(28 ECONOMIC GEOLOGY

tin lodes and at higher levels. The main production in
tecent years has been in the United States, which had an
output in 1924 of 13,000 tons; France was second with
10,000 tons; England produced 3200 tons from the Cornish
copper mines,
BisMUTH

Bismuth (Bi; at. wt, 208; sp. gr., 9-8; melting-point,
520° F. ; it expands 2-3 per cent. of its volume on solidification)
 is a white hard brittle metal, which is the most strongly
diamagnetic of the elements. It is chiefly found native or
as the sulphide, Bi,S,, bismuthinite. It is used mainly for
making fusible alloy, drugs, and pigments; as the demand
for it is limited and closely controlled production is small.
It is usually of deep-seated formation, and occurs in quartzveins
 associated with tin, tungsten, copper, gold, cobalt,
and uranium. As both the sulphide and carbonate are
relatively insoluble bismuth ores are not readily concentrated
in the surface zone. Owing to its insolubility it occurs in
alluvial deposits, and is obtained in Southern China from
tungsten placers. Saxony once had almost a monoply, but
its yield has become insignificant; the main supplies come
from Queensland, where it is obtained as a bye-product
from the tin and tungsten placers, and from Bolivia, where
it is obtained from tin mines. The price generally varies
from between 8s. 6d. to 12s. 6d. a lb.