The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1913-12-18

opinent OF the Alaska Juneau prop
erty was undertaken, extensive open
pit mining was planned for summer
work, and for winter work reliance
was placed upon finding comparative
ly narrow widths In the vein that
would yield by selective underground
stopping $1.45 per ton; but as the vein
where exposed by the crosscut should
yield $l.70 per. ton, 1t Is now expected
that an average recovery of $1.45 per
ton will be obtained from the entire
vein when mining underground 5000
tons per day. This can be done at a
total cost Of not to exceed 80 cents
per ton, which cost per ton will be
somewhat reduced when eventually
mining $4,000 tons per day.
Mining.
Mining will be done under a COM
bination Of the Douglas Island meth
DDS with the caving system developed
in the adjoining Perseverance mine by
the former superintendent, ]. r. Nit
chell with the expectation of secur-
ing at least 100 tons of broken ore
per machine drill shift, as against ar
average Of 81 (29 to 34) tons in the
Douglas Island mines This differ
ence in duty per machine drill shift
Is due entirely to the difference in
composition of the two veins; the
Alaska Juneau being slate vein with
loose or free quartz stringers and
some metagabbro bikes between 8
greensboro foot wall and schist
hanging wall, while the Douglas Is
land vein is a solid, hard, tough dixie
Of diorite with frozen quartz string
ers without parting or selvage be-
tween the quartz and the enclosing
rock as in the Alaska Juneau slate
vein. The Alaska Juneau ore is very
much easier to drill than Douglas Is
land ore and will break with a less
consumption of powder per ton. Also
when blasted or caved, the Alaska
Juneau ore in the bottom of stopt
will In time, because Of air slakine
and the superimposed weight of add.
tional ore broken or caved from the
back Of the stope, crumble and crust
into pieces small enough to go through
chutes into ore cars; whereas, Tho
Douglas Island ore after being blastet
from the back of stope has to bC
both bulldozed and broken by sledges
in order to pass similar openings.
HauIage System.
THE trolley haulage system to bt
eventually installed in the present
crosscut and over the tramway from
1t to the millsite will handle 5000 tons
per day. In order to handle a tota
of $4,000 tons and over per day, q
sea level adit is now being driven
This, starting Immediately from the
millsite on the shore of Gastinea,
channel Gan arm of the ocean,, will b.
$500 feet long to reach the vein at Q
point 400 feet vertically below it's de.
velopment by the present crosscut
For this winters milling work. the ore
hauling will be done by gasoline To-
connective.
Milling.
Although the slate and the meta
gabbro each carry gold to the amour,
OF from rs to IS cents per ton, prac-
tically all the easily recoverable gold
Is in the quartz stringers which are
worth about So per ton. Experiment
al work has demonstrated that the
mill feed can be profitably enriched
by sorting out and roughing out the
waste even though there is some loss
In the gold contained by the waste
plus that contained by some ore thus
discarded. In the rock crushing house
1t Is expected that about 20 per cent
OF the waste will be trommeled off
with very little handling. This is be-
cause the quartz occurring as loose
or free stringers is more friable than
the slate and will break into smaller
pieces when going through rock
crusher with consequently more waste
than ore passing over the end of the
trommel; and very little hand sort
ing work on waste stacking belt at
the end of the trommel will prevent
the loss of any substantial amount of
ore.