ROCKS FROM NORTHERN AND CENTRAL CHINA. 37 
The quartz appears in fresh interlocking crystals, which are but little 
strained, and evidently are the result of the recrystallization of the original 
quartz. 
The striated feldspars are subordinate to orthoclase and have a com- 
position ranging from albite to oligoclase. The majority of the feldspars 
of both kinds are thickly set with inclusions which are the products of 
weathering. Kaolin and muscovite are the commonest of these products, 
but zoisite and epidote are scattered rather abundantly through the feld- 
spars as if the latter had contributed largely to the formation of them. 
Associated with interlocking grains of quartz there are also small fresh 
crystals of orthoclase and microcline, which have doubtless developed 
from the recrystallization of altered feldspars. 
The hornblende is bluish-green, varying in its pleochroism to pale 
yellowish-green. The crystals are all small and irregular, and are segre- 
gated to some extent in parallel bands in company with epidote. Most 
of them have been extensively altered into epidote, zoisite, and quartz. 
The brown mica is decidedly rare and occurs as irregular scales. The 
color is much too light for biotite, the feeble pleochroism ranging from 
colorless to pale russet-brown. It is not improbable that we have here 
the lithia mica, lithionite. 
The minerals now visible are probably all secondary in origin. Most 
of the quartz seems to have been rearranged in bands, and the parallelism 
among the hornblendes indicates that they are the results of metamorphic 
processes acting upon still older ferro-magnesian minerals. The subsequent 
change of the greater part of the hornblende into epidote, etc., gives the 
rock its present specific character. 
RocKks OF IGNEOUS ORIGIN. 
GRANITES. 
The T’ai-shan complex includes several varieties of granites. In 
the Ch’ang-hia district a reddish rock is prevalent, but in the T’ai-shan 
itself several different granites are associated. Some of them are found 
intruded into the gneisses and hornblende schists, and it is highly probable 
that they are all younger than those more severely metamorphosed rocks. 
Red gneissoid granite, No. 20.—The red granites are intrusive in the 
more ancient gray gneisses and hornblende schists of the T’ai-shan complex. 
In volume they form a large proportion of the Pre-Cambrian system and 
they are exposed extensively in many places. Specimen No. 20, collected 
near the head of the ravine about 2 miles, 3 kilometers, due west of the 
village of Ch’ang-hia. 
A light reddish-brown granite in which gneissic banding is scarcely 
discernible. The texture of the mass is rather fine. 
