880 MINERAL RESOURCES, 1913—PART I.
The
concentrates are mainly smelted, as stated, but are in some cases
treated in gold and silver mills by the processes named. Comparison
with corresponding figures published by the Survey for earlier years
shows that the total tonnage treated in straight concentrating mills
(for concentration only) increased from 15,407,515 tons in 1910 to
17,602,315 tons in 1911, to 22,207,305 tons in 1912, and to 27,088,716
tons in 1913. The greater part of the increase in 1912 was in Arizona
(from 4,327,705 to 5,141,337 tons), in Idaho (from 1,985,527 to
2,126,535 tons), in Montana (from 4,497,240 to 4,930,632 tons), in
Nevada (from 3,010,976 to 3,451,549 tons), in New Mexico (from
1,142,002 to 1,987,896 tons), and in Utah (from 6,477,567 to 8,883,379
tons), and with the exception of Idaho and Montana indicates chiefly
increased tonnages of low-grade disseminated copper ores mined. In
Idaho and Montana the increase was largely in lead-zinc ores. The total
quantity of gold and silver bearing concentrates produced in all
classes of mills increased from 2,597,992 tons in 1910, to 2,773,870
tons in 1911, to 3,303,655 tons in 1912, and to 3,786,031 tons in 1913.
The chief increases in 1913 were from 411,627 to 454,393 tons in
Arizona, from 232,347 to 269,400 tons in Idaho, from 353,563 to 501,888
tons in Nevada, from 81,811 to 198,243 tons in New Mexico, and from
381,358 to 525,900 tons in Utah. The total recoverable gold content of
all concentrates aggregated 473,788 ounces, valued at $9,794,069, in
1913, against 494,980 ounces, valued at $10,232,144, in 1912, against
484,971 ounces in 1911, and 475,452 ounces in 1910. The recoverable
gold content in concentrates increased chiefly in Arizona, California,
and Oregon, and mainly decreased in the other States given. The
decreases were mainly due to lowered grade of siliceous gold and silver
ores milled and were not offset by large increases in low-grade copper
ores milled. The total recoverable silver in concentrates produced
aggregated 24,045,405 ounces in 1913, against 22,322,239 ounces in
1912, against 20,794,441 ounces in 1911 and 19,949,379 ounces in 1910.
The increased output was most notable in Idaho (from 5,402,543 to
6,720,969 ounces), in Montana (from 8,597,953 to 9,100,418 ounces), and
in Oregon (from 37,434 to 132,778 ounces), and was due mainly to
increased output of argentiferous lead and zinc concentrates.
The
fourth item covers the quantity and recoverable precious metal content
of crude ores shipped from the mines direct to smelters, and in general
includes the richer gold, silver, copper, lead, and zinc ores from
which the gold and silver are eventually recovered bv refining the
copper or lead bullion that collects the precious metals in the
smelting. The total quantity shipped of this class of ore decreased
from 6,016,425 tons in 1910 to 5,588,771 tons in 1911, increased to
6,543,436 tons in 1912, and increased again to 7,109,088 tons in 1913.
The increase in tonnage for 1913 as compared v,ith that oi 1912 was
mainly in Arizona (irom 2,140,008 to 2,425,962 tons), in California
(irom 456,735 to 531,189 tons), in Colorado (from 617,726 to 664,998
tons), in Nevada (from 376,800 to 399,178 tons), and in the Eastern or
Appalachian States (from 605,951 to 653,150 toes). The decrease was mainly in Montana (from 839,383 to 811,765 tons). The tonnages have been notably large hi
Arizona and Utah. The total gold output from crude ores smelted
decreased from 623,272 fine ounces in 1910 to 611,344 ounces in 1911,
to 578,391
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