The
quantity of siliceous ores treated in Alaska and South Dakota in 1920
increased, but the recovery of gold per ton was slightly less; the
siliceous ore in California decreased about 424,000 tons, but the gold
recovery per ton was the largest recorded for seven years.
COPPER ORES.
The
gold obtained as a by-product in the smelting of copper ores sold or
treated in 1920 showed a decrease in quantity but an increase in
percentage of the total gold yield. The largest producer was Arizona,
followed by Utah, Nevada, Montana, Oregon, and New Mexico.
LEAD ORES.
The
gold in lead ores sold or treated in 1920 came chiefly from Utah,
Colorado, and Arizona, and showed an increase over the output in 1919.
LEAD-ZINC, ZINC, AND MIXED ORES.
The
production of gold from lead-zinc ores in 1920 decreased, and that from
zinc ores, and copper-lead, and copper-lead-zinc ores increased. Utah,
Colorado, and Montana produced nearly all the gold from lead-zinc ores
and Montana nearly all the gold from zinc ores. Nevada, Colorado, and
Utah contributed nearly all the gold from copper-lead ore.
DISTBIBUTION OF MINE PRODUCTION OF SILVER IN 1920, BY
SOURCES.
Mine production of silver in 1920, in fine ounces.
