THE MINERALS OE IDAHO 129 



Xodules of pyrite inclosed in clay of Neocene lake beds on Turners 

 claim near Idaho City contain some gold and silver. 10 In ore from 

 the gold vein of the Golden Age mine, Pioneerville district, auriferous 

 pyrite occurs in cubic crystals with sphalerite, and in a specimen of 

 typical ore from a stope below the tunnel level of this mine it is 

 abundant in grains and imperfect bright orystals with galena sphaler- 

 ite and tetrahedrite, disseminated through somewhat crushed quartz 

 associated with sericitized granite. In a specimen from the Coon 

 Dog No. 1 vein striated cubic crystals of pyrite up to 1 cm. on an 

 edge are embedded in quartz with chalcopyrite and sphalerite, the 

 latter being coated on fractures with covellite. In the Coon Dog No. 

 4 pyrite occurs in coarse cubic crystals thickly disseminated in quartz 

 in a 65 cm. (26-inch) vein of sulphides in granite porphyry, where it 

 is associated with abundant chalcopyrite and a little of a reddish 

 gray antimonial mineral which may be tetrahedrite but which re- 

 sembles famatinite. This ore contains good values in silver. Masses 

 of coarse imperfect striated pyritohedral crystals occur in ore 

 from the Gem of the Mountains mine, and in the Overlook mine 

 coarse imperfect pyrite crystals are intergrown with galena, sphalerite, 

 and tetrahedrite forming masses of sulphides in quartzose gold ore. 

 In the Blackbird tunnel on the Enterprise vein small brilliant 

 pyrite crystals occur disseminated through sericitized rock and inter- 

 grown with sphalerite in the ore, and small brilliant pyritohedral 

 crystals are present in granite on the Fairmont claim. 



In the Pearl district much of the gold ore occurs as narrow seams 

 of sulphides in sericitized granite consisting principally of sphalerite 

 and pyrite. Specimens from the Lincoln mine contain small pyrite 

 crystals showing oscillatory combination of cube and pyritohedron 

 in drusy cavities in dark brown sphalerite. Specimens from the 

 Black Pearl dump consist of masses of p} r rite with sphalerite and 

 galena in sericitized granite. 



CLEARWATER COUNTY 



Pyrite is common in gold ores. Specimens from the Lolo M. & 

 P. Co. property, Musselshell (Weippe) district contain pyrite cubes 

 in quartz up to 2 cm. in diameter in part altered to pseudomorphs of 

 limonite. 



CUSTER COUNTY 



Next to chalcopyrite, pyrite is the most abundant primary sul- 

 phide in the lime-silicate contact deposits in limestone in the Alder 

 Creek district. It occurs both as coherent grains and as intricately 

 fractured grains with chalcopyrite along the fractures. The chalcopy- 

 rite in many such specimens represents more than half the total area. 

 In some places the pyrite is interstitial with respect to garnet cry- 



io\Valdemar Lindgren. U. S. Geol. Survey, 18th Ann. Rept., pt. 3, p. fi05, 1898. 

 54347— 26t 10 



