78 BULLETIN" 131, UNITED STATES NATIONAL MUSEUM 



OWYHEE COUNTY 



Stibnite occurs abundantly in the Flint district in silver bearing 

 quartz veins. In the Rising Star mine needles and blades of this 

 mineral up to 5 cm. in length occurred with silver minerals in coarse 

 white comb quartz (Cat. No. 1287, U.S.N.M.). In the Flint mine 

 it is abundant as granular masses in quartz in the upper levels, espe- 

 cially the third level, and decreases in amount with depth. In the 

 Mammoth district stibnite occurs in seams of bluish quartz on the 

 hanging wall of a large gold-silver-bearing quartz vein in the Sunset 

 Claim on Boulder Creek 1 y% miles above Duvall Ranch. In the Shore 

 Claims on East Creek stibnite in masses up to 30 cm. in width is 

 abundant in white quartz. 



SHOSHONE COUNTY 



Stibnite has been mined from a number of deposits in the Coeur 

 d'Alene district in Shoshone County and two small plants were built 

 years ago to reduce the ore or convert it to oxide. The oldest mine 

 is that known as the Coeur d'Alene Antimony, immediately beside 

 the stream near the mouth of Pine Creek. The vein lies in a strongly 

 crushed zone along a flat fissure, possibly a thrust fault, in typical 

 blue slaty argillites and shales of the Prichard formation. There is 

 no marked dissimilarity in the wall rocks on the two sides of the 

 fissure. In one exposure the footwall of the fissure contained a large 

 number of seams of translucent quartz 1 to 2 cm. wide which con- 

 tain some pyrite but no stibnite, and cut off by the quartz of the 

 stibnite vein. These do not occur in the hanging wall at this point. 

 The ore-bearing vein lies in the center of the crushed zone and has 

 an average width of half a meter, but in places reaches 2 meters. 

 The filling consists of semitranslucent to opaque white quartz carry- 

 ing varying proportions of stibnite. Even where there is no visible 

 stibnite the quartz has a cloudy appearance and gives a reaction for 

 antimony. Minute light colored grains of sphalerite occur dissem- 

 inated in the quartz but no galena is known in the vein. The vein 

 quartz is everywhere checked by close-spaced fractures which are less 

 noticeable in the richer ore. There are some indications that the 

 stibnite may be later and a replacement of the quartz. The stibnite 

 is said to be entirely confined to the quartz and never occurs in the 

 walls of the vein or in the gouge of the fissure. 



The mill concentrates carry some gold and the statement was made 

 by the manager of the mine that the gold content ran higher when 

 much footwall rock was milled. The footwall contains numerous 

 isolated crystals, streaks and bunches of crystalline yellow pyrite 

 similar to that occurring throughout the Prichard rocks in the Pine 

 Creek area. The pyrite stringers are cut by the small quartz seams 

 which, in turn, are older than the stibnite vein. Since the above 



