so found in the oxide zone. The carrying down of lead in
solution and its deposition below the water table as a secondary
sulphide is not proved on any extensive scale. In this respect it
contrasts with zinc; and when the two minerals occur together, lead is
likely to be more abundant in the oxide zone, and zinc in the sulphide
zone below. Such a change in composition with depth is also found in
some cases as the result of primary vertical variations in the
mineralization.

ZINC ORES

ECONOMIC FEATURES

Zinc metal has commonly gone under the name of "spelter." Brass and
galvanized iron contain zinc as an essential ingredient. Of the total
United States zinc consumption in normal times, about 60 per cent is
used in galvanizing iron and steel objects to protect them from rust, 20
per cent is used in the manufacture of brass and other alloys, 11 per
cent goes into the form of rolled sheets for roofing, plumbing, etc., 1
per cent is employed in desilverizing lead bullion, and the remaining 8
per cent is used for pigments, electrodes, and other miscellaneous
purposes. During the war the use in brass-making was greatly increased.

The zinc content of the ores mined today ranges from a little over
1-1/2 per cent in the Joplin district of Missouri, to 25 per cent and
higher in some of the deposits of the Coeur d'Alene and other western
camps, and over 40 per cent in certain bonanzas in British Columbia and
Russia. The ores usually contain both zinc and lead in varying
proportions, and sometimes gold, silver, and copper are present. Of the
zinc produced in the United States, about 73 per cent is obtained from
ores containing zinc as the principal element of value, about 25 per
cent from zinc-lead ores, and 2 per cent from copper-zinc and other
ores. The average grade of the straight zinc ores is about 2-1/2 per
cent.

Of the world's zinc ore, the United States produces in normal times
about one-third, Germany about one-fifth, Australia about 15 per cent,
Italy, North Africa and Spain each about 5 per cent. The remaining 15 to
20 per cent comes from a large number of scattered sources, including
Japan, East Asia, Norway and Sweden, Canada, Mexico, Austria, France,
Greece, Siberia, and Russia. In the near future the Bawdwin mines of
Burma will probably be increasingly important producers. Large reserves
of zinc also exist in the Altai Mountains of southwestern Siberia, and
in the Cordilleran region of South America. In s