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252
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MINERAL RESOURCES.
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recorded
for most of the other States, notably Utah. The total silver production
from crude smeltmg ore increased from 28,487,837 fine ounces in 1910 to
29,831,111 ounces in 1911. The production of silver from this class of
ore increased notably in Alaska, Arizona, Idaho, Montana, Nevada, New
Mexico, and Utah, and fell off considerably in Colorado.
Under
the fifth item is given the quantity of old material, principally
slags and tailings, re-treated and their recoverable contents. These
are largely smelted, sometimes mainly for their fluxing values, but
increasing quantities of old tailings are now concentrated and
cyanided, as in the case of Cripple Creek. The concentrates produced
from old tailings, and their gold and silver content, are included
under "Concentrates produced." Comparison of the figures for 1910 and
1911 shows that the total quantity of this old material treated
increased from 334,637 short tons in 1910 to 412,346 tons in 1911, but
that the recovered gold content decreased from 30,323 to 16,259 fine
ounces and the silver recovery from 333,809 to 99,475 fine ounces.
From
this table the output of ore from the Central States, producing
insignificant quantities of silver and no gold, has been omitted. The
output of zinc ore from the Eastern States is also omitted, as this
zinc ore produces no silver or gold.
The
following table shows in summary the percentage of total output, by
processes, of gold and silver in the United States in 1911:
Percentage of output of gold and silver by processes in the United States in 1911.
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In
this table it is of interest to note that the mills contributed over
half the gold output but less than 16 per cent of the silver
production, and that the placers, the amalgamation and cyanidation
processes, and the smelters mainly supplied the gold production in four
nearly equal parts; but that the placers and the amalgamation process
contributed very small percentages of the silver output, the
chlorination process so small a fraction that it is not given, and the
cyanidation process less than 15 per cent—the great bulk of the silver
output, or more than 84 per cent, coming from the refining of smeltmg
products.
The
following table shows in greater detail the tonnage treated and output
of precious metals by gold and silver mills, by States, in 1911:
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