MINERALS. 141

 

SECTION LIE

MINERALS.

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GHA PT Et.

- Minerals.

868. General Distribution of Minerals—The
distribution of the various mineral substances
that form parts of the earth’s crust, unlike the
distribution of the earth’s plant and animal life,
is independent of the distribution of heat and
moisture. Mineral products, therefore, cannot be
arranged in zones, according to latitude and alti-
tude, as can the plants and animals.

The absolute dependence of plants and animals on the
distribution of heat and moisture necessarily limits them
to those parts of the earth in which the requisite condi-
tions exist. Moreover, while some animals, to a certain
degree, possess the ability to become acclimated, that is,
to accommodate themselves to changes in climate, yet
they are necessarily limited to the regions in which the
vegetable food exists on which they are directly or in-
directly dependent. Mineral substances, on the contrary,
are not, to any marked degree, dependent on existing cli-
matic or surface conditions, since the conditions under
which they were formed or deposited no longer exist.

Since some mineral substances are practically limited
to certain geological formations, a fairly good distribution
might be based on the geological strata, were it not for
the fact that, in many cases, through the agency of ero-
sion, such substances have been distributed through the
rocks of later formations. Moreover, in many cases, the
mineral products are found in nearly all the geological
formations. No attempt, therefore, will be made to
arrange the earth’s mineral products in characteristic
zones or regions. ;

369. Value of Mineral Products.—The civil-
ization of man is largely dependent on the char-
acter and extent of the earth’s mineral products.
His progress would have been seriously retarded
had the earth contained no metallic substances
from which he could fashion tools, build machines,
form the rails for steam and electric roads, or the
electric conductors for telegraph, telephone, elec-
tric light and power lines, and had he no metals
suitable for coining or, for ornamentation. Had
no stores of energy been placed in the earth’s
crust for his use, in beds of coal, in peat-bogs, or
in recesses filled with coal-oil or natural gas, or

 

did he fail to find among the earth’s mineral
treasures, beds of sandstone, granite, marble or
other similar materials with which to build his
houses, his ability to adapt himself to various
climates would have been seriously restricted.
Moreover, if the mineral products now employed
for their medicinal or curative properties were
denied to him, life and health would have been
markedly decreased.

370. Varieties of Mineral Substances.—Min-
eral substances occur in a gaseous state, as in
natural gas; in the liquid state, as in petroleum
or coal-oil; and in the solid state, as in the
various building stones, coal, rock-salt, and metal-
lic ores generally. The solid state is by far the
most common. Mineral substances occur at
varying depths and are obtained by different
mining processes. Sometimes, as in the case of
gold, the mineral occurs near the surface, in beds
of sand or gravel. Here, hydraulic mining, or the
washing away of the deposits by powerful streams
of watzr, may be adopted. -Generally, however,
the deposits occur at fairly considerable distances
below the surface, in which case shaft-mining is
necessary ; 7%. é., pits, shafts, or galleries are cut
through the crust so as to reach the deposits.

Building stones are generally obtained from

- open cuttings or quarries, since the cost of taking

out such substances from great depths would be
restrictive. It is generally believed that large
and valuable metallic deposits exist at depths
below which mining operations have, as yet, been
carried on.

871. Classification of Mineral Products—For
convenience of study, mineral products may be
divided into the following classes:

(1.) The metals and their ores.

(2.) Coal, peat, coal-oil and natural gas.

(8.) Clay, kaolin, marls, salt, sulphur and
graphite.

(4.) Building stones.

(5.) Precious stones or gems.

372. The Metals and their Ores——The most
important metals are gold, silver, platinum, iron,