Blasdale.] 



Contribution to Mineralogy. 



345 



was partly decomposed by hydrochloric acid after long digestion. 

 The analysis reported in Table VI shows a remarkably high percent- 

 age of combined water, which can scarcely be accounted for unless 

 the existence of a hydrated anthophyllite be admitted. The specific 

 gravity was found to be 2.756. 



ALBITE. 



This mineral is found in the crystalline schists, especially those 

 containing quartz and glaucophane. In one mass of these schists 

 from locality B there is present a vein some six inches in width 

 and visible for a distance of some twenty feet, which consists of 

 crystals of the pure mineral. They are uniformly twinned according 

 to the albite law, but are too opaque to admit of microscopic 

 investigation. The analysis recorded in Table VI shows that the 

 mineral possesses no unusual features but clearly indicates that the 

 process of kaolinization has begun. 



NOTE ON THE PROBABLE RELATIONSHIPS OF THE ABOVE 

 .MINERALS. 



Though aside from the principal objects of the present paper, 

 some observations on the occurrences and probable genetic 

 relationships of the minerals here described are not out of place. 

 The physiographic features of the principal locality represented 

 (B) may be briefly described as a gentle hill slope extending from 

 the top of the ridge which forms the western wall of Wildcat 

 Canon, to the alluvial plane surrounding the Bay of San Francisco. 

 It is transversed by numerous small water courses, which are 

 rapidly sculpturing the slope into a series of distinct hills. The 

 principal rock formations represented are serpentine in its various 

 forms and a series of crystalline schists, both of which for- 

 mations outcrop at various points over the entire surface, but 

 are more strikingly revealed in the form of projecting masses 

 or ledges, sometimes extending to a height of twenty feet above 

 the prevailing slope. Various stages in the alteration of 

 pyroxenite, the ultimate result of which is serpentine, are to be 

 found, but the latter often assumes the form of compact blue-black 



