Lode
mines of California, the Alaska mines of the Juneau district, and the
Cripple Creek and upper San Miguel County mines in Colorado. The great
gold-dredging fields of California, especially of the Marysville
district, are examples of the placer gravels worked on a large scale. A
considerable output of gold is also now recovered from the refining of
copper bullion from copper ores, especially of the West Mountain or
Bingham district, Utah, and the Summit Valley or Butte district, Mont.
In 1918 the copper ores of the United States produced more than 9.6 per
cent of the total gold, against 8.7 per cent in. 1917. The natural
tendency is for the proportionate output from gold ores to decrease
with declining yield from some of the principal gold camps and for that
from copper ores to increase, with a general net falling off of total
yield of gold owing to the preponderant output from gold and
gold-silver ores.
The
principal domestic supply of new silver came from dry or siliceous
silver and silver-gold ores, copper ores, lead ores, and lead-zinc ores
in the proportion of 31.7, 30, 26.9, and 10.7 per cent, respectively,
in 1918, against 30.4, 28.8, 27, and 12.2 per cent, respectively, in
1917. The dry or siliceous silver-gold ores have come chiefly from four
large mines of the Tonopah district, Nev., and declining output from
this camp more than offsets gains from such ores elsewhere. The bulk of
the silver ores of this class are milled and cyanided at or near the
mines, although a small quantity of richer ores is shipped to copper
and lead smelters. The largest single producer of silver in 1918 from
domestic mines was the Anaconda Copper Mining Co., of Montana,
producing from copper ores; the second largest was the Chief
Consolidated Mining Co., of Utah., producing from lead ores; and the
third largest was the Butte & Superior Mining Co., of Montana,
producing from lead-zinc ores. Of the 25 mines or groups of mines
producing silver on the largest scale, 5 were silver-gold and silver
mines, 7 were copper mines, 11 were lead mines, and 2 were zinc-lead
mines. With large recent increase in output of argentiferous copper,
lead, and zinc-lead ores, the domestic silver output has been fairly
well maintained against decline from silver-gold and (the rare) silver
ores. Tne silver obtained as a by-product from copper, lead, and zinc
ores is derived from refining the copper and lead bullion produced in
smelting those and other ores.
WORLD'S PRODUCTION OF GOLD.
Value of gold produced in the Ivorld, 1860-1918.
[The
annual production from I860 to 1872 is obtained from statistics for
5-year periods compiled by Dr. Adolph Soetbccr. Since 1872 the
estimates aro those of the Bureau of the Mint. See PI. VII.]
