706 MINERAL RESOURCES, 1916----PART I.
The
total quantity of ore sold or treated and from which gold or silver was
produced increased from 50,513,452 short tons in 1915 to 66,388,402
short tons in 1916, the largest quantity of such ores ever recorded.
The total of such ores has increased more than 23,000,000 tons in two
years. In 1916 the quantity of copper ores sold or treated increased
more than 14,500,000 tons; dry or siliceous ores, more than 230,000
tons; zinc ores, 320,000 tons; copper-lead ores, 69,000 tons; and
lead-zinc ores, 800,000 tons. Arizona, Utah, and Mon tana continued to
lead in quantity of ore, owing to the largely increased output from
copper mines, the ore from Arizona and I tali being mainly from
low-grade disseminated ores and that from Montana mainly from the Butte
vein deposits. Nevada ranked next in output of ore, mainly from Ely
copper ores, but also from siliceous ores from Goldfield, Tonopah, and
other districts. Alaska, New Mexico, California, Idaho, and Colorado
come next, with an output mainly of dry or siliceous ores from many
districts in Alaska, California, 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 and California, which yielded ores that were mainly
all dry or siliceous in character.
The
average gold and silver extraction values were high for the siliceous
ores of Colorado, New Mexico, Nevada, Montana, Oregon, Utah, Idaho, 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 $0.35 a ton, that of
Tennessee $0.14 a ton, that of Montana $1.32 a ton, that of Nevada
$0.34, that of New Mexico $0.11, that of Utah $0.32, and that of
Michigan $0.22. The lead ores of Utah showed an average recovery in
gold and silver of $9.07 a ton, and the lead ores of Idaho only $3.98 a
ton. Idaho produced the largest quantity of gold and silver bearing
lead ores, and also lead-zinc ores. Utah yielded the next largest
quantity of these classes of ore, but the gold, and sdver content of
such ore was less than that of Montana ores of similar character. About
19.5 per cent of the output of ore considered as producing gold and
silver was dry or siliceous ore, against 25 per cent in 1915; 71.5 per
cent was copper ore, against 65 per cent in 1915; 3.58 per cent was
lead ore; 4.07 per cent was lead-zinc ore; 1.25 per cent was zinc ore,
and 0.12 per cent was copper-lead ore. The average precious-metal
extraction value per ton of siliceous ores of the United States
decreased from $6.26 to $5.73, that of zinc ores from $1.32 to $1.21,
and that of copper-lead ores from $15.55 to $5.54. The average gold and
silver value of copper ores per ton was 51 cents in each year, and that
of lead-zinc ores increased from $2.06 to $2.31.
DISTRIBUTION OF MINE PRODUCTION OF GOLD IN 1916, BY
SOURCES.
As
shown by the following table, the great bulk of the domestic output of
gold is obtained from dry or siliceous ore—normally gold quartz ana
gold-silver quartzose ores—and from placers, more than
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