8ILLIMAN.1 



TELLUEIDE ORES. 691 



argentiferous tetrabedrite, native silver, and galenite. Associated with, 

 these are hessite, bournonite, jamesonite, barite, sphalerite, stibnite, 

 native arsenic, realgar, orpiment, silver-glance, chalcopyrite, marcasite, 

 native copper, malachite, pyrrhotite, sulphur, &c., with various epigene 

 species. In all, over forty mineral species are enumerated as found in ' 

 the veins of Nagyag. Compared with this abundance, we find at the 

 Eed Cloud mine only native tellurium, sylvanite, hessite, pyrite, chal- 

 copyrite, and more rarely galenite and sphalerite, with native gold and 

 an epigene species at surface. The gangue-stone is hornstone or chalce- 

 donic quartz, with feldspar. 



Possibly explorations at greater depths may develop other species, 

 but this result has not followed the deep- workings of the silver-mines in 

 Nevada, where, at the depth of 1,500 feet, the number of species found 

 is not greater than it was at the surface. A like paucity of species 

 characterizes the metamorphic and volcanic rocks of the Sierra Nevada 

 in California. 



