THE MINERALS OF IDAHO 

 Analysis and ratios of tetrahedrite, Ramshorn mine 



165 



The ratios agree rather well with the formula proposed by Wherry 

 and Foshag, namely R 12 Sb 4 Si 3 or Rio'R" 2 Sb 4 Si3, which expanded is 

 5R / 2 S.2R"S.2Sb 2 S 3 . The iron and zinc are, however, present 

 slightly in excess of the total bivalent bases required, so that it is 

 not necessary to assume the presence of any bivalent copper, the 

 formula consequently being written 



5(Cu,Ag) 2 S.2(Fe,Zn)S.2Sb,S 3 . 



The ratio of silver to copper is 1 : 13.3 and that of zinc to iron is 

 1 : 1.54, or very nearly 2 : 3. The analytical ratios agree somewhat 

 better with the more complex formula 



10(Cu,Ag),S.5(Fe,Zn)S.4Sb 2 S 3 , 



which may be further expanded to show the relation between iron 

 and zinc to 



10(Cu,Ag) 2 S.3FeS.2ZnS.4Sb 2 S 3 . 



Such a complex formula is not ordinarily justified by a single analysis 

 and is here presented only because a tetrahedrite from Shoshone 

 County gave identical results as discussed below. 



ELMORE COUNTY 



Tetrahedrite occurs in small quantity in the Monarch mine, 

 Atlanta district. 



IDAHO COUNTY 



Tetrahedrite occurs as silver-rich grains and masses with free gold, 

 ruby silver, and pyrite in the Little Giant, Rescue, Goodenough, and 

 other veins of the Warren district, and also as a constituent of silver- 

 gold ores of the Big Buffalo, Jumbo, and other mines of the Buffalo 

 Hump district. It probably occurs in gold ores of other mining dis- 

 tricts of the county. A specimen of ore from the Black Pine mine, 

 Elk City district, contains grains of "gray copper" sparingly dis- 

 seminated in quartz with galena, sphalerite, pyrite, and free gold. 



