THE MINERALS OF IDAHO 229 



SIDERITE (273) 

 BROWN SPAR, IRON SPAR, SPATHIC IRON 



Iron carbonate, FeC0 3 . Rhombohedral. 



Siderite is, next to quartz, the most widespread and abundant 

 gangue mineral in the State. It is especially characteristic of 

 argentiferous lead ores where the valuable metallic minerals are 

 galena and tetrahedrite, and it occurs thus in practically every lead 

 producing district of consequence in Idaho. Siderite is also the 

 essential gangue mineral of copper-silver ores in the Bayhorse district 

 and of copper-gold ores in the Loon Creek district, both in Custer 

 County. 



BEAR LAKE COUNTY 



Siderite forms a gangue of galena in the Blackstone mine, St. 

 Charles district. 37 



BLALNE COUNTY 



Siderite is reported to occur in the Camas district with quartz as 

 the gangue of gold-bearing ores containing pyrrhotite, chalcopyrite, 

 sphalerite, and a little galena. 38 In the Elkhorn district near 

 Ketchum siderite forms the gangue of the ore of the Elkhorn mine. 39 

 In the Mineral Hill (Hailey) district siderite is a characteristic 

 gangue mineral in the lead veins in slate, among them the Minnie 

 Moore, Star, Mayflower, Red Elephant, O. K., Pass, Narrow Gauge, 

 and other mines. 40 The siderite when fresh is buff in color, trans- 

 lucent, and coarsely crystalline. Siderite is also a characteristic 

 gangue mineral in several districts of the Sawtooth quadrangle, 

 particularly the Rosetta, Warm Springs, and Smoky districts, 41 

 where siderite together with quartz occurs as the gangue of argenti- 

 ferous galena ores containing also some sphalerite, pyrite, and 

 arsenopyrite. Typical coarsely crystalline translucent buff siderite 

 occurs with galena in specimens of ore from the middle tunnel, 

 Tyrannus vein. Other specimens examined include coarse cleavable 

 buff siderite, weathering iridescent, from the Stormy Galore mine 

 near Carrietown, and medium coarse granular buff siderite forming 

 the gangue of galena, pyrite, and arsenopyrite from the Silver Star 

 mine. 



BOISE COUNTY 



Buff siderite has been noted as the gangue of galena in ore from 

 the lower tunnel of Hall Bros, property in the Deadwood district. 



« It. W. Richards. U. S. Oeol. Survey, Bull. 470, p. 182, 1911. 

 28 Waldemar Lindgren. U. S. Qeol. Survey, 20th. Ann. Kept., pt. 3, p. 208, 1900. 

 38 Waldemar Lindgren. Idem, p. 210. 

 « Waldemar Lindgren. Idem, p. 198-206. 



<i J. B. Umpleby. Ore deposits of the Sawtooth Quadrangle, Blaine and Custer Counties, Idaho. U.S. 

 Gcol. Survey, Bull. 580, pp. 221-249, 1915. 



