346 KRA^IM— SERPENTINES OF THE CENTRAL [June 6, 



Copiapite is less abundant than melanterite, the oxidation of 

 which gives rise to it. 



Redingtonite was first found in the Redington Mine at Knoxville 

 and described by Dr. Becker. 



Knoxvillite, according to Dana, occurs with redingtonite at 

 Knoxville. 



Linwnite and hematite are products of decomposition of the ser- 

 pentines and impart the red color to the soil derived from it. Com- 

 mercially they are not important on account of impurity. 



Conclusions. 

 In the preceding pages the following facts are demonstrated : 



(A) The serpentines are derived from basic eruptive rocks. 

 For this speaks the irregularity of the serpentine bodies, which 



is a typical character of eruptive rocks. A glance upon the map also 

 shows that, with the exception of the Mount Diablo serpentine, the 

 areas have an approximately northwest-southeast trend, which cor- 

 responds to lines of structural weakness in the Coast Ranges. 



Furthermore, the serpentine contains olivine and chromite. The 

 first, with the exception of altered magnesian limestones, is found 

 only in eruptive rocks. 



The second has, to the writer's knowledge, never been found 

 in serpentine derived from sedimentaries. 



The chemical composition of the serpentine shows it to be related 

 to peridotites. 



Pseudomorphs after pyroxenites are not very well possible in ser- 

 pentine derived from sedimentaries. 



(B) This eruptive rock was fairly uniform and its time of intru- 

 sion falls in a period which followed the deposition of the Knoxville 

 beds. 



The uniformity is demonstrated by the analyses of the rock 

 which show it to be of a basic nature. 



The mineralogical investigation shows it to be a Iherzolite, and 

 the serpentine derived from it a Iherzolite serpentine. 



However, variations in this rock occur which are represented by 

 lenticular bodies of pyroxenites which are usually of small dimen- 



