158 



BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



A specimen from the California or Marguerite shaft on War Eagle 

 Mountain, Silver City district, contains finely disseminated argentite, 

 chalcopyrite, etc., forming streaks in white fine granular or flinty 

 quartz. This contains small drusy cavities lined with quartz crystals, 

 with occasional well-developed pyrargyrite crystals, 2 millimeters or 

 more in size. One of these which was measured is illustrated in the 

 drawing, Figure 28. The measurements obtained upon it are as 



follows : 



Measurements of pyrargyrite, Marguerite mine 



SHOSHONE COUNTY 



Ruby silver, which occurs sparingly in the ore of the Yankee Boy 

 mine on Big Creek and is reported from the Polaris mine, is probably 

 in part pyrargyrite, as it is rather dark in color. Specimens showing 

 thin films of pyrargyrite coating joints in galena were collected by 

 the writer from the stope above the 2,000-foot level of the Standard- 

 Mammoth ore shoot at Mace. This occurrence is interesting, as the 

 pyrargyrite apparently represented a very last stage of the vein- 

 forming activity, the earlier mineralizations here being very base 

 and low grade and containing large quantities of pyrite, arsenopyrite, 

 pyrrhotite, etc., and relatively little silver. 



PROUSTITE (145) 

 Silver sulpharsenite, 3Ag 2 S.As 2 S 3 . Hexagonal, rhombohedral. 



Proustite, commonly known as light ruby silver, is similar to pyrar- 

 gyrite, differing in being lighter red in color and in having arsenic 

 instead of antimony as an essential constituent. It is of rather fre- 

 quent occurrence in silver ores in Idaho. 



BLAINE COUNTY 



In the Era district in the Ella mine at the head of Ella Canyon 

 proustite occurs in small grains in the oxidized ores associated with 

 argentite, cerargyrite, and tetrahedrite. 37 In the Hub mine, Lava 

 Creek district, 2 miles southwest of Martin, proustite occurs with 

 stephanite in a quartz-calcite gangue. The silver minerals occur as 



" J. B. Umpleby. U. S. Geol. Survey, Prof. Paper 97, p. 121, 1917. 



