1885.J 



37 



[Genth. 



was not slightly contaminated with, pyrite and quartz. From the amount 

 of iron found, the quantity of pyrite was calculated, and this and the 

 quartz deducted from the material taken for analysis. 



For comparison I have analyzed the cosalite from the Alaska Mine. 

 This is free from pyrite, but contaminated with chalcopyrite, the amount 

 of iron found gave that of chalcopyrite, which, together with quartz, were 

 deducted from the material used for the analysis. 



The following results were obtained after deducting in analysis I, 



% of 



0.216 



0.201 



100.08 100.17 



Atomic Ratio of (PbCu 2 Ag 2 ) : Bi : S 



99.88 

 2:2:5 = 2 (PbAg 2 Cu 2 ) S. Bi 2 S, 



6. Schirmerite and Beegerite. 



Under the name schirmerite I described, in 1874, a mineral from the 

 Treasury Mine, Geneva District, Park county, Col., of the formula 

 PbS. 2Ag 2 S. 2Bi 2 S s , which I had received about twelve years ago from 

 Mr. Schirmer. Later, he sent me as schirmerite several specimens from 

 the Treasury Vault Mine, Summit county, Colorado, and has furnished the 

 latter mineral to numerous friends. He has not been able to give me 

 another specimen of the original schirmerite, ami I do not know that it has 

 been preserved in any collection. 



When I took up the investigation of the sulphobismutites above 

 described, I observed that the original schirmerite, which was bright and 

 fresh when received, had tarnished, was quite dull, and some portions 

 almost black, while the mineral from the Treasury Vault 3Iine was quite 

 fresh in appearance. As this indicated a diflerence in the composition, its 

 true nature was endeavored to be established by an analysis. 



That from the Treasury Vault Mine occurs in small particles and 

 patches, the largest about 10 mm in size, disseminated through quartz, asso- 

 ciated with cubical crystals of pyrite, very little chalcopyrite, and, in some 

 of the cavities, a yellowish earthy coating, probably of bismite. 



