I9I0.] COAST RANGES OF CALIFORNIA. 325 



half mile. Bordering it in the north is found a dike of olivine 

 basalt, in the south the metamorphosed sandstone. 



The other area is exposed by the road from Lower Lake to 

 Knoxville about six miles from the former. It is represented only 

 by a few outcrops with an east-and-west trend. 



Both areas have very low outcrops and mineralogically corre- 

 spond with the principal body of serpentine described in the pre- 

 ceding pages. 



TJic Clear Lake Serpentines. 

 A small area of serpentine is found on the ridge north of Borax 

 Lake, west of Clear Lake and south of the Sulphur Bank IMine. 

 No specimens were obtained from this area. Becker^^ describes 

 the serpentine, which seems to resemble closely the one met with at 

 Knoxville and Sulphur Creek. Analyses are given of two varieties 

 of serpentine, the first is of a black impure looking mass with 

 phenocrysts, which are probably bastite, the second is of a purer 

 variety. For comparison they are here appended. 



Analyses of Serpentine from Near Borax Lake, Lake County. 

 Analyst not stated. 



I. II. 



Per Cent. Per Ont. 



SiOi 39.64 41.86 



AI2O3 1.30 .69 



FeO 7/6 415 



MgO 3713 38.63 



Cr-Oa 29 .24 



NiO 33 trace 



MnO 12 .20 



H2O 13.81 14.16 



100.38 99.93^ 



It is seen that in chemical character the serpentine closely 

 approaches that of Sulphur Creek. The total iron although given 

 here as ferrous probably includes also iron in a ferric state. 



Another serpentine area is located by Siegler Springs and 

 Howard Springs about seven miles southwest of Lower Lake. It 

 has a northwest-southeast trend. At Siegler Springs its width is ap- 



" Monograph XIII., U. S. G. S., p. iii, 1888. 



