Mohave County miner., 1910-01-22

prediction was laughed at. Today
the great mines of Utah and Nevada
are going under this original estimate.
And now Arizona is coming in the
great porphyry- copper age, particular
ly in the Globe district and New
Mexico, with its Burro, Santa Rita
and San Andres mountain districts, is
Joining the ranks. But Michigan pre-
ceded the west in porphyry coppers,
as it had trap rock carrying as little
as l per cent of copper per ton worked
at a profit. But it was native copper;
whereas the western porphyries carry
sulphides, both copper glance and cop
per pyrites.
The famous deposits of Bingham,
Utah, are an enormous mass of mon
zonite porphyry, half mile wide, car
rying from per cent upward in cop
per, occurring as sulphides, and roughly
estimated to contain over 250,000, 600
tons, covered with leached out rock
or over burden from 30 TO 60 feet thick
Experimental plants for testing demon
strated that this ore could be mined,
on a large scale, and that 10 to 20 tons
could be concentrated into one tons of
high grade copper concentrates, which
could be shipped TO smelters at profit
of over Is ton.
And later the Utah Copper company
began the erection of a mill of 5000
tons daily capacity and demonstrated
that it could produce copper for eight
cents a pound.
Porphyry mining is carried on there
principally by open cuts, the ground
being first laid out in benches of
from 40 TO l2O feet high along the
slope of the mountain, and a line of
five-inch holes, 30 feet apart, being
drilled as far back from the face of the
ore as the explosives will easily break.
When the holes have reached the
level of the bench below, the ground
sprung or loosened by successive ex-
plosiOns of dynamite, which makes a
chamber at the bottom of each drill
hole, large enough TO contain the
breaking charge" which is from 20
to 80 boxes of black powder TO the
hole. The row of holes is then fired
simultaneously. and the whole mass of
rock is so broken up that it can be
handled by steam shovels. This is the
cheapest mining known in the world,
the ore being mined for less than %
cents a ton.
The magnitude of the operation may
be realized when it is stated that in
one mine six 90-ton steam shovels with
3 ton dippers are employed, and two
trains of four-ton dump cars being i'll
led AZ the rate of one a minute. Four
shovels have handled 1900 tons of
ore every day of 20 hours, or I75 tons
an hour for each shovel. Along with
this equipment are operated 10 steam
and five electric locomotives, carrying
to the mill 5000 tons of ore a day.
besides stripping and hauling away the
worthless over burden.
The concentrating mill has a capac
ity of 600 tons a day and will be in
creased to 10000 capacity. Ore con-
tanning only % pounds of copper ton
can he mined, milled. smelted and
marketed at a profit of LOSS a ton.
In other words, on this grand scale of
steam shovel mining, the ore is "manu-
factured'' into copper metal at from
seven to eight cents a pound.
In Arizona mines belonging to this
class are the Ray, claiming to have 49,
000,000 tons of ore blocked out: the
Miami with from 100000 to I5,OOO,-
900 tons; the Inspiration, and the New
Keystone and Live Oak and others.