THE MINERALS OF IDAHO 83 



this rock which consists chiefly of irregular bunches ot quartz and 

 muscovite. The molybdenite crystals are in some cases 2 cm. across 

 and have a radiating structure, as have also the mica crystals with 

 which it is associated. The deposit is irregular and bunchy and has 

 been opened only by a few shallow open cuts. 47 Specimens in the 

 National Museum labeled as from veins in granite 21 miles by trail 

 southwest of Porthill, Idaho, consist of rosettes of molybdenite folia 

 up to 1 centimeter in diameter in quartz with some mica (niargaro- 

 dite). Very small amounts of molybdenite occur in a quartz vein 

 with pyrite in a small diorite intrusion south of Lakeview near Lake 

 Pend d 'Oreille. 



CUSTER COUNTY 



Small scales of molybdenite are present in ore taken from the bins 

 of the north tunnel of the Empire mine at Mackay where it is asso- 

 ciated with chalcopyrite in garnet rock. Specimens from the Bay 

 Horse district show small rosettes of molybdenite folia up to 7 milli- 

 meters in diameter in quartz. Others show weathered molybdenite 

 partly altered to powellite. A sample sent to the National Museum 

 by Dr. C. L. Kirtley from Challis shows small scales of molybdenite 

 associated with quartz and pyrite in a heavy pyroxene rock. 



ELMORE COUNTY 



This mineral is also reported to occur in a vein on Sheep Creek. 

 A specimen sent in by W. R. Decker from Pine, in Elmore County 

 shows good foliated molybdenite partly altered to molybdite on 

 granite. 



IDAHO COUNTY 



Molybdenite occurs on W. G. Cadby's claims 12 miles from 

 Warren and one half mile west of the South Fork of Salmon River 

 and four miles north of the wagon road between Warren and Dustins 

 Ranch on the South Fork. It is associated with pyrrhotite in gar- 

 netized schist and hornblende sills, being usually in very fine grains, 

 although crystals over a centimeter in diameter occur locally. The 

 zone in which the molybdenite occurs is about 50 meters wide and 

 700 meters long. 48 



LEMHI COUNTY 



Molybdenite forms thin films and coatings on fractures and 

 minute scales intergrown with the primary minerals of the tungsten 

 deposits of the Blue Wing district. Considerable amounts occur 

 also on A. R. Mulkey's claim on west Eightmile Creek in the Lemhi 

 Range 12 miles west of Leadore. The country rock is granite or 

 monzonite and the mineral is contained in a very irregular or bunchy 

 pegmatite vein. Several hundred kilograms of molybdenite were 



« 7 D. C. Livingston. Univ. of Idaho School of Mines Bull. 2, p. 40, 1919. 

 « D. C. Livingston. Univ. of Idaho School of Mines Bull. 2, p. 42, 1919. 



