58 CALIFORNIA ACADEMY OF SCIENCES. [PROC. 3D SER. 



2. ACTINOLITE AND HORNBLENDE SCHISTS. 



The actinolite-schist occurs bedded, showing greater 

 variation than the quartzite in the thickness of the beds. It 

 also frequently exhibits plications such as occur in the 

 quartzite. Some of these schists occur in rather thin 

 beds, with a finely schistose structure, the slender needles 

 of actinolite parallel to the plane of schistosity. In other 

 cases, especially the coarser forms of the rock, it is 

 found showing no marked schistose arrangement. The 

 crystals in these coarser schists frequently have a length of 

 three or four centimeters. The rocks are more or less 

 compact, and in general are composed of columnar or aci- 

 cular actinolite crystals, but always associated with a greater 

 or less amount of other minerals. The most common 

 mineral accompanying the actinolite is talc. This is usually 

 in small amounts, but rarely it becomes the dominant min- 

 eral, forming a matrix in which the needles of actinolite are 

 embedded. Chlorite occasionally occurs with the actinolite, 

 and like the talc, this sometimes, though rarely, becomes 

 dominant. The chlorite varies in occurrence from minute 

 flakes to plates several centimeters in diameter. A small 

 amount of quartz is frequently found in these schists, and 

 occasionally both quartz and feldspar, in varying amounts, 

 occur associated with the actinolite and hornblende. 



Almost the entire area of actinolite- and hornblende-schist 

 is composed of the former. The latter is confined to the 

 area which contains the serpentine, occurring here with the 

 actinolite-schist. The rocks are coarse-grained, compact, 

 greenish black in color, and are composed of coarsely pris- 

 matic crystalline hornblende. A small amount of mica is 

 occasionally associated with it. 



3. SERPENTINE. 



The serpentine of this same area is found on the summits 

 of these hills of amphibole-schist. The hills are in the 

 neighborhood of 1,000 feet in height, and the serpentine 

 which outcrops here is two or three hundred feet in thick- 



