404 RESEARCH IN CHINA. 
formations in the vicinity is obscured. ‘The hills are almost entirely bare. 
The rock is broken by three systems of joints into quadratic blocks whose 
dimensions are from 4 to 8 feet, 1.2 to 2.4 meters, on the side. The weath- 
ering of the gabbro produces a black sand which forms waste slopes at the 
bases of the hills. 
Specimen obtained at the base of a conical hill, about 60 feet, 18 
meters, high, which is situated 3.7 miles, 5.9 kilometers, WNW. of the 
outer wall of Tsi-nan-fu. 
A dull blackish-brown rock of medium granitic texture. From an 
inspection of the hand-specimen the nature of the darker minerals can 
only be guessed at, and the lighter ones appear to be entirely feldspars. 
The olivine, which is revealed by the microscope, is difficult to distinguish 
with the unaided eye. In the thin section the constituents are seen to be 
plagioclase, augite, hypersthene, olivine, and a little biotite and magnetite. 
The first mineral to crystallize was olivine; it is found included in 
both of the pyroxenes and in the feldspars and is unexpectedly fresh. 
Along the edges and cleavage cracks, pale-greenish serpentine has begun 
to develop, and in some cases a little magnetite dust has separated out 
during the process. Where the olivine is in contact with the feldspars, 
one frequently sees bushy growths of minute colorless fibers which are 
probably tremolite or some other amphibole. Reaction rims of this char- 
acter have been described by Térnebohm,* Williams,} and others. 
Of the two pyroxenes hypersthene is less abundant and usually occurs 
in smaller bodies. It exhibits the customary pleochroism varying from 
pale-green to salmon-pink. It is not only unaltered, but is relatively free 
from inclusions. 
The most common of the darker components of the rock is a pale- 
greenish augite. This contains numerous small inclusions of the olivine, 
biotite, magnetite, and other minerals. Certain inclusions which appear 
clear gray between crossed nicols are probably feldspars; in a few cases 
faint twinning bands can be seen. A mineral supposed to be rutile occurs 
in minute short needles, all of which lie with their axes parallel to the 
principal cleavage of the pyroxene. On account of the great difference 
between the two kinds of pyroxene in regard to their content of these 
inclusions, they can readily be distinguished from each other by this means 
alone. 
The large clear prisms of feldspar crystallized later than the other 
components and hence are bounded by irregular lines. They show but 
little sign of decay and have very few inclusions. The extinction angles 

* Neues Jahrbuch fiir Mineralogie, Geologie und Paleontologie, 1877, p. 383. 
+ U.S. Geological Survey, Bull. 28, p. 25. 
