard anthracite, and especially
anthracite waste and slack, is also largely used for steam
purposes where it is favored by cheap transportation.

For the use of blacksmiths, where a hollow fire is de-
sirable, a pure agglutinating coal is employed ; and this
kind of coal is essential also for the manufacture of coke.
For the last purpose the coal should have a high percent-
age of fixed carbon ; and whatever sulphur it may contain
should be, as far as possible, in that condition which
renders it easy of elimination by heat. The operation of
coking drives off the water, the volatile combustible mat-
ter, and the separable sulphur, leaving the fixed carbon
and the ash as coke, which, in its best condition, is a
hard, strong, and highly cellular substance of a silvery
color.

Anthracite and open-burning bituminous coals are also
largely used for iron-smelting, it being essential for this
purpose that the coal should have sufficient strength
to bear the weight of the charge without crushing, and
that it should be free from injurious amounts of sulphur
and phosphorus. Where dry-burning bituminous coal is
used for smelting, it is freed from its volatile matter in the
upper part of the furnace, the gases being drawn off by
proper arrangements near the top of the stack, and used
for heating the blast and for other fuel purposes.

MINERAL FUELS. 163

For the manufacture of illuminating gas, a coal should
have a high percentage of volatile combustible constitu-
ents, and any sulphur which it may contain should be, as
far as possible, in that state in which it is not volatilized
during distillation. A residue of good coke is also highly
desirable. For this purpose, therefore, the fat, caking,
bituminous coals are selected, with which cannel coal is
sometimes mixed ; this latter kind of coal, although very
rich in volatile matter, yielding a residue of too inferior a
character to be used profitably alone.

Although what has here been said may serve as useful
suggestions to the student, in the selection of fuels best
adapted to certain purposes, where such a selection is pos-
sible within reasonable limits of cost, yet it must always
hold true that local supplies of mineral fuels, whatever
their quality, must be the chief dependence of communities,
because of their proximity to the consumer. Lignites,
often of very inferior quality, are coming into increasing
use in the western part of our continent ; and the statistics
of Germany and Austria show that more than 22,000,000
tons of this fuel are annually used in those countries for
domestic and other purposes. Although peat is widely dis-
tributed in marshy places over the Northern United States
and Canada, it has not yet been much used as fuel in
this country, because of its high percentage of water and
its objectionable odor, as well as because of the abundance
and cheapness of coal. It is, however, largely used in Ire-
land, Scotland, and some parts of Germany ; and it is said
that more than 40,000,000 tons of this fuel are burned
annually in Holland. It is prepared for use by cutting
and drying, or by compressing it into bricks of convenient
size. It has been suggested that its efficacy as fuel may
be increased, and its disagreeable odor removed, by char-
ring it like wood before burning. (Page.)

For the natural gas, which is coming into so large
use very recently as a fuel, the student is referred to the

1 64 APPLIED GEOLOGY.

succeeding chapter, where it is spoken of as the usual at-
tendant of petroleum, although frequently found without
this substance.

The student will do well to consult the geological manuals of Dana,
Geikie, and Credner, Dawson's "Acadian Geology," the geological
reports of the coal-producing States, and especially the second volume
of Rogers's report on Pennsylvania, the volume on mineral resources
of the United States, published by the Geological Survey in 1883, and
Johnson's report on American coals.

CHAPTER IX.

GEOLOGICAL MATERIALS FOR ILLUMINATION.

CHIEF of the geologically furnished light-producers, at
present, is petroleum, which, within the last quarter of a
century, has attained a foremost place in point of cheap-
ness and efficiency, to which must be added the bitumi-
nous shales and cannels, which yield illuminating oil by
distillation, and ozocerite, or mineral wax, besides illumi-
nating gas, which has already been mentioned as derived
from bituminous coals.

What is known under the general name of petroleum,
includes a series of hydrocarbon oils, varying widely in
physical properties. Some are limpid fluids and may be
burned for light without refining, while, with many inter-
mediate grades, others are found viscid and even tar-like,
having sufficient body to make excellent lubricators for
machinery. Their color, by transmitted light, ranges
from a light yellow, through orange and red, to a reddish
brown so dense as to be translucent only in thin films,
while, by reflected light, it passes from a light dusky to a
dark green and to a black. Their gravity ranges from
about 26° to 52° Beaume". They differ as markedly in
odor, also, as in other properties, some having a very dis-
agreeable smell, while that of others is considered even
pleasant.

Mode of Occurrence of Petroleum. — Petroleum
is found at many points, issuing in small quantities from

1 66 APPLIED GEOLOGY.

the earth in the form of springs; but, as a substance of
economic importance, it is almost invariably found stored
in deposits of porous rock, usually sandstones or con-
glomerates, which are incased above and below in prac-
tically impervious strata of shale or other clayey materials.
The porous rock plays the part, in truth, of a vast sponge
saturated in all its pores with petroleum and its usual
accompaniment, combustible gases. It is obvious, then,
that the storage capacity of such a bed will depend on its
extent, its thickness, and its porosity. An oil-bearing
sand-rock of considerable thickness, and of tolerably
uniform and loose texture, is likely to yield largely, and
to afford a good degree of certainty of success to the
operator, while one of little thickness, or whose texture
varies greatly in a vertical and horizontal direction, will
be not only uncertain to reach at favorable points, but
less likely to yield supplies of much durability. For ex-
ample, the unusually thick and uniform sand-rock of
Bradford, Pa., has given but a small percentage of unsuc-
cessful ventures over a considerable area, and is still pro-
ducing largely after a number of years of vigorous ex-
ploitation ; while the territory along Oil Creek and the
Alleghany River in western Pennsylvania, where the oil-
bearing rocks occur in long and narrow belts, and are
made up of irregular alternations of materials of highly
variable texture, and often of no great thickness of porous
rock, has afforded a large percentage of unproductive
wells, and, while often producing largely, has in many
localities been subject to early exhaustion. The imper-
vious incasement is also highly essential, to retain within
the sponge-like rock a substance so volatile as petroleum,
and to prevent its dissipation. Where the oil-bearing
rock is intersected by fissures which reach the surface, or
is tilted so as to outcrop, much of its valuable contents is
sure to have been lost. The idea, once somewhat preva-
lent, that the oil is stored in fissures, has been shown by

GEOLOGICAL LIGHT-PRODUCERS. 167

developments to have little foundation in fact ; and the
oil-producer looks for success rather to a properly con-
ditioned rock than to any fissures which may casually be
encountered in boring. Where fissures occur locally in
the rock they are helpful, not so much by increasing its
storage capacity as by promoting a ready flow of its con-
tents ; and, in all cases, the operator produces them arti-
ficially, by shattering the oil-rock with explosives, to in-
crease the extent of surface from which percolation may
take place. Where favorable conditions are met with, of
a porous storage-rock and an impervious incasement, the
petroleum and its accompanying gas are usually found, at
the outset, existing under enormous pressure, so that,
when a fresh territory is first pierced with the drill, the oil
frequently rises to the surface with great force, even from
the depth of many hundred feet, producing flowing wells.
A number of such wells in Pennsylvania have poured
forth at first from two thousand to more than three thou-
sand barrels of oil per day. As the pressure is relieved
by the flow and by the sinking of additional wells, the
rate of flow invariably diminishes, until ultimately the oil
no longer reaches the surface, and resort must then be
had to pumping. The question of the origin of. this in-
teresting substance is one which can by no means be con-
sidered to have been definitely settled as yet. It seems
probable, however, that it has originated from accumula-
tions of marine vegetation, and possibly, in some cases,
also from animal substances, which, subjected during vast
ages to a process of gradual change and distillation, have
evolved fluids and gases that have slowly permeated the
minute crevices of the overlying strata, until they have
found final lodgment in the porous strata where they now
occur.

The chief geological horizons from which petroleum is
procured in paying quantities, leaving out of view those
in which it has not yet proved of economic importance,

X68 APPLIED GEOLOGY.

are, first, the Corniferous, from which it is obtained in the
western part of the Province of Ontario near Lake St.
Clair ; second, several different geological levels in the
Upper Devonian of Pennsylvania and New York, of which
that of Bradford and its vicinity is lowest, succeeded by
that of the Warren and Forest County region, and this by
that of Oil Creek and the Alleghany River ; third, the Car-
boniferous, in which are found the usually heavy oils of
West Virginia and the adjacent part of Ohio, with two
other limited areas in northern and eastern Ohio ; and,
fourth, the Tertiary and possibly more recent deposits, in
which occurs the petroleum of California, that east of the
Carpathians in Galicia and Moldavia, that near Baku,
on the Caspian Sea, and that on the Irrawaddy River, in
Burmah, and on some of the coast islands of Burmah.

At the first of these horizons, near Lake St. Clair, some
petroleum has been obtained from surface-wells, sunk in
the drift materials overlying the limestones ; but the chief
supplies have been drawn from the Corniferous limestones
themselves, which here vary from a close to an open text-
ure, and are overlaid by about three hundred feet of
shales. The oil is black, of an unpleasant odor, and of
somewhat higher gravity than that of Pennsylvania, in
comparison with which last region its production has
always been small. Oil is also known to occur, near this
horizon, in southern Kentucky and adjacent parts of Ten-
nessee, but it has not yet been considerably produced in
this section.

The Upper Devonian rocks of the Chemung and possi-
bly of the Catskill period have, for many years, in west-
ern Pennsylvania and the adjacent part of New York,
furnished by far the greatest supplies of petroleum known
to exist, about five sixths of the world's supply being de-
rived from this region. The petroleum is here obtained
from a porous sand-rock, underlaid and covered by im-
pervious shales. The oil territory which was first discov-

GEOLOGICAL LIGHT-PRODUCERS. 169

ered and developed, occupying parts of several counties
in western Pennsylvania, along Oil Creek and the Alle-
ghany River, has given rise to the prevailing nomenclature
of the oil-producers. Petroleum is here found in a triple
group of white or gray, often loosely cemented, and porous
sandstones and conglomerates, called respectively the
first, second, and third sands, which are separated from
each other by considerable beds of shaly rocks. This oil-
bearing series has an average thickness of about three
hundred and fifty feet, and is overlaid by about four hun-
dred feet of soft, impervious shales. Still above these, in
many places, are found beds of sandstones or conglomer-
ates belonging to the Lower Carboniferous, and termed the
first and second mountain sands, because they usually cap
the highest hills. The oil-bearing sand-rocks are very
variable in thickness, composition, and texture, and are
sometimes split into benches by intercalations of shale,
thus locally giving rise to more than three sand-rocks,
while the series as a whole retains its usual thickness.
The portions which produce oil are usually of but little
width, often no great number of rods, though sometimes
extending, with occasional interruptions, for some miles
in the same general direction, bearing thus the character
of deposits along an ancient shore-line. These lines of
productiveness are the oil-belts. The lowermost, or third
sand, is, in much the greater number of cases, the storage-
rock ; and hence an oil-bearing rock is apt to be called
the third sand by operators, even in regions of quite dif-
ferent structure. Where the third sand is wanting, as, for
example, where the others overlap it, or where it is not
porous, the second or the first sands may produce oil, but
often of a different character from that usually found in
the third sand. The usual third sand oil has a gravity of
about 46° Beaume", and is of a dark-green color by re-
flected light, while some of those from the higher sands
are black, or have a reddish tint, or are of so high gravity

1 70 APPLIED GEOLOGY.

as to fit them for lubricators rather than for illumination.
The depth of the wells in this region varies from a few
hundred feet to 1,600 or 1,800 feet, the deepest wells
occurring in the southern part of the territory, toward
which the strata have a gentle dip.

The celebrated Bradford region, in McKean County,
Pennsylvania, with its continuation in New York, which
has for a number of years produced so vast an amount of
petroleum, has its storage-rock at a geological level fully a
thousand feet below that which has just been described,
and differs widely from it in general structure. The oil-
bearing sand-rock is of a fine texture, tolerably compact,
yet loosely cemented, and ranging in color from brown to
a light gray, forming a storage-rock of an average thick-
ness of perhaps forty-five feet, and varying so little in
texture that over a producing territory of about one hun-
dred and ten square miles not more than four per cent of
the wells have proved unproductive. Above this stratum,
which is called the third sand, lies a very thick mass of
shaly rock with occasional sandy strata, among which the
well-drillers number a first and second sand, following the
traditions of the region first explored, to which this bears
no structural resemblance. The average depth of the wells
in this district ranges from 1,200 to about 2,000 feet, the
deepest wells being found in its southwestern part. The
cost of drilling and equipping a well 1,500 feet deep, in
1880, was estimated to be about $3,250.

The oil-producing horizon in Warren and Forest
Counties, intermediate between that of Bradford and that
of Oil Creek, has yielded productive wells in porous rocks,
varying tgreatly in character and at different levels, the
physical characters of the product being as variable as
those of the conditions under which it occurs. Some of
these oils are transparent, and of various reddish or amber
tints, with .a gravity of about 47° or 48°, while others are
greenish and nearly opaque, with a gravity of 40°. A

GEOLOGICAL LIGHT-PRODUCERS. 171

number of remarkable wells have been found in this
region, several of which have started out with the aston-
ishing daily production of from 2,000 to 3,000 barrels ;
but their activity has invariably been very short-lived, and
as a class the wells of this district have shown little dura-
bility.

The oil district of West Virginia, extending into Wash-
ington County, Ohio, obtains its supplies from sandstones
of Carboniferous age. The oil is said to occur in fissures
on the site of gentle anticlinal axes. Its actual mode of
occurrence probably does not differ materially from that
which has been found to hold true on so extensive a scale
in Pennsylvania. The oil is of greater gravity than that
of Pennsylvania, ranging from 28° to 40° B., and the
production has not been large, amounting in 1880 to
about 220,000 barrels of 42 gallons, or about 600 barrels
daily. The oil-producing territory of California occurs
in two of its southwestern counties near the coast. In
this region, large natural springs of petroleum with exten-
sive sheets of asphaltum arising from its evaporation,
have for many years been known to exist ; the oil issuing
from the outcropping edges of highly inclined bituminous
strata of probable Tertiary age. The amount of oil ob-
tained from borings in these strata has not hitherto met
the sanguine expectations of the earlier explorers, appar-
ently so well justified by the surface exudations. The
estimated production of 1882 was about 70,000 barrels, or
less than 200 barrels per day ; though for a portion of
that year a daily production of 500 barrels was claimed.
From what are now known to be the usual conditions on
which large supplies of petroleum seemingly depend, a
great production can hardly be looked for from this dis-
trict.

Of all the regions at present producing petroleum from
the Tertiary or later deposits, that of Baku, on the Cas-
pian Sea, is by far the most promising. Here, for many

1/2 APPLIED GEOLOGY.

ages, a tract twenty-five miles long and a half-mile in width
has yielded petroleum (naphtha) from a porous argilla-
ceous sandstone of Tertiary age, the wells being usually not
more than twenty-five feet deep. Recent careful explora-
tions show, it is said, that the possible productive area
may amount to as much as 1,260 square miles ; and the
active development now in progress resulted in a produc-
tion, in 1882, of nearly 5,000,000 barrels, and in 1884 of
about 6,700,000 barrels; from which it seems likely that
this is destined to be a formidable competitor to the oil-
regions of Pennsylvania. The petroleum of Baku is said
to vary from a clear naphtha-like fluid to one of a yellow-
ish-green and reddish-brown, with a gravity of from 26° to
36° B. It yields only about 33 per cent of illuminating oil,
the residuum being burned for fuel.

The long-known petroleum of Burmah is obtained
chiefly from wells of no considerable depth, in a soft
greenish sandstone of late geological age, inclosed in im-
pervious beds of sandy clay, near the Irrawaddy River.
The productive territory is said to be less than a square
mile in area, and the amount produced annually does not
reach 1,000,000 barrels. Petroleum is also found in
small quantities in springs on several islands off the west
coast of Burmah. The Burmese product is of two kinds :
one, which seems to resemble our u amber oil," is of light
gravity and reddish color, and yields a high per cent of
illuminating oil with little parafnne ; the other is thick, of
a greenish color and agreeable smell, and holds a large per
cent of paraffine. The petroleum which is reported to ex-
ist in considerable quantities in deposits of Tertiary age
north of the Carpathians does not seem as yet to have
made any figure in the markets of the world. Of that
which is said to have been long produced in China, little
is known wkh certainty. Small quantities are also ob-
tained in Japan, according to Prof. Lyman, from wells
dug to no considerable depth.

The amount of petroleum produced in
and adjacent parts of New York, in 1882, was reported to
be 30,053,500 barrels of forty-two gallons ; and in June,
1883, the daily production was nearly 66,000 barrels, or at
the rate of about 24,000,000 barrels yearly, a rate which
was continued in 1884. It may thus be seen that the
production of Pennsylvania is by far the greatest factor in
the world's supply of this very useful commodity, that of
the Caspian region ranking second.

How Oil-Weils are bored and operated. — In
few branches of business have there been more remark-
able improvements made, both in simplicity and effective-
ness of work and in diminution of expense, than those
which have been suggested by experience in drilling and
operating oil-wells. This might naturally be expected,
when we consider the great number of active and highly
intelligent men who are engaged in a business involving
more than usual risks, and in which the tendency to a
constant diminution in the price of the product demands
a corresponding diminution in the cost of production.
Then, too, the number of these usually very deep borings
has been enormous, being counted by the tens of thou-
sands. The number of oil-wells producing simultaneously
in the Pennsylvania region has sometimes been more than
nineteen thousand ; and the number of new wells in prog-
ress has not for many years fallen so low as a hundred,
and has, not unfrequently, been more than four hundred.
Hence, undertakings which thirty years ago would have
been considered remarkable, have come to be matters of
ordinary every-day business, and the means by which they
could most easily be accomplished have demanded the
attention of many clear-sighted men. At the outset, bor-
ings at first four inches and later five and a half inches in
diameter were sunk to the oil-producing rock, no effort
being made to shut off the water which entered the boring
from porous rocks encountered in the strata that were

174

APPLIED GEOLOGY.

penetrated. Hence the well, however deep, was always
nearly full of water while the boring was in progress, caus-
ing serious inconveniences, not only by lessening the force
of the drilling-tools, and by converting into fluid mud
some of the softer shales to embarrass the drillers, but
also by making it uncertain when an oil-bearing rock had
really been reached, until the water-veins had been shut
off and the well cleared of water by pumping. These and
other difficulties eventually led to the adoption of the pres-
ent form of boring, which seems admirably adapted to its
purpose.

Where the loose surface materials are of considerable
depth, a wrought-iron drive-pipe, of eight inches interior
diameter, is forced down vertically to the bed-rock, in suc-
cessive lengths of nine feet each ; and an eight- inch hole
is drilled through this pipe till it reaches the bottom of the
lowest water-bearing stratum, when it is tapered gradually
down to five and a half inches. Into this hole, an iron pipe
of five and a half inches inside diameter, called the casing,
screwed together in lengths, and surrounded at the bottom
by a properly constructed collar, is lowered and firmly seat-
ed on the tapering shoulder prepared for it, thus shutting
off all water from above. From this point downward the
drilling, five and a half inches in diameter, is prosecuted
dry, water being poured in from the top through the casing
to moisten the powder produced by the drill, so that it may
be removed as mud by an instrument called a sand-pump,
which consists usually of a cylinder six to ten feet long of
thin iron, provided at the bottom with a spindle-valve
opening upward, and at the top with a bail by which it is
attached to a stout rope of proper length. The usual
drilling-tools are sixty-two feet long and weigh twenty-
one hundred pounds. They consist of several parts
screwed firmly together, and called, commencing from be-
low, the bi^ the auger-stem, the jars, the sinker-bar, and the
rope-socket. The first named is the steel-edged chisel which

GEOLOGICAL LIGHT-PRODUCERS. 175

cuts the rock, and is screwed above to the auger-stem, a
bar of iron thirty feet in length. The jars, a highly im-
portant device, are two elongated steel-faced links with a
play of thirteen inches, the lower link of which is screwed
to the auger-stem, and aids in giving the downward or cut-
ting blow, while the upper link attached to the sinker-bar
aids the two upper members to give a sharp upward stroke
to the tools on their ascent, by which the bit is loosened
from the rock. The rope-socket is the upper member of
the series, and is securely attached to the great rope-cable
by which the string of tools is to be raised and lowered,
and given motion in drilling. For the purpose of raising
and lowering the drilling-tools, and of operating the well
after it is completed, a stout, pyramidal framework about
seventy-five feet in height, called a derrick, is erected over
the site of the proposed well. At one side of this is set
the steam-engine that furnishes the power, with the band-
wheel and walking-beam by which the drilling-tools and
other parts of the machinery are driven. At the top of
the derrick is a stout pulley over which the drill-cable
passes, and a little below a second pulley for the sand-
pump rope. The end of the drill-cable opposite to that
to which the tools are attached is coiled around a large
cylindrical drum, called a bull-wheel, to which motion is
given by the engine in raising the tools from the well :
they will naturally descend by their own weight when per-
mitted, the rate of their descent being controlled by a
powerful brake applied to the bull-wheel. When the tools
are lowered ready for drilling, they are connected with the
end of the walking-beam by an arrangement called a tem-
per-screw, the lower end of which is firmly clamped to the
cable at the proper point. By this means, as the bit cuts
deeper into the rock, the tools can be gradually lowered
until the screw, about four feet long, is run out, when the
tools must be raised and the well cleaned out with the
sand-pump. When the oil-sand is reached, specimens of

176 APPLIED GEOLOGY.

the drillings are taken for every run, and carefully pre-
served to serve as a guide in operating the well. In order
to secure a perfectly cylindrical hole, the tools are rotated
when in action, by means of a lever inserted in rings of
the temper-screw.

A full description of the mode of drilling oil-wells, with
working drawings, may be found by the student in Vol.
I8 of the " Second Geological Survey of Pennsylvania." It
seemed fitting, however, to include, in a work of this char-
acter, this brief account of an operation so interesting
even aside from oil-production, the improvements in which
have reduced the cost of deep borings to about one fourth
of what they were less than twenty years ago, while di-
minishing the time consumed in fully as great a ratio.

In the present mode of drilling a well dry, it can be
ascertained, soon after the oil-rock has been penetrated,
whether the well is likely to be successful. In case the
show of oil and gas is satisfactory, the drilling-tools are
removed, and the well is tubed with iron tubing of two
inches diameter inside, screwed together in lengths until
the bottom of the well is reached. The lower end of the
tubing is provided with an anchor, made of a piece of per-
forated casing a few feet in length, to the top of which
the working barrel is attached. The pump-rods, with a
suitable valve at bottom, are next inserted into the tubing,
being screwed together in lengths ; the upper end of the
pump-rod is attached to the walking-beam, and the opera-
tion of pumping oil begins. The oil passes to a tank by a
side-pipe near the top of the tubing, while the gas, which
is usually present, rises in the annular space between the
tubing and casing, and is carried by another side-pipe to
be burned as fuel under the boiler. In many cases, espe-
cially in the Bradford district, the oil is of such quality
that the operation of pumping can be dispensed with, and
the well compelled to flow by heads. This is effected by
encircling the tubing, at a proper point above the oil-rock,,

GEOLOGICAL LIGHT-PRODUCERS. 177

with an annular valve called a. packer, by which the space
between the tubing and the walls of the well is closed
gas-tight. The accumulating force of the oil and gas thus
imprisoned below will then cause the well to flow periodi-
cally, or by heads.

Almost universally, before the well is tubed, the oil-
producing rock is shattered by means of torpedoes charged
with nitro-glycerine to facilitate the influx of oil. These
torpedoes are simply tin shells, sometimes twenty to thirty
feet long, and containing not unfrequently from thirty
to sixty quarts of nitro-glycerine. These are lowered to
their place by means of a wire, which is then unhooked
and withdrawn, and the torpedo exploded by dropping a
weight from above upon a detonating cap in its top. "The
commotion caused by so large an amount of this violent
explosive can be more easily imagined than described.
This operation is also frequently resorted to when the
production of a well becomes greatly diminished, the tub-
ing being withdrawn before the torpedo is used.

Refining. — The method of refining crude petroleum,
to fit it for being burned in lamps, is based on the fact
that the various ingredients of this highly complex sub-
stance have different boiling-points. Hence, by a process
of fractional distillation at regulated temperatures, the
more volatile ingredients, such as gasolene, naphtha, and
benzine, which would render the oil dangerous to be
burned in lamps, are first driven off, succeeded next by
illuminating oil, and leaving behind in the still a tarry
residue which may be further separated by distillation,
leaving a final residue of coke. The illuminating oil is
then further purified by agitation with sulphuric acid, by
which a tarry substance is separated from it, and finally
by agitation with water and an alkali to remove all traces
of the acid. The average results obtained at a refinery in
Titusville, Pa., treating petroleum of about 46° Beaume,
were given as the following :

178 APPLIED GEOLOGY.

Naphtha, etc '. 10 per cent.

Illuminating oil 75 „

Tarry residue 7 „

Gas and loss 8 „

Total 100 „

In a different mode of refining, a smaller proportion of
illuminating oil is made, and the heavier products are
separated as lubricators for machinery.

Uses. — Besides the well-known extensive use of petro-
leum for lighting purposes, the crude heavy oils are very
valuable as lubricators for machinery. Several of its by-
products are also largely used ; as, for example, paraffine,
which, besides entering into the manufacture of candles,
has several other valuable applications ; the so-called
naphtha, which is used for mixing paints and varnishes,
and as a solvent for resins and grease ; while gasolene is
employed as a carburetting agent in automatic gas-ma-
chines. Both crude petroleum and the residue from re-
fining are also largely used as fuel in Russia.

For additional information with respect to petroleum, the student
will do well to consult the " Second Geological Survey Reports of
Pennsylvania," Vols. I, I3, I4, J, and R ; the section on petroleum in
" Mineral Resources of the United States," published by the United
States Geological Survey in 1883 ; " Tenth Census of the United
States," Vol. X ; and the article " Petroleum " in Appletons' " Amer-
ican Cyclopaedia." Valuable information may also be obtained from
" Geology of Canada," 1863, and Vols. I, II, III of Ohio " Geological
Reports," as well as from papers of Drs. Newberry and T. S. Hunt,
on this and allied subjects.

To illustrate what has been said of the mode of occur-
rence of petroleum, the present mode of drilling and
operating oil-wells, and the tools that are used in drilling,
the following figures are appended.

Other Mineral Light-Producers. — Before the dis-
covery and development of the great sources of natural
rock oils, illuminating oils were produced to a consider-

OIL

3'6" [f] Rope-socket.

Sinker-bar.

CASINt
HEAD

Drift with 8" drive

Shale.!

PIPE

First mountain sand,.
water-bearing.

30' Auier-stem-

Shale.!

Second mountain^
sand, lowest wa-~
ter-bearing. Cased;
here, 5$" casing. =

Shale.!

ILL-H(.

Bit.

Oil series. First:
sand.

Shale.^

Second sand.]

Shale.]

Third sand.}

Bottom shale j

FIG. 14.— Drilling-tools. To-
tal length, 61' i* ; weight,
2,100 Ibs. ; down stroke,
1,320 Ibs. ; upward stroke,
780 Ibs.

FIG 15.— Ideal Section of Oil- Well, Oil
Creek, Pa.

180 APPLIED GEOLOGY.

able extent by the distillation, at a dull-red heat, of cannel
and fat bituminous coals, and also by the distillation of
black bituminous shales called oil-shales or pyroschists.
The use of oil obtained from these substances has been
wholly superseded in this country by the abundant and
cheap mineral oil ; but the manufacture of oils from these
sources continues to be a considerable one in some parts
of Europe, both cannels and oil-shales being used for this
purpose. Of the latter, more than a million tons were
raised for distillation in Great Britain in the year 1882.*
Should the production of petroleum seriously diminish in
this country, as it seems quite likely to do at an early day,
unless sources of supply now unknown are discovered, re-
course must be had, at no distant time, to our cannels,
like the Breckenridge of Kentucky, and to our bituminous
shales, now useless, which are found abundantly at many
geological horizons. The bituminous shales at the base
of strata of the Hudson period in the Lower Silurian,
called the Utica slates, extend widely over the north-
ern part of New York and Canada, containing important
amounts of carbonaceous matter, amounting sometimes to
as much as 20 per cent, and are thought by Dr. Newberry
to be the ultimate source of the oils of western Canada.
At the base and summit of rocks of the Hamilton period,
in central New York, are found the Marcellus and Gene-
see black shales, which are often marked along their out-
crops by springs of oil and gas, and the latter of which,
in its western extension, becomes the Huron shale of
central Ohio, being there about three hundred and fifty
feet thick, and stretching southward into Tennessee. It
is estimated by Dr. Newberry to be capable of yielding
by distillation from ten to twenty gallons of oil per ton.
From the horizon of the Genesee and Huron shales,
abundant gas-wells have also been obtained along the
shores of Lake Erie, from Fredonia, in New York, to near
* This amount was increased to 1,518,871 tons in 1884.

GEOLOGICAL LIGHT-PRODUCERS. 181

Cleveland, and also in Knox County, Ohio. The gas is
utilized for heat and light, and, in Knox County, for mak-
ing what is called " carbon-black," a substance nearly
equal in value to ivory-black. Bituminous shales are
found abundantly in the Carboniferous, as might be ex-
pected, since the source of the bituminous matter is doubt-
less largely vegetable; in the Triassic of Virginia and
North Carolina, some of the strata of which are so highly
bituminous as to be classed by O. J. Heinrich as the
Oleiferous group ; in the Cretaceous of Colorado and ad-
joining regions ; and in the Tertiary rocks of western Cal-
ifornia, especially in Venturas and Santa Barbara Counties,
from whose interbedded sandstones is derived the oil men-
tioned on a previous page. Most pyroschists contain also
a considerable amount of nitrogen, which, by proper mani-
pulation during distillation, can be obtained as ammonia.

In some of the earlier reports of the Geological Sur-
vey of Canada, Dr. T. Sterry Hunt has drawn attention
also to our abundant beds of peat as a possible future
source of oil, paraffine, gas, and other products, by distilla-
tion.

In 1877 an important deposit of ozocerite, or mineral
wax, was discovered in southern Utah, this substance hav-
ing previously been known chiefly from Moldavia, east of
the Carpathians. It is of a wax-like appearance, and
ranges in color from whitish to black. It is said to yield
by fractional distillation from 8 to 10 per cent of illumi-
nating oil, and 60 per cent of paraffine. Such are the
chief light-producers of mineral origin. To recapitulate
briefly, they are :

1. Gas and oil, obtained by the distillation of bitumi-
nous and cannel coals, bituminous shales, peat, and, to a
small extent, from ozocerite.

2. Petroleum, occurring at present in porous or some-
times fissured storage-rocks, but having its probable deep-
seated source in bituminous shales.

1 82 APPLIED GEOLOGY.

3. Natural gas, derived from oil-bearing rocks, and
from wells sunk in bituminous shales.

4. Paraffine, obtained from ozocerite, and as a by-
product in the refining of various bituminous sub-
stances.

CHAPTER X.

MODE OF OCCURRENCE OF METALLIFEROUS DEPOSITS.

ON account of the very great importance of many of
the metals in the arts and industries of civilized man, as
well as of the difficulties and uncertainty that attend their
discovery and exploitation, much attention has naturally
been directed to the various combinations in which they
occur, to the minerals with which they are found associ-
ated, and to the geological nature, structure, and origin of
the deposits in which they are found.

As is pretty generally known, very few of the metals
occur in nature in the metallic or uncombined state. In
the vast majority of cases, they are found in chemical
combination with some other element or elements, form-
ing that class of mineral substances known as ores. These
ores usually differ widely in appearance and properties
from the metals which give them their value, and require
to be subjected to some chemical process before the metal
which they contain can be separated and utilized. Nor
are the ores themselves usually found simple and unmixed.
Almost universally they occur associated and intermingled
with other mineral substances, which frequently make up
the chief bulk of the metalliferous deposit, and from
which they must be separated by processes sometimes
mechanical, sometimes chemical. These associated min-
erals are known by the name of gangues or vein-stones.
Again, although several of the metallic ores occur widely

1 84 APPLIED GEOLOGY.

diffused in minute quantities in many rocks — as, for ex-
ample, iron, traces of which may be found in nearly all
rocks — still, to be of any economic importance, they must
by some means have been concentrated in certain places
into deposits of such richness as to admit of their profit-
able extraction. Such concentrations are called ore de-
posits, and to these various names are given, according to
their structure and the geological conditions under which
they occur.

Metallic Ores. — Of the metals possessing economic
importance, gold and platinum are almost always found in
the metallic state ; bismuth also most largely so ; and cop-
per, which usually occurs in the state of ores, in one fa-
mous region is found in vast quantities as a native metal.
Besides these, silver and mercury occasionally occur in
the metallic state. Much the most widely diffused miner-
alizing agents of ores are sulphur, oxygen, and carbonic acid,
to which are added in much smaller measure silica, arsenic,
and chlorine. Most of the leading metals have compounds
with sulphur, and in the case of several of the metals
these sulphides form their chief ores. Pyrites, the iron
sulphide, common as it is, and great as is its economic
importance, can hardly be called a source of iron ; but the
sulphides of silver, both alone and combined or associ-
ated with sulphides of lead, antimony, and arsenic, con-
stitute a chief source of silver. So the sulphide of mer-
cury (cinnabar), stibnite (the sulphide of antimony), and
galena (the lead sulphide), are the main sources of these
three metals ; while blende (the zinc sulphide) and the
various sulphides of copper, or of copper combined with
iron, are leading ores of their respective metals. Millerite,
a nickel sulphide, is also a valuable ore ; and bismuthinite,
the sulphide of bismuth, is said to be the source whence
the United States are likely to derive their future supplies
of this metal.

Among the oxide ores, those of iron have a foremost

METALLIFEROUS DEPOSITS. 185

place, being, though not the sole, yet a leading source
whence are derived the supplies of this most important
metal. Tin is obtained almost wholly from its oxide, cas-
siterite. The most valuable ores of manganese are its
oxides ; and the brilliant compounds of chromium are
wholly derived from chromite, an oxygen compound of
chromium and iron. Zincite, the red oxide of zinc, found
in New Jersey, is a valuable ore. Oxides_of copper and
of cobalt also occur, and are used wherever found as
sources, the one of copper, and the other of smalt.

The important carbonate ores are those of iron, cop-
per, lead, and zinc. The iron carbonate, called siderite,
or spathic iron, whether pure or mingled with varying
amounts of earthy or bituminous matters, as clay iron-
stone and black-band ore, are highly important ores of iron
and largely utilized. Malachite (the copper carbonate),
the lead carbonate (cerusite), and smithsonite (the carbon-
ate of zinc), occur usually associated with other ores of
their respective metals, notably the sulphides, have evi-
dently been derived from them, and are valuable ores.

The silicate ores are those of zinc called calamine, of
copper called chrysocolla, and several of nickel, all of
which are employed as sources of their metals. Rho-
donite, a manganese silicate, is also utilized somewhat in
coloring glass and porcelain.

The only chloride ore of any importance is cerargyrite
or horn-silver, which is a considerable source of silver.
Arsenic forms several ores with nickel and cobalt which
are important as sources of nickel and of the compounds
of cobalt.

Besides these, ores, notably those of gold and silver,
are sparingly met with in which tellurium is the mineral-
izing agent. These tellurides, variously combined, consti-
tuting the minerals sylvanite, hessite, petzite, nagyagite,
and calaverite, are valuable ores of the precious metals in
the few localities where they occur.

!86 APPLIED GEOLOGY.

Ore Associations and Gangues. — Besides the com-
paratively simple ores that have been mentioned above,
others of a much more complex character are frequently
met with, formed by the union of two or more metals with
the same mineralizing agent, or by the partial replacement
of one element by another. Thus the most common ore
of copper, chalcopyrite, is a double sulphide of iron and
copper. Common ores of silver are sulphides of silver
and antimony, or of silver and arsenic ; and in the first,
portions of the silver and antimony may be replaced by
copper and arsenic. Cobalt and nickel also have arsen-
ides and sulphides in which one metal may partially re-
place the other, forming double compounds ; or antimony
may partly replace arsenic in the nickel arsenides, giving
rise to another form of complication. So in the mineral
tetrahedrite, often called gray copper, which is a sulphide of
copper and antimony, the copper may be partially replaced
by iron and zinc, or by silver, forming a valuable ore of
silver ; while arsenic may take the place of a part of the
antimony, giving rise to a highly complicated ore. Be-
sides the complications of composition of which these few
examples have been given, others arise from frequent
associations of ores. Thus ores of silver are so frequently
associated with those of lead that argentiferous lead-ores
are a large source of silver, as in some of our great West-
ern mining regions. Silver sulphide is found also with
zinc sulphide, forming another often rich but somewhat
troublesome ore, as in some of the mines about George-
town, Colorado. So, too, the ores of lead and zinc are
very often closely associated ; iron pyrites is intermingled
usually with more or less of copper pyrites, and vice versa ;
and manganese-ores occur with those of iron. Tin-ore is
almost always associated with a mineral called wolfram ;
platinum, always native, is invariably alloyed with one or
more of the rare metals iridium, palladium, rhodium,
and osmium ; and gold, likewise native, though alloyed

METALLIFEROUS DEPOSITS. 187

with silver, is commonly associated with iron or copper
pyrites, making its extraction difficult save where its asso-
ciates have been removed by weathering. Only a few
of the more common associations and combinations have
here been mentioned by way of illustration. The student
who desires to go more fully into this subject will find
many more in special treatises on ore deposits like those
of Grimm, Von Cotta, and J. A. Phillips.

Ores of metals thus composed and associated are in
most cases arranged and disseminated in a considerable
bulk of other minerals having no value as ores, and which
are called gangues, or vein-stones. The most common of the
gangues are quartz, calcite, baryte, often called heavy-spar,
and fluor-spar. Sometimes the ore has little gangue, as
is the case with some deposits of iron-ore ; more common-
ly the gangue greatly surpasses- the ore in amount. This
is especially true in the case of ores of the precious metals,
as can be readily understood when we reflect that an ore
containing three hundred dollars' worth of silver per ton,
which would be considered very rich, would have no
more than one per cent of the metal, and that a gold -ore
of the same value would contain only about one twentieth
of one per cent, or about a pound in a ton. We call such
deposits gold or silver deposits, because they contain
enough of these metals or their ores to be worked with
profit ; when they might more justly be considered depos-
its of the gangue minerals slightly contaminated with gold
or with silver ores. Proportions of these ores such as
have been named, when viewed in the light of human en-
terprise, would be counted very rich and enormously
profitable ; but considered with reference to the relation
that they bear to the mass of the rock, they are evidently
but very minor accessories. The ratio which the ores of
the base metals bear to their gangues must naturally be
much greater than this, to bring them within the limits of
profitable working ; yet with these the question of profit

1 88 APPLIED GEOLOGY.

is often dependent on some cheap and effective means of
separating a large amount of worthless rock from a com-
paratively small amount of valuable material. For exam-
ple, in the great Lake Superior copper-mines the native
copper is mingled with from 85 to 99 per cent of worth-
less vein-stone, which, however, can be mostly separated
by pulverizing the rock and washing it in suitable appa-
ratus. Such a process of separation of ore from gangue
is called concentration, and many very ingenious devices
have been contrived for this purpose, descriptions of which
may be found in technical works. They mostly depend
upon the use of currents of water, but sometimes of air,
whose velocity is so regulated as to sweep away the lighter
materials, leaving the heavier behind. The greater the
difference in weight of particles made nearly equal in size,
the easier and more complete the separation can be made.
Geological Mode of Occurrence and Structure
of Ore Deposits. — Ore deposits are unquestionably due
to some process of concentration of substances, once wide-
ly and sparsely disseminated, or too deep-seated to be
available for human use. In some cases the concentra-
tion has been due to mechanical agencies, by which rocks
have been ground up, and their heavier and more un-
changeable portions collected in favorable places ; in
some others it has been effected possibly by the agency
of heat, which may have volatilized certain substances
and forced them up from considerable depths in the form
of vapor, to 'be condensed on cooling; but in the vast
majority of cases the accumulation of ore deposits has
been due to chemical solution, in which water has played
a prominent and essential part. By this last means, par-
ticles widely diffused have been removed by solution from
their parent rock, and have been carried away to be rede-
posited in fissures and cavities, or to fill the pores and
cellules in rocks ; or to react chemically with favorable
portions of some rocks, chiefly limestones, and thus to re-

METALLIFEROUS DEPOSITS. 189

place them ; or, through change or dissipation of their
solvent, to be deposited in beds at the existing surface,
either alone or mingled with other substances. The most
important forms in which metalliferous deposits, thus
originating, are found to occur, though variously grouped
by different authors, may be conveniently tabulated as
follows :

a. Placers and other superficial deposits.

b. Deposits forming entire strata.

c. Deposits disseminated in strata.

d. Ores segregated from strata.

e. Infiltrations into beds.

2. Impregnations -j f. Contact zones enriched from neighboring

deposits.
g. Gash-veins and caverns in limestone.

h. Quasi-veins or chambers.

3. Mass deposits J .

1 t. Contact deposits.

j. Stockworks.
f k. Segregated veins.

4. Veins I f (r) Bedded veins.

1 /. Fissure-veins -| (2) Cross-cutting veins.
I I (3) Contact veins.

I. Stratified Deposits. — Many valuable metallifer-
ous deposits are found occurring in the form of beds,
evidently deposited in most instances as sediments, but in
at least one case, that will be mentioned, in sheets of vol-
canic rock interbedded with mechanical sediments. The
bedded form of deposits is especially common with the
ores of iron, though it is by no means confined to them.
Usually the origin of the ores has been contemporaneous
with that of the accompanying and inclosing rocks ; where,
however, it seems evident that it has been subsequent to
that of the beds in which they are contained, they would
properly be classed as impregnations. Bedded deposits
have pretty definite limits above and below ; their arrange-
ment is parallel with that of other beds of the same series,
whether the position of the series is horizontal or inclined;
they have no special connection with other similar parallel

APPLIED GEOLOGY.

beds ; and their valuable contents are in general more
evenly distributed than is the case with other forms of ore
deposits.

(a) Placers. — This important form of metalliferous
deposits may, it would seem, be classed with beds, owing
their origin as they do to the same kind of agencies by
which mechanical sediments are formed, and when they
come to be covered, as they sometimes are, by deposits
of other materials, being considered and treated as beds.
Placers originate from the disaggregation of other forms of
ore deposits, and from the sorting of their materials by the
action of running water. The substances which give them
their value are of much greater specific gravity than the
minerals with which they were originally associated, and
are not affected by the usual agencies of change. Hence
they retain their integrity, and are separated by the action
of water from the lighter substances and from those
which yield to disintegrating influences. Sometimes the
valuable minerals remain nearly in their original position,
and are merely separated in a greater or less degree from
their accompanying rock. In much the more numerous
and important cases, all the material of the disaggregated
deposit is transported to some distance from its place of
origin ; the desirable substance, by reason of its greater
gravity, is washed free from the lighter and finer rock, and
is ultimately accumulated in the lower portions of a rude
mass of the coarser rubbish, mingled usually with sand
and in some places with " occasional beds of tenacious
clay." The usual places of accumulation of placers are
naturally at the base of declivities, in valleys, and in wa-
ter-courses ; and in the last case, the ancient water-course,
now entirely filled with transported material, may long
since have been abandoned by the stream to which its
origin was due. These accumulations have in not a few
cases been cemented to a solid mass, especially in their
lower portions, by the infiltration of mineral waters, and

METALLIFEROUS DEPOSITS. 191

some of the placers of the Pacific coast and of Australia
have subsequently been covered by sheets of lava of great
thickness. Placer deposits are sometimes hundreds of
feet in thickness, and have a rudely stratified structure,
marking undoubtedly periods of rapid and tumultuary dep-
osition, alternating with others of more quiet action. The
distribution of the valuable substance in such masses is
by no means uniform. Being of high specific gravity, as
has before been remarked, it naturally tends to the lowest
point in the deposit, and is found most abundant on and
near the bed-rock, the richest accumulations being found in
holes, splits, and depressions of this rock, and at points
where the current of the depositing stream had been ar-
rested or suddenly changed by any cause. When several
periods of deposition are superposed, several richer hori-
zons or pay-streaks may occur, occupying each the lowest
place in its own bed. The substances commonly found
in placers are, besides precious stones, gold, platinum, tin
oxide, and magnetite, all of them highly insensible to the
usual agencies of change.

Although Von Cotta, in his excellent treatise on ore de-
posits, expresses a doubt whether placer deposits occur of
earlier date than the Post-Tertiary, yet Dawson, in his " Aca-
dian Geology," shows that gold-bearing placers are found
in Nova Scotia at the base of the Lower Carboniferous as
conglomerates deriving their materials from Silurian au-
riferous rocks ; and in the vicinity of Deadwood, in the
Black Hills, auriferous conglomerates of probable Primor-
dial age occur, having all the characteristics of modern
placers, both in the nature of the materials constituting
the deposits, and in the distribution of the gold. (" En-
gineering and Mining Journal," 1882, p. 335.)

Besides placers, deposits of metallic ores of bedded
structure occur, (b) forming the entire mass, or at least the
greatly preponderating material of beds of considerable
extent and thickness ; such is the case with many very im-

192 APPLIED GEOLOGY.

portant deposits of iron-ore. Or (c) the metallic substance
may be found disseminated more or less richly throughout
certain beds ; examples of which may be seen in the copper-
bearing conglomerates of Lake Superior, and in the bitumi-
nous shale of Mansfeld, containing profitable amounts of
ores of copper and silver. Lastly, ores may occur (d) as
concretionary masses of variable size, in beds from whose
remaining materials they have segregated themselves by
virtue of the mutual attraction exerted by particles of a
like kind ; e. g., the kidney-shaped masses of clay iron-
stone occurring abundantly in some strata of the coal-
measures.

The principal ores occurring in beds, besides gold,
platinum, and cassiterite, mentioned as found in placers,
are those of copper, lead, zinc, and iron, the last named of
which, as a workable substance, occurs in this country al-
most exclusively in beds.

2. Impregnations. — Impregnations are deposits of
ores found disseminated more or less richly in certain re-
gions of rock, into which they have apparently been in-
troduced subsequently to the origin of the containing rock.
Their determining characters are their subsequent origin,
and their usual lack of any definite limits other than the
extent to which the rock containing them can be profitably
extracted. They may occur (e) as infiltrations into pre-
existing zones of rock, usually having the bedded structure,
which from their porous or cellular texture, or from their
fissured condition, have afforded access to metalliferous
solutions or sublimations by which they have been en-
riched. -Examples of this kind of impregnation are
afforded by the deposits of Silver Reef, Utah, where sev-
eral beds of Triassic sandstone inclosed in clay-slates
contain profitable amounts of silver chloride and sulphides ;
by the deposits of copper glance in the Oscuras Mount-
ains, in New Mexico, which occur impregnating con-
glomerates and decomposed argillaceous slates, and in some

METALLIFEROUS DEPOSITS. 193

cases incrusting or replacing fossil plants and shells ; by
the Triassic sandstone of Cornmern in the Rhenish Province
of Prussia, whose loose, fine-grained sandstone, according
to Credner, sometimes nearly two hundred and fifty feet
thick, is thickly strewed with grains of galena, constituting
one of the most valuable lead deposits in Germany ; and
by the deposits of native copper in the Lake Superior re-
gion, which occur disseminated in sandstones and con-
glomerates, or filling the amygdaloidal cavities in great
sheets of bedded volcanic rock. Impregnations of the
kind here described are often by no means easy to be dis-
tinguished from true bedded deposits. The distinction,
where it can clearly be made out, will depend upon ob-
serving how far all the attending circumstances point
to contemporaneous deposition, or to subsequent introduction.
The usually vague limits of such impregnations may either
coincide in a general way with those of the beds in which
they are found, or they may be confined chiefly to such
portions of them as were most easily permeable to the en-
riching agency.

Besides these independently occurring impregnations,
having no obvious connection with other accumulations
of similar ores from which their materials may have been
derived, others are found (./) closely dependent on other
forms of ore deposit, to which they form a more or less
enriched incasement or zone of contact. They may oc-
cur in the rock inclosing any of the other forms of de-
posit, whether beds, mass deposits, or veins. Their ores
have in some cases, it is probable, been derived merely
from the same source as those of the main deposit, with
which in such case they would be contemporaneous ; and,
since the agency which formed the chief mass permeated
also to some extent the surrounding rock, the ores of both
would be quite likely to have a similar mineralogical
character. In other cases, the enrichment of the sur-
rounding rock has evidently been subsequent to the ac-

1 94 APPLIED GEOLOGY.

cumulation of the main deposit, and has been derived
from it by decomposition and solution of some of its con-
tents. Hence the impregnation in this case would be
likely to hold its ores in mineral combinations somewhat
differing from those of the parent mass.

3. Mass Deposits. — These deposits, called also by
the German name Stocke, are accumulations of ore of
irregular form, but with somewhat clearly marked bound-
aries. The defmiteness of their limits will usually serve
to distinguish them from impregnations ; their great irreg-
ularity of form, and the limitation of their boundaries in
all directions, separate them sufficiently from most veins ;
while they are distinguished from bedded deposits, both
by their irregularity of form and position and by the fact
that their ores are usually subsequent in origin to the in-
casing rocks, in which they either fill pre-existing cavities,
or occupy tracts by virtue of a chemical replacement. In
position these accumulations may coincide in their greater
dimensions with the bedding of the inclosing rocks, or
may be transverse to their bedding planes. In extent,
they vary greatly, many of the lead-bearing crevices and
flats of Illinois and Wisconsin being of no very consider-
able dimensions, while some of the mass deposits of
argentiferous galena, etc. , in our Western Territories, have
yielded hundreds of thousands of dollars' worth of ore ;
and one of the great deposits of cupriferous pyrites on the
Rio Tinto, in southern Spain, was reported in 1883 to be
in places more than thirteen hundred feet wide and six
thousand feet in length. Indeed, their frequent great
dimensions, their comparatively small distance from the
surface, and the consequent ease with which they may be
worked, afford some compensation for the uncertainty
attending their exploration, and the certainty that, when
their boundaries are reached, these isolated deposits will
afford no reliable guide to anything beyond. Similar ore
bodies may be likely to occur in the neighboring rocks,

METALLIFEROUS DEPOSITS. 195

either at the same or at a different geological level, but
their lack of dependence on each other renders each an
object of independent and often costly search.

These accumulations are often found filling partly or
entirely cavernous spaces in limestones (g) which, when
they have been formed by the widening of joints, are
called often gash-veins, or, if by the partial or entire re-
moval of beds, flats. Such are the lead deposits of Illi-
nois and Wisconsin. The ores found in these cavernous
spaces seem either to have been introduced from above,
or to have been acquired by infiltration from the sur-
rounding rocks. (h) Deposits of somewhat similar form,
filling fissures and cavernous spaces in limestones that
have been disturbed and thrown into inclined positions,
and whose ores have, it seems highly probable, been
brought in solution from below through fissures in the
lower rock, may conveniently be called quasi veins, from
the similarity of their position and of their probable mode
of filling to that of fissure-veins. They are also called
chambers by the distinguished geologist Dr. Newberry.
The deposits of gold- and silver-bearing lead-ores of
Eureka, Nev., are examples of this kind of mass depos-
it. (/') Ore accumulations frequently occur occupying
spaces at the plane of contact between rocks of dissimilar
character, and from this circumstance are called contact
deposits. The celebrated deposits of rich argentiferous
lead-ores of Leadville are of this character, occurring at
the contact of porphyry with an underlying limestone.
According to Emmons, these ore-masses are not fillings
of pre-existing cavities, but have been formed by the
replacement of the limestones by ore-bearing solutions
penetrating them from the overlying porphyry. Accumu-
lations thus originating are sometimes called metamorphic
or transformation deposits. Contact deposits and flats
which occupy a nearly horizontal position are frequently
called blanket-lodes. (J) Stockworks are regions of rock

196 APPLIED GEOLOGY.

so cut by a network of irregular, vein-like, ore-bearing fis-
sures or sheets, that the entire mass must be mined out.
An example of this kind of deposit is furnished by the
Fresnillo mines, at Zacatecas, Mexico, which work an
interlaced mass of fissures carrying ores of silver, with
which also the inclosing rock is impregnated to varying
distances from the stockwork.

It is well for the student to bear in mind that the dis-
tinction of these three classes of mineral deposits, viz.,
beds, impregnations, and mass deposits, is not always
sharply drawn nor easily made. The extreme and well-
marked forms will present no great difficulties ; but not
unfrequently they so approximate in characters that they
are classed differently by different observers, and that the
distinction among them, if it can be decisively made, will
depend upon a careful study, not only of the circum-
stances under which they occur, but of the conditions in
which they originated.

4. Veins. — Referring to what has already been said at
page 35 for an account of vein-formed rocks in general,
what follows here will be confined to a description of veins
which carry metallic ores as an important portion of their
contents. Such veins are frequently called lodes, although
this term is sometimes loosely applied to ore deposits
which are not, strictly speaking, veins. Metalliferous
veins are sheets of mineral matter, differing usually some-
what markedly in mineralogical character from the in-
closing or country rock, and filling pretty clearly defined
fissures, or occupying definite structural planes therein.
They tend to a vertical or highly inclined rather than to
a horizontal position ; differing in this respect, as well as
in the subsequent origin of their contents, from bedded
deposits, which originally, at least, must have been nearly
horizontal, and whose ores were deposited as part of the
continuous series of operations that formed the beds.

Segregated veins (k) are lenticular masses, chiefly of

METALLIFEROUS DEPOSITS.

197

quartz, and sometimes of great dimensions, formed appar-
ently by elimination of their materials from the surround-
ing metamorphic rocks, and by the concentration of these
materials along certain planes of the bedding during the
process of metamorphism. Gold is the chief valuable
substance found in such veins, associated always with iron
pyrites and sometimes with chalcopyrite, both of which
may occur in sufficient abundance to be worth working,
even if unaccompanied by gold. Of this kind are the
quartz veins and lenticular masses of chalcopyrite with
pyrites, which occur in the metamorphic schists of the
Alleghany range from Georgia to Canada, and which in
some places contain valuable amounts of gold and copper.
On account of their conformity with the bedding of the
accompanying rocks, they are often spoken of as beds,
though apparently differing in mode of origination from
true beds. Where they swell out to considerable dimen-
sions also, they are indistinguishable from mass deposits,
to which they are closely allied, and with which, doubtless,
they might not inappropriately be classed.

Fissure-veins, or metalliferous lodes (/), are fissures of
the earth's crust which have, subsequent to their forma-
tion, been filled with mineral substances of which metallic
ores constitute a part. Such veins are often of very con-
siderable length, being sometimes traceable for several
thousand feet, or even for miles, in the same general direc-
tion, and it is highly probable that in many cases their ex-
tent is greater than can conveniently be traced. As to
the depth to which they reach, it can only be said that it
is greater than that to which the deepest human workings
have yet been prosecuted, or indeed are likely, for prac-
tical reasons, ever to be prosecuted. Work on metallic
lodes has been suspended, temporarily or finally, at vari-
ous depths and for various reasons, but never, so far as
known, from any real cessation of the vein in depth. The
fissures occupied by the deposits now under consideration

I98 APPLIED GEOLOGY.

are doubtless fractures of the earth's crust, resulting from
deep-seated causes, such as produce uplifts and other
changes of level in rocks, earthquakes, and volcanic out-
bursts. Hence, veins are found chiefly in regions which
have been subjected to powerful agencies of disturbance,
regions rent by the throes of volcanic activity, regions of
metamorphic rocks, mountain-regions, to whose larger
structural lines they conform in direction. Also, the sys-
tem of veins of any special region, made up of a number
of separate veins, presents usually a rude but striking
parallelism among its several members, as might be ex-
pected with fractures produced by the same disturbing
cause, acting with a certain constancy of direction. Ex-
amples of this parallelism are presented by many vein-
mining districts, as in the northwest coursing veins of
Reese River, Nev., and the nearly east and west coursing
veins of Gilpin County, Col. Sometimes a tendency to a
radiate arrangement is observable in a system of veins.

It is obvious, however, that for the formation of a
mineral vein mere fracture of the rocks is not sufficient.
Doubtless many fractures have been made by movements
in the earth's crust, the opposite sides of which have re-
turned so nearly to their original position that no observ-
able space has been left for future deposits. But ex-
tensive rock-fractures inevitably present a very uneven
surface, as can easily be understood by observing, on a
small scale, the irregular surface of a broken block of
stone. If, then, the force which causes fracture causes
also, as is very likely, some movement of the broken parts
upon each other in any direction, it is easy to see that the
fracture will present irregular open spaces, with the oppo-
site walls resting upon each other at some points. The
student can illustrate this clearly to himself by cutting a
sheet of cardboard across irregularly, as was done for
Fig. 1 6 ; or, better, by breaking a block of stone, and then
moving the parts upon each other in any direction. Fig.

METALLIFEROUS DEPOSITS.

199

1 6 presents a section of
such a fissure, which, by
the movement of the upper
part from a to b, presents
the appearance d, while a
movement from a to b'
gives the form c.

To such movements in
their walls is doubtless at-
tributable the striking irreg-
ularity in width which most
fissure-veins present, vary-
ing from bulges of consid-
erable width to a pinch-out,
where the walls are sepa-
rated from each other only
by a seam of clay. In these
faulting movements, the
overhanging portion of the
country rocky significantly
called by miners the hang-
ing wall of the vein, has
usually slid downward on
the underlying or foot-wall
side.

Another means by
which the walls of veins are
held asunder, to be after-
ward filled with minerals
and ores, is by the break-
ing off of fragments of the
hanging wall, either by the
shock that formed the fis-
sure, or by gravity, and
their sliding downward un-
til they become wedged be-

200 APPLIED GEOLOGY.

tween the walls. Such fragments of the country rock en-
countered in mining are called horses or riders, and are
characteristic of many veins. Some of the horses met
with in the famous Comstock vein were of such vast
dimensions as to give it, in places, the delusive appear-
ance of being divided into two veins.

The open fissures thus formed, as also those occupied
by many mass deposits, have doubtless been filled with
their mineral contents, both ores and gangues, by a slow
and long-continued process of deposition from solutions
or vapors circulating through them. In some cases it is
possible that the process has been in part one of sublima-
tion, the ores being introduced into the fissure at great
depths in the state of vapor, and being deposited as a re-
sult of the progressive diminution of heat. In the great
majority of instances, however, all the observed facts point
to water, everywhere present in rocks, as the medium
through whose agency the various vein-forming minerals
have been appropriated, transported, and finally deposited
in fissures which furnished convenient channels for its cir-
culation. Its solvent power has doubtless in most cases
been vastly enhanced by great elevation of temperature
under pressure, and by the presence of various chemical
agents, such as carbonic acid and alkaline sulphides and
carbonates, taken up in its passage through the rocks. It
has permeated the rocks often to vast depths ; has ab-
stracted from them their sparsely disseminated ores and
other minerals which, under the circumstances, it was
capable of dissolving ; and has finally made its way into
open fissures, along whose sides in its upward course it
has deposited its contents in consequence of a decrease of
temperature and pressure, or of some change in the chem-
ical condition of the solution. The source of the miner-
als which fill the veins, therefore, is believed to be usually
the country rock itself, considered in the wide rather than
the merely local sense. Sometimes, indeed, the rocks im-

METALLIFEROUS DEPOSITS. 20 1

mediately adjoining the present position of the ore depos-
its appear to have furnished the ores and gangues by lat-
eral secretion, as is probably true of many vein-like mass
deposits. But, in the case of true fissure-veins, all the
circumstances point to the ascent of the solutions from
great depths, and consequently to the derivation of their
contents from the leaching of areas of the country rock
of considerable extent in both width and depth. These
deposits, therefore, are, as has already been said, concen-
trations, within a limited and available compass, of ores
originally valueless from their wide dissemination. Much
undoubtedly still remains to be done in investigating the
chemistry of the process by which these seemingly insol-
uble substances have been brought into solution ; but
enough has already been done to render no longer doubt-
ful the possibility of the translocation and concentration
through aqueous solution of all the minerals found in veins
and other ore deposits. It should also be borne in mind,
in considering how ore deposits have been accumulated,
that the present condition in which ores occur in veins is
by no means always the same as that in which they were
originally deposited. On the contrary, it is often apparent
that important changes, not only of condition but also of
location within the deposit itself, have taken place since
their deposition. Thus the question that not unfrequently
arises is, not how a given substance could have been dis-
solved, but what was the original form under which it was
rendered soluble and brought to its present place, and by
what means has it been made to assume its present state ?
Some examples of these transformations will be given
hereafter, when we come to consider the surface appear-
ances of ore deposits.

Arrangement of Vein Contents.— The mode of
arrangement of the minerals with which veins are filled
is quite variable. In some, especially those filled mostly
with a single mineral, e. g., quartz, the structure is mas-

2O2

APPLIED GEOLOGY.

sive, any ores that are present being disseminated in gran-
ules often very fine, or in irregular lumps and threads. A
common mode of arrangement, where the veins contain
several minerals, is the banded, in which the different min-
erals, or sometimes different states of the same mineral,
are arranged in more or less regular sheets parallel to the
walls, and often showing duplicated or corresponding
sheets on the opposite walls, as in Fig. 17, which exhibits
a section of a copper-mine in Cornwall, from De La
Beche's " Geological Observer," p. 659.

FIG. 17. — i, i, Country Rock ; 2, Massive Quartz ; 3, 3, Agate-like Quartz ;
4, 4, Quartz-Crystals or Combings ; 5, Chalcopyrite.

Such a structure indicates that different conditions of
deposition prevailed in the fissure at different times, or
that solutions of a different character succeeded each
other during the period in which it received its contents.
In this mode of arrangement the valuable ore usually
forms one or more of the successive bands of the vein
commonly known by miners as pay-streaks. Where vacant
spaces have been left in veins, usually along the plane of
final closure, such spaces are called vugs ; or, where lined
with crystals, as is apt to be the case, they are called druses
or drusy cavities. Ores are often found lining such drusy
cavities. Occasionally the vein structure is brecciated, i. e.,
the fissure has been filled with rounded or angular frag-
ments of the country rock coated and cemented with the
ore and gangue. This type of structure is presented by a
few celebrated mines in our Western Territories. Besides
the modes of occurrence mentioned above, it is common

METALLIFEROUS DEPOSITS. 203

to find ores lining cracks and fissures of the vein-stone in
the form of irregular strings, sheets, and incrustations.

The distribution of the ores in veins is apt to be very
irregular, considerable portions of the vein being practi-
cally barren, or carrying ores of but low grade, while oth-
ers present tracts of unusual richness. Such rich zones
of ore are called bonanzas, or ore-chimneys. They are apt
to occur in the wide portions of veins ; either because
width of fissure and consequent slower movement of ore-
bearing solutions afforded unusually favorable conditions
for deposition ; or because, in the case of subsequent
movement of the vein, crushing and fissuring its original
contents, the wider parts offered favorable places for an
after-concentration of ores within the vein itself. The
Comstock vein of Nevada has afforded many remark-
able examples of the alternation of wide tracts of barren
rocks with ore-bearing zones, sometimes of great extent
and astonishing productiveness, these bonanzas occurring
in the wider parts of the vein. Also, there can be no
doubt that the unequal distribution of ores in many veins
is due in a great measure to the influence of the country
rock ; for where this differs in character in different parts
of the fissure, some portions rather than others promote
the deposition of ores, apparently from their greater
roughness of surface, their readier conduction of heat, or
their presenting conditions for a chemical reaction with the
solutions circulating in the fissure. From these and other
causes, veins usually present an irregularity in the distri-
bution of their ores, as well as a heterogeneity of mineral
composition, in somewhat marked contrast with any
bedded deposits to which they may sometimes bear a close
superficial resemblance.

Characteristic for deposits filling fissures are branch-
veins or leaders, horses, and selvages or fluccan. Branch-
veins, called also leaders and stringers, are small subsidi-
ary veins diverging from the main vein, and leading some

204 APPLIED GEOLOGY.

little distance into the country rock, where they may
gradually die out. They have evidently been formed and
filled by the same agencies as the main veins. Some-
thing akin to branches may occasionally occur in mass de-
posits which fill pre-existing cavities, but they can evident-
ly not occur with beds, since these were deposited upon
the underlying beds, and were subsequently covered by
the accumulation of the overlying ones. Horses have
already been mentioned as portions of the country rock,
usually fragments of the hanging wall of inclined veins,
which have broken off and slid down into the fissure,
where they have subsequently been enveloped by the re-
maining contents. They occur in fissure-veins, and may
occur in some mass deposits, but, not in beds or impreg-
nations. What is called fluccan or selvage is a sheet of
earthy matter frequently found lining one or both walls
of fissure-veins. It is caused sometimes by movements of
the vein, which have ground up the materials along the
walls ; more frequently, doubtless, by the percolation of
water along the walls, and the consequent decomposition
of the adjacent rocks. Such decomposed sheets of rock
are called by the miners gouge, because their softened
condition renders them easy to be penetrated and gouged
out by tools in mining operations. Where the selvage has
been caused by movement, the adjacent rock usually pre-
sents a polished, glazed, and striated surface, termed slick-
ensides, the striations bearing evidence of the direction of
the movement. Appearances of this kind between the
bands of a vein, and others presented by the structure of
the vein contents, not unfrequently testify to the reopen-
ing of a vein after it has been filled, and the formation of
a secondary fissure, which has subsequently been filled
within the vein itself. Thus, in the section presented by
Fig. 17 on a preceding page, the want of correspondence
between the exterior bands 2 and 5 may possibly have
resulted from reopenings of the vein-fissure. An un-

METALLIFEROUS DEPOSITS.

205

doubted illustration of a
vein presenting several re-
openings may be found by
the student in Fig. 292, at
page 658 of De La Beche's
" Geological Observer,"
and another on page 48 of
Phillips's " Treatise on Ore
Deposits."

Veins occupy various
positions with reference to
the structural planes of the
inclosing rock. Most fre-
quently they are found cut-
ting at various angles across
the bedding of the country
rock, where this is percep-
tible : e. g., a, Fig. 18, which
incloses a horse (e).

Sometimes the vein-fis-
sure has followed the con-
tact-plane of unconf ormable
rocks differing in charac-
ter : e. g., b, Fig. 18. Such
veins are called contact-
veins. The Comstock is a
contact-vein through a por-
tion of its course. Final-
ly, where the country rock
is much inclined, the vein
may be mainly parallel to
the bedding, often making
it difficult to determine
whether it is really a fis-
sure-vein or a bedded de-
posit : e. g., c, Fig. 18. In
10

206 APPLIED GEOLOGY.

this case, a decision may often be reached by observing
the presence or absence of horses, stringers, and selvage,
as well as the composition and mode of arrangement of
the contents of the deposit ; by noting whether at all
points of its course it holds the same position among the
inclosing beds, or, rather, breaks across in places so as to
occupy somewhat different planes at different points, as a
vein is likely to do, but never a bed ; and, finally, should
it be crossed by other deposits, by observing whether it is
continuous across these, and whether it causes any change
in the relative position of their opposite parts, neither of
which circumstances could be true of beds. The bedded
vein, c, Fig. 18, is shown to be really a vein : (i) by hav-
ing branches, ff; (2) by crossing the inclosing beds
>at£V (3) by faulting the vein, a; while the deposit, d,
which is everywhere conformable to the bedding, and is
faulted by a, is, so far as these circumstances show, prob-
ably a bed contemporaneous in origin with the country
rock.

Disturbances of Metalliferous Deposits— Faults.
— All the forms of metalliferous deposits are liable to have
their continuity interrupted, either in depth or in hori-
zontal extension, by faults caused by fissures formed since
their deposition by disturbances of the earth's crust.
These faulting fissures may themselves have subsequently
been filled with minerals from solution, constituting veins ;
or they may have remained merely crevices, filled only
with materials formed by the attrition or decomposition of
their walls.

As has already been remarked in a preceding chapter,
the displacement has been caused in the great majority of
cases by the sliding downward of the hanging wall of the
faulting fissure. Such faults are therefore called normal
faults, or simply slides. In cases, however, where the fault-
ing is an attendant result of powerful disturbances and
considerable folding of the strata, examples may occur

METALLIFEROUS DEPOSITS.

207

where the hanging- wall side of the faulting fissure has been
thrust upward, producing a reverse fault, or heave.

In Fig. 19, representing
faults of veins produced by
fissures whose course is ap-
proximately parallel to that
of the veins, i, 2, and 3 illus-
trate normal faults, or slides,
and 4, 5, and 6, heaves ; i
and 4 being caused by fis-
sures dipping toward the
veins, 2 and 5 by fissures
dipping in the same direction
as the vein at a lower angle,
and 3 and 6 by fissures dip-
ping with the vein at a steeper
angle. A simple inspection
of the figures will make it
obvious that, in i and 6, the
continuation of the vein may
be found by a cross-cut from
the interrupted end into the
hanging wall of the vein in
the direction of the arrows ;
that in 2 the cross-cut should
be into the foot-wall of the
vein ; that in 3 and 5 a verti-
cal shaft or winze should be
sunk, and cross-cuts made in
the direction of the hanging
wall of the vein ; while in 4
the vein would be found by
a winze. The cases i, 2, and
3 will be those most frequent-
ly met with. In the absence
of any other means of infor-

208 APPLIED GEOLOGY.

mation as to the direction of the faults of a new region, it
is safest to assume at the outset that the faults, if any occur,
are normal, and to act accordingly. When, however, defi-
nite information as to the direction of faulting has been ob-
tained in some cases by exploration, then it is well to re-
member that the faults produced by the same system of fis-
sures are likely to agree in direction, i. e., to be all slides or
all heaves. The examples given above represent cases where
the continuity of the vein is interrupted in depth. But cases
may occur where a vein is faulted by a fissure striking across
it at a wide angle, in which case, unless the vein be vertical,
or even then if the direction of movement be oblique, the
continuity of the vein in length will be interrupted. Such
cases are not easily represented by diagrams ; but the
thoughtful student, by an attentive consideration of the
respective dips of the vein and of the faulting fissure, will
be able to solve for himself the problem of the relative
positions of the parts of the vein with any given direction
of movement. For example, suppose a vein, in a line with
the observer and dipping to the right, to be cut by a fis-
sure at right angles to its course, and dipping toward him ;
then it is obvious that a slide would throw the portion
nearest to the observer out of line with the rest of the vein
to the left, while a heave would displace it to the right.
Indications of the direction of movement will be likely to
be obtained in practice from striations of the walls of the
faulting fissure, or from the relative positions on its oppo-
site sides of peculiar zones or beds of rock.

Displacements occurring in beds, mass deposits, and
impregnations are not likely to present cases more compli-
cated in character than those of veins, or differing from
them in principle.

Surface Appearance of Ore Deposits. — The char-
acter of those portions of veins and other ore deposits which
are near the surface is commonly very different from that
which the same deposits present at considerable depths.

METALLIFEROUS DEPOSITS.

209

This change of character, which is due to the action of
the air, and of water charged with various chemical agents,
is usually confined chiefly to the uppermost fifty or sixty
feet ; but not unfrequently, in the case of permeable and
fissured deposits, it extends to much greater depths.
" The general character of these altered outcrops consists
in a disintegration and softening of the adjacent country
rock, in the lack of sulphur compounds, and the preva-
lence of metallic oxides, salts of the metals, hydrates, car-
bonates, phosphates, arseniates, chlorides, etc., which often
produce very striking colors ; these change-products are
also, mayhap, accompanied by the development of metallic
copper and silver. In depth, these products of decompo-
sition pass often very gradually into everywhere preva-
lent sulphides of the metals or into iron carbonate."
(Von Cotta.) The superficial materials resulting from this
change have received various names in different regions.
In this country they are usually called gossan, a name de-
rived from the mining districts of Cornwall ; the Germans
apply to them the significant name of the iron hat, and
have an ancient rhyming rule which signifies that however
good a vein may be, it will have an iron hat ; while in
Mexico and South America they are called pacos, colorados
and negrillos. The nature of the change that occurs, and
the special character which the altered outcrop is thus
caused to assume, will naturally depend in every case on
the original character of the contents of the deposit, both
ores and gangues. Probably the most widely diffused and
obvious change is the one which is signalized in the Ger-
man and French name iron hat^ applied to weathered de-
posits, and which originates in the conversion of the wide-
ly disseminated compounds of iron, notably pyrites, into
the hydrated peroxide, giving to the mass a reddish or
yellowish-brown color, and in some cases making it to a
certain depth an available source of iron. Thus the out-
crops of copper deposits present usually a mass of spongy

210 APPLIED GEOLOGY.

iron oxide mingled with the original veinstone, and show-
ing few if any traces of copper, which has been changed
from the original sulphide to the soluble sulphate (blue
vitriol) and washed away. This may be succeeded below
by a rich zone of copper oxides and carbonate with
metallic copper, and finally by the unchanged sulphides
of copper and iron. The copper veins of Ducktown,
Tenn., illustrated by Safford in his " Geology of Tennes-
see," and also by Le Conte in his " Elements of Geology,"
will afford a good example of this kind of transformation.

Deposits of lead and zinc are in like manner found
changed to the carbonates of those metals, cerusite and
smithsonite, sometimes inclosing cores of the original
galena or blende but partially transformed; and where
pyrites was originally mingled with the ores, the carbonates
are reddened or intimately mixed with spongy oxide of
iron, as is the case with the argentiferous carbonates of
Leadville and Eureka. The superficial portions of silver
deposits are apt to contain the precious metal in the form
of native silver or of the chloride, mingled sometimes
with the bromide and iodide, succeeded at greater depths
by the usual compounds of silver with sulphur, antimony,
and arsenic.

Auriferous quartz veins, containing, as they usually do,
disseminated iron pyrites or chalcopyrite, present at the
surface masses of rusty cellular quartz from which the py-
rites has been removed, leaving the rock stained with iron
oxide, and containing the threads and grains of gold in a
state such that it may easily be obtained by crushing and
amalgamation. At no great depth, the unaltered form of
the vein is met with, in which the gold is so associated
with the metallic sulphides as to be by no means so easily
and completely secured.

It is obvious that a knowledge of the surface appearances
usually presented by the ore deposits of any region is of
very great importance to those engaged in searching for

METALLIFEROUS DEPOSITS. 211

such deposits in that region j yet it would be a great error
to suppose that inferences derived from the examination
of the deposits in any one district can be safely treated
as unerring guides in the exploration of all others. For
example, however true it may usually be that the outcrops
of gold-veins are indicated by iron-stained and cellular
quartz, and however expedient it may be to follow up and
test carefully any such indications in a district that is
known to be gold-bearing, yet the converse of the propo-
sition is by no means true, that every outcrop of rusty
cellular quartz is probable evidence of the existence of
gold ; for such appearances occur in many places where
no gold has ever been found. To an important extent,
every mineral region is likely to present distinctive char-
acters of its own ; and general statements as to the effects
of atmospheric and aqueous agencies upon ore deposits
need to be supplemented by a careful study of the special
modifications that are liable to be met with in any particu-
lar district, from differences, it may be, in the nature of
the minerals with which the ores may be associated, or in
that of the substances with which the permeating water
may be charged.

General Distribution of Ore Deposits. — Since, as
has already been remarked, ore deposits seem in all cases
to be concentrations, under favorable conditions, of sub-
stances once widely disseminated in rocks, it is obvious
that they are most likely to be found in localities where
the conditions for such a concentration have been pre-
sented. Such favorable conditions are most likely to be
found in regions cut by ancient eruptive rocks, since they
bespeak the former activity of forces that would produce
fractures and fissures, and would furnish the heat essen-
tial for the solution of many substances found in ore de-
posits ; in regions of fractured, folded, and altered rocks,
mountainous regions, because in them also fissures would
be likely to be opened, the circulation of fluids facilitated,

212 APPLIED GEOLOGY.

and heat generated by the intense exertions of mechanical
force ; in regions of rocks of great geological antiquity,
rather than in those of more modern date, because the
more ancient rocks, by reason of their age, have been
longer exposed to occasions for the action of those slow-
working and protracted agencies by which ore deposits
have doubtless been most largely produced, and because,
to effect the solution and deposition of many highly re-
fractory substances frequently found in veins, masses, and
impregnations, the action of water at a very elevated tem-
perature must be requisite, needing the concurrence of
heat with the pressure of a great thickness of covering
rock, a circumstance which implies not only relative an-
tiquity in the rocks which were the deep-seated theatre of
such action and deposition, but also the lapse of vast pe-
riods of time during which these deeply placed rocks
were elevated and laid open to human search by an enor-
mous denudation ; whence also mountain-regions, whose
rounded forms and comparatively slight elevation above
the general surface show that their very roots have been
exposed by wear, are likely to be more favorable than
those whose rugged and elevated peaks testify to a briefer
exposure to elemental waste.

It will thus be seen that conditions favoring the ac-
cumulation of ore deposits are presented (i) by great
disturbances of the earth's crust by which fissures may be
produced, heat generated, and circulation promoted; (2)
by heat, such as initiates, accompanies, and succeeds out-
bursts of volcanic activity ; (3) by original depth of action
and consequent pressure, through which the solvent possi-
bilities of heated waters are enormously increased ; and
(4) by great lapse of time during which the repeated and
protracted action of agencies seemingly feeble may pro-
duce important accumulations, which may subsequently
be brought within reach of human explorations by great
uplifts and denudation.

METALLIFEROUS DEPOSITS. 213

The regions, therefore, in which the great majority of
valuable ore deposits are found are (i) those which are in
close proximity to eruptive rocks, especially those of some-
what ancient date ; (2) mountainous regions, more par-
ticularly those whose low and rounded outlines show that
large portions of their original bulk have been removed
by denudation ; and (3) regions of rocks geologically
ancient, the more recent formations containing usually
little of value besides iron-ore. It has been observed also
that regions where rocks of very dissimilar character are
found in contact are favorable to the accumulation of ore
deposits, hence contact deposits, whether from their lia-
bility to separate and form fissures as the result of disturb-
ances, or from their presenting planes of easy percolation
to metallic solutions, or from some favoring circumstances
of the wall-rocks.

It should by no means be inferred that regions like
those here enumerated are likely in every case to furnish
valuable ores in some portion of their extent ; but only
that ore deposits occur mainly in such connections and
much more rarely elsewhere. It is well also to bear in
mind that the conditions which have produced one dis-
covered ore deposit in a region are quite likely to have
produced others also which are apt to bear to this some
definite relation of kind, position, or direction.

Prospecting. — What has been said as to the general
distribution of ore deposits may be useful to the observer
at the outset in directing him to the kind of localities
which are likely to reward his search. Its proper appli-
cation will depend, as may be seen, upon some knowledge
of the geological structure of the region, and a prelimi-
nary acquaintance with the general character of its rocks.
Without these, any first discovery of valuable minerals
would be due merely to a lucky accident, as indeed most
first discoveries have probably been. In the absence of
other sources of information, traces of ancient workings

214 APPLIED GEOLOGY.

may prove useful guides to the explorer, indications such
as would be given by old pits not yet wholly obliterated,
and heaps of debris whose weathered contents may afford
some hints of what explorations would be likely to reveal.
Such ancient workings of the aboriginal inhabitants of the
country have led, it is said, to the discovery of some of
the copper-mines of Lake Superior, and of the best mica
deposits of North Carolina. Mere local traditions of the
occurrence of minerals, however, when unsupported by
perceptible traces of former workings, are notoriously
unreliable.

In districts where there is a strong probability of the
existence of ores, useful indications to aid in their search
may be gained in several ways : from peculiarities of vege-
tation, since many ore deposits exert a special influence
on the vegetation along their course ; from the contents or
the depositions of springs issuing from the hidden courses
of veins, etc. ; or from some marked features of the topog-
raphy, such as sharp, narrow ridges marking the outcrop
of veins harder than the country rock, or linear hollows
suggesting the presence of those made up of materials
softer and more easily decomposed than the inclosing
walls. The best and most helpful aid is furnished, how-
ever, by the debris arising from the disintegration and
wear of ore deposits, which is likely to be found strewed
along stream-courses and slopes below the outcrop of the
parent formation. Such transported materials, called
usually shode-stones, or in our Western mining regions more
commonly float, will naturally present the surface appear-
ances of the deposits from which they were derived, such
as cellular iron-stained quartz and the like. These float
minerals, indicating the possible proximity of an ore de-
posit, are traced carefully upward along stream-beds or
slopes, to the point beyond which they are no longer
found; and at this point further search is made for the
originating deposit by trenches or pits excavated to the

METALLIFEROUS DEPOSITS.

215

underlying rock. Should this examination reveal the
probable presence of a vein or some other form of mineral
deposit, more extended explorations are made by means
of pits and shafts, to determine its direction, extent, and
character ; and these explorations are accompanied by
assays, which, if made upon samples fairly taken, may in-
dicate the possible value of the deposit, and whether it is
likely to justify extended working.

Circumstances which condition the Value of
Ore Deposits. — Sound business discretion will naturally
dictate that the work of exploration should be pushed far
enough to reveal the real nature and probable abundance
of the valuable mineral, in both depth and extent, and
that the conditions on which the present and prospective
value of such a deposit must depend should be carefully
considered, before the necessarily costly preparations for
extensive mining and for the beneficiation of the product
should be undertaken.

A primary consideration in determining the value of
an ore deposit will, of course, be the relative amount of
the valuable metallic substance which the ore mass con-
tains. Where the ore is intimately mingled with the
gangue, the value should be estimated on the basis of the
entire mass that must be subjected to the processes of
concentration and reduction. When, however, the ore is
found concentrated into a somewhat definite pay-streak, or
in a narrow vein, while the value of the ore may be esti-
mated on this same basis, careful consideration should be
given to the fact that with the ore a sufficient amount of
barren rock must be taken down to give room for con-
venient mining operations, usually three feet or more in
width, increasing by so much the cost of getting the
really valuable ore. The value of ores of the precious
metals is usually stated as so many dollars or so many
ounces per ton ; thus, an eighty-dollar ore is one contain-
ing that value of gold or silver in a ton. Sometimes the

2i6 APPLIED GEOLOGY.

value of low-grade gold-rock is given as so much per
cord, the cord being approximately eight tons. In the
case of the less valuable metals, like mercury, copper, lead,
and iron, the percentage which the metal bears to the ore
mass is given. It is obvious that to attain even an ap-
proximately reliable estimate of the average value of a
deposit, the samples that are subjected to assay should
fairly represent what must be treated as ores ; otherwise,
all further calculations must be mere wild guess-work, as
indeed too many estimates of the prospects of new mines
are apt to be. Reasonably fair samples can be obtained
only by some systematic operation which will exclude en-
tirely the chance for even an unintentional selection, such
as by taking shovelfuls indiscriminately from many parts
of a well-mixed ore-pile, breaking this material into small
fragments, heaping it up, and subjecting it to successive
quarterings, until a specimen of convenient bulk is ob-
tained for the assayer. Before, however, a final decision
is reached, a mill test should be made, by hauling several
tons of what is to be considered ore to the most con-
venient reduction-works, and finding what it will yield to
this practical test.

Second only in importance to the relative amount of
metal in the ore mass is the state in which it occurs :
whether native, and obtainable by a process merely of
crushing and washing, like the copper-rock of Lake Su-
perior ; or free milling, like some ores of gold and silver,
which after crushing yield their metallic contents mostly to
amalgamation, with little accessory treatment ; or in some
simple form of combination from which the metal may be
liberated by a process involving few operations, like galena
and iron oxide ; or involved in such complications with
other substances as to require an intricate and costly se-
ries of operations for its beneficiation ; whether also, in
case the ore is intimately mingled with so much gangue as
to reduce it below the limits of profit, it is in such physi-

METALLIFEROUS DEPOSITS. 217

cal condition, and bears such relations of gravity to the
gangue, as to admit of easy concentration, and whether in
such case there is a sufficient supply of water for the pur-
pose. It is easy to see that, if one ore costs ten dollars
per ton more for reduction than another, it needs to be
ten dollars richer to pay ; and that if fifty dollars' worth of
ore disseminated through ten tons of vein-stone can, with
but little loss, be concentrated into one ton worth nearly
fifty dollars, it may, if the process of concentration is made
cheap enough by abundant water, become valuable when
it would otherwise be valueless.

The question of ready and cheap transportation is
also one of vital importance. Remote regions, difficult of
access, can utilize at first only their richest ores, those
whose value is so concentrated as to bear heavy transpor-
tation charges and still leave a margin for profit. Every
improvement in the means of communication, every re-
duction in the charges for carriage, will render available
ores of lower and still lower grade, and will bring the
products of such regions nearer in value to more favored
localities. Many districts in our own country of well-
known promise have their mining industries still hampered
by the difficulties and cost of transportation. For what
avail mines capable of producing an abundance of ores of
fair nominal value, all of which and even more may be
consumed by the charges for mining, reduction, and ex-
cessively dear transportation ?

The probable expense of working the deposit also
needs the most attentive consideration, depending as it
does on several circumstances, such as the cost of labor;
the hardness of the rock that is to be dealt with; the
structure of the deposit, whether likely to need much or
little support for roof or walls, and whether the timber for
this purpose is at hand ; the cost of food, tools, and mining
appliances in general ; and the cost of the power that
must be used for hoisting ores, and for handling the water

2l8 APPLIED GEOLOGY.

that is likely to be encountered. All these elements of
inevitable expense must vary greatly, as may readily be
seen, with the circumstances of different localities, and
must be carefully estimated in view of such circumstances,
if one would avoid the risk of unprofitable undertakings.

Finally, the relation which the particular metal that is
to be produced is likely to bear to the supply of human
wants, as indicated by the state of the market for that
metal, needs to be taken into account. For example, a
deposit of copper which, in view of all the considerations
above enumerated, would seem likely to yield a good
profit when the metal is selling at sixteen cents per pound,
might be found to promise no margin of profit with copper
selling at fourteen cents or less.

The practical importance of the considerations given
above, and the frequency with which some of them are
overlooked, sometimes intentionally, by promoters of
mining enterprises, will justify a brief abstract of the chief
conditions on which depends the value of ore deposits :

1. On the relative amount of metal in what must be
treated as ore, needing —

a. Fair sampling to secure a reliable estimate of the

average value.

b. Due consideration of the amount of dead rock to

be handled in securing the ore.

2. On the nature of the combination in which the
metal occurs ; often also on susceptibility to concentration.

3. On situation with respect to cheap transportation.

4. On the cost of exploitation, which includes a con-
sideration of —

a. The cost of labor.

b. The hardness of the rock to be mined.

c. The structure of the deposit as regards the need

of costly support.

d. The cost of food, tools, mining supplies, etc.

e. The cost of power for hoisting and pumping.

METALLIFEROUS DEPOSITS. 219

5. On the relations to the supply of human wants, in-
dicated by current price.

Erroneous Ideas regarding Ore Deposits. —
There are prevalent among persons engaged in mining a
number of false or only partially justified notions, arising
partly from an imperfect knowledge of the true character
of ore deposits, partly from a tendency to too wide gener-
alization in formulating as general laws applicable to all
mining regions the results of an experience gained in
some limited district whose conditions were possibly
largely peculiar to itself. As these ideas in many cases
tend to foster too sanguine expectations, and to encourage
too hazardous ventures without proper examination, while
in others they may unduly discourage careful investigation,
they deserve to be briefly stated and discussed in a work
of practical character, as this aims to be.

1. A somewhat prevalent idea of this kind is, that fis-
sure-veins are likely to increase in width as they descend.
From what has already been said as to the manner in
which open fissures are formed, partly by a faulting move-
ment of walls of irregular contour, partly by the aid of
detached masses of the country rock, it may be seen that
this idea is likely to be baseless. Veins may be expected
to vary greatly in width, passing from a mere narrow clay
seam in one place, to a bulge of considerable width in
another. If now at the present surface, resulting always
from denudation, the vein happens to be encountered at a
narrow point, it will naturally widen for a time, sometimes
to a considerable depth, before again contracting ; if,
however, it should be struck at a wider portion, the con-
trary may be true. The idea has probably sprung from
men's disposition to believe easily what they strongly de-
sire, coupled with the well-known tendency to permit a
single success to blot out the remembrance of many fail-
ures.

2. Somewhat closely akin to this error is the notion that

220 APPLIED GEOLOGY.

fissure-veins grow richer in depth. This may have arisen
from the fact that where the products of the decomposi-
tion of the ores are soluble, as in the case of copper and
silver, the outcropping portions of the veins are impover-
ished, and their true character does not appear until the
weathered portions are passed. When, however, the me-
tallic substance is itself unchangeable, e. g., gold, the out-
cropping portion may be not only relatively richer, but
also much more easily reduced than the unweathered part
of the vein ; so that it may very well happen that a mine
which " pays from the grass-roots " may pay nowhere else,
for the reason that the sparsely distributed metal may be
so involved with other substances in the unchanged vein
as not to yield itself to any cheap method of beneficiation.
Veins, where found in their natural condition in depth,
are likely, as has been stated on a former page, to have
their chief value collected in richer zones alternating with
tracts of ground practically barren, the richer zones being
met with more commonly in the wider parts of the vein.
It will therefore be a mere accident dependent upon de-
nudation, whether the vein shall be struck in a richer or
poorer portion of its extent. The opinion, once current
on high geological authority, that gold has been accumu-
lated in paying quantities only in the superficial portions
of veins, is probably entertained by very few persons at
present, since mining investigations have shown that it
was based on incomplete data.

3. Another current opinion, viz., that certain directions
of strike in veins are decisive indications of their possible
value, and its modification ascribing certain specialties of
course and form to veins of certain metals, may furnish
good illustrations of too sweeping generalizations. It is
undoubtedly true that, within given regions, the courses
of veins, and also of other forms of deposit that have been
greatly disturbed, are likely to have a tolerably definite
direction, conforming themselves, indeed, in a general way,

METALLIFEROUS DEPOSITS. 22I

to the prevailing structural lines of the region due to up-
lifts, as if related to them in origin, as they doubtless are.
The error, then, is not in expecting certain prevailing di-
rections in the courses of deposits in a given region, but
in looking to find the same in all regions, without regard
to that which conditions their direction, viz., the structural
characters produced by upheaval. Still more, it is to be
considered that it is merely the existence of the fissure that
is due to the causes which control its direction, and not
the nature of its contents, whether or not they shall be met-
alliferous, or what ores they shall contain. The filling of
the fissure is a subsequent process, and is due to a quite
different agency. For the forces which produced all the
fissures of any region of fissure-veins, and which hence con-
trolled their direction, were mechanical, and thus totally
different from the chemical agencies which filled them, and
so conditioned the nature of their contents. The same
kind of mechanical forces, exerted in the same region at a
subsequent period and in a somewhat different direction,
may produce a second set of fissures varying in direction
from the first, and which, if filled by solutions of a different
kind, may form veins containing the ores of a different
metal. To this cause is due the fact that veins of the same
region which course differently are apt to have unlike me-
tallic contents. Yet veins of similar ores in distinct min-
ing regions which have different structural features may
have widely different courses, because their courses, and
not their contents, are conditioned by such structural
causes.

4. The sentiment in favor of some kinds of country
rock, as likely to be favorable to richness in deposits, and
against others as likely to be unfavorable, is not without
justification so long as it is restricted to districts in which
such influences have been observed. There is no reason
to doubt that from several causes, some of which have
been briefly mentioned on a preceding page, the country

222 , APPLIED GEOLOGY.

rock does exert an influence on the deposition of the con-
tents of veins. What influence, however, is a matter which
needs to be carefully studied in each region for itself, and
not to be hastily inferred of any region because of observa-
tions made in a different one. For it is to be borne in
mind that the nature of the solutions circulating in fissures
must have been an influential factor in determining the
deposition of ores upon one kind of wall-rock rather than
upon another, the interaction between the two varying
with the nature of the solution ; also, that the relative com-
position of rock species is to a great extent variable and
indefinite, so that one is liable, while using the same rock
name, to be dealing with rocks that, from the difference in
the relative amounts of their constituents, might be likely
to exert notably different influences on ore deposition.*

5. Finally, it may be well. to mention in this connection
the prejudice, common among men engaged in mining, in
favor of fissure-veins, and against some other forms of ore
deposits. It is true that a fissure-vein whose average rich-
ness gives evidence of being satisfactory, has the great
advantage of affording such promise of continuance as to
justify large expenditures for its proper development, but
coupled with the certainty that the cost of both explora-
tion and extraction must increase greatly as depth is at-
tained. Other forms of deposit are, however, not without
their compensating advantages. Mass deposits, for exam-
ple, though of very uncertain extent and duration, are
frequently of vast dimensions, and their uncertainty is
fortunately counterbalanced, as Rossiter W. Raymond re-
marks, not only by this circumstance, but also by " their
comparative small depth and the consequent ease and
cheapness of extraction and of exploration." As a matter
of fact, very large portions of our mineral wealth are de-
rived from deposits other than fissure-veins. Not to men-
tion the vast stores of iron-ore obtained from beds, it is
* Von Cotta, " Erzlagerstatten."

METALLIFEROUS DEPOSITS.

enough to allude, for a few examples out of many, to the
gold derived from placers ; the copper from the deposits
of Lake Superior, whether they be called beds or impreg-
nations ; and the silver and lead from the mass deposits
and quasi veins of Leadville and Eureka. Hence, it is
well for men interested in mining enterprises to cherish
no prejudices for or against particular forms of deposit,
but to endeavor, by the wise adaptation of methods to the
special deposits in hand, to extract from them the greatest
attainable profit, which is the true purpose of all intelligent
mining.

The student will do well to consult, for further information with
regard to ore deposits, " A Treatise on Ore Deposits," J. A. Phillips ;
De La Beche, " Geological Observer " ; R. W. Raymond, chapter on
ore deposits in " United States Report on Mineral Resources," 1870 ;
Burat, " Geologic Applique " ; and Von Cotta, "Erzlagerstatten," Part I ;
also papers on ore deposits by Dr. J. S. Newberry.

CHAPTER XI.

IRON.

IRON may justly claim the foremost place among the
metals, from the indispensable relations which it bears to
most forms of human industry. The sources from which
it is obtained commercially are the oxide ores and the
carbonates, viz., magnetite, hematite, limonite, spathic ore
or siderite, clay iron-stone, and black-band. Richest
among these is magnetite, which when pure contains a little
more than 72 per cent of metallic iron. It is highly mag-
netic, yields a black powder and a black streak on un-
glazed porcelain,and is so hard as to be scratched with diffi-
culty by a knife. It is often crystalline granular, the faces
of the crystals being triangular when perfect. Hematite
when pure contains 70 per cent of iron. It is not usually
magnetic, though sometimes it slightly affects the mag-
netic needle, and its powder and streak are of a dark red.
It varies much in appearance, being sometimes hard and
of a steely metallic luster, when it is called specular ore ;
often constituting a reddish ochreous mass of an earthy
texture ; occasionally composed of black, shining, mica-
like scales, and hence called micaceous ore ; and some-
times made up of red, oolitic grains. Limonite differs
from hematite in being hydrated (combined with water),
and so containing a smaller percentage of metallic iron —
about 60 per cent — and in yielding a brown powder and
streak. It is often found in stalactitic and semi-concre-

IRON. 22$

tionary forms, with a smooth and shining surface, and a
fibrous, often radiated, internal structure. The pure iron
carbonate called siderite or spathic iron-ore, which con-
tains about 48 per cent of metallic iron, is a sparry mineral
of brownish color, and of an easy, threefold rhombohedral
cleavage, in which it closely resembles calcite and dolo-
mite, from which its cleavage angles differ but little.
When strongly heated, it decrepitates, turns black, and be-
comes magnetic ; and when heated in hydrochloric acid,
it dissolves with effervescence, yielding a yellow solution.
In its impure forms it occurs abundantly in certain shaly
strata of coal-regions, mingled with a considerable propor-
tion of earthy matter, forming beds of clay iron-stone, or
collected into kidney-shaped concretions disseminated
through the beds, when it is called kidney-ore ; or some-
times it is found mingled with much bituminous matter
forming black, shaly-looking seams called black-band.
These impure carbonates, though not so rich in iron as
several other ores, by reason of their close proximity to
fuels and fluxes, and of the ease with which they are re-
duced, are a large and valuable source of iron.

Mode of Occurrence. — Although iron- ores are some-
times found filling fissures and irregular cavities, their
usual mode of occurrence in this country is in bedded
deposits, whether disseminated in the beds like the kidney-
ores, or forming nearly the entire bulk of strata which are
not unfrequently of great dimensions. Where the strata
with which they are associated have been greatly altered
and thrown into highly inclined positions, the ore-beds
have much the appearance of veins and are often so called ;
but there is little reason to doubt that they are really beds,
often of lenticular shape, formed as part of the regular
series of events by which the strata in which they are in-
closed were accumulated. Many of the limonites seem to
have arisen from the transformation or disintegration of
other kinds of iron-bearing strata, and occupy somewhat

226 APPLIED GEOLOGY.

ill-defined positions, yet related to those of the probable
parent deposits.

Geological and Topographical Distribution. —
Though small amounts of iron-ores may be found in near-
ly every geological position, still their occurrence in work-
able quantities is chiefly confined to a comparatively few
geological horizons. Of these horizons in this country,
the Archaean is much the most prolific in excellent ores,
magnetite and hematite. From this horizon come the ores,
so largely worked, and furnishing more than half the iron
of the United States, of the Lake Superior region, of
northeast New York and adjacent Canada, of northwest
New Jersey, and of the celebrated Iron Mountain region
of southeast Missouri. Enormous beds of iron-ore occur
also in this horizon in southern Utah, and along the Ap-
palachian range south of New Jersey, especially in North
Carolina.

From the horizon of the Lower Silurian Potsdam and
Calciferous are derived most of the valuable deposits of
limonite which occur along the Appalachain range from
New York and Connecticut to Alabama, and which are
largely worked for local use at many points along this
range, in New York, Pennsylvania, western Virginia, East
Tennessee, and Alabama.

The horizon of the Clinton Group of the Upper Silu-
rian affords a singularly persistent seam of oolitic hema-
tite, which extends with some interruptions from central
New York through Pennsylvania, etc., into Alabama, and
ranges in thickness from one foot to a maximum of twelve
or more feet. Above this horizon little of value is found
until the Carboniferous is reached, where beds of clay
iron-stone, kidney-ore, and black-band, are met with in
most coal- regions, furnishing large local supplies of ores
which are destined to become of increasing value with the
rapid growth of the iron industry on this continent. Ores
of this same character are also found associated with the

IRON. 227

coal-beds of Triassic and Cretaceous age in the United
States, and much of the iron-ore of France, according to
Lebour, is derived from the Jurassic and Lower Creta-
ceous. A famous iron horizon occurs in the Middle Lias
(Jurassic period) of Great Britain, where a clay carbonate
in the so-called Cleveland District, Yorkshire, yields near-
ly one tenth of the iron of the world from an ore averag-
ing 30 to 35 per cent of iron.

Besides the iron regions mentioned above, the United
States is known to possess rich deposits in the Rocky
Mountain region and on the Pacific slope, though they
are still undeveloped save to a limited extent in Colorado
and Oregon. The magnetite deposits of southern Utah
are said to be very extensive. Besides our native supplies
of ore, considerable amounts are yearly imported, chiefly
from the island of Elba, from Algiers, and from Spain,
which last country is reported to mine annually for export
about four million tons of iron-ore.

Other highly important foreign regions of iron produc-
tion, besides those that have been named, are those of the
coal districts of Great Britain ; those of Germany, which
raise her to the third place as an iron-producer ; those in
the ancient crystalline rocks of Sweden and Norway ; and
that of Luxembourg, which supplies much of the iron-ore
smelted in Belgium. It is also recently reported that
southeast Cuba, through American enterprise and capi-
tal, is likely soon to become a considerable producer of
iron-ores.

In the case of a substance so abundant and widely dif-
fused as iron-ore, its economic importance must largely
depend on (i) its proximity to the fuels and fluxes needed
for its reduction to the metallic state, (2) its freedom from
injurious ingredients not readily removed in smelting, and
(3) the percentage of iron which it is capable of yielding.
The fuels used for its reduction are anthracite and dry-burn-
ing bituminous coals, coke, and charcoal ; while limestone is

228 APPLIED GEOLOGY.

the flux most largely employed for removing in the form
of slag the usual silicious and clayey impurities. Near-
ness to the prime necessaries may bring into early use
comparatively lean ore deposits ; while even richer ones,
less favorably located, may wait long for development.
Where, therefore, abundant iron-ores of reasonable rich-
ness are found in convenient proximity to good fuels and
limestone, there prosperous centers of iron production are
likely to arise, and transportation facilities to be furnished.
To such fortunate concurrences is largely due the suprem-
acy in iron production of Great Britain, where the ores
most largely utilized are only moderately rich. Many lo-
calities in our own country afford examples of a similar
character, which are likely to be considerably multiplied
in the near future.

Where abundant and cheap fuel and limestone are not
at hand, an iron-ore needs usually to be both pure and rich
to warrant distant transportation. The most troublesome
impurities in iron-ores are sulphur and phosphorus, neither
of which is easily eliminated from the iron in the process
of smelting, and both of which necessitate increased ex-
pense for even their partial removal. A small amount of
sulphur in iron causes it to be " red-short," i. e., brittle
and difficult to work at a red heat ; while more than a
tenth of one per cent of phosphorus makes it "cold-
short," or brittle when cold, thus unfitting it for many uses
where great strength is required, and rendering it wholly
unsuitable for the manufacture of steel. Where ores are
sufficiently free from these injurious accessories, and are
capable of yielding 60 per cent or more of pig-iron, they
may be profitably transported to smelting centers at con-
siderable distances. Hence the Archaean ores of New York,
Missouri, and of the Lake Superior region, are largely car-
ried for reduction to Pennsylvania, Ohio, and Illinois ;
while the rich and pure ores of Spain and Elba are
brought by cheap ocean-carriage to be mixed with other

IRON.

229

ores in iron for various steel-making processes. A re-
cently devised modification of the Bessemer process,
which, by the use of a basic lining for the converter, con-
sisting essentially of some mineral rich in magnesia, frees
iron from phosphorus, promises to make available for the
highest uses ores otherwise unobjectionable, but held in
bad repute because of their large amount of phosphorus.

According to a somewhat careful estimate of the iron
production of 1882 —

The production of the world was 20,656,184 tons gross or metric ;
„ Great Britain, 8,493,287 gross tons ;

„ United States, 4,623,323 ,,

„ Germany, 2,945,007 metric tons —

these three leading producers having, therefore, furnished
somewhat more than sixteen million tons, or nearly four
fifths of the product of the world. The steel product for
the same year was given as 6,307,756 tons, of which Great
Britain produced 2,259,649 tons and the United States
1,736,692 tons, these two nations together producing nearly
two thirds of the steel of the world.

These figures will serve to give some idea, not only of
the vast proportions of the industries for which iron-ores
furnish the basis, but also of the countries which, by a
fortunate combination of circumstances, seem to be best
adapted to be leaders in those industries.

The rapid growth of the iron industry in the United
States may be seen when it is considered that in 1854 the
entire product was 656,445 gross tons, and that it rose in
twenty-six years to 3,835,191 gross tons in 1880. Among
the States of the Union, Pennsylvania is foremost in pro-
duction, from causes that may easily be inferred, yielding
in 1882 more than 47 per cent of the entire product of
the United States, with Ohio, New York, and Illinois hold-
ing second, third, and fourth rank ; while Michigan, New
Jersey, Tennessee, Missouri, and Alabama each produced
100,000 or more gross tons.
11

230

APPLIED GEOLOGY.

The uses of iron and steel may justly be said to be
coextensive with civilized industry. Some of its leading
uses only can here be indicated, viz., in constructing and
operating railways, for rails, bridges, and rolling-stock ; in
ship-building ; in architecture, for pillars, girders, and mul-
tifarious other purposes ; in tools and machinery for both
agricultural and manufacturing uses ; in pipes for the con-
veyance of water and petroleum, and in tanks for storage ;
in stoves, furnaces, and boilers ; and in wire for fencing
and for lines of telegraph.

The works to which the diligent student might refer for more
complete information with regard to the ores of this important metal
are very numerous. He will do well to consult the Geological Re-
ports of Missouri, Michigan, and Wisconsin, and those of the States
along the great Appalachian range, from Canada and New York to
Alabama, some or all of which may be within his reach. Many valu-
able papers on this subject may also be found in the volumes of
" Transactions of the American Institute of Mining Engineers." The
" Statistics and History of Iron and Steel," in the "Report of the
Tenth Census of the United States," and the article " Iron," in the
" Mineral Resources of the United States," published by the Geologi-
cal Survey, 1883, should be consulted ; also Wright's " Reports on
Mineral Statistics of Michigan," for iSyy-'yS, i88o-'82 ; and Phillips's
" Treatise on Ore Deposits."

CHAPTER XII.

COPPER.

THE chief sources whence are derived the supplies
of this metal of great and growing importance in the
arts, are the native metal, and the sulphides, chalcopyrite,
bornite, and chalcocite. These yield more than seven
eighths of the world's supply of copper, the sulphides
furnishing fully three fourths, while native copper affords
somewhat more than a seventh, mostly from the Lake
Superior region. The remainder is supplied by the car-
bonates, malachite and azurite, and by the red and black
oxides formed by the transformation of other ores, with
minor amounts from the silicate, chrysocolla, and tetra-
hedrite or gray copper. Metallic copper and all its com-
mon ores yield with no great difficulty to the knife, having
a hardness varying from about three to four ; they are
also soluble with more or less ease in nitric acid, giving
green or blue solutions, into which, if a clean knife-blade
be dipped, it will soon be covered with a red coating of
copper.

The native metal is easily distinguished by its well-
known red color, its bright metallic luster, and the flexi-
bility of a thin shaving cut off with a knife.

Chalcopyrite, its most common ore, somewhat resembles
iron pyrites, with which it is often associated, but is easily
distinguished by its greatly inferior hardness, and by its
deeper shade of yellow, with a tint verging on green. It

232 APPLIED GEOLOGY,

is a double sulphide of copper and iron, and yields, when
pure, about 34 per cent of copper.

Bornite, called usually variegated copper pyrites and
erubescite, is also a sulphide of iron and copper of some-
what variable composition, carrying from 55 per cent to
more than 60 per cent of copper. Its color varies from
red to brown, and it easily tarnishes on exposure, taking
the variegated colors from which it derives its common
name.

Chalcocite, or copper glance, is of a dark, lead-gray color,
with usually a blue or green tarnish, and is somewhat
softer than the two preceding ores, with which it is often
associated. It is a simple sulphide of copper, and con-
tains nearly 80 per cent of the metal. These three sul-
phides of copper give fumes of sulphur when heated on
charcoal, and when dissolved in nitric acid, with heat if
necessary, leave a residue of sulphur.

Malachite is a light-green carbonate of copper, holding
nearly 57 per cent of the metal ; and azurite is a blue car-
bonate, with about 55 per cent of copper. Their hardness
is about four, and when dissolved in nitric acid they effer-
vesce from the escape of carbonic acid. They are easily
distinguished by these characters and that of their solu-
tion. When malachite occurs in thick, compact incrusta-
tions, showing delicate bands of color, as in some of the
Siberian mines, it is considerably used as an ornamental
material in inlaid work.

The black oxide of copper, called tenorite, and the deep
red oxide, called cuprite and tile ore, or, when it occurs in
crystals, ruby copper, are both minerals of high specific
gravity, and contain respectively, when pure, 80 and 88
per cent of the metal. Both dissolve in nitric acid, and,
when heated with the blow-pipe on charcoal, yield a
malleable globule of copper. These oxides are often
found in some abundance in the middle and lower zones
of the decomposed parts of copper veins, and are valuable

COPPER. 233

sources of the metal. Large, rounded masses of tenorite,
streaked with green, were found, at an early day, in con-
siderable abundance in the Lake Superior copper regions.

Chrysocolla, a bright bluish-green silicate of copper,
which contains, when pure, about 36 per cent of copper,
is found in sufficient amount in some of our Western cop-
per regions to be a valued source of copper. It has
nearly the same hardness as malachite, for which it* is
often mistaken ; but its shade of color is noticeably differ-
ent, and it does not, like malachite, effervesce with nitric
acid.

Tetrahedrite, called usually gray copper •, from its pre-
vailing color, is a complex sulphide of copper and anti-
mony, with commonly some other metals, notably sil-
ver. It occurs somewhat abundantly in some of the
mines of the Rocky Mountain region, where it is valued
rather as a source of silver than of copper.

Mode of Occurrence. — Copper or its ores occurs in
all the great classes of metalliferous deposits that have
been described in a preceding section : (i) It is found in
veins intersecting the older rocks, or forming lenticular
deposits in certain planes of their highly inclined bedding,
as at many points along the Appalachian Mountains, at the
Bruce and other mines on the north shore of Lake Huron,
at the mines like the Cliff on Keweenaw Point, which have
become famous from the enormous masses of native cop-
per which they have yielded, and in the very rich district
around Butte City in Montana. (2) It occurs in mass
deposits, as along the base of the Sierra Nevada in Cali-
fornia, in the Harz Mountains at Goslar, and in the enor-
mous deposits in southwest Spain on the Rio Tinto, in all
of which localities the copper ore is mingled with large
proportions of pyrites. The very rich copper deposits of
Globe, Arizona, and of the Copper Queen, seem also to be
of this character, though the ores are widely different.
(3) It occurs disseminated in beds, as in the deposits of

234

APPLIED GEOLOGY.

Ste. Genevieve County, Mo., which are in two beds of
Lower Silurian limestone, at several points in the Lower
Silurian beds of Canada, which have not yet risen to great
commercial importance, and in the famous copper slate of
the Harz Mountains, which, in the vicinity of Mansfeld,
yields so large a portion of the copper of Germany from a
seam of but inconsiderable thickness. (4) It is found in
impregnations, as in the rich deposits of native copper,
disseminated in amygdaloids and conglomerates, on Ke-
weenaw Point, in northern Michigan ; in the oxide and
carbonate ores which enrich enormous zones in beds of
felsitic rock, on the boundaries of Arizona and New
Mexico, near the Gila River ; and in the beds of con-
glomerate and underlying slate, impregnated with copper
sulphides and oxide, in the Oscuras Mountains of central
New Mexico. Thus far, in this country, the deposits
which have here been classed as veins and impregnations
have been much the most largely worked, and with the
greatest profit, though important amounts are also pro-
duced from the other two classes of deposit.

Geological and Topographical Distribution. —
Although workable deposits of copper are sometimes found
in formations as late as the Permian, as at Mansfeld, and
in the possibly younger beds of the Oscuras Mountains,
yet they are most largely accumulated in the ancient crys-
talline or eruptive rocks of the Archaean and in the often
much-disturbed and altered beds of the earlier Silurian.

The most notable copper region in North America is
that of the southern shore of Lake Superior, in the north-
ern peninsula of Michigan. The copper here occurs in
the native state, in a very thick series of interbedded vol-
canic rocks, sandstones, and conglomerates, of probably
later Archaean age, though they are thought by some ex-
cellent geologists to belong to the Cambrian. The metal
is found partly in fissure-veins, in which the copper has
been met with largely in masses, sometimes of enormous

COPPER. 235

size, several having been discovered which weighed from
two hundred to nearly five hundred tons ; partly as one of
the minerals filling amygdaloidal cavities in the volcanic
rocks, some of the irregularly shaped masses here also at-
taining considerable dimensions ; and partly disseminated
in conglomerates, in which it constitutes a portion of the
cementing material. The fissure-veins are no longer so
productive as they once were, the great masses being now
unfrequently found, so that the product depends chiefly
on the copper disseminated in lumps, strings, and grains
in the vein-rock. The largest part of the product is de-
rived from the amygdaloids, in which, besides the fine
grains and strings of metal with lumps of a few pounds in
weight, irregular masses weighing more than a ton are
sometimes encountered, filling large scoriaceous cavities in
the ancient lava-beds ; and from the cupriferous conglom-
erates, in which one great mine, the Calumet and Hecla,
produces considerably more than half the copper of the
region from a conglomerate impregnated with about five
per cent of the metal. The amygdaloids are more easily
worked than the conglomerates, and their average of metal
varies from about three per cent in the Quincy mine to
0.72 per cent in the Atlantic. The process of extraction
consists in freeing the lumps and masses, as far as possible,
from the accompanying minerals, by steam-hammers, rock-
breakers, and stamps, stamping the finer copper and gangue
to a coarse powder, and washing away the waste rock in
jigs and buddies, and then smelting the lumps, masses, and
washed grains to rid them of the remaining gangue in the
form of slag.

Second in the list of copper-producers is the region im-
mediately around Butte City, Montana, which in 1882
produced over four thousand gross tons of metal from rich
sulphide-ores, yielding also usually valuable amounts of
silver, and in 1884 reached a production of over eighteen
thousand gross tons.

236 APPLIED GEOLOGY.

Ranking third in amount of metal produced since 1883
are the copper-producing districts of Arizona, at present
three in number. The Clifton district is in the southeast
part of the Territory, on the Gila River, near the boundary-
line of New Mexico. The ores, mostly carbonates and
oxides, are said to occur in enormous zones in vertical
beds of felsite rock, and to average fifteen per cent of cop-
per in a gangue of manganese and iron oxides. The Cop-
per Queen mine at Bisbee is the largest producer in Ari-
zona, having a very rich body of carbonates and oxides in
limestone with, it is said, some native copper, and copper
glance in the deeper workings. A block of this ore, weigh-
ing three tons, recently sent to the Museum of Cornell
University by Prof. W. P. Blake, is made up chiefly of
malachite intermingled with black oxide of manganese and
calcite. The Globe District, in Gila County, though situ-
ated badly in regard to transportation, is yet producing
largely in several mines, the ores of all which are carbon-
ates and oxides, containing also small amounts of the pre-
cious metals. The Old Dominion mine, in this district, is
said to yield annually more than two thousand net tons of
copper. Besides these chief producing centers there are
some other promising mines in this remote Territory, of
which the Peabody, in Cochise County, a little north of
the famous Tombstone region, is stated (" Report of the
Director of the Mint for 1882 ") to be producing at the
rate of eighteen hundred tons per year, from an ore carry-
ing a high percentage of gold and some silver. In 1884
the estimated yield of Arizona was 11,920 gross tons of
copper.

Colorado produces considerable amounts of copper,
solely as a secondary product from ores worked chiefly
for their gold and silver. Most of this is from the mines
of Gilpin County, west of Denver, with smaller amounts
from the San Juan region, and from a locality near Canon
City. New Mexico, though not yet producing more than

COPPER. 237

four or five hundred tons per year, is known to have very
rich deposits in not less than six counties, many of the
mines carrying also important amounts of the precious
metals. Wyoming, in 1883, increased its copper product
about twelve-fold, producing nearly six hundred tons from
mines on the Platte River, ninety miles north of Cheyenne.
The ores are rich carbonates and cuprite. Vermont has
long had a steady production from low-grade pyritiferous
ores, chiefly in Orange County. Besides these main pro-
ducing regions, promising deposits are known to exist and
have been considerably worked in many places along the
Appalachian range, chiefly in western Virginia, the north-
west part of North Carolina at Ore Knob, and at Duck-
town in southeast Tennessee ; as well as in California,
Nevada, Utah, Ste. Genevieve County, Missouri, and in
Maine.

Other North American deposits of copper are found
in the southeast part of Cuba, near Santiago de Cuba,
which formerly yielded annually as high as thirty thousand
tons of eighteen-per-cent ore ; and in the British domin-
ions, on the north shores of Lakes Superior and Huron,
in southern Quebec, and in Newfoundland. Judging from
the statistics of production, these are rather regions of
promise than of present vigorous working, with the ex-
ception of Newfoundland, which in 1883 is credited with
a product of ten hundred and fifty-three tons from two
localities, and of Capelton, in the southern part of Que-
bec, which annually sends to the United States a large
amount of cupriferous pyrites to be used in the manufact-
ure of sulphuric acid, from which is extracted about four
hundred and fifty tons of copper.

Under the existing conditions of production, arising
from large output and low prices of copper, the chief North
American centers of growth for this industry for the im-
mediate future seem likely to be those of Lake Superior,
Arizona, Butte, with probably Wyoming, New Mexico, and

238 APPLIED GEOLOGY.

Newfoundland, and those sections in which, like Colorado,
the production of copper is made an accessory to the ex-
traction of the precious metals, or to the manufacture of
sulphuric acid.

Of the foreign producers of copper on a large scale,
Chili, with Bolivia, still ranks foremost, although the pro-
duction of Chili has greatly diminished in recent years,
while Spain and Portugal have risen to almost equal rank.
The product of Spain is obtained from enormous mass
deposits of copper-bearing pyrites near the Rio Tinto, in
the extreme southern part of the peninsula, and extending
into adjacent Portugal. These great deposits, called mass
deposits (Stocke) by Von Cotta, are pronounced fissure-
veins in a recent account by a French engineer (" Engi-
neering and Mining Journal," November 17, 1883), and
yield an average of about three per cent of copper.

Next to Spain, as a producer of copper, is Germany,
whose largest product by far is derived from the beds of
Mansfeld, before mentioned, the residue coming from cu-
priferous pyrites, mainly from great mass deposits in the
Harz Mountains. Australia also furnishes large amounts,
chiefly from the divisions of South Australia and New
South Wales.

England, once a large producer of copper-ores, has
maintained her supremacy in the copper industry mainly
by large importations of ores, cupriferous pyrites, and par-
tially reduced copper, from Spain, South America, the
Cape of Good Hope, Australia, and some other countries,
her own once famous mines in Cornwall, Devon, Anglesea,
etc., yielding little more than three thousand tons an-
nually.

The following table of the product for 1883, recently
compiled in London, partly from estimates, will give an
idea of the most important sources of supply. In this the
German product has been corrected from more recent
statistics, as also that of the Cape of Good Hope. France,

COPPER.

239

which in 1882 produced 3,627 tons, is for some reason
omitted from this table :

Tons.

United States 52,080

Chili and Bolivia 44,349

Spain and Portugal 43,655

Germany 18,205 *

Australia. 12,000

Cape of Good Hope 5,175

Venezuela 4,018

Norway and Sweden 3,43O

England 3,000

Russia 3,000

Japan 2,800

Italy 1,600

Newfoundland 1,053

Hungary 1,000

Algiers 600

Austria 500

Mexico 489

Peru 395

Canada 329

Argentine Republic. . . 293

Total 197,971

A table of production of the various parts of the
United States in 1882, prepared by the United States Geo-
logical Survey, will show the distribution of our own prod-
uct. It is reduced to gross tons of 2,240 pounds :

Tons.

Lake Superior region 25,439 1

Arizona 8,025

Montana, Butte 4,°44

Colorado 667

Vermont 564

New Mexico 3^9

California 369

Utah 271

Southern States 180

Nevada 156

* Of which 17,501 was from Mansfeld.
f Calumet and Hecla mine, 14,309 tons.

240 APPLIED GEOLOGY.

Tons.

Missouri o ...... 132

Maine 130

Wyoming 45

Pyrites, mostly Canadian 446

From desilverizers 56

Total 40,913

The increase in 1883 was due mostly to the first three
regions in the list and to Wyoming, and in 1884 the esti-
mated product of the United States was 64,831 gross tons.

Uses of Copper. — The uses of copper are numerous
and important. Among these is its employment for
sheathing the hulls of wooden ships ; in wire, in the vari-
ous appliances connected with the widely and rapidly de-
veloping applications of electricity ; in the fashioning of
many articles for domestic uses, and also for manufactur-
ing purposes, such as boilers and evaporating-pans for
sugar-works and stills for distilleries ; as one of the ele-
ments in some forms of galvanic battery ; and as a chief
component in several alloys very largely used in the arts,
such as brass for many parts of machinery and for numer-
ous other uses, and bronze for cannon, bells, and statuary.
It has also a considerable use as an essential or subsidiary in-
gredient in alloys for coins, and for the manufacture of vari-
ous ornaments. Besides this, several of its salts are largely
used in the arts, such as the sulphate, called blue vitriol or
blue-stone, the acetate, known as verdigris, and the brilliant
though dangerous green pigments formed by its combina-
tions with arsenic.

Works to be consulted.

"Mineral Resources of the United States," 1882, article "Cop-
per " ; Von Cotta, " Erzlagerstatten," Part II, for Europe ; Geological
Reports of Michigan, Missouri, Tennessee, and North Carolina ;
Geological Report of Canada, 1863 ; " Third Annual Report of the
United States Geological Survey" — I rving's Report ; Wright's "Re-
ports on Mineral Statistics of Michigan," iSj'j-'jS, 1880, 1882; Phil-
lips, u Treatise on Ore Deposits."

CHAPTER XIII.

LEAD AND ZINC.

Lead. — Lead was smelted in the United States as
early at least as 1825, but during nearly half a century
from that date, down to the close of 1872, with wide fluc-
tuations in the amount of production, the annual out-
put had never exceeded 27,000 gross tons. Since that
date, the discovery of rich stores of argentiferous lead-
ores in Colorado, Nevada, Utah, and some other Western
regions, has swelled our production of lead, mainly as an
accessory to the extraction of silver, to five-fold its for-
mer amount, and we now rank foremost among producers
of this metal.

The sources from which lead is derived are the sul-
phide (galena) and the carbonate, with minor amounts
from the sulphate, which is often associated with galena as
a product of its transformation by atmospheric agencies,
as is also the carbonate.

All these ores yield easily to the knife, their hardness
not exceeding 3 ; they are of high specific gravity, and
are easily fused by the blow-pipe, being reduced to a mal-
leable bead of lead, with the exception of the sulphate,
which requires the addition of soda for its reduction.

Galena, the fundamental and most common ore, occurs
in granular or in cubical crystals, has an easy cubical
cleavage, a lead-gray color, and a brilliant metallic luster,
and contains 86 per cent of lead. The carbonate, cerus-

242

APPLIED GEOLOGY.

site, which contains 77 per cent of lead, is usually white
or gray in color, occurs massive or in right rhombic prisms,
its crystals have a brilliant luster, and it dissolves with
effervescence in nitric acid. Anglesite, the lead sulphate,
holding about 68 per cent of lead, occurs massive or gran-
ular, and is of white or gray color, and bright, resinous
luster. It melts very easily, but yields a bead of lead only
by the addition of soda carbonate ; and it does not effer-
vesce with acids, by which characters it may be distin-
guished from the carbonate.

Nature of Deposits and Chief Geological Hori-
zons.— Ores of lead occur (i) most largely in mass de-
posits in limestone formations, filling irregular cavities
formed by the enlargement of joints, or extending between
beds, or occurring at the plane of contact of limestone
with some rock of dissimilar character. Of this kind are
the deposits of Eureka district, Nevada, of southeast
Missouri, of the Galena district of Illinois and Wiscon-
sin, and of Wythe County, Virginia, occurring in limestone
of Lower Silurian age ; and those of Leadville, and of
southwest Missouri and adjacent Kansas, in limestone of
the Carboniferous.

(2) They are found disseminated in beds, as, e. g., in
beds of Lower Silurian limestone in East Tennessee (Saf-
ford) ; and near Commern, in the Rhenish Province of
Prussia, where they impregnate abundantly thick beds of
loose white sandstone of Triassic age, constituting the
richest lead deposits of Germany.

(3) They occur in veins cutting strata of different
kinds, but productive chiefly in limestone, between whose
beds, or at their contact planes, they not unfrequently
form also flat deposits connected with the fissures, as in
northern England, in Derbyshire, and in the two northern
counties of Wales.

(4) They are also met with in veins, usually more or
less argentiferous, cutting ancient crystalline formations,

LEAD AND ZINC.

243

as at Georgetown and in the San Juan region, Colorado,
at Freiberg in Saxony, and in Cornwall.

The chief lead-bearing geological horizons of this
country and of England are the Lower Silurian and the
Carboniferous, with some in crystalline formations; the
same appears to be true also for Spain ; while in Germany,
lead is derived mostly from Triassic rocks. Limestone
appears to be a rock which is especially favorable to the
deposition of ores of lead. These ores are usually associ-
ated with more or less of silver, sometimes in proportions
too minute to be separated with profit, but not unfre-
quently the silver contents equal or surpass in value the
lead with which they are blended.

Chief American Centers of Production.— Of the
lead production of the United States more than 43 per
cent is credited to Colorado, in which State its extraction
is wholly accessory to that of silver ; and the larger portion
of the product is derived from the famous region about
Leadville. The ore masses are found here chiefly at the
contact of a limestone of Lower Carboniferous age with
overlying masses of porphyry, and, according to Emmons,
they owe their origin to a replacement of the substance of
the magnesian limestones by silver-lead solutions which
were derived from the overlying eruptive rocks. The ores
are argentiferous lead sulphide and carbonate in a gangue
of ferruginous silica and clay. Besides the Leadville re-
gion, the silver-lead veins around Georgetown and in the
San Juan region, cutting Archaean rocks, afford consider-
able amounts of lead.

Next in production to Colorado is Utah, 60 per cent
of whose product in 1882 was derived from the Horn Sil-
ver mine in Beaver County, most of the residue coming
from the region around Salt Lake City. Here, also, as in
all the Rocky Mountain region, the extraction of lead is
an accessory to that of the precious metals, the value of
which usually equals or surpasses that of the lead.

244 APPLIED GEOLOGY.

The mines of Eureka district, in Eureka County, yield
nearly all the lead of Nevada, the reported product varying
from about 8,000 to 28,000 gross tons per annum. The
ores here, which are chiefly carbonate of lead in a highly
ferruginous gangue, carrying 20 to 30 per cent of lead with
a high value in gold and silver, occupy great chambers in
a magnesian limestone of Lower Silurian age. The inclos-
ing limestone is tilted up at a considerable angle, and bears
evidence of great compression, in consequence of which
it -is much fractured and crushed, so that the ore masses,
in their mode of introduction and after -concentration,
seem to have a considerable resemblance to fissure-veins.
They therefore belong to that variety of mass deposits
which in a preceding chapter has been described as " quasi
veins," i. e., those which, while mass deposits in mode of
occurrence, are allied to true veins in having derived their
ores from some deep-seated source rather than from local
concentrations.

The State of Missouri, which is an important producer
of lead, has two geological horizons of lead-bearing strata.
A very considerable area in the southeast portion of the
State, with some of the central counties, has deposits of
lead-ores in Lower Silurian limestones, partly occurring
in mass deposits, partly disseminated in certain of the
beds, according to Prof. Brodhead. The deposits, how-
ever, which are at present most largely worked, are those
occurring in crevices and flats, true mass deposits, in the
•Lower Carboniferous limestones of the southwest part of
the State, about Joplin and Granby, and extending into
adjacent Kansas. The ores here are associated with im-
portant amounts of zinc ores, but contain only insignificant
proportions of silver.

In the Galena district of Illinois, Wisconsin, and Iowa,
lead-ores, associated with zinc but poor in silver, are found
in vertical crevices formed by the widening of the joints
of the Lower Silurian limestone in which they occur, or

LEAD AND ZINC. 245

sometimes in flats between the beds of the limestone. This
region does not appear to be a large producer at present.

Besides these well-known and most largely productive
districts, most of the States and Territories of the Rocky
Mountain division are reported to have promising deposits
of lead-ores, though little worked as yet, unless where they
contain paying amounts of the precious metals. This is
especially true of Montana and of the Wood River region
in Idaho, from both of which a considerable production of
argentiferous lead was reported in 1882. In Wythe Coun-
ty, Va., also, large bodies of sulphide and carbonate of
lead, associated with ores of zinc, are known to exist and
have been somewhat worked, in limestone of Lower Silu-
rian age ; and they need only good facilities for transporta-
tion to build up a prosperous center of metallic production.

The lead product of the United States for 1882, which
was considerably increased in 1883, was reported to be
120,832 gross toris, distributed as follows :

Tons.

Colorado 52,360

Utah 26,786

Missouri, Kansas, Illinois, etc 25,906 *

Nevada 7,670

Idaho 4,45O

Montana .... 3,660

Total 120,832

The foremost foreign producers of lead are Spain, Ger-
many, and England, with minor amounts from Austria,
Greece, Italy, and France. Of these, Spain is much the
largest producer.

The lead-producing regions of this kingdom are in
the provinces of Murcia and Almeria on the southeast coast
near Cartagena, and about Linares, in the province of
Jaen, a little farther inland, on the head-waters of the
Guadalquiver. The district about Linares is said to yield

* Less than one tenth from Illinois and Wisconsin.

246 APPLIED GEOLOGY.

nearly two thirds of the lead, but it is poor in silver ; while
the coast deposits about Cartagena, which, according to
Von Cotta, are veins of galena and blende, cutting Silurian
limestones and slates, contain profitable amounts of the
precious metals.

The large lead product of Germany is derived from
Commern, in the Rhine Province ; from Upper Silesia,
where it is subordinate to a very large output of zinc ; from
the Harz Mountains, Nassau, and Freiberg. At Com-
mern, according to Credner, the galena is found richly im-
pregnating a friable white sandstone of Triassic age, which
attains sometimes a thickness of eighty metres, or more
than two hundred and sixty feet. In Upper Silesia, ac-
cording to the same author, the associated ores of lead and
zinc occur in mass deposits in a dolomitic limestone of
the Muschelkalk (Triassic).

England has also a large but somewhat decreasing pro-
duction, chiefly from Alston Moor, from Derbyshire, and
from Flintshire and Denbighshire in North Wales, with
some from other localities.

The following table of the lead production of the world,
from the latest attainable statistics, will afford a good idea
of the most important lead-producing countries. The
amounts are given in gross tons for England and the
United States ; for the Continental states of Europe they
are supposed to be metric tons of 2,204^ pounds :

Tons.

United States, 1883 129,722

Spain, ,, 123,000

Germany, „ . 89,767

England, 1882 50,328

Austria, ,, 11,899*

Greece, 1881 njoof

Italy, 1873 15, 500 J

France, 1882 8,067

Total 439,983

* Partly litharge. f Amount exported. \ Sardinia.

LEAD AND ZINC. 247

Chief Uses of Lead. — The very great increase in
the production of lead within the past ten years has doubt-
less been attended by a corresponding increase in its use.
It is employed in the arts, in the form of metal, in a num-
ber of important alloys, and in several chemical combina-
tions. As metal, it is used in sheets for covering roofs, for
lining sulphuric-acid chambers in chemical works, and for
conden sing-pans and cisterns, and for lining tea-chests.
It has a large use in pipes for the conveyance of water and
gas. Coated with a thin film of tin, as tin-foil, it has a
large and increasing use for linings and wrappers of many
articles for culinary and other purposes. Its alloys with
tin, bismuth, and antimony are used as soft solder and
pewter, and for type and stereotype metal. Either alone,
or slightly alloyed with arsenic, it is used for bullets and
shot. White lead, an artificial carbonate, the chromate,
or chrome-yellow, and red lead, are largely used as pig-
ments ; both litharge and red lead enter into the composi-
tion of the most brilliant kinds of glass ; and the acetate,
called also sugar of lead, is largely used in the arts and in
medicine.

Books of reference.

" Geological Reports of Missouri " ; " Geological Reports of Illi-
nois," Vol. I ; " Geological Report of Wisconsin," Vols. II and IV ;
" First Geological Report of Iowa," Vol. I, Part I ; " Second Geological
Report of the United States" — Emmons on Leadville ; "Mineral
Resources of the United States," 1882 ; Wallace, "Laws which Reg-
ulate the Deposition of Lead-Ores in Veins " ; Phillips, " Treatise on
Ore Deposits."

Zinc. — The ores from which zinc is extracted are the
sulphide, called blende, smithsonite, the carbonate, and cala-
mine, a silicate of zinc ; besides which, in a New Jersey
locality, three minerals, which are rare elsewhere, occur
abundantly and constitute valuable ores of the metal,
viz., the red oxide zincite, ivillemite another silicate, and
franklinite.

248 APPLIED GEOLOGY.

The most widely diffused ore is that popularly known
as blende, or black-jack, but whose scientific name is spha-
lerite, and which contains 67 per cent of zinc. It occurs
commonly massive, but sometimes in crystals ; has an
easy cleavage, is of a variety of colors, the more com-
mon ones being yellow, brown, and black, with a resin-
ous luster; and its hardness is that of dolomite, yielding
with no great difficulty to the knife. It is infusible before
the blow-pipe on charcoal ; but, when strongly heated, it
yields fumes of zinc oxide which coat the coal with a
yellow film that becomes white when cold ; and in nitric
acid it dissolves, giving the disagreeable odor of sulphu-
retted hydrogen.

The carbonate, smithsonite, which results from the
weathering of the sulphide, contains about 52 per cent
of zinc, and occurs usually in dirty-white or brownish
masses, crusts, or stalactites, which when crystalline have a
pearly luster. It is harder than blende, being somewhat
difficult to scratch ; it dissolves in nitric acid with effer-
vescence, and before the blow-pipe behaves like blende.
This ore is the " dry bone " of Western miners.

Calamine, the common zinc silicate, called Galmei by
the Germans, contains about 54 per cent of the metal, and
occurs usually in whitish masses or crusts, but sometimes
in rhombic prisms with a pearly luster. Its hardness is in-
termediate between that of blende and smithsonite ; and
it dissolves in hot sulphuric acid, the solution becoming
jelly-like when cold.

Zincite, the native oxide of zinc, containing 80 per cent
of the metal, is of a deep-red color, very easy cleavage,
and brilliant luster, and is found usually in cleavable, foli-
ated masses. It is infusible before the blow-pipe, but gives
a zinc film like blende on coal, and, when heated with
borax, yields a yellow glass. It dissolves in nitric acid,
and its hardness is a little greater than that of blende.

Willemite, a second zinc silicate containing 58 per cent

LEAD AND ZINC. 249

of zinc, occurs usually massive, but sometimes in rhom-
bohedral crystals. It has various colors, as yellow, green,
red, and yellowish brown, and, with soda on charcoal, it
gives a zinc film before the blow-pipe. It dissolves in
hydrochloric acid, yielding a jelly of silica, like calamine.

Franklinite, a complex compound of oxides of iron,
manganese, and about 17 per cent of zinc, greatly resembles
magnetite in form, color, magnetism, and hardness ; but
its streak is reddish brown, and before the blow-pipe on
charcoal with soda it yields a film of zinc.

Mode of Occurrence. — In their mode of occurrence
and geological horizons, the ores of zinc present no
marked differences from those of lead, with which, in the
majority of cases, they are intimately associated. Thus,
in the lead regions of Missouri, and of the Galena dis-
trict, forming mass deposits occupying flats or irregular
fissures discontinuous in depth, in limestones of the Lower
Silurian and Lower Carboniferous, the two sets of ores are
found associated ; and in the Galena district, as shown
by Chamberlin, in tolerably equal amounts, though with
a tendency to occupy somewhat different levels ; while in
deposits of similar character in Lower Silurian limestone
near Bethlehem, Pa., the zinc-ores are remarkably free
from lead. In the veins, often following faulting fissures,
productive chiefly in Lower Carboniferous limestones, of
North Wales, Derbyshire, and northern England, the two
ores are also frequently found associated. In the silver-
bearing veins cutting Archaean rocks about Georgetown,
Col., zinc blende is a frequent large constituent of the ore,
making a mixture from which it is difficult to extract the
silver without great loss by volatilization ; and the remark-
able deposits of franklinite, zincite, and willemite, near
Franklin, N. J., in Archaean limestones, form part of the
series of highly metamorphosed and greatly disturbed beds
of that region. These few examples will serve to show
that, although the ores of zinc and lead are not always

250 APPLIED GEOLOGY.

found together, their modes of occurrence are yet striking-
ly similar, even when they form distinct and separate
deposits.

American Centers of Production of Zinc Ores.
— The Lower Carboniferous lead region of southwestern
Missouri and adjacent Kansas, mentioned in the previous
'section, is at present the foremost producer of rich zinc-
ores in the United States, it being estimated to yield fully
two thirds of the zinc which we produce. The ores are
blende, with considerable amounts of calamine. The zinc
deposits of eastern Missouri, covering, in connection with
lead, copper, and nickel, a considerable area in portions of
ten counties, and once yielding a considerable supply of
ores, are said to be doing little at present.

The zinc-ores of the Galena district, blende and
smithsonite, according to Chamberlin are proving fully
equal in amount to those of lead, and show a marked
tendency to accumulation in the limestone crevices at
lower levels than the galena with which they mingle in the
middle zones of deposit. Here, as in Missouri, in the
earlier periods of mining, they were thrown on the waste-
heaps as worthless " black-jack " and " dry bone," but have
later been collected as the basis of a prosperous industry.

The ores of zinc with lead occurring in eastern Ten-
nessee, in the Lower Silurian (Knox dolomite), are re-
ported to be worked for zinc near Knoxville. Passing
northeastward from this point, we meet with the zinc
deposits of Wythe County, Va., and of Lehigh County,
Pa., both in strata of the same geological age as the
Knoxville deposits. According to C. R. Boyd (Institute
of Mining Engineers, June, 1883), the ores of Wythe
County are carbonate and sulphide of zinc, remarkably
free from lead, occurring in great mass deposits in dolo-
mite, and yield a zinc of exceptional purity. The deposits
in Lehigh County, near Bethlehem, are not worked at
present. The ores, blende with the results of its transfer-

LEAD AND ZINC.

mation, smithsonite and calamine, occur in crevices, some-
times parallel, sometimes perpendicular, to the bedding
of greatly disturbed and fractured magnesian limestones,
and seem to belong to the variety of mass deposits which
have been described as " quasi-veins."

The unique deposits of franklinite, zincite, and wil-
lemite, in Essex County, N. J., in the vicinity of Franklin,
are found in Archaean limestone, in beds conformable to
the highly inclined and crystalline strata of the region.
They are of great dimensions, and furnish important sup-
plies of ore for the manufacture of a high grade of metal,
and also of white zinc oxide and spiegeleisen. The re-
gions above described are at present the only important
producers of zinc-ores in North America.

Foreign Zinc-producing Regions. — Among for-
eign producers of zinc, Prussia ranks easily foremost, her
mines in Upper Silesia, in the Rhenish Province, and
Westphalia, yielding more than two fifths of the zinc of
the entire world. The famous zinc district of Upper
Silesia, which yields annually about seventy thousand met-
ric tons of the metal, obtains its ores, chiefly calamine
with minor amounts of blende, from mass deposits in a
dolomitic limestone of Triassic age ; while in the Rhenish
district and Westphalia the ore is blende with but a small
proportion of calamine, in irregular deposits in the De-
vonian or Lower Carboniferous limestone, which is chiefly
dolomitic. The very large product of Belgium is derived
in but small measure from its native ores. According to
the latest returns available, less than 12 per cent of the
zinc- ores smelted in that country came from Belgian
mines, which resemble in character and horizon those of
the Rhine Province ; the residue being imported from
Greece, Sardinia, Spain, Sweden, Germany, and France,
most largely from the two regions first named. England is
a considerable producer of zinc from her lead regions in
Wales, northern England, Cornwall, and Devonshire.

252 APPLIED GEOLOGY.

Besides these countries, France, Spain, Austria and
Poland, Greece and Italy, yield important amounts;
France, as appears from Von Cotta's description, chiefly
from veins in crystalline and eruptive rocks ; and Spain
partly from the lead district near Cartagena, mentioned in
the preceding section, and partly from the province of
Santander, on the northern coast, where large mass de-
posits and impregnations (?) occur in Cretaceous strata
between dolomite and clay slate, which yield nearly two
thirds of the zinc of Spain.

The zinc product of the world, according to the latest
available data, approximates 290,000 gross or metric tons,
distributed as follows :

Tons.

Prussia, 1883 116,644

Belgium, ,, 78,220

United States, ,, 29,747*

England, ,, 27,661 f

France, 1882 18,325

Spain, 1881 7>O32

Austria, 1882 4>79*

Poland, 1883 3,783

Total 286,203

Zinc is used in sheets as a covering for roofs, as a lin-
ing for various receptacles, and as a protection for floors
and walls against the heat of stoves. It has a very im-
portant use in most forms of galvanic battery. It is very
largely used for coating sheet-iron and wire for fencing to
protect them from rust, a process which is called galvaniz-
ing. A single manufactory in this country is said to use
more than three thousand tons annually for galvanizing
fence-wire. Several of its alloys, like brass, Mosaic gold,
German silver, hard solder, and Babbitt's metal, are largely
used in the arts. Among its compounds, zinc-white is a
highly valued paint, zinc sulphate is used in medicine and

* And 9,000 gross tons zinc oxide. f Estimated.

LEAD AND ZINC. 253

in the arts, and zinc chloride is employed in the process
called Burnettizing, for the preservation of timber, as also
for a disinfectant.

As works of reference, most of those mentioned under lead may be
consulted with profit, to which should be added " Geology of New
Jersey," published in 1868.

CHAPTER XIV.

TIN AND MERCURY.

Tin. — Although a sulphide of tin is occasionally met
with, the only ore that seems to be relied upon as a source
of the metal is cassiterite^ an oxide which contains y8f per
cent of tin. It is a brown or black mineral of brilliant
luster when in crystals, and is of nearly the hardness of
quartz. It is infusible by the blow-pipe on charcoal, but,
if soda be added, it yields a white, malleable bead of tin.
It is found sometimes crystallized in modified square
prisms and octahedrons, but more commonly massive, in
grains, lumps, and kidney-shaped masses, which, when
they have a concentric and radiated structure, are called
wood tin, or toad's-eye tin.

Mode of Occurrence and American Localities. —
Tin-ore occurs (a) disseminated in bunches and grains in
veins cutting ancient crystalline rocks like granite, gneiss,
micaceous and hydro-micaceous schists, and is often as-
sociated with a peculiar kind of granitic rock called
greisen, composed of quartz and mica without feldspar.
It is accompanied by a great number of minerals, like
pyrite, chalcopyrite, albite feldspar, tourmaline, and wol-
fram. (<£) From its hardness and unalterability by atmos-
pheric agencies, cassiterite is one of the ores which is
found largely accumulated \nplacer deposits, in the neigh-
borhood of tin-veins, from whose denudation it has been
accumulated in favorable localities ; and it is said that a

TIN AND MERCURY. 255

large proportion of the tin product is still obtained from
this source. Hence the name stream-tin, since these tin
placers are often called streams.

Tin-ore has not been found hitherto in quantities of
economic importance in North America, although a num-
ber of localities, apparently of great promise, have been
discovered within the last few years which seem likely
soon to give both the United States and Mexico a rank
among producers of tin. Quite recently, Prof. W. P.
Blake has reported the occurrence of tin-stone in the
Black Hills of Dakota. It is there found both in placers
and in irregular bunches and seams in veins of coarse
granite, associated in some places with greisen, and in
others in a greisen-like rock of albite and mica.

Tin is reported as occurring in very promising deposits
in two of the southern counties of California, ores from
San Bernardino County giving an analysis of about 60 per
cent of the metal. In Clay County, Ala., deposits of tin-
stone have been opened and worked to some extent since
1 88 1. The ore here occurs disseminated in grains in
vertical beds of gneiss, interstratified with micaceous and
chloritic schists. Six beds of the tin-bearing gneiss are
said to occur, some of them yielding an average of i\ per
cent of the oxide. Tin-ores are said also to have been
discovered at King's Mountain in North Carolina, and at
several other points in the United States, but whether in
quantities sufficient to justify mining, is still to be shown.

Mexico is reported to have deposits of cassiterite of
great extent and high promise in the States of Durango
and Chihuahua, but they are as yet very little worked,
and have not apparently added anything to the supply of
the world. From South America, Bolivia yields annually
about one thousand metric tons, and the States of Colom-
bia are said also to produce small amounts.

Foreign Producers. — The chief supplies of tin are
from three regions, viz., from Cornwall, England ; from

256 APPLIED GEOLOGY.

Banca and Billiton, in the Straits of Malacca, hence called
Banca tin and Straits tin ; and from the eastern part of Aus-
tralia, chiefly from New South Wales, with some from adja-
cent Queensland and Victoria. The tin deposits of Corn-
wall have been worked for many ages, the earliest workings
extending back, it is supposed, some centuries before the
Christian era. The ore is still obtained to some extent
from placers, but chiefly from veins in ancient crystalline
rocks. The Australian deposits, which in New South
Wales are found over an area of 8,500 square miles, oc-
cur in narrow veins, irregularly disseminated in bunches,
grains, and seams, and associated with quartz, feldspar,
greisen, and chlorite, the country rock being, like that of
Cornwall, granite and crystalline schists. The largest
supplies are obtained, however, from extensive placer
deposits derived from the disintegration and wash of the
veins. The latest government report gives the product of
New South Wales for 1883 as 9,125 gross tons of tin and
its equivalent in ore, and the chief hindrance to making
the output much greater evidently arises from the fre-
quent defective supply of water to wash the ore-bearing
gravels. Some of these placer deposits are of very con-
siderable depth, occupying the sites of ancient water-
courses, and are covered with masses of basalt, presenting
a striking resemblance to the deep gold placers of Califor-
nia. The large supplies of Banca and Billiton are said to
be derived chiefly from placers, which yield annually
about eight thousand tons. Besides these, small amounts
of tin are produced in Germany and Bohemia, from de-
posits similar to those of Cornwall, the product of the two
regions amounting together to one hundred and thirty-six
tons in 1882.

The entire product of the world for 1881 is said to
have been 38,123 gross tons.

The statistics of production, so far as they could be
obtained, are as follow :

TIN AND MERCURY. 257

Tons.

England, 1882 9,158

New South Wales, 1883 9,125^

Banca and Billiton about 8,000

Bolivia, 1881 1,000

Germany, 1882 (from Saxony) IO2

Austria „ (from Bohemia) 34

Tin, used somewhat in castings, is much more exten-
sively employed as a coating for other metals, as, for ex-
ample, iron in the widely used tin-plate, copper in many
vessels for culinary purposes, and lead in the so-called
tin-foil. Its alloys, chiefly with copper, but somewhat
with lead and bismuth, are numerous and important.
Among them are bronze, bell-metal, gun-metal, britannia,
pewter, soft solder, Babbitt's metal, and the amalgam with
mercury for coating mirrors, besides several others.

Several of its compounds also have important uses in
the arts. Tin oxide is used for enamels, as a coating for
razor-strops, and for giving a fine polish to some orna-
mental stones ; the chlorides have valuable applications in
dyeing and calico-printing ; and the bisulphide, under the
name of bronze-powder, is considerably used for ornamental
purposes.

Mercury. — Although mercury or quicksilver is not
unfrequently found native in small quantities, the only
source of it which is of economic importance is cinnabar,
the sulphide, which contains when pure about 87 per cent
of the metal. This ore is of a bright red or brownish
red color and scarlet streak ; is of high gravity, about
9, and is easily scratched, its hardness being less than
that of calcite. Before the blow-pipe it is easily dissipated
in vapor, leaving no residue save the substances with
which it may be mingled.

Mode of Occurrence and Localities. — Its mode
of occurrence in all the great producing regions, three in
number, is the same, viz., as an impregnation, either
from solution or from vapor, in certain porous or fissured

258 APPLIED GEOLOGY.

beds of tilted and sometimes metamorphosed stratified
rocks. The three regions, however, while agreeing in the
character of the deposits, contain them in rocks of widely
different geological age ; the Spanish deposits being in-
closed in Silurian strata, the Austrian in rocks of the
Lower Triassic, and the Californian in strata not older
than the Cretaceous.

The production of mercury in the United States,
which is now nearly one half the entire product of the
world, is confined wholly to the vicinity of the Coast
Range in California. In this region, at least eight coun-
ties, ranging from Fresno on the south to Trinity County on
the north, are known to contain workable deposits of cin-
nabar. The richest deposits that have been opened hith-
erto are those of New Almaden, in Santa Clara County,
while important supplies are also derived from Napa,
Lake, Sonoma, and Fresno Counties, the mines in other
sections seeming to depend for their working upon favor-
able prices for quicksilver. The inclosing strata in the
entire region are usually serpentine, and sandstones and
shales, the last-named rocks being sometimes much
metamorphosed, in other cases wholly unchanged, and in
some localities containing fossils of probable Tertiary age.
The cinnabar occurs in irregular deposits, impregnating in
some cases talcose, argillaceous, and jaspery slates ; in
others, sandstone ; while in others, quartzites and opaline
quartz form the gangue. The average contents of metal
in the New Almaden mine are said to be about 3^ per
cent, and the average cost of production in well-conducted
mines is said by Wagoner to be 27 -J- cents per pound.
Throughout the region, irregular deposits of chromic iron
are said to be as constant as cinnabar. As an indication
of the location of the mines whose product is at present
the most important, the following table is given for the fis-
cal year ending June 30, 1883 5 it is stated in flasks of 76 \
pounds :

TIN AND MERCURY.

259

Flasks.

New Almaden (Santa Clara County) 28,753

Napa Consolidated (Napa County) 6,351

Great Western (Lake County) 4,514

Sulphur Bank ,, 4,053

Reddington „ 2,555

Great Eastern (Sonoma County) 2,673

New Idria (Fresno County) 1,720

Other mines 671

Total 5 1,290

The famous Spanish quicksilver mines of Almaden,
northeast of the city of Cordova, have been wrought for
many centuries, having been known, it is said, to the an-
cient inhabitants of the peninsula before the time of the
Roman occupation. The ore deposits here occur in ver-
tical Silurian strata of sandstone, quartzite, and bitumin-
ous schist, with hard sandstone and limestone which do
not contain ores. The cinnabar, in a compact or earthy
condition, is found, in the largest mine, impregnating a
gray sandstone to such a degree that the mass may yield
as much as 25 per cent of mercury, and leave as a residue
when distilled only loose sand. In other cases the impreg-
nated beds are of quartzite, creviced with fissures running
in all directions, into which the cinnabar has penetrated,
forming sometimes also great masses, with occasional cavi-
ties containing metallic mercury. That these deposits are
really impregnations, and not bedded veins, as they have
sometimes been considered from the presence of a selvage,
seems to be conclusively shown by the fact that the origi-
nal planes of stratification of the beds are often percep-
tible in the midst of the deposits. The chief mine in 1851
was already 1,050 feet in depth, and the width which had
been mined out at the 8oo-foot level was said to be 67
feet. No ores are treated here which carry less than two
per cent of mercury, and the cost of production is not
more than twenty cents per pound.

The quicksilver-mines of Idria are in Carniola, in the

260

APPLIED GEOLOGY.

southern part of Austria, not far from the Adriatic Sea,
and have been worked since the latter part of the fifteenth
century. They occur in greatly inclined strata of Triassic
age, impregnating black bituminous schists, or forming
contact deposits between dolomites and slates, or filling
transverse fissures in dolomite and limestone. The work-
ings have now reached the depth of 950 feet, and the ore-
bearing rock is found to grow richer as greater depth is
gained, confirming the opinion that the cinnabar has been
derived from a deep-lying source by infiltration or subli-
mation. The ores of the Idrian mines are reported to
average about 1.6 per cent of mercury, and the annual
production is much smaller than in the other two regions.
Besides these three chief sources of supply, compara-
tively insignificant amounts of mercury are obtained from
Italy and other parts of Europe ; but the total supply es-
timated to be received from these scattered localities is of
little importance, as may be seen from the following statis-
tics of the world's production in the year 1882. In this
table the product is given in flasks, of which those of the
United States, as has already been said, contain 76.5
pounds of mercury, while those of Spain and Austria
hold 76.07 pounds. The amounts are also given in a sec-
ond column in metric tons of 2,204.6 pounds :

PRODUCTION OF MERCURY IN 1882.

Flasks.

Metric tons.

United States

52,372

1, 8^O

Spain . .

AC Q2I

I 6lO

Austria .

ii, 8«^

4OQ

Italy etc., estimated

2,000

<*^y
60

Total

112,506

•7 q-;8

California, therefore, furnished about 46^ per cent of
the mercury of the world, and the New Almaden mine
alone fully 25 per cent.

TIN AND MERCURY. 26l

Uses of Mercury. — The largest uses to which mer-
cury is applied are in the extraction of gold and silver, and
in the preparation of the brilliant pigment vermilion. From
the valuable property which this fluid metal possesses, of
readily forming alloys, called amalgams, with the precious
metals at ordinary temperatures, it has become indispensa-
ble in the processes by which these metals are cheaply
extracted from ores of too low grade to be smelted with
profit ; and about 45 per cent of all mercury is used for
amalgamation. A still larger proportion of the product is
employed in the manufacture of vermilion, the artificial
sulphide of mercury, used as a pigment.

Other important applications of mercury are found in
the making of mirrors and philosophical and meteorologi-
cal instruments, such as barometers and thermometers, in
the manufacture of fulminates for percussion caps, and of
various preparations for medical use, as well as in a pro-
cess for preserving timber from decay, called kyanizing.

Works of reference.

"Geological Report of California," Whitney, Vol. I; J. Ross
Browne, " Report on Mineral Resources of the United States," 1867,
p. 170 ; R. W. Raymond, " Report on Mineral Resources of the
United States," 1873, p. 18 ; Williams, " Report on Mineral Resources
of the United States," 1883 ; " Engineering and Mining Journal," Nos.
for December 24, 1881, and October 7 and December 23, 1882 ; Von
Cotta, " Ore Deposits," Part II, pp. 248 and 455 of German edition ;
Phillips, " Treatise on Ore Deposits."

CHAPTER XV.

SILVER.

THIS, which is counted one of the two precious metals,
and which in all ages of the world has been held in high
estimation and largely used for coinage and for articles
of luxury and ornamentation, is found native in small
amounts in most great regions where it is mined, when it
is easily distinguished by its pure white color, often with
a dark superficial tarnish, by the ease with which it may
be cut and its brilliant luster on a cut surface, and by its
solution in nitric acid, from which it may readily be pre-
cipitated by a clean slip of copper, yielding a coating of
silver, or by a solution of common salt, yielding a white
chloride of silver which soon becomes discolored on ex-
posure to light. More commonly it is found in various
combinations with other substances, forming ores of silver.
Those most largely met with are its combination with sul-
phur, called argentite j with sulphur and antimony, forming
stephanite and pyrargyrite ; with sulphur and arsenic, called
proustite ; with chlorine, called cerargyrite, or horn-silver;
and with sulphur, antimony, and lead, called freieslebenite,
a mineral found as an ore in the mines of Guadalajara in
Spain. It also frequently replaces a part of the copper in
tetrahcdrite, or gray copper, thus making it a valuable ore
of silver, as has been mentioned in the chapter on copper.
In many of our Western mines, also, it is largely obtained
from its associations with ores of lead and with zinc blende.

SILVER. 263

All these ores of silver are so soft as to be easily cut with
a knife, and have a specific gravity varying from 5^ to 7^ ;
all melt with little difficulty before the blow-pipe, emitting
fumes of sulphur, antimony, arsenic, or chlorine, and yield-
ing a bead of silver, either alone or by addition of soda
carbonate ; and all, save cerargyrite, dissolve in nitric acid
with precipitation of any sulphur, antimony, and arsenic
that may be present, and the silver may be deposited from
this solution on a clean slip of copper, or may be precipi-
tated as chloride by salt water. These ores may be dis-
tinguished from each other — argentite, or silver glance, by
its dark lead-color and lustrous streak, its malleability and
sectility, and its yielding a silver bead by heat on charcoal
without soda ; stephanite, or brittle silver, by its black color
and streak ; pyrargyrite, by its usual dark-red though some-
times black color, and its red streak, from which it takes
its common name of ruby silver ; proustite, also called ruby,
or light-red silver-ore, by its light-red color and the odor
of garlic which it emits when heated ; freieslebenite, by its
steel-like color, and its yielding when heated on coal a
globule of silver-lead, from which the lead may be burned
off by heating with the blow-pipe on a little cup of boae-
ash, leaving a bead of silver, an operation which is termed
cupellation ; and cerargyrite, called usually horn-silver, by
its looking and cutting somewhat like horn, and by its
emitting peculiar pungent fumes when heated on charcoal,
and yielding a bead of silver without soda. When pure,
argentite contains 87 per cent of silver, stephanite 69 per
cent, pyrargyrite 59 per cent, proustite 65 per cent, frei-
eslebenite about 24 per cent, and cerargyrite 75 per cent.
Argentiferous galena requires no special description. Its
silver contents may be ascertained by cupelling the silver-
lead globules obtained by heating on charcoal.

When it is considered that an ore-mass containing one
thousand dollars' worth of silver per ton would hold no
more than a thousand ounces avoirdupois per gross ton

264 APPLIED GEOLOGY.

of rock, or about three per cent of silver, and that such an
ore-mass would be counted very rich, while one yielding
one half of one per cent, if abundant, would be worked
with enormous profit, it will be obvious to the student that
the ores of silver, described above, can not usually be ex-
pected to occur in pure and easily determinable masses of
considerable size, but rather as strings, thin seams, and
stains disseminated in a comparatively large bulk of gangue
rock, most commonly quartz or calcite, where its determin-
ation as a silver-ore, and as to the amount which it may yield
per ton, will often be easier and of greater economic impor-
tance than any exact answer to the question of precisely
what silver-ores are present in the mass. For this reason
the description of the most common silver-ores has here
been made chiefly as general as possible, embracing those
characters which are common to them all, as in this form
it will be more likely to be generally useful to the practical
man. For more complete descriptions, and for desirable
additions to the few specific characters here given, the stu-
dent can refer to any good manual of mineralogy like Dana's.

Mode of Occurrence of Silver Deposits.— The
forms of deposit in which workable silver-ores are found
are various, including most, if not all, the chief classes of
deposit described in a preceding chapter. They occur in
veins, cutting granitoid rocks, and crystalline schists of the
Archaean, as in the Reese River region of Nevada, in the
Atlanta and associated lodes of Salmon River, Idaho, in
the mines about Georgetown, Col., and in those of Kongs-
berg, Norway, and Freiberg, Saxony. Some of the great-
est silver-veins of the world are incased in or associated
with volcanic rocks of Tertiary age, called variously an-
desite, propylite, and sometimes diorite, e. g., the celebrated
Comstock vein of Nevada, the Veta Grande of Zacatecas,
and some others in Mexico, and those of Felsobanya and
Schemnitz in Hungary.

It occurs in impregnations, as in the Triassic sand-

SIL VER. 265

stones of Silver Reef, in southwestern Utah, and in the
joints and bedding planes of Devonian limestones of the
White Pine region, Nevada. Associated with ores of lead,
it is found in mass deposits and ^zfcWf-veins, as at Lead-
ville, in many mining districts of New Mexico, and at
Eureka, Nev. It forms flat deposits, connected in origin
with mineralized dikes of eruptive nature, of which char-
acter, according to W. P. Blake, are the silver deposits of
Tombstone in southern Arizona. Finally, as an example
of silver in beds, may be cited the copper schists of Mans-
feld, which, besides affording much of the copper of Ger-
many, yield also important amounts of silver. An inter-
esting occurrence of silver may also be noted here, viz.,
that in the regions of native copper on Lake Superior,
where the two native metals are not unfrequently found
forming parts of the same lump, and thoroughly welded
together without being alloyed.

Regions producing Silver. — Of the vast silver pro-
duction of North America, derived almost entirely from
the United States and Mexico, it may be said in a general
way that, with comparatively trivial exceptions, it is ob-
tained from the great mountainous region of the western
part of the continent, comprised between the Front range
of the Rocky Mountains on the east, and the Cascade and
Sierra Nevada ranges on the west, with their southern ex-
tension into Mexico. The only exceptions worthy of note
are the product of Dakota, which might without great vio-
lence be included in the first, and that of the Appalachian
range mostly from North Carolina, and of Canada, the three
together amounting to little more than three hundred thou-
sand dollars in value in a product of more than seventy-
five million dollars. A similar statement may also be
made with regard to the silver production of South Amer-
ica, second only to that of the United States and Mexico,
which is derived from the Andes and their western slope.

Within the great mountain-region indicated above, the

266 APPLIED GEOLOGY.

United States has much the largest silver production of any
country in the world. Of the eleven States and Territo-
ries included within its limits, all save Wyoming, Oregon,
and Washington, in 1882 yielded amounts of silver valued
at eight hundred thousand dollars or more. The State
ranking highest in silver production in that year was Colo-
rado, whose sixteen and a half million dollars' worth of sil-
ver was derived most largely from three chief districts :
that of which Leadville may be considered the center, in-
cluding Lake County and small portions of Summit, Gun-
nison, Eagle, and Chaffee ; Clear Creek County, of which
Georgetown is the center ; and the San Juan region, in-
cluding portions of about six very rugged and mountain-
ous counties, whose chief centers seem to be Silverton
and Ouray. Besides these chief regions, Boulder, Custer,
Gilpin, and Park Counties yield important amounts. The
mines of these four counties are chiefly in veins, and the
vein system in all of them yields' gold as well as silver;
that of Gilpin County, in particular, affording six times as
much gold as silver. The two great mines of Custer
County, the Bassick and the Bull Domingo, present features
worthy of mention, since their gangue is a kind of breccia
of the country rock, carrying the ores of gold and silver
of the first, and of silver of the second named mine, as a
cementing incrustation of the blocks of stone ; while the
ore-bearing fissure of the Bassick has the character of a
chimney of unknown depth but limited extent, giving rise
to the theory that it is the pipe of an ancient hot spring.

Next in value of silver output to Colorado is Arizona,
in which the noted Tombstone region, in the southernmost
county of the Territory, yields fully two thirds of its sil-
ver ; while Final County, chiefly through the Silver King
mine ; Gila County, so rich in copper ; Yavapai, Yuma, and
Final Counties are also important producers. The large
silver product of Utah may conveniently be said to be de-
rived from three chief districts, of which what may be

SILVER. \ V«J 267

called the Salt Lake district, since its mines use
City as a center or are in convenient proximity to it, in-
cludes Salt Lake and Tooele Counties and the Tintic dis-
trict of Juab County, the ores of which are mostly treated
near Salt Lake ; as also Summit County, in which the very
rich Ontario mine produces yearly about two million four
hundred thousand dollars in silver. In the Frisco dis-
trict of Beaver County, the Horn Silver mine is much the
largest producer ; and the Harrisburg or Silver Reef dis-
trict, in the very southernmost part of the territory, yields
about nine hundred thousand dollars a year from its
unique reefs of sandstone permeated with ores of silver.

Nevada, so short a time ago the foremost State in sil-
ver production, mainly from the Comstock mines, the Eu-
reka and Reese River districts, and from Esmeralda and
White Pine Counties, has during the past few years sunk
to the fourth place, the great diminution in the yield of the
Comstock mines not having been compensated by a corre-
sponding increase elsewhere. Besides the regions named
above, Elko, Lincoln, and Nye Counties are important
producers of silver.

Of the silver produced in Montana, about five sixths
are reported to come from the near vicinity of Butte City,
the remaining sixth being made up mostly by three coun-
ties, Beaver Head, Deer Lodge, and Jefferson, which sur-
round it, in the western portion of the Territory.

The silver of Idaho, amounting to about two million
dollars per year, is derived almost wholly from the three
counties of Custer, Alturas, and Owyhee: in the first,
from the region on the head-waters of the Salmon River ;
in Alturas, from the Atlanta vein and the Wood River re-
gion, these districts being in near proximity to each other ;
while the mining districts of Owyhee County are in the
southwest corner of the Territory, in the vicinity of Silver
City. Most of the silver of New Mexico so far has been
derived from mines along the Mimbres, or Black range,

268 APPLIED GEOLOGY.

and the Socorro Mountains, in portions of Grant, Dona
Ana, and Socorro Counties, in the southwest part of the
Territory ; and that of California from the Sierra Nevada
Mountains, chiefly on their eastern declivity. The an-
nexed table of the silver product of the United States in
1882 will aid the student to gain a clearer idea of its rela-
tive distribution from the preceding brief description.
The values are reckoned on the coinage estimate of silver,
viz., $i.2912o9o- Per ounce, troy. As the selling price of un-
coined silver during that year was not more on the aver-
age than $1.11 per ounce, troy, the real value of the
total is given also at that rate.

Colorado $16,500,000

Arizona 7,500,000

Utah 6,800,000

Nevada 6,750,000

Montana 4,370,000

Idaho 2,000,000

New Mexico 1,800,000

California 845,000

Oregon 35,ooo

Dakota 175,000

North Carolina 25,000

Total $46,800,000, or

$40,179,440 value at $i.n per ounce troy.

Foreign Silver Regions. — In amount of silver pro-
duced, Mexico is second only to her neighboring republic,
the United States. Some of the mines, like those of Gua-
najuato and Zacatecas, have been long known, having been
opened even before the time of the Spanish conquest,
and, though worked fitfully and without system, have
yielded enormous quantities of the precious metal. In
more recent times many of them have fallen into the
hands of English and American capitalists, and with im-
proved methods are yielding regularly and largely.
These silver deposits, chiefly veins, or, as at Fresnillo,
stockworks accompanied by impregnations, follow the line

SIL VER. 269

of the Cordilleras from Tasco, south of the city of Mexi-
co, as far northward at least as Batopilas in the southwest
corner of Chihuahua. The foremost silver-producing
States are Guanajuato and Zacatecas, both of which have
famous mines, as the Valencian in Guanajuato and those
of Zacatecas, Sombrerete, Fresnillo, Pachuco, and Real del
Monte in Zacatecas. Besides these States, silver in im-
portant amounts is obtained from Queretaro, and from
parts of Jalisco, Durango, and Chihuahua. The Mexi-
can yield of silver in 1883 is reported to have been more
than twenty-nine million five hundred thousand dollars.
The deposit of Silver Islet, on the north shore of Lake Su-
perior, which has yielded three million dollars' worth of
the metal, mostly from native silver in a vein cutting Ar-
chaean schists and dikes, is no longer a considerable pro-
ducer; and its companion veins, if any exist, have not
yet been discovered on the mainland.

The silver of South America is derived mainly from
Bolivia and Chili, with much smaller amounts from Colom-
bia and the Argentine Republic, Peru not being named in a
recent list of silver-producing countries published by the
Director of the United States Mint, although in 1880 its
average annual product was given as 79,365 kilogrammes
=$3,298,410, mostly from Cerro de Pasco. These silver
deposits, as has already been said, are in the Andes
Mountains, and on their Pacific slope. The mines of Po-
tosi in Bolivia have been long celebrated, but are now
greatly surpassed by those of Huanchaca and Colque-
chacq, west and north from it. The most important mines
of Chili are in the regions near Copiapo and Iquique, a
port belonging until recently to Peru.

The large silver product of Germany is derived
mostly, it is said, from the vicinity of Freiberg, from the
Harz, and from Mansfeld where it is an accessory to the
production of copper. The silver mines of the Austrian
Empire are in the Tyrol, and on the slopes of the Carpa-

2/0

APPLIED GEOLOGY.

thians at Schemnitz, Kremnitz, and Felsobanya in Hun-
gary, and in Transylvania. Spain produces a consider-
able amount of silver from the mines of Hiendelencia in
the province of Guadalajara, northeast of Madrid, as also
from the argentiferous lead deposits on the southeast coast
in the vicinity of Cartagena and in the northeast part of
the province of Almeria. The product of Norway from
Kongsberg, of Russia from its Siberian provinces, and of
Japan, are none of them so much as four hundred thou-
sand dollars per annum. The silver of Japan, according
to Prof. Lyman, of the University of Tokio, is derived
from argentite, antimonial sulphides, and native silver,
which occur mostly in veins, though sometimes in irregular
mass deposits in volcanic rocks. The production of Japan
was formerly much more considerable than at present.

A table of the production of the precious metals
throughout the world for the year 1883, prepared by the
Director of the United States Mint, has recently been pub-
lished, and the table below is a copy of that portion of
this which relates to silver :

Weight in
kilogrammes.

Mint value.

United States

I III 4^7

Mexico. . .

711 "347

2o 568 ^76

Colombia

18 28^

Bolivia

•284 021

16 ooo ooo

Chili

128 106

Argentine Republic

IO IOO

,j^5,uoo

Canada

AQ one

Russia

7 78l

Austro- Hungary. .

48 708

J^J»4^7

Germany

27O 6oA

Norway

e f\A£

>D09)3°°

I ^82

•^J4.<J4D

Turkey

2 164

Italy

17
bpain

4J^

J7»949

Japan

8 488

Australia

I Q24

JDJ.°^5

80 ooo

Total..,

2.747.78J.

ifcl 14.2 1 7.717

SILVER. 2/1

The silver product of the world, therefore, was 2,747^0% metric tons.
The mint value given in the table is $1.29 ^ per ounce troy, which
equals $41.56 per kilogramme. As the average market rate of silver
during 1883 was $1.10 per ounce troy, a deduction of 14.92 per cent
should be applied to the above, making the real value $97,176,447.

The enormous increase in the production of silver since
1860, resulting from the discovery of our Western deposits
and from the more thorough working of the Mexican
mines, and which has, since the year 1872, increased the
annual output fully 80 per cent, has produced the effect
that might naturally be anticipated for silver, as for any
other metal, of diminishing its value in comparison with
gold and with all salable commodities. It already inter-
feres seriously with its availability for its largest use, viz.,
in coinage, rendering necessary a resort to artificial and
arbitrary expedients for the continuance of its use at a
rate of estimation which was fixed in times when the metal
was much less abundant ; and it threatens, unless a great
falling off in production soon occurs, or unless new and
wider avenues for its employment are soon opened, to
force a fundamental revision in the ideas of coinage, with
the abandonment of any serious attempt to fix its relative
estimate with the less abundant metal, gold, which is so
generally made the standard of value by commercial na-
tions.

Uses of Silver. — The uses of silver have always been
determined by the beauty of the metal, by its rarity in
comparison with other metals save gold, and by its un-
alterability by the ordinary agencies of change which so
soon affect most other metals. From these circumstances
it has for ages been dedicated to coinage, and to the fab-
rication of articles of luxury and ornament, articles which
in a measure bespeak the wealth and importance of their
possessors. For these uses, it is always alloyed with a
certain proportion of copper, usually from 7^ to 25 per
cent, to increase its hardness and durability. Besides

272

APPLIED GEOLOGY.

these chief uses, silver is also largely employed in plating
other metals and alloys, either by applying to them a thin
sheet of silver, or more commonly by depositing the metal
from solution upon the objects to be plated by the gal-
vanic current. Some of the compounds of silver also have
a very considerable use in photography, in surgery, and
in the plating of mirrors.

A table of the uses of silver in the arts, for other pur-
poses than coinage, will be given in connection with gold
in the chapter on gold.

Works of reference.

Clarence King, " Geological, etc., Survey of the Fortieth Parallel,"
Vol. Ill ; " Sutro Tunnel Report " — Von Richthofen's description of the
Cqmstock lode ; " Geology of the Comstock Lode and Washoe Dis-
trict," G. F. Becker, United States Geological Survey; " Second An-
nual Report of the Director of the United States Geological Survey " ;
Raymond's " Reports on the Mineral Resources of the United States,"
from 1869 to 1876 ; " Reports of the Directors of the United States
Mint" ; Von Cotta, " Erzlagerstatten," Part II, for Europe; Phillips,
" Treatise on Ore Deposits."

CHAPTER XVI.

GOLD.

THIS, the more highly valued of the two precious met-
als, is found very widely distributed over the earth, but
usually in traces so minute as to be economically valueless.
It is only when it has been accumulated in rock deposits,
in proportions varying from a considerable fraction of an
ounce to a number of ounces per ton of rock, or when, by
the disaggregation of the containing rocks, it has under-
gone a process of concentration in the channels of ancient
or modern stream-courses, that it becomes an object of
other than theoretical interest. Gold is rarely found form-
ing ores, properly so called, although its common associa-
tions with iron and copper pyrites, and with some other
minerals, are often conveniently called ores. It usually
occurs in the metallic state, almost always alloyed with
more or less of silver and occasionally with other metals.
When it is in visible particles it is readily distinguished by
its yellow color, its luster, its malleability, and by the ease
with which it may be cut with a knife. The only minerals
which are liable to be mistaken for it are iron and copper
pyrites, which somewhat resemble it in color, but in no
other respect, since both are harder, pyrites very much so ;
both crumble instead of flatten under the hammer, and,
though copper pyrites can be cut with no great difficulty,
it yields a greenish powder instead of a flexible metallic
shaving like gold. When heated strongly with the blow-

274 APPLIED GEOLOGY.

pipe, also, gold melts to a brilliant globule on coal, while
both of the minerals in question yield fumes of sulphur.
Besides its usual occurrence as native metal, true ores of
gold are sometimes met with which are compounds of tel-
lurium with gold, either alone, as in calaverite, or with sil-
ver, as in sylvanite and petzite, or with lead, as in nagyagite.
These minerals, which are usually mineralogical rarities
rather than sources of the precious metals, have been found
in sufficient abundance to become valuable ores at a few lo-
calities in our Western mining regions, notably in the region
around Gold Hill in Boulder County, Col., where mines, like
the Red Cloud, Cold Spring, Keystone, and Smuggler, have
yielded considerable amounts ; and in the Bassick mine,
Custer County, Col., where the tellurides occur in some of
the incrustations which cement the breccia-like gangue.

Mode of Occurrence of Gold. — Gold is found in
both original and secondary deposits, the original deposits
being the veins and beds, or impregnations in which it was
originally accumulated by various agencies ; and the sec-
ondary those which have resulted from the disintegration of
the first, and the concentration of their heavy auriferous con-
tents by running water, in the channels and accumulations
of streams, usually in their lowest parts and in their hollows
and eddies, and which are called alluvial deposits, or placers.

Gold-bearing veins occur cutting granite and other
crystalline or eruptive rocks, as in the veins of Gilpin
County, Col., and some of those of California ; or follow-
ing mostly the planes of bedding of highly inclined schists,
of which kind are the veins of Nova Scotia and many of
those of the Appalachian range and of the Sierra Nevada.
In these veins quartz is the usual gangue, in which the
gold is disseminated in minute grains, films, and strings,
usually associated with pyrites, arsenical pyrites, and chal-
copyrite, and not unfrequently with some galena and
blende. In the upper and exposed portions of such veins,
these sulphides have been weathered out, leaving the quartz

GOLD.

275

cellular and rusty and the gold free, so that it is easily ob-
tained by crushing the rock and amalgamating with mer-
cury ; but where the sulphides are not decomposed, the
gold is so incased in them that but little of it can be ob-
tained by such simple methods, and the ores are called
rebellious. In some veins, as in the Comstock, the Atlanta
lode in Idaho, the ^#0j/-veins of the Eureka district, Nev.,
and in the veins of Kremnitz in Hungary, gold is found
associated with silver, forming a considerable part of the
value of the ore body. This is notably the case in those
unfrequent instances where the ores are tellurides, as in
the regions named in a preceding paragraph, and in the
veins of Nagyag, in Transylvania. Besides its occurrence
in veins, gold is also found disseminated in beds of talcose,
chloritic, and micaceous schists, or in lenticular segrega-
tions parallel with their bedding planes. Deposits of this
kind have yielded important amounts of gold, for example,
at King's Mountain and Gold Hill in North Carolina.
(Kerr.) Workable amounts of gold are also sometimes
found as impregnated zones of the country rock of veins.
The greenstone walls of the vein of Kremnitz are impreg-
nated for some distance with valuable amounts of gold ;
and the schists which incase some of the quartz-veins of
California contain gold, possibly derived from the veins.

But, important as are these original and primary de-
posits of gold, and destined as they doubtless are to be-
come in the future even more important, yet the secondary
deposits, or placers, have in all time been the source of
much the largest part of the gold, and continue to be a
very large source, although the output from veins is in-
creasing. Of the enormous gold product of our Pacific
coast fully nine tenths, it is said, has been derived from
placers ; most of the gold of South America is from the
same kind of deposits, as is also two fifths of the product
of Victoria, in Australia, and a much larger proportion of
that from the more northern provinces of the east coast

276 APPLIED GEOLOGY.

of that island ; the large product of New Zealand is mostly
from placers ; and nearly all of that from Russia, from the
Siberian side of the Ural Mountains, is likewise from a
similar source. In Australia, as well as in California, many
of the older and deeper placer deposits have been covered
by thick sheets of volcanic rocks, forming what are called
"deep placers," from which the auriferous gravel is ex-
tracted by subterranean workings, similar to those by
which coal-beds are worked. Gold, as it occurs in placers,
offers some signal advantages to those engaged in obtain-
ing it. By the agencies of disintegration and transporta-
tion, through which the placers have originated, the metal
has been freed from entangling alliances with the sulphides
with which it is so commonly associated, and is presented
in the state most favorable for being seized upon by the
mercury which is used for its collection. Again, the gold,
which in many of its original deposits was in amounts too
minute and insignificant to justify even the least expensive
efforts at extraction, has been mostly separated from its
containing rocks and concentrated into deposits where it
may be profitably worked. A third and very important
advantage is the facility with which enormous amounts of
these superficial accumulations can be handled, and their
valuable contents extracted, by modern hydraulic methods,
where the requisite conditions can be obtained, of sufficient
slope of surface and an abundant supply of water under
great head. Streams of water of from four to nine inches
diameter, and under a head due to a descent of from one
hundred to more than four hundred feet, directed against
a bank of auriferous gravel, unless its parts are very firmly
cemented, tear down and disaggregate the materials with
great rapidity, and send them rushing tumultuously through
long sluices, where the gold is caught by mercury distrib-
uted in the stone or iron riffles with which the bottoms
are paved. In this way gravels which contain but ten to
twenty cents' worth of gold per cubic yard can be profita-

GOLD. 277

bly worked. In placer deposits only are occasionally found
those exceptionally large masses of gold, called nuggets,
which weigh from a few ounces or pounds to one hundred
and fifty pounds and even more. Nuggets of considerable
size have been met with in our Southern Atlantic States
and in California, but the greatest masses of this kind have
been found in Australia, one of which weighed over one
hundred and forty-six pounds, another nearly one hundred
and eighty-three pounds, and two others weighed respect-
ively one hundred and thirty-five and ninety-two pounds.
The largest reported from the United States was from
North Carolina, and weighed twenty-eight pounds avoirdu-
pois, or a trifle more than thirty-four pounds troy. Since
bunches of this size have, it is claimed, not yet been met
with in undecomposed veins, and since the gold of nuggets
is usually considerably purer than that in veins, it seems
possible that the nuggets may be due to some process of
gradual solution and subsequent precipitation of the gold
within the placers, as has been maintained by Prof. T.
Eggleston ; an opinion which has, however, been strongly
opposed by Dr. Newberry, in an article on the " Genesis
and Distribution of Gold," in which an explanation of the
origin of nuggets is given, wholly consonant with the gen-
erally accepted theory of the formation of placers.

Regions of Gold Production.— About 93 per cent
of the gold of the world is derived from four great regions
of production, viz., the mountainous western section of
the United States from the meridian of the Black Hills
westward ; the Australian region, consisting of the eastern
part of Australia, with Tasmania and New Zealand ; the
Russian gold region of Siberia ; and the two northern
divisions of South America, Colombia and Venezuela. If
to these be added the product of Africa, the Austrian
Empire, Mexico, Canada, and Brazil, little more than
$1,000,000 worth per year remains to be credited to the

rest of the world.
13

278 APPLIED GEOLOGY.

The following table of the gold product of the United
States for 1882, from the report of the Director of the
Mint, will afford a fair idea of our gold-yielding regions,
and of their relative importance :

GOLD PRODUCTION OF THE UNITED STATES IN 1882.

1. California $16,800,000

2. Colorado 3,360,000

3. Dakota 3,300,000

4. Montana 2,550,000

5. Nevada 2,000,000

6. Idaho 1,500,000

7. Arizona 1,065,000

8. Oregon 830,000

9. Georgia 250,000

10. Utah 193,000

11. North Carolina 190,000

12. New Mexico 150,000

13. Alaska 150,000

14. Washington 120,000

15. South Carolina 25,000

16. Virginia 15,000

17. Wyoming 5,coo

Total . . $32,500,000

From this table it may be seen that the Southern Ap-
palachian States, which, up to the time of the discovery of
gold in California in 1848, were our sole producers of gold,
but which after that time came to be little regarded, are
again showing much activity and are yielding a creditable
output, aggregating in 1882 $480,000 in value, mostly from
Georgia and North Carolina. The large product of Cali-
fornia, more than one half that of the entire United States,
is credited to no less than thirty-two counties, but is ob-
tained chiefly from the Sierras and their Pacific slope,
Nevada and Mono Counties taking the lead, while Ama-
dor, Plumas, and Sierra Counties have each a product of
more than $1,000,000. Nearly one half the product of

GOLD. 279

Colorado is from Gilpin County, with large amounts also
from Lake, Boulder, Clear Creek, Custer, and Rio Grande
Counties, eight others of the mountain counties aiding to
swell the total. The gold of Dakota is derived from the
Black Hills region in the southwest part of the Territory,
most largely from mines working the enormous belt of low-
grade rock in Lawrence County, but with considerable
amounts also from placers, and from the peculiar fossil
placer of Lower Silurian age which was mentioned in the
chapter on ore deposits, and which is here called cement.
The gold of Nevada is derived mostly from the Comstock
and Eureka district mines, the first group of mines yield-
ing gold and silver in tolerably equal proportions, and the
second producing gold, silver, and lead. The localization
of the gold product of the remaining gold-producing sec-
tions can not be profitably attempted, since the produc-
tion in those new regions is subject to great fluctuations,
from the discovery of new mines and the partial aban-
donment of older locations by a population intent on rapid
gain. Placers of small extent become exhausted and the
course of production drifts elsewhere ; or the weathered
portions of the veins in a newly-discovered territory are
hastily worked out by simple appliances, and then the lo-
cality is measurably abandoned, awaiting the advent of
capital for its more complete and systematic development ;
or rumors of a rich strike elsewhere may cause an almost
total exodus of that adventurous class who are the pio-
neers of all new mining regions. From these various
causes the production of gold in several promising sections
has not yet sufficiently settled about great centers to make
it safe to note them definitely.

An estimate of the gold production of the world for the
year 1883 has recently been published by the Director of
the Mint, which, with a slight rearrangement, to bring to-
gether regions which are contiguous, is given below, with
weight and values :

280

APPLIED GEOLOGY.

Kilo-
grammes.

Value.

United States
Mexico . ...

45,140
i 438

$30,000,000
Q<;5,63Q

Canada

I 4.35

954,OOO

Colombia

5 802

•3 856 ooo

Venezuela
Argentine Republic
Brazil.

5,022

118

QC2

3,333,058
78,546

632, ^ 2O

•$8,140,499 for South

IOQ

72, 375

America.

Chili . .

2AZ

163 ooo

Africa

3 ooo

I,QQ3,8OO

$28 613 880 for South-

Australia, etc

OQ 87-7

26,5OO,OOO

ern Hemisphere and

Japan

181

1 2O O8O

TaDan

Russia

<ie Qja

23,867,Q35

Austro-Hungary . . .
Germany .

1,638
A £7

1,088,615
•2Q3 722

Italy.

IOQ

72,375

$25,363,883 for Eu-

Sweden

•27

24,590

rope.

Turkey ..

6.646

Total

141 47Q

$Q4 O2 7 QOI

From this table it appears that the total annual product
of gold is about 141^ metric tons, worth, at $664.62 per
kilogramme, $94,027,901 ; and that North America pro-
duces over a third of this, chiefly from the Rocky Mount-
ain division of the United States, with nearly a million
dollars' worth each from the Pacific slope of Mexico and
from Canada. The gold of Canada is derived from the
quartz-veins on the Atlantic side of Nova Scotia, and from
veins and placers in Quebec, not far from the United
States boundary ; promising veins of gold-bearing pyrites
also occur in the township of Marmora, Hastings County,
Ontario, and gold is obtained from placers in British Co-
lumbia. Next to the gold product of North America
ranks that of the Australian provinces, from the quartz-
veins and placers of the four eastern divisions of Aus-
tralia, of which Victoria is the largest producer, from
Tasmania and from New Zealand, whose placers yield
several million dollars' worth annually. The Orange
Free State of South Africa exhibited at Philadelphia in

GOLD. 28l

1876 a rich collection of gold nuggets gathered from its
" golden sands " ; and more recently rich placers have
been opened in the Transvaal, from which, and from the
longer known placers of the east and west coast, the gold
of Africa is derived. The best known sources of the large
gold product of Russia are the placers and occasional veins
of the Urals, chiefly on the eastern slope ; and the gold
of the Austrian Empire is derived almost wholly from
Hungary, from veins on the lower declivities of the Car-
pathians and their outliers, ranging from Schemnitz and
Kremnitz in the north, around to the region called the
Banat in the south. The gold of Colombia and Venezu-
ela is derived mostly from placers, the attempts at work-
ing veins having, it is said, not been satisfactory ; and the
production of Brazil, according to recent reports, is ob-
tained mostly from five mines, one of which, the St. John
del Rey, yields fully seven eighths of the entire amount.

Uses Of Gold.— The uses of gold, like those of silver,
have from the earliest periods been based on its intrinsic
beauty, rarity, and unchangeability by chemical agencies,
and have been for coinage and articles of luxury. In
recent years it has had also a considerable use for pens
and dental supplies, as well as for coating less valuable
metals. For coinage and most other purposes it is alloyed
with copper or silver to increase its hardness, the standard
of fineness for coin in this country being nine tenths gold,
and in England eleven twelfths. For other purposes the
amount of alloy varies widely. The report of the Director
of the Mint for the year ending June 30, 1884, gives a
table of the uses of gold and silver for purposes other than
coinage during the fiscal year, based on a wide correspond-
ence with manufacturers ; from which it appears that in
the United States alone nearly fourteen and a half million
dollars' worth of gold, and more than five and a half
million dollars' worth of silver, was so used. This table
is here given :

282

APPLIED GEOLOGY.

Gold.

Silver.

Watch-cases $3,598,308 $1,845,599

Watch-chains 827,000 23,544

Jewelry and watches 7,905,163 1,098,220

Plate 528,868 2,066,294

Leaf 1,084,824 46,883

Pens 145,924 6,730

Spectacles 215,428 23,782

Instruments 5,I99 I3,99°

Dental supplies 37,912 6,738

Supplies for watchmakers, etc 79,227 8,331

Chemicals 31,611 416,419

Total "... $14,459,464 $5,556,530

TABLE OF VALUE OF FINE GOLD.

Per ounce, troy $20.6718.

Per pound, troy 248.06.

Per ounce, avoirdupois 18.84^.

Per pound, avoirdupois 301.46.

Per kilogramme 664.628.

Modes of Extraction of Gold. — Although the ex-
traction of gold from the gold-bearing rock is an operation
which belongs rather to the metallurgist than to the geolo-
gist, yet the great general interest which attaches to this,
the most highly valued of the precious metals, will render
not inappropriate a brief sketch of the two most common
modes of extraction. The mode of getting gold in the
large way from placers by hydraulic methods has already
been outlined, and needs no repetition. Where gold oc-
curs in rock material not intimately associated with sul-
phides, as in some quartz-veins and talcoid schists, or in
the decomposed outcroppings of deposits, it is reduced to
a fine powder or pulp with water in stamp-mills, and the
gold caught on copper plates coated with mercury, and ar-
ranged partly inside the stamp-boxes, partly on an inclined
platform over which the pulp flows after leaving the bat-
tery. At proper intervals of time the amalgam of gold is
scraped from the plates, and, after being cleaned, the vola-
tile mercury is distilled off from the gold by heating in

GOLD. 283

iron retorts. When, however, the gold is involved in sul-
phides like pyrites and arsenical pyrite, and so becomes
what is called rebellious instead of free-milling, it is first
crushed to powder in a stamp-mill or otherwise, in which
operation any free gold may be caught as in free-milling if
thought desirable ; second, concentrated, i. e., freed from
gangue by washing in gigs, buddies, or vanners ; third,
roasted, to free the sulphides from sulphur and reduce
them to oxides, thus liberating the gold from its entangle-
ments ; and, fourth, the gold is amalgamated, or, better, re-
duced to the form of the soluble chloride of gold, by
treating the moistened pulp with chlorine gas in a suitable
vessel, an operation which can be greatly hastened by
keeping the pulp in motion, and introducing the chlorine
under considerable pressure (Mears's process) ; when, fifth,
the chloride is leached from the pulp with water, and the
gold precipitated as a powder by adding a solution of iron
sulphate. When the gold is associated with valuable
amounts of copper, a much more complicated process of
smelting and separation of the metals is resorted to, for
which any one interested in such matters will need to refer
to treatises on metallurgy.

Works of reference,

Besides the works mentioned under silver, most of which are ap-
plicable also to gold, the student will do well to consult Whitney's
"Treatise on the Auriferous Gravels of California" ; Dawson's " Aca-
dian Geology " ; the Geological Reports of Canada for 1863 and 1870-
'71 ; " Geological Reports of North Carolina," Emmons, 1856, and
Kerr, 1875 ; and also numerous papers in " Transactions of American
Institute of Mining Engineers." Many other works might easily be
named, but some of the above are most likely to be accessible to the
diligent student.

CHAPTER XVII.

PLATINUM AND OTHER METALS.

Platinum. — This metal, whose singular infusibility
and indifference to nearly all chemical reagents, com-
bined with its remarkable ductility and its malleability,
make it an object of great importance in the arts, is
always found in the metallic state, and usually alloyed
with iron and certain rare metals, of which the most com-
mon are iridium and osmium. It has never yet been
found in any other than placer deposits, in which it
usually occurs in flattened grains, readily distinguished by
their infusibility and malleability, and their great specific
gravity. Nuggets of considerable size are also occasion-
ally met with, the largest of which, according to Phillips,
weighed twenty-two pounds troy. Although the original
deposits from whose destruction the platinum has been
supplied to placers have never yet been discovered, still,
according to Von Cotta, its occasional occurrence with
chromic iron in bits of serpentine, point to veins of that
mineral as the source of the metal. Although platina was
first discovered in Colombia in 1735, an(^ ^as smce been
found at several points in Brazil, it does not appear that
South America adds any important amount to the small
product of the world. Nearly the whole supply is derived
from placers on the east slope of the Urals in Russia, the
product of 1881 amounting to 6,798 pounds avoirdupois.
Besides this, Borneo is said to furnish about five hundred

PLATINUM AND OTHER METALS. 285

pounds a year, and in 1882 the United States yielded
about thirteen and three fourths pounds avoirdupois. The
entire product of the world does not probably exceed
four net tons per year. Discoveries of small quantities of
platinum have repeatedly been announced from various
localities of the United States, especially in the gold
placers of California, and recently in the Wood River
region of Idaho ; but nothing of economic importance
has yet come to light, although the demand for the metal
to be used in the arts constantly exceeds the meager sup-
ply. It is quite possible that a careful examination of the
placer deposits of California might reveal a much greater
abundance of this metal than has been suspected hitherto.
Indeed, operations directed to securing gold from aurifer-
ous sands, by washing and amalgamation, would be very
little likely to detect platinum, which does not amalga-
mate. If the idea of Von Cotta and also of Prof. W. P.
Blake is well founded, that the mother rock of platinum is
serpentine, the most promising localities in which to search
in California will be those alluvial deposits which have
been formed from the cttbris of the serpentinous rocks of
the Coast Range.

The uses of platinum are based on its infusibility, its
resistance to most chemical agents, and its ductility. It
is used in chemical manufactories for the large stills in
which the ultimate concentration of sulphuric acid is
effected ; in numerous forms of chemical apparatus, as
crucibles and evaporating dishes, and as foil, wire, and
the tips of forceps to support objects in blow-pipe opera-
tions ; as one of the elements in the most powerful form of
galvanic battery ; in fine wire for incandescent lighting by
electricity, and for forming the cutting edge of a number
of surgical instruments — the wire, when in use, being
heated to whiteness by a galvanic current, and searing as
it cuts so as to prevent the effusion of blood. Platinum is
used somewhat for medals and ornaments, for dentists'

286 APPLIED GEOLOGY.

supplies, and in porcelain-painting, to give a steel-like
color to objects, and it was once used in Russia for coin-
age. Its uses would doubtless be much extended did the
supply of the metal permit.

Nickel and Cobalt. — Nickel, which, from its wider
applications and its valuable properties, has within a
comparatively recent period come to be a metal of in-
creasing economic interest, is derived from ore compounds
with sulphur, arsenic, and silica, in which it is very com-
monly associated with cobalt, forming a considerable group
of minerals, of which the most common are millerite, a yel-
low sulphide in needle-like crystals or wool-like bunches ;
siegenite, a steel-gray sulphide of nickel and cobalt ; nicco-
lite, or copper nickel, a copper-colored arsenide ; and sili-
cates of an apple-green color, which have recently been
found in so considerable quantities and of such excep-
tional purity on the island of New Caledonia as seriously
to affect the price of the metal. The ore from which the
largest supplies have always been obtained is magnetic
iron pyrites, containing nickel, with which some of the
other nickel compounds are often associated. Although
ores of nickel occur at numerous localities in the United
States and Canada, mostly in ancient crystalline rock, and
often associated with serpentine, as on the north shore of
Lakes Superior and Huron, at Oxford in Quebec, and
Chatham, Conn., its extraction has been attended with
success only at the Lancaster Gap mines in Pennsylvania,
which have yielded in some years fully one fifth the nickel
of the world from arsenical pyrites and millerite aver-
aging not more than two per cent of the metal ; and at
Mine La Motte, in southeastern Missouri, where its extrac-
tion was subsidiary to the production of lead. Besides
these localities, deposits said to be of great promise occur
in Churchill County, Nev., and in Douglas County, Ore., in
which last region the ores are green silicates, resembling
in grade and purity those of New Caledonia. Near Schnee-

PLATINUM AND OTHER METALS. 287

berg, in Saxony, are mines which have been wrought for
more than two centuries, yielding nickel, cobalt, bis-
muth, and arsenic, and which still furnish most of the im-
portant production of Germany. The silicate ores of
New Caledonia, which yield a nearly pure metal more
easily than any others known, are mostly shipped to
France, of which the island is a penal colony. Although
the ores of nickel occur usually in veins, in Mine La
Motte, mentioned above, they are found in a thin seam
of slate associated with the lead-bearing Lower Siluri-
an limestones of that region, or coating the seams of
galena.

The entire amount of nickel produced in 1877 was
estimated at 550 metric tons. No complete statistics of
nickel production are attainable ; but that of the United
States in 1882 was 125 metric tons, and that of Germany
for the same year was 121 metric tons, France yielding 30
metric tons. The chief uses of nickel are for the alloy
called German silver, for minor coinage, and for electro-
plating, for each of which uses the demand is very con-
siderable. German silver, which is an alloy of copper and
zinc with one third or less of nickel, is largely used for
fabricating many domestic implements and wares, which
are then electro-plated with silver. An alloy of 25 per
cent of nickel with 75 per cent of copper is used in the
United States coinage for three and five cent pieces, and
one containing 12 per cent of nickel for pieces of one
cent. Nickel alloys are used also in Germany and Bel-
gium for minor coinage. For the electro-plating of many
instruments, articles of domestic use, portions of stoves
and machinery, nickel is peculiarly adapted by reason of
its hardness, its difficulty of fusion, its resistance to rust,
and its susceptibility to a high polish ; and its use for
this purpose is very large and rapidly increasing. By a
recently devised process, it is possible to make nickel-
coated iron-plate, which, for the manufacture of cooking

288 APPLIED GEOLOGY.

utensils that are to be subjected to heat, has several strik-
ing advantages over tin-plate.

Of cobalt, whose ores occur very commonly associated
with those of nickel, it is sufficient to say that it is pro-
duced in small amounts in the United States at the two
nickel-producing localities ; that it has at present no use
as a metal ; and that it is employed to give a blue color
to glass, porcelain, and earthenware, in the form of the
black oxide, and of smalt, which is a silicated oxide made
by fusing cobalt oxide with glass, or with quartz sand
and potash. The production of cobalt oxide at the works
of Lancaster Gap mine in 1882 was 11,653 pounds.

Besides the metals already described, there are several
others which are of considerable economic interest,
whether from the valuable properties that they impart to
certain alloys, like antimony and bismuth ; or from their
adaptation to certain special uses, like magnesium and alu-
minium, which last metal awaits only cheaper processes
of extraction to be largely used ; or from the large use of
some of their compounds in the arts, like manganese,
chromium, and arsenic.

Antimony has already been mentioned as a common
mineralizing agent in ores of silver ; but the usual source
of the metal is the sulphide stibnite, a soft, lead-gray, and
easily fusible mineral, occurring in rhombic prisms of easy
cleavage, or in radiating needles, as also massive ; and
readily distinguished by these characters as well as by be-
ing dissipated into a white vapor with an odor of sulphur
before the blow-pipe on charcoal. It occurs most com-
monly in veins in crystalline rocks, and the largest depos-
its yet found in the United States are those near Battle
Mountain in the Humboldt region of Nevada, and in
Kern County, Cal. These deposits are said to be of
great importance, and have been worked to some extent,
though difficulties arising from distance from markets
and from easy transportation have not hitherto made

PLATINUM AND OTHER METALS. 289

their exploitation profitable. Besides these, promising de-
posits are reported to exist in Sevier County, Ark. Valu-
able foreign sources of supply occur in Germany, Hun-
gary, France, Spain, Borneo, and in New South Wales.
From its ready fusibility, the ore is easily separated from
its gangue by heat. It is used in alloys, as type and stereo-
type metal, and in britannia ; and some of its compounds
are used in medicine, in orange and yellow pigments, and
in pyrotechny for Bengal fire.

Bismuth occurs native, associated often with ores of
cobalt and silver in veins inclosed in crystalline rocks, as
also in the form of a sulphide called bismuthinite, and as an
impure oxide called bismuth ochre. The chief supplies are
derived from Schneeberg, Saxony, the German product of
1 88 1 being reported as fifty-six metric tons; from Bolivia,
the value of whose product for the same year is reported
at $61,189; and from South Australia. Deposits of some
importance are said also to exist in Utah, in Boulder and
La Plata Counties, Col., and near Golden, in the same
State. Its uses are somewhat limited, being chiefly in
compounding fusible alloys, soft solder, and britannia;
in the preparation of pearl-powder, and of mordants for
calico-printing, and in coloring glass and porcelain.

Magnesium is very widely diffused as a constituent
of several common rock-forming minerals ; but the sources
whence the metal is obtained are the mineral carnallite, a
double chloride of magnesium and potassium occurring
associated with the salt deposits of Stassfurt in Germany,
and magnesite, a magnesian carbonate which is associated
with serpentine, and which to obtain the metal is con-
verted to a double chloride of magnesium and sodium by
dissolving in hydrochloric acid and adding a solution of
common salt. The metal is obtained from either of these
double chlorides by fusing with metallic sodium and fluor-
spar. It is rolled into thin ribbons or made into wire, and
in this form burned in a proper lamp, giving a light of ex-

290 APPLIED GEOLOGY.

ceeding brilliancy for use in signaling. It is also used in
filings for pyrotechny.

Aluminium is a recent addition to the list of metals,
but its remarkable characters promise to render it highly
useful in the arts as soon as processes shall be devised by
which it may be liberated from its combinations within
reasonable limits of cost. It is a white metal of singular
lightness, its specific gravity being only about one third
that of iron ; it is malleable and very tenacious, and unal-
terable by atmospheric agencies ; and its alloy with copper,
called aluminium bronze, is of a golden yellow color, very
hard and malleable, and of a tensile strength which is said
to be greater than that of Bessemer steel. The compounds
of this metal with silica are some of the most widely dis-
tributed constituents of rocks, and kaolin, the essential
constituent of clays, is a hydrous silicate of alumina ; but
it has not yet been found practicable to obtain the metal
from its silicated compounds. The sources from which it
is obtained are bauxite, a hydrous oxide of aluminium
and iron containing but a trifling amount of silica, found
abundantly in France, and cryolite, a double fluoride of
aluminium and sodium, which is brought from Greenland.
Bauxite is first converted into a chloride of sodium and
aluminium, and then the latter compound is fused with
metallic sodium and a flux, thus liberating the metal ;
while cryolite can be fused direct with sodium. A process
is said recently to have been devised in Philadelphia by
which the reduction of the metal will be very greatly
cheapened by dispensing with the use of sodium, and re-
ducing the cost of preparing the aluminium compound ;
and, if it proves successful, this interesting metal will soon
be largely used in the fabrication of engineering and other
instruments, and for various other purposes where strength
combined with lightness is desirable. The French pro-
duction of aluminium in 1882 was 2,349 kilogrammes.*
* While this work is going through the press, it is announced that

PLATINUM AND OTHER METALS. 291

Chromium. — This metal is of little economic impor-
tance as a metal, having merely a limited application in the
manufacture of what is called chrome-steel ; but its brill-
iant colored compounds are largely used in the arts as pig-
ments and in calico-printing ; and they have also a limited
use in galvanic batteries. The source whence it is derived
is the mineral chromite, or chromic iron, a hard, black,
feebly magnetic compound of chromium and iron oxides,
which contains when pure about 68 per cent of chromic
sesquioxide, but rarely has more than 60 per cent. This
mineral occurs usually in beds or veins of serpentine in
crystalline rocks, as along the eastern base of the Appa-
lachians, and in the Coast Range of California, at favor-
able localities in which it is found in great abundance.
It was formerly derived wholly from Wood's Mine, Lan-
caster County, Pa., and the adjacent parts of Maryland
not far from Baltimore. Lancaster County is said to
have yielded ninety-five thousand tons of the ore, aver-
aging 48 per cent of the oxide. The supplies from these
localities are said to be now mostly superseded by the
richer ores of California, which are drawn most largely
from mines in San Luis Obispo County, and from Placer
County near Auburn, rich deposits being also known to
exist in several other counties. By appropriate treatment,
this ore is converted into bichromate of potash, the basis
of all chrome pigments.

Manganese. — The direct uses of this metal are in
alloys with iron, called spiegeleisen, or ferro-manganese,
according to the percentage of manganese which they
contain, and which are largely used in the manufacture of
steel ; and in an alloy with copper called manganese
bronze, which from its hardness is well fitted for bearings
in heavy machinery. The iron alloys are obtained by
smelting manganiferous ores of iron, procured mostly

Messrs. E. H. and A. H.Cowles, of Cleveland, O., have perfected a process
by which the manufacture of aluminium bronze will be much cheapened.

292 APPLIED GEOLOGY.

from Germany and southern Spain, the American ores be-
ing too commonly contaminated with phosphorus to be
used for this purpose. Several native compounds occur in
considerable abundance, chiefly oxides, which are black,
a rose-red carbonate, and a lighter red silicate; but that
which is most used in the arts is pyrolusite, a tolerably soft
black dioxide of manganese (MnO2), whose impure mix-
ture with iron oxide, called wad, is also employed for some
of its uses. These oxides are found in the Atlantic
States from Maryland to Georgia, the purest being ob-
tained from Bartow County, Ga., and the Virginia de-
posits being next in value, Augusta County yielding fully
one half of the product of Virginia, from a single mine.
Promising deposits occur also on the Pacific coast, the one
best known being on an island in the Bay of San Fran-
cisco. Deposits of this mineral should contain at least 60
per cent of the oxide to justify their exploitation. Pyro-
lusite is largely employed in the arts for the liberation of
chlorine and the manufacture of bleaching-powder, in the
preparation of varnish and " boiled oil," and in glass-
making to discharge the green tints which iron imparts.
It is also used in glazing and painting pottery, and in glass-
staining, and to some extent with potassium chlorate in
making oxygen. The permanganate of potash has like-
wise a large use as a disinfectant.

Arsenic. — This metal, so widely known by reason of
the deadly nature of all its compounds, is but little used in
the metallic state. It enters into a few alloys, the chief of
which is with lead to give it greater hardness in the manu-
facture of shot. Its compounds are, however, considerably
used for various purposes. The yellow sulphide, called
orpiment, or king's yellow, the red sulphide realgar, and
the arsenite of copper, called Scheele's green, are used as
pigments, realgar being also used in pyrotechny and for
signaling purposes as an ingredient in "white Indian
fire " ; the oxide is used in glass-making and for the pres-

PLATINUM AND OTHER METALS. 293

ervation of natural history specimens ; and some of the
compounds enter into pharmaceutical preparations. Ar-
senic occurs in the crystalline rocks, forming important
ores with silver, nickel, and cobalt ; and its compound
with sulphur and iron called mispickel, or arsenical iron
pyrites, a hard, silver-white, and brittle mineral which
yields an odor like garlic when heated, is found abun-
dantly in many places associated with ores of silver, cop-
per, and other metals, as at Freiberg, and with ores of tin,
as in Cornwall. From this last mineral chiefly, and from
the ores of nickel and cobalt, it is obtained for commer-
cial purposes in the form of the well-known white arsenic,
by roasting the ores and condensing the arsenic in cham-
bers and flues. It is made mostly in Germany, and in
Cornwall and Devon. The ores from which it is obtained
exist also in sufficient abundance at various points in re-
gions of crystalline rocks in the United States.

Iridium, which is found sparingly associated with plat-
inum, has a limited but important use, based on its ex-
treme hardness, in wire draw-plates and knife-edges for
balances, in the nibs of gold and stylographic pens, and in
the contact-points of telegraph instruments. It is said,
also, to be used somewhat in porcelain-painting to give a
black color. Its chief source is iridosmine^ an alloy of
iridium with osmium and one or more other rare metals
of the same class, which is found not only in the Urals,
but also in the gold placers of California and Oregon,
where its weight, which equals that of gold, renders it easy
to be recovered, so that this region now yields important
supplies. The value of pure iridium is nearly that of gold,
the iridosmine selling at from twenty-five to sixty dollars
per pound troy, according to the percentage of the metal
which it contains.

Besides these metals, a few others, whose ores are of
somewhat unfrequent occurrence, but which are utilized
in the arts for special purposes, deserve brief mention here.

294 APPLIED GEOLOGY.

Molybdenum, in the form of molybdenite, a mineral which
resembles graphite, but is easily distinguished from it by
yielding sulphur by heat, has been found at several locali-
ties in the Eastern States, and is said to occur in some
abundance in Gunnison County, Col., and in Utah. It is
used to give a blue color to pottery. Uranium, also used
in porcelain-painting for yellow and black colors, has been
found as the mineral pitchblende at the Wood mine near
Central City, Col., and also near Denver. Its chief sup-
plies are, however, derived from Bohemia. Tungsten is
obtained from wolfram, a compound of tungsten, iron, and
manganese, found as a somewhat frequent associate of the
tin-ores of Cornwall and of Saxony. It has been found
in small quantities in Maine, Connecticut, North Carolina,
Missouri, and Nevada, and is quite likely to be met with
in the tin region of the Black Hills. Tungsten has in re-
cent years come into use for making a special grade of
steel, which is of extreme hardness without being very
brittle, and which is therefore adapted to the manufacture
of tools for turning and planing iron. Some of its soluble
compounds are used to a small extent in calico-printing,
and other compounds are of excellent promise as valuable
pigments.

In this necessarily condensed treatment of the metals,
their mineralogical and geological mode of occurrence, the
regions where they are most largely obtained, and their
leading uses, no attempt has been made to do more than
to give the student such information as may serve as a
guide to his active efforts or to his more extended re-
searches in special directions. It is hoped that it may
also prove helpful to the practical man, not only by indi-
cating the most promising sources of materials for his
technical pursuits, but also by pointing him to regions
whence he may look for the most effective competition in
his business. To these ends the leading foreign deposits
have been noted, as well as those which are found in our

PLATINUM AND OTHER METALS. 295

own country; and the extent and importance of both
sources of supply and competition have been suggested by
the tables of production, which have been compiled from
the latest statistics and estimates that have come to hand
in Government reports and technical journals. A number
of rare metals have been entirely omitted, while the metals
of the alkalies and alkaline earths, which, with a single
exception, have no technical use as metals, will be treated
in their appropriate place under their most important
native compounds.

CHAPTER XVIII.

SUBSTANCES ADAPTED TO CHEMICAL MANUFACTURES OR

USE.

THE earth's crust affords a considerable number of
substances whose applications are chiefly of a chemical
character, or which form the basis of extensive chemical
manufactures before they attain the varied forms in which
they may most completely supply human wants. Some
few of the substances which may most conveniently be dis-
cussed under this head, besides their chemical applications,
have also direct uses in their native condition, like salt
and sulphur ; some, like the fluxes, are used either to re-
move unwelcome ingredients in the form of a liquid slag
in metallurgical operations, or to give a fine exterior finish
to pottery ; while some, like pyrites and niter, may furnish
the initiative to series of chemical operations resulting in
a number of useful products. It may also with propriety
be stated here, once for all, that some mineral substances
are of varied utility, and might with equal fitness be con-
sidered under any one of two or more different classes of
applications. Such substances will receive whatever gen-
eral discussion may seem desirable in the first class in
which they may occur ; and any subsequent mention of
them will imply an acquaintance with their previous treat-
ment.

Pyrites. — Pyrites, so called from the Greek word for
firey because its hardness is such as to enable it to strike

SUBSTANCES FOR CHEMICAL PURPOSES. 297

fire with steel, is a sulphide of iron, FeS2, containing, when
pure, 53.3 per cent of sulphur. It is found frequently in
cubic crystals of a light yellow color and brilliant metallic
luster, gives a black streak on porcelain, is very hard
though brittle, and emits when heated the odor of sulphur,
yielding finally a black magnetic globule. Although a
compound of iron, it was not described among the ores of
iron, because it is not directly used as a source of that
metal, though the residues from its treatment for chemical
purposes are in recent years coming into use for making
certain grades of iron and steel. Pyrites, in small quanti-
ties, is very widely disseminated in rocks of all ages, and,
by the readiness with which it oxidizes when exposed to
the weather, it constitutes one of the most active agents
in their decay ; but, to be of any economic importance, it
needs to occur in deposits of great dimensions, and rea-
sonably free from admixture with other minerals save
chalcopyrite, with which it is usually associated.

The workable deposits of pyrites occur in great beds,
swelling out often to dimensions so vast as to be consid-
ered mass deposits, and intercalated mostly in crystalline
schists, which in this country at least seem to be of Ar-
chaean age. Deposits of this kind are found along the
eastern slope of the Appalachians from eastern Alabama
to New Hampshire and Maine. Along this range mines
have been opened at Capelton in the Eastern Townships
of Quebec, at Milan in New Hampshire, Stafford in Ver-
mont, Rowe in Massachusetts, and at Tolersville in Lou-
isa County, Va. From the Canadian locality about forty
thousand tons are sent yearly to the United States. The
deposits at Milan, which have been proved for more than
nine hundred feet in length, are from eight to more than
forty feet thick ; and those of Tolersville, according to a
recent account, are capable of yielding easily one thousand
tons daily. The pyrites from all these localities contains
valuable amounts of copper, and all are claimed to be re-

298 APPLIED GEOLOGY.

markably free from arsenic, a deleterious ingredient which
is rarely entirely absent from pyrites deposits, and whose
presence in any considerable proportions seriously im-
pairs the value of the mineral for some of its foremost uses.
Besides these deposits, which are favorably situated with
regard to transportation, others of the greatest promise
are known to exist within the Appalachian region which
are still untouched from lack of a market. The State geolo-
gist of Alabama reports extensive deposits of cupriferous
pyrites in Clay County ; and, according to C. R. Boyd, in
the western part of Carroll County, Va., occurs a body of
pyrites in talcose schists, which has an average length of
ten miles with an average width of thirty-three feet, and
which contains an average of two and a half per cent of
copper and 45 per cent of sulphur.

Large as are our American deposits of pyrites, they
sink into comparative insignificance in comparison with
some of the enormous masses which are found in Sweden,
Spain, and Germany. The greatest of these are the de-
posits of Rio Tinto in southwestern Spain, extending west
into Portugal. Here are worked two vast beds or veins in
highly disturbed and metamorphosed schists, associated
with quartz porphyry, which are thought to be of Per-
mian age. The southern vein, which is from three hun-
dred to four hundred feet in width, is opened for sixteen
hundred feet of its length, and is known to be at least
twenty-five hundred feet in length, while the northern
vein is much more enormous, being fully six thousand
feet long, and swelling in places to a width of from thir-
teen hundred to sixteen hundred feet. The pyrites from
these immense deposits contains highly important amounts
of copper, a recent analysis of the export material showing
3.69 per cent of copper, with 47.76 per cent of sulphur,
but contaminated by nearly one per cent of arsenic. The
Spanish output of pyrites in 1881 was nearly a million and
a half tons, and it has greatly increased since that date ;

SUBSTANCES FOR CHEMICAL PURPOSES. 299

and the large amount of copper directly and incidentally
derived from these deposits is a highly important factor in
determining the present low prices of that metal.

At Goslar, in the Harz Mountains, in a region of De-
vonian limestone and slate, occurs an enormous mass de-
posit of cupriferous pyrites, which, as described by Von
Cotta, has a known length of eighteen hundred feet, with
a width of three hundred and fifty feet, and sends a con-
siderable branch into the hanging wall, showing that it
can not be considered a bed, although in other respects its
position is conformable with the stratification of the in-
closing rocks. The pyrites of this deposit contains
arsenic and lead, with small amounts of several other
metals. The German output of pyrites in 1883 was
148,700 metric tons.

At Fahlun, in Sweden, a great irregular mass deposit
of copper-bearing pyrites, with numerous outliers, is met
with in schists and gneiss of Archaean age. Portions of
this deposit contain also lead and zinc. Also at Agordo,
in the Tyrolese Alps, occurs a considerable mass deposit
of pyrites, varying in width from twelve to two hundred
and fifty feet, in a country rock of talcose and clay slate,
with the bedding of which it conforms.

Uses of Pyrites. — The foremost use of pyrites is as
a cheap source of sulphur in the manufacture of sulphuric
acid, and it has within the past twenty-five years rapidly
replaced native sulphur in this very important industry.
For this purpose, the pyrites is burned in properly con-
structed combustion-chambers, the sulphur being elimi-
nated in the form of sulphurous acid ; and it is said that
some of the arrangements for this purpose are so effective
as to leave less than one per cent of sulphur in the iron of
the residue. After burning, the copper in the pyrites is
extracted by a leaching process, and the residual some-
what sulphurous iron oxide can then be used as a source
of certain grades of iron, and for some other purposes.

3oo APPLIED GEOLOGY.

The characters which best adapt pyrites for the use of
acid manufacturers are the following: (i) A high per-
centage of sulphur. As has already been stated, absolute-
ly pure pyrites contains about 53 per cent of sulphur ;
but most of the mineral in commercial quantities holds
varying amounts of quartz and other substances, which
diminish the percentage of sulphur by so much. The
Spanish pyrites contains, according to the analysis al-
luded to above, about 2^ per cent of silica and lime, and
a little less than 48 per cent of sulphur. It has recently
been stated that pyrites capable of yielding 45 per cent of
sulphur is worth about seven dollars per ton for acid-
making. (2) Freedom from arsenic, antimony, and lead,
the first of which substances unfits the acid containing it
for many of its uses, while the second and third promote
the fusion of the pyrites while burning, and so hinder the
complete elimination of its sulphur. Arsenic, while es-
pecially common in pyrites, is also especially objection-
able, and, in the foregoing account of the great deposits,
its presence or absence where known has been mentioned
for this reason. (3) Readiness to part with the contained
sulphur, in which different lots of pyrites show consider-
able differences ; partly in consequence of the physical
condition of the mineral, that which is more granular and
porous presenting a larger surface for the combustion of
the sulphur ; partly from differences of fusibility, arising
from the presence or absence of minerals that are liable
to act as fluxes at the temperature which is employed ;
partly, also, from the presence of sulphur compounds
which retain their sulphur with considerable tenacity, like
copper, the presence of which, while adding to the selling
value of the pyrites in one direction, diminishes, to a
certain extent, its value to the acid-maker as a source of
sulphur, since it prevents its complete elimination. (4) It
is desirable that pyrites for acid-making should not have
a tendency to crumble readily in mining and handling,

SUBSTANCES FOR CHEMICAL PURPOSES. 301

since this produces a great amount of " fines," rendering
necessary special arrangements for its burning. (5) Py-
rites sometimes contains water mechanically inclosed, ren-
dering it liable to decrepitate violently while burning —
a troublesome character, which detracts from its value.
(6) As was suggested above, the presence of a consider-
able proportion of copper adds much to the value of py-
rites, since it becomes a source of copper as well as of
sulphur. The copper is paid for, on analysis, in addition
to the obtainable sulphur ; or else, in some cases, the resi-
dues, after burning, are returned to the seller. It can
hardly be expected that all these desirable characters will
concur in every lot of pyrites that is worth extracting.
That will be the best which has the greatest number of
excellences, and those most essential. With a careful ex-
amination of fair average samples of pyrites as regards
these requisites, the probable value of any great body of
pyrites well located for cheap transportation to markets
can be closely approximated. The extent and impor-
tance of the chemical industries to which pyrites furnishes
the initiative can not be better stated than by quoting
from the "Geology of Canada," 1863, p. 746 : "In order
to give some idea of the great importance of iron pyrites
and of its products in a manufacturing point of view, it
must be said that sulphuric acid, which is now for the
most part manufactured from pyrites, is the agent used
for decomposing common salt for the manufacture of
soda in its various forms of soda-ash, carbonate of soda,
and caustic soda. From this decomposition is also ob-
tained hydrochloric acid ; this is used in the manufacture
of chlorine, and of bleaching-powder or chloride of lime,
which are indispensable in the bleaching of cotton, linen,
and of the materials for paper. Besides this, the manu-
factures of soap and glass, and many other chemical prod-
ucts, are dependent upon the soda thus obtained. The

sulphuric acid is also used for the manufacture of nitric
14

302 APPLIED GEOLOGY.

acid, of superphosphate of lime, of alum, and many other
products, all of which are generally manufactured in the
vicinity of sulphuric acid and alkali works."

Besides its use in the manufacture of sulphuric acid,
pyrites is largely utilized in making iron sulphate or cop-
peras, to be employed in dyeing fabrics black and as a
disinfectant. Incidental to this process, sulphur is some-
times extracted for the market from the pyrites, by heat-
ing the mineral in retorts to drive off about one third of
the sulphur, which is condensed. The pyrites, partially
roasted in this way or merely in heaps, or quite as fre-
quently without preliminary roasting, is piled on tight
floors under a shed-cover, moistened with water, and left
to the action of the atmosphere, by the agency of which it
is oxidized to iron sulphate ; this is then leached out with
water, and the solution, properly concentrated by boiling,
is left to deposit the copperas in crystals.

Sulphur. — As will already have been observed in the
preceding chapters, the compounds of sulphur with the
metals constitute a highly important and widely diffused
class of metallic ores called sulphides or sulphurets, and
from some of these a part of the sulphur can be obtained
by a process of distillation, as in the case of iron pyrites.
As a commercial article, however, it is more largely ob-
tained from deposits in gypsum, bituminous marl, and
limestone, or from volcanic regions, where it is found un-
combined, filling fissures and cavities, and mingled usually
with varying amounts of earthy substances, from which it
is easily separated by melting in large kettles ; the sulphur
melts at a temperature a little above that of boiling water,
the impurities settle to the bottom or are skimmed out,
and the sulphur, in a tolerably pure condition, is then
ladled out into molds. A simpler mode of separation is by
setting fire to the sulphurous earth in heaps or kilns, when
the heat generated by the combustion of a portion of the
sulphur melts the rest, which flows off and is caught ; or it

SUBSTANCES FOR CHEMICAL PURPOSES. 303

can be obtained much purer by distilling off the sulphur
from the earthy mass in iron or earthenware retorts. The
source of the sulphur in these deposits is doubtless from
the decomposition of earthy or metallic sulphides and
sulphates, in some cases possibly by heat, but in most by
the agency of water and oxygen or organic matter, giving
rise to sulphur springs which deposit their sulphur by
the action of atmospheric oxygen. The largest supplies
of sulphur, for both Europe and the United States, are
derived from Sicily, where the deposits are found in foli-
ated gypsum, bituminous marls, and limestones of Tertiary
age. These deposits contain from 20 to 40 per cent of
sulphur, of which they yield somewhat more than half to
the usual processes of extraction. The United States
imported in 1880 more than 100,000 tons of sulphur, nearly
all from Sicily, and it is said that Europe derives nearly
nine tenths of its sulphur from the same region. Impor-
tant deposits also occur in Italy and Poland. Iceland
contains rich but undeveloped deposits of sulphur, and it
is found in most volcanic regions. In the United States,
sulphur has hitherto been obtained from native deposits
only in California and Nevada, though deposits of great
promise are known to exist at Cove Creek in western
Utah, in New Mexico, in the Yellowstone region, and
near Evanston, in Wyoming. The deposits of Cove
Creek, and those of Rabbit Hole in northwestern Nevada,
are said to be in regions of comparatively recent volcanic
activity, occupying in the first case the sites of not yet
extinct solfataras, and either filling fissures in the rocks
or impregnating and cementing tufas.

Sulphur has several important and extensive uses, fore-
most among which is its employment in the manufacture
of sulphuric acid. Until within a very few years, all the
acid made in this country was manufactured from sulphur,
chiefly Sicilian ; and although it is now being slowly su-
perseded for this purpose by pyrites, on account of the

304 APPLIED GEOLOGY.

greater cheapness of the latter substance, still, for many
uses where perfect freedom from arsenic is required, acid
made from sulphur is sure to be preferred. Some of our
Western sulphur deposits, however, are said not to be
wholly free from arsenic, a fact which indicates that such
deposits were derived from sublimation in which case
arsenic from its volatility would accompany sulphur, rather
than from elimination from the water of sulphur springs.
Other large uses of sulphur are in the making of gun-
powder, in the manufacture of matches, for which its ready
inflammability adapts it, in the vulcanizing of rubber and
gutta-percha, in bleaching straw and woolen goods, and
as a cementing material between iron and stone. It is
used in the manufacture of vermilion, an artificial sul-
phide of mercury ; of mosaic gold or bronze powder, a
bisulphide of tin, and of several other useful compounds ;
has some important pharmaceutical applications, and the
sulphurous-acid gas generated by its combustion is a very
valuable disinfectant.

Salt. — This useful and indeed indispensable substance
occurs in nature in two states — either (i) in solution, as
in the waters of the ocean, and of salt lakes and ponds, or
in those of salt springs and wells, the waters of which de-
rive their salt from subterraneous masses, or from perco-
lating through clays and marls in which salt is dissemi-
nated ; or (2) in irregular beds and masses of rock-salt,
which are sometimes of enormous dimensions, and from
which the salt is obtained by regular mining operations.
From whichever source derived, salt, which, as is generally
known, is a chloride of sodium, is never absolutely pure,
but holds variable amounts of sulphates of lime, magnesia,
and soda, chlorides of calcium and magnesium and some-
times of potassium, with usually a little iron carbonate,
and often, in the case of rock-salt, some finely disseminated
clay. The salt of this country has hitherto been derived
almost entirely from the evaporation of natural brines,

SUBSTANCES FOR CHEMICAL PURPOSES. 305

like those of Syracuse, N. Y., and of the region around
Saginaw Bay, Mich., by solar or artificial heat ; or from
the solar evaporation of sea-water in salt-pits at favor-
able points, as in California ; while a very considerable
portion of the European supply has for ages been drawn
from beds of rock-salt, the famous mines of Wieliczka,
near Cracow, in Polish Austria, having, it is said, been
worked since the eleventh century.

A pure saturated brine contains at ordinary tempera-
tures about 25.7 per cent of salt, and the strength of
brines is usually tested by an instrument called a salome-
ter, an areometer graduated from o°, the point to which it
sinks in pure water, to 100° for the point at which it stands
in a pure saturated brine. A degree of the salometer
answers, therefore, to about one fourth per cent of salt in a
pure solution ; while a degree of the ordinary hydrometer
of Beaume corresponds very nearly to i per cent of salt,
if the brine is pure. Sea-water contains 2.6 per cent of
salt, and nearly i per cent more of other saline ingredi-
ents ; the brines of Syracuse hold from 14 to about 18 per
cent of salt ; those of Michigan, from 15 to nearly 20 per
cent ; those of Goderich, Ontario, from 20 to 24 per cent ;
and the weaker brines of West Virginia and Ohio, about
10 per cent.

Beds or deposits of rock-salt occur associated with
beds of gypsum, marls, and clays, and sometimes, as at
Goderich, of porous dolomites. They have in all proba-
bility originated from the desiccation of salt lakes, or of
sea-borders cut off from the main body of water by bar-
riers which were occasionally overleaped by the outside
waters, thus adding new supplies to be concentrated by
evaporation. In the process of concentration such waters
would naturally first deposit their least soluble ingredient,
gypsum or anhydrite, which is always present in sea-water,
and afterward, with increasing concentration, their salt ;
while earthy substances, washed from the adjacent lands,

3o6 APPLIED GEOLOGY.

furnished the solid impurities and the materials for the
interstratified beds of marls and clays. Every fresh influx
of sea-water will give occasion for a new deposition of gyp-
sum to be interlaminated with the salt ; while the more
soluble sulphates and chlorides of magnesium and potash
become greater in amount in closed basins, like that of
the Dead Sea at present, and may ultimately, under fa-
vorable circumstances, on the final drying up of the area,
form deposits of carnallite, sylvite, kainite, etc., like those
of Stassfurt in Germany, and in the eastern Carpathians,
which will be mentioned in subsequent sections. Some of
the deposits of salt thus formed are of vast dimensions.
Probably the most amazing yet known is that at Speren-
berg, south of the city of Berlin, which, according to Roth
and Credner, has been explored by boring nearly four
thousand feet without penetrating to its base. That of
Wieliczka is said to be in places not less than fourteen
hundred metres thick.

Salt deposits are by no means limited to any special
members of the geological series. On the contrary, they
are found in rocks of various geological ages, from the
Upper Silurian to the present time. Yet, aside from the
deposits which are now accumulating in closed basins and
lagoons, there are recognized on both continents geological
horizons which are especially rich in salt. Thus, in North
America, a group of Upper Silurian rocks has been appro-
priately called the Salina, because of its salt-bearing char-
acter ; along it are ranged the great salt-works of Syracuse,
the two recently discovered salt-beds of Wyoming County,
thirty and seventy-five feet thick, from which a nearly
saturated brine is drawn, and the deposits around Go-
derich, on Lake Huron, consisting of six salt-beds of an
aggregate thickness of one hundred and twenty-six feet,
some of which are of unusual purity, besides salt-wells at
many other points, the brine of which is not strong enough
to be worked with profit under the existing conditions of

SUBSTANCES FOR CHEMICAL PURPOSES. 307

production. A second profitable salt horizon is that of
the Lower Carboniferous up to the base of the coal-meas-
ures, which yields the brines of the Saginaw region in
Michigan, and those of Ohio and West Virginia near the
Ohio River. The great mass of extraordinarily pure salt
at Petit Anse in Vermilion Bay, southern Louisiana, which
has been explored to the depth of one hundred and sixty-
five feet without reaching the bottom, is said by Hilgard
to be of probable Cretaceous age. In Europe the Triassic
is often called the Saliferous system, on account of the rich
deposits of rock-salt that occur in it at several different
horizons ; in England, at Northwich in Cheshire, and in
Germany at Vic and Dieuze in Lorraine, on the upper
Neckar in Wiirtemberg, and at a number of other points.
Yet the rocks of the Permian period might with nearly
equal propriety be counted a saliferous system, since in
them occur the enormous deposits of Stassfurt and Speren-
berg, which have already been mentioned, as well as those
of the government of Perm in eastern Russia, and those of
the Kirghiz Steppe near the Caspian Sea ; while in the
Tertiary are found the celebrated deposits of Wieliczka,
and those occurring along both sides of the Carpathians
to Wallachia and Transylvania ; as also, quite probably,
those of Cardona, in the Pyrenees of northeast Spain,
which are thought by some to belong to the Cretaceous
period.

Besides the chief salt-producing centers in the United
States that have been mentioned above, the great Western
region, extending from the Rocky Mountains to the Pacific
coast, is abundantly supplied with salt at many points,
from salt lakes, pools, and marshes, and surface incrusta-
tions overlaying beds of salt of unknown depth, and which
occupy apparently the sites of ancient salt lakes long since
dried up. Nevada, in particular, abounds in salt deposits
of these various kinds. Near Columbus, Esmeralda Coun-
ty, a salt-field of nearly fifty square miles is found ; on the

3o8 APPLIED GEOLOGY.

Rio Virgen, in Lincoln County, are said to occur enormous
masses of rock-salt with an outcrop of not less than twenty-
five miles ; and several other counties have supplies almost
equally abundant, while every State and Territory in this
region may draw sufficient supplies of this needful sub-
stance from sources existing within its own limits.

In 1882 the United States produced 801,547 gross tons
of salt, of which 71 per cent was furnished by the Saginaw
region and Syracuse; about 18 per cent more by West
Virginia and Ohio, in nearly equal proportions, while most
of the residue was derived from California, Pennsylvania,
Utah, Virginia, Louisiana, and Nevada. In the same year
the reported product of Great Britain was 2,135,499 gross
tons, and that of Germany 322,422 metric tons of rock-salt,
her production from salt-works in 1881 having also been
456,958 tons. The product of Russia in 1874 was 769,000
tons, 54,630 tons of which was rock-salt ; and that of Aus-
tria, for the same year, was 249,521 tons, of which 81,081
tons was rock-salt.

The largest use to which salt is applied is doubtless for
household purposes, in the seasoning of food and the pres-
ervation of provisions. This use among civilized nations
is everywhere large, varying with the habits of the people
from about ten to more than thirty pounds per capita. It
is estimated that the people of the United States consume
in this way about thirty-two pounds per person ; and, if this
estimate is correct, our production, large as it is, is mostly
consumed for this single use. Another large use of salt
is in chemical manufactures, as a source of soda by the
Leblanc process, or by the recently devised ammonia pro-
cess ; as a source of hydrochloric acid incidental to the
Leblanc process ; and, directly or indirectly, for the lib-
eration of chlorine in the manufacture of chloride of lime,
to be used for bleaching purposes and as a disinfectant.
Large amounts are used, also, in the metallurgy of silver,
as a chloridizing agent preparatory to amalgamation ; in

SUBSTANCES FOR CHEMICAL PURPOSES.

309

the manufacture of pottery as a glaze ; and as a fertilizer
in agriculture.

For additional information on the occurrence of salt, and the mode
of extraction from brines, the student is referred to " Natural History
of New York," Beck's " Mineralogy " ; " Geological Report of Michi-
gan," Vol. Ill ; T. Sterry Hunt's articles on salt in the " Geological
Survey Reports of Canada " for 1866, 1866-1869, and i876-'77 ; " Min-
eral Resources of the United States," 1883 ; Credner, " Geologic," pp.
45 and 291 ; Hoffman, "Chemische Industrie," and Ure's "Diction-
ary of Arts," etc.

Alkalies from Geological Sources. — The ultimate
source of the alkalies potash and soda, save such portions as
may always have been present in oceanic waters, is doubt-
less to be found in the decomposition of the rock-forming
minerals which contain them, chiefly feldspars and micas.
From these they have passed partly into soils, from which
they are withdrawn by plants in the processes of growth ;
and a very important portion of the potash of commerce
is still obtained from leaching the ashes of plants and
evaporating the solution. Still larger portions of these
soluble substances have been carried into great bodies of
water, like the ocean and inland seas and lakes ; and, on
the final desiccation of isolated bodies of such waters, have
formed deposits of salts of potash, soda, and magnesia
overlying salt-beds, as at Stassfurt, Kaluscz in eastern
Hungary, and Maman in Persia ; or, in arid regions, like
those of northern Chili and adjacent Peru, and portions of
our great Western basin region, have formed extensive
alkali flats impregnated with carbonates, sulphates, and
sometimes nitrates of soda, occupying the sites of former
inland seas, portions of which in some cases still remain,
forming lakelets of intensely alkaline water.

Of the potash salts, the nitrate, called niter or salt-
peter, is spontaneously generated in the soil of a number
of hot regions like India, Persia, Arabia, and Egypt, doubt-
less by the action of organic matter on the debris of feld-

310 APPLIED GEOLOGY.

spathic rocks ; as also on the earth floors of some caves in
our Western States. India formerly yielded the largest
supplies ; but, during recent years, a chief source of the
salts of potash has been the vast deposits overlying the
beds of rock-salt near Stassfurt in Germany. Here a
series of beds, several hundred feet in thickness, is made
up of alternating layers of rock-salt and hydrous sulphates
and chlorides of potash, soda, magnesia, and lime, called
kainite, carnallite, sylvite, kieserite, and polyhalite. These
are largely extracted and sent into commerce. Sylvite,
which is the chloride of potassium, is readily converted
into saltpeter by the agency of soda nitrate, yielding ni-
trate of potash and common salt. In 1882 Germany
produced 141,272 metric tons of kainite, which is a com-
plex compound of potassium and magnesium sulphate,
magnesium chloride, and water, and 1,063,592 metric tons
of other potash compounds. These are utilized as ferti-
lizers, and in the manufacture of the various valuable com-
pounds of potash. The occurrence of these desirable de-
posits of potash minerals, in connection with the upper
beds of salt deposits in several foreign localities, suggests
the expediency of a careful examination of what overlies
any beds of rock-salt that may be found in our own coun-
try, to see whether similar sources of potash and magnesia
may not possibly be discovered here. The numerous uses
of potash compounds, in the manufacture of gunpowder,
matches, soap, glass, saleratus, alum, and nitric acid, in
photography and dyeing, in galvanic gilding and silvering,
and in medicine, are familiar to most persons. The Unit-
ed States imported in 1882 5,225 net tons of saltpeter,
which is said to have been obtained mostly from India.

As has already been said, in treating of pyrites and of
salt, the compounds of soda are very largely manufactured
from common salt. But, besides this, the nitrate, carbon-
ate, and sulphate of soda occur native in very important
deposits in several arid regions, where they occupy usu-

SUBSTANCES FOR CHEMICAL PURPOSES. 311

ally the dry basins of former bodies of saline waters, the
shrunken remnants of which sometimes remain as alkaline
pools and lakelets. Probably the most noteworthy of
these deposits are those of Chili and Peru, of Central
Asia, and of several portions of the great basin region in
the Western United States. The salinas of Chili and
Peru extend over several degrees of latitude in that rain-
less region, and in many places the soil is richly impreg-
nated to the depth of several feet with various salts of
soda, magnesia, and lime, of which the nitrate of soda,
often called Chili saltpeter, is a considerable constituent.
The nitrate, with some of the other more soluble sub-
stances, is leached from the soil, the solution evaporated,
and the crude salt exported, to be used as a fertilizer,
and in the manufacture of nitric and sulphuric acids and
nitrate of potash. Among the most notable of the nu-
merous saline deposits and lakes of the Great Basin, im-
pregnated more or less richly with the carbonate and sul-
phate of soda, and in some places with the nitrate, together
with common salt and compounds of magnesia, are, first
those of Humboldt County and Churchill County, Nev.,
in what is called the Forty-Mile Desert, the first of which
has valuable amounts of nitrate of soda, and the second,
in a depressed basin of several acres in area, is said to be
filled to the depth of ten feet or more with nearly pure
carbonate of soda divided into layers by thin seams of
clay ; second, those reported from San Bernardino County,
Cal., and the southern border of New Mexico, containing
nitrate of soda ; third, those of Carbon County, Wyo., where,
sixty-five miles north of Rawlins, a lake of three hundred
acres area is said to hold in solution about 10 per cent of
soda sulphate and carbonate, while a lakelet three and a
half acres in extent which receives its overflow is filled
with solid carbonate to more than six feet in depth, a
number of other soda lakes being also found about Inde-
pendence Rock in the same region ; and, fourth, the

312

APPLIED GEOLOGY.

soda lake at Morrison, near Denver, Col., the sulphate of
soda from which is said to be coming into use in Denver
for glass-making. It is highly probable that the thorough
examination of this vast region will reveal the presence of
many valuable deposits of the alkalies not at present
known. A recent geological reconnaissance of southern
central Oregon, made by Mr. J. C. Russell, the results of
which are published in the recently issued Fourth Report
of the Director of the United States Geological Survey,
has shown that the waters of two considerable lakes in
that region, Lakes Sumner and Abert, are " strong solu-
tions of potash and soda salts," an analysis of the water
of the last-named lake revealing the presence of two per
cent of potash compounds and a little salt, the origin of
which Mr. Russell attributes to the decomposition of the
feldspars in the surrounding volcanic rocks.

Besides the uses of soda compounds that have already
been incidentally mentioned, they are largely employed as
detergents in households and in bleaching establishments,
in the manufacture of hard soaps and of glass, in cookery
for raising bread and cake, in medicine and photography,
and in some metallurgical operations as a solvent of silver
salts.

Borax. — This substance, which is largely used in the
arts for several important purposes, is a biborate of soda,
which occurs native in several localities, and is also ob-
tained by treatment of native boracic acid, and of ulexite
or boronatrocalcite, a double borate of lime and soda,
found in rounded masses made up of white, silky radiating
fibers. These compounds, with some others of little com-
mercial importance, are found dissolved in the waters or
crystallized in the mud of the margins and bottoms of
closed and greatly shrunken saline lakes, or forming in-
crustations, mingled with other salts and earthy matters, in
marshes which are dry during a portion of the year ; or
issuing in the water of hot springs in a few volcanic dis-

SUBSTANCES FOR CHEMICAL PURPOSES. 313

tricts. For a long time it was brought to Europe in an
impure form called tincal> from Thibet, where it was found
in the borders of a saline lake, and the process of refining
was long kept secret by the Dutch and Venetians. Sup-
plies of tincal were also obtained from Nepaul, in India,
and from Ceylon. Later, it was made largely from the
boracic acid which issues with steam from the hot springs
of the lagoons of Tuscany. To these sources are now
added the rainless region of Chili, in the vicinity of
Iquique, where boronatrocalcite is found in large quanti-
ties, and the borax lakes and marshes of Nevada and Cali-
fornia. Large deposits of berates have also recently been
discovered near the Sea of Marmora in Asiatic Turkey.
The first locality in the United States where borax was
discovered was in a small saline lakelet,, very near Clear
Lake, in Lake County, Cal., where it occurred in crystals
enveloped in the gelatinous mud and underlying clay of
the bottom. Hot springs in the vicinity were also found
to contain boracic acid. For a number of years, a con-
siderable amount of borax was derived from this lake, but
it seems now to be superseded by richer or more acces-
sible localities. The largest amount of borax produced in
this country at present is derived from the borax marshes
near Columbus, in the southeast part of Esmeralda
County, Nev. It occurs here in extensive salines or
marshes, called Teel's Marsh, and Fish Lake, Columbus,
and Rhodes Marshes. These are all in oval alkaline flats,
occupying closed basins, which are dry during a portion
of the year, but in the wet season have shallow pools in
their lowest parts. The borax occurs forming incrusta-
tions mingled with salt, soda, and earthy substances, from
which it is freed by dissolving it with the aid of steam,
and then crystallizing it. A considerable amount of the
double borate of lime and soda is also found in these
marshes in the usual white fibrous balls. In 1882 nearly
half the borax produced in the United States was derived

APPLIED GEOLOGY.

from Teel's Marsh, a considerable quantity being also ob-
tained from Fish Lake Marsh. Similar borax deposits
occur in Slate Range Marsh, San Bernardino County,
Cal., from which a large amount of borax is obtained ;
and very promising deposits are reported also to occur in
Inyo County, about one hundred miles northward from
the last. The output of borax in the United States for
1884 was 3,500 tons of 2,000 pounds. The result of the
late discoveries of borax has been to reduce the wholesale
price to about thirteen cents per pound, which is not more
than two fifths of the price that formerly prevailed.

The largest uses of borax are based upon its property
of dissolving the oxides of many of the metals at a high
temperature, and forming with them a kind of glass,
which, in a number of cases, has characteristic colors.
Hence it is used as a flux in refining metals ; by iron and
steel workers in welding, to preserve the surfaces of the
metal clean from oxide during the operation ; by braziers
and jewelers in soldering ; by enamelers ; and by chem-
ists, as a most valuable reagent in blow-pipe operations.
It is an essential ingredient in all artificial gems ; is a
component of some varnishes and fine toilet soaps ; and
is said to enter into some kinds of glass. Considerable
amounts are also used as a detergent for household pur-
poses, by packers in preserving meats, and in some me-
dicinal applications.

The student will gain some additional information about borax
from " Mineral Resources of the United States " for 1867, p. 178,
which contains an account of the first discovery of borax in the Unit-
ed States, by the discoverer ; " Mineral Resources of the United
States," 1883 ; Ure's " Dictionary of Arts," etc. ; and Watt's " Dic-
tionary of Chemistry."

Alum. — This well-known substance is a hydrous dou-
ble sulphate of potash, soda, or ammonia, with alumina,
the base of clay. It is sparingly found native as an efflo-
rescence on rocks, where it originates from the weathering

SUBSTANCES FOR CHEMICAL PURPOSES.

315

of pyritous clays containing potash, but is more commonly
manufactured from pyritous shales, called alum-shales, or
from alunife, an insoluble sulphate of potash and alumina,
called commonly alum-stone. The latter occurs in rocks
of volcanic regions, where it probably originates from the
action of sulphurous vapors on feldspars containing pot-
ash. It is a somewhat rare substance, but is found in
quantities of commercial importance at Tolfa near Rome,
and at two or three localities in Hungary, where it forms
considerable beds. The mineral is carefully calcined to
avoid fusion and loss of sulphur, then kept moist in
heaps, and left to the action of the weather, by which it
is disintegrated, with the development of soluble alum.
This is leached out and crystallized, forming opaque
cubes ; and, under the name of Roman alum, derived
from the chief locality whence it is obtained, it is pre-
ferred to other alums for some uses. By far the most
abundant material for the manufacture of alum is afforded
by the alum-shales. Those best adapted to the purpose of
alum-making are pyritous clay rocks, in which coaly mat-
ter is disseminated, thus affording readier access to the
air, by which the decomposition of the pyrites is effected.
The decomposition of the pyrites, accelerated usually by
the long-continued application of a low degree of heat in
extensive piles, converts the alumina of the clay into sul-
phate of alumina, which is leached out, concentrated, and
converted into alum by the addition of a proper amount
of sulphate or chloride of potash or ammonia. The sul-
phate of alumina for this purpose is also largely made by
treating with sulphuric acid calcined clays which are as
free as possible from lime and iron oxide. For this use,
the excellent clays which abound in the Cretaceous beds
of New Jersey are admirably adapted ; and there can be
no doubt that pyritous shales, adapted to alum-making,
can be found in many portions of our own country, es-
pecially in the coal and lignite regions, from which they

3i6 APPLIED GEOLOGY.

are mostly extracted in Europe, though it has recently
been stated that most of the clays used in the United
States for alum-making are imported. It has also been
proposed to manufacture alum from the greensand which
abounds in the Cretaceous of New Jersey, by treating the
gently ignited greensand with sulphuric acid, the green-
sand furnishing the requisite potash and alumina.

On account of the strong affinity of its aluminous base
for organic coloring-matters, alum is largely used as a
mordant in dyeing, and by manufacturers of what are
called lakes, which are compounds of organic coloring
principles with alumina, of which madder lake, and the
brilliant cochineal lake called carmine, are familiar ex-
amples. It is also used in clarifying liquors, in some pro-
cesses of tanning skins, in medicine as an astringent, in
pastes for paper, and in small amounts by bakers for
whitening and raising bread.

Besides the substances applicable to chemical manu-
facture or use that have already been described, some
mention should also be made in this connection of mag-
nesia, strontia, and titanium. Magnesia will require some
mention in the chapter on refractory materials ; but, be-
sides the use based on its resistance to heat, are others of
a chemical nature. The sulphate, which is much used in
medicine under the name of Epsom salt, is found native
at Stassfurt as the mineral kieserite, and is also ob-
tained from the residues after extraction of potash from
some other Stassfurt salts. It is said to be used as a
cheap substitute for sulphuric acid in the preparation of
blanc fixe, a white pigment obtained by the precipitation
of chloride of barium, and also in the manufacture of
pearl-white, to be used in paper-making. Epsom salt and
magnesia alba can also be manufactured from magnesite, a
carbonate of magnesia, much resembling calcite and dolo-
mite in color and cleavage, but containing no lime, be-
sides being somewhat harder and more sluggish in its

SUBSTANCES FOR CHEMICAL PURPOSES. 317

effervescence with acids. It occurs in considerable beds
in the Lower Silurian rocks of Bolton and Sutton in Que-
bec, near the boundary-line of Vermont, where it is as-
sociated with beds of dolomite, steatite, and serpentine,
and in one locality with argillite ; and it will doubtless be
discovered in similar associations elsewhere, whenever an
active demand for it shall arise.

Strontia, the almost sole use of which has been here-
tofore in pyrotechny in the form of the nitrate for making
red fire, is recently coming into a greatly increased de-
mand, since it has been found that it can be utilized in
recovering sugar from the " melasse" which has hitherto
occasioned great loss in making beet-sugar. The two
minerals in which it occurs in economically important
amounts are strontianite, the carbonate, and a sulphate
called celestite (Latin ccdum), from its frequent sky-blue
tint. They are both heavy minerals, their specific gravity
being from 3.6 to 4 ; both are quite brittle, and both give
a bright-red colored flame when heated before the blow-
pipe. Like other carbonates, strontianite effervesces with
acids, and by this it may readily be distinguished from
celestite. These two minerals are sparingly distributed,
being found in nests and crevices, most commonly in lime-
stones, in the United States and Canada, but sometimes
also in sandstone and clay, or associated with gypsum.
They have been foun4 in the Lower Silurian limestones
of Manitoulin Islands, somewhat abundantly at Kingston,
and on the Ottawa River in Canada, as also in Jefferson
County, N. Y. ; and in Upper Silurian limestone near Scho-
harie and Lockport, N. Y., in Blair and Mifflin Counties,
Pa., and on Strontian and Put-in Bay Islands, Ohio, where
celestite is more than usually abundant. Strontianite is
obtained from Argyleshire in Scotland, where it was first
discovered, and somewhat abundantly in Westphalia, where
it occurs in veins or shrinkage cracks in Cretaceous clays;
while Sicily is much the most considerable producer of

3i8 APPLIED GEOLOGY.

celestite, exporting, it is said, about four thousand tons
annually. For its new use, in the manufacture of beet-
sugar, caustic strontia is obtained from strontianite by
heating it to redness to expel the carbonic acid. This,
when boiled with " melasse," forms a compound with the
sugar from which the strontia is separated by carbonic
acid, leaving the sugar to be dissolved and crystallized.
On account of its infusibility, caustic strontia is also
utilized in making tuyeres for blast-furnaces. The nitrate
of strontia, for use in pyrotechny, is obtained by treating
strontianite with nitric acid, or by heating celestite, mixed
with charcoal, to a high temperature, and then treating
with nitric acid the sulphide of strontia thus formed.

The compounds of titanium, which are now consider-
ably used in the manufacture of artificial teeth and in
porcelain-painting, are probably destined to a greatly in-
creased use in the manufacture by various chemical means
of a number of brilliant and permanent pigments. It is
found abundantly, in the form of ilmenite, or titanic iron,
in the Archaean rocks of Canada and Norway, where it
bears a great resemblance to magnetite, being, however,
very little magnetic It occurs also in crystalline rocks as
titanic acid, forming the minerals rutile and brookite.

CHAPTER XIX.

FICTILE MATERIALS.

THE arts of the potter and the glass-maker afford a
striking exemplification of what human skill can accom-
plish by a dexterous use of the properties of substances
which in their original condition are among the most com-
mon and least valued objects. What could be more dis-
similar to the magnificent creations of porcelain and of
glass which, in varied forms, deck the tables and adorn
the mansions of the rich, and which are objects of eager
desire to princes, or even to the humbler wares which
spread the board and minister to the modest wants of the
poor laborer, than heaps of clay and sand, of lime and
feldspar, with bins of soda, potash, salt, and borax, and a
few metallic oxides ? Yet the former are but the latter,
mingled by knowledge bought by generations of experi-
ence, fashioned by skill and taste, and subjected to a treat-
ment adapted to develop to the utmost their latent capa-
bilities. The art of shaping rude vessels from clay and
hardening them by fire is one which has been practiced
in the infancy of civilization ; but the highest and most
refined developments of this art tax to the utmost the sci-
entific resources and the cultivated taste of the most en-
lightened nations.

A number of the substances used as materials for the
manufacture of porcelain, earthenwares, and glass, have
already been described, as regards their geological occur-

320 APPLIED GEOLOGY.

rence, in the preceding pages. Such are potash, soda, and
lime, used as fluxes in glass-making and in glazes for pot-
tery ; such is oxide of lead, used as a flux for flint-glass
and in many glazes ; such are the oxides and a few other
compounds of the metals employed in glass- staining and
porcelain-painting ; such is salt, used as a glaze for stone-
ware, and borax, used also in some glazes, and as a partial
substitute for silica in some fine sorts of glass and artifi-
cial gems. Of the remaining substances, including clay,
silica, feldspar, granulite, steatite, and baryta, all of which
are used more or less largely in one or both of these arts,
clay is of the greatest interest, since it forms the basis of
all pottery- wares, and has also some other highly important
applications. This substance is a highly variable mixture
of kaolin, the mineral on which its valuable properties
depend, with silica, iron, lime, magnesia, the alkalies pot-
ash and soda, and often a small amount of mica and par-
tially decomposed feldspar. In blue and black clays, or-
ganic matter is also present, and disappears on burning,
leaving the clay white. Kaolin is a usually white and
unctuous 'hydrous silicate of alumina, which contains in
round numbers 46 per cent of silica, 40 per cent of alu-
mina, and 14 per cent of water. From this it will be seen
that two and a half times the alumina given in the analysis
of a clay will show the amount of kaolin that enters into
its composition. In some of the best clays this mineral is
much the largest ingredient, but small proportions of other
substances being mingled with it ; while in others it may
constitute considerably less than half of the aggregate, to
which, nevertheless, it gives its essential characters. Kao-
lin, then, is the essential ingredient of every true clay, and
by itself constitutes a clay of the finest quality ; all other
ingredients are non-essential accessories, and in some cases
injurious ones, rendering the clay unfit for its highest uses.
The most invariable accompaniment of kaolin in clay is
free silica, occurring in the form of sand intimately min-

FICTILE MATERIALS. 321

gled with the mass, and varying in amount from a mere
fraction of one per cent to more than fifty per cent of the
whole. This silica, though sometimes in grains of moder-
ate size, frequently exists in the state of an almost im-
palpable powder or dust, yet showing itself under the
microscope as minute angular particles of white, transpar-
ent quartz. The quartz in clay to be used for pottery
can hardly be considered as anything but a diluent of the
clay. Indeed, for the purposes of the potter, rich or fat
clays need to be mingled with finely comminuted silica,
in preparation for their use. By itself in a clay, it is inert,
acting, however, physically to counteract the tendency to
shrinkage and the production of checks and cracks which
kaolin alone exhibits when subjected to great heat. When,
however, verifiable bases, like potash, soda, and lime, are
present in the clay, the readiness of finely divided silica
to form with them fusible compounds at a high tempera-
ture causes that slight incipient fusion which gives rise to
the hardness and strength of the productions of the pot-
ter. Some one or all of the three bases that have just
been named, but potash much the most generally, are
found in nearly all clays, but usually in small quantities
in the best. It seems quite probable that these alkaline
substances which analysis reveals, and which produce
their effect on the fusibility of the clayey mass, are due, in
some cases at least, to partially decomposed feldspar, and
sometimes to mica present in the clay. Both of these
minerals contain potash, and feldspar usually contains
some soda and lime also. Feldspar in clays occurs in
small, sandy particles. Mica, from the ready flotation of
its minute laminae, is little likely to be found in clays
which are somewhat remote from their place of origin, and
which have possibly been worked over more than once by
transporting agencies before resting in their present beds.
The most undesirable contamination of clays for potter's
use is iron, which in some of its forms, as oxide, carbon-

322 APPLIED GEOLOGY.

ate, or sulphide, seems never to be wholly absent from any
clay. Sometimes its proportions sink to not more than a
fifth of one per cent ; more frequently, however, it is pres-
ent to the extent of two or three per cent or even more,
unfitting the clay for any save the coarsest and most com-
mon wares, since it imparts to them yellow, red, or brown
colors, according to its amount and the degree of heat to
which the articles are subjected. The following table of
analyses of a few approved pottery clays will give a fair
idea of their composition, and of the extent to which the
various ingredients other than kaolin may be present
without proving seriously detrimental. The titanic acid,
which will be observed to be present in several of the
clays, especially those from New Jersey, seems to be
wholly inert, producing no appreciable effect on their
properties. Following the excellent arrangement of analy-
ses given in the New Jersey Report on Clay Deposits, and
in the Ohio Report on Economic Geology, the kaolin-
forming compounds, the inert substances, and the com-
pounds which promote fusibility, with their respective
amounts, are placed in separate groups. It may here be
said that, for their finest uses, clays are washed by mixing
them thoroughly with water, and then allowing the creamy
liquid in which the clay will remain long suspended to
flow off into settling-vats where the clay is deposited. By
this means the coarser and heavier impurities are easily
separated.

The properties of clays which are of chief interest to
the potter are plasticity, and a tendency to shrink at a high
temperature. Most clays which are used by potters when
properly moistened are tenacious and pasty, and are sus-
ceptible of being easily shaped into any desirable form in
molds or on the potter's wheel. The forms thus made
harden considerably on drying, and when heated to a high
temperature assume the stony consistency which is famil-
iar to every one in earthenware and porcelain. This

FICTILE MATERIALS.

323

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324 APPLIED GEOLOGY.

valuable property of plasticity belongs solely to the kaolin
of the clay ; and plastic clays, rich in alumina, admit the
addition of a considerable amount of fine sand without
any material diminution of their plasticity. The plas-
ticity of clays is doubtless dependent in part on the water
held in chemical combination by the kaolin, since, when
this water is driven off by a red heat, plasticity is perma-
nently lost, and can not be restored by any treatment of
the stony product with water. That it is by no means
due wholly to the combined water, however, is shown by
the fact that some highly valued porcelain clays or kaolins
are but slightly plastic. An example of this is presented
by the clay of which the beautiful Sevres porcelain is
made, which, when prepared for use, is so little tenacious
as to require a quite special and expensive mode of hand-
ling in shaping the articles which are fashioned from it, a
fact to which the high price of this porcelain is in a great
measure due. Prof. George H. Cook, in his report on the
clay deposits of New Jersey, has shown that very probably
the plasticity of kaolin is largely due to a minute sub-
division of the crystalline plates and bundles of which the
mineral is originally composed, since recognizable crystals
of kaolin are found, by microscopic examination, to abound
in clays which are deficient in this property, while they are
absent, or nearly so, from highly plastic clays.

The shrinkage of clays, when subjected to great heat,
is a character quite as remarkable as their plasticity.
This arises partly, no doubt, from the expulsion of water ;
but that this is not the only cause, is shown by the fact
that the clay continues to contract with an increase of
temperature, even after the water has been entirely ex-
pelled. On this fact was based the pyrometer of Wedg-
wood, which attempted to measure very elevated tempera-
tures by the degree of contraction which they produced
in rods of clay ; an attempt which was not entirely suc-
cessful, on account of irregularities in the contraction

FICTILE MATERIALS. 325

of clays when exposed to long-continued heat. Highly
aluminous or fat clays shrink the most by heat, while very
sandy or lean clays shrink less or not at all. Hence, to
counteract the excessive shrinkage of fat clays, which is
apt to cause irregularities and cracks in the wares when
burned, they are tempered by mixing them intimately, be-
fore molding, with a proper amount of finely divided
silica, or with thoroughly burned and pulverized clay.

Clays originate doubtless from the decomposition of
feldspathic rocks, such as granites, gneisses, and porphy-
ries. The feldspars, from whose decomposition kaolin is
derived, are orthoclase, albite, and oligoclase, albite being
the most readily attacked by the agencies of decay, but
orthoclase, from its greater abundance, being the most
important source. These minerals, which are silicates of
alumina, with potash, soda, and lime, when exposed to the
action of carbonic acid and water, slowly lose their alka-
line constituents and some of their silica, take in water,
and so are ultimately converted to kaolin. When kaolin
is found on the place of its origin, it is naturally associ-
ated with the quartz and mica, which are the remaining
constituents of granite and gneiss ; or, with quartz alone,
when it is derived from the variety of granite called aplite
or graphic granite, which contains little or no mica. Such
clays are usually deficient in plasticity, probably from the
undisturbed crystalline condition of their kaolin. Of this
kind are apparently the porcelain clays of China, from
which the names kaolin and china clay have been de-
rived ; that of Saint Yrieix-la-Perche, not far from Li-
moges, which is the basis of the French manufacture of
porcelain ; that of Saxony, from which Dresden porcelain
is made ; and the china clay cf the granite district of
Cornwall. The Chinese kaolin and that of Cornwall, ac-
cording to Ure, have more plasticity than that of France
and Germany. On account of the slowness with which
kaolin subsides in water, with which it readily forms a
15

326 APPLIED GEOLOGY.

milky mixture, and of the consequent ease with which it
may be transported to long distances from the place of its
origin, much the largest portion which is formed is washed
away from its parent rock, and deposited in low grounds
or in bodies of water, forming often considerable beds,
like those found so abundantly in parts of New Jersey,
and those which constitute the under-clays of many coal-
beds. These translocated clays, as a result of their trans-
portation by moving water, have usually been freed from
most of their mica, and from their free silica, save that
which existed in a state of fine subdivision. They are
also commonly highly plastic, although those which have
been much solidified by pressure need to be softened by
weathering before they exhibit this character. These
clays are occasionally of such purity as to be adapted to
the finest uses in the manufacture of porcelain ; such,
however, are found in but few localities. Clays, adapted
to the manufacture of the more common articles of white
and ornamented stoneware, are more abundantly dis-
tributed, while others, which are too much contaminated
with iron for this purpose, are used for making jars, jugs,
and many other articles of a coarser kind.

Pottery clays are known to occur at many points in
the Archaean districts along the Appalachian range, from
New England to Georgia, and they are dug to a limited
extent in several localities. These are all surface deposits
of geologically recent origin, and some of them may be
found suitable for porcelain-making. Clay deposits, suit-
able for common wares, are reported at a number of
points in the far West, and are said to be utilized to some
extent ; but none of the very best quality, apparently,
have yet been found, unless the clay of Golden, Col.,
given in analysis No. 10, on a preceding page, should
prove to be one. The clay deposits most largely wrought
in this country hitherto are of Cretaceous and Carbonifer-
ous age. The Cretaceous clays of New Jersey, chiefly in

FICTILE MATERIALS. 327

Middlesex County, are abundant, and of qualities fitting
them for various uses. The excellent pottery clays are
not only largely sent to other States, but are the basis of a
very important manufacture of wares of various kinds at
Trenton, Jersey City, and Elizabeth, New Jersey produc-
ing nearly three fifths of the pottery wares that are made
in the United States. It can hardly be doubted that
some of the New Jersey clays may be used for the manu-
facture of the best porcelain. Some of the under-clays of
the lower coal-measures, in several of the coal-producing
States, are suited to the manufacture of pottery. They
have been most largely utilized for this purpose at Liver-
pool, O., on the Ohio River, and at two or three other
localities in the same State, where they are mixed with
clays from other regions, Ohio ranking next to New
Jersey in the amount of wares produced. At Huron,
Ind., and at other points in Lawrence County and also in
Owen County, noted deposits of kaolin called indianaite
occur, an analysis of which, showing an unusual propor-
tion of water, has been given on a preceding page. This
clay is used at Indianapolis for making encaustic tiles of
the highest grade of excellence, and at various points in
the United States in the manufacture of fine qualities of
white ware ; and it seems to be suitable for the very high-
est uses of the potter. No attempt has here been made
to enumerate the many promising localities of pottery
clays which are known to exist in the United States, but
which have not as yet been much developed. It is
certain, however, that clays adapted to the more common
uses are widely distributed, while it is probable that here,
as in all other countries, kaolins suitable for the manu-
facture of fine porcelain will be found to be rare. Any
mention of fire-clays has been purposely deferred to a
succeeding chapter ; and those coarser clays, which are so
widely used for brick-making and similar purposes, have
already been described in treating of building materials.

328 APPLIED GEOLOGY.

The materials on which is based the vast English
manufacture of pottery and porcelain in Staffordshire are
derived from the southwest counties of Cornwall, Devon,
and Dorset, in which are found extensive deposits of ex-
cellent clays and kaolin.

Although clay is the basis of pottery, several other
minerals are mingled with it to form the pastes that are
employed for the various kinds of ware. Of these, silica
has the most universal use, being mingled with the clays
in proper proportions to correct their tendency to too
great and irregular shrinkage in burning. This may be
obtained in the state of clean silicious sand, or of flint,
found disseminated in chalk and other limestone rocks ;
or of massive quartz, from veins of this mineral occurring
in regions of granitic rocks and silicious schists, such as
the Archaean areas described in treating of building-
stones. From whatever source derived, the silica is
ground to a very fine powder before it is used, and the
massive forms are frequently calcined before grinding, to
render them more brittle. This finely divided silex is not
only mingled intimately with the clay which forms the
body of the ware, but also enters into most of those vitri-
fiable mixtures which are used as glazes. Both silex and
pure clay or kaolin, however, are wholly infusible at the
temperature attained in porcelain-kilns. Hence, to im-
part to the clay mixture a tendency to that incipient vitri-
faction which increases the strength of the more common
wares, and gives to fine porcelain the translucency which
is so much admired, minerals like feldspar, lime, and crys-
tallized gypsum, are added, which at high temperatures
form with silica fusible compounds. The Chinese use for
their porcelain a mixture of kaolin with a silicious feld-
spar called petuntse, which mixture requires an exceed-
ingly high temperature for its vitrifaction. The standard
mixture for Sevres porcelain is, according to Ure, 59 per
cent of silica, 35.2 per cent of alumina, 2.2 per cent of

FICTILE MATERIALS.

329

potash, and 3.3 per cent of lime, which may be formed by
mingling kaolin with proper proportions of feldspar, flint,
and chalk. The English " tender porcelain" is composed
of clay and flint, with bone-dust, and sometimes potash,
as a vitrifying agent ; and in Wedgwood-ware, baryta is
used as a flux for the clay. The feldspar which is used
in these mixtures, to add the needful alkalies, is to be
sought, as might be expected, in regions of coarsely crys-
talline granitic rocks. That which is used in this country
seems to be obtained mostly from near Middletown and
Portland, Conn., and from middle Virginia; but numer-
ous other localities are known in the New England and
Atlantic seaboard States, where it can be found abun-
dantly.

The glazes which give to wares their impermeability,
and their smooth and often brilliant finish, are various
mixtures of flint, feldspar, ground glass, lead oxide, borax,
potash, soda, and lime. From among these substances,
various manufacturers compound for their wares glazes
which experience teaches them to be most suitable for
their purposes, the glazes being artificial glasses, some-
times transparent, sometimes opaque, which coat the
wares to heighten their beauty, or sometimes to conceal
their defects. Some porcelain has a glaze of feldspar
only. Many coarser articles of pottery are glazed by
merely throwing salt into the kiln among them at the
proper stage of the baking ; the salt is decomposed by the
heat, and its soda forms a fusible glaze with the silica and
alumina of the surface of the wares.

The colors which are used for the ornamentation of
pottery are mostly oxides of the metals, with a few chlo-
rides and chromates. These are mingled or fused with
proper fluxes, ground fine, and applied to the wares before
their final burning in a medium of gum-water, or of some
volatile oil. The colors are in some cases fused into the
glaze of the wares, and in others they are laid on under the

330 APPLIED GEOLOGY.

glaze and show through its transparent substance. The
oxides, which are chiefly used for painting porcelain and
other wares, are those of cobalt, iron, copper, antimony,
uranium, nickel, manganese, chromium, tin, and titanium,
with chlorides of gold, silver, and platinum, and a few chro-
mates. By a proper treatment of these substances and
their fluxes, the skillful porcelain-painter attains as com-
plete a mastery over the effects that he desires to produce
with these coloring materials that must pass through the
fire before showing their real nature, as the artist who
paints on canvas with ordinary pigments.

Glass. — It may be stated in a general way that this
beautiful, transparent, and impervious substance, which
plays so large a part in the comforts, conveniences, and
elegancies of civilized life, is a double silicate of potash or
soda and lime or lead. Its foremost materials are there-
fore silica, the alkaline substances, and lead oxide. In
some of the finer kinds of glass, boracic acid takes the
place of a portion of the silica. To correct the effects of
impurities in these materials, a little niter is commonly
used, as also small amounts of arsenic, and of black oxide
of manganese, which, from its purifying effects, is often
called glass soap. The geological occurrence of most of
these substances has already been described elsewhere.
The silica, which constitutes the largest ingredient in all
varieties of glass, was formerly prepared for the finer kinds
by calcining and grinding flint, from which is derived the
name of flint or crystal glass, applied to the very dense,
lustrous, and highly refracting double silicate of potash and
lead. It has, however, been found that, in somewhat nu-
merous localities, sand may be obtained of sufficient pu-
rity to be used for all the purposes of glass-making. For
all except the coarser varieties of glass a tolerably fine,
angular, white sand is needed, free from earthy impurities,
and especially from iron, which gives to glass a green tint.
In some localities, sea-sands are found of sufficient purity

FICTILE MATERIALS.

331

for any purpose. Thus the English manufacturers obtain
much of their sand from the Isle of Wight, and from
points on the coast of Norfolk and of Holland. In south-
ern New Jersey a large number of glass-houses obtain an
inexhaustible supply from a bed of Tertiary sand more
than ninety feet thick, and of very considerable extent,
much of which is so pure as to require no washing before
being made into window-glass. The glass-works in cen-
tral New York obtain a good sand for window-glass from
the modified drift around Oneida Lake.- In four counties
of central and southern Indiana great deposits of pure
white sand and slightly indurated sandstone occur, from
which an approved quality of plate-glass is manufactured.
Besides such deposits of incoherent sands of Tertiary age
and of recent origin, which are pure enough for glass-
making, white silicious sandstones are occasionally met
with in much more ancient rocks, which are so friable as
to be readily reduced to sand, and are then used for the
manufacture of glass. Notable among these is the St.
Peter's sandstone of the Lower Silurian, which occupies
considerable areas in Missouri, Minnesota, and Wisconsin,
and in La Salle County, 111. At many of its exposures, it
occurs as a clean white sandstone, remarkably free from
impurities, and so friable as to be readily extracted from
its beds by pick and shovel. A considerable manufacture
of glass is already based upon this sand, and its use seems
destined to be greatly increased. The Potsdam sand-
stone, which occupies the lowest horizon of the Lower
Silurian, also occurs of sufficient purity to afford a good
material for glass, in portions of northern New York,
Canada, and Wisconsin. A few only of the more note-
worthy exposures of sands which have been proved by
use to be sufficiently pure for the manufacture of the bet-
ter grades of glass have here been mentioned. Many
others will doubtless be eventually brought into use with-
in our broad domains ; but it will easily be conceived

332 APPLIED GEOLOGY.

that, though sand is a very widely and abundantly dis-
tributed substance, yet that which is of the high degree
of purity needed for the manufacture of fine white glass
is by no means common. For the making of bottle-glass,
in which purity of color is not required, inferior sands are
largely utilized. For this last purpose a rock called
granulite has recently come into quite extensive use in
Saxony and in southern England. Granulite, though
sometimes granular, is usually a schistose rock composed
of alternating layers of quartz and feldspar, with little or
no mica, and is usually of a white color, so that it is called
by the Germans weiss-stein, or white stone. The Saxon
granulite contains from 70 to 80 per cent of silica, with
a considerable per cent of potash in its feldspar, and less
than one per cent of iron; and, when melted with the
addition of sufficient lime to secure perfect fusion, makes
a pale- green bottle-glass, at about two fifths of the usual
cost for this article. Rock of this character, or that which
will serve the same purpose, viz., granite free from mica
and containing but a minimum amount of iron, may doubt-
less be found in the Archaean areas of Canada and New
England, as well as elsewhere, and where met with it will
afford excellent opportunities for the profitable invest-
ment of capital. The Saxon production from this source
is said to have reached twenty-two million bottles in 1880,
and to have increased rapidly since that time. It has
recently been proposed to use this glass for gas and water
pipes and other large castings, and, should this idea be
carried out successfully, deposits of granulite and graphic
granite, favorably located with respect to transportation,
will naturally assume great economic importance.

The substances which are used for coloring glass, like
those employed in porcelain-painting, are metallic oxides
and a few other compounds of the metals, all of which, it
need hardly be said, are obtained from geological sources.
Thus the white opaque glass called enamel derives its

FICTILE MATERIALS. 333

color and opacity from the oxide of tin ; a blue color is
given by the oxide of cobalt, green by oxide of copper,
yellow by chromate of lead and by silver chloride, and
other colors by similar means. Without at all entering
into the technicalities of glass-making, it may appropri-
ately be said here, in illustration of the geological origin
of its materials, that the chief varieties of glass are com-
pounded of the following ingredients :

Common bottle-glass, of silica, alumina, soda, and
lime ; Bohemian glass, of silica, potash, and lime ; crown-
glass, of silica, potash or soda, and lime ; window-glass
and mirror-plate, of silica, soda, and lime ; crystal and
flint glass, of silica, potash, and lead oxide ; strass for arti-
ficial gems, of silica and boracic acid, potash, and lead
oxide.

The differences of quality are due to the relative
purity of the ingredients, the proportions in which they
are compounded, and the skill and care with which they
are treated.

For additional information with regard to materials for the manu-
facture of pottery and glass, the student is referred to the following
works : Ure's " Dictionary of Arts," etc., articles on clays, glass, and
pottery ; " Geology of New Jersey," 1868 ; the " New Jersey Report
on Clay Deposits," 1878 ; and " Ohio Geological Report," Vol. V,
chap. ix.

CHAPTER XX. .

REFRACTORY SUBSTANCES.

FOR numerous and highly important purposes among
civilized nations, materials are required which will endure
very high degrees of heat without injury; and every im-
provement whereby more elevated temperatures are se-
cured by the skillful use of fuel, renders the need of such
refractory substances more imperative. It is necessary
only to direct attention to the furnaces used for various
metallurgical operations, and especially those in which
iron and steel are to be treated ; the kilns in which
pottery is baked and the materials of glass are fused ; the
seggars, or fire-proof boxes, in which earthenware and
porcelain are exposed to the heat of the kiln ; the large
pots or crucibles in which the ingredients of glass, and
metals like copper, silver, and steel, are melted ; and the
linings of Bessemer converters, in which molten iron is to
be subjected to ebullition by the action of a current of air
to burn out its impurities — to indicate the variety and im-
portance of the uses for which refractory substances are
required, and the fierce heats which they are called upon
to endure without softening. All these substances are
minerals which enter into the composition of rocks, and
are therefore derived from geological sources.

Foremost in importance among these is fire-clay, both
from its great infusibility, and from the readiness with
which it may be fashioned into convenient forms. This

REFRACTORY SUBSTANCES. 335

clay does not differ from the pottery clays described in
the preceding chapter in any respect save in its greater
necessary freedom from the fluxing ingredients, potash,
soda, lime, magnesia, and iron oxide. The presence of
any considerable proportion of these fluxes in a clay, to
the extent, for example, of two or three per cent, in-
juriously affects its heat-resisting properties ; and the
combination of two or more of them proves more detri-
mental than a like amount of any one, because the com-
pound silicates are more fusible than the simple ones.
The more completely a clay is composed of kaolin, or of
kaolin and silicious sand, the more refractory it is likely
to show itself, since both these substances are wholly in-
fusible at the temperatures attained in industrial opera-
tions. This may be seen by examining the following
analyses of several of the most celebrated fire-clays of
this country and of Europe. They are arranged in the
order of their resistance to an extreme fire-test, made by
exposing small triangular prisms of each with sharp edges,
for a half-hour, to a heat in which platinum was melted.
Exposed to this heat, some of the clays retained their
sharp edges ; others, while retaining the sharpness of their
edges, were more or less blistered or distorted ; in others,
the edges were rounded and fused, and a number melted.
This series of tests was undertaken by the Geological Sur-
vey of New Jersey, and its results and methods are pub-
lished in the annual report of that State for 1880. On
this was founded a tentative division of the clays into
seven classes, according to their relative refractoriness ;
and to this classification the numbers in the first column
refer. The analyses of the same clays have been selected
from those given in the New Jersey report on clay de-
posits, to which reference has been made before. Neither
soda nor lime appears in any of these analyses.

As all these clays are well esteemed for their resistance
to heat, it may be assumed that the amount of the flux-

336

APPLIED GEOLOGY.

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ing ingredients in a fire-clay can not safely exceed what is
found in these, especially as one of the clays which occu-
pies the lowest class contains the most of the fluxes.
When it is considered, also, that in these tests pure rock-
crystal was melted, a reason will be found why the four
clays that contained the most free silica rank lowest in
this list. It would be difficult to assign reasons for some
other differences in refractoriness shown by the clays in
the table, as, for example, why clay No. 7 should not have
been as refractory as Nos. 2 and 3, unless it is to be found
in the texture and density of the clays.

Aside from the very superior fire-clays obtained from
the Cretaceous clay deposits of New Jersey, the great
bulk of the refractory clays of Europe and the United
States are derived from the under-clays of coal-beds — not
only those of the coal-measures proper, but also, as in
several of our Western Territories, those bearing similar
relations to the lignitic coals of the Upper Cretaceous.
These under-clays doubtless owe their freedom from alka-
line constituents to the fact that, having once been soils
which sustained a luxuriant vegetation, these substances
have largely been withdrawn from them by the processes
of plant-growth. When first dug, they are hard and
stony, but can be softened and rendered somewhat plastic
by sufficient weathering. Frequently, however, they are
merely ground fine with water, mixed with a proper
amount of previously burned and pulverized fire-clay
called calcine, and sufficient sandy, plastic clay to serve
as a bond, and then molded and burned for fire-brick,
glass-pots, retorts for gas and zinc works, terra-cotta
wares, chimney-tops, and many other articles which are
either to be exposed to high temperatures, or which need
to be fired strongly to secure the characters desired.

Dinas or silicious bricks, which are employed where an
excessive temperature is attained, as in the melting-cham-
ber of regenerative furnaces, in which ordinary fire-brick

338 APPLIED GEOLOGY.

does not endure well, were originally made from a sili-
cious rock locally called clay, though containing about 97
per cent of silica, occurring in the Carboniferous strata of
South Wales. This rock was disaggregated and mixed
with a small portion of lime to serve as a cement, then
molded and burned at a high heat for several days. At
the high temperature employed, the lime combines with
an equivalent amount of silica to form a refractory silicate
which binds the whole together. Similar bricks are now
made from any pure silicious rock, which is ground and
mixed with about one per cent of milk of lime to form a
bond for the mass when burned. The silicious rock em-
ployed for this purpose should be free from iron and
mica. Silicious bricks expand somewhat when heated,
and so keep the parts of the furnace tight.

The substance called ganister, used as a refractory lin-
ing for Bessemer converters, is a very fine-grained and
tough sandstone, or quartzite, containing a certain amount
of finely disseminated aluminous matter. When this is
ground fine and mixed with water, the contained alumina
acts as a sufficient bond. Rock for this purpose is ob-
tained in England from a silicious under-clay of the coal-
measures at several points, the best being found in the
vicinity of Sheffield. A rock of a similar character is
found in the Archaean strata in the immediate vicinity of
Marquette, Mich., where a thin-bedded and ripple-marked
quartzite is quarried to a considerable extent for this use.
Any pure silicious rock, ground to a fine powder and
mixed with a proper amount of good fire-clay, is said to
answer well in place of ganister.

What are called fire-stones are usually silicious sand-
stones, which should be free especially from iron, and
from mica the potash in which renders it a fluxing in-
gredient. Fire-stones may be found by careful exam-
ination and trial in many localities, where their cheap-
ness makes them a reasonably good material for many

REFRACTORY SUBSTANCES. 339

purposes, as for the hearths of furnaces and fireplaces,
and for the construction of kilns, though their use is now
largely superseded by that of fire-brick. Where used, it
is hardly necessary to say that they should be thoroughly
dried before being subjected to heat.

For a number of purposes bricks are very desirable
which shall combine with the ability to endure unchanged
all ordinary degrees of temperature, very feeble conduc-
tivity for heat, and much less specific weight than common
fire-brick. Such materials, called floating bricks, because
they are lighter than water, are made from an infusorial
earth called "fossil meal," composed of the microscopic
skeletons of silicious organisms, and forming a whitish
earthy mass, very light, and resembling chalk in appear-
ance, but yielding no effervescence with acids. This sub-
stance, mingled with a small amount of clay, may be made
into bricks which weigh less than one fifth as much as or-
dinary bricks, which resist heat well, and which when red-
hot at one end are not perceptibly warm at the other. An
earth of this kind is abundant in Tuscany ; and it is prob-
able that the Tertiary infusorial earth which occurs in a
bed thirty feet thick near Richmond, Va., and in a still
thicker deposit at Monterey, Cal., is adapted to this use.

Graphite or plumbago, under the name of black-lead, is
familiar to every one from its wide use in lead-pencils. It
is a soft, black mineral, of a greasy feel and metallic luster,
and easily gives a lead-gray mark on paper, on which ac-
count it is used in the manufacture of pencil-leads. Aside
from the impurities with which it is often contaminated, it
is pure carbon, having the same composition as the dia-
mond, to which in other respects it is so unlike ; and it is
in all probability the ultimate stage in the series of changes
which vegetable matter undergoes, passing through the
conditions of peat, lignite, and mineral coal, to end in
graphite, which is not only infusible, but also incombusti-
ble under the conditions which are presented in the in-

340 APPLIED GEOLOGY.

dustrial use of heat. It is usually found in quantities of
economic importance only in the most ancient crystalline
rocks, associated frequently with limestones, and also with
gneiss and schistose rocks. In these it occurs, either dis-
seminated more or less abundantly in certain horizons of
the rock, or forming pockets and nests, or filling vein-like
fissures with mineral of a high degree of purity. It is met
with at many points in the Archaean region, extending from
the Province of Quebec, in Canada, through New York,
New Jersey, etc., to North Carolina and Alabama ; but in
most of the localities it is either too sparingly dissemi-
nated to pay for its extraction, or is of such physical char-
acter as not to admit of cheap separation from its impuri-
ties. It has been mined to some extent at Bloomingdale,
N. J., Bucks County, Pa., and Sturbridge, Mass., being
found in graphitic gneiss ; but the chief place in the
United States where it is mined at present is near Ticon-
deroga, N. Y., where it is obtained from a graphitic
schist, about fifteen feet thick, and containing from 8 to
15 per cent of disseminated graphite. This locality
yielded two hundred net tons of graphite in 1882, the
remainder of the United States producing only twelve
tons. In Ottawa County, Quebec, extensive deposits
occur in the Laurentian limestones, containing in some
localities 20 to 30 per cent of disseminated graphite. Fis-
sure-veins are also found here, which yield a very pure
mineral, but it is said to be usually in quite limited
amounts. Graphite deposits have also been worked at
intervals in the Archaean rocks near St. John, New Bruns-
wick, and it is reported to occur in graphitic schists in the
Archaean area of northern Michigan, as also in some of
the Western Territories. The Island of Ceylon furnishes it
in immense vein deposits of singular purity at Travancore,
and from these the largest supplies of the world are de-
rived, although Austria and Bavaria produce annually
from 15,000 to 18,000 metric tons. The rocks in which

REFRACTORY SUBSTANCES. 341

available graphite is most likely to be found are, there-
fore, those of Archaean age, though small amounts occur
in strata as late as the coal-measures. The famous de-
posit of Borrowdale in England, which is now no longer
worked, occurs in veins in interbedded trap ; and its
product was once sold at from $8 to $12 per pound, for
the manufacture of pencils, extraordinary precautions be-
ing taken to prevent theft. The present price of graphite
is from $25 to $200 per ton, according to its purity and
fineness.

The properties on which depend the important uses of
graphite in the arts are its infusibility, its unchangeable-
ness in the air, even when exposed to high heat, its soft,
unctuous texture, its ready conduction of electricity, and
its graphic quality, from which is derived its name graph-
ite, from the Greek grapho, I write. Of these, its in-
fusibility properly concerns us in this place ; but, for the
sake of completeness, its leading uses may be briefly
enumerated here, although some of them belong properly
in the succeeding chapter, where they will be referred to.
Fully one third of all the graphite that is produced is
used for refractory articles, such as small furnaces, nozzles
and stoppers for the Bessemer process, and crucibles for
melting steel, silver, copper, and brass. For these pur-
poses it should be free from lime and iron oxide, with
which it is liable to be contaminated ; since, for such
uses, it must be intimately mingled with a proper propor-
tion of fire-clay to give it strength, and the silica of the
clay would form fusible compounds with iron and lime.
Other large uses of graphite are for stove-polish, to pro-
tect iron articles from rust, and for foundry-facings, two
fifths of the product being employed for these purposes,
an additional amount being also used for glazing powder
and shot. A fourth highly important and increasing use
is for the lubrication of heavy machinery, in which it is
employed in the state of a fine powder, and in various

342 APPLIED GEOLOGY.

patent greases. Its use in pencil-leads is familiar to every
one, besides which it is considerably employed in electro-
typing and for several minor purposes.

Although caustic lime is one of the most infusible as
well as most easily obtained of known substances, it is not
capable of being used in the large way as a refractory
material, because of the readiness with which it absorbs
water from the air and then crumbles to powder. It is,
however, used for constructing the small furnaces and
crucibles in which platinum is melted and refined by the
heat of the oxyhydrogen blow-pipe flame, a small but
quite important use. Caustic magnesia is also highly in-
fusible, and in Germany is converted into a very refrac-
tory brick, being cheaply obtained from the waste liquors
of the Stassfurt salts described in a preceding chapter, by
precipitation from its chloride by milk of lime, or by sub-
jecting the chloride to the action of an oxidizing flame
and superheated steam. A cheap and effective mode of
utilizing in the large way the refractory properties of a
combination of these two alkaline earths has recently
been devised, whereby the lime produced by calcining
strongly a somewhat silicious dolomite is made into a
paste with pitch, and then molded into bricks, or used
directly as a refractory lining for Bessemer converters.
By gradual heating, the pitch is burned out, and the re-
fractory earths are left in the shape required. This is the
so-called " basic lining," by the agency of which a consid-
erable percentage of phosphorus may be eliminated from
iron, rendering available, for steel-making purposes, iron
hitherto wholly unfit for this use. Magnesian limestones,
suitable for this purpose, are widely distributed among the
geological formations, and need no special mention in
this connection. It is said by Bloxam, on the authority of
Gilchrist, that the best composition of a magnesian lime
for the basic process is, lime, 52 per cent ; magnesia, 36
per cent ; silica, 8 per cent ; alumina and iron, 4 per cent.

REFRACTORY SUBSTANCES. 343

Steatite, called commonly soapstone or potstone, is a soft,
compact, gray or greenish form of talc, and derives its
name soapstone from its soapy feel. In composition, it is
a hydrous silicate of magnesia, and is highly infusible, on
which account it is considerably used as a fire-stone in
hearths, stoves, and furnaces, and for register borders and
pipe-holes, as also in gas-jets and in several articles for
household purposes. It is found in the ancient crystal-
line rocks of the Atlantic border States, and is quarried
chiefly in Vermont and New Hampshire, though similar
deposits are known to occur in several other States.

Mica and Asbestus. — The leading uses of these two
minerals are based upon their infusibility, coupled in the
one case with toughness and great transparency, and in
the other with a highly fibrous texture and a very slight
conductivity for heat. The only desirable variety of mica
is muscovite, in large transparent crystals, free from irreg-
ularities and accessory minerals. Such crystals occur
chiefly in veins of exceedingly coarse-grained granite, and,
as might naturally be expected, they are to be sought for
chiefly in regions of Archaean rocks, as along the Appala-
chian range, and in the vicinity of the Rocky Mountains
and the Sierra Nevadas. The chief production of mica
has hitherto been from western North Carolina, and from
the Black Hills, near Deadwood. In North Carolina, ac-
cording to the Geological Report of that State in 1875, the
mica occurs in veins of coarse granite with walls of gneiss,
in which are found rude crystals of mica weighing from
thirty to fifty pounds, and in a few instances even as
much as a thousand pounds, affording, occasionally, sheets
three feet across. The most profitable workings here are
on the sites of pits and galleries of some ancient race of
men. Similar ancient workings are reported by Prof.
Smith to exist at various points of eastern Alabama, giving
promise of merchantable mica in that State. The mica
from the Black Hills is reported to be of very fine quality,

344 APPLIED GEOLOGY.

and plates of large size are sometimes produced. " The
main ledge is said to be fourteen feet wide, and to consist
of a central mass of feldspar and 'porphyry,' with a casing
of mica which varies in width from three to four feet on
each side. The country rock is granite." Mica is pro-
duced also in Maine and New Hampshire ; and a com-
pany with large capital is reported to have been lately
formed in Marquette to develop a promising mica prop-
erty in northern Michigan, and another in Chaffee County,
Col., for a like purpose. It is well to bear in mind that it
has been observed in North Carolina that, wherever horn-
blendic rocks or chloritic schists form the walls of the
mica-bearing veins, the mica is apt to be badly specked
with magnetite. The chief use of mica is for the trans-
parent plates of stoves and furnaces, and for lanterns,
some of the larger plates being also occasionally utilized
in surveyors' instruments in the place of glass. Finely
pulverized mica is also used as an absorbent of nitro-
glycerine in one variety of high explosives, and likewise
as a finish for wall-papers, and for some other ornamental
purposes. The price of sheet-mica varies at present from
twenty-five cents to five dollars per pound, according to
size and quality, exceptionally large and fine sheets bring-
ing even a higher price.

Asbestus affords a curious example of a mineral whose
leading properties have been known for many centuries,
and have caused it to be somewhat used by the ancients
for incombustible fabrics, which were objects of curiosity
rather than of practical utility ; yet whose important in-
dustrial capabilities have been neglected until very recent
years. It is a fibrous form of several minerals, like horn-
blende, pyroxene, and serpentine, is of a white, light
green, or brownish color, and is practically infusible by
the heat of ordinary fires. The most valuable kinds
occur in long, silky, parallel fibers, which are strong and
flexible, and capable of being spun like flax by proper

REFRACTORY SUBSTANCES. 345

machinery, and woven into fabrics that are incombustible.
Hence its name, which is a Greek word applied to the
mineral with reference to this property. Other varieties,
in which the fibers interlace so as to form a kind of
natural felt, are called mountain leather and mountain
cork, while the fine, silky, fibrous variety is sometimes
called amianthus, from a Greek word meaning unpolluted,
because the fabrics woven from it, when soiled, may be
readily cleansed by passing them through fire. To be of
any considerable economic importance, asbestus needs to
have length and fineness of fiber, combined with tough-
ness and flexibility. These qualities are often lacking in
mineral which has a promising appearance, the fiber being
short, or brittle and harsh to the touch, making a sub-
stance of little or no value. Hence the expediency, when
a new deposit is discovered, of having the mineral care-
fully tested in respect to these qualities, before incurring
any considerable expense in working it. Asbestus is
found in regions of crystalline rocks, most commonly
associated with serpentine, occupying vein-like crevices
which are of uncertain and usually quite limited extent,
causing great difficulty in mining it with profit. The
finest is produced in the Italian Alps and in Corsica ; but
a considerable amount of asbestus of good quality is ob-
tained from the Province of Quebec, from several of our
Atlantic seaboard States, ranging from New York to
Georgia, and from some of the far Western States, es-
pecially California. Doubtless more diligent search with-
in our great areas of crystalline rocks, stimulated by the
rapidly growing demand for this mineral, will result in
many new discoveries, some of which may yield an article
equal in quality to the best Italian.

The uses of asbestus are based upon its fibrous text-
ure, its resistance to fire, and its very feeble conduction of
heat and electricity. It is most largely used for packing
the joints and working parts of steam-machinery ; for

346 APPLIED GEOLOGY.

covering boilers and steam-pipes to prevent loss of heat
by radiation ; and as a fire-proof lining for floors and
ceilings, and for the walls of wooden buildings. For
some of these purposes it is spun into yarn by the aid of
special machinery, or woven into sheets and tape, with
the addition, for some uses, of India-rubber ; for others, it
is felted and pressed into sheets of a kind of paper called
mill-board, of any required thickness. In this latter form
it is used also as an insulator in dynamos. It is woven
into fire-proof cloth for the drop-curtains of theatres, for
furnace-men's aprons and leggings, and for other similar
purposes ; and it has been proposed to construct from
such cloth light fire-proof shields to protect firemen from
the heat of conflagrations. Twisted into cord and rope it
may be used for fire-escapes, since it has great tensile
strength. It has long had a limited use in incombustible
wicks for lamps, for which it is admirably adapted. It
is also used for making fire-proof cements and paints.
There is no reason to doubt that, with the probable in-
crease in the production and diminution in cost of this
useful mineral, there will be a large increase in its indus-
trial applications in the immediate future.

The United States production of asbestus in 1882 was
reported to be twelve hundred tons, and its average value
at the mines about thirty dollars per ton, varying from
fifteen to sixty dollars, according to quality, exceptionally
fine mineral commanding much higher prices than these.

With reference to the substances treated of in this chapter, the stu-
dent can profitably consult the following works, to which many others
might easily be added : Bloxam on Metals — the chapter on " Refrac-
tory Materials " ; " New Jersey Report on Clay Deposits," 1878, and
Annual Report for 1880 ; " Ohio Geological Report," Vol. V ; " Geo-
logical Report of North Carolina," 1875 ; " Geology of Canada," 1863,
section vi of chapter xxi ; " Mineral Resources of the United States,"
1883 ; also any good encyclopaedia ; and the files of the " Engineering
and Mining Journal," by the aid of its excellent indexes.

CHAPTER XXI.

MATERIALS OF PHYSICAL APPLICATION.

A VERY considerable number of purposes, some of
which are sufficiently common and consequently of a high
degree of importance, are subserved by substances of geo-
logical origin by reason of their possession of certain
physical properties, as texture, hardness, and color ; little
previous preparation, and that of a purely mechanical
nature, being necessary to adapt them for their uses.
Such are the substances which are used for mending
roads and improving streets and walks ; for grinding vari-
ous kinds of grain as well as many minerals ; for giving a
keen edge to cutting instruments, and for imparting a fine
polish to wood, stone, and metals ; for drawing purposes,
and for the cheap and rapid reproduction of pictures ; for
diminishing friction ; for making molds for castings in
metal ; and for some other uses of analogous character.
The mere enumeration of these utilities is sufficient to
show how nearly some of them touch the comforts and
conveniences of civilized man ; how much others affect
the efficiency of his efforts ; and how intimately still
others concern his opportunities for refinement.

Materials for Roads and Walks. — The commer-
cial rank and the industrial advancement of any commu-
nity are pretty fairly expressed in the excellence of its
means of communication, not merely by lines of railway,
but also by those more numerous and highly important

348 APPLIED GEOLOGY.

avenues of travel and intercommunication which afford
ready access to every hamlet and every home. The im-
provement of country roads is usually effected by the
judicious use of those materials which are most easily
accessible in any given locality. In very many regions,
deposits of gravel, the accumulations of streams, and
sometimes of the ocean, or the relics of the glacial age,
afford a convenient means of improvement, which, from
the usual hard and silicious nature of the pebbles, is both
cheap and durable, making, with due preparation of the
foundations, and by proper arrangement of the coarser
and finer portions, excellent and enduring roadways. In
some few localities where gravel is not found, ledges of
conglomerate, not too closely cemented, may be acces-
sible, which, at some slight cost for crushing, may afford
excellent material for roads. In other cases, silicious
limestones of the vicinity, crushed by rock-breakers, or
broken to proper sizes with hammers, are used for road
purposes, needing occasional renewal on account of the
comparative softness of the stone. Harder and more en-
during material is afforded by the hornstone and chert
which occur at most of the exposures of the largely
quarried Corniferous limestone across the State of New
York and westward, and which are found accompanying
some of the limestones of the Lower Carboniferous age in
the Western States. In regions of crystalline formations,
rocks of the granite class — quartzites, felstones, tough
porphyries, and still tougher traps — may be made avail-
able for road-metal. All these rocks, of hard and tough
character, can be most cheaply reduced to sizes proper
for macadamizing roads by means of rock-crushers driven
by steam or water power ; and though the first cost of the
roads constructed from such materials may be somewhat
large, yet their convenience and durability, when once
properly made, will more than compensate for the original
outlay. In European countries, permanent roadways are

MATERIALS OF PHYSICAL APPLICATION. 349

constructed from all the substances that have here been
enumerated ; their use is increasing in the more thickly
settled portions of our own country ; and there can be no
doubt that, ere long, a people so progressive and so prac-
tical as ours will become impatient at the too often
wretched condition of our roads, and will seek, in durable
rock materials, for a permanent means of improvement.
The need of previous careful drainage, and the prepara-
tion of a suitable foundation for a road, before using any
of these materials, has not been insisted on here, because
it is a matter which belongs rather to the road-engineer
than to the geologist.

For those streets of cities and large towns which are
devoted chiefly to residences, and which are little used
for transportation, macadamized roadways, properly con-
structed of materials such as have already been mentioned,
present the advantage of being comparatively noiseless —
an advantage which may compensate in a good degree
for their liability to dust in dry weather. .But for streets
which are much used as thoroughfares for heavy traffic,
the road materials need to be employed in larger and
more solid forms, to secure stability under stress. For
this purpose, rectangular blocks of hard and tough varie-
ties of stone are used, arranged in courses, such width of
the blocks being best as affords the most convenient hold
for the feet of horses. A number of kinds of rock are
well adapted to this use, such as granites, hard sandstones,
quartz schist, felstone, trap, and porphyry. The granites
most suitable for pavements are those of medium fineness
of grain, in which quartz rather than feldspar is a domi-
nant ingredient, or those into which hornblende enters in
a considerable amount, those being naturally selected in
which a somewhat easy rift in certain directions facilitates
their reduction to proper shapes. Quartz schists, or those
highly silicious mica schists in which the mica is barely

in sufficient amount to impart a schistose structure, may
16

350 APPLIED GEOLOGY.

be wrought with ease into good paving-blocks. Felstone
is also sometimes used for pavements where its structure
admits of easy working. These three kinds of paving ma-
terials may be obtained in those regions of Archaean rocks
which were described in the chapter on building-stones,
and which have since been several times mentioned. In a
number of our Northern cities, of which Rochester, Buffalo,
and Cleveland are examples, a silicious sandstone obtained
from the lower member of the Niagara period in western
New York, and called the Medina sandstone, from one of
the villages where it is largely quarried, is extensively used
for pavements, and is found excellent for this purpose.
In the region about Medina and Albion it is a hard, well-
cemented sandstone of extraordinary strength, susceptible
of being wrought without much difficulty into convenient
blocks, and of sharp grit, so that it shows little tendency
to become smooth by wear. In the northeast part of New
York, also, very hard silicious sandstones occur in strata
of the Potsdam period, which are admirably suited for use
in paving. In the immediate neighborhood of New York
city, at many points in Connecticut and New Jersey, and
in elongated belts of strata which stretch parallel to the
Atlantic border even to the boundary of South Carolina,
occur dikes of basaltic trap-rock which has a very exten-
sive use for paving-blocks. It is a hard, heavy, and very
tough rock, and makes pavements of unsurpassed dura-
bility ; but its tendency to become smooth and slippery
by wear renders it expedient to shape it into narrower
blocks than those which are commonly used. It is per-
haps needless to say that only those portions of the trap-
rock are fitted for this use whose structure admits of their
being easily split into the required forms.

It will be seen, therefore, that for all purposes of road
construction, a rock needs to be hard, that it may endure
wear ; tough, that it may not easily yield to blows ; of such
structure as to admit of being wrought without too great

MATERIALS OF PHYSICAL APPLICATION. 351

expense ; and, if possible, of such texture as to remain some-
what rough in use.

The qualities which are desired in a material for the
construction of sidewalks, and for some other kindred
uses, are evenness of surface, closeness of texture to resist
the penetration of moisture, and a sufficient degree of
hardness to withstand the kind of wear to which it is to
be subjected. The ability to secure slabs of different di-
mensions and thickness, to adapt them to use under a
variety of circumstances, is also very desirable. These
qualities are well combined in what are called flag-stones,
which are even-bedded and somewhat argillaceous sand-
stones, occurring in sheets of from two to eight inches in
thickness, associated with shales and thicker bedded sand-
stones. Such flagging is largely quarried in beds of the
upper part of the Hamilton period and of the Lower Che-
mung (Portage group), near the Hudson River, in Ulster
and Greene Counties ; at the south end of Cayuga Lake
near Ithaca, in strata of the Chemung period ; in the
northern part of Wyoming County, Pa., in strata which are
referred by the Pennsylvania geologists to the lower part of
the Catskill period ; and near Warren, Ohio, in beds of the
Lower Carboniferous (Waverly group). Where such flag-
stones can not be obtained without too great expense, re-
sort is often had to thin-bedded or easily divided rocks of
other kinds. Thus, thin-bedded limestones are sometimes
applied to this purpose, though the surface is liable to be
somewhat uneven, and to become dangerously smooth by
use. In northern Ohio, soft sandstones, of Lower Car-
boniferous age, are split or sawed into slabs of proper
thickness, which, although somewhat porous and liable to
wear, make very handsome walks. In many localities,
sidewalks and sometimes roadways are constructed from
a concrete of fine gravel, pulverized limestone, and asphal-
tum, or of sand and hydraulic cement, which, when prop-
erly made, are very good.

352 APPLIED GEOLOGY.

Asphaltum, for this purpose, is obtained chiefly from
the Island of Trinidad, and some also from Santa Barbara
County, Cal., which is used on the Pacific coast. The tar
from gas-works serves as a fair substitute for asphaltum
for this use. Many of the streets of Paris are paved with
a calcareous asphalt, obtained from Val de Travers and
elsewhere in Switzerland ; and this substance is also im-
ported into the United States to a considerable extent, to
be used in sidewalks and for coating roofs. The Geo-
logical Report of Canada for i88o-'82 announces the dis-
covery, on the Athabasca River, of a bituminous sand-rock,
which is probably suitable for walks and water-proofing.
It is worthy of consideration whether a valuable applica-
tion of such water-proof concretes could not be made in
the pavements of cities, especially on streets devoted to
residences, by using them as an impervious cement be-
tween the paving-blocks, thus preventing, at least in a
measure, the unhealthful emanations which arise in warm
weather from the putrefaction of organic matters, while at
the same time guarding against displacements by the
action of frost.

This enumeration of some of the leading geological
substances which are utilized for roads and walks may
serve as an indication of those physical properties of
rocks and minerals which best adapt them to such uses,
and may guide the inquirer to still other substances in his
own neighborhood that may be employed for a like pur-
pose.

Abrasives. — What are here classed as abrasives are
those rocks and minerals which, by reason of their in-
trinsic hardness, or of certain grades of hardness and
texture, are used for sharpening all kinds of edge-tools,
for triturating grain and minerals, for polishing wood,
stone, and metals, and for rock-drills. These are, with a
single exception, wide-reaching as well as important uses,
affecting the convenience and efficiency of many arts and

MATERIALS OF PHYSICAL APPLICATION. 353

trades, and some of them concerning every household.
And foremost among these in treatment as in importance
may justly be placed those substances used to give a keen
edge to cutting instruments, the grindstones and whet-
stones; for, not to speak of the many occupations which
owe much of their efficiency to the excellence and variety
of their edge-tools, there are few individuals who do not
find daily occasion to use such articles as knives and
scissors.

A better description could not well be given of the
conditions which must combine to make a good grind-
stone-rock than that of Dr. Dawson, in his "Acadian
Geology," p. 154: " These grindstones have been formed
from beds of sand, deposited in such a manner that the
grains are of nearly uniform fineness, and they have been
cemented together with just sufficient firmness to give
'cohesion to the stone, and yet to permit its particles to
be gradually rubbed off by the contact of steel. A piece
of grindstone may appear to be a very simple matter, but
it is very rarely that rocks are so constituted as perfectly
to fulfill these conditions." The infrequency of occur-
rence here spoken of is well exemplified in this country
and Canada, which, in all their vast area, have as yet de-
veloped but three or possibly four regions in which occur
strata of the proper quality to yield first-rate grindstones :
one, near the head of the Bay of Fundy in Nova Scotia ; a
second, in northern Ohio, near and west of Cleveland ;
and a third, at Point au Barques in Michigan. These are
all in strata of the Carboniferous age, and mostly in its
lower portion ; though one of the two geological horizons
which yield grindstones in Nova Scotia lies above the
productive coal-seams. Besides these localities, what is
called the "Gray Band," in the lower portion of strata of
the Niagara period (Medina group), in the Province of
Ontario, Canada, is said at some points to present the
characters requisite to make grindstones of good quality.

354 APPLIED GEOLOGY.

It is interesting to observe that in England, also, most of
the rock which is used for grindstones is derived from the
grits of the Carboniferous age. Of this age are the grind-
stones quarried near Newcastle and Sheffield, as also in
Yorkshire and Staffordshire, and at a few other localities.
It would seem that in this age, more frequently than in
the others,' conditions were presented favorable for the
formation of an even-grained, homogeneous sand-rock, not
too closely cemented.

Rock suitable for the manufacture of whetstones and
hone3 is composed of some very hard mineral, like quartz,
and occasionally garnet, in the condition of fine, even
grains, cemented to a firm mass. If the grains are some-
what coarse, the stone cuts down instruments rapidly, but
gives a coarse edge. In the best honestones for delicate
instruments, the grain is almost imperceptibly fine. The
finer-grained and stronger portions of grindstone-rock are
wrought into a coarser kind of whetstones for sharpening
farm implements and other tools, in which a fine, smooth
edge is not required. Stones of similar character but
tougher fiber are made from mica schists or slates which
contain, thoroughly disseminated, a large proportion of
fine-grained silica. Such is the rock which is manu-
factured into whetstones in the southern part of Quebec
on Lake Memphremagog, at Bridgewater, Vt., and doubt-
less at other points in regions of mica slates. Whetstones
for finer uses are made from varieties of very fine-grained
silicious slates called nov acuities, some of the most valued
among which are nearly pure quartz in an excessively
minute state of division, and cemented by silica. Such is
the Arkansas or Ouachita oilstone obtained at the Hot
Springs of Arkansas, which, according to two different
analyses, contains from 98 to 99^- per cent of silica. This
rock is of the age of the Lower Carboniferous, and, ac-
cording to Dr. Owen, it owes its snowy whiteness and its
impalpably fine grain to the long-continued action of hot

MATERIALS OF PHYSICAL APPLICATION. 355

silicious waters. The finest of these stones are known to
the trade as Arkansas oilstones, while those of somewhat
coarser grain are sold at much cheaper rates as Ouachita
stones. The Turkish oilstones are also highly esteemed,
their grain being slightly less fine than that of the best
Arkansas stone. The very superior yellow Belgian hone-
stones owe their fine quality to microscopic garnets set in
a garnet paste.

For the grinding of grain, almost any hard, tough,
sharp-grained rock will serve fairly well, and several kinds
of rock of this character have been and still are employed
locally for this purpose, some of which have even more
than a local use. Thus, tough, coarse-grained gneisses,
and some firmly cemented conglomerates, are so em-
ployed. A white, hard, sharp-grained sandstone, of sub-
Carboniferous age, found at Peninsula, O., is used near
where it is found, and also sent elsewhere, for preparing
oatmeal and for pearling barley, for which purposes it ap-
pears to be specially fitted. A basaltic lava, found in
Germany, is used for millstones, especially for grinding
minerals, because of its peculiarities of texture. The
rock, however, which is most suitable for millstones of
any yet known, is a highly cellular quartz-rock called
buhrstone. That which has the highest reputation, and is
most largely used, is obtained from the vicinity of Paris,
France, from rocks of earlier Tertiary age. It is of fresh-
water origin — indeed, often contains great numbers of si-
licified fresh-water shells, and in the best portions the
cellular spaces occupy more than one third the bulk of
the stone. Its superiority is due to its cellular structure
and its hardness. The stone is cut into blocks of proper
form, which are fitted together and held to their place by
iron bands to form millstones. Rock of similar charac-
ter, and in strata of about the same geological age, is
found also in South Carolina, Georgia, and Alabama.
The use of millstones in making flour has been, to a con-

356 APPLIED GEOLOGY.

siderable extent, superseded in large flouring establish-
ments by that of iron rollers ; but for other purposes, and
in most small mills, there is likely to be always a wide de-
mand for stones to be used in grinding. There will be
needed here no more than an allusion to the use of stone
in heavy wheels for pulverizing clays, quartz, and other
minerals as well as ores, and for some pulping purposes ;
and the much ruder use of heavy stone blocks, dragged
round and round on a pavement of stone, for grinding
ores in the arrastra.

For the rapid grinding, cutting, drilling, and polishing
of the harder rocks and minerals and of steel, resort is
had to the hardest of known minerals, the diamond and
corundum, or to the impure and somewhat less hard but
tougher variety of the latter mineral called emery. The
diamond, because of its rarity and great cost, is confined
to special uses. Small crystals and angular fragments are
firmly cemented into handles to be used in cutting and
ruling glass, in drilling and cutting rubies, sapphires, and
some other gems, and for the fine dressing of millstones.
Diamond drills, used for prospecting mineral deposits and
veins at considerable depths, are made by cementing
small diamonds around the edge of a hollow cylinder of
steel. This, being swiftly revolved by machinery, not
only cuts rapidly through rocks, but also enables the
miner to bring up from various depths a solid cylindrical
core of rock for examination. For this purpose, black
diamonds, not suited for jewelry, are used, called borts,
carbons, or carbonados. They are procured, it is said,
chiefly from the Brazilian diamond regions. Other dia-
monds of inferior quality are used for the other purposes
that have been named, or crushed to fine powder to be
used for cutting and polishing the harder gems and the
diamond itself.

The mineral corundum, which is inferior only to the
diamond in hardness, in the condition of transparent crys-

MATERIALS OF PHYSICAL APPLICATION. 357

tals of various colors furnishes the gems sapphire, ruby,
emerald, etc. That which is used as an abrasive is most
commonly gray and imperfectly transparent, and is of no
value as a gem. It has been found in the Appalachian
region of the United States at many localities, the most
important of which are in Clay and Macon Counties, N. C.,
and Chester County, Pa. Masses of corundum are said
to have been found in Clay County, N. C., weighing from
three to six hundred pounds, associated with the olivine
rock of that region. It is estimated that about five hun-
dred tons are produced annually by the United States.
Emery, which is an impure form of corundum contaminated
with varying amounts of iron oxide, whence it derives its
dark color, is obtained chiefly from near Smyrna, in Asia
Minor, where it occurs in considerable masses, and from
the island of Naxos. It has also been mined at Chester,
Mass. Both corundum and emery are pulverized to a
powder of different degrees of fineness for different pur-
poses, and sold, under the name of emery, for polishing
glass and the harder kinds of stone and metals, a large
part of the price at which it is sold being due to the labor
of reducing to fine powder minerals of such hardness.
The powder of emery, though not so hard as that of pure
corundum, and hence not abrading so rapidly, is said to
be less brittle and so more durable. What are called em-
ery-wheels, so largely used in machine-shops for grinding
and polishing iron and steel, are made by mixing powdered
emery into a paste with water-glass, fire-clay, or some other
cementing material, then molding into the proper shape
and baking. Emery-paper is made by cementing emery-
powder to stout paper with glue. Sand-paper, to be used
for polishing wood, is made in like manner from sharp*
quartz sand.

Sand is also largely used -as an abrasive in sawing and
rubbing to a smooth surface marble and sandstone. Other
mineral substances, which are utilized for polishing wood

358 APPLIED GEOLOGY.

and stone, bone and ivory, as also metallic articles, are
pumice and tripoli. Pumice is a light, porous, felspathic
lava which is brought chiefly from the neighborhood of
Mount Vesuvius and the Lipari Islands, but is said to
occur abundantly also in San Francisco County, Cal.
Tripoli is a silicious, infusorial earth of very fine grain
which is found near Richmond, Va., and Monterey, Cal.,
as also in Nevada and at a number of foreign localities.
Tripoli has also been somewhat used as an absorbent of
nitro-glycerine in making dynamite.

Graphic Materials.— What have been thus grouped
in this place are those geological substances which, by
reason of their texture, softness, color, and some other
properties, are used with no other than a mechanical prepa-
ration for making, or for receiving and transferring, draw-
ings and writings. As is well known, great improvements
have been made within the present century in the adapta-
tion of means for these purposes, whereby the multiplica-
tion of writings and of works of art has been greatly facili-
tated and cheapened, to the great advantage of business,
while bringing within the reach of all classes of people
better means for cultivating a refined taste, and for the
illustration of subjects otherwise difficult of comprehen-
sion. Some portion of this improvement has been due to
the discovery, or adaptation and preparation, of geological
substances, such as graphite, chalk, steatite, and litho-
graphic limestone. Graphite, the mode of occurrence and
localities of which have been given in the preceding chap-
ter, has long been used in pencils for drawing and writing,
being sawed into slender prisms from blocks of granular
graphite ; and for this use that of Borrowdale, England,
had a special value, being pure and of granular texture.
Now, however, purified graphite, in a fine state of divis-
ion, is either compressed intp solid masses by hydrostatic
pressure, to be afterward sawed into pencil " leads," or else
mingled into a paste with certain proportions of the finest

MATERIALS OF PHYSICAL APPLICATION. 359

clay, run into molds, dried, and heated to such tempera-
tures as are needful to secure the degrees of hardness
which are requisite for different purposes. Chalk, so
largely used in crayons for school and other purposes, is
a soft, white, earthy limestone, composed of the calcareous
skeletons of microscopic organisms. This forms nearly
the uppermost deposit of rocks of the Cretaceous period
in southern England and northern France, where it covers
considerable areas. Because of its peculiar soft and fria-
ble condition it is easily pulverized and molded into proper
shapes, either alone or mingled with various coloring in-
gredients. Its physical condition fits it also to be used in
some porcelain mixtures, and to be mingled with a proper
proportion of clay for burning into hydraulic cements.
The so-called red chalk, used for graphic purposes, is an
argillaceous ochre, i. e., a soft, earthy form of red iron
oxide mingled intimately with clay, which occurs in re-
gions of iron-ores. The massive granular form of talc,
called steatite and soapstone (see preceding chapter), is
used, under the name of French chalk, for marking on
cloth, and in crayons for drawing in fine white lines on a
dark ground ; and pyrophyllite, a soft, aluminous silicate,
closely resembling talc in its light colors, its softness, and
its greasy feel, is much used for slate-pencils. The latter
occurs in the Archaean slates of Georgia and both Caro-
linas, and near Little Rock, Ark.

The very important graphic material known as litho-
graphic limestone is a very fine-grained, compact, and per-
fectly homogeneous limestone, of conchoid fracture, and
usually of a pale-gray or yellowish tint, and having a suf-
ficient degree of porosity to slightly absorb water and oil.
On the smoothed or finely granulated surface of such a
stone, drawings are executed with a properly prepared
greasy pigment, called lithographic chalk and lithographic
ink, or such drawings may be transferred to it from spe-
cially prepared paper. The stone absorbs the greasy draw-

360 APPLIED GEOLOGY.

ing material sufficiently to retain it firmly, and, if it now
be moistened with water, all except the greasy portions
absorb the water and become wet. A roller charged with
the oily printer's ink, passed over the moistened stone, will
now wet only the greasy lines of the drawing, which may
then be printed from as from an engraving. Limestones
possessed of this peculiar combination of characters are
very rarely met with. Hitherto they have been obtained
wholly from certain thin-bedded limestones of the upper
part of the Jurassic period at Solenhofen, Bavaria, a local-
ity famous also for the remarkably preserved fossils which
it affords. Limestone of the required quality is, however,
reported to occur in strata of the Trenton period in Mar-
mora, Hastings County, Ontario, and in a yellowish dolo-
mite of the Salina period on the Saugeen River in Bruce
County, of the same province. It is said, also, that litho-
graphic limestones in small slabs may be obtained at some
localities in the Lower Carboniferous limestone of Mis-
souri, portions of which, however, are apt to show spots of
different texture, and so to be worthless.

Pigments. — A great majority of the pigments that
are in common use are derived from the metals by chemi-
cal processes, and hence have already been mentioned in
their proper places among the useful applications of the
metals from which they are derived. Such, for example,
are the various pigments manufactured from lead, zinc,
chromium, mercury, arsenic, antimony, copper, and cobalt.
Besides these, however, there are some other substances
which, with no other than a mechanical preparation, are
used as cheap pigments. Thus, graphite, so largely utilized
for other purposes that have been mentioned before, is also
somewhat used as a black paint. Finely pulverized chalk,
under the name of whiting and Spanish white, is used as a
white or tinted wash for walls ; and caustic lime is also
widely employed for the same purpose. Besides these
substances, which have already been described in other

MATERIALS OF PHYSICAL .APPLICATION. 361

connections, ochre, umber, and barytes have a large use as
pigments. Ochre is a soft, pulverulent form of hydrated
peroxide of iron, mingled usually with more or less con-
siderable proportions of clay, silica, and organic matter,
and affording various shades of yellow, red, and brown.
It occurs in deposits of various geological ages, and often
as superficial accumulations of recent periods. Thus, the
softer earthy portions of some hematite beds are ground
and used as pigments, called iron paints. The ochre de-
posits of Great Britain are found chiefly at the base of the
Cretaceous system, while the extensive beds of ochre along
the St. Lawrence in Canada are superficial deposits which,
in some cases, are interstratified with peat, and have been
accumulated by the solvent action on iron compounds of
organic acids resulting from vegetable decomposition, and
the subsequent deposition of the iron oxide by atmospheric
oxidation. Ochre is procured also from the muddy fer-
ruginous waters pumped from mines. Its color may be
greatly modified by calcination, thus driving off its water
of hydration. Beds of red and reddish-brown clay-rocks,
colored by iron oxide, are also ground and used as a cheap
paint. Umber is a soft, earthy variety of ochre, which is
colored brown by oxide of manganese, and becomes red-
dish brown by calcination. It occurs usually in crystalline
rocks, and is brought mostly from the island of Cyprus.
It is found, also, at a few localities in Great Britain, and
is said to be produced to some extent in this country.

The mineral barytes, called also heavy spar, because of
its great specific gravity, is a white crystalline or massive
sulphate of baryta, of about the same hardness as calcite,
and is fusible by the blow-pipe, giving a green color to the
flame. On account of its great weight, it is little liable to
be mistaken for any other white mineral save celestite,
which has nearly the same weight and hardness ; and from
this, the color imparted to the blow-pipe flame readily dis-
tinguishes it, that of celestite being a bright red. It oc-

362 APPLIED GEOLOGY.

curs commonly as a vein-stone, especially in veins of lead
and copper. It is found in workable quantities at quite a
number of localities in North America ; as in the copper
veins on the north shore of Lake Superior ; in the central
Missouri lead region, especially in Miller and Morgan
Counties; in several counties of East Tennessee, being
worked in some; and in Wythe, Smyth, and Campbell
Counties, Va., a single mine in the county last named be-
ing reported to be able to produce a hundred tons per
day. Considerable amounts are produced also in Penn-
sylvania and Maine. The largest production is from
Missouri and Virginia ; Connecticut grinds also a large
amount of barytes imported from Germany. About
twenty-five thousand tons a year are mined in the United
States, of which much the largest part is used for mixing
with white lead and zinc white, in the preparation of
white paint. This employment of barytes is commonly
considered an adulteration, and manufacturers do not
seem eager to publish the fact of its use ; yet, when
properly prepared, it produces a good opaque white color,
which is not, like lead, liable to discoloration from sul-
phuretted hydrogen.

Lubricators. — The mineral substances which are
most largely employed for diminishing friction in ma-
chinery, viz., graphite and the heavy varieties of petroleum,
have already been mentioned in other connections as fitted
for this use. The foliated varieties of talc, when free from
needles and grains of the harder minerals, are also used to
a considerable extent in lubricating compositions. This
last-named mineral, which, like soapstone, its massive form
from which it is distinguished commercially, occurs in
crystalline schists, is found in several of the States of the
Atlantic border — most largely in Georgia, Pennsylvania,
New York, and Vermont. The fibrous form of this miner-
al, which is found in considerable quantities near Gouver-
neur, N. Y., is quite largely mined and ground for pulp to

tSE-

MATERIALS OF PHYSICAL APPLICA%$^ \^'

'•

be used in paper-making. It may readily be judged that
only the fibrous variety could be used for this purpose,
since only this has any staple to form a felt ; and the St.
Lawrence mineral may, it is said, enter into printing paper
to the extent of twenty per cent, or even more. Talc has
also a quite extensive use in soap-making, and in dressing
skins and leather, these various applications rendering it a
mineral of considerable economic importance. In the
" Geological Report on the Midland Counties of North
Carolina," 1856, Prof. Emmons speaks of a valuable anti-
friction hornstone as abounding in several counties of
that State. This rock, probably a felstone, since it gradu-
ated into porphyry, was of flinty aspect and very fine and
compact texture, and was highly valued locally as a bear-
ing for the axles of heavy wheels. From its fine texture
and great hardness, this distinguished geologist pro-
nounced it to be fitted to take the same part in diminish-
ing the friction of heavy machinery that rubies play in the
works of watches.

Molding-Sand. — This substance, which is of so
much importance for foundry use, is an intimate mixture
of quartz sand with just sufficient proportions of clay and
• ochre to enable it to retain the form given by the pattern,
and to withstand in founding the current of molten metal
without displacement. If the proportions of the cohesive
substance are too small, even if the mold retains its form
before it is used, it is apt to wash, i. e., to be swept away
in places by the flowing metal, and so to cause irregulari-
ties in the casting, or to ruin it wholly. If, on the other
hand, there is more clay than is needed, it is burned in the
founding, and forms a crust on the casting which is some-
what troublesome to remove. A good sand for molder's
use should contain about 92 per cent of fine quartz sand,
6 per cent of clay, and 2 per cent of iron oxide. The
fineness and delicacy of the impression that can be given
will depend on the fineness of the sand that is present in

364 APPLIED GEOLOGY.

the molding mixture. For some very fine castings, an
artificial mixture is prepared by calcining loamy sand,
grinding it very fine, and adding some substance to impart
the necessary adhesiveness. Good molding-sand is of a
yellow color, soils the fingers when dry, and when damp,
if grasped in the hand, it retains a delicate impression of
the fingers. It occurs in superficial deposits, usually of
no great thickness, and is liable to great variations in
quality at points little removed from each other. Mold-
ing-sand is by no means of common occurrence, and the
foundries of very considerable sections of country are
often obliged to depend for their supplies on material
brought from a distance. Saratoga County, N. Y., fur-
nishes a molding-sand of fine reputation and of various
qualities fitted for special purposes, which is transported
to long distances. Good sand for this purpose is found
at some localities in New Jersey, from which supplies are
sent to the Southern seaboard States. Tompkins County,
N. Y., has a fair quality of sand which supplies the local
demand for ordinary foundry uses. For some purposes,
as for large castings in bronze, molding-sand is even im-
ported from Europe. For the facing of molds, called
foundry facings, graphite is largely used, as has already
been said. A cheaper facing, and one which, for some
purposes at least, is less liable to wash, is afforded by
hydraulic lime.

CHAPTER XXII.

ORNAMENTAL STONES AND GEMS.

A TREATISE which is intended to present any just view
of the contributions which geology makes to the supply of
the multifarious wants of mankind, can not omit some ac-
count of those substances which, while not ministering to
man's necessities, nor promoting his comfort, nor increas-
ing the efficiency of his efforts, are nevertheless strongly
desired by him as a gratification to his tastes, as the ex-
pression of his wealth and social consequence, or as fitted
to be fashioned into the most permanent monuments of
his culture and refinement ; objects which, though not
necessary, are yet essential, because without them some-
thing would be lacking for the complete satisfaction of his
many-sided nature. Man loves beauty and craves orna-
ment, and all that ministers to this sentiment and craving
is more elevating in its tendency than what satisfies merely
his bodily wants. Many of the substances which are
drawn from geological sources lend themselves to these
higher wants of mankind by their durability, combined
with their beauty, their brilliancy of color or of luster, and
often their rarity. Several of them are found in consider-
able abundance, and a great part of the estimation in
which they are held is due to their adaptation to the pur-
poses of refined and artistic workmanship. Such are the
ornamental stones, the objects wrought from which usually
far surpass the raw material in value. Others add to

366 APPLIED GEOLOGY.

beauty of color and brilliancy of luster a greater or less
degree of hardness and of rarity, and, while gratifying the
taste of their possessor, become in a certain degree badges
of his wealth and importance. Such are the gems, a large
part of whose value is usually intrinsic, i. e., dependent in
but a minor degree on excellence of workmanship.

Ornamental Stones.— On account of the hardness
and unalterability of the mineral, the various forms of
quartz have, for many centuries, been used for ornamental
purposes. The transparent varieties were fashioned by the
ancients into crystal cups and vases, and set in jewelry.
Its use for most such purposes is now largely superseded
by that of the finer kinds of glass, which are more brilliant
and cheaply formed, but more liable to be marred in use
because of their inferior hardness. Clear white quartz has
a considerable use in lenses and for spectacles ; and un-
der such names as Rhine-stone and California diamond,
quartz is still quite largely cut and polished for cheap
jewelry, that which is of a clear yellow color figuring as
false topaz, and that of a smoky tint as Cairngorm-stone.
The purple variety of quartz called amethyst, when trans-
parent crystals of sufficient size and proper depth of color
are met with, is cut for valuable jewelry. Much, however,
that is sold under these various names is artificial, being
made from strass. Handsome crystals and clusters of
crystals of quartz are held in some estimation as house-
hold ornaments. Fine specimens for this purpose are
found at the Hot Springs of Arkansas, and in Herkimer
County, N. Y. ; as also frequently in regions of Archaean
rocks. The most valued amethysts are brought from
India, Ceylon, Siberia, and Brazil ; and they are found
also on Keweenaw Point, and in some of the Eastern
States, but seldom good enough for jewelry. The massive
translucent varieties of quartz with waxy luster, and es-
pecially those which present alternating bands and spots
of different colors and shades of color, due to impurities

ORNAMENTAL STONES AND GEMS. 367

introduced during the successive deposition of the layers
from silicated waters, make very handsome ornamental
stones, and are wrought into a variety of beautiful objects,
such as vases, cups, boxes, necklaces, seals, buttons, knife-
handles, and small columns for cabinets ; or they are
merely cut and polished to display their spots and bands
of color, and used for mantel and cabinet ornaments.
Varieties of milky and bluish tints are called chalcedony,
abundant in geodes in Iowa and Illinois ; of bright, rich
red, carnelian, brought from the East Indies ; of concen-
tric and often zigzag bands of color, agates, found on Lake
Superior ; of smoky tints, containing moss-like figures in
metallic oxides, moss-agates, occurring in the Rocky
Mountain region ; and of flat, parallel layers of white and
black or brownish shades, onyx and sardonyx. These last
are the materials in which are cut miniature articles of
sculpture called cameos, in which the alternation of layers
of different colors is dexterously made to heighten the
effect, and in the art of cutting which the ancients had
attained as great skill as is displayed by modern artists.
The opaque red, yellow, and green variety of quartz, called
jasper, when it occurs in bands of different colors, is val-
ued for ornaments like vases, handles, boxes, and small
cabinets, and especially for mosaics and inlaid work.
Handsome varieties are found in Calaveras County, Cal. ;
Graham County, Kan. ; near Troy, N. Y. ; and at Chester,
Mass.

Some of the varieties of feldspar also afford orna-
mental material. Thus sunstone, a yellowish or grayish
feldspar, containing minute scales of mica, and moonstone,
a milky opalescent feldspar with pearly reflections, are cut
for jewelry ; and labradorite, a dark-gray or brown feld-
spar, which when polished often presents a beautiful play
of bright bluish and greenish colors from internal reflec-
tions, is a handsome material for ornamental uses. The
last-named mineral is obtained of good quality from Lab-

368 APPLIED GEOLOGY.

rador, whence its name, being also found in northern
New York ; while the first two occur in Amelia County,
Va., and Delaware County, Pa. Moonstone is brought
also from Ceylon, and sunstone from Norway. The feld-
spars used for ornament occur in regions of .crystalline
rocks. The tough, heavy, compact, and translucent stone,
called nephrite and jade, of green and blue colors, obtained
from China, India, Siberia, Alaska, and New Zealand, is
used for making carved ornaments, for which purpose it
has long been held in high estimation by the Chinese.
Lapis lazuli, a mineral usually compact and of rich blue
color, occurring in the ancient crystalline rocks of Persia,
China, Siberia, and Thibet, furnishes a valued material for
objects of luxury, like vases, rich mosaics, and the inlaid
work of costly furniture, besides being used in jewelry.
When powdered, it becomes the costly blue pigment,
ultramarine, which is now, however, prepared artificially
at much smaller expense than that from the native min-
eral.

The use of malachite, the green banded carbonate of
copper, in magnificent inlaid furniture, has already been
mentioned in the chapter on copper. It is a common ore
of copper in our Southwest Territories ; but large concre-
tionary masses, fit to be cut for ornamental uses, are not
often met with, the Ural Mountains being still the chief
source of supply for such purposes.

The fluoride of calcium, called fluor-spar and Derby-
shire spar, which occurs both massive and crystalline as a
vein-stone in many veins, especially those of lead, when
transparent, and of fine colors, such as green, purple, and
red, is sometimes wrought into ornamental articles, like
vases, snuff-boxes, and candlesticks. Derbyshire, England,
affords a handsome blue fluorite, whence the mineral has
derived one of its common names. Fluorite fit for orna-
mental uses is said to be found in Hardin County, 111.,
and in Colorado. The chief use of the mineral, however,

ORNAMENTAL STONES AND GEMS. 369

is for a flux in metallurgical operations, and as a glaze for
pottery. A hard, compact, and lustrous variety of brown
coal, which admits of a high polish, is used on this ac-
count, and because of its black color, for personal orna-
ments, especially mourning jewelry, under the name oijet.
It occurs abundantly in El Paso County, Col., and at
some localities in Texas ; also in England (Whitby be-
ing a celebrated locality), in France, and in Spain. Like
the lignites and brown coals, jet occurs in the later geo-
logical deposits, the Tertiary and Upper Cretaceous ; and
like these, also, it is very light when compared with other
minerals, by which character it may easily be distinguished
from its imitations made of glass.

Another very light mineral substance, largely used for
small ornamental objects, is amber, a transparent fossil
resin of yellow and orange colors, frequently inclosing in-
sects. It occurs in irregular lumps in the Tertiary beds
of several European and Asiatic localities, and on the
Atlantic borders of Massachusetts and New Jersey ; but
much the most important source of supply is the Baltic
coast, chiefly of Prussia, where it is washed out of its con-
.taining strata and thrown on the shore by the action of
the waves. It is manufactured into ornaments for the
person, such as ear-pendants, bracelets, necklaces, and
brooches, and into boxes, mouth-pieces for pipes, and han-
dles for canes and paper-knives. As its weight is less
than half that of an equal bulk of glass, this character, as
well as its softness, affords an easy means of distinguishing
it from imitations.

The ornamental employment of marbles in the interior
decoration of houses has already been mentioned under
building-stones ; but, aside from this, a large use of mar-
bles of fine texture and pleasing and varied colors is made
in the ornamentation of articles of furniture and in sculpt-
ure, one of the noblest of the fine arts. For the latter
purpose marble is required which is of fine and even text-

370 APPLIED GEOLOGY.

lire, free from any foreign minerals, and of a pure and
uniform white color. Such marble is of rare occurrence,
and hence the celebrity of some of the marbles of Italy
and Greece, those of Carrara and Paros. What is called
onyx marble is a translucent stalagmite, prettily banded
with different light shades, and obtainable in masses of
considerable size. It is a beautiful material for ornamental
purposes, and may be wrought into many pleasing objects.
Attention has recently been called to it by large specimens
from Algiers and Mexico, exhibited at some of the World's
Expositions. Alabaster, a compact, translucent variety of
gypsum, and verd-antique marble, a rock composed of green
serpentine and white calcite, are also used in ornamental
work.

Mention should also be made here of the porphyries,
hard and tough varieties of rock, made up of a very fine-
textured felspathic base inclosing well-defined crystals*
usually of feldspar. Where the base and inclosed crystals
are of pleasing and finely contrasted colors, as dark red,
green, and white, this rock, from its susceptibility to high
polish, has in all ages been an admired material for orna-
mental objects, such as vases, caskets, columns, parts of
furniture, and handles of knives. The antique red and
green porphyries have an ancient celebrity. As porphyry
is of volcanic origin, its geological position is naturally in
dikes ; and material suitable for ornamental uses is more
likely to occur in those which cut rocks of great geological
antiquity.

Gems. — The minerals which, from their transparent
brilliancy, their beauty of color, and their hardness, coup-
led with their rarity, are held in esteem as gems are but
few in number, not more than a dozen in all. They are
the diamond, corundum, spinel, topaz, beryl, zircon, gar-
net, tourmaline, spodumene, turquoise, and opal, some even
of these holding but a doubtful place in a list of gems,
although occasional examples of uncommon size and beau-

ORNAMENTAL STONES AND GEMS. 371

ty sell at a considerable price. Of these, only the trans-
parent varieties, and those of pleasing and uniform colors,
have any considerable value as gems, some others being
utilized on account of their hardness, like the black dia-
mond and bort, and the gray and black corundum, or
being valued merely as mineralogical specimens. With
the exception of the opal, which occurs in nests and veins
in volcanic rocks like the rhyolites, all the gems have their
birthplace in the ancient crystalline rocks, although several
are most commonly met with in alluvial deposits formed
from the ground-up and assorted debris of such rocks.
Where used as gems, all are transparent save turquoise,
which is opaque, and opal, which is usually merely trans-
lucent. They range in hardness from the diamond and
corundum, which scratch all other minerals, to opal and
turquoise, which may be scratched by quartz ; all but the
last two can therefore be easily distinguished from their
glass imitations by their superior hardness, since that of
the brilliant variety of glass called strass or paste, from
which imitation gems are made, is not more than 5 on
the scale of hardness, while that of the softest gems is 6,
and of quartz 7. Hardness is essential in gems, since,
though entailing greater expense in cutting, it preserves
their colors and polish undimmed for ages. A few of the
gems are colorless, like the diamond, and occasionally the
topaz and zircon ; but most of them present various clear
shades of red, green, blue, and yellow ; and some of them,
like corundum and beryl, afford gems of several different
colors which bear different names. The carat, in which
the weight of many precious stones is reckoned, is a con-
ventional weight, equal, according to Ure, to about 3.88
grains troy, although sometimes used as no more than 3.1
grains. Gems are cut, according to their nature and shape,
in four different styles, of which the brilliant consists of a
truncated double pyramid, the truncated ends being octa-
gons, and the sides made up of a combination of triangular

372 APPLIED GEOLOGY.

and rhomboid or pentagonal facets ; the rose cut has a
flat base surmounted by a pyramidal dome, made up usu-
ally of twenty-four triangular facets ; the table has a rect-
angular face and beveled edges ; and the en cabochon cut
has a flat base and smooth, rounded dome.

As is well known, the diamond is the most highly val-
ued of the gems. This mineral, which is pure crystallized
carbon, the same element which in other conditions con-
stitutes charcoal and graphite, is the hardest of all known
substances, readily scratching every other mineral and
being scratched by none. The peculiar charm of the dia-
mond lies in its singular brilliancy of luster, in which it as
far surpasses all other gems as it does in hardness, and
which depends on the great refractive and dispersive
power that it exerts on the rays of light. The diamond
is usually colorless, but has not unfrequently a slight tinge
of color, of which yellow is the most common and least
esteemed. A diamond of the first water is perfectly trans-
parent and colorless, and free from spots or flaws, those
of clear green and rose tints being also very highly prized.
Diamonds are occasionally found of considerable size :
the largest from South Africa weighed 308 carats, the
largest from Brazil 254!- carats, and one is mentioned from
India which is said to have weighed originally 900 carats.
Those weighing more than twenty carats are rarely met
with, the vast majority of those found being much smaller
than this ; and they lose, on the average, about one half
their weight in cutting and polishing — operations which
can be performed only by the aid of the powder of the
diamond itself. The diamond has very rarely been found
in any other than alluvial deposits made up probably of
the debris of its original rocky matrix ; so that there has
been much conjecture as to the nature of the formations
in which it originated. In Brazil it is found in a peculiar
rounded gravel of milky quartz, associated with coarse
ferruginous sand, called by the miners cascalho. This may

ORNAMENTAL STONES AND GEMS. 373

have been derived from a ferruginous conglomerate, or,
more probably, it is thought, from a laminated and some-
times slightly flexible quartzite called itacolumite, which
belongs to the ancient crystalline series of that country.
In India, where its mode of occurrence is said to be simi-
lar to that in Brazil, a French geologist, M. Chaper, has
recently found the diamond in situ, associated with corun-
dum, in a matrix of rose-colored pegmatite, a variety of
granite, the granitic rocks in the vicinity of the gems being
traversed by veins of feldspar and epidotiferous quartz ;
thus we have reliable information of one mode of original
occurrence of this gem, if not the only one. The great
diamond-producing regions of the world are three in num-
ber, viz., the southern part of Hindostan, Brazil, and South
Africa. The diamond region of the Indian Peninsula has
been known from a remote antiquity, and from it have
been derived most of the famous diamonds which are
among the crown jewels of European sovereigns. The
Brazilian diamond-fields are chiefly in the provinces of
Minas-Geraes and Bahia, north of Rio Janeiro, though
gems are found also in Parana, Goyaz, and Matto-Grosso.
The black diamonds, or carbonados, mentioned in the pre-
ceding chapter, are found in Bahia. The Brazilian prod-
uct is said to amount to from forty to fifty pounds troy
per annum. The latest discovered and most prolific re-
gion is that of Griqualand and the Orange Free State in
South Africa, of which Kimberley is the center, and which
has been known only since 1867. The workings here ex-
tend to the depth of some hundreds of feet, and the value
of the product for 1881 is said to have been about $22,-
000,000. Besides these chief regions, diamonds are found
in the Ural Mountains and in Borneo, and a few isolated
occurrences have been noted in the United States — in
Georgia, North Carolina, Virginia, and California.

Corundum, which ranks next to the diamond in hard-
ness, is pure crystallized alumina, and, when occurring in
IT

374 APPLIED GEOLOGY.

transparent crystals of pure colors, yields gems which rank
next to the diamond in value, and which receive different
names in jewelry according to the colors that they present.
Thus, the transparent blue corundum is called sapphire j
the red, oriental ruby ; the green, oriental emerald; the
violet, oriental amethyst j and the yellow, oriental topaz —
white stones also occurring which have passed for dia-
monds. While the original matrix of these gems, like
that of ordinary corundum, is in crystalline rocks, they are
most frequently found in alluvial deposits. The finest
stones are obtained mostly from the East Indies, some be-
ing found also in Saxony, Bohemia, and France. Gems of
the corundum species are found occasionally in North
Carolina ;' also in southern Colorado, New Mexico, and
Arizona, in sand with garnets.

The spinel is a mineral composed of alumina and mag-
nesia, with usually a little iron, is in hardness next below
corundum, by which it may be scratched, and when used
as a gem is of a fine rosy red color, though green and violet
tints also occur. This gem, which is called by jewelers
spinel ruby and balas ruby, is obtained chiefly from Siam
and Ceylon, where it occurs in crystalline rocks, but most-
ly in alluvial deposits derived from their wear. Spinel is
also found in Sussex County, N. J., and Orange County,
N. Y., sometimes in crystals of large size, but rarely if ever
fit for jewelry.

The topaz, which is a silicate of alumina containing
a considerable proportion of fluorine, occurs in rhombic
prisms with perfect cleavage across the prism, has a hard-
ness about equal to that of spinel, and its color is most
commonly yellow, but sometimes green, blue, and white.
Like the other gems, it occurs in crystalline rocks, or in
their cttbris. Those used in jewelry are mostly brought
from Siberia, Kamchatka, and Brazil ; it is found also in
Saxony and Bohemia, in Arizona and New Mexico, and
on Pike's Peak ; the last-named locality, which has recent-

ORNAMENTAL STONES AND GEMS. 375

ly been discovered, gives promise, it is said, of yielding
a light-blue topaz which will be valuable for gems — color-
less and pellucid crystals being also found.

Beryl, a silicate of alumina and glucina, which occurs
in six-sided prisms, sometimes of great size, in the crystal-
line rocks of some of the Eastern States, when transparent
and of fine colors affords the valuable green gem, emerald,
the sea-green or bluish aqua marine, and the yellow or
light-green beryl. Its hardness is somewhat less than
that of the spinel and topaz, by which it may be scratched.
Crystals fit for jewelry are sometimes found in New
England and in Alexander County, N. C., but the emerald
and aqua marine are mostly obtained from New Granada,
Brazil, Hindostan, and Siberia.

Zircon, the silicate of zirconia, transparent red crystals
of which constitute the gem called hyacinth, and colorless
or smoky ones, the jargoon, although found in crystalline
rocks at several localities in North Carolina, New York,
and New England, has not yet afforded any valuable gems
in the United States. These are derived from Ceylon,
which furnishes so many other gems, from Siberia, Green-
land, and some European localities. The hardness of zir-
con is about the same as that of beryl, and exceeds that
of quartz.

The garnet, which is a silicate of quite variable com-
position, is of about the same hardness as quartz ; and
though of quite common occurrence in mica schist, horn-
blende schist, and some other crystalline rocks, still, clear
red crystals of proper size are held in some estimation
as gems. Stones of the finest quality are found in south-
ern Colorado, New Mexico, and Arizona, excellent ones
being also obtained from Greenland and Ceylon. It is
usually cut in thin tables, or low, rounded forms.

The tourmaline is a variable compound of silica, alumi-
na, and boracic acid, with several other substances. It oc-
curs in prisms, usually black, of three, six, nine, or twelve

376 APPLIED GEOLOGY.

sides, with a low, three-sided pyramidal end, has about the
same hardness as quartz, and is found as a common acces-
sory of various ancient crystalline rocks. It is occasion-
ally met with in transparent crystals of clear yellow, green,
blue, and pink colors, when it becomes a gem of consider-
able value. Fine yellow gems of this mineral are obtained
from Ceylon, and sold often as topaz. Paris, in Oxford
County, Me., is a celebrated locality for tourmaline gems
of various colors, yielding, it is said, more than two thou-
sand dollars' worth per year ; and two or three other lo-
calities in the vicinity of Paris give promise of yielding
similar gem-stones.

Hiddenite, or lithia emerald, a variety of spodumene,
and composed of silica, alumina, and lithia, is a gem re-
cently discovered at Stony Point, Alexander County, N. C.,
where it occurs in small open pockets in gneiss-rock, asso-
ciated with emeralds and several other crystallized min-
erals. The most valued gems are of a brilliant grass-green
color, those of light-green and yellow colors as well as
colorless being also found, but held in less esteem. Ac-
cording to its discoverer, the gem has a brilliant cleav-
age, and is somewhat harder than the emerald. The lo-
cality is being diligently explored for the mineral, which
is in good demand for cabinet specimens as well as for
gems.

Turquoise is a hydrous phosphate of alumina, opaque,
of a delicate blue or bluish-green color, due to copper, and
of a hardness inferior to that of quartz. Despite its in-
ferior hardness and opacity, it has long been held in esteem
as a gem, because of its pleasing color and the beautiful
combinations that it makes when cut with a smooth,
rounded surface and set with diamonds or pearls. It
occurs in small, rounded masses, or in thin veinlets trav-
ersing eruptive or crystalline rocks. The best has for
ages been obtained from Khorassan, a province of Persia.
Attention has recently been called to two localities of this

ORNAMENTAL STONES AND GEMS. 377

mineral that were largely worked by the ancient Mexicans,
among whom, at the time of the Spanish conquest, it was
highly prized as a gem under the name of chalchihuitl, or
chalchuite. One of these localities, showing old workings
of vast extent, is in the Los Cerillos Mountains, twenty
miles southeast of Santa Fe, and the other in Cochise
County, Arizona. The mineral at both these localities is
bluish green. It has also been found at a locality in south-
ern Nevada of a rich blue color, disseminated in grains in
a hard sandstone, which is polished and makes a beautiful
mottled stone for jewelry.

Opal is a peculiar, massive, uncrystalline form of quartz,
containing a variable proportion of water, somewhat softer
than crystalline quartz, by which it may be scratched, and
also of a lower specific gravity, its weight rarely exceeding
2.2 that of water, while that of quartz is about 2.65. When
used as a gem it is translucent, and usually of a milky
color, and presents a vivid, iridescent play of colors, due
to internal reflections with decomposition of the luminous
rays, by microscopic laminae. (Zirkel, " Die mikrosko-
pische Beschaffenheit der Mineralien," etc., p. 116.) To
this charming opalescence, which is best displayed when
the gem is cut with a smooth convex surface, it owes the
high estimation in which it was held by the ancients not
less than by modern nations. It occurs in small nests and
thin veins traversing certain volcanic rocks. The precious
opal, and the girasol, or fire opal, have not yet been found
fit for jewelry in the United States. They are obtained
from Hungary, Honduras, and Mexico, and to some ex-
tent from the Faroe Islands.

Besides the minerals here briefly described as precious
stones, some others are occasionally used in jewelry, for
example, chrysoberyl, kyanite, idocrase, and chrysolite ;
of which it will be sufficient to say that the first named,
which nearly equals corundum in hardness, is a valuable
gem in the rare cases when it is transparent and free from

378

APPLIED GEOLOGY.

flaws ; and that chrysolite is in some demand because of
its olive-green tint.

Although most of the gems are by nature singularly
indestructible, still, from the comparative unfrequency of
the occurrence of stones suitable for gems of the first qual-
ity, it may be doubted whether the increase in the supply
more than keeps pace with the increase in wealth and lux-
ury, and with the consequent disposition to acquire precious
stones. Even the recent large increase in the supply of
diamonds, resulting from the discoveries in South Africa,
does not appear yet to have produced any perceptible
effect in diminishing their price as gems. The demand for
several of the precious stones is indeed subject to the ca-
prices of fashion, like that for most things which are objects
of taste and preference rather than of necessity. Hence
occur temporary fluctuations in their price, which bear
little or no relation to variations of supply. Yet, on the
whole, these minor fluctuations serve but to accentuate
more sharply the fixedness and constancy of the passion
for the more indestructible gems, showing how unchange-
able is the principle of human nature in which it has its
roots.

INDEX.

Abrasive substances, 352.
Accessibility of deposits, 46.
Agate, 367.

Age of rocks, 36, 40, 42.
Agordo, pyrites, 299.
Agriculture, geologic relations,

101.

Alabaster, 370.

Alkalies, geological sources, 309.
Almaden, mercury, 259.
Alston Moor, 246.
Aluminium, 290.
Alum shales, 315.

sources, 315.

uses, 316.
Alunite, 315.
Amber, 369.
Amethyst, 366.

Oriental, 374.
Amphibolite, 22.
Amygdaloidal texture, 14.
Analyses of soils, 116.
Ancient workings of deposits, 214.
Anglesite, 242.
Anthracite coal, 19, 137.
Anticlinal, 30.

Anti-friction hornstone, 363.
Antimony, 288.
Aphanitic, 14.
Aplite, 23, 325.
Aqua marine, 375.
Archaean rocks, where found, 81.
Arenaceous, 8.
Argillaceous, 8.

sandstone, 15.
Arrangement of rocks, 27.

vein contents, 201.
Arsenic, 292.

Arsenical ores, 185.

Artesian wells, 58, 60.

Asbestus, needful qualities, 344,

345.

uses, 346.
Ash in coals, 156.
Ashes of plants, analyses, 113.
Asphalt, 352.
Associations of ores, 186.
Atlanta vein, Idaho, 267.
Augite, 6.
Australia, 238, 256, 276, 280.

Banca, tin, 256.

Banded structure of veins, 202.

Barytes, 361.

Basalt, 23, 350.

Basic lining of converters, 229.

Basins of coal, 147.

Bassick mine, Col, 202, 266, 274.

Bauxite, 290.

Beauty of building-stones, 75.

Bedded deposits of ores, 189, 191.

structure, 48.
Belgium, zinc, 251.
Beryl, 375.
Billiton, tin, 256.
Bismuth, 289.

Bituminous coal, 21, 138, 140.
Black-band ore, 17, 143, 225.
Black Hills, 255, 279.
Blanket lodes, 195.
Blende, 248.
Block coal, 139.
Bonanzas, 203.
Borax, occurrence and uses, 312,

314.
Bornite, 232.

INDEX.

Bort, 356.

Breccia, 16.

Brecciated vein structure, 202.

Brick clays, 92, 93.

kiln, perpetual, 95.
Brown coal, 139.
Bruce mine, 233.

Building -stones, desirable quali-
ties, 66.

choice of, 78.

distribution of, 80.

essential qualities, 66, 67.

of America, 80.
Bull Domingo mine, 266.
Butte City, 233, 235.

Calamine, 248.
Calaverite, 274.
Calcareous, 8.

tuff, 16.
Calciferous period, hydraulic lime,

99.

Calcite, 5, 7.
California, 258, 278, 313.
Caking coal, 138, 140.
Cameos, 367.

Canadian period, limestone, 89.
Cannel coal, 20, 139, 140.
Capelton, Quebec, 237.
Carat, 371.
Carbonate ores, 185.
Carbons, 356, 373.
Carboniferous, subdivisions, 148.
Carnallite, 289.
Carnelian, 367.
Cassiterite, 254.
Cement, hydraulic, 19, 97, 359.
Cerussite, 242.
Chalcedony, 367.
Chalchuite, 377.
Chalcocite, 232.
Chalcopyrite, 231.
Chalk, 19, 359.
Chamber deposits, 189, 195.
Characteristics of fissure veins,

203.
Chemical manufacture, geological

materials of, 296.
Chemical sediments, 16.
Chemung period, sandstone, 88.
Cherry coal, 20, 138, 140.
Chili, copper, 238.
Chimneys of ore, 203.

Chloride ore, 185.
Chlorite, 7.

schist, 22.
Chromium, 290.
Chrysocolla, 233.
Classes of rocks, table, II.
Clay, 8, 92, 320.

ironstone, 17, 225.
Clay County, Ala., tin, 255.
Clays, origin, 325.

pottery, 321, 326.

properties, 322.
Cliff mine, 233.
Clifton District, Arizona, 236.
Clinometer, 29.
Coal, adaptation to uses, i5i.

analyses, 141.

American regions, 149, 156.

foreign regions, 153.

fuel value, 159.

geologic associations, 142.

geologic horizons, 148, 149.

impurities, 156.

kinds, 19, 137.

origin, 19, 135.

pipes, 144.

product of 1881, 155.

relative thickness, 146.
Cobalt, 288.
Coke, 162.

Cold-shortness of iron, 158, 228.
Colorados, 209.
Coloring for glass and pottery,

329, 332.

Columbus Marsh, borax, 313.
Columnar structure, 13.
Commern, 193, 242, 246.
Compact texture, 14.
Complications of ores, 186.
Comstock vein, 200, 203, 205,

267.

Concentration of ores, 188.
Concrete for paths, 351.
Concretionary structure, 13.
Conditions of ore deposits, 211,

212.

Conformability of strata, 33.
Conglomerate, 16, 348.
Consolidation, means of, n, 67,

70.
Contact deposits, 195.

veins, 205.
Cool limes, 19, 96.

INDEX.

381

Copper, forms of deposit, 233.

glance, 232.

ores, 231.

production, 239.

uses, 240.

Copper Queen mine, 233, 236.
Corniferous period, limestone, 90.
Cornwall, tin, 255, 256.
Corundum, 356, 373.
Country rock, 36, 196, 199.
Cretaceous coals, 149, 151.
Cryolite, 290.
Cuba, copper, 237.
Cuprite, 232.

Denudation, 33.

Derbyshire, lead, 246.

Derbyshire spar. See Fluorite, 368.

Diamond, 356, 372.

Diabase, 23.

Dikes, 35.

Dip of rocks, 29.

effect on accessibility, 46.

on ease of extraction, 48.
Diorite, 23.

Dinas brick (silicious brick), 337.
Distribution of ore deposits, 211.

of ores in deposits, 203.
Dolerite, 23.
Dolomite, 7, 19.
Drainage, agricultural, 127.

dependence on structure, 64.

sanitary, 132.

Dressing of stone, effects, 77.
Driven wells, 57.
Druses, 202.
Ducktown copper, 237.
Durability of building-stones, 70.

Earth-worms, agency in soils,

108.

Economic geology defined, 44.
Elasticity in building-stones, 68.
Emerald, beryl, 375.

Oriental, 374.
Emery, 356, 357.

wheels, 357.
England, 153, 238, 246, 251,

255-

Erroneous ideas regarding ore de-
posits, 219.

Eureka District, Nev., 210, 244.

Excavations, 49.

Facility of dressing building-
stones, 76.

Fahlun, Sweden, pyrites, 299.
False or current bedding, 28.
Faults, 31, 206, 297.

effect on accessibility, 47.
Feldspar, 6, 328, 367.
Felsite, 23.
Ferruginous, 8.
Fertilizers, geological, 118.
Fertilizing ingredients of soils,

114, 116.

Fictile materials, 319.
Filling of veins, etc., 200.
Fire-clay under coal-seams, 143.
Fire-clays, composition, 335, 336.

tests of, 335.

uses, 337.
Fire opal, 377.
Fire-stones, 338.
Fissures, how formed, 197, 199.
Fissure-veins, 189, 197.
Flagging-stones, 16, 351.
Flats, 195.
Floating brick, 339.
Flucan, 204.
Fluor-spar, fluorite, 368.
Foliation, 12.
Foot-wall, 199.
Forms of ore deposits, 189.
Fossils, 28.

use of, 38.
Foundations, dependence on

structure, 51.
Foundry facings, 364.
Franklin, N. J., 249, 251.
Franklinite, 249.
Freestone, 16.
French chalk, 359.
Fuels, mineral, 135.

Galena, 241.

Galena District, 242, 244, 250.

Gangues, 183, 187.

Canister, 338.

Garnet, 375.

Gas, natural, 166, 180.

Gems, 365, 366, 370.

forms in which cut, 371.
Genesee and Huron shale, 180.
Geology, practical purposes, I.

theoretic objects, I.
Georgetown, Col., 243, 249, 266.

382

INDEX.

Germany, Commern, lead, 246.
Gilpin County, Col., gold, 274, 279.
Girasol, 377.
Glacial agencies in soils, 105.

materials, nature, etc., 107.
Glass, 330, 333.
Glazes of pottery, 329.
Globe, Arizona, 233, 236.
Gneiss, 20.

Gold Hill, Col., tellurides, 274.
Gold, extraction of, 282.

modes of occurrence, 274.

production, tables, 277, 278.

regions, 277.

surface appearance of deposits,
210. .

uses of, table, 281, 282.

value, table, 282.
Goslar, pyrites, 233, 299.
Gossan, 209.
Gouge, 204.
Granite, 22, 26, 82.
Granitic building-stones, distribu-
tion, 8 1.

Granitoid texture, 14.
Granular texture, 14.
Granulite, 23, 332.
Graphic materials, 358.
Graphite, plumbago, 339, 358, 360,

362.

Gravel, 15, 348.
Gray-band, sandstone, 88, 353.
Gray copper, tetrahedrite, 186, 233.
Great Meadows, N. J., drained,

127, 132.
Greisen, 22.
Grindstones, 353,
Grit, 16.
Guano, 124.
Gypsum, 17, 124.

Hade of veins, 32.
Hanging-wall, 199.
Health, geological conditions of,

129.

Heavy spar, 361.
Hematite, 18, 224.
Hiddenite, 376.
Honestone, 354.
Hornblende, 6.
Hornblendic gneiss, 21.
Hornblende schist, 22.
Horn Silver mine, 243, 267.

Hornstone, anti-friction, 363.
Horses or riders of veins, 200,

204, 206.

Hot limes, 19, 96.
Huron shale, 180.
Hyacinth, 375.
Hydraulic lime, 19, 97.

geologic occurrence, 98.
Hydro-mica schist, 21.

Idria, mercury, 259.
Igneous rocks, II, 22.
Illuminating substances, 165.
Impregnations, 189, 192, 257, 275.
Iridium, 293.
Iron ores, 17, 224.

chief geologic horizons, 226.

forms of deposit, 225.

paints, 361.

production, 1882, 229.
Irregularities in width of veins,

199, 219.
Itacolumite, 373.

Jade, 368.
Japan, 270, 280.
Jargoon, 375.
Jasper, 367.
Jet, 369.

Johnstown cement, 99.
Jointed structure, 48.
Joints, 13.

Joplin and Granby lead and zinc,
244, 250.

Kainite, 310.
Kaluscz, 309.

Keweenaw Point, 233, 234.
Key for determining rocks, 24.
Key rocks, 145.
Kidney ore, 17, 225.
Kieserite, 310, 316.
Kimberley, S. Africa, 373.

Labradorite, 367.

Laccolites, 34.

Lake Superior copper, 234.

Lamination, 12, 49.

Lancaster Gap mine, 286.

Lapis lazuli, 368.

Lead, chief uses, 247.

forms of deposit, 242.

ores, 241.

product, 1882, 245, 246.

INDEX.

383

Leaders or stringers of veins,

203.

Leadville, 195, 210, 243, 266.
Lignite, 139, 140.
Lime, 96, 119, 342.
Limestone, 18, 19, 89, 92.
Limonite, 18, 224, 225.
Liparite, 23.

Lithographic limestone, 359.
Lode, 196, 197.
Los Cerillos Mountains, 377.
Louisville cement, 99.
Lower Helderberg limestone, 90,

99.
Lubricators, mineral, 362.

Magnesia, 316, 342.
Magnesian limestone, 19.
Magnesite, 289, 316.
Magnesium, 289.
Magnetite, 18, 224.
Malachite, 232, 368.
Manganese, 291.
Mansfeld, copper, 234, 238.
Marble, 19, 84, 369.
Marls, calcareous, 120.

greensand and analyses, 120,
121.

Mass deposits, stocks, 189, 194.
Massive rocks, 9.

structure, 12.
Materials of physical application,

347-

Medina sandstone, 87, 350.
Mercury, three regions of, 257.
Mesozoic sandstone, 88.
Metamorphic ore deposits, 195.

rocks, 10, 20.
Mexico, 255, 268.
Mica, 6, 343.

schist, 21.
Millstones, 355.
Milwaukee cement, 99.
Mine la Motte, 286.
Mineral lubricators, 362.
Minette, 22.
Mispickel, 293.
Missouri, 244, 250, 360.
Molding sand, 363.
Molybdenite, 293.
Monoclinal, 30.

Montezuma Marsh, N. Y., 127,
132.

Moonstone, 367.
Mortar, 95.
Moss agate, 367.
Muck, 118.

Nagyagite, 274.

Nephrite or jade, 368.

New Almaden, 258.

New Mexico, 234, 236, 267.

Niagara limestone, 90, 92.

Nickel, 286.

Nitre, 309.

Nitrogen from coal and shale, 124,

181.

Normal faults, 206.
Nuggets of gold and platinum,

277, 284.

Ochre, iron paint, 361.

Ohio lower coal measures, 145.

Oil sands of Bradford, 166, 170.

Oil Creek, Pa., 168.

Warren, etc., Counties, Pa., 170.

West Va. and Ohio, 171.
Oil territory of Baku, 171.

Burmah, 172.

California, 171.
Oil wells, how bored, 173.

how operated, 176.
Oil shales, 180.
Old Dominion mine, 236.
Ontario mine, 267.
Onyx, 367.

marble, 16, 370.
Oolite, 16.
Opal, 371, 377.
Ophiolite, 19.
Ores, defined, 183.

agents of mineralization, 184.
Ore chimneys, 203.

deposits, 184.
Ore Knob, N. C., 237.
Organic sediments, 18.
Origin of ore deposits, 188.
Ornamental stones, 365, 366.
Oscuras Mountains, 234.
Outcrop, 32.
Oxide ores, 184.

Parker's cement, 99.
Paving-stones, 349.
Pay streaks, 202.
Peabody mine, Arizona, 236.

INDEX.

Pegmatite, 23.

Periods of rocks, table, 42.

Petroleum, nature, etc., 165.

refining and use, 177.
Petzite, 274.

Phosphates, mineral, 123.
Phosphorus in coal, 158.
Pigments, mineral, 360.
Pike's Peak, topaz, 374.
Pittsburg coal seam, 144.
Placers, 190, 275.
Platinum, 284.
Plumbago. See Graphite.
Plutonic rocks, n.
Porphyries, ornamental, 370.
Porphyritic texture, 14.
Portland cement, 99.
Positions of strata, 29.
Potash, 126, 309.
Potsdam sandstone, 87, 331, 350.
Pottery clays, 320, 323.
Proportions of precious metals in

ores, 187.
Prospecting, 213.
Pumice, 358.
Pyrite, 7, 296.

qualities needed, 300.

uses, 299.
Pyrolusite, 292.
Pyrophyllite, 359.
Pyroschists, 180.
Pyroxene, 6.

Quartz, 5, 21, 328, 366.
Quartzite, 15, 21.

Quasi-veins, chambers, 189, 195,
251, 275.

Red chalk, 359.

Red-shortness of iron, 158, 228.
Regions of vein-fissures, 198.

of ore deposits, 211, 213.
Reopening of veins, 204.
Reverse faults, 207.
Rhyolite, 23, 25.
Rift of granites, 83, 349.
Rio Tinto, Spain, 233, 238, 298.
Road materials, 347.
Rocks, condition of components,
8.

crystalline, 8, 10.

mineral components, 4.

sedimentary, 9, 15.

Rocks, stratified, 9.
Rock masses, arrangement, 27.
Rosendale cement, 99.
Ruby, balas, and spinel, 374.
Ruby, Oriental, 374.

Salometer, 305.

Salt and uses, 17, 125, 304, 308.

Salt, forms of deposit, 304.

geological horizons, 306.
Sampling ores, 216.
Sand, 15, 95, 330, 357.
Sand-paper, 357.
Sandstone, 15, 86, 357.
Sanitation, geologic considerations,

129.

San Juan region, 236, 243, 266.
Sapphire, 374.
Sardonyx, 367.
Schistose structure, 12.
Seam, 12.

Sedimentary rocks, 9, 15.
Segregated veins, 36, 196.
Selvage, 204.

Semi-anthracite coal, 138, 140.
Semi-bituminous coal, 138, 140.
Serpentine, 8, 22.
Shale, 13, 16.
Shingle, 15.
Sicily, 303.
Siderite, 17, 225.
Silesia, 246, 251.
Silicate ores, 185.
Silicious, 8.
Silver, American regions, 265.

foreign regions, 268.

forms of deposit, 264.

ores, 260.

production, 268, 270.

uses, 271, 282.
Silver Islet, 269.
Silver King mine, 266.
Silver Reef, 265, 267.
Sinter, silicious, 17.
Slate, 85.

Slate Range Marsh, borax, 314.
Slaty structure, 13.
Slickensides, 32, 204.
Smithsonite, 248.
Soapstone, 343, 359.
Socorro Mountains, N. M., 268.
Soda, 310.
Soils, amendments, in.

INDEX.

385

Soils, composition, 101.

from various rocks, 103.

of disintegration, 103.

of transport, 104, 109.

origin, 102.

physical characters, no.
Solenhofen, 360.
Spain, 238, 245, 259, 270.
Spathic iron, 17, 225.
Sperenberg, 306, 307.
Sphalerite, 248.
Spinel, 374.
Spirifer, 39.
Splint coal, 138, 140.
Springs, 52.

Stalactite and stalagmite, 16.
Stassfurt, 126, 306, 310.
Steatite, 359.
Ste. Genevieve County, Mo., 234,

237-

Stocke, 35, 194.
Stockworks, 189, "95.
St. Peter's sandstone, 331.
Strass, 371.
Stratification, n.
Stratified rocks, 27.
Stream tin, 255.
Strength of building-stones, 67.

of stones, table, 69.
Strike of rocks, 30.
Strontium, 317.

Structure, economic relations, 45,
48, 49.

of rocks, n.
Sub-carboniferous limestones, 91.

sandstones, 88.
Subsoils, 107, 127.
Sulphide ores, 184.
Sulphur in coal, 158.
Sulphur, origin and uses, 302,

303.

Sunstone, 367.
Superposition, test of relative age,

37-

Surface appearance of ores, 208.
Syenite, 23, 26.
Syenitic granite, 22, 26.
Synclinal, 31.
Sylvanite, 274.
Sylvite, 310.

Talc, 7, 362.
Talcose schist, 21.

I Tell's Marsh, borax, 313.
1 Telluride ores, 185.

Temperature changes, effects on
building-stones, 73, 74.

Tenorite, 232.

Tetrahedrite, 186, 233.

Texture of rocks, 14.

Tin, 254.

Titanium, 318.

Tombstone District, 266.

Topaz, 374.

Torpedoes in oil-wells, 177.

Tourmaline, 375'

Trachyte, 23, 26.

Transportation, importance of,
217.

Travertine, 16.

Trenton limestone, 89.

Triassic, coal-fields, 149.

Trilobites, 39.

Tripoli, 358.

Tungsten, 294.

Turquoise, 371, 376.

Ultramarine, 368.

Umber, 361.

Unconformability of rocks, 33.

Under-clays of coals, 143.

Unstratified rocks, 34.

Uplifts, effect on accessibility,

47-

Uranium, 294.
Utica slate, oil shale, 180.

Value of ore deposits, 215, 218.

Veins, 35, 196.

Vein-stone, 183, 187.

Verd - antique marble, 19, 84,

370.

Vermont, 237, 354.
Vitreous texture, 14.
Vugs, i.e., druses, 202.

Water in coals, 157.
Water-lime group, 99.
Water supply, 52, 129.
Wells, 55.
Whetstones, 354.
Whiting, 360.
Wieliczka, 306, 307.
Willemite, 248.
Wolfram, 254, 294.

386

INDEX.

Wood's Mine, Pa., 291.
Wood River region, 245.
Working ore deposits, costs,

217.

Wyoming, 237, 311.
Wythe County, Va., 245, 250.

Zinc, American localities, 250.

foreign centers, 251.

ores, 247.

product and uses, 252.
Zincite, 248.
Zircon, 375.

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THIS BOOK IS DUE ON THE LAST DATE
STAMPED BELOW

Books not returned on time are subject to a fine of
50c per volume after the third day overdue, increasing
to $1.00 per volume after the sixth day. Books not in
demand may be renewed if application
expiration of loan period. •• .

made before

NOV 18 '01J>
OCT 16 191S

SPfi 84 1922

APR

1931

50m-7,'16

YB 15521

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Full text of "Applied geology. A treatise on the industrial relations of geological structure; and on the nature, occurrence, and uses of substances derived from geological sources"

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