138 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



crystals from this locality are shown in the drawings, Figures 14, 15, 

 and 16. 



Arsenopyrite is also common in veins near Carrietown in the 

 Rosetta and Warm Spring districts west of the Hailey quadrangle. 

 A specimen from the Dollarhide mine, No. 3 level, shows arseno- 

 pyrite as small prisms in quartz with galena and sphalerite. In ore 

 from the Silver Star claim disseminated minute prisms of arseno- 

 pyrite are associated with pyrite and galena in quartz and siderite 

 and in the Stormy Galore mine minute steel gray prisms of arseno- 

 pyrite occur in wall rock inclusions in siderite. 



BOISE COUNTY 



Arsenopyrite is of very general occurrence in lode gold ores. In the 

 Pearl district ore from the I. X. L. mine consist of quartz with abun- 

 dant finely disseminated arsenopyrite. Small vugs contain brilliant 

 arsenopyrite crystals associated with minute crystals of dolomite 

 and quartz. Heavy auriferous sulphide ore from the West Coast 

 mine contains more arsenopyrite than all other sulphides together. 

 In ore from the Checkmate mine minute perfect tin-white arseno- 

 pyrite crystals occur abundantly disseminated through altered 

 granite which is seamed with quartz and auriferous sulphides. 

 Other specimens from this mine show fine massive granular arseno- 

 pyrite with pyrite and sphalerite forming heavy masses of auriferous 

 sulphides, in vugs of which arsenopyrite appears in small perfect 

 crystals. Specimens of massive auriferous sulphide ore from the 

 Mountain Chief mine, Quartzburg district, show predominant 

 arsenopyrite with pyrite and chalcopyrite and vugs with arseno- 

 pyrite crystals. A specimen from the Gem of The Mountains mine 

 of the Diana Mines Co., Pioneerville district, contains arsenopyrite 

 sparingly as crystals in comb quartz with galena and pyrite. 



CUSTER COUNTY 



Arsenopyrite occurs as an accessory mineral in the tetrahedrite- 

 siderite ores of the Bay Horse district. A specimen from the Rams- 

 horn mine illustrated by Umpleby 15 shows a seam along which 

 prisms of arsenopyrite are developed in siderite. The crystals of 

 this specimen, when freed by solution of the siderite in acid, were 

 found to have the form shown in Figure 16. The angles measured 

 on them are as follows: 



i« Joseph B. Umpleby. U. S. Oeol. Survey, Bull. 539, pi. 7, lower. 



