PROCEEDINGS OF THE NATIONAL MUSEUM 



Analysis of miargyrile from Randshurg, Calif. 

 Earl V. Shannon, analyst 



Insoluble. 



Silver 



Copper. _ 



Iron 



Lead 



Antimony 

 Arsenic.-. 

 Sulphur.. 



Found 



0. 80 



36. 20 



.02 



. 56 



. 95 



42. 46 



Trace. 



19. 27 



100. 26 



Theory 



36. 90 



41.20 

 21.90 



100. 00 



This analysis shows that the mineral is normal miargyrite, free 

 from unusual constituents. It is a mineral of relatively low silver 

 content as compared with the other silver minerals, with red streak 

 which are commonly called ruby silver, and include proustite, 



pyrargyrite, and polybasite. 



The crystals of miargyrite occur 

 either lining cavities in the massive 

 mineral or implanted on the drusy 

 quartz of the vugs in the breccia 

 ore. They are very brilliant black 

 in color but tend to tarnish and be- 

 come iridescent in the air. None of 

 those in the specimens at hand are 

 large, the most of them being be- 

 tween 1 and 3 millimeters in di- 

 ameter. They occur singly or in 

 small clusters grown together in 

 haphazard fashion. No recognizable 

 twins were found. 



This mineral is monoclinic in 

 crystallization and crystals from all 

 localities are characterized by a 

 rather peculiar general habit, being 

 thick tabular parallel to the base 

 c (001) with a predominance of faces 

 lying in the zone between the front 

 pinacoid a (100) and the side dome 

 (Oil). This is especially true of the 

 Randsburg material. This habit 

 makes the crystals very hard to orient. Although the basal pinacoid 

 is usually present, this is inclined to the pole. The a (100) pinacoid 

 is the only face developed in the prismatic zone and this is usually 



Fig. 1. 



-Crystal of miargyrite thick 

 tabular on c (001) 



