438 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



Assuming all the iron to be present as limonite and the carbon 

 dioxide as cerusite this material may be interpreted as having the 

 following mineralogical composition: 



Per cent 



Limonite 4. 49 



Cerusite 3. 64 



Bindheimite 89. 83 



Quartz 2. 28 



The composition derived for the bindheimite, recalculated to 100 

 per cent, is as follows: 



Per cent 



Lead oxide (PbO) 57. 32 



Antimony oxide (Sb 2 5 ) 41. 53 



Water (H 2 0) 1. 15 



Total 100. 00 



These percentages yield ratios approximating closely to the formula 



2PbO.Sb 2 5 .^H 2 



The bindheimite usually seems to be a little less rich in silver than 

 the tetrahedrite of the same mine. That from the Hypotheek mine 

 is practically free from silver. Owing to its pulverulent and friable 

 nature, much of the bindheimite of the Ceour d'Alene district is lost 

 in handling the ore, practically all of it in any wet gravity concentra- 

 tion or washing. There is a belief among the miners that this mineral 

 is very dangerous in causing "leading" or lead poisoning. The 

 mineral can best be determined by solution in concentrated hydro- 

 chloric acid and saturation with hydrogen sulphide when red antimony 

 sulphide is precipitated. Upon dilution with water the black lead 

 sulphide is then precipitated. 



SODA NITER (683) 

 Sodium nitrate, NaN0 3 . Rhombohedral. 



Soda niter has been found in small amounts in Elmore and Owyhee 

 Counties in Idaho. 



ELMORE COUNTY 



Pure sodium nitrate occurs in thin scales and plates in the structure 

 and shrinkage cracks of a 100-foot vertical bluff of recent black basalt 

 near King Hill on the banks of the Snake River. This deposit has no 

 commercial value and is regarded by Bell as due to leaching of the 

 lava. 39 



OWYHEE COUNTY 



Soda niter occurs in impure form in several places in Owyhee 

 County southeast of Homedale, Oreg. At the Roosevelt claim, one- 



39 Robert N. Bell. Ann. Rept. State Mine Inspector. Mining Industry of Idaho for 1913, p. 211. 



