e chief commercial source of bismuth.

The oxide, bismuth ochre, Bi2O3, and the sulphide, bismuth glance or
bismuthite, are also of commercial importance. The former is found,
generally mixed with iron, copper and arsenic oxides, in Bohemia,
Siberia, Cornwall, France (Meymac) and other localities; it also occurs
admixed with bismuth carbonate and hydrate. The hydrated carbonate,
bismutite, is of less importance; it occurs in Cornwall, Bolivia,
Arizona and elsewhere.

Of the rarer bismuth minerals we may notice the following:--the complex
sulphides, copper bismuth glance or wittichenite, BiCu3S3, silver
bismuth glance, bismuth cobalt pyrites, bismuth nickel pyrites or
saynite, needle ore (patrinite or aikinite), BiCuPbS3, emplectite,
CuBiS2, and kobellite, BiAsPb3S6; the sulphotelluride tetradymite; the
selenide guanajuatite, Bi2Se3, the basic tellurate montanite,
Bi2(OH)4TeOe; the silicates eulytite and agricolite, Bi4(SiO2)3; and the
urnayl arsenate walpurgite, Bi(UO2),(OH)24(A3O4)4.

_Metallurgy._--Bismuth is extracted from its ores by dry, wet, or
electro-matallurgical methods, the choice depending upon the
composition of the ore and economic conditions. The dry process is
more frequently practised, for the easy reducibility of the oxide and
sulphide, together with the low melting-point of the metal, renders it
possible to effect a ready separation of the metal from the gangue and
impurities. The extraction from ores in which the bismuth is present
in the metallic condition may be accomplished by a simple liquation,
or melting, in which the temperature is just sufficient to melt the
bismuth, or by a complete fusion of the ore. The first process never
extracts all the bisbuth, as much as one-third being retained in the
matte or speiss; the second is more satisfactory, since the extraction
is more complete, and also allows the addition of reducing agents to
decompose any admixed bismuth oxide or sulphide. In the liquidation
process the ore is heated in inclined cylindrical retorts, and the
molten metal is tapped at the lower end; the residues being removed
from the upper end. The fusion process is preferably carried out in
crucible furnaces; shaft furnaces are unsatisfactory on account of the
disintegrating action of the molten bismuth on the furnace linings.

Sulphuretted ores are smelted, either with or without a preliminary
calcination, with metallic iron; calcined ores m