194 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
and roscoelite. Small pentagonal crystals of pyrite, as well as sphalerite, develop 
throughout the rock also; strings of these pyrite crystals joined by a thin sheet of 
quartz in some places penetrating the orthoclase. Light-colored sphalerite, inti¬ 
mately mixed with galena, occurs replacing orthoclase in ore from the Ajax mine. 
Small replacement veinlets as well as filled veinlets of adularia, quartz, and fluorite 
penetrate the rock and abundant irregular cavities of dissolution are coated with the 
same mineral associated with calaverite in well-crystallized form. 
The secondary adularia is often deposited in optical continuity about the 
remains of original feldspars. Sericite occurs in shreds in the orthoclase, but forms 
no important part of the rock. When granular quartz is developed it often possesses 
the optical “flamboyant” structure characteristic of Cripple Creek vein quartz. 
Apatite remains unaltered. Particularly large masses of granite ore were mined at 
the Ajax mine and two specimens of closely contiguous altered and unaltered granite 
from this mine were analyzed. 
Specimen 345 C. C., the analysis of which is shown under A in the table below, is 
a syenitic modification of the normal granite. It contains in the order of abundance, 
microcline, oligoclase, quartz, biotite, magnetite, apatite, and zircon. The oligoclase 
shows slight sericitization. The biotite is fresh. 
Specimen 344 C. C. (analysis B), taken at a distance of 1 foot from 345, shows 
much of the original microcline and quartz, although newly formed adularia is also 
abundantly present. Pyrite is disseminated throughout the rock, but also forms by 
replacement of original magnetite: The oligoclase is partly sericitized, and the 
biotite is transformed into aggregates of pyrite, fluorite, adularia, and a yellowish- 
green mica, which, without much doubt, is roscoelite. A small quantity of calcite or 
an allied carbonate appears as nests in the microcline. 
Analyses of fresh and altered granitic rock. 
[Analyst, W. F. Hillebrand.] 
A. 
B. 
Si0 2 . 
. 66.20 
59.58 
S0 3 ... 
AljOs. 
. 14.33 
16.00 
Cl. 
. 2.09 
.30 
F. 
FeO. 
. 1.93 
.65 
MgO. 
. .89 
.03 
MnO. 
CaO. 
. 1.39 
2.03 
BaO. 
. 2.58 
.98 
SrO. 
k 2 o. 
. 7.31 ' 
11.93 
Li 2 0. 
h 2 o-. 
. ,4S 
.32 
V 2 0 3 . 
H 2 0+. 
. .83 
.81 
MoOs.. 
Ti0 2 . 
. .65 
.75 
ZrO. 
.02 | 
(?) 
Less O. 
co 2 ... 
. .36 
.26 
P 2 Oo. 
. .25 
.32 
a 1.42 CaF. 
A (345 C. C.). Ajax mine, level 6. 
B (344 C. C.). Ajax mine, level 6, 1 foot from 345. 
6 2.55 S. 
A. 
None. 
Trace. 
(?) 
.12 
.13 
.18 
Trace. 
Trace. 
99.74 
B. 
None. 
(?) 
a. 69 
6 4.78 
Trace. 
.11 
.01 
Trace. 
.39 
.01 
99.95 
.29 
99.66 
