378 RESEARCH IN CHINA. 
RocKs OF SEDIMENTARY ORIGIN. 
DOLOMITES. 
Crystalline dolomite, No. 8.—A local phase of the basal layers of the 
Tsi-nan formation. Specimen collected in the cliff northeast of Ch’au- 
mi-tién village, Shan-tung. 
A pale-brown rock of even grain and fine saccharoidal texture. It 
feels sandy to the touch and presents numerous minute glistening faces 
which show that it is distinctly crystalline. 
The specimen is composed almost entirely of crystals of the mineral 
dolomite, which are more or less perfectly rhombic in outline. The charac- 
teristic cleavage is fairly prominent, but twinning bands do not appear 
in the slide. Upon testing the slide with logwood stain* we find that 
a small amount of calcite occurs in the interstices between the grains 
of dolomite. 
OoLITic LIMESTONES. 
No single feature of the lower Sinian limestones is more distinctive 
than the dark oolitic bodies which are characteristic of these rocks at 
certain horizons over a large area of northern China. Upon studying the 
specimens under the microscope we find that some are typical oolites, 
others show evidence of having been once oolitic, while others are prob- 
lematical. 
Red oolite, No. 14.—Typical oolites of red color occur in thin strata 
near the top of the Man-t’o (Lower Cambrian) formation. Our specimen 
was taken at this horizon in the summits southwest of Ch’ang-hia, Shan- 
tung. 
This specimen represents an oolitic limestone of the familiar type 
and is useful as a basis from which to proceed to the discussion of the 
stranger phases of Chinese oolites, which are so altered that their origin 
has been contested. The rock is a massive red-brown limestone composed 
largely of small spheroidal red bodies inclosed in a matrix of clear calcite. 
The matrix forms only a small part of the mass, however, and its color 
serves merely to impart to the rock a mottled appearance. 
The matrix is rather coarsely crystalline, contains no animal remains, 
and possesses no distinctive structure. The portions contiguous to the 
corpuscles are usually composed of long crystals arranged as a fringe 
along the circumference of the red body. ‘These facts suggest that the 
matrix has either been introduced in aqueous solutions or has crystallized 
in situ since the corpuscles were formed. 
* For this method of distinguishing calcite from dolomite see Lemberg, abstract in Mineralogical 
Magazine, vil p. 166, or Skeats, Bull. Mus. Comp. Zool. Harvard, Geol. Series, v1, No. 2 
