3Q 



University of California. 



[Vol. a. 





I. 



II. 



Si0 2 



49.61 



50.55 



Al 2 O s 



19.18 



20.48 



Fe 2 3 



2. 12 



2.66 



reU 



5.01 



4.02 



CaO 



ro.05 



7.30 



MgO 



4Q4 



4.24 



K,0 



1.04 



2.27 



Na 2 



5.62 



8-37 



PA 



.27 



not det. 



so 3 



trace 







3-55 



H 2 .44 



Total 



101.39 



100.33 



Sp. g. 



2.782 





It will be readily seen that the two rocks are very closely related. 

 The large amount of water in that from Point Sal is character- 

 istic of the teschenites of Europe. The water is not indicated 

 in the second, although it is certain that about the same amount 

 must be present. It appears that the Cuyamas rock is somewhat 

 richer in soda and poorer in lime. The two occurrences are about 

 75 miles apart. Although it seemed conclusive from the results of 

 the former study that the high percentage of soda could be accounted 

 for only by postulating its derivation from a soda rich mineral, yet 

 this was not actually proved. Consequently in the present study it 

 seemed best to attempt an isolation of the different components for 

 the purpose of making an analysis of each. This would settle 

 definitely the question if the large percentage of soda could be 

 derived from the feldspars, or whether its source must be looked for 

 elsewhere; for the analysis of the augite material was taken from 

 the large crystals in the coarser facies of the rock. Fragments of 

 feldspar were broken from a coarse specimen, the microscopic exam- 

 ination of which showed it to be comparatively fresh. These frag- 

 ments were powdered sufficiently fine to pass through a 60-mesh 

 sieve, and then introduced into Klein's solution, possessing a specific 

 gravity of 2.60. With this density, more than half of the material 

 still remained suspended. In order, if possible, to get rid of any 



