360 RESEARCH IN CHINA. 
The schistose arrangement of the micaceous minerals is prominent. 
The iron ore is hematite, now largely altered to limonite, but the perfect 
rhombic forms of the bodies indicate that they are pseudomorphs after 
siderite which has been subjected to weathering. These rhombs of quon- 
dam siderite lie with their longer axes parallel to the schistose structure 
and usually lie in ‘“‘eye-spots’”’ formed by the divergence of the minute 
shear-zones as they encounter the rhombic crystals. The matrix is least 
disturbed in the angles of these ‘“‘augen’’ and most sheared and sliced 
along their flanks where stresses have been most intense. 
The original rock appears to have been a ferruginous clay. The rhombs 
of siderite may represent initial deposition, but probably they grew in 
the clay by segregation of the iron-carbonate content. Under conditions 
of heavy pressure in a deeper zone the mass was somewhat deformed. 
Schistosity began to develop, but the process did not progress far enough 
to distort the siderite. Subsequently hematite replaced the siderite and 
it is now in turn weathered and largely altered to the hydrous oxide. 
SINIAN SYSTEM. 
Rocks OF SEDIMENTARY ORIGIN. 
PSEPHITES. 
Quartzite conglomerate, No. 62.—A moderately coarse conglomerate 
from the Yung-ning formation (Lower Cambrian?) 2 miles, 3 kilometers, 
north of Fu-chéu. It is not known to be a basal conglomerate. 
The pebbles are well-rounded pieces of resistant rocks, such as vein- 
quartz, gray, black, and banded chert, and brown iron ore. They are 
firmly embedded in a coarse gray sandstone, the grains of which are 
cemented with quartz. 
PSAMMITES. 
Ferruginous arkose, No. 65.—A characteristic example of the harder 
strata in the Yung-ning formation. Specimen taken 3 miles, 5 kilometers, 
northeast of Ch’au-kia-tién, between Fu-chéu and Siung-yué-ch’éng. 
The rock is a hard, coarse-grained arkose or grit of red-brown color. 
The red hue is imparted by abundant red feldspars. 
Quartz and feldspar together constitute the largest part of the mass. 
In addition there are abundant grains of magnetite and hematite. The 
grains are irregular or subangular, but do not show the rounded forms 
of well-worn sand. ‘The cement, which binds the grains into a hard rock, 
is argillaceous; it consists of the debris of decayed feldspars and com- 
minuted quartz. Oxides of iron stain the cement yellow and brown in 
certain areas, and chlorite locally imparts a green tinge. Evidence of 
deformation is very slight, 
