The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1914-03-12
(From Speech of S. J. Jennings Before
Mining aud Mafa 1lurpipaI SopiptV)

(From Speech of S. ]. Jennings Before
Mining and Metallurgical Society
The most dramatically interesting
developments in the mining anc mes
allurgy Of precious metals are taking
place back of Juneau, Alaska. A zone,
about 10000 feet long by 1000 feet wide
in it's widest point is being developed
by three companies. the Alaska Cas-
tineau, which owns about 10000 feet
along the strip, the Alaska juneau,
which owns 5000 feet. This zone con-
ssts of belt of slate in which quartz
lenses and stringers occur with more
or less irregularity. The gold con-
tents in the pure quartz, that is, in the
center of the lenses, are practically
negligible, and the gold In the slate it.
self is also small in amount. The gold
seems to occur chiefly at the contact
between the quartz and the slate. AS
says as high as $50 per ton for a
width of 5 inches have been obtained
but recovery Of $3.50 is estimated for
the whole mass that will be mined.
How the Ore Is Mined.
Naturally, the method of mining
such deposit, and the costs that Will
be incurred in mining, have received
great amount of attention. In the
case of the Gastineau a system has
been worked out which promises fav-
orable results The foot wall OF the
deposit, 50 far as developed in this
property, is fairly well defined by the
fact that quartz lenses and stringers
occur with greater persistence ana
regularity on the foot wall than any
where else This wall dips approx
mately So degrees and it is estimated
that the silcifcation of the slate ex-
tends out for an average of 30 feet
from the foot wall, although many OF
the crosscuts show a much greater
width than this. A drive is carried
parallel to the foot wall in the country
rock. At height Of about 80 feet
above this drift a parallel drift is like
wise carried in the foot wall. This
upper drift is called 'chute tenders
drift Crosscuts from it at intervals
of from 80 to so feet are driven into
! the vein. From these crosccuts slopes
are opened out or s feet high and for
the full width of the vein, say 80 feet,
and the ore broken in these slopes is
mucked into the chutes which lead
! 1n
level. Slopes are then raised on the
foot wall of the vein for from 20 to %
feet high, and at the end of a stope
say 200 feet long, the vein is stopped
clear across from the footwall for as
great distance as commercial recov-
cries are found There is thus pre-
pared a block of ground about 200 fee
long by 20 to 25 feet high, which is
undercut on the bottom, on the foo
wall side, and at two ends and expert
ence has proved that this block o
ground will cave. The roof that re-
mains after it has dropped, gradual,
approximately at right angles to tn
foot wall, when it is quite safe agail
for men to enter on the top of tn
broken ground and start their foo
wall Slope once more. Thus actuall
only one fifth of the ore sent to mil
has to be mined, the remaining four
fifths breaking itself
Sounds Like Fairy Story.
Such a statement seems like a fair
, tale. 1t did to me when it was frs
made but after having examined tn
Slopes where some 100000 tons ha
been broken by this method, I am in
clined to believe, under the condition
existing, and with the amount Of sill
cification of the slate so far expose
by development, that the scheme vii
work.
Grizzlies are laid on top Of tn
chutes before mentioned, and SHOULD
these grizzlies become blocked b.
large humps. the chute tender goini
along the drift can In perfect safet
bulldoze such Jumps and keep tn
chute filed. These chutes are design
ed to hold 1875 tons--approXimat tel
one trainload.
Transporting to the Mill.
The train will consist of flat car
and will be trammed either by endles
wire rope, or by electric locomotive t
the main chutes, where the ore will b.
, plowed, off the cars by stationar.
pillow and dropped to the Sheep creel
tunnel level. At the start this drop vii
be some 400 feet. since the working o
the mine will noturaly commence a
the part of the vein near the outcror
The ore on the Sheep creek TUNE
level will be hauled in trains by cleo
trio locomotives to the MILL located OF
Gastneau channel. In the mill the or
will be broken in crushers and roll
and a large proportion roughed off
leaving only a small percentage to b
finely ground amalgamated and con
; centrated.
Rolls to Crush Ore.