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250
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MINERAL RESOURCES, 1912.
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The
total output of dry or siliceous ores decreased slightly, from
10,623,884 tons in 1911 to 10,584,777 tons in 1912, and the percentage
of the total of this class of ore fell from 29.9 to 25.8 The average
precious metal value also decreased from $7.50 to $7.40 per ton. All
these percentage and value decreases are in continuation of similar
decreases in 1911 and indicate a downward movement in relative tonnage
and average value of these ores. The latter change is the more
significant when the higher price of silver in 1912 is taken into
account.
Of
the total output of 10,584,777 tons of dry and siliceous ores, the bulk
were gold-silver ores, but 848,574 tons were true silver ores. Of
these, 158,429 tons were produced in Colorado, 476,725 tons in Nevada,
110,127 tons in New Mexico, 20,375 tons in Texas, 81,234 tons in Utah,
and smaller quantities in Arizona, California, Idaho, Montana, Oregon,
and Washington, in 1912.
The
quantity of copper ores treated increased from 21,384,408 tons in 1911
to 26,761,390 tons in 1912, following a similar increase in 1911. The
average precious metal content decreased, however, from $0.67 to $0.63,
following a similar decrease since 1910. These figures are in harmony
with the increase in relative output of copper ores, from 60.2 per cent
of the total in 1911 to 65.12 per cent in 1912, owing to the largely
increased output of low-grade ores in recent years.
The
output of argentiferous lead-ores increased also from 2,157,817 tons in
1911 to 2,388,598 tons in 1912, but the relative production of these
ores decreased from 6.07 to 5.82 per cent of the total, both of these
changes being in continuation of corresponding changes in 1911. The
average precious metal value of the ore increased from $4.39 to $4.85,
more than offsetting a decline in 1911 from $4.44 in 1910.
The
production of gold and silver bearing zinc ores decreased from 425,380
to 377,737 tons, and the relative output from 1.20 to 0.92 per cent of
the total, but the average precious metal value increased from $0.89 to
$1.35. All of these changes were opposite to those of 1911.
The
output of copper-lead and copper-lead-zinc ores increased from 6,923 to
14,614 tons, and the average precious metal tenor from $25.17 to $30.80
per ton. These ores have the highest average richness of all in
precious metal but they form only 0.03 per cent of the total output of
ore that yields gold and silver. The production of lead-zinc ores
increased from 924,478 to 967,690 tons and the average precious metal
tenor from $1.80 to $2.05 per ton, but the relative percentage of
output of these to total ores decreased from 2.60 to 2.35 per cent.
The
production of dry and siliceous ores increased from 1,594,404 to
1,761,814 tons in Alaska, from 1,874,103 to 1,966,300 tons in Colorado,
and from 1,341,495 to 1,400,728 tons in Nevada. It decreased from
2,296,347 to 2,225,429 tons in California, from 1,945,770 to 1,901,459
tons in South Dakota, from 369,241 to 298,308 tons in Montana, and from
464,229 to 369,736 tons in Utah. The great output of this class of ore
is notable from Alaska, California, Colorado, Nevada, and South
Dakota, and is mainly from the well-known Treadwell, Mother Lode and
Grass Valley, Cripple Creek, Goldfield and Tonopah, and Homestake
mines, respectively, in these States.
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