rtant deposits are
controlled by the large consumers of bauxite, principally the Aluminum
Company of America and its subsidiaries, though certain chemical and
abrasive companies own some deposits. The Aluminum Company of America
also controls immense deposits of high-grade bauxite in Dutch and
British Guiana, and further exploration by American interests is under
way.

With the return to normal conditions since the war, some of the domestic
bauxite deposits probably can not be worked at a profit, a situation
which is likely to require the development of the tropical American
deposits.

GEOLOGIC FEATURES

Aluminum is the third most abundant element in the common rocks and is
an important constituent of most rock minerals; but in its usual
occurrence it is so closely locked up in chemical combinations that the
metal cannot be extracted on a commercial scale. In the crystalline form
aluminum oxide constitutes some of the most valuable gem stones. Many
ordinary clays and shales contain 25 to 35 per cent alumina
(Al_{2}O_{3}), and the perfection of a process for their utilization
would make available almost unlimited aluminum supplies. The principal
minerals from which aluminum is recovered today are hydrous aluminum
oxides, the most prominent of which are bauxite, gibbsite, and
diaspore--the aggregate of all these minerals going commercially under
the name of bauxite.

Prior to the discovery of bauxite ores, cryolite, a sodium-aluminum
fluoride obtained from pegmatites in Greenland, was the chief source of
aluminum. It is only within about the last thirty-five years that
bauxite has been used and that aluminum has become an important material
of modern industry. Cryolite is used today to form a molten bath in
which the bauxite is electrolytically reduced to aluminum.

Bauxite deposits in general are formed by the ordinary katamorphic
processes of surface weathering, when acting on the right kind of rocks
and carried to an extreme. In the weathering of ordinary rocks the bases
are leached out and carried away, leaving a porous mass of clay (hydrous
aluminum silicates), quartz, and iron oxide. In the weathering of rocks
high in alumina, and low in iron minerals and quartz, deposits of
residual clay or kaolin nearly free from iron oxide and quartz are
formed. Under ordinary weathering conditions the kaolin is stable; but
under favorable conditions, such as obtain in the weathered zones of
tropical climates, it is brok