THE MINERALS OF IDAHO 117 



NICCOLITE (71) 

 Nickel arsenide, NiAs. Hexagonal. 



LEMHI COUNTY 



Niccolite is reported to occur as small indistinct crystals of a pale 

 copper-red color with dark tarnish in ores of the Togo claim in the 

 Blackbird district, where it is associated with smaltite and other 

 cobalt-nickel minerals. It is said to alter to annabergite. 88 



PYRRHOTITE (74) 



Iron sulphide, Fe?S 8 to FeS. Hexagonal 



The hexagonal form of iron sulphide commonly known as magnetic 

 pyrite is a fairly common mineral, occurring usually in massive 

 granular form. It may be distinguished from the more common 

 pyrite by its faintly coppery color and the property of being attracted 

 by a magnet. Localities which have been noted are mentioned below. 



BLAINE COUNTY 



Massive pyrrhotite forms a prominent constituent of the ores of 

 the Croesus, Camas, and Tip Top veins. These are gold veins in 

 granite and much of the ore consists of intergrown auriferous sul- 

 hides, including galena, pyrite, pyrrhotite, chalcopyrite, and arseno- 

 pyrite. 89 Coarse granular pyrrhotite occurs also in the ore of the 

 Golden Glow and other mines of the Rosetta district, with pyrite 

 and sphalerite in quartz. 



CUSTER COUNTY 



Pyrrhotite may be extracted in small amount from crushed samples 

 of most of the sulphide ore of the Alder Creek district. The individual 

 grains are so minute that they can be detected only with the aid of a 

 magnet. 90 In the Lost Packer mine in the Loon Creek district 

 pyrrhotite occurs sparingly as small crystals inclosed either in chal- 

 copyrite or in quartz. 91 In the Seafoam district pyrrhotite occurs 

 in a vein in limestone with galena sphalerite and pyrite. About 400 

 feet west of the Golconda discovery a vein of auriferous pyrrhotite 5 

 feet wide occurs in limestone. This pyrrhotite assays $14 a ton in 

 gold. 92 In Washington Basin pyrrhotite is the most abundant sul- 

 phide of the great sulphidic masses of the Empire ledge. 



LATAH COUNTY 



In the Hoodoo district in the Mizpah and adjacent prospects 

 pyrrhotite is common in the ores associated with chalcopyrite. It 

 sometimes forms considerable masses, often containing coarse 

 crystals of biotite. 93 



«» J. B. Umpleby. U. S. Geol. Survey, Bull. 528, p. 78, 1913. 



«» Waldemar Lindgren. U. S. Geol. Survey, Ann. 20, pt. 3, pp. 207-20S, 1900. 



•o J. B. Umpleby. U. S. Geol. Survey, Prof. Paper 97, p. 54, 1917. 



« J. B. Umpleby. U. S. Geol. Survey, Bull. 539, p. 53, 1913. 



" J. B. Umpleby and D. C. Livingston. Idaho Bur. Geol. and Mines, Bull. 3, p. 18. 



93 D. C. Livingston and F. B. Laney. Idaho Bur. Mines and Geol., Bull. 1, p. 95, 1920. 



