76 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



reports have not been available, 30 except in the case of the Minidoka 

 occurrence as follows: 



MINIDOKA COUNTY 



David T. Day investigated a number of black sands from Idaho 

 with especial reference to their platinum content, and reported that 

 several of them contained platinum, the richest, a Snake River black 

 sand from near Minidoka, assaying 0.018 ounces of platinum to the 

 ton. 31 Bell carefully investigated this occurrence and found that the 

 residue yielding this result represented a concentration from the 

 gravels of several thousand to one. The platinum occurs in the 

 fine sands along Snake River but is too thinly scattered to be of 

 commercial value. It is associated with the gold in the gravels but 

 can not be detected by panning, although invariably encountered in 

 cleaning amalgam. In the operation of the Sweetzer-Burroughs 

 dredge near Minidoka platinum was always observed at clean-up 

 time as ashy gray particles which floated when the amalgam was 

 thinned with mercury for the purpose of separating foreign materials 

 from the gold. One-fourth ounce of platinum obtained in this manner 

 is in the possession of Louis Sweetzer of Rupert, Idaho. The heavy 

 minerals of the concentrate form about one-fourth to one-third of 

 1 per cent of the gravel and after the free gold is amalgamated out 

 the residue assays less than $5 a ton in gold. After amalgamation 

 one sample of black sand assayed $3 a ton in gold, with only a trace of 

 platinum. 32 



IRON (25) 



Native metallic iron. Fe. Isometric. 



LEMHI COUNTY 



No occurrence of terrestrial iron is known in the State. For the 

 sake of completeness it seems desirable to mention the metallic iron 

 of a small meteorite which was found in 1895 in placer washings on 

 Hay den Creek in Lemhi County. This object was kidney shaped and 

 weighed about 275 grams. The metal showed coarse octahedral 

 structure on etched surfaces and was rich in ferrous chloride. So 

 far as known no analysis has ever been made. 33 



REALGAR (26) 



Arsenic monosulphide, As S. Monoclinic. 



CASSIA COUNTY 



Dr. E. S. Larsen found that the pulverulent red mercurial material 

 of the ore from the Black Pine cinnabar prospects in Cassia County 

 contained considerable arsenic and writes that it is probably a mixture 



*° F. C. Schrader. U. S. Geol. Survey, Bull. 624, p. 120, 1917. 



81 David T. Day and R. H. Richards. U. 8. Oeol. Survey. Mineral Resources U. S. for 1905, p. 1195. 



82 Robert N. Bell. Ann. Rept. State Inspector of Mines for 1906, p. 115. Boise. 

 " W. E. Hidden. Amer. Journ. Sci., vol. 9, p. 367, 1900. 



