The
output of copper ores increased from 4,274,209 to 6,542,154 tons in
Arizona, from 2,375,000 to 2,500,000 tons in Michigan, from 4,332,479
to 5,094,432 tons in Montana, from 2,778,325 to 3,276,169 tons in
Nevada, from 69,305 to 1,195,683 tons in New Mexico, from 581,974 to
603,229 tons in Tennessee, and from 6,121,099 to 6,670,845 tons in
Utah. There was no important decrease of copper-ore output in 1912.
The great production from Utah, Nevada, New Mexico, and in part from
Arizona is largely from disseminated deposits, that of Butte (Montana)
from fissure deposits, and that of Michigan from the amygdaloid and
conglomerate deposits of the Keweenaw districts.
The
output of precious-metal-bearing lead ores increased from 158,984 to
182,745 tons in Colorado, from 1,559,724 to 1,597,661 tons in Idaho,
and from 393,029 to 498,401 tons in Utah. There were smaller increases
in Montana and Nevada also, and no important decreases in 1912. The
production of argentiferous zinc ores increased from 110,845 to
177,946 tons in Colorado, but decreased from 225,586 to 136,552 tons in
Montana. The production of argentiferous lead-zinc ores increased from
214,385 to 229,107 tons in Colorado and from 397,354 to 480,126 tons in
Idaho, but decreased from 280,817 tons to 216,764 tons in Utah.
The
average extraction value of precious metals per ton of dry or siliceous
ore increased in Alaska from $2.66 in 1911 to $2.85 in 1912, in
California from $4.57 to $4.95, and in South Dakota from $3.87 to
$4.21; but it decreased in Colorado from $11 to $10.53, and in Nevada
from $18.12 to $14.74.
The
average extraction value of gold and silver per ton in copper ores
increased from $0,111 in 1911 to $0,211 in 1912 in Michigan, and from
$1.32 to $1.42 in Montana, remained the same at $0.18 in Nevada in both
years, and decreased from $0.51 to $0.41 in Arizona, from $1.70 to
$0,275 in New Mexico, and from $0.60 to $0.56 in Utah. The average
precious-metal value of lead ores increased from $2.45 to $2.78 in
Idaho, but decreased from $9.55 to $8.67 in Utah. In zinc ores the
value increased from $0.30 to $0.51 in Colorado, and from $1.23 to
$1.98 in Montana. In lead-zinc ores the value increased from $2.16 to
$2.17 in Colorado, and from $2.93 to $4.48 in Utah, but decreased from
$0.70 to $0.68 in Idaho.
AVERAGE TENOR OF SILVER IN ORES, BY MINING DISTRICTS.
In
the general Survey report on gold and silver by the writer for 1911 the
results were given of a brief study of the tenor of silver in ores by
mining districts. A few copies of that report are still available for
distribution.
The
bulk of the silver production, as shown, is from more widely
distributed sources than that of gold, the placers and mixed ores
playing little part, but the dry or siliceous silver, silver-gold, and
gold-silver ores, the copper ores, and the lead ores contributing more
equally in the product. The relatively high tenor of many dry or
siliceous and lead ores (with the notable exception of the lead ores of
the Cceur d'Alene) are shown, as well as the relatively high tenor of
silver in the copper ores in the Chitina region, Alaksa, and the Lead-
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