16 Preseott — Ilvaite from Shasta Co., California. 



The material for the analysis given above was sorted from 

 the massive ilvaite and all portions that might contain impuri- 

 ties or inclusions were carefully excluded. It was then sub- 

 mitted to H. R. Moss, whose results are tabulated (p. 15) with 

 the two analyses available for America and with the theoreti- 

 cal for HCaFe/ 1 Fe m Si 2 9 , given by Dana in the sixth edi- 

 tion of the System of Mineralogy. 



The material was air-dried at 95° C, and the total water 

 obtained by a modification of Penfield's tnbe method. The 

 only deviation from the usual course of analysis was in the 

 determination of the manganese by triple precipitation as 

 MnO, with bromine, in the filtrate from a basic acetate separa- 

 tion, and the subsequent precipitation of the chromium with 

 ammonia. 



Thanks are due Dr. A. F. Rogers, Stanford University, for 

 advice and assistance in the preparation of this note. 



