324 University of California. [Vol. 2. 



The calculated percentages for the mixture agree fairly well 

 with the reduced analysis, but there is nothing to indicate that the 

 substance is other than homogeneous. In view of this fact and 

 the high probability of occluded water in the analyses, the writer 

 is inclined to the belief that the mineral is wholly coquimbite, since 

 it possesses properties so similar. In this case, about one-half of 

 the iron has been replaced by aluminum, and about 10 per cent of 

 the water must be regarded as occluded. 



The analysis, calculated as a pure ferric sulphate containing 

 only the amount of water necessary for coquimbite, becomes: — 



Required for coquimbite 

 Fe 2 (S0 4 ) 3 + 9 H 2 

 Fe. 2 O a 27.99 2847 



S0 3 43. 1 8 42.70 



HX) 28.83 28.83 



1 00 1 00 



The mineral constitutes an additional member of an undoubted 

 series of sulphates, and mixtures of sulphates, in the Redington 

 Mine, resulting from the decomposition of the abundant marcasite. 



Melville and Lindgren* have reported the occurrence of copia- 

 pite, Knoxvillite, and Redingtonite from this mine, the analyses of 

 which minerals differ quite materially from the coquimbite, no 

 chromium being found in the coquimbite. 



V. ALTAITE CRYSTALS, FROM SAWMILL FLAT, TUOLUMNE COUNTY, 



CALIFORNIA. 



Some delicate little specimens of gold, cementing minute, dark 

 gray isometric crystals, came from a pocket in the Birney pocket 

 mine, near Sawmill Flat, Tuolumne County, Cal., and an analysis 

 of these crystals by Mr. W. J. Sharwood, to whom the writer is 

 indebted for these notes, shows them to be altaite crystals. 



The gold and altaite are intimately associated, some of the 

 crystals having a gold coating, while the majority are perched on 

 the ends of gold stems or wires. 



The crystals are from 1-2 mm. in diameter, and are mainly 



*Melville and Lindgren, Mineralogy of the Pacific Coast, 3890, Bull. 61, 

 U. S. Geological Survey. 



