368 RESEARCH IN CHINA. 
Dark hornblende gneiss, No. 28.—A more basic phase of the ancient 
gneisses than either Nos. 29 or 30. The rock is frequently schistose and 
grades off into hornblende schists such as No. 27. Specimen collected at 
an elevation of 4,300 feet, 1,300 meters, near the granite stairway up the 
T’ai-shan. ‘This is a dark, greenish-gray, indistinctly banded rock, the most 
prominent component of which is a blackish hornblende disposed not only 
in thin layers but in small lenticular knots parallel to the banding. 
The rock consists of feldspar, hornblende, and quartz, with lesser 
amounts of biotite, titanite, and pyrite. Hematite, epidote, and zoisite 
are present as alteration products. Judging from its composition the rock 
was originally a moderately basic igneous rock, but its constituents have 
evidently been completely rearranged, old compounds having been broken 
up and new ones formed. The minerals now present are probably all 
secondary developments or even later alterations of them. 
The quartz, albite, and orthoclase appear in medium-sized allotrio- 
morphic grains. In our specimen the feldspars are considerably altered 
to saussurite and micas. The light-green hornblendes, which are abundant 
in clusters or in scattered irregular crystals, have probably been constructed 
in large measure out of the original amphibole or pyroxene. It is rare 
to find these hornblendes in well-shaped crystals; they are usually closely 
packed and mutually interlaced in flat lens-shaped groups. Although 
subsequent decomposition of the hornblendes has not progressed very far, 
it has in some cases produced aggregates of epidote, hematite, and quartz. 
The subordinate amount of biotite present seems also to be a later develop- 
ment of the hornblende. It invades the latter along edges and often grades 
into the hornblende without any distinct boundary. This relation can be 
more clearly discerned in No. 27. 
A few grains of pyrite and magnetite are probably primary crystals. 
The former are generally surrounded by partial pseudomorphs of hematite, 
and other crystals of this iron oxide may also have been derived from the 
alteration of the pyrite. 
Biotitic hornblende schist, No. 27.—Apparently a basic phase of the 
hornblende gneisses just described. Specimen taken near No. 30 at 4,200 
feet, 1,260 meters, elevation on the south slope of the T’ai-shan. 
This rock is, in most respects, similar to the last described (No. 28), 
but in this case the schistosity is well developed. The cleavage faces 
exhibit not only the dark hornblendes but also a considerable amount 
of brown mica. The hornblendes and micas lie interlaced in layers which 
have a very marked parallelism. From the fact that the biotites penetrate 
and feather into the hornblendes it is evident that they are later and have 
been derived in part at least from the latter. 
