The
total quantity of ore treated or sold in 1911 and producing gold and
silver was 35,522,890 short tons, against 31,717,912 tons in 1910 and
30,564,557 tons in 1909.
The
total output of dry or siliceous ores increased from 9,646,294 to
10,623,884 short tons, but decreased from 30.41 per cent of the total
in 1910 to 29.91 per cent in 1911. The average precious metal value
also decreased from $807 to $7.50 per ton.
The
quantity of copper ores increased from 19,145,677 to 21,384,408 short
tons, but the percentage of total output decreased slightly— from 60.36
per cent in 1910 to 60.20 per cent in 1911. The average precious metal
value per ton decreased also, owing largely to increasing tonnages of
low-grade copper ores mined, from $0.74 in 1910 to $0.67 in 1911,
following a similar decrease from $0.83 in 1909 to $0.74 in 1910.
The
output of argentiferous lead ores increased from 2,081,545 short tons
to 2,157,817 short tons, but the ratio of these ores to total output
decreased from 6.56 to 6.07 per cent and the average precious metal
value per ton fell off from $4.44 in 1910 to $4.39 in 1911.
The
production of gold and silver bearing zinc ores increased from 322,008
to 425,380 short tons, and the percentage of total output from 1.02 to
1.20 per cent, but the average precious metal content fell off from
$1.46 to $0.89 per ton.
The
output of copper-lead and copper-lead-zinc ores decreased from 20,318
to 6,923 short tons and the percentage of total output from 0.07 to
0.02 per cent, but the average precious metal value increased
