GLAUCOPHANE AND ASSOCIATED SCHISTS 739 



Of less importance though widely distributed and intimately- 

 associated with the glaucophane is the light green actinolite 

 schist which occurs with the glaucophane schist in irregular 

 layers and masses. Both of these schists have garnets abun- 

 dantly developed in them. 



Dikes of serpentinized peridotite and also of diabase are com- 

 monly found in apparent association with the schists. It was on 

 such an association that Dr. F. L. Ransome 1 based his hypothesis 

 that the Angel Island glaucophane schist is the result of the 

 contact action of fourchite and peridotite intrusions in the 

 Golden Gate or Franciscan sandstones. Ransome's conclusions 

 are questioned, however, by Turner, 2 who says: "It is yet to be 

 demonstrated that these schists are the result of contact 

 metamorphism." 



In a short note in his paper on metamorphism, Professor C. 

 R. Van Hise 3 refers to the glaucophane schists of the northern 

 end of Calaveras Valley, in Alameda county, as resulting from 

 dynamic agencies, and says they are formed from igneous rocks 

 by crushing. 



The writers have examined several localities where the schists 

 occur, and where their relationship with accompanying rocks is 

 clear. The principal ones are four in number: one about two 

 miles southwest of Healdsburg, Sonoma county, one at Camp 

 Meeker, Sonoma county, one mentioned by Van Hise in the 

 northern end of Calaveras Valley, Alameda county, and one on 

 Tiburon Peninsula, Marin county, in which the lawsonite 

 described by Ransome 4 occurs. Besides these, many smaller 

 exposures have been studied between Healdsburg and San Luis 

 Obispo county, and especially in the region around the bay of 

 San Francisco. 



'"The Geology of Angel Island," F. Leslie Ransome, Bull. Dept. of Geo/. 

 Univ. of Calif ., Vol. I, No. 7, p. 211. 



2 Loc. cit., p. 491. 



3 " Metamorphism of Rocks and Rock Flowage," C. R. Van Hise, Bull. Geol.Soc. 

 Am., Vol. IX, p. 313. 



4 "On Lawsonite, a New Rock-Forming Mineral from the Tiburon Peninsula, 

 Marin county, California," F. Leslie Ransome, Bull. Dept. Geol., Univ. of Calif ., 

 Vol. I, No. 10, p. 311. 



