of arsenic, orpiment and realgar, are formed
both as primary minerals of igneous source and as secondary products of
weathering. They are rather characteristic of the oxide zones of certain
arsenical metallic ores, and are believed in many cases to have formed
from arsenopyrite. They are mined on a commercial scale in China.

The great bulk of the world's arsenic, as previously stated, is obtained
as a by-product of smelting operations. The enargite of the Butte copper
ores (pp. 201-203) contains a considerable amount of arsenic, a large
part of which will be recovered from the smelter fumes by new processes
which are being installed. The gold-silver ores of the Tintic district
(pp. 235) also yield important amounts, the arsenic-bearing minerals
being enargite and tennantite (copper-arsenic sulphides) and others. The
silver ores of the Cobalt district of Ontario (pp. 234-235), containing
nickel and cobalt arsenides, produce considerable arsenic. Many other
metallic ores contain notable amounts of arsenic, which are at present
allowed to escape through smelter flues, but which could be recovered
under market conditions which would repay the cost of installing the
necessary apparatus.

BISMUTH ORES

ECONOMIC FEATURES

Bismuth metal is used in alloys, to which it gives low fusibility
combined with hardness and sharp definition. Bismuth alloys are employed
in automatic fire sprinklers, in safety plugs for boilers, in electric
fuses, in solders and dental amalgams, and in some type and bearing
metals. Bismuth salts find a considerable application for pharmaceutical
purposes, especially in connection with intestinal disorders, and the
best grades of bismuth materials are used for this purpose. The salts
are also used in porcelain painting and enameling and in staining glass.

Bolivia is the most important producer of bismuth ore. The output is
controlled entirely by British smelting interests. An important deposit
exists in Peru, the output of which is limited by the same British
syndicate. Considerable bismuth is produced in Australia, Tasmania, and
New Zealand, all of which likewise goes to England. Germany before the
war had three smelters which produced bismuth from native ores in
Saxony; bismuth was one of the few metals of which Germany had an
adequate domestic supply. Recently southern China is reported to be
mining increasing amounts of bismuth.

The United States produces the larger part of its bismuth requ