148 



BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



grains through the quartz and as sharply bounded cubic crystals in 

 greatly sericitized fragments of wall rock which occur in the quartz. 

 The quartz is loose textured and contains small angular cavities 

 between the crystals. The galenobismutite occurs interstitially with 

 relation to the quartz crystals and projects as fibrous bundles of 

 prismatic needles into the cavities. It is clearly the youngest min- 

 eral of the vein, which is the common paragenetic position of the 

 majority of lead sulpho-salts. 



The galenobismutite is rather light gray in color and tarnishes to a 

 yellowish color. Its luster is rather more brilliant than that of the 

 antimonial sulphosalts of lead and the mineral greatly resembles 

 bismuthinite in general appearance. It forms elongated prisms im- 

 bedded in quartz or minute deeply striated crystals in open cavities. 

 The streak is black on porcelain or brownish black when rubbed. 

 The hardness is about 2.5. 



Material for analysis was secured free from other impurities than 

 quartz and pyrite as shown by microscopic study of polished surfaces. 

 After deducting these impurities the analysis gave the following 

 results : 



Analysis of galenobismutite from Belzazzar mine 



Constituent 



Lead (Pb) 



Iron (Fe) 



Copper (Cu) 



Antimony (Sb) 



Bismuth (Bi) 



Sulphur (S) (Calc.) 



Calculation of ratios 



•0.149 149X1 1.03X1 



} .279 140X2 1.00X2 

 .555 139X4 1.00X4 



The ratios yield the usual formula, PbBi 2 S 4 or PbS.Bi 2 S :> Such 

 material as the galenobismutite has long been recognized as a charac- 

 teristic mineral of rich gold ores in this region and has passed under 

 the name " antimony" in the supposition that it was stibnite. These 

 occurrences were probably in part galenobismutite and in part bis- 

 muthinite. A gray mineral resembling the galenobismutite was noted 

 in small amount associated with pyrite and a little sphalerite in 

 quartz in ore from the upper tunnel of the Granite State mine, 

 Pearl district. This may be bismuthinite or galenobismutite. 

 It was insufficient in amount for chemical examination. 



MIARGYRITE (121) 



Silver sulphantimonite, Ag 2 S.Sb 2 S 3 . 



Monoclinic. 



OWYHEE COUNTY 



Miargyrite is a comparatively rare silver mineral which had not 

 been identified from any American locality until Penfield found it in 

 specimens from the Silver City district collected by Lindgren. The 

 following description of the crystals from this locality is taken from 



