4 CALIFORNIA ACADEMY OF SCIENCES. 



Between the plagioclase crystals, and closely following 

 their outlines, lie numerous grains of clear quartz with com- 

 paratively few fluid inclusions. 



The rock, according to this description, should be classi- 

 fied as a pyroxenic facies of quartz-mica diorite. 



2. Another specimen, also from Ensenada (corner Galvez 

 and Fourteenth streets), is macroscopically a fresh, not very 

 coarse grained mixture of hornblende, biotite, feldspar and 

 quaitz. Under the microscope foils of brown mica and 

 irregular grains of a dark green hornblende form the prin- 

 cipal part of the ferromagnesian silicates; there are also, 

 however, a few prismatic grains of a colorless augite (m.i- 

 lacolite). Plagioclase is present in large quantities with the 

 usual, partly idiomorphic prismatic forms, and between 

 them lie numerous quartz grains with fluid inclusions. 



The rock should, hence, be characterized as a quartz-mica 

 diorite. 



3. A specimen of beautiful and fresh granitic rock was 

 collected near the middle line of the peninsular range, at 

 the east side of San Rafael Yalley, on the road from Real 

 to Campo Nacional, near mouth of Canada del Sur. 



Very fresh, coarse granular rock with hornblende crystals 

 up to 10 mm. long, biotite foils, white, often striated crys- 

 tals of plagioclase up to 8 mm. long and much quartz. 



Under the microscope, zircone and apatite, in small quan- 

 tities, a little magnetite mostly associated with hornblende. 

 Biotite in straight, fresh foils, yellowish-brown, and with 

 very strong absorption, forms inclusions in feldspar and 

 hornblende. Dark green hornblende also with very strong- 

 absorption: a, olive green; b and c, dark green; absorption 

 of b nearly equal to that of c; one or two large, approxi- 

 mately square grains of uralitized pyroxene, probably dial- 

 lage or augite. The plagioclase of which a large quantity is 

 present is as usual partly idiomorphic, and in all respects 



