ORIGIN OF FOLIATED CRYSTALLINE ROCKS 303 
work of the writer has been largely confined to the examination of 
the zircon and ilmenite contents of the rocks in order to obtain 
further evidence of chemical change during metamorphism. At 
the same time the rocks were studied in the field and under the 
microscope. 
Data.—The quartzite exposures are not continuous but afford 
excellent opportunities for study, especially as a quarry has been 
opened up in one of the largest outcrops. Though the rock has 
been strongly folded, its bedding can generally be determined by 
means of conglomeratic layers. The schistose bands, which are 
seldom over two inches in thickness, may in some cases lie parallel 
to the bedding but in others they distinctly cut it. 
The quartzite is of a dense crystalline type. It is predominately 
grayish in color, though vitreous and reddish phases also occur. 
Frequently specks of black iron oxide (ilmenite) and light-colored 
mica can be detected in the hand specimen. Under the microscope 
the fragmental texture can be recognized though the rock has 
suffered considerable granulation and recrystallization. Between 
the quartz grains are varying amounts of sericite and ilmenite with 
a few crystals of zircon. The sericite occurs in small flakes which 
are generally parallel to the borders of the quartz particles while 
the ilmenite is present in irregular grains. Sometimes the zircons 
are surrounded by quartz which seems, in some cases at least, to 
be of secondary origin. 
The sericite schist is a uniform, fine-grained micaceous rock, 
generally of a pale greenish-yellow color. Under the microscope 
it is seen to consist of the same minerals as the quartzite except 
that the quartz has largely been replaced by sericite. In some 
places, associated with the sericite bands, are small stringers of 
quartz. The sericite flakes occasionally bend around portions of 
the quartz veins, suggesting that at least part of the quartz was 
present during the formation of the sericite. 
The writer has separated the zircon and ilmenite grains from 
several specimens of the quartzite and schist by panning and the 
use of heavy solutions. It was found that the amount of ilmenite 
and zircon was in each case unusually large and that, apparently, 
both minerals were more abundant in the schist than in the quartz- 
