MIARGYRITE SILVER ORE FROM THE RANDSBURG 

 DISTRICT, CALIFORNIA 



By Earl V, Shannon 



Assistant Curator of Geology, United States National Museum 



INTRODUCTION 



Miargyrite, one of the rarest of the sulphantimonites of silver 

 crystallizing in the monoclinic system, has the formula AgaS.SbzSj. 

 It has been found in the United States only in the Flint and Silver 

 City districts in Owyhee County, Idaho, ^ and in the Randsburg 

 district of California.^ In the latter district it has been abundant 

 in the bonanza silver ores lately worked by the California Rand Min- 

 ing Co. Shortly after the discovery of the rich silver ores of these 

 mines an excellent series of specimens was obtained for the National 

 Museum by Frank L. Hess. These specimens form the basis for the 

 following description. 



Although the Randsburg district has been prospected since the 

 sixties and has been an active mining region since 1893, the rich silver 

 ores were not discovered until April 12, 1919.^ The original outcrop 

 of the ore was on the Juanite claim, only about 30 feet from a well- 

 traveled road about 2 miles southeast of the town of Randsburg. The 

 ore at the surface was very rich and all of the material mined was 

 shipped to the smelter, leaving the mine literally without a dump. 

 The specimens received by the United States National Museum are 

 labeled as from the Kelly mine, which is one of the compact group 

 now included in the California Rand properties. 



There are a number of veins belonging to two systems that are 

 rather complex in their relationships. The country rock consists 

 of mica-albite and amphibole schists of pre-Cambrian age. Only 

 two of the numerous silver veins outcropped, and one of these two 

 is too low grade to be worked at a profit. The original discovery 

 was made on the Shaft vein at the only point at which it came to 



1 Earl v. Shannon. The Minerals of Idaho. Bull. U. S. Nat. Mus. 131, pp. 148-150, 1926; Miargyrite 

 and Tetrahedrite from the Flint District, Idaho. Amer. Min., vol. 13, No. 1, pp. 18-21, January, 1928. 



2 Arthur S. Eaklc. Minerals of California. Calif. State Mining Bureau Bull. 91, p. 70, 19^3, and 

 Carlton D. Ilulin. Oeology and Ore Deposits of the Randsburg Quadrangle of California. Calif. State 

 Mining Bureau Bull. 95, 1925. 



3 Hulin. Geology and Ore Deposits of the Randsburg Quadrangle of California, p. 108. 



No. 2766.-PROCEEDINGS U. S. NATIONAL MUSEUM, VOL. 74, ART. 21 



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