Custer weekly chronicle. [volume] (Custer City, S.D.) 1890-1931, 1902-06-07
Secretary of the Interior
Free Milling Ore.

Every once in a while we see men.
toned in the papers published in the
northern Hills, notes on different mines
around Custer designating them as pro-
ducers of free rnilling ore. This means
that the ore is amenable to the process
of stamping and amalgamation of the
gold with quicksilver. This is not true
Of any mine as yet discoyered in the
southern Hills, except the "Holy Terror"
at keystone, and it is not strictly true
even of the Holy Terror. 1t is true that
we have many mines which is free mill
ing at the surface and that fact has been
the bane of our camp. There are, or
were until recently, II stamp mills with
in a radius Of 10 miles of Custer City.
These were all erected to treat the ores
of the different mines by the free milling
process, and we grieye to state that al
though many are rich gold mines they
have every one been failures. For l5
years We haye preached to our people
that there were no free milling mines in
the southern Black Hills, and We have
prayed to them to diyest themselyes Of
that eronious notion. Still every once
ia while there comes stranger into
our camp, who is attracted to the mines
which show rich prospect in the pan,
and he excited by the delusiye phan-
tom, invests his money in the belief tnat
it is free milling mine, and invariably
scores another failure. Our miners and
prospectors have learned that the ores
do not retain their free milling quality
as the veins descend into the earth, ex.
cept in very rare instances when it is
found in narrow seams, but not in suffi-
cient quantity to be considered in COM
parison to the grand aggregate of the
precious metal that is in the rock. We
are tired Of seeing this folly repeated
year after year in this district, and in 80
far as we have power to prevent there
will be an end to it. If called upon to
give reason why the ores are often
free milling at the surface, and base and
refractory below. we would explain it in
this way. The mineral found in the rock
was first in solution which became
stronger as it perculated through the
rock, desolving and absorbing whatever
mineral it found in its way. When at
last it reached the creyice, which is now
changed into a vein of ore, by the crys.
talization of these minerals from their
solution. The mineral crystalizes in &C.
cordance with its chemical affinity, and
its constituents are just what was pre-
yiously in the water. There are so
many varieties in these combinations
that it would be difficult to enumerate
them and in the southern Hills we seem
to have them all. But the most COM
mon minerals with which the gold COM
bines in the southern Hills mines is as
follows. Iron, sulphur, bismuth, tellu-
rum, tungstic acid platinum, copper,
silver, antimony, arsetic and lead. These
minerals are deposited in the vein in the
manner described, mingled with q
matrix of silica, lime, etc., as the case
may be. The vein becomes eroded or
worn down, and the mineral is exposed
to the rays Of the sun and the action Of
the oxygen in the atmosphere, until the
base metals become disintegrated and
are again taken up in solution, and flow
downward deeper into the vein, where
they form new combinations and again
crystalize. This secondary teaching is
what produces the rich spots, streaks,
and what is termed pay shoots" in the
vein. But the gold except in some of its
rare combinations will not leach as read.
lily as the base ores, and is therefore left
at or near the surface where it is found
by the prospector, and may be obtained
by the morter and pan, or amalgamated
with quicksilver. Our ores are amenable
to the various processes of chlorination,
cyanide or bromide, and may be smell
ed after preliminary roasting, but not
without. AS far as our experience goes
after 16 years experimenting and testing,
we are prepared to testify, and we an
nounce, and wish it distinctly under
stood that our ores are not free milling.
q. w. ROBBINS.
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