THE MINERALS OF IDAHO 79 



statement implied that the pyrite was auriferous, several gold assays 

 were made by W. McM. Huff with the following results: Pyrite in 

 slate from footwall, 50 per cent pyrite, $0.41 a ton; quartz of spur 

 veins from footwall, gold, none; quartz from main vein containing 

 microscopic needles of stibnite and rare grains of sphalerite, $1.66 

 gold a ton. These results show that the idea that the gold is derived 

 from the pyrite of the footwall is erroneous. The gold, like the anti- 

 mony, is practically confined to the quartz of the main vein. At the 

 exposure of the vein on the surface it consists of crushed quartz and 

 wall rock cemented into a breccia by limonite and dirty white oxides 

 of antimony. Apparently the vein was as rich in antimony at the 

 present surface as at any point exposed below. The antimony- 

 bearing portion appears to form a lens lying in the fissure and the 

 vein can be traced some distance beyond the workings. The ore is 

 all confined to the one vein, although there has been no crosscutting 

 done in search of other veins. No arsenopyrite or other arsenic 

 mineral was seen. The general trend of the vein is N. 25° E. and the 

 dip is from 35° to 50° NW. 38 



A number of other veins carrying notable amounts of stibnite have 

 been prospected on Pine Creek in recent years. None of these ex- 

 cept a small lens of stibnite in the Sherman mine has been seen by 

 the writer. Several carloads of ore have been shipped from the Star 

 Antimony mine located on the ridge between the East Fork of Pine 

 Creek and Stewart Creek. Stibnite forms the ore and occurs as a 

 replacement both of crushed slate and vein quartz. A little pyrite 

 and sphalerite are associated with the stibnite and the ore contains 

 some gold. A rich streak of sheared stibnite up to 50 cm. in width 

 occupies the center of the vein. The Pearson prospect on a tributary 

 to Ross Fork of Pine Creek produced 50 tons of stibnite ore in 1910. 

 The stibnite replaces sheared slate along a fissure and calcite crystals 

 line cavities in the ore. Several tons of stibnite have also been ob- 

 tained from the Hannibal claims 1 ,800 feet south of the Pearson. 37 



The Stanley antimony-gold mine in Gorge Gulch about a mile 

 above Burke produced considerable stibnite ore in 1906 and again 

 in 1915-16. The ore is coarse bladed stibnite in quartz which con- 

 tains minute grains of yellow sphalerite. The country rock is slaty 

 quartzite of the Burke formation and inclusions of wall rock in the 

 quartz of the vein contain disseminated crystals of pyrite and arseno- 

 pyrite. The ore near the surface contains numerous secondary oxida- 

 tion products. 38 Films of native gold occasionally coat rifts in the 

 stibnite. Some small lenses of stibnite occur aloug a fissure in the 



M The above notes are from observations made by the writer in 1915 in company with Lon Brainerd, then 

 manager of the mine. A more recent description appears by E. L. Jones, jr., Bull. U. S. Geol. Survey No. 

 710, p. 32, 1920. 



17 E. L. Jones, jr. U. S. Qeol. Survey Bull. 710, pp. 33-34, 1920. 



3 « Earl V. Shannon. Amer. Min., vol. 3, p. 23, 1918. 



