92 GEOLOGY OF TONOPAH MINING DISTRICT, NEVADA. 



ANALYSIS OF OXIDIZED ORE. 



Concentrates from a picked sample of thoroughly oxidized ore from the 

 300-foot level of the Valley View vein were found by Doctor Hillebrand to have 

 the following compositipn: 



Analysis of oxidized ore from Valley View vein. 



Siliceous matter 16. 53 



Gold 62 



Silver "62.54 



Lead 32 



Copper ." &.09 



Iron '. 1.39 



Manganese .07 



Zinc - 10 



Selenium .78 



Tellurium None. 



Arsenic .03 



Antimony -15 



Sulphur Not -det. 



Total 82.62 



Concerning this analysis Doctor Hillebrand adds: 



"After extraction of all the silver chloride by ammonia the residue was boiled 

 with hydrochloric acid until silver no longer appeared in the filtrates. The insoluble 

 matter then consisted, aside from gangue, of a little pyrite, of the same black gold- 

 silver alloy found in the unoxidized ore, and of a pyritic-looking mineral, which 

 latter yielded to dilute nitric acid much silver and some selenium, leaving a residue 

 of gold." 



COMMENT ON THE ORE ANALYSES. 



Aside from the complex carbonate of lime, manganese, magnesia, and iron, 

 the analysis of the primary sulphide ore indicates (p. 89) the presence of a large 

 amount of silver sulphide argentite. Antimonial sulphides of silver, polybasite, 

 very likely stephanite, and smaller amounts of galena, blende, pyrite, and 

 chalcopyrite are also indicated. Of very great interest is the presence of a 

 considerable amount of selenium, which occurs, in part at least, as a silver 

 selenide, and the absence of its usually closely associated element tellurium. 

 The chemical form of the gold is 3 r et uncertain. 



It is fair to assume that the oxidized ore in its primary sulphide state may have 

 had a composition somewhere relatively near that of the primary sulphide analyzed. 

 The two analyses may then be compared with the object of perceiving the changes 

 effected by oxidation. There is no element which can be considered as having 



a 38.10 as lulpbldeg; 24.44 us chloride, selenitic, and alloy. 6 Mostly oxidized. 



