50 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
In the imdulous extinction of the quartz, the contortion of the mica, and 
sometimes distinct cataclastic structure, together with a rude arrangement of the 
constituents in parallel position and in bands, there is additional evidence of defor¬ 
mation. 
OTHER VARIETIES. 
Reddish to dark-gray gneissic rocks, usually of finer grain than the type just 
described, occur as streaks and patches within the Cripple Creek granite, particu¬ 
larly near the contact with the Womack gneiss. 
Biotite is the prominent constituent, though feldspar is plentiful, particularly in 
the less foliated types. In some cases there seems to be a direct gradation into the 
Cripple Creek granite, suggesting that they have been derived from it through shear¬ 
ing; but their lithological similarity to the Womack gneiss makes it probable that 
they are masses of that rock which have been caught up in the granite at the time of 
intrusion. The microscope shows that they are practically identical, as to mineral 
composition, with the Womack gneiss, except that orthoclase has been largely 
changed to microcline by the crushing which has taken place. 
Another variety of gneiss is that derived by shearing of the Pikes Peak granite. 
As mentioned in the description of that rock (p. 43), deformation has in some places 
been sufficient to produce an augen gneiss or even a still more foliated rock. Gneissic 
facies of this kind exist in the neighborhood of the contact with the Cripple Creek 
granite in the southwestern part of the district, on Beacon Hill and near the Thomp¬ 
son mine. Still greater shearing has produced a rock which is with difficulty recog¬ 
nized as having been derived from the Pikes Peak granite. All the large feldspar 
crystals have been destroyed and biotite appears to have been formed under the 
metamorphosing conditions that obtained. The resulting rock is a dark, micaceous, 
decidedly foliated gneiss. It occurs in several places as narrow zones, and in the 
southeastern part of the district is frequently encountered in small, ill-defined areas. 
A mass on the southern slope of Calf Mountain can be roughly outlined and, as has 
been stated, has been mapped with the Womack gneiss. The rock in that locality 
bears considerable resemblance to the Womack variety, of which it may possibly be 
an included fragment in the Pikes Peak granite. If that be the case, the Pikes 
Peak granite is certainly of later age than the gneiss. But marginal gradations into 
fairly massive granite and the occurrence of narrow strips of similar rock along 
near-by shear zones make it probable that the gneiss has been formed directly from 
the Pikes Peak granite. 
Related to the foregoing, and probably representing even more intense meta- 
morphism, are the narrow, dike-like zones of dark-colored foliated rock—for exam¬ 
ple, the so-called “schist vein” encountered in the Ajax mine and the similar occur¬ 
rence in the cut on the Low Line of the electric railway near the point where it passes 
under the Florence and Cripple Creek Railroad west of Victor. These are made up of 
clear, untwinned feldspar, a few grains of quartz, abundant green biotite, and con¬ 
siderable actinolite, with small amounts of apatite, sphene, and magnetite. Recrys¬ 
tallization has doubtless occurred, but crushing is evident not withstanding. 
