446 RESEARCH IN CHINA. 
three or four very small garnets, none of which are noticeable in the hand- 
specimen. 
This specimen has the composition of a fine-grained graywacke which 
has been subjected to considerable metamorphism in the deep-seated zone. 
The granulation of the large sand-grains is obvious and it must be supposed 
that much of the ground-mass has suffered in the same process. It is also 
evident, however, that the present constitution of the rock is due principally 
to the recrystallization of the comminuted material; during this process the 
fresh feldspars and quartz, the parallel micas, and other secondary minerals 
were developed. 
PELITES. 
Pyritic black slate, No. 138.—A prominent member in the anthracite 
coal-measures (Wu-shan) on the Nan-kiang in southern Shen-si. ‘The series 
is exposed for several miles south of the village of Ku-niu-tu, and the pres- 
ent specimen was collected 2 miles, 3 kilometers, south of that village. 
This is a hard, dense, bluish-black rock in which slaty cleavage is 
poorly developed. Although it breaks at rather distant intervals along 
parallel planes, it fractures much more often conchoidally. 
In the thin section this black argillite is seen to be exceedingly fine- 
grained. Quartz and dark carbonaceous materials compose most of the 
mass, with a very few small sand-grains scattered at random. ‘There seems 
to be no definite orientation among the minute flakes of kaolin, and there 
is no evidence of noteworthy progress in the recrystallization of the original 
shale. In addition to the minute grains of pyrite visible on the surface 
there are obscure blotches of a grayish substance which is not recognized. 
Throughout the slide many microscopic shear-zones are seen; some 
of them are short and evidently only incipient, while others traverse the 
entire slide. ‘These shear-zones are apparently the only visible evidence of 
mechanical deformation. ‘Their general trend is not parallel to the rather 
faint lines which are indicative of slaty cleavage. 
Black stliceous argillite, No. 133.—This is the coal-bearing argillite 
which is exposed 2 miles, 3 kilometers, north of Ts6ng-kia-pa. It is asso- 
ciated in that locality with a metamorphosed conglomerate (No. 134). 
A dense, aphanitic, coal-black argillite, which tends to fracture con- 
choidally rather than with true slaty cleavage. As seen in the thin section, 
the rock consists of uniformly and very minutely crystalline quartz and 
finely divided graphitic matter. The black pigment is not evenly dis- 
tributed, but forms an obscure complex of wavy bands which give the 
slide a mottled appearance. In this slide there are no porphyritic grains 
nor any micaceous constituents worth mentioning. 
