The record-union., 1899-08-27


some cases both tunnels and shafts are
made on the same mine. Where a
tunnel is possible, the water drains off
itself, but in shafts the water must be
pumped or hoisted out in bailing tanks
AT the bottom of the shaft is a sump,
or continuation of the shaft. where the
water collects, and from which it is
pumped. In breaking down the rock
in running the drifts, ETC., holes have
to be drilled and powder used for blast
ing. These lodges are of an average
width of two to three feet, and extend
downward to an indefinite depth.
Sometimes they are thirty, forty or
fifty feet wide and sometimes only a
few inches. Generally speaking, the
wide ones are poorer in gold, on the
average, than the small ones; still the
very wide ones of low grade are pre-
ferred to the small but richer ones by
companies which invest in these prop
critics.
The large veins of medium or low
grade ore are supposed to be more last
ing than the small ones, and pay very
handsomely when extensive crushing
mills are provided. In all these mines
SOIIlS pOI dI6 pOOI anu OLuGIS
but there is no way of telling anything
about this in advance, unless one hap
pens to be like the man who was sure
that there was money in a certain mine
because he had put in $4,000 and
never got it out When men tell about
quartz from these mines running from
$500 to $1,000 per ton, it can be put
down as 'bosh,' or in that case there
is very little of the rock Pockets" or
small punches of ore, as rich as that
are sometimes found in a ledge, but
they are very scarce and are often sue
ceeded by barren rock, which may con-
tinue a long time before another pocket
is found.
When the ore is raised to the surface
from the mine, it is dumped in bins or
hoppers above the mill, from which it
falls by gravity into large, steam
driven rock breakers, which crush it
into small pieces, and thence it slides.
again by gravity, into what are called
ore-feeders. One of these is placed in
behind each battery of five stamps of
the mill, and is so arranged that at
each drop of stamp small quantity
of ore is fed under the stamps. The
amount to be fed may be regulated ac-
cording to the character of the ore.
The stamps, which weigh from 900
to 1000 pounds each and drop ninety
to 100 times each per minute, are ar
ranged in groups of five, each five hav-
ing a mortar of their own. In this are
five steel dies on which the shoes of the
stamps drop, the ore being crushed be-
~ i;
in which the stamps drop on the ore,
quicksilver is placed so as to catch the
gold as it is freed from the rock. Water
passes through the mortar continually
and washes the ore, as it is crushed,
through fine screens on to inclined
aprons or small sluices placed in front
of each battery. These aprons are
covered with sheets of silver plated
copper on which amalgam or quicksil-
yer is placed, so as to catch any gold
which escapes from the mortarS with
the finely crushed ore. These aprons
are scraped periodically to remove the
amalgam and gold. The amalgam-
which is gold and quicksilver mixed
from the mortars and from these plates
is placed in buckskin bag. and the
amalgam remaining being then retort-
ed. The heat in the retort evaporates
the quicksilver, which is saved by be-
ing again condensed, and the gold is
left in the retort. This is then melted
into bars, sent to the Mint and turned
into coin, and we all fight in our vari-
Gus ways to get hold Of as much Of it
as we can.
In addition to the free gold-that is,
in a pure native state-most of the ore
in these ledges carries sulphurets 0r
pyrites Of iron, also containing gold,
but in such condition that it will not
amalgamate with the quicksilver The
crushed ore, therefore, after going
through the batteries and over the
aprons as described, passes on to con-
centrators on the floor below These
consist Of inclined endless rubber belts,
which are revolved and have also a
shaking motion. They are so arranged
and operated that the light tailings or
worthless material pass away, while
they collect and concentrate the heavy
sulphurets and any stray gold or ANAL
gam which may have passed through
the mortars. A concentrator is used
for each five-stamp battery The sui
phurets thus collected are roasted in a
furnace to drive off the sulphur, and
are then SO treated by the chlorination
process that the gold is first dissolved
and then precipitated from the solu-
ton. Only few mills have a chlorina-
ton plant of their own, most of the
miners selling their sulphurets to the
C,1oa1fiYo works nf ma "
contain only from / to 3 per cent. OF
sulphurets, and these are often worth
from hundred to thousand dollars
a ton, but it takes time and work TO
get ton of them. The usual average
is from 1 to ~ per cent. of sulphurets,
worth from S75 to $50 per ton.
In some mines there is little or no
free gold, but the rock has to be
crushed and concentrated to obtain the
sulphurets which carry the gold values.
After passing all these appliances the
pulp, as the crushed ore is called, still
has some value, and is led through
sluices to canvas plant. Broad sheets
Of ordinary canvas are spread smooth
ly on slightly inclined surfaces, and
over these the tailings pass, carried by
the water, and clear water is added.
The little fibers of the canvas catch
very fine gold and rich "slimes" which
may have escaped the other appliances.
At some mines the cyanide process is
made use of to save gold from ores
which it is difficult to treat by the or
dinary milling process, and cyaniding
is also done with tailings which still
contain some gold. BY this process the
finely crushed ore is placed in vats
and treated with a weak solution of
oxapida of p0ta SSiI1rn bv which tho