166 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



LEMHI COUNTY 



Gray copper ore containing 1.9 per cent of silver occurs as irregular 

 patches and grains in ores of the Blue Wing district. The mineral 

 occurs in quartz with sphalerite, hubnerite, and molybdenite. 51 



OWYHEE COUNTY 



In Owyhee County tetrahedrite is common in ores of the Flint 

 district, associated with other silver-bearing minerals, as masses and 

 grains in white quartz. 



SHOSHONE COUNTY 



Tetrahedrite is common in Shoshone County, in the Coeur d'Alene 

 district, being perhaps the only primary silver-bearing silver mineral 

 of the silver-lead ores. Its best development is in the ores of the 

 so-called "dry belt" veins, which are narrow-filled fissures in shales 



29 30 



Figs. 29-30.— Tetrahedrite. Uypotheek mine, Shoshone County 



of the Wallace formation, the Yankee Boy mine on Big Creek, and 

 the Polaris mine in Polaris Gulch being the most exploited deposits 

 of this type. The tetrahedrite, which is the most prominent ore 

 mineral, is usually massive, although small crystals have been noted 

 in vugs in ore from the Yankee Boy mine. The gangue is either 

 quartz or coarse buff manganiferous siderite and the veins also con- 

 tain some pyrite, specular hematite, galena, and a little proustite or 

 pyrargyrite. The mineral from these veins is usually highly argen- 

 tiferous and is mined as a silver ore. There are a number of veins of 

 the same general type between Kellogg and Wallace. The tetra- 

 hedrite from the Polaris mine is said to be arsenic and mercury 

 bearing. Closed tube tests did not indicate the presence of either 

 of these elements in tetrahedrite from the Yankee Boy mine. 



Tetrahedrite occurs also in many of the lead-silver ores, having 

 been especially noted in the Standard-Mammoth, Hercules, and 

 Gold Hunter mines. There is reason to believe that the silver con- 

 tent of the galena ores is more or less proportional to their tetrahe- 

 drite content and the mineral probably occurs in microscopic grains 

 in many ores in which it can not be recognized with the eye. Speci- 



51 J. B. Umpleby. U. S. Qeol. Survey, Bull. 528, p. Ill, 1913. 



