SERPENTINES OF THE CENTRAL COAST RANGES OF 



CALIFORNIA.^* 



(Plates XXXIV and XXXV.) 



By H. E. KRAMM. 



Communicated by Prof. J. C. Branner. 



(Received June 6, 1910.) 



Contexts. 



Introduction 315 



General Location of the Serpentines 318 



The Sulphur Creek District Serpentines 318 



The Knoxville and Clear Lake District Serpentines 321 



The Knoxville Serpentine * 321 



The Clear Lake Serpentine 325 



The Mayacmas District Serpentines 327 



The San Francisco District Serpentines 329 



The San Francisco Peninsula Serpentine 329 



The Angel Island Serpentine 331 



The Tiburon Peninsula Serpentine 331 



The Coyote Creek and Black Mountain Serpentines 332 



The Mount Diablo and Mount Hamilton Serpentines 335 



Age of the Serpentines 337 



Quicksilver in Connection with the Serpentine 337 



Mineralogy of the Serpentines 338 



Primary Minerals .' 338 



Secondary Minerals 341 



Conclusions 346 



Introduction. 



It is the object of this paper to present a petrographical descrip- 

 tion of serpentines in the central coast ranges of Cahfornia. 



The areas under discussion are found in the region south from 

 Clear Lake in 'Lake County to the New Almaden Mine in Santa 

 Clara County, a distance of about 140 miles, and aggregates perhaps 

 300 square miles. 



^^ A thesis for the degree of A.M. presented to the Department of Geol- 

 ogy- of Stanford University, May, 1910. 



Proc. Amer. Phil. Soc, xlix, 196 u, Printed September 7, 1910. 



