A24 . RESEARCH IN CHINA. 
are all heavily strained, many of them sliced and considerably granu- 
lated locally, and shear-planes traverse the mass at frequent intervals. 
The longer grains show a rude parallel arrangement, as if they had been 
rotated into a common plane. Part of the granulated material derived 
from the sand-grains has been recrystallized in the form of fresh quartz 
and orthoclase crystals. The greater part of the rock still consists, how- 
ever, of unreduced, though distorted, sand-grains. 
Black magnetite quartzite, No. 9t.—The compass-needle is perturbed by 
this rock in the canyon of the T’ai-shan-ho about 4 miles, 6.5 kilometers, 
above Shi-tsui. The quartzite is interbedded with schists of the Shi-tsui 
series (Plate XVIII, stratum 19). 
The quartzite is black, with narrow gray bands parallel to the strati- 
fication planes. The texture is fine. Quartz and magnetite are the only 
abundant components, and the variations in the relative abundance of 
these two minerals in different layers impart the banded appearance of 
the exteriors. The quartz grains form an interlocking mosaic without 
cement, while the iron ore occurs in cubic and octagonal crystals of vari- 
able size interspersed or even occluded in the quartz (Plate LVI, Fig. E). 
These features indicate that the rock is a ferruginous quartzite which has 
entirely recrystallized without becoming schistose. ‘The conditions were 
probably those of mass-static anamorphism. 
Subsequent changes are evidenced by the occurrence of irregular 
fissures filled with tertiary magnetite, associated locally with chlorite and 
siderite. These last minerals are characteristic of the belt of cementation, 
and the very existence of the fractures shows that the rock had emerged 
from the anamorphic zone previous to the production of these veins. 
Micaceous graywacke, No. 84.—A phase of the schist-and-quartzite 
sequence in the lower part of the Shi-tsui series. Specimen collected near 
the top of a micaceous quartzite (Plate XVIII, stratum 4), 1.5 miles east 
of Shi-tsui. 
The rock is purplish-gray in color with much black mica in certain 
layers. All the crystals are minute, but the specimen is not strongly 
coherent and the feel is sandy. The compact mosaic of small grains 
consists of quartz and various alkali feldspars. No schistose structure 
appears in the slide. In darker bands shreds of biotite with green horn- 
blende and epidote are abundant. They exhibit no definite parallelism 
in their orientation. 
Although this rock is part of a sedimentary sequence its clastic struc- 
ture is no longer visible. The original constituents have recrystallized 
without the development of schistosity. Its composition suggests that 
it was formerly a fine-grained grit or pelite. 
