JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. V AUGUST 19, 1915 No. 14 



GEOLOGY. — Plumbojarosite and other basic lead-ferric sul- 

 phates from the Yellow Pine district, Nevada.^ Adolph 

 Knopf, Geological Survey. 



Plumbojarosite and beaverite. The gold, platinum, and palla- 

 dium in the quartz lode at the Boss mine, Clark County, Nevada, 

 are especially associated with plumbojarosite, a basic lead-ferric 

 svdphate.- The mineral occurs as small masses of comparatively 

 pure ocher enclosed in a fine-grained quartz mass, which forms a 

 replacement of a Carboniferous dolomite, the country rock at 

 the mine. It is a greenish-yellow mineral whose most obvious 

 physical feature is its smooth talc-hke feel. Under the highest 

 power of the microscope the ocher is seen to consist of perfect 

 hexagonal tablets averaging 0.01 mm. in diameter. Very rarely 

 triangular plates can be found. Dr. F. E. Wright has kindly 

 determined certain of the optical properties of the mineral and 

 for comparison has also determined the refractive indices of the 

 analyzed plumbojarosite from American Fork, Utah,^ and from 



> Published with the permission of the Director of the U. S. Geological Survey. 



2 Knopf, Adolph, A gold-platinum-palladium lode in southern Nevada. U. 

 S. Geol. Survey Bull. 620-a, 1-18. 1915. / 



3 Hillebrand, W. F., and Wright, F. E., A new occurrence of plumbojarosite. 

 Am. Jour. Sci., 4th Ser., 30: 191-192. 1910. In this paper the refractive index 

 o) is given as greater than 1.83; at that time it could not be determined more 

 closely, as index-solutions of higher indices than 1.83 had not then been 

 prepared. 



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