394 RESEARCH IN CHINA. 
Altered basalt, No. 43.—This rock occurs as an intrusion in the Man-t’o 
shales near Kau-kia-p’u, 8.5 miles, 13.5 kilometers, north of Sin-t’ai-hién. 
An aphanitic blackish rock resembling No. 24 in general appearance. 
The lighter blotches which occur in the rock are whitish instead of greenish 
and exhibit prominent cleavage faces. 
The matrix of the rock is a mat of minute plagioclase needles with 
grains of augite and magnetite. Decomposition products, such as calcite 
and fibrous greenish and yellowish minerals, contribute largely to the forma- 
tion of this ground-mass. ‘The larger bodies in the rock are of variable size, 
and, regardless of the question as to whether they are phenocrysts or amyg- 
dules, they now consist almost entirely of calcite, with, in some cases, a 
fibrous chloritic substance and chalcedony. ‘The majority of these bodies 
are more or less round or irregular in outline, but others have fairly definite 
crystal forms which are identical with those of feldspars. These crystals 
were probably plagioclases which have been thoroughly decayed and 
replaced by calcite. 
The plagioclase of the ground-mass seems to be labradorite, but the 
crystals are so small and extensively altered that the identification can not 
be relied upon. 
The augite grains are very small and are more or less altered to green- 
ish substances. As is usual in basaltic rocks, magnetite partly altered to 
martite is abundant in the form of small grains. Throughout the rock 
there is an abundance of calcite in formless plates and clusters. It is 
doubtless a result of the weathering of the feldspars and pyroxenes of the 
original basalt. 
DACITES. 
Hornblende-dacite porphyry, No. 44.—This porphyry is known only as 
an intrusive in the Sinian limestone north of Sin-t’ai-hién. It resembles, 
however, certain dike-rocks which are associated with the Carboniferous 
formation, a few miles farther north, and we infer from this that it belongs 
to the same period of volcanic activity. Specimen from an intrusive sheet 
about 100 feet, 30 meters, in thickness, near the base of the Tsi-nan dolomite, 
9.5 miles, 15 kilometers, north of Sin-t’ai-hién. At the contact of this 
porphyry with the overlying limestones, there is very little evidence of the 
metamorphism which would be expected. 
Our specimen is so much decayed that it can not be considered a fair 
representative of the rock. There is an olive-gray ground-mass through 
which needles of hornblende and larger crystals of white feldspar are 
profusely distributed. These phenocrysts rarely exceed 3 millimeters in 
breadth. The ground-mass is microcrystalline and deeply decayed. It 
