98 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



SHOSHONE COUNTY 



The region in Shoshone County known generally as the Coeur 

 d'Alene district is the greatest galena-producing area of its size in 

 the world. The ores which have made the vast production occur 

 in fissure veins in a thick series of sedimentary rocks of Algonkian age. 

 Near Burke the principal mines are the Hercules, Tiger-Poorman, 

 Marsh, Benton, Hecla, Standard-Mammoth, Greenhill- Cleveland, 

 and Frisco. The Hercules is perhaps the richest body of galena in 

 the district. It is reported that a raise driven for 40 meters (125 

 leet) in the vein was in granular galena showing no other material 

 on any part of the walls throughout the entire length. In 1914 

 there was exposed in one stope of this mine a body of galena 12 

 meters (40 feet) wide which was very nearly pure. The ores of 

 the Hercules mine are relatively free from other sulphides, although 

 some tetrahedrite, pyrite, sphalerite, and pyrrhotite occur. The 

 Benton mine has produced galena ore rather free from zinc but 

 containing more or less pyrite and chalcopyrite. This vein is cut 

 off at shallow depth by a fault and its continuation has not been 

 found. The Hecla is another vein which produces galena relatively 

 free from objectionable sulphides, and the ore of the adjoining Marsh 

 mine is similar. The Tiger-Poorman vein system was very pro- 

 ductive, but at depth the ore became so contaminated with pyrrhotite, 

 pyrite, and sphalerite that it could not be worked profitably. The 

 Standard-Mammoth and Greenhill- Cleveland ore shoots also were 

 very productive of galena ore, but both became increasingly poorer 

 with depth. The ore from the bottom levels of these ore bodies 

 consisted of galena mixed and intergrown with magnetite, sphalerite, 

 pyrite, pyrrhotite, and chalcopyrite. Clean masses of galena and 

 silver-bearing minerals were, however, sparingly present in the 

 lower levels filling later fractures in the old complex mineralization. 

 These minerals included chalcostibite, boulangerite, chalcopyrite, 

 and pyrargyrite. The Frisco vein contains galena very much 

 intergrown with sphalerite, pyrrhotite, etc. It has not been profitably 

 worked in the lower levels. These mines all occur in the slaty seri- 

 citic quartzites of the Burke formation and occupy fissure veins of 

 high dip. The ore is for the most part confined to the fissure and 

 replaces the gouge and brecciated rock of the vein. The gangue 

 minerals are quartz and siderite. 



Near Mullan the principal lead mines are the Morning, Hunter, 

 and Star. The Morning produces some clean galena ore from veins 

 in the Revett formation. Much of the ore is a complex mixture of 

 sulphides and the ore of the adjoining Star mine is a very intimate 

 mixture of galena and sphalerite. The Hunter mine, which is the 

 only important lead mine in the Wallace formation, has galena ore 

 containing some tetrahedrite and other sulphides in a gangue of 



