1912 ] Eakle: The Minerals of Tonopah, Nevada 



7 



The few carbonates are of probably more recent formation 

 than those minerals derived by the general oxidation of the 

 deposit. 



DESCRIPTION OP THE MINERALS 

 Native Elements : Gold and Silver 



Gold. — Free gold occurs as small flakes and grains in the 

 narrow black bands of argentite, on the borders of small, irregu- 

 lar veins and seams of quartz, mostly in the vicinity of the 

 Valley View vein. Arborescent groupings of deformed octa- 

 hedrons and rhombic dodecahedrons have occasionally been 

 found in some of the mines. Gold occurs in very limited quanti- 

 ties in rich silver ore, the general ratio of gold to silver being 

 about 1 to 90. The metal appears to have been deposited 

 originally with the silver minerals, either as visible particles 

 or later made visible through the decomposition of the silver 

 minerals containing it. No tellurides have been found in the dis- 

 trict and no traces of tellurium in the concentrates, but its near 

 relation selenium is present in over two per cent, as shown by 

 Hillebrand's analysis. It is probably a constituent of polybasite 

 or tetrahedrite, or forms a silver selenide rather than a gold 

 selenide. 



Silver. — Wires, films, and spongy masses of metallic silver are 

 frequently found accompanying the various silver minerals, 

 especially in the vugs where these are better crystallized. The 

 wires are generally attached to argentite, polybasite, tetrahedrite. 

 or pyrargyrite, and the metal is evidently a reduction product. 

 Some of the polybasite crystals have their surfaces honeycombed 

 and the small cellular cavities filled with minute capillary silver. 

 "Wire silver is prominent in the Belmont mine and one quartz 

 specimen from the 1000-foot level charged with platy tetra- 

 hedrite has a fine wire coating. 



Sulphides : Argentite, Galena, Cinnabar, Pyrite, 

 Chalcopyrite and Sphalerite 

 Argentite. — The chief mineral of the Tonopah veins is argen- 

 tite, but the sulphide is intermixed with the sulphosalt, poly- 

 basite, and possibly stephanite. The mineral is both primary and 



