90 BULLETIN 131, UNITED STATES NATIONAL, MUSEUM 



the North Star mine, which is on the East Fork of Wood River, the 

 ore below the oxidized zone consists of galena with pyrite, sphalerite, 

 arsenopyrite, and boulangerite. 



In the Era district argentiferous galena is the principal ore mineral. 

 In the St. Louis and Reliance mines it is present in rather small 

 amount and is associated intimately with wurtzite and is occasionally 

 in distinct crystals, which are either cubes or cuboctahedrons. In 

 the Reliance mine a little jamesonite occurs with the galena. 



In the Hamilton or Clyde district galena bearing ores have been 

 mined in prospects in Badger Creek Canyon 9 miles southeast of 

 Clyde. 



In the Lava Creek district galena occurs in silver ores where it is 

 associated with proustite, stephanite, etc., in brecciated veins in 

 volcanic rocks. A specimen from the Hub which is the principal 

 mine shows coarse granular galena with a little sphalerite of like 

 texture and fine crystals of pyrite in a gangue of calcite and rhodo- 

 chrosite. 



In the Little Smoky district a number of veins carrying galena- 

 have been worked to some extent, the Tyrannus mine having pro- 

 duced some ore. 



The Little Wood River or Muldoon district has yielded some 

 galena ore, principally from the Muldoon mine where this mineral 

 is associated with some sphalerite and pyrite as a replacement of 

 quartzites which are probably of Carboniferous age. On the Drum- 

 mond claim galena occurs in what appears to be a contact-meta- 

 morphic deposit in fine grained intergrowths with copper sulphides 

 and lime silicates. 



The Mineral Hill or Hailey district which together with the Elk- 

 horn or Ketchum district is usually called the Wood River district,, 

 is, aside from the Coeur d' Alene region, the most important lead- 

 mining district in the State. The lead-silver mines of this district 

 are noted for their large bodies of pure galena of which the Minnie 

 Moore mine is the best-known deposit. The galena from this mine 

 occurs in masses of coarse granular texture. Some of these individuals 

 are 5 to 8 centimeters in diameter and all specimens show a more or 

 less distinct lamellar structure, or a striation on certain cubical 

 cleavage planes which on close examination is found to be identical 

 with the lamination in character. The regularity of this structure is 

 not evident in many pieces, but appears very distinctly in others,, 

 and by means of numerous transition stages all forms of banding 

 are seen to represent definitely one of two phenomena. The first 

 of these is where a banding appearing on a cleavage face results from 

 a series of undulations parallel to one diagonal of the cube. The 

 reflection is seen to be simultaneous in alternate bands and to be 

 continuous from one position to the other, for the surface is simply 



