MISCELLANEOUS ROCKS
There are a few rocks which do not fit into any of the three groups
described, such as concretions, geodes, meteorites, etc., and they are
gathered together here. There is also one type of rock, which really
belongs among the minerals, but is likely not to be so recognized at
first glance, and that is the material filling veins. These last are
sometimes designated “vein rocks,” but are really massive deposits of
one, two or more minerals, and should be referred to the minerals when
found.
Concretions
In the sedimentary rocks there frequently occur inclusions of a nature
different from the surrounding rock. In shape they are usually rounded,
nodular, spherical, discoidal, ovate, flattened, elongated or
ring-shaped, or combinations of the foregoing, making often curious and
fantastic forms. In size they range from a fraction of an inch in
diameter to several feet through. When broken, they may show a nucleus,
around which more or less concentric layers have formed, or neither
nucleus nor concentric structure may be visible. The layered structure
of the surrounding rock in some cases continues right through the
nodular mass. These structures are called concretions, and their
formation in all cases is at least due to similar reactions.
In general the concretions differ from the surrounding rock in
composition, but are usually composed of some one of its impurities, of
lime in the clays or silica in limestones, of iron oxide in sandstone,
etc. They seem to have originated as a result of the solution of the
minor mineral, and then its redeposition around some center or nucleus.
In many cases the nucleus is organic, such as a leaf, a shell, a bone,
etc., so that when the concretion is split, in its center will be found
the perfect imprint of the leaf, or the shell of a mollusk, or a bone of
a higher animal, sometimes a whole skeleton. Again the nucleus may be
inorganic like a grain of sand; and in still other cases no nucleus can
be found, though there was probably one in the beginning. What has
happened is somewhat like the case of accessory minerals in igneous and
metamorphic rocks. A layer of sediment was laid down, including in it,
here and there, something foreign to the run of the rock. Later when the
water leaches through this rock, impregnated with lime for instance, it
comes to the point where a leaf is decomposing. The products of the leaf
decomposition are different from what is already present in solution,
and may precipitate some of the lime in that neighborhood. As long as
leaf decomposition continues the precipitation in that region will
continue and increase the size of the concretion. This sort of action
accounts for many of the concretions, especially those about organic
remains. In some other cases where there is no nucleus, as the flint in
chalk, what has taken place is that the small amounts of silica in the
lime have been dissolved, and then around some center has constantly
been added more and more non-crystalline silica until a mass of flint
has accumulated. There may be a considerable variety of ways to account
for different concretions, but in all cases solutions of one mineral
have come in contact with solutions of a different kind, and
precipitation about a center has resulted.
Clay stones
Pl. 68
Of all the concretions these are perhaps the commonest, being found in
the clays of all types and in many regions. They are made of lime and
precipitated around some nucleus of foreign matter. The shapes vary
widely, usually discs, flattened ovals or even rings, in most all cases
however flattened. This is indicative of the water moving though the
clay more freely in some layers than others. Often clay stones occur so
abundantly that two or more have grown together making fantastic shapes,
sometimes resembling animals, and all sorts of fancied but unrelated
objects. As the clay stones have grown the clay has not been pushed
aside, but has been incorporated within the concretion; so that when a
concretion is dissolved in acid, it yields not only the lime, which is
its reason for being, but also a large amount of clay.
Claystones are found in clays most anywhere, usually occurring in
certain layers and being absent from others.
Lime concretions
These are found mostly in shales which carry a high percentage of clay
as impurities, and are characteristic of the older geological
formations, especially ancient sea bottoms. They are likely to have as a
nucleus some shell, fish bone, or a leaf, which when the concretion is
split, reveals a wonderfully preserved portion of an animal or a plant,
which was buried millions of years ago. The lime concretion is closely
related to the claystone, and is really a claystone which has been
buried so long that the surrounding matrix has changed to a shale
instead of remaining clay.
One of the most famous localities for these lime concretions is Mazon
Creek, Illinois, where thousands of these concretions have been picked
up and split to study the organic remains included. The commonest
objects found are fern leaves, like the one on Plate 68. But about once
in a thousand times they inclose a spider or insect, and once in ten
thousand times the skeleton of an amphibian, which is of especial
interest, as here have been thus found the remains of the very earliest
of the land animals. These remains were inclosed in these concretions
during the coal age, probably 50,000,000 years ago, and once inclosed
all the hard parts have been as well preserved after that long interval,
as they were immediately after being inclosed in the concretion. Lime
concretions range from less than an inch in diameter to several feet
through. They are not confined to shales, but sometimes occur in
sandstones, in this case also usually having as a nucleus either a
shell, or the bone, or bones, of some animal.
They are likely to be found anywhere in the limestone belt, from the
Appalachian Mountains to the Rocky Mountains, or in the Great Basin, or
on the Pacific Coast. Often they have been mistaken for turtles and
other objects. A good many of the cases where the head or body of
animals “petrified with all the flesh” are reported, it is one of these
concretions which has a shape sufficiently like the part described, for
the imagination to construct the rest.
Septeria
Pl. 69
Septeria are lime concretions, which, after they had formed, have shrunk
and developed a series of cracks running through them in all sorts of
directions, and since then the cracks have been filled with various
minerals, such as calcite, dolomite, and siderite. These make a series
of veins which intersect the concretion, in a sort of network. Septeria
are mostly of considerable size, ranging from six inches in diameter to
several feet through. They are characteristic of the shales of ancient
sea bottoms, especially those of Devonian age in New York, and
Pennsylvania, and those of Cretaceous age in Wyoming, Montana and the
Dakotas.
Flint concretions
The silica in limestones is often segregated into nodular masses of
varying sizes, to make concretions of flint. Such masses have grown in
the limestone, and, while growing, have either pushed away, or dissolved
the adjacent limestone, so that the flint nodule is pure silica. They
are especially characteristic of the chalk beds, and of ancient
limestones which formed on the floor of the sea, like the Helderberg
Limestone of New York, Pennsylvania, Ohio, etc. When thin sections are
cut through these flints, and examined under the microscope, many
remnants of the shells of plants and animals are still recognizable. A
nucleus is seldom found, but in some cases there is a fossil in the
nodule about which the concretion doubtless formed. The spicules of
sponges, shells of diatoms, and of radiolarians seem to have contributed
most of the material from which flint concretions are formed. In
addition to the silica there are frequently inclosed in these nodules
the horny jaws of various sea worms, and a host of spiny balls the
relationships of which are still unknown.
Sandstone concretions
There are two types of sandstone concretions, first those which are
cemented with lime, and second those cemented with iron oxide. The
concretions bound by lime are especially characteristic of sandstones
which were laid down as river deposits, either in the channels or on the
flood plains, and also the sandy deposits resulting from wind
deposition. In these cases the concretions will mostly be found to have
formed around some organic nucleus, most frequently about a bone, or
group of bones, of some ancient animal. In this country they are mostly
found in the arid and semiarid sections of the West, where the present
day wind erosion exposes the harder parts of bluffs, etc.
The second type of sandstone concretion is the one in which the cement
is most often limonite, less often hematite. These concretions are less
dense than the lime ones, and in some cases the limonite is only
precipitated at a distance from the nucleus, which has resulted in the
formation of a hollow shell, filled with loose sand. This is especially
characteristic of certain concretions, found in a gravel or coarse sand
in the region of Middletown, Del.
Oolites
In large bodies of water like the sea and some larger lakes we find
concretions which have formed, or are still forming, about tiny grains
of sand, which are still being moved about by the waves and currents. In
such cases not only are great masses of concretions formed but they have
very clearly marked the concentric layering, which shows that they have
increased in size, sometimes more rapidly and sometimes more slowly.
Where great masses of such concretions have formed the resulting rock
appears like a great mass of small eggs, whence the term oolite. The
cement may be any one of several substances, but lime, silica, and
hematite are perhaps the most common. Here and there are found larger or
smaller masses of this oolite. In some cases it would appear that the
material was precipitated by the action of bacteria. Such for instance
is probably the origin of the Clinton iron ore, a bed of oolitic
hematite, extending from New York State all down the Appalachian
Mountains to Alabama.
Pisolite
Pl. 69
When the concretions, formed in exactly the same manner as in the case
of oolite, are of a size bigger than a pea, then the rock is known as
pisolite.
Other Concretions
Though less abundant concretion may form from still other substances.
Hematite has been mentioned, and when concretions are made of this
material, either they have been deposited by bacteria, or were formed as
limonite and the water of crystallization of this latter mineral driven
off.
Manganese concretions are found on the floor of the ocean at maximum
depths, and brought to the surface by dredging.
Geodes
Geodes are nodules, which, when broken open, are found to be hollow and
the cavity lined with one or more minerals. They represent a special
case of minerals in a cave. There was in the first place a cavity in the
surrounding rock, usually of sand or clay. As the water leached through
the surrounding rock, it became saturated with one or more minerals and
then coming into the cavity, deposited the minerals, either as crystals,
or as a non-crystalline mass, lining the cavity. Thus the inside is
often a beautiful cluster of bristling crystals, or it may be simply
layer on layer of chalcedony of any color. Before this process had gone
so far as to completely fill the cavity, erosion had dislodged the mass,
and it has been found. One usually recognizes that it is a geode by the
fact that it is far too light to be a solid rock, and then it may be
carefully broken. They are characteristic of certain formations; so that
having accidentally broken the first one, others can be carefully opened
to display the beauty of the interior. The geode illustrated on Plate 70
is lined with quartz crystals, but near by were found many others, some
of which had chalcedony and some jasper as a lining. Such crystallined
nodules are usually called geodes so long as they occur in a softer
matrix so that they are easily dislodged, and until they reach a size of
three or four feet in diameter.
Pebbles
When picked up either from brook beds, sea beaches, or the open plain,
there are few forms of rock which tell a story of the past more
completely than do pebbles; and any one, who enjoys reading a story
written in form, structure and composition, will find in pebbles one of
the most satisfying and at the same time testing exercises. The story
may be complex or simple according to what has happened to the parent
rock, and to that is added what happened since the pebble left the ledge
where it was a part of a great mass. One must not forget to take into
consideration where the pebble was found and the character of its
associates. This sort of exercise is recommended to all interested in
rocks. It will yield something upon first trying, and more on prolonged
study; and the fullness with which it is done will test one’s knowledge
of the meaning of rocks as nothing else will do. As a sample of this
sort of exercise let us take the two pebbles illustrated on Plate 71.
The upper one is a common quartz pebble picked up in a New England brook
bed. Such pebbles are common all over the country formerly covered by
the glacial ice sheet. It is crystalline quartz, but the individual
crystals are not distinguishable, and such quartz is typical as the
filling of veins. It therefore goes back to a time when the rocks were
fissured, probably in connection with the folding accompanying mountain
making far to the north in Canada. Into the fissures thus formed seeped
the water which had been leaching through the adjacent rocks, and it was
saturated with silica which it had dissolved from those rocks. In the
open fissure the quartz was deposited as crystals, which grew finally
filling the fissure and crowding each other so that all the faces were
obliterated. The quartz vein was complete, but it must have been far
below the surface of the ground. Time must have passed, thousands of
years of it, until, in the weathering away of the mountain system, the
many feet of overlying rock were removed and this vein was brought to
the surface. As the quartz is harder than the adjacent rocks, the vein
soon projected as a ledge. The effect of changes of temperature in
alternately expanding and contracting the rocks developed cracks, into
which water worked its way, and then the breaking was hastened by the
expansion which takes place when water freezes, and in exposed regions
is so effective, because the freezing and thawing are so often repeated.
Finally an angular fragment of quartz was dislodged and lay on the
surface, resistant to the solvent power of the rain. In this case this
happened just before the advance of the great ice sheet. When that came
to the place where the fragment lay, it was picked up along with all
other loose material and partly shoved in front of, but probably mostly
carried frozen in the ice, and journeyed one, two, three hundred,
perhaps a thousand miles. This took many years for the ice moved only a
few feet a day. Finally however it came to the point where the ice
melted as fast as it advanced, and our quartz fragment was dropped at
the front of the ice sheet along with other great masses of till. Here
there was abundant water, partly from the melting of the ice, and partly
from the storms which must develop where there are such contrasts in
temperature, as there would be over the ice, on one hand, and over the
bare land in front of the ice on the other hand. A torrent picked up our
fragment and started it on a second journey, banging against other
stones as it rolled along down the stream bed, every time it struck
another stone bruising the corners which soon became rounded. Thus from
time to time during high water the quartz fragment, becoming rounder
every time it moved, journeyed down stream, until it came to the point
where the stream emptied into a lake. Here the current was checked and
the stone dropped to the bottom along with other larger stones to make
the delta at the mouth of the stream. There it lay as long as the lake
existed, and would be lying now, but that in New England a tilting
movement of the land tipped the north end of the lake up and the water
all ran out. Then the stream began to flow over its own delta and in
time of freshet tore a channel down through the old delta carrying the
pebble still further down, until it came to the level stretch which
represented the old lake’s bottom and there it dropped the pebble in its
bed. And there it was found and picked up to become the pebble which
told the above story of its life, and to repeat it as often as anyone
will look at it with a seeing eye.
The second pebble is quite a different one. It was picked up in a gravel
bank along a railroad cut, just at the foot of Mt. Toby in
Massachussetts, and the writer has used it many times to test his
students, to see if they could read the story which it tells.
It consists of two sorts of rock, the one, angular fragments of a
hornblende schist, the other, a fine-grained granite filling all the
spaces between the fragments of schist, even in cracks less than a
quarter of an inch wide. The schist is the older rock and in its first
appearance represents a deposit of mud (clay and sand) on the floor of
the ocean, well out from the shore, and somewhere off to the east of Mt.
Toby, perhaps ten miles, perhaps more, from the place where it was
found. This was back in early Palæozoic times, millions of years ago.
This deposit was buried by further layers of sediment on the sea bottom
and cemented into a shale. Then during a mountain making period the
region was folded, and the sediments were altered by the combined
pressure and heat, our layer of rock becoming a hornblende schist. After
that happened considerable time must have passed, but just how much is
not indicated by the pebble, before another period of disturbance took
place, during which this deep seated schist was faulted, and shattered
to fragments along the line of breaking. This accounts for the angular
fragments. Then into the fissure thus formed was pressed a molten magma,
which while liquid enough to flow and be squeezed into every opening
could not have been very hot; for not even the corners of the schist
fragments are melted or altered, so as to appear any different from the
mass of the schist. The molten magma cooled rather slowly, making a
fine-grained granite. This must all have taken place far below the
surface, or the magma would have cooled into a felsite or dense lava.
Again a long time must have elapsed, while the rock overlying our piece
was eroded away, so it could come to the surface. Just about the time it
did come to the surface, the Connecticut Valley was formed by a great
block, 95 miles long by fifteen to twenty miles wide, dropping down six
or eight thousand feet (probably not all at once but by one or two
hundred feet at a time) between two north and south faults. This took
place in the Triassic Period. Of course the streams then began to wash
sand and stones of all sizes into the hole. Our pebble was one of these.
While still an angular fragment, lying perhaps ten miles east of the
Connecticut Valley, a stream started it moving, and as it rolled along
the brook bed, it was battered and rounded to its present shape, and
finally tumbled over a waterfall to the bottom of the great hole, which
had been formed as described above. Here with other stones it formed
part of a coarse gravel, coarsest near the sides of the hole, and finer
toward the middle; for the material was further distributed in the
bottom of the valley. Our stone stayed pretty near the side and was soon
buried beneath hundreds of feet of similar material. The leaching water
dissolved enough iron rust so that this acted on the lower layers as a
cement and bound the whole mass into a conglomerate.
Here for some millions of years our pebble rested, while above it was
piled sand and gravel and a couple of sheets of lava, until the hole was
filled, and our pebble was near the bottom of the mass. Later movements
of the land raised the whole region, fully six thousand feet, and
erosion went on for other millions of years. The conglomerate and
sandstone wore away faster than the metamorphosed rocks on either side
of the filled valley, so that a new valley, the present Connecticut
Valley, came into existence.
When our pebble finally came near to the surface on the side of Mt. Toby
(a mound of conglomerate which somehow was protected and wore down a
little less rapidly than the conglomerate on either side of it), it was
just about the time of the glacial period. The great ice sheet went over
the mountain removing all the loose material and some more of the solid
conglomerate. This brought our pebble to the surface, but too late to be
moved by the ice. However as soon as the ice left the Mt. Toby region,
the rains fell, and in the further weathering of the conglomerate, the
cement holding our pebble in place was dissolved and it was freed. At
once a tiny brook started it rolling down the side of the mountain, a
brook so small that when the pebble reached the foot of the slope it did
not have power to carry it further. Here there gathered a fan-shaped
mound of such pebbles, known as an alluvial fan. It rested here not over
a couple of thousand years, when the Central Vermont R. R. cut a groove
through the fan, using the material for ballast, and here the pebble was
found and brought home.
Meteorites
Meteorites can hardly be called common, but there is always a chance of
finding one, and their interest is so great, that none should escape
because unrecognized.
Meteorites are visitors to the earth from space, and they bring to us
knowledge of the composition of planets and solar systems, other than
our own. It is of interest to note, that while they have brought to us
some combinations of elements which do not occur in the earth, still
they have not brought any element with which we were not already
familiar. They are popularly known as “falling” or “shooting stars,”
though of course they are not stars, but only small masses of matter
which are entirely invisible until they come inside our atmosphere.
In space there are many small (compared with the size of the earth)
chunks of matter, each pursuing its solitary way around the sun, or
wandering through space along paths entirely unrelated to the sun. From
time to time one of these passes near enough to the earth, so as to be
influenced by its attraction, and then comes rushing toward it at
tremendous speed, 20 to 30 miles per second. As soon as it comes into
the atmosphere, even the very attenuated atmosphere, a couple of hundred
miles above the surface, friction heats the surface of the meteor until
it glows, and by that light we see the so-called shooting star, often
with a trail of luminous matter streaming out behind. Of course in using
this term “shooting star,” we understand the meteor is no star, for they
are bodies as big as our sun, shining at distances billions of miles
away.
As the meteor rushes through the atmosphere it may all burn up, no large
fragment reaching the earth’s surface. The luminous matter streaming out
behind is material which has melted and dripped off the main mass. As
this oxidizes and cools, that part which did not become gaseous will
finally fall to the earth as fine dust. When however a meteor actually
falls to the earth, its surface is still hot, though probably there has
not been time enough for much heat to be transmitted to the interior. At
any rate they do not show any alteration due to this cause. On landing
and sometimes before they land meteors break into two or more pieces.
When found the surface always shows the effects of the heat generated by
the friction of passing through the air, the surface being smoothed, and
covered with stream lines and melted out pits and hollows, and the outer
surface consisting of a thin crust, making an appearance, which once
seen, can hardly be mistaken.
There are two types of meteorites, those made wholly or largely of iron
with some nickel, and appearing like great chunks of iron, and those
which are stony and resemble a granite boulder. In collections the first
sort, _i.e._ iron meteorites, are most abundantly represented, because
most easily recognized when found. They consist of masses of iron and
nickel with small amounts of other elements, ranging in size from the
Cape York meteorite, which fell in northern Greenland in 1894 and was
later brought by Peary to the American Museum, and weighs some 36 tons,
down to small grains as small as a grain of wheat. The largest one which
has fallen in the United States was the Willamette meteorite weighing
some 15 tons, and falling 19 miles south of Portland, Oregon. These and
all iron meteorites have the iron in crystalline form which is readily
seen if the meteorite is cut, and the surface thus made polished, then
etched with acid, which is put on and quickly washed off. Every
meteorite has its particular pattern, as illustrated on Plate 72, and by
these patterns can be identified. Meteorites have a high value and are
eagerly sought by certain large institutions and collectors. Since the
crystalline structure is so characteristic of each fall, when a new
meteorite is found, it is usually cut in two, and one part retained by
the finder or some institution; while the other part is cut into small
pieces, an inch or two on a side and a quarter of an inch thick, but
each large enough to show the characteristic pattern. These are
distributed largely by sale to other collectors. Thus a great meteorite
collection consists of a few large meteorites and a great many small
portions of other meteorites.
The second type of meteorite is the stony meteorite. Where meteorites
have been located as they fell and recovered, the majority of them were
of this type, so that probably more than half of the meteorites which
fall are of the stony type. However when the stony meteorite is exposed
to weathering it takes only a very short time before the surface is
eroded off and then such a meteorite looks like any other boulder and
probably most of them fail to be recognized, and so have been lost.
Because they have so much greater variety, they are in many ways of
greater interest than the iron type.
It is desirable that every one have his eye out for meteorites, and when
found it is desirable that the fact should be reported to some one of
the great institutions which collect them, such as the National Museum
in Washington, or the American Museum in New York. Each one should be on
record even if it is desired to keep it in a private collection.
Fossils
In the sedimentary rocks one is apt to find remains of some of the
animals and plants that lived at the time the rock was forming. While
the soft parts of animals decompose rapidly, shells and bones are likely
to be buried in the sediments, and if the conditions have been
favorable, these remains may be preserved more or less perfectly. All
through the millions of years that sedimentary rocks have been forming
in the sea, in lakes, on river flood plains and in wind swept deserts,
there was an abundance of life, as much as there is today; and our
knowledge of that life is derived from these buried fossil remains, so
that fossils have a great historic interest.
However as there have lived and died several times as many different
kinds of animals as live today, the study of fossils becomes a separate
subject, which cannot be treated in this book. Should any collector of
rocks and minerals come upon fossils, he is opening a new field, and it
will be necessary to turn to other sources for their identification.
General books on this subject are scarce, but one or two are given in
the literature list.
A List of the Elements, the Abbreviations Used for Them, and Their
Atomic Weight, Which Is Approximately the Number of Times Heavier They
Are Than Hydrogen.
Name Oxygen = 16
Aluminium, Al 27
Antimony, Sb 122
Argon, Ar 40
Arsenic, As 75
Barium, Ba 137
Beryllium, Be 9
Bismuth, Bi 209
Boron, B 11
Bromine, Br 80
Cadmium, Cd 112
Cæsium, Cs 132
Calcium, Ca 40
Carbon, C 12
Cerium, Ce 140
Chlorine, Cl 35
Chromium, Cr 52
Cobalt, Co 59
Columbium, Cb 93
Copper, Cu 64
Dysprosium, Dy 162
Erbium, Er 167
Europium, Eu 152
Fluorine, F 19
Gadolinium, Gd 157
Gallium, Ga 70
Germanium, Ge 63
Glucinum, Gl 9
Gold, Au 197
Hafnium, Hf 179
Helium, He 4
Holmium, Ho 165
Hydrogen, H 1
Indium, In 115
Iodine, I 127
Iridium, Ir 193
Iron, Fe 56
Krypton, Kr 84
Lanthanum, La 139
Lead, Pb 207
Lithium, Li 7
Lutecium, Lu 175
Magnesium, Mg 24
Manganese, Mn 55
Mercury, Hg 201
Molybdenum, Mo 96
Neodymium, Nd 144
Neon, Ne 20
Nickel, Ni 59
Nitrogen, N 14
Osmium, Os 190
Oxygen, O 16
Palladium, Pd 107
Phosphorus, P 31
Platinum, Pt 195
Potassium, K 39
Præseodymium, Pr 141
Protoactinium, Pa 231
Radium, Ra 226
Radon, Rn 222
Rhenium, Re 186
Rhodium, Rh 103
Rubidium, Rb 85
Ruthenium, Ru 102
Samarium, Sm 150
Scandium, Sc 45
Selenium, Se 79
Silicon, Si 28
Silver, Ag 108
Sodium, Na 23
Strontium, Sr 88
Sulphur, S 32
Tantalum, Ta 181
Tellurium, Te 128
Terbium, Tb 159
Thallium, Tl 204
Thorium, Th 232
Thulium, Tu 169
Tin, Sn 119
Titanium, Ti 48
Tungsten, W 184
Uranium, U 238
Vanadium, V 51
Xenon, Xe 131
Ytterbium, Yt 173
Yttrium, Y 89
Zinc, Zn 65
Zirconium, Zr 91
Table of Geologic Time
_Eras_
_Periods and their _Important Physical _Important
Duration in Millions Events_ Organic Events_
of Years_
Cenozoic
Quaternary
Recent Youthful land forms Dominance of man.
having high relief
formed.
Pleistocene Epoch 2 M.Y. Period of Heidelberg,
glaciation; four Neanderthal, and
great ice advances. Crô-Magnon man;
extinction of
large mammals.
Tertiary
Pliocene Epoch 10 M.Y. Continuing Intermigration of
world-wide land North and South
elevation. American mammals.
Transformation of
ape to man.
Miocene Epoch 18 M.Y. Cordilleras, Alps, Culmination of
Himalayas formed. modern types of
Widespread mammals. Apes
vulcanism-basalt appear in Old
flows in World.
northwestern United
States.
Oligocene Epoch 10 M.Y. Land dominant; seas Carnivores and
marginal. ungulates develop
into importance.
Eocene Epoch 20 M.Y. Extensive Dawn of the
sedimentation; seas dominance of
marginal. mammals. Reptiles
subordinate.
Cretaceous 65 M.Y. Widespread Climax and
epicontinental culmination of
seas. Laramide reptiles,
revolution at close especially
of period—Rocky dinosaurs; first
Mountains formed. flowering plants
and grasses.
Mesozoic
Jurassic 38 M.Y. Continent emergent; Rise of birds and
shallow seas on flying reptiles,
western North first modern
America. trees.
Triassic 35 M.Y. Continent emergent; Rise of
seas marginal. dinosaurs,
cycads, and
ammonites.
Paleozoic
Permian 35 M.Y. World-wide Extinction of
continental uplift most Paleozoic
and mountain fauna and flora.
building. First modern
Widespread insects.
glaciation.
Pennsylvanian 48 M.Y. Continent Great
alternately rising coal-forming
and sinking. forests, of ferns
and seed-ferns.
Mississippian 35 M.Y. Low lands and Culmination of
widespread crinoids,
submergence. numerous sharks.
Devonian 40 M.Y. Widespread First known land
submergence, local animals, first
vulcanism. forests.
Silurian 28 M.Y. Widespread First lung fishes
submergence, local and scorpions,
deserts. abundant corals.
Ordovician 65 M.Y. 60% of North Climax of
America below sea. invertebrate
dominance, first
vertebrate.
Cambrian 105 M.Y. Widespread First abundant
submergence. invertebrate
fauna, trilobites
dominant.
Proterozoic 700 ± M.Y. Long periods of Bacteria and
granite intrusion, seaweeds present.
sedimentation, and Most
mountain building. invertebrates
probably present,
but remains are
lacking.
Archeozoic 800 ± M.Y. World-wide Blue-green algae
intrusive igneous present,
activity; some primitive
sediments. one-celled plants
and animals
probably present.
BIBLIOGRAPHY
MINERALOGY
_Getting Acquainted with Mineralogy._ By G. L. English, 1936,
McGraw-Hill Book Co. A beginning textbook of mineralogy.
_Introduction to the Study of Minerals and Rocks._ 3rd Edition, by A. F.
Rogers, 1937, McGraw-Hill Book Co. Describes the commoner minerals
systematically.
_Dana’s Textbook of Mineralogy._ 4th Edition, revised by W. E. Ford,
1932, John Wiley and Sons. Detailed descriptions of minerals, their
physical properties, and their occurrence.
_Manual of Mineralogy._ 15th Edition, by E. S. Dana, revised by C. S.
Hurlburt, 1941, John Wiley and Sons. A textbook of mineralogy.
MINERAL ECONOMICS, GEOPOLITICS
_World Minerals and World Peace._ By C. K. Leith, J. W. Furness, and
Cleona Lewis, 1943, The Brookings Institution. Physical, economic,
and political trends in the mineral industry.
_Minerals in World Affairs._ By T. S. Lovering, 1943, Prentice-Hall.
_Minerals Yearbook._ U. S. Bureau of Mines. An annual volume presenting
statistical data on the production of the mineral resources of the
United States. Reports on individual minerals or rocks may be had
separately.
ECONOMIC GEOLOGY
_Mineral Deposits._ 4th Edition, by W. Lindgren, 1933, McGraw-Hill Book
Co. The manner of occurrence and origin of mineral deposits.
_Elements of Engineering Geology._ 2nd Edition, by H. Ries and T. L.
Watson, 1947, John Wiley and Sons.
_This Fascinating Oil Business._ By M. W. Ball, 1940, Bobbs-Merrill Co.
A simple and elementary description of the petroleum industry.
_Geology of Coal._ By O. Stutzer and A. C. Noe, 1940, University of
Chicago Press.
GENERAL GEOLOGY
_Down to Earth._ By C. Croneis and W. C. Krumbein, 1936, University of
Chicago Press. An introduction to geology, profusely illustrated.
_Textbook of Geology Part I—Physical Geology._ 4th Edition, by C. R.
Longwell, A. Knopf, and R. F. Flint, 1939, John Wiley and Sons. A
standard text on geology.
_Field Geology._ 4th Edition, by F. H. Lahee, 1941, McGraw-Hill Book Co.
Recognition and interpretation of geologic structures and
topographic forms as they are observed, and methods of geologic
work.
PRECIOUS STONES
_A Book of Precious Stones._ By J. Wodiska, 1910, G. P. Putnam’s Sons.
Written for jewelers, but of general interest.
_The Curious Lore of Precious Stones._ By G. F. Kunz, 1913, Lippincott.
Legends and stories of the gem minerals.
_The Magic of Jewels and Charms._ By G. F. Kunz, 1915, Lippincott.
_Popular Gemology._ By R. M. Pearl, 1948, John Wiley and Sons.
Scientific and industrial uses of gems, current information about
their locality and production.
FOSSILS
_An Introduction to the Study of Fossils._ By H. W. Shimer, 1933,
Macmillan Co. An introductory textbook about fossil plants and
animals.
_Invertebrate Paleontology._ By W. H. Twenhofel and R. P. Shrock, 1935,
McGraw-Hill Book Co.
_Textbook of Geology Part II—Historical Geology._ 4th Edition, by C.
Schuchert and C. O. Dunbar, 1941, John Wiley and Sons. The story of
the development of life through the ages.
INDEX
A
Actinolite, 120
Adobe, 210
Agate, 107
Agate, moss, 73, 108
Alabaster, 152
Albertite, 229
Albite, 110, 113, 115
Almandine, 97
Almandite, 122, 123
Aluminum bronze, 74
Aluminum group, 73
Amazon stone, 114
Amber, 223
Amethyst, 104
Amethyst, Oriental, 75
Amianthus, 120
Amphibole group, 119
Amygdoloid, 194
Amygdoloidal, 176
Analcite, 141
Andesite, 113, 187
Andradite, 122, 124
Anglesite, 62
Anhydrite, 149
Anorthite, 110, 113
Anorthosite, 183
Anthracite, 218, 222
Antimony, 81
Antimony, gray, 81
Apatite, 160
Aquamarine, 125
Aragonite, 147
Argentite, 35
Argillite, 242
Arkose, 206
Arsenic group, 78
Arsenopyrite, 79
Asbestos, 120, 140
Augite, 118
Aventurine, 104
Azurite, 46
B
Barite, 154
Barium group, 154
Basalt, 188
Batholith, 174
Bauxite, 77
Beryl, 125
Beryl, golden, 125
Beryllium, 125
Bibliography, 270
Biotite, 129, 130
Bitumen, 228
Black jack, 65
Bloodstone, 106
Bog lime, 213
Bombs, 191
Boracite, 164
Borax, 165
Bornite, 41
Brass, 64
Breccia, 191, 198
Brittania metal, 81
Bronze, 38
Bronze Age, 38
Bronzite, 118
Bytownite, 113
C
Calamine, 68
Calaverite, 30
Calcite, 144
Calcium, 143
Carbon, 156
Carbonite, 222
Carbuncle, 124
Carnelian, 106
Carnotite, 90
Cassiterite, 93
Cat’s eye, 104
Celestite, 153
Cerargyrite, 37
Cerrusite, 61
Ceylonite, 97
Chalcedony, 104, 106
Chalcocite, 42
Chalcopyrite, 40
Chalcotrichite, 45
Chalk, 213
Chert, 107
Chlorite, 140
Chlorospinel, 98
Chromite, 87
Chromium, 86
Chrysocola, 47
Chrysolite, 134, 140
Chrysoprase, 106
Cinnabar, 91
Cinnamon stone, 123
Citrine, 103
Clay, 207
Clay, ball, 208
Clay, brick, 209
Clay, china, 208
Clay, fire, 208
Clay, paving brick, 209
Clay, sewer-pipe, 209
Clay, slip, 209
Clay, stoneware, 209
Clay stones, 250
Cleavage, 21
Cleavage, slaty, 234
Coal, 217
Coal, bituminous, 212, 220
Coal, cannel, 221
Coal, hard, 222
Coal, soft, 220
Cobalt, 84
Cobalt bloom, 85
Cobalt glance, 85
Cobalt gray ore, 85
Cobaltite, 83
Coke, 220
Colemanite, 165
Collecting, 5, 7
Color, 23
Concretions, 248
Concretions, flint, 253
Concretions, lime, 251
Concretions, other, 255
Concretions, sandstone, 253
Conglomerate, 202
Copper, 37, 39
Copper, blushing, 42
Copper, glance, 42
Copper, grey, 43
Copper, peacock, 42
Copper, plush, 45
Copper, purple, 41
Copper, red, 44
Copper, variegated, 42
Copper, yellow, 40
Coquina, 213
Coral, 146
Coral rock, 214
Corundum, 75
Crude oil, 227
Cryolite, 78
Crystal balls, 101
Crystal formation, 14
Crystal rock, 103
Crystal structure, 11
Crystal systems, 13-18
Cuprite, 44
Cyanite, 128
D
Dacite, 187
Dense, 176
Diamond, 157
Diamonds, Matura, 127
Diamonds, slave’s, 133
Diatoms, 231
Dikes, 174
Diorite, 182
Dog-tooth spar, 145
Dolomite, 99
Dry bone, 68
E
Earth, diatomaceous, 23
Elements, listed, 267
Emerald, 125
Emerald, Oriental, 75
Emery, 76
Enstatite, 117
Epidote, 134
Equipment, 7
Erubescite, 42
Extrusive, 173
F
Feldspar, 110
Feldspar, alkalic, 111
Felsite, 186
Felsitic, 176
Ferromanganese, 70
Flagstone, 207
Flint, 106
Fluorine, 162
Fluorite, 162
Fossils, 266
Fragmental, 176
Franklinite, 69
Freestone, 207
G
Gabbro, 183
Galena, 60
Garnet group, 121
Garnet, Sirian, 123
Geodes, 255
German silver, 82
Gilsonite, 229
Glassy, 176
Glucinum, 125
Gneiss, 237
Goethite, 51, 52
Gold, 31
Gold foil, 64
Gold group, 29
Gossan, 50
Granite, 178
Granite, graphic, 179
Granitoid, 176
Graphite, 156, 219
Gravel, 201
Graywacke, 206
Grit, 206
Grossularite, 122, 123
Guano, 230
Gumbo, 210
Gypsum, 150
H
Halite, 163
Hardness, 20
Hardpan, 216
Heavy spar, 154
Heliotrope, 106
Hematite, 53
Hemihedral forms, 19
Hercynite, 98
Hexagonal system, 18
Hornblende, 121
Hornstone, 107
Hyacinth, 127
Hypersthene, 118
I
Ice, 167
Iceland spar, 145
Ice stone, 78
Ilmenite, 94
Intrusive, 174
Iron, 47
Iron, bog, 50
Iron, chromic, 87
Iron, magnetic, 54
Iron pyrites, 56
Iron, spathic, 55
Iron, specular, 53
Isometric system, 13
J
Jacinth, 127
Jargons, 127
Jargoons, 127
Jasper, 106
Jet, 222
K
Kaolin, 137, 208
Kaolinite, 137
L
Labels, 5
Labradorite, 113, 116
Laccolith, 174
Lapilli, 191
Lava, 173
Lead, 59
Lead glance, 60
Lead, green ore, 63
Lead, white ore, 61
Lepidolite, 129, 130
Lignite, 218, 219
Limestone, 212
Limestone, encrinal, 214
Limestone, hydraulic, 214
Limestone, lithographic, 214
Limonite, 49, 51
Loess, 210
Luster, 23
M
Magma, 173
Magnesite, 98
Magnesium group, 96
Magnetite, 54
Malachite, 45
Malanite, 124
Malta, 229
Manganese group, 70
Manganite, 72
Marble, 243
Marble, Suisun, 146
Marcasite, 57
Marl, 211
Mercury, 90
Meteorites, 262
Mica group, 128
Microcline, 113, 114
Millerite, 83
Mineral tables, 25
Minerals, defined, 10
Molybdenite, 81
Molybdenum, 80
Monoclinic system, 17
Monzonite, 181
Morion, 103
Mother-of-pearl, 148
Muscovite, 129
N
Natrolite, 142
Natural gas, 227
Needle iron stone, 52
Niccolite, 83
Nickel, copper, 83
Nickel group, 82
O
Obsidian, 191
Ochre red, 54
Ochre yellow, 49
Oligoclase, 113, 115
Olivine, 134
Olivine-gabbro, 183
Onyx, 108
Onyx, Californian, 146
Onyx marble, 215
Onyx, Mexican, 146
Oolites, 254
Opal, 108
Opal-agate, 109
Opal, common, 109
Opal, fire, 109
Opal, precious, 109
Ophicalcite, 246
Ophiolite, 246
Orpiment, 80
Orthoclase, 110, 113
Orthorhombic system, 16
P
Paste, 103
Pearls, 148
Pearlstone, 193
Peat, 218, 219
Pebbles, 256
Pegmatite, 179
Peridot, 134
Peridotite, 184
Perlite, 193
Petroleum series, 224, 227
Pewter, 60
Phenocrysts, 189
Phlogopite, 129, 131
Phosphate, 160, 230
Phosphorus, 159
Phyllite, 242
Picotite, 97
Pisolite, 255
Pitchstone, 193
Plagioclase, 111
Plasma, 106
Platinum, 95
Plumbago, 156
Porous, 176
Porphyritic, 176
Porphyry, 189
Prase, 104
Prousite, 36
Psilomelane, 72
Pumice, 193
Pyrargyrite, 35
Pyrite, 56
Pyrite, capillary, 83
Pyrite, magnetic, 58
Pyrite, white, 57
Pyritohedron, 56, 318
Pyrolusite, 71
Pyromorphite, 63
Pyrope, 122, 123
Pyroxene group, 116
Pyroxenite, 185
Pyrrhotite, 58
Q
Quartz, 100
Quartz-diorite, 181
Quartz, milky, 103
Quartz, rose, 104
Quartz, smoky, 103
Quartzite, 239
Quicksands, 204
Quicksilver, 90
R
Radium, 89
Realgar, 80
Rhinestones, 101
Rhodochrosite, 73
Rhyolite 185
Rock, phosphate, 230
Rocks, 170
Rocks, defined, 10
Rocks, igneous, 172
Rocks, igneous, classified, 177
Rocks, metamorphic, 232
Rocks, metamorphic, classified, 236
Rocks, sedimentary, 194
Rocks, sedimentary, classified, 196
Rubicelle, 97
Ruby, 75
Ruby, Balas, 97
Ruby mica, 52
Rutile, 94
S
Salt, 163
Sand, 202
Sandstone, 205
Sapphire, 75
Sapphire, Oriental white, 75
Sardonyx, 108
Satin spar, 146
Schist, 240
Schistosity, 234
Scoria, 192, 193
Septeria, 252
Sericite, 130
Serpentine, 139, 245
Shale, 210
Shale, oil-bearing, 225
Sheet, 173
Siderite, 55
Silica, 99
Silicates, 99
Silicon, 99
Sill, 174
Sillimanite, 128
Silver, 34
Silver, dark red, 35
Silver, German, 65
Silver glance, 35
Silver group, 32
Silver, horn, 37
Silver, light red, 36
Silver, ruby, 35
Sinter, 110
Slate, 241
Smalt, 84
Smaltite, 85
Smithsonite, 68
Soapstone, 244
Sodalite, 126
Soil, 198
Solder, 60
Specific gravity, 22
Speigeleisen, 70
Spelter, 64
Spessartite, 122, 123
Sphalerite, 65
Spinel, 97
Spinel-ruby, 97
Stalactites, 146
Stalagmites, 146
Staurolite, 133
Steatite, 244
Stellite, 84, 88
Stibnite, 81
Stilbite, 143
Stock, 174
Streak, 23
Strontianite, 152
Strontium group, 152
Sulphur, 166
Syenite, 180
Sylvanite, 30
T
Talc, 138
Talus, 197
Tetragonal system, 15
Tetrahedrite, 43
Tile ore, 45
Till, 215
Tillite, 217
Time chart, 268
Tin, 92
Tin stone, 93
Titanium, 93
Tonalite, 181
Topaz, 131
Topaz, false, 103
Topaz, Oriental, 75
Topaz, Saxon, 132
Topaz, Scotch, 132
Topaz, smoky, 132
Topaz, Spanish, 132
Tourmaline, 135
Trachite, 186
Trap, 188
Travertine, 146, 215
Tremolite, 120
Triclinic system, 18
Tripolite, 110
Tufa, calcareous, 147
Tuff, 190
Tungsten, 87
Turgite, 51
Turquois, 161
Twinning, 19
Type metal, 60
U
Uintaite, 229
Uranium, 89
Uvarovite, 122, 123
V
Vanadium, 89
Verde antique, 247
Volcanic ash, 190
Volcanic blocks, 191
W
Water, 167
White metal, 64
Willemite, 67
Witherite, 153
Wolframite, 88
Wood, agatized, 108
Wood, opalized, 109
Wood, silicified, 108
X
Xanthosiderite, 51
Z
Zeolites, 141
Zinc, 63
Zinc blende, 65
Zinc red ore, 66
Zinc, ruby, 65
Zincite, 66
Zircon, 127
Plate Frontispiece
[Illustration: Tourmaline crystals, growing amid feldspar crystals
in a cavity in granite, from Paris, Me.]
Plate 5
[Illustration: Gold in quartz, from California]
Plate 6
[Illustration: Native silver in calcite]
[Illustration: Argentite, the black masses throughout the white
quartz]
Plate 7
[Illustration: Pyrargyrite as it appears after moderate exposure to
the light.]
[Illustration: Crystal form of Pyrargyrite]
[Illustration: Prousite as it appears after moderate exposure to the
light]
Plate 8
[Illustration: Native copper from Michigan]
[Illustration: Chalcopyrite in tetrahedrons and an occasional
octahedron.]
Plate 9
[Illustration: Chalcocite crystals with the bluish tarnish]
[Illustration: Tetrahedrite crystals]
Plate 11
[Illustration: Cuprite, the red crystals showing characteristic
color, other showing the green tarnish of malachite]
[Illustration: Malachite (green) and azurite (blue), the two
minerals shown together as they very commonly occur]
Plate 12
[Illustration: Limonite]
[Illustration: The crystal form in which goethite is found, _p_ is
the prism faces, _b_ and _c_ are faces formed by beveling the edges
of the prism, _o_ is the pyramidal face characteristic of the ends]
Plate 13
[Illustration: Hematite, Clinton iron ore, oolitic]
[Illustration: Siderite crystals]
Plate 15
[Illustration: Pyrite crystals]
[Illustration: Marcasite in concretionary form with radiate
structure]
Plate 17
[Illustration: Galena in crystals]
[Illustration: Pyromorphite crystals (green)]
Plate 19
[Illustration: Sphalerite, some the normal yellow and some crystals
with the reddish tinge. (White is dolomite)]
[Illustration: Zincite]
Plate 21
[Illustration: Smithsonite in yellow crystals]
[Illustration: Franklinite in octahedral crystals]
Plate 24
[Illustration: Arsenopyrite, showing crystals massed so as to be
incompletely developed]
[Illustration: Realgar as it usually occurs in powdery
incrustations]
Plate 25
[Illustration: Large crystal of stibnite, the light colored face is
the one parallel to which cleavage occurs]
[Illustration: Niccolite as a vein in slate]
Plate 26
[Illustration: Cobaltite, silver color, with pink tinge]
[Illustration: Smaltite, pink is cobalt bloom]
Plate 27
[Illustration: Carnotite from southwest Colorado]
[Illustration: Cinnabar]
Plate 31
[Illustration: Amethyst, not however deep enough colored for gems]
[Illustration: Jasper, with botryoidal surface]
Plate 32
[Illustration: Banded Agate from Brazil]
Plate 33
[Illustration: Common Opal from Arizona]
[Illustration: Siliceous sinter or Geyserite from The Yellowstone
Park]
Plate 35
[Illustration: A group of Microcline crystals from Pike’s Peak,
Colo.]
[Illustration: Labradorite, showing multiple twinning (the
striation), and the iridescent play of colors]
Plate 36
[Illustration: Crystal form of a pyroxene; _a_ and _b_ prism faces,
_m_ the beveled edge between two prism faces]
[Illustration: Cross section of a pyroxene crystal showing the lines
of intersection of the two cleavage planes]
[Illustration: Cross sections of pyroxenes, showing typical forms
taken by crystals]
[Illustration: Augite crystals, in crystalline limestone]
Plate 38
[Illustration: The dodecahedron and the 24-sided figure
characteristic of garnets]
[Illustration: The garnet, grossularite]
[Illustration: The garnet alamandite]
Plate 39
[Illustration: Beryl of gem quality]
[Illustration: Zircon in syenite]
Plate 40
[Illustration: Cyanite crystals in schist]
[Illustration: A crystal of mica, showing basal cleavage]
Plate 41
[Illustration: Crystal form typical of topaz]
[Illustration: A topaz crystal from Brazil]
[Illustration: Crystal form typical of staurolite when simple]
[Illustration: A typical twin of staurolite]
Plate 43
[Illustration: Serpentine]
[Illustration: Chlorite]
Plate 49
[Illustration: Apatite crystals in crystalline calcite]
[Illustration: The ends of apatite crystals showing common modes of
termination]
Plate 50
[Illustration: A group of fluorite crystals]
[Illustration: A group of halite crystals]
Plate 61
[Illustration: Amber]
[Illustration: Two bottles of petroleum, the left hand one with a
paraffin base, the right hand one with an asphalt base]
Plate 65
[Illustration: Mica schist, with garnets]
[Illustration: Chlorite schist]
Plate 67
[Illustration: Serpentine, composed of serpentine, hematite, and
some calcite]
Plate 1
Basal forms of the isometric system
[Illustration: Cube]
[Illustration: Octahedron]
[Illustration: Dodecahedron]
Plate 2
Basal forms of the tetragonal system
[Illustration: A square prism]
[Illustration: Octahedron]
Basal forms of the orthorhombic system
[Illustration: A Rectangular prism]
[Illustration: Octahedron]
Plate 3
Basal forms of the monoclinic system
[Illustration: The rectangular prism askew]
[Illustration: The octahedron]
[Illustration: A cross section of the prism with its edges beveled
so that the _b_ faces are obliterated by the _m_ faces, and a
six-sided prism is formed (pseudo-hexagonal)]
[Illustration: Basal form of the triclinic system]
Plate 4
Basal forms of the hexagonal system
[Illustration: The six-sided prism]
[Illustration: The double pyramid]
[Illustration: The rhombohedron]
Plate 10
[Illustration: Tetrahedrons showing characteristic manner in which
tetrahedrite occurs]
[Illustration: A cube with the edges beveled and the corners cut in
a form characteristic of cuprite]
Plate 30
[Illustration: Two intergrowing or twinned quartz crystals]
[Illustration: Diagram of the typical quartz crystal, _p_ prism
faces, _l_ left hand rhombohedron, _r_ right hand rhombohedron]
[Illustration: A quartz crystal on which the left hand rhombohedron
is represented by small faces while the right hand rhombohedron has
large faces]
Plate 14
[Illustration: Crystal forms of hematite, _A_ the rhombohedron with
the edges beveled; _B_ the tabular form, resulting from the
excessive development of the two _o_ faces opposite each other]
[Illustration: A typical crystal of magnetite]
[Illustration: The rhombohedron typical of siderite]
Plate 16
[Illustration: The pyritohedron]
[Illustration: The pyritohedron with certain of its edges beveled by
the cube faces, to show the relationship of these two forms]
Plate 18
Typical forms for cerrusite
[Illustration: The pyramid, _n_ the prism face, _m_ the beveled
prism, _p_ the octahedral face, and _o_ the edge of the octahedral
faces beveled]
[Illustration: The simple type of twinning]
[Illustration: A multiple twin where three crystals grow through
each other]
[Illustration: Forms in which anglesite occurs: _l_ the pyramid
face, _p_ the prism face, _o_ the vertical edge of the prism
beveled, _m_ the horizontal edge of the prism beveled, _n_ a further
beveling of the horizontal edge of the prism. _D_ the tabular, _E_
the prismatic form]
Plate 20
[Illustration: A characteristic form in which sphalerite may occur;
being the combination of, _d_ the dodecahedron, _o_ the octahedron,
and _t_, a 24-sided figure]
[Illustration: Characteristic form for zincite crystals, _n_ the
hexagonal prism, and _p_ pyramidal faces on it]
[Illustration: Typical form of crystal of willemite: _p_ the prism,
_r_ rhombohedron faces on end, ½ _r_ a second lower rhombohedron]
Plate 22
[Illustration: Moss agates, showing the dendritic growth of
manganitic minerals, like manganite or pyrolusite]
[Illustration: Moss agates]
[Illustration: Crystal form of manganite]
Plate 23
[Illustration: Crystals of green corundum in syenite, from Montana]
[Illustration: Typical crystal forms of corundum: _A_ the elongated
prism with the alternate corners cut by rhombohedral faces, _B_ the
tabular prism, _C_ the double pyramid]
Plate 28
[Illustration: Cassiterite, twinned crystals]
[Illustration: The crystal form in which both cassiterite and rutile
occur when in simple crystals, _p_ prism faces, _m_ beveling of the
prism, _o_ octahedral face, _n_ beveling of the edge between
octahedral faces]
[Illustration: Multiple twinning characteristic of rutile]
Plate 29
[Illustration: Crystal of Spinel]
Crystal forms in which dolomite occurs
[Illustration: _A_ the cleavage form, rhombohedron with the faces
curved]
[Illustration: _B_ the rhombohedron with the corners cut, as it
often occurs]
[Illustration: _C_ the form found in gypsum or anhydrite]
Plate 34
[Illustration: Orthoclase, a cleavage piece, _a_ and _b_ the perfect
cleavage planes, and _c_ the imperfect cleavage plane]
Crystal forms of orthoclase
[Illustration: _A_ the simple crystal]
[Illustration: _B_ the twinned form]
[Illustration: _C_ the twinned form in which the crystals are
intergrowing]
[Illustration: Diagram of a multiple twin of a plagioclase feldspar]
Plate 37
Diagrams of amphibole crystals
[Illustration: _A_ a typical crystal]
[Illustration: _B_ cross section showing the intersection of
cleavage planes]
[Illustration: _C_ and _D_ cross sections to show variations in
outline]
[Illustration: Tremolite in silky fibrous crystals. Asbestos]
[Illustration: Hornblende crystals in quartzite]
Plate 42
[Illustration: Epidote crystals]
[Illustration: Typical forms of epidote crystals; _p_ prism faces,
_m_, _n_, _x_, and _y_ beveled edges of the prism, _o_ octahedral
faces]
Typical forms of tourmaline
[Illustration: _A_ side view; _B_ and _C_ ends to show terminations;
_p_ prism faces, _m_ beveling of prism edges, _r_ a low rhombohedron
on the end, _s_ the opposite rhombohedron, _b_ basal face, and the
other faces represent bevelings]
Plate 48
[Illustration: A group of barite crystals]
[Illustration: Outline of the typical tabular barite crystal]
[Illustration: The six-sided double pyramid, composed of three
interpenetrating crystals, typical of witherite and strontianite]
Plate 44
[Illustration: The typical form of analcite]
[Illustration: A typical natrolite crystal]
[Illustration: The typical crystal form of stilbite]
[Illustration: A sheaf-like bundle of fibrous crystals, typical of
stilbite]
Plate 45
[Illustration: A group of calcite crystals]
Typical forms of calcite
[Illustration: _A_ the rhombohedron formed by cleavage]
[Illustration: _B_ a rhombohedral crystal truncated by the basal
plane]
[Illustration: _C_ the scalenohedron]
[Illustration: _D_ the scalenohedron truncated by the rhombohedron]
[Illustration: _E_ the scalenohedron on a prism]
Plate 46
Typical forms of aragonite
[Illustration: _A_ the simple crystal]
[Illustration: _B_ a needle-like form, twinned]
[Illustration: _C_ cross section to show how the form may appear
six-sided]
[Illustration: Typical form of the anhydrite crystal]
Plate 47
[Illustration: A piece of gypsum looking on the surface of the
perfect cleavage, and showing the two other cleavages as lines,
intersecting at 66°. Twinning is also shown]
[Illustration: A simple crystal of gypsum]
[Illustration: Twin crystals of gypsum]
Plate 51
[Illustration: Sulphur crystals]
[Illustration: Ice crystals, the top one, the end of a hexagonal
prism; the two lower figures multiple twins as in snow flakes]
Plate 52
[Illustration: The Devil’s Tower, Wyoming, an example of igneous
rock with columnar structure, and resting on sedimentary rocks.
Courtesy of the U. S. Geological Survey]
Plate 53
[Illustration: A coarse granite]
[Illustration: Graphic granite]
Plate 54
[Illustration: Syenite]
[Illustration: Gabbro]
Plate 55
[Illustration: Basalt-porphyry. The large white crystals are
phenocrysts of plagioclase feldspar]
[Illustration: Basalt-obsidian]
Plate 56
[Illustration: Amgydoloid]
Plate 57
[Illustration: The north face of Scott’s Bluff, Neb., showing
sedimentary sandstones above and clays below. The type of erosion is
characteristic of arid regions. Courtesy of the U. S. Geological
Survey]
Plate 58
[Illustration: Breccia]
[Illustration: Conglomerate]
Plate 59
[Illustration: Calcareous shale]
[Illustration: Coquina]
Plate 60
[Illustration: Foramenifera from Chalk; enlarged about 25 diameters]
[Illustration: Encrinal Limestone; fragments of the stems, arms and
body of Crinoids]
Plate 62
[Illustration: _A_ diatomaceous earth magnified 50 times]
[Illustration: _B_ and _C_ two diatoms from the above enlarged 250
times. After Gravelle, by the courtesy of Natural History]
Plate 63
[Illustration: A metamorphic rock, showing the contortion of layers
due to expansion under heat]
Plate 64
[Illustration: A conglomerate partly metamorphosed to a gneiss. Note
the flattened pebbles and the alternation of the intermediate
material to mica scales, etc.]
[Illustration: A typical gneiss]
Plate 66
[Illustration: Phyllite]
[Illustration: A white marble, with black streaks due to graphite]
Plate 68
[Illustration: Claystones, simple and compound]
[Illustration: A line concretion, which on splitting disclosed a
fern leaf of the age of the coal measures]
Plate 69
[Illustration: A septeria from Seneca Lake, N. Y.]
[Illustration: Pisolite]
Plate 70
[Illustration: A geode filled with quartz crystals]
Plate 71
[Illustration: A quartz pebble from the bed of a New England brook]
[Illustration: A pebble of schist and granite from the foot of Mt.
Toby, Mass.]
Plate 72
[Illustration: An iron-nickel meteorite, of 23 lbs. which fell in
Claiborne Co., Tenn.]
[Illustration: An etched slice of an iron meteorite which fell in
Reed City, Osceola Co., Mich.]
Plate 73
[Illustration: A stony meteorite, about natural size, which fell in
1875, in Iowa Co., Iowa]
PUTNAM’S
NATURE FIELD BOOKS
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Wild Birds and Their Music
Durand Wild Flowers in Homes and Gardens
My Wild Flower Garden
Common Ferns
Lutz Insects
Loomis Rocks and Minerals
Eliot Birds of the Pacific Coast
Armstrong Western Wild Flowers
Alexander Birds of the Ocean
Anthony North American Mammals
Thomas Common Mushrooms
Sturgis Birds of the Panama Canal Zone
Miner Seashore Life
Breder Marine Fishes of the Atlantic Coast
Morgan Ponds and Streams
Longyear Rocky Mountain Trees and Shrubs
Olcott Field Book of the Skies
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Transcriber’s Notes
—Retained publication information from the printed edition: this eBook
is public-domain in the country of publication.
—In the text versions only, text in italics is delimited by
_underscores_.
—Silently corrected a few typos.
—Reconstructed an image caption (Pisolite) on Plate 69.
—Generated a cover image based on elements in the book.