12.83
at Ely, in Nevada; 3.04 at Magdalena, in New Mexico; 17.32 at Shatter,
in Texas; and 11.93 at Frisco, 21.01 at Tintic, 7.38 at Bingham, 10.18
at Rush Valley, and 20.32 at Park City, in Utah. The general high
average content of silver in lead ores is characteristic, the notable
exceptions being in the Ccsur d'Alene.
DISTRIBUTION OF GOLD PRODUCTION OF 1911, BY SOURCES.
As
shown in the following tables, the great bulk of the gold output is
from dry or siliceous ores—normally gold-quartz ores—and placers. In a
later report it is hoped some detailed data may be presented showing
variations in gold content of placer gravels and of gold-quartz ores in
the different mining districts of the United States and Alaska.
Nearly
93 per cent of the total gold production of the United States is from
tlie combined contributions of the placers and the deep mines producing
dry or siliceous ores. The output of gold derived from the great copper
and lead mines of the United States is therefore relatively small. The
relative proportion of output by sources showed little change in 1911
from 1910. It is interesting to note, however, that 24.17 per cent of
the gold production came from placers in 1911, against 23.76 per cent
in 1910, and that 68.52 per cent came from dry or siliceous ores,
against 68.91 per cent in 1910. Normally changes would be expected in
opposite directions. There was decreased relative output from copper
ores, also, and increased relative production from lead ores.
Tlie
following tabic shows the sources by classes of ore by States of tlie
gold output in 1911, and for comparison the corresponding total figures
for the United States for 1910:
Source
of gold in 1911 in States and Territories, as reported from the mines
to the United States Geological Surrey, by hinds of ore and by States,
in fine ounces.a
