THE MINERALS OF IDAHO 291 



LEMHI COUNTY 



Actinolite occurs in the Carmen Creek mine, Carmen Creek dis- 

 trict. The ore occurs as lenses of quartz distributed through a band 

 of schist. Much of the schist is mineralized with the development of 

 pyrite, chalcopyrite, actinolite, and epidote. Much of the quartz 

 contains magnetite, but the actinolite and epidote are confined to the 

 inclusions of schist. The material is largely oxidized. The actinolite 

 has the usual green color and radiate-fibrous structure. 12 



SHOSHONE COUNTY 



Some very fine specimens of actinolite have been seen from the 

 southern part of Shoshone County. The material came from some 

 copper prospect, the location of which was vaguely described as in 

 the St. Joe country. They consist of radiating olive green fibers up 

 to 25 cm. long in pure masses up to 12 kilograms (25 pounds) in 

 weight. Other specimens in the same lot consist of scaly masses of 

 black biotite, large cubes of pyrite, and a very coarse rhombohedral 

 carbonate, probably ankerite. The actinolite fibers inclose the 

 pyrite crystals. The specimens were obtained by Harvey Ross, of 

 Kellogg and Spokane. 



HORNBLENDE (338) 



VARIETY OF AM PHI BOLE 



Variable silicate of lime, magnesia, and 

 ferrous iron represented by the formula 



Ca0.3(Mg,Fe)0.4Si0 2 with variable Monoclinic. 



amounts of alumina and ferric iron 

 probably entering as the compound 

 (Mg,Fe)0.(Al,Fe) 2 3 .Si02. 



While hornblende is of relatively common occurrence in Idaho as a 

 rock constituent, only a few of the occurrences have received any 

 special attention. 



SHOSHONE COUNTY 



In the southern part of Shoshone County, especially along the St. 

 Joe- Clearwater divide, the rocks of the sedimentary Belt series of 

 Algonkian age have been intensely metamorphosed, due in part to 

 the nearness of the great Idaho batholith and in part to dynamic 

 stresses acting under a heavy load of sediments. 13 Dikes and sills 

 inclosed in the sedimentary rocks have in places suffered in the 

 general metamorphism and have become schistose amphibolites in 

 which the original pyroxene has changed to amphibole accompanied 

 by the development of numerous garnets. Numerous metamorphic- 



H J. B. Umpleby. U. S. Geol. Survey, Bull. 528, p. 127, 1913. 



" F. C. Calkins and E. L. Jones, jr. Geology of the St. Joe-Clearwater Region, Idaho, U S. Qeol . 

 Survey, Bull. 530, pp. 75-86, 1913. 



