406 RESEARCH IN CHINA. 
irregular border of olive-green hornblende with which is associated magne- 
tite and biotite in small shapeless bits. The whole is inclosed, as in former 
cases, by a network of augite and labradorite. Evidently the inner portion 
of this phenocryst furnishes a case of the very familiar habit of hornblende 
in inclosing pyroxene. The exterior intergrowth of the augite and feld- 
spar with the hornblende, biotite, and magnetite may be due to alternate 
crystallization and resorption by the still liquid magma of portions of 
crystals which formed during the earlier stages of cooling. Lacroix 
describes a similar condition which he observed in certain French lavas,* 
and he suggests the explanation just given. 
The pyroxene of the ground-mass is a colorless augite, occurring in 
short prismatic bodies in which, however, the crystal faces are seldom dis- 
cernible. In many instances the edges appear to have suffered corrosion. 
Abundant inclusions of iron ores in very small particles are characteristic 
of this mineral. In the incipient alteration of the pyroxene a colorless 
secondary chlorite is developing along the cracks and edges. 
The biotite is reddish-brown and highly pleochroic. It is a primary 
constituent of the rock and occurs in the form of short scales which include 
many small bodies of titanite and iron ores. Its association with horn- 
blende and magnetite in the irregular intergrowths of the phenocrysts has 
already been mentioned. In the alteration of the mica a fibrous aggregate 
is produced which appears to consist of a nearly colorless chlorite. 
White augite andesite, No. 50.—Like the last this is a marginal phase of 
the massive basic intrusion southeast of Yen-chuang. ‘The specimen was 
taken from the edge of the intrusion very close to its contact with the 
limestone. 
A very fine-grained grayish-white rock in which no dark minerals are 
visible except as minute ill-defined specks. On the weathered exteriors 
phenocrysts of white feldspar may be seen, but these are almost invisible 
on freshly broken surfaces. It is closely allied in composition, as well 
as by its relation in the field, to the porphyry just described. It is more 
acid in composition, however, and there is a notable absence of hornblende, 
iron ores, micas, and other dark-colored constituents. 
The rock consists essentially of a medium-grained mass of plagioclase 
with a little augite, the interstices between the larger crystals being filled 
with a considerable amount of minutely granular feldspar and quartz. 
Iron ores are almost entirely absent, and the ocher-colored specks, which 
are visible in the hand-specimen, are seen to be secondary discolorations. 
The feldspar of No. 50 seems to have a higher percentage of soda than 
that of the augite porphyry (No. 49) and the zonal structure is not so promi- 
* Lacroix: Minéralogie de la France, vol. I, p. 668, 
