268 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



BISMUTITE (306) 

 BISMUTH OCIIER 



Basic bismuth carbonate, Bi2O3.CO2.H2O. Amorphous, earthy. 



Bismutite or a related bismuth carbonate probably occurs at 

 various places in Idaho as an alteration product of primary bismuth- 

 bearing sulphides. The following occurrences have been noted. 



BOISE COUNTY 



Grains of a whitish mineral called "bismuth" are reported to occur 

 commonly in placer concentrates from the Leary and Brogan placer 

 tract one-half mile a little north of east of Placerville. A sample of 

 this material consists of gray and lusterless grains having a suggestion 

 of a fibrous structure or the columnar appearance of bismuthinite. 

 A grain which was examined has a hardness of about 4, specific 

 gravity 4.96. It is tough and tenacious and exhibits a waxy luster 

 on fresh fracture. The mineral is soluble with effervescence in hot 

 hydrochloric acid. Under the microscope it is very fine grained and 

 crystalline with moderately high birefringence and very high refrac- 

 tive indices. 



CUSTER COUNTY 



Little cavities left by the oxidation of bismuthinite in rusty quartz 

 specimens from the Empire mine, Washington Basin district, are 

 partly filled with an earthy pulverulent dirty white hydrous bismuth 

 carbonate. 



KOOTENAI COUNTY 



Small amounts of dirty white earthy bismuth carbonate occur in 



cavities in quartz from near the surface in the veins containing 



disseminated native bismuth in Carver and Varnam's Bismuth 



King property on Beauty Bay Creek near Beauty Bay, Lake Coeur 



d' Alene. 



ORTHOCLASE 



POTASH FELDSPAR 



Potassium aluminum silicate, Monoclinic. 



K 2 0. AI2O3. 6Si0 2 . 



Orthoclase is a common constituent of numerous igneous rocks, 

 among them granite, granodiorite, monzonite, rhyolite, etc. In 

 these rocks the orthoclase is commonly in relatively small grains and 

 crystals and no specimens of these rocks in which the feldspar 

 exhibits any especial interest have been seen from any Idaho locality. 

 Only a few occurrences are mentioned. In granitic regions there are 

 often found as rounded or lenticular segregations in the granite or 

 dikelike or veinlike masses in either the granite or adjacent rocks, 

 coarse aggregates of crystals ol feldspar with quartz, mica, and some- 



