4:02 F. A. Genth — Contributions to Mineralogy. 



1. 2. Ratio. Calculated. 



Ag 79-13 7907 -732 4 79-50 



S b--rj -188 1 5-89 



Se 14-82 -188 1 14-61 



99-75 100 



Represented by the formula : Ag 3 S + Ag s Se. 



All the other specimens were more or less altered ; the agui- 

 larite crystals had become rounded, and in the proportion to 

 the extent of the alteration, their crystalline form was more or 

 less obliterated. They often were penetrated by round holes, 

 showed the presence of metallic silver and were coated with. 

 microscopic iron-black crystals, sometimes in. apparently, hex- 

 agonal scales. Although this coating was quite brittle. I did 

 not succeed in obtaining the unaltered nucleus of aguilarite in 

 a state of purity, as has been proved by the following analyses : 



1. 2. 3. 



Ag 78*09 77-85 75-75 



S not clet. 7'55 8'32 



Se 12-39 12-22 not det. 



5b. As. Cu, etc.. not determined. 



I was able to separate, in a state of approximate purity, a little 

 over half a grain of the scaly brittle iron-black product of alter- 

 ation, which gave : 



Ratio. 



Ag _■ 67-08 "621 5-S4 116 



Cu 6-44 101 0-94 2 



£•::::::::::: €l S!?h« «• 2 



S 13-62 -426 3'98 8 



100*07 



Giving the molecular ratio of a cupriferous stephanite 5(Ag, 

 Cu) s S+(Sb 3 As) s S a with an admixture of metallic silver. 



2. Sdeniferous BismuthinUe and Guanajuatite. 



A. Sdeniferous Birnnuthinite. — As crystallized Guanajua- 

 tite. Messrs. Geo. L. English & Co. sent me for identification 

 a small specimen, consisting of slender, striated crystals, about 

 5-- in length and 0*5 to 1™™ in thickness with distinct braehy- 

 diagonal cleavage, imbedded in indurated clay. Color light 

 gray, some crystals showing a yellowish tarnish. Sp. gr. = 6*306. 

 The analysis stave : 



