ROCKS FROM NORTHERN AND CENTRAL CHINA. 455 
This slide shows admirably the very different behavior of quartz and 
dolomite under conditions of strong compression. ‘The former is broken, 
ground up, and stretched out in bands; the other adjusts itself to the new 
conditions by merely recrystallizing in the form of a homogeneous aggregate. 
Black crystalline limestone, No. 1134.—This coaly limestone is asso- 
ciated with thin layers of impure black slate and dark limestone, along 
the canyon of the Han river opposite Shi-ts’tian-hién. 
Specimen from the right bank of the river, 1 mile, 1.6 kilometers, 
below the city. 
This is a coal-black finely crystalline limestone in which the lines of 
stratification are bent and contorted. The body of the rock is composed 
of interlaced crystals of calcite, arranged after the fashion of marble. A 
black graphitic substance occurs as specks included in the crystals and also 
in much greater amount in the form of streaks and seams; as the crystals 
formed they evidently excluded most of the graphite and pushed it aside. 
In addition there are grains of magnetite and quartz and small flakes of 
colorless mica; all of these are scattered indiscriminately through the rock, 
but the mica flakes lie with their axes parallel to the minute shear-zones 
which traverse the slide. Here and there the rock has been torn apart in 
the process of folding, and the fissures thus formed are now filled with 
vein quartz. 
The original components of this limestone have entirely recrystallized 
under conditions of dynamic metamorphism and have formed crystals of 
calcite, secondary quartz, mica, etc. 
Gray schistose limestone, No. 119.—This is from one of the limestone 
layers which are interbedded with mica schists, near Liang-ho. It is 
therefore closely related to Nos. 116 and 117. Specimen collected 3 miles, 
5 kilometers, southeast of Liang-ho. 
This rock is a dark-gray fine-grained limestone, banded with white 
laminz of quartz. Much of the mass is distinctly foliated and the surfaces 
of these folie carry minute flakes of mica, which impart a silvery sheen. 
The dark bands consist of interlocking calcite crystals, the majority of 
which are arranged with their longer axes nearly parallel. This schistose 
structure is emphasized by streaks of graphite, which coincide with it in 
trend. Pyrite and bits of graphite are scattered indiscriminately through 
the rock, while little scales of muscovite lie with their axes parallel to the 
general banding. The darker lamine are relatively free from quartz, but 
the white layers are composed almost entirely of that mineral in the form 
of a clear mosaic. The quartz shows little, if any, evidence of deformation, 
and it appears to have been deposited after the rock had passed through 
its severest distortion. 
