Alteration Products from the Black Hills, S. D. 109 



Having a larger quantity of similar but purer material from 

 the Peerless I subjected a portion of it to analysis. The air- 

 dried material loses 5*06 per cent when dried at 100° and the 

 dried mass is so hygroscopic that it regained 4*35 per cent of 

 its original weight when exposed to the atmosphere for forty- 

 five minutes, and after eighteen hours its loss amounted to 

 only a few tenths of a milligram. 



This material can be scratched with the linger nail ; absorbs 

 water with avidity and adheres quite strongly to the tongue 

 and has a clayey odor and taste. I found the sp. gr. for two 

 portions of the material 3 3 L2 and 3 - 374 respectively. Mr. 

 Ulke reports specific gravity nearly 5. Analysis of material 

 dried at 100° : 



Loss upon ignition.. 8*20 



Fe o 3 11-85 



CuO 18-02 



SnO„ 46-07 \ = 84-G5 = Soluble in HC1 



ZnO, CdO 0-51 



S0 3 trace | 



Sb 2 'O s trace J 



Gangue 1'68) 14-64 Insol. in HC1 



•Sn0 8 (Fe trace) 12-96 



99-29 



Computing the portion soluble in hydric chloride to 100, 

 obtain 



we 



H„0 





9-68 



Fe„0, 





13-98 



CuO 





21-34 



SnO„ 





54-40 



ZnO, 



CdO 



•60 



H 



0108 



108- 



11 



Fe 



0978 



17-46 



2 



Cu 



1704 



26-96 



3 



Sn 



4279 



35-41 



3-5 



Zn 



0048 



•74 





Atomic equivalents. 



^2 



100-00 



O [2883] 180-10 18 



11H.O 

 2Fe„0, 



6CuO 



7SnO„ 



This gives no approximation to any simple and evident 

 formula for the portion soluble in hydric chloride. The solu- 

 tion gave no reaction for ferrous oxide even after gentle boiling 

 indicating the absence of any ferrous, stannous or other lower 

 oxide which would reduce the ferric salt under these condi- 

 tions, while the color of the mass and the bright blue coatings 

 on the fracture planes in the quartz point to the absence of an 

 anhydrous cupric oxide. That the stannic oxide insoluble in 

 hydric chloride is present as such and ought not to be con- 

 sidered as a part of some other combination is indicated by 

 the macroscopic properties already detailed and even more 

 strongly by the deportment of the material in lumps when 



