ROCKS FROM NORTHERN AND CENTRAL CHINA. 429 
CARBONATE ROCKS. 
White marble, No. 96.—lwo members of white marble occur in the 
Shang-ho-miau portion of the T’ai-shan-ho section. The lower one is inter- 
bedded with garnet schists, while the upper bed is thicker and uninterrupted 
by schists. Our specimen came from the upper layers of the lower marble 
(Plate XVIII, stratum 23). 
A finely crystalline marble of gray-white color. Indistinct gray bands 
appear to mark the original bedding-planes. ‘The rock consists almost 
entirely of interlocking crystals of a carbonate, which is probably calcite. 
The only accessory minerals are a few flakes of muscovite which are scattered 
at random through the mass. 
According to the usual habit of such rocks, the original limestone did 
not become schistose when metamorphosed, but merely recrystallized into 
marble in which no evidence of strain or fracture may be seen. 
Banded impure marble, No. 100.—Banded impure marbles of gray, 
brown, and reddish colors, containing seams of chert, jasper, and hematite, 
occur just above the fault-plane upon which the Nan-t’ai series overrides 
the white marble syncline on the west side of the T’ai-shan-ho. ‘The marble 
is interbedded with layers of dark quartzite and slate (No. 101). ‘The 
present specimen, collected 0.5 miles, 0.8 kilometers, up the ravine which 
comes in from the north, may be considered fairly representative of the 
limestone portion of the true Nan-t’ai. 
The dark-gray and red portions of the rock are finely crystalline, but 
the wavy white bands are composed of coarser quartz and calcite. Little 
seams of steel-gray hematite occur in the quartzose layers. 
The internal composition of the rock is so complex that the term 
‘‘marble’’ is of doubtful appropriateness. The red bands are rich in hydro- 
hematite dust, but otherwise resemble the gray layers. The latter consist 
of a fine mosaic of quartz, calcite, and feldspars (both orthoclase and 
plagioclase). All are abundant, and they are intimately mingled as ina 
clastic rock. ‘The rounded forms of many of the strained quartzes and feld- 
spars strongly suggest that they are clastic grains, not yet recrystallized, 
embedded in a crystalline ground-mass of calcite. In certain bands the 
carbonate has been replaced by cherty silica as described by Van Hise* 
from the Lake Superior iron formations. 
The lighter bands are evidently in the nature of veins which have 
been formed by the deposition of quartz, calcite, and hematite from solu- 
tions. The pronounced strain-shadows and sliced crystals show that the 
veins themselves have been severely deformed. 

*U.S. Geol. Surv. Monograph xivu, A Treatise on Metamorphism, pp. 850-851. 
