ROCKS FROM NORTHERN AND CENTRAL CHINA. 415 
appear to have developed in consequence of the metamorphism which pro- 
duced the banding. Hornblende, garnet, epidote, and titanite all occur in 
the same bands and always in small irregular grains rather than in well- 
formed crystals. Some of the material has obviously been sliced and it 
may be that most of the grains are merely fragments of larger and more 
regular crystals. 
Black amphibolite, No. 75.—Dark amphibolites and hornblende schists 
are frequently interlaminated with the gneisses near Féu-p’ing-hién. The 
present specimen was collected 2 miles, 3 kilometers, east of the city (in 
stratum c of Fig. 14, Part I). 
The rock consists very largely of glistening black crystals of horn- 
blende interspersed with white feldspar and quartz in minor amount. 
The hornblendes are all parallel. This feature does not impart to the 
rock schistose cleavage; the structure is irregular, but shows an approach 
to linear parallel cleavage. 
The microscope reveals, as the constituents of the amphibolite, green 
hornblende, labradorite, and some quartz, with accessory grains of zircon, 
tourmaline, pyrite, and pale-pink garnet. 
The present minerals and the parallel structure of the rock are the 
results of changes in the zone of anamorphism which have completely 
obliterated the original constituents. Since these minerals were produced 
the rock appears to have undergone no severe strains. 
Katamorphic alterations have resulted locally in the production of 
epidote and chlorite from the hornblende, and of muscovite from the feld- 
spar. The epidote occurs in granular aggregates gradually invading the 
hornblende crystals, and also in large well-defined plates which have sharply 
defined boundaries. In the latter case the occurrence of the epidote is 
identical with that of garnet, a mineral which is characteristic of the zone 
of anamorphism. Van Hise finds that epidote is usually a product of the 
upper zone,* but in this case it seems highly probable that it originated in 
the greater depths. Chlorite has grown along the cracks of the hornblendes, 
and even those of the garnets and feldspars. Calcite in irregular masses is 
doubtless derived from the alteration of several minerals together and 
is one of the latest growths in the rock. 
The origin of the amphibolite is problematical. It has the composi- 
tion of a basic intrusive, such as a gabbro or diorite, and may have been 
derived from such a rock. Very similar amphibolites have been describedf 
as metamorphosed limestones. The succession of thin beds of amphibolite 
* Van Hise: A Treatise on Metamorphism, U. S. G. S. Monograph xLvu, p. 321. 
y+ Emerson describes amphibolites, hardly distinguishable from this specimen, which were altered 
Paleozoic limestones. (Emerson, B. K., Geology of Old Hampshire County, Mass., U.S. G. S, Monograph 
XXIX, p. 95.) 
