GRANTITIC ROCKS OF PIKES PEAK QUADRANGLE 219 
The texture of this type presents all grades of transition from 
that in which the feldspar is only slightly larger than the quartz 
to one in which the feldspar stands out in large, imperfectly 
formed porphyritic crystals." 
The areal distribution of the rocks showing such increase’ 
in the development of the feldspar is not clearly defined, although 
there is a faint suggestion of a concentric wrapping about the 
lower slopes of Pikes Peak. 
A mechanical separation shows the constituent minerals of 
the Pikes Peak type to be in the following proportions by weight: 
Quartz - - - - = Bail 
Microcline - - - - 53-3 
SBOE a s— - - - = 1x4 
Oligoclase - - - - 2.6 
100.00 
The ‘biotite’ includes all of the minerals with a greater 
specific gravity than 3.0. 
The quartz occurs in large irregular or oval, colorless or 
smoky grains distinctly outlined against the feldspar and biotite 
towards which it is usually xenomorphic. In one instance, a 
basal section of quartz presented three systems of cracks inter- 
secting at 60° representing an imperfect rhombohedral cleavage 
probably due to mechanical deformation. The extinction ranges 
from completely simultaneous to mottled or undulatory. 
The inclusions observed are arranged according to one of 
three ways. (1).The small and irregularly shaped inclusions 
occur either in long thin lines parallel to the rhombohedron, in 
broader unoriented zones, or irregularly massed in definite parts 
of the quartz individuals. (2) The small, somewhat rectangu- 
lar cavities are arranged in indistinct lines parallel to their longer 
directions but not related to the crystallographic directions of 
the quartz. (3) The fine, hair-like ‘‘ needles” have a linear 
arrangement and seem to occur when the other inclusions are 
*The coarse-grained granite in which the feldspar phenocrysts are large and 
generally well formed, is sometimes called the “‘ Raspberry Mountain granite,” from its 
conspicuous development on that mountain. 
