Kiotte.] 218 [Mayl, 



time HS is emitted. Pieces of the Stetefeldtite show the reduction 

 by becoming covered with silver wires. Tiie fact that neither silver 

 nor any of the noble metals ever occur as oxides, nor as such in salts 

 (problematical), carbonate of silver excepted, speaks against any sup- 

 position of its being contained in an oxydized state. 



The most natural grouping of the elements in proportion, as the 

 analysis gives them, is shown in the following formula : 



5R'+PJOSb^O'+15HO. 



This gives the value as found by the analysis exactly. 

 A formula reading as follows : 



2R'4-R^OSb-05-f-GHO 



would be tolerably accurate and fall within the limits of error in the 

 atialysis. 



In either case R' would denote ^ Ag'-[-4 Cu' and RO would denote 

 I CuO+1 feO. 



This composition is truly remarkable and an analogy can hardly 

 be found. It seems as though all the extraordinary peculiarities of sev- 

 eral minerals were joined iu this. We have a sulphuret, combined 

 with an oxygen salt, as in the Helvin, and an antimoniate as a hy- 

 drate, as in the case of the bleinierite. Perhaps an analogy can be 

 found by comparing the formulas of apatite, pyromorphite and 

 bleinierite. 



The question has arisen, whether this substance was not the pro- 

 duct of decomposition from tetrahedrite. If it is, the decomposition 

 has certainly produced a new and characteristic mineral, and often 

 produces it even in very different localities. But the fact that the 

 mineral is often found enclosed in solid hard quartz with sharp out- 

 lines and bordering, without any discoloration whatever from the car- 

 bonates of copper, speaks evidently for a kind at least of originality. 

 The mineral has been found iu the upper levels of mines, decomposed 

 so as to form flakes of chloride of silver, azurite and malachite, and 

 sometimes a yellow film of antimoniate of lead. 



The finest specimens, masses three and four inches in diameter, 

 come from the Empire District, 130 miles southeast from Austin. The 

 specimen sent comes from there. I hope to be able in a few weeks 

 to forward very superior pieces (if the snow blockade is raised). 



I have also found beautiful masses in the High-bridge and Silver 

 Chord ledges, in the Philadelphia District, 100 miles southeast from 

 here. Eureka furnishes a variety with lead and but 3 to 4 per cent. 

 of silver. Zone and Palmetto, as well as the Northumberland Dis- 

 trict furnish some with from 20 to 25 per cent, of silver. 



