The Meeker herald., 1894-04-07
CRIPPLE CREEK ORES.
Explauation of the Manner In Which
Gold Occurs In Them.


condensation of paper read before
the Colorado Scientific Society at its
last meeting by Dr. Richard Pearce:
The Cripple Creek ore has the APP
pearance of rhyoite, with similar
characteristics to the silver deposits
at Silver Cliff, Colorado. At the lat
ter place the joints and fractures OF
the rock were filled with psilomelanc,
carrying cerargyrite in sufficient guam
titles to make it silver ore; at Grip
pie Creek the silver is replaced by gold.
The material on which the investiga'
tons were made came from the Gar
field Grouse mine. 1t consisted OF
Jumps of rhyolite, one or two OF which
were coated with quartz crystals, &C
companied by clay and psilomelane, the
latter occurring in small rounded or
botryoidal concretions characteristic
of this mineral The rest of the sam
pie, forming about % per cent. of the
whole, was soft, clayey material, in
closing humps of soft rhyolite, which
could easily be rubbed down by the
hand to an unctious clayey mass.
The free gold obtained by vanning,
after separation of the loose material,
from the rest, was of peculiar,
brownish color. brittle, crystalline,
presenting n striking analogy to the
habits of sylvanite, from which it was
inferred that they might be pseudo
morphs after that mineral. This con-
clusion was further strengthened when
it was found that in the soft, clayey
portion Of the ore tellurium was found
| in an oxidized form.
On samples from the prince AL
bert and independence" containing
respectively OF. and . OF. gold per
ton it was found that the Prince AL
bert carried o IA per cent. of tellurium
in the oxydized form and the Indie
pendence OH per cent. In support OF
the theory that the gold was derived
from sylvauite, a comparison Is drawn
between the ratio of gold to silver in
their telluride minerals and that which
exists in the Cripple Greek ores; Crys-
tallinc sylvanitc, ratio An to Ag 2I;ll;
massive calaverite, ratio 1913; krcn-
neritc. ratio 35:5. The results of
sampling great many tons OF Cripple
Creek ore show that the relation OF
the gold to the silver more nearly ap-
proachcs the ratio which exists in syl-
vanite than in calaveritc or krenncr-
lite.
The following figures showing the
relative proportions Of gold and tellu-
rum in three samples OF the oxy-
died material, will. however, prove
the existence of large o-cccss of tcllu-
rum over the amour. required to have
originally formed sylvanite;
Sylvanitc Au to Az - .45i; Prince
Albert No. I, ratio ] 3 1913; Indc. ID
encc No. |, ratio . $40; Prince Al
bert No. >. ratio .4.3S5. This excess
of tcllurium can only be accounted for
either by supposing that other tcllu-
rum minerals were present (probably
native tcllurium) or that portion of
the gold originally combined with it
had been removed.
This latter theory seems not at all
an unlikely one. The presence of bin
oxide Of manganese, together with solu-
tons containing alkaline chlordcs, and
sulphuric acid derived from the de-
composition OF the pyrite, would effect
the removal of finely divided and pre-
cipitated gold by means of the chic
ride generated.
Specimens coming from greater
depths exhibited all the stages of
transition from the mineral syvanite to
pure gold, with tellurium in an oxid-
lied state. This free gold appears in a
remarkable condition. 1t is very much
like gold that has been precipitatcd
and allowed to dry. being very soft
and yielding readily to pressure with
the knife. Associated with the gold
is soft yellow inerustation, contain
ing strong evidences of the presence
of tcllurium in an oxidized form. In
several pieces the free gold again
showed distinctly the habits of syl-
vanitc, of which mineral there weN
pscudomorphic impressions in mat
rix Of granular fuoride, the gaaguc be-
ing metamorphoscd rhyoitc. 1t may
be noted that pscudomorphs of gold,
after sylvanite, were long ago observed
by the writer in specimen from one
of the Boulder mines
The metamorphosed rhyolitc COM
ing from below the zone of oxidation
probably owes its peculiar grcenish
color to the presence of iron in fer
rous condition. In the Garfield Grouse
mine the ore is mainly the white rock,
which in itself is quite barren, or
nearly so, but the joints of which are
filed with high grade auriferous mate
rial. Some idea of the richness of the
latter may be had when it is stated
that the lot of ore in bulk which furn-
ishcd the samples on which the fore
going experiments were made carried
20 OF. of gold per ton. The greenish
metamorphosed rock from the Ana
conda in which the mineral sylvanitc
was observed assayed ~ ounces of gold
per ton.
As to the origin of the Cripple Creek
deposits it may be reasonably inferred
that they were caused by solutions
brought up from below through the
joints or lines of least resistance, the
L unld haiHn nj 4huA