desian,
Russian, Turkish, and Indian ores are also of high grade. The ores mined
in the United States, Canada, Brazil, Cuba, Greece, and Japan are of
lower grade.

The use of domestic chromite supplies in the United States presents much
the same problem as does manganese. The ore bodies are small, scattered,
and of a generally law grade. War-time experience showed that they could
be made to meet a large part of the United States requirements, but at
high cost and at the risk of early exhaustion of reserves. California
and Oregon are the principal sources, and incidental amounts have been
produced in Washington, Wyoming, and some of the Atlantic states. With
the resumption of competition from foreign high-grade ores at the close
of the war, the domestic mining industry was practically wiped out; the
consequences being financial distress, partial direct relief from
Congress, and consideration of the possibilities of a protective
tariff,--which in this case would have to be a large one to accomplish
the desired results (see Chapters XVII and XVIII).

GEOLOGIC FEATURES

The principal chrome mineral is chromite, an oxide of chromium and iron.
Chromite is a common minor constituent of basic igneous rocks of the
peridotite and pyroxenite type. In these rocks it occurs both as
disseminated grains, and as stringers, and large irregular masses which
probably represent magmatic segregations. Alteration, and weathering of
the parent rock, forming first serpentine and then residual clays, make
the chromite bodies progressively richer and more available, by leaching
out the soluble constituents of the rock leaving the chromite as
residual concentrates. All the important chromite deposits of the world
are associated in somewhat this manner with serpentine or related
rocks. They are formed in the same way as the lateritic iron ores of
Cuba, and from the same sort of rocks (pp. 171-173). Chromite is very
insoluble, and the mechanical breaking down of deposits and
transportation by streams frequently forms placers of chrome sands and
gravels. Such placers have not been worked to any extent.

Katamorphic processes give the important values to chromite deposits.

NICKEL ORES

ECONOMIC FEATURES

The principal use of nickel is in the manufacture of nickel steel, the
most important of all alloy steels. Ordinary nickel steels carry about
3-1/2 per cent nickel. Nickel is used in all gun and armor-plate steels,
and in practically