646 LEWIS G. WESTGATE 
Both orthoclase and microcline frequently show a fine microper- 
thitic intergrowth, with a second feldspar. In a larger number 
of sections some orthoclase and plagioclase grains show a grano- 
phyric intergrowth, with a second mineral, probably quartz, 
which takes the form of narrow irregular, curving or angular 
inclusions, converging toward the center of the feldspar grain. 
This granophyric intergrowth is absent from the probably sedi- 
mentary gneisses to the south, and seems to be characteristic of 
those of igneous origin. Quartz occurs in irregular but some- 
what rounded interstitial grains, and is also common in drop- 
like inclusions in the feldspars, which occasionally approach a 
a dihexahedral shape. Titanite, in small, rounded, and lenticu- 
lar grains, is the most common accessory. A very little apatite 
and magnetite occur. In about one half of the sections there is 
evidence of a slight amount of crushing. In the section where 
this is best shown, some of the quartz grains have been elon- 
gated, broken into separate areas, and granulated about their 
border and along lines of fracture; and between the feldspar 
grains are lines of smaller grains, which seem to have come from 
the fracturing of the feldspar, Yet in this section considerable 
portions show no evidence of crushing, and in many slides no 
proof of crushing exists. 
2. Schlieren.— The biotite-gneiss, especially where it is more 
massive, often contains schlieren of darker color and finer grain, 
which have already been referred to and partly described in the 
discussion of the igneous origin of the granite-gneiss. Sections 
from these schlieren resemble closely the ordinary granite- 
gneiss. They are granitic in structure, but with a distinct folia- 
tion. Green hornblende is present, but is less abundant than 
the biotite. Orthoclase, plagioclase, and microcline occur in 
abundance in the order named. A few feldspar grains show the 
granophyric intergrowth already mentioned. Quartz and micro- 
perthite are absent. Titanite is acommon accessory. The pres- 
ence of hornblende and absence of quartz, while keeping the 
other essential structure and characters of the granite-gneiss, 
indicates that these darker patches are an integral part of the 
