ORIGIN OF FOLIATED CRYSTALLINE ROCKS 305 
ANALYSES BY J. H. WARNER 
Quartzite Sericite Schist 
SiO sae acccisnhaeee ae 86.60 58.61 
AN AO), {era HO? Asia ee 7.60 2278 
ISO), BSOne gadis gue Be 9.73 
KG Osetra ee is ale oe 1.102 2.85 
Nias Opis Roles seve 508 1.18 
Loss by ignition...... mele) 2.92 
A test by panning made on material from a pegmatite dike 
in the quartzite some miles from the locality in which the schistose 
bands were developed did not reveal the presence of either zircon 
or ilmenite. 
Conclusions.—The evidence showing that the bands of sericite 
schist are not altered argillaceous bands which may have under- 
gone little change in composition during metamorphism may be 
summarized as follows: 
a) Field evidence shows that the schistose bands are sometimes 
developed directly across the bedding. In many cases where they 
might be considered to have developed parallel to the bedding the 
schistose zones are lens shaped and cannot be traced to any argil- 
laceous layer in the quartzite. 
b) Zircon is usually formed only in igneous melts. During 
sedimentation the zircon grains become concentrated in the arena- 
ceous beds and they are almost absent from argillaceous deposits. 
In the sericite schist, which has roughly the composition of an 
argillaceous sediment, zircon is present in amounts large even for 
arenaceous beds. It is decidedly in greater abundance in the 
sericite schist than in the quartzite. 
c) Ilmenite is generally considered to form only under conditions 
of high temperature and it is usually associated with igneous rocks. 
There is no evidence that it has been formed secondarily in either 
the quartzite or the sericite schist. It is a heavy mineral and like 
zircon would be concentrated in the arenaceous beds during sedi- 
mentation, yet it is decidedly more abundant in the schist than in 
the quartzite. 
The following evidences seem to indicate that the difference in 
