466 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



The mineral is apparently ordinary potash jarosite and contains no 

 soda or lead. Under the microscope the powder is pleochroic in 

 brown and nearly colorless. It is biaxial negative with small axial 

 angle and strong birefringence. The crystals are zoned and the 

 refractive index varies in different zones. The approximate indices 

 are a = 1.70, 7 = 1.80. 



The usual mode of occurrence of jarosite is as microscopic scales in 

 aggregates of earthy appearance resembling limonite. With the 

 exception of a single lot of material collected by W. F. Foshag, at 

 Pioche, Nev., no specimens showing coarse crystals like those of the 

 Idaho specimen have ever been found before. 



LEMHI COUNTY 



A specimen from the Parker Mountain mine, Parker Mountain dis- 

 trict, contains small waxy brown areas which are apparently pseudo- 

 morphs after pyrite crystals, embedded in white clay. The brown 

 material is transparent under the microscope and is composed of fine 

 grains which are uniaxial or nearly so with moderately high bire- 

 fringence. The lowest index of refraction a is about 1,702. The 

 mineral dissolves in hot concentrated hydrochloric acid and the 

 solution reacts for ferric iron and sulphuric acid. The mineral is 

 doubtless jarosite. 



PLUMBOJAROSITE (801a) 



Basic sulphate of lead and ferric iron, Rhombohedral. 



Pb0.3Fe 2 3 .4S0 3 .6H 2 0. 



The lead member of the jarosite group closely resembles ordinary 

 or potash jarosite and like it in its usual massive form closely resem- 

 bles limonite. This lead mineral has been found to be so widespread 

 in occurence in similar ores in Utah and Nevada that it is odd that it 

 has not been found from a number of Idaho mines. The only re- 

 corded locality is in Fremont county. 



FREMONT COUNTY 



Plumbojarosite has been listed by Umpleby 74 as occurring in 



oxidized lead ores of the Kaufman and Weaver mine in the Skull 



Canvon district. 



THE WOLFRAMITE GROUP 



The wolframite group includes those tungstates of iron and man- 

 ganese included under the old name wolfram or wolframite. There 

 are two recognized end members of this group, ferberite, or iron 

 tungstate free from manganese, and hubnerite, which is manganese 

 tungstate free from iron or nearly so. The group name, wolframite, 

 is therefore without strict mineralogic significance and is used 



'< J. B. Umpleby. U. S. Geol. Survey, Prof. Paper 97, p. 91, 1917. 



