218 EDWARD B. MATHEWS 
prominence in the constitution of the Pikes Peak massif. This 
type is characterized by the relatively large size of its feldspar 
and quartz grains and its tendency to form conspicuous feldspar 
phenocrysts that often attain a diameter of several] inches. 
The fresh, unaltered granites of this type are coarse-grained 
aggregates of quartz, perthitic feldspars, and biotite with occa- 
Fic. 3.—Pikes Peak type of the granite. 
sional accessory hornblende or fluorite and microscopic apatite, 
zircon, titanite, magnetite, rutile, hematite, limonite, epidote, and 
allanite. 
The grain varies widely from extremely coarse where the 
feldspar phenocrysts are six inches long to the more normal 
granite in which the length of the feldspar grains is little more 
than a quarter of an inch. The usual diameter for the feldspar 
is about half an inch, and for the quartz, a quarter of an inch to 
an eighth of an inch. The biotite areas, although generally 
smaller than the quartz grains, are sometimes a half inch in 
width. (Fig. 3.) 
