AIO RESEARCH IN CHINA. 
which the sedimentary rock has been changed to a greenish color. At 
the immediate contact the sandstone has been completely cemented into a 
dense flinty rock, but this is only a fraction of an inch in thickness. Along 
this contact subsequent faulting is indicated by the prominent development 
of slickensides upon this quartzitic layer. 
The red sandstone (represented by No. 37, which was collected at a 
distance of 10 feet, 3 meters, from the intrusion) is in reality a fine-grained 
arkose. It is composed of quartz and abundant feldspars together with 
grains of magnetite and occasionally other minerals. The cementing 
materials between the grains are earthy red hematite with calcite and a 
little quartz. 
In the altered zone the sandstone has been changed to a dull olive- 
green color (No. 36, collected 3 feet, 1 meter, from the dike). The thin 
section shows that the only notable change which has taken place is in 
the cement. The slide discloses no newly developed minerals nor any 
alterations of the sand-grains themselves. Even the calcite appears to 
have remained unaltered. The earthy red hematite, however, which is 
so characteristic of the red sandstone is in this specimen represented by 
an amorphous material of dull greenish color. While it is not possible to 
determine microscopically just what this pigment is composed of, it is 
probable that it has been produced by the reduction of ferric components 
to the ferrous state. 
In the only observed exposure of this rock it is so extensively decayed 
that it is difficult to obtain even a small and irregular specimen. As it 
appears at the surface the mass of the rock is bright green and there 
is usually a distinct spheroidal parting. Most of the rock can be dug like 
soil, but by removing the outer portions of one of the spheroids it is usually 
possible to obtain a small core or nucleus which is firm and coherent. 
This nuclear material has a dark brownish-gray color and is aphanitic. 
In the field it was mistaken for a badly weathered pitchstone. 
An examination of the thin section shows that the rock was formerly 
composed almost entirely of olivine with a little pyroxene and iron ores. 
It was therefore very close to the dunites in composition. 
The olivine in our specimen is wholly altered to fibrous gray serpentine 
and iron ores. The cracks and boundaries between the crystals are partly 
occupied by a greenish decomposition product which is probably also ser- 
pentine. The centers of many of the crystals are obscured by opaque 
brownish material, the nature of which is not recognized. 
The section shows only a few irregular areas which are occupied by 
augite. It occurs in irregular masses inclosing crystals of olivine and 
controlled by the latter in all its boundaries. Along the cleavage lines 
