The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1917-08-09

by itself, but general description o
the common practice may be an ait
in sampling. Zinc properties ar.
sampled, in general, in two ways, ac'
cording to the nature of the deposi
and the amount of development; b.
making cuts across the face of the
vein or deposit, or by drilling with &
churn or diamond drill. The former
method is commonly used in veins, the
other in sampling sheet deposits such
as those of the Joplin district.
An engineer may be called upon tc
make an examination of a zinc pro-
perty, which may be anything from q
prospect without development to a
fully developed mine with ore reserves
already blocked out. If it is of the
vein class, his aim will be to get
samples from across the vein at GER
tain distances along the strike and
dip. This is not such a difficult mat
ter provided the vein is sufficiently
opened up, but when the deposit is
simply an irregular mass, it is a diff
cult matter and his chief aim will be
to sample the deposit at regular in
tervals.
In the case of a prospective pro-
perty that has not been opened below
the surface, all that can be accom-
plished in the way of sampling is to
dig trenches across the deposit at GER
tain distances from each other. These
trenches will not necessarily be at
right angles to the dip or strike of
the orebody, but will show what there
is near the surface. 1t is only hazard
as to what to expect farther down.
General Underground SampIins.
Some mines are sampled every five
or ten feet along the vein by taking
samples from the floor or the roof of
the drifts and at like distances in the
shafts, wines or raises when in the
vein. These samples are generally
from 81 or Ain. wide channel cut in
the ore with a single-ja jack and CAD.
They weigh from to 40 pounds each
and are placed in canvas sacks and
tagged. AS a rule the engineer marks
the samples simply by number and
records the sample number on blue
print of the mine plan, which makes
reference easy and convenient, the
samples representing the grade of the
ore in place in the mine.
The samples must be reduced to a
convenient size and mesh for analysis
and also dried. The best manner in
which to reduce the sample is to first
grind it in a small jaw-crusher to
about "a in. diameter; then dry, mix
and reduce the quantity by quartering
to 10 pounds. This can be further
reduced to 30-mesh in coffee mill'
and riffied to u pound and then pull
verified in disk pulverizer or on a
bucking board until all the pulp will
pass through 100-mesh screen. The
final sample of 4 ounce is placed in an
envelope or paper bag and properly
marked and is ready for analysis.
The type of mineral deposit occur
ing in the Joplin district may be sam
pied by drilling with a churn drill.
Holes are spaced at regular intervals
and the drillings removed from the
hole with sand pump. After the
drill gets down into the ore, these
drillings may be emptied into tub
and allowed to settle, the water drain
ed off, the sample washed into a pan,
dried, mixed, any Jumps reduced and
ground to 30-mesh, riffied to a quarter
pound and pulverized to pass through
a 100-mesh screen, when the sample
is ready for analysis.
Similar deposits may be drilled with
the diamond drill and the part of the
core containing mineral matter re-
duced. OF course, in any kind of
sampling sufficient data as to dis
tances, locations. etc., must be kept
so as to insure complete record, from
which measurements the engineer
bases his calculations of the tonnage
in place, and from the analysis of the
samples the value of the ore.
Other Mine Samples.
There are many old dumps through
out the country containing zinc, and
it is another problem for the engineer
to obtain representative sample from
them upon which to base the calcula-
ton OF their value. The two accepted
methods are the pipe and the opencut
methods. The former can be used
only when the ore has been broken
finer than a 3-in. cube, when it is fea-
sible to drive a Sin. pipe into the
dump and withdraw 1t filled with ore.
The other method, the use of the
trench, consists in digging down the
walls of the trenches for the samples,
which may then be crushed, quartered,
ground, mixed, riffied and pulverized
for analysis In case the pile of ore is
very high and in form of a cone, the
trenches can be dug from the perl
phery and down from the top.
After the mine or prospect has
reached productive stage, samples
must be taken from day to day as the
work progresses in order to keep in
formed of the grade of the material
being extracted to distinguish between
ore and waste rock. These samples
also provide a means of keeping a
check on the original estimates of the