336 



KRAMM— SERPENTINES OF THE CENTRAL [June 6, 



Analyses of Serpentines, Mount Diablo. 



I. II. III. IV. 



SiOo 53-25 36.57 40.50 41.52 



P.^Os trace • 



Cr.Os 54 -33 -41 



AI.O3 2.80 .95 .78 1.57 



Fe.^Os 69 7.29 4.01 3.50 



FeO 5-93 -37 2.04 1.07 



NiO 07 .31 .11 



MnO 09 .10 .13 .29 



CaO 16.22 .14 .39 .44 



IMgO 19.91 40.27 37-43 36-84 



Na^O 19 .31 .28 



K2O trace trace .16 



H:;0 at 105° C 05 .94 2.81 3-32 



H2O above 105° C 24 12.43 10.94 12.51 



99.98 100.01 99-99 101.06 



I. Fresh pyroxenite with some olivine. W. H. Melville, analyst. 



II. Bastite with fine seams of chrysotile. W. H. Melville, analyst. 



III. Serpentine. W. H. Melville, analyst. 



IV. Serpentine weathered interwoven with quartz and calcite. W. H. 

 Melville, analyst. 



Areas of considerable extent are found about fifteen miles south- 

 east of Livermore to the west of the Arroyo Mocho in Contra Costa 

 County, a iew miles north of the Santa Clara and Contra Costa 

 dividing line. 



Other areas are to the west of the Arroyo del Valle to the south 

 of Livermore in Contra Costa County, and in Santa Clara County. 

 Still others are about six miles to the northwest of Mount Hamilton 

 in Santa Clara County. 



The location of these areas is best shown by the accompanying 

 map. 



These areas were not visited by the writer, but specimens of the 

 serpentine are in the Stanford University collection. 



Some of these are altered to the greenish-yellow slippery mass in 

 which all genetic indications are obliterated ; others exhibit the char- 

 acteristics of a Iherzolite serpentine. The presence of lenticular 

 bodies of pyroxenites is indicated by specimens of diallagite and en- 

 statite-pyroxenite which come from the serpentine areas northwest 

 of Mount Hamilton. 



