There
was a decrease of nearly 1,800,000 tons in the quantity of siliceous
ores treated in Alaska and California in 1918, compared with
1917,
though the gold content of the ore treated in 1918 was slightly
greater. The quantity of siliceous ore milled in South Dakota
decreased 86,000 tons and the recovery of gold was less.
COPPER ORES.
The
gold obtained as a by-product of the smelting of copper ores sold or
treated in 1918 was $6,387,974, against $7,051,523 in 1917, an increase
from 8.75 per cent of the total gold yield in 1917 to 9.62 per cent in
1918. The largest production was in Arizona, followed by Utah, Nevada,
Montana, California, in the order given. The largest decrease was in
California, Alaska, Utah, and New Mexico, caused by a smaller output of
copper in those States. As was expected, the increase in the production
of copper in Montana and Arizona in 1918 resulted in a recovery of gold
from copper ores nearly equal to the output from that source in 1916
from those States. The yield of gold from copper ores in 1919 will be
appreciably less than in 1918.
LEAD ORES.
The
production of gold in lead ores sold or treated in 1918, chiefly from
Utah and Colorado, was $1,142,036, against $1,415,274 in 1917, and
$1,486,754 in 1916, or 1.72 per cent of the total domestic output of
gold in 1918.
LEAD-ZINC, ZINC, AND OTHER ORES.
The
production of gold from lead-zinc ores was $870,132 against $765,316 in
1917, and $589,950 in 1916; from zinc ores $24,561 in
1918,
against $125,786 in 1917; and from copper-lead and copper-lead-zinc
ores $29,579 in 1918, against $92,480 in 1917. Utah, Montana, and
Colorado produced nearly all the gold from lead-zinc ores and Colorado
nearly all that from zinc ores. Nevada contributed nearly all the gold
from copper-lead ore.
DISTRIBUTION OF MINE PRODUCTION OF SILVER IN 1918, BY
SOURCES.
The
mine production of silver from the three most important sources of
silver—dry or siliceous ores, copper ores, and lead ores— was 88.6 per
cent of the total output in 1918, against 86.2 per cent in 1917. The
output from dry and siliceous ores increased 1.27 per cent in 1918,
following a decrease of 4.35 per cent in 1916 and 0.77 per cent in
1917; that from lead ores decreased 0.1 per cent; that from lead-zinc
ores decreased about 1.5 per cent; and that from copper ores increased
1.32 per cent. The combined output from placers, zinc ores, copper-lead
ores, and copper-lead-zinc ores was 0.66 per cent of the total
production of silver.
