THE MINERALS OF IDAHO 107 



it is separated in milling mainly by the process of differential flota- 

 tion. Some mines contain much more zinc than lead and can make 

 a clean crude ore product consisting almost entirely of sphalerite. 

 The principal types of occurrences are listed below. 



ADA COUNTY 



Sphalerite occurs in the gold ores of the Black Hornet and Boise 

 districts. Specimens from the Black Hornet mine show heavy 

 masses of sulphides from streaks along the borders of a large quartz 

 vein. These sulphide streaks yield hand specimens of practically 

 pure coarse granular cleavable black auriferous sphalerite. 



BLAINE COUNTY 



In the Mineral Hill (Hailey, Wood River district) sphalerite is 

 common in the lead-silver veins both in slate and in granite and also 

 in the gold veins in granite. In the lead ores it is usually an incon- 

 spicuous mineral present in amounts too small to be a serious nui- 

 sance and very few of the mines have enough sphalerite to make a 

 zinc product. In a few mines, notably the North Star on the east 

 fork of Wood River, the sphalerite is abundant mixed with the galena 

 and other sulphides. The sphalerite of this district is usually massive, 

 fairly coarse grained and dark brown in color. 



In the Rosetta district sphalerite is common in the ores. Speci- 

 mens from the Dollarhide mine show resinous dark brown sphalerite 

 in quartz with galena and arsenopyrite. Ore from the Golden Glow 

 mine contains pure granular masses of sphalerite and very fine grained 

 grayish sphalerite intergrown with galena and boulangerite. A large 

 specimen from the New Hope (Warfield) property contains very 

 fine grained massive black sphalerite with fine grained galena. A 

 specimen labeled Neptune mine, Blaine County (Cat. No. 56536, 

 U.S.N.M.) shows golden yellow and dark brown grains of sphalerite 

 with pyrite in a gangue of quartz and rhodochrosite in a silver ore. 



BOISE COUNTY 



In the Banner district sphalerite occurs in coarse grains of a rich 

 brown color intimately associated with pyrargyrite and stephanite in 

 the richer streaks of the silver ores of the Banner mine. 



In the Quartzburg (Idaho Basin) district sphalerite is a common 

 constituent of the gold ores below the oxidized zone. Ore from the 

 Mountain Chief mine shows coarse brilliant granular dark brown to 

 black sphalerite intergrown with chalcopyrite and pyrite in a quartz 

 gangue. Specimens from the lower tunnel of the Carroll- Driscoll 

 group show masses of dark brown sphalerite up to several centi- 

 meters across in a gangue of white quartz with a little chalcopyrite 

 and tetrahedrite. The sphalerite is blue on fractures and on polished 

 cross section is seen to be largely replaced along cracks and seams 



