canyon
is about 265 feet below the mouth of the old shaft on the cliff. The
main drift has been carried to the east nearly 500 feet, with many
hundred feet of levels and stopes above. The dike is somewhat irregular
in shape and contains alternate rich and barren portions. The latter
seem to be due, in places, to abundant inclusions of limestone, while
in other places the dike pinches around projecting portions of the
limestone walls. The outcrop of the dike in the foot of the canyon wall
was not at first located, since it was rather indefinite and was partly
covered with large blocks of talus. A crosscut tunnel was driven from
the north side until the dike was located, and from this the main drift
was carried eastward on the one side, and the dike traced to its
outcrop in the canyon wall on the other. A large body of pay rock,
apparently over 45 feet wide, was located by the crosscut and drift.
Though the relation of this ore body to the dike was not definitely
known at the time of the writer's visit, it seemed to cut across the
regular dike with a dip of about 40° to the east. No definite hanging
wall had been located, though the pay streak was about 12 feet thick
from the foot wall. This body of ore had been brecciated and the broken
masses squeezed into slickensided lenses.
The
mine is equipped with a track running to the mill near by. The track is
protected between these points by a shed, in order that severe weather
may not interfere with operations. The ore is handled in steel dump
cars of improved pattern.
The
method of treating the sapphire ore is quite different from that used
by the New Mine Sapphire Syndicate, the ore receiving special mill
treatment soon after mining. It has been found that over 50 per cent of
the ore removed by blasting is fine enough for milling without
disintegration by weathering. The ore direct from the mine, after
passing through 4-inch grizzlies, is digested with water in heavy
revolving screens. The latter discharge three classes of material, the
fines or slimes, which are immediately discarded, the oversize or
material still in lumps, which is saved for further treatment, and the
digested matter ready for sizing and concentration. The lump material
is left in stock piles to weather for a period of several months, by
which time it is readily digested in the revolving screens and
concentrated. After sizing, the digested material is concentrated on
Woodbury jigs arranged to treat three sizes, three-fourth and
three-eighth inch and 6-mesh. Two jigs are run in series for safety.
These jigs were handling about 75 tons in a day of seven and one-half
hours at the time of the visit, though from 200 to 225 tons could be
treated in twenty-four hours.
The
concentrates from the jigs, in rare cases, run as high as 30 per cent
sapphire, 5 to 10 per cent being more common. The concentrates
containing the watch-jewel sizes, or culls, are treated on a
Blake-Morscher electrostatic concentrator and their, grade brought up
to between 50 and 90 per cent sapphire. The final cleaning, as with the
larger sizes suitable for cutting, is accomplished by hand picking. In
filling hurry orders this cleaner is or value, since it enables a large
quantity of sapphire to be selected much more quickly than could be
done by hand alone. On the other hand, part of the sapphire goes over
with the tailings, which require more labor to pick over than the
original concentrates.
The operations of the American Sapphire Company have not yet reached the capacity of the plant, since much time has been con-
