ROCKS FROM NORTHERN AND CENTRAL CHINA. 369 
Both of these minerals have also undergone more recent, although 
slight, katamorphic changes which have resulted in the production of 
granules of epidote, quartz, etc. Other changes, characteristic of this 
zone, appear in the alteration of the ilmenite to leucoxene, and of the mag- 
netite to pyrite and hematite. In this rock one also finds small grains 
of rutile, many of which, like the ilmenite, have narrow borders of titanite, 
as described by Hobbs* and others. Allanite inclosed in epidote is not 
uncommon here. 
Biotitic hornblende schist, No. 21.—This mica schist appears to be one 
of the oldest constituents of the basal complex. It is so intimately associ- 
ated with the gray gneisses that it was not found practicable to ascertain 
the relationship between the two, but on several occasions lenticular bodies 
of the schist were found included in large masses of the gray gneisses, 
as if they were bits of the older rock torn off by a rising granitic magma. 
Specimen taken from such an inclusion in the gneiss at the mouth of 
the ravine about 1 mile, 1.6 kilometers, west of Ch’ang-hia. 
A rather imperfectly schistose, dark, reddish-brown rock in which dark 
micas cover the cleavage faces. It differs from Nos. 27 and 28, chiefly in 
having a larger proportion of quartz, feldspar, and biotite, and from all the 
preceding members of the complex in the red color of its feldspars. The 
hornblendes, and especially the micas, are arranged in streaks with the 
axes of the individual crystals roughly parallel. Most of the orthoclase 
and quartz occurs in small irregular grains, and even among these the more 
elongated crystals lie with their axes parallel to the schistosity. There are, 
however, a few larger feldspars which are situated in ‘‘augen’’ around 
which the micas and hornblendes bend in the same manner as in the con- 
glomeratic schists. The corners of these “‘augen”’ are filled with granulated 
feldspars. It is believed that these are primary feldspars which have been 
only partially reduced during mechanical deformation of the original rock. 
Since the deformation all of the feldspars have undergone weathering, and 
they are now clouded with gray and reddish decomposition products. 
On the whole, biotite is rather more prominent in this rock than horn- 
blende. It is probably a secondary development derived in part from 
the alteration of the hornblende; this would result from a further advance 
of the alteration noted in Nos. 27 and 28. ‘The mica flakes have begun 
to lose color along the cleavage cracks and in many cases are partially 
altered to chlorite and epidote. The same minerals are likewise produced 
by changes in the hornblende. 
Several varieties of the iron ores occur in abundant small grains. 
Magnetite is probably the most common and is distinguished by its charac- 
* Wis, Acad. of Sci. Transactions, vol. vit, pp. 155-159. 
