20 BULLETIN 42, UNITED STATES NATIONAL MUSEUM. 



{'.i) Massive, iu quartz, with a little galena, blende, aqd pyrite. Sheba Mine, Star 

 district, Humboldt County, Nevada. (15591.) 



(4) Massive, intimately mixed with galena, blende, and pyrite. A very<;haracter- 

 istic specimen. Moose Mine, Park County, Colorado. (39411.) 



CERARGYKITE (HORN SILVER.) 



Composition : AgCl. Chloride of silver, contaiuing silver, 75.3 per 

 ceut., and chlorine, 24.7 per cent. 



It crystallizes in the isometric system, especially in cubes, octahe- 

 drons, dodecahedrons, and compounds of these. Its most general occur- 

 rence is massive, especially in crusts and flakes, and as the filling of 

 minute fissures. It varies in hardness from 1 to 1.5, and in specific 

 gravity from 5.31 to 5.55. When jjure and perfectly fresh it is pearl- 

 gray to colorless, but foreign material may give it a variety of tints, 

 and on exposure to light it soon darkens iu color and may become black 

 on the surface. It has a resinous luster and may readily be cut with a 

 knife, whence its name cerargyrite, which is the Greek equivalent of the 

 common name horn silver. 



Cerargyrite is one of the most important of all the silver minerals, 

 and has yielded large amounts of the metal. It is generally the result 

 of the decomposition of other silver minerals, and is therefore most 

 abundant in the upper workiugs of a mine, above the water level. To 

 illustrate the occurrence of cerargyrite seven specimens are shown : 



(1) Imperfect crystals, resulting from the decomposition of ruby silver, iu barite. 

 Horn Silver Mine, Frisco district, Beaver County, Utah. (55337.) 



(2) Crystallized, iu quartz stained by decomposition products. High Bridge Mine, 

 Philadelphia district, Nye County, Nevada. (15726.) 



(3) Massive, with a little barite ; a nearly solid lamp of chloride of silver, weigh- 

 ing 10 iiounds, and worth about $100. Robert E. Lee Mine, Leadville, Lake County, 

 Colorado. (5440.) 



(4) A thin crust on quartz. Eberhardt Mine, Havana district, Madison County, 

 Montana. (10928.) 



(5) A crust on quartz. Meadow Valley Mine, Ely district, Liucolu County, 

 Nevada. (15315.) 



(6) Flakes, in decomposed material. High Bridge Mine, Philadelphia district, Nye 

 County, Nevada. (15713.) 



(7) Flakes, filling fissures iu decomiwsed quartzose material. Barcelona Mine No. 

 1, Spanish Belt district, Nye County, Nevada. (5832.) 



EMBOLITE (MEGABROMITE.) 



Composition : Ag (ClBr). Chloro-bromide of silver, in which the 

 ratio of chloriue to bromine varies greatly, contains, silver 61 to 72 per 

 cent., bromine 8 to 31 per cent., and chlorine 5 to 20 per cent. 



It crystallizes in the isometric system, and occurs also massive and as 

 coatings. It varies in hardness froui 1 to 1.5, and in specific gravity 

 from 5.31 to 5.43 ; is colored various shades of green and yellow ; has 

 an adamantine luster, and darkens on exposure to light. 



Kmbolite freipiently accom[)anies cerargyrite. To illustrate the oc- 

 currence of embolite one specimen is shown : 



(1) Crystalline crust mi chfrt. Robert E. Lee Mine, Leadville, Lake County, Colo- 

 rado. (5442.) 



