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GOLD AND SILVER.
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The
total quantity of ore sold or treated from which gold or silver was
produced increased from 67,176,327 short tons in 1917, which was the
largest ever recorded, to 68,046,900 short tons in 1918. The total of
such ores has increased more than 17,500,000 tons in three years. In
1918 the quantity of copper ores sold or treated increased more than
4,360,000 tons; dry or siliceous ores decreased nearly 2,464,000 tons;
zinc ores more than 431,000 tons; copper-lead ores, nearly 16,000 tons;
lead-zinc ores, 441,000 tons; lead ores nearly 138,000 tons. Arizona,
Utah, Montana, and Nevada, led in quantity of ore, owing to the largely
increased output from copper mines, the ore from Arizona and Utah being
fnainly from low-grade disseminated ores and that from Montana mainly
from the Butte vein deposits. Nevada ore was mainly from Ely copper
ores, but also from siliceous ores from Goldfield, Tonopah, and other
districts. New Mexico, Alaska, California, Colorado, Idaho, and South
Dakota were next, with an output mainly of dry or siliceous ores from
many districts in Alaska, California, South Dakota, and Colorado, and
of copper ores from the low-grade ore bodies in New Mexico.
The
large production of lead and lead-zinc ores in Idaho ranked that State
before South Dakota, which produced ores that were mainly dry or
siliceous in character.
The
average extraction values in gold and silver were comparatively high
for the siliceous ores of Arizona, Colorado, New Mexico, Nevada,
Montana, Oregon, Utah, Idaho, Texas, and Washington, and low for the
larger ore bodies of California, South Dakota, and Alaska. Some of the
States produced comparatively small quantities of copper ore carrying
high extraction values in gold and silver, but the copper ores of the
important copper-producing States showed low extraction values. The
average recovery in gold and silver from the copper ores of Arizona was
$0.41 a ton, that of Tennessee $0.18 a ton, that of Montana $1.75 a
ton, that of Nevada $0.26, that of New Mexico $0.11, that of Utah
$0.22, that of California $1.09, and that of Michigan $0.18. The lead
ores of Utah showed an average recovery in gold and silver of $13.43 a
ton, and the lead ores of Idaho only $5.70 a ton. Idaho produced the
largest quantity of gold and silver bearing lead ores, and Montana the
largest quantity of lead-zinc ores. Utah yielded the next largest
quantity of lead ore, and the gold and silver content of such ore was
more than that of Montana ore of similar character. About 14.26 per
cent of the output of ore considered as producing gold and silver was
dry or siliceous ore, against 18.1 per cent in 1917; 78.5 per cent was
copper ore, against 73 per cent in 1917; 3.46 per cent was lead ore;
3.46 per cent was lead-zinc ore; 0.31 per cent was zinc ore; and 0.02
per cent was copper-lead ore. The average precious-metal extraction
value per ton of siliceous ores of the United States increased from $5.56 to $6.58, that of zinc ores decreased from $0.90 to $0.76, and
that of copper-lead ores increased from $14.58 to $16.19. The average
gold and silver value of copper ores per ton was 51 cents in 1916, 49
cents in 1917, and 50 cents in 1918, and that of lead-zinc ores
increased from $2.82 in 1917 to $3.47 in 1918.
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