of
the flotation concentrates are cyanided and not shipped to smelters.
This method was adopted by the Goldfield Consolidated Mines Co., which
had retained part of the cyanide plant for treatment of tailings and
the flotation concentrates.
It
is stated in the annual report of the Goldfield Consolidated Mines Co.
for 1917 that the treatment by cyanidation of concentrates recovered
by flotation was not profitable in that such flotation concentrates.
must be subjected to a chloridizing roast prior to the treatment by
cyanide. The flotation concentrates are now shipped to smelters.
The
smelters, which had for three years been producing each year a slightly
greater proportion of gold and a smaller proportion of silver, are to
be credited in 1917 with about 23.6 per cent of the total output of
gold and 83.1 per cent of the silver. The decrease in the per cent of
gold in 1917 was due to the smaller quantity of gold recovered from
crude ore smelted.
The
bulk of the production of gold remains mainly from the gold mills, but
in decreasing proportion. As shown by the table above the proportion of
gold recovered by amalgamation, cyanidation, and chlorination has
decreased from 53.6 per cent in 1912 to 50.6 per cent in 1917.
The following table shows in greater detail the ore treated and the output of gold and silver mills, by States, in 1917:
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