116 DESCRIPTIONS OF MINERALS. 



55'o, gold 44-5=100, with a little silver, occurring massive at the Stan- 

 islaus Mine, California, and the Red Cloud Mine, Colorado, and also 



the Keystone and Mountain Lion mines, in the Magnolia District. 



Krtunciite is another gold telluride. 



Syicanite, called also Graphic tdlurium, is a telluride of gold and 

 silver, also containing sometimes antimony and more or less lead < v see 

 p. 118). 



Nagyagite is a telluride of lead containing 9 to 13 per cent, of gold 

 (see p. \a\)). 



Petzite is a telluride of silver, allied to Hessite (p. 118 1 , containing 

 gold ; a specimen from Golden Rule Mine, Colorado, contained 25*60 

 per cent, according to Genth. 



II. SILVER. 



Silver occurs native, and alloyed, or combined with gold ; 

 also combined with sulphur, selenium, tellurium, arsenic, 

 antimony, bismuth, chlorine, bromine, or iodine ; but nevei 

 as an oxide, carbonate, sulphate, or phosphate. 



Native Silver. 



Isometric. In octahedrons and other forms. Xo cleavage 

 apparent. Occurs often in filiform and arborescent shapes, 

 the threads having a crystalline character ; also in laminae, 

 and massive. 



Color and streak silver-white and shining. Often black 

 externally from tarnish. Sectile. Malleable. H. =2*5-3. 

 GL =10-1-11 -1. 



Composition. Native silver is usually an alloy of silver 

 and copper, the latter ingredient often amounting to 10 per 

 cent. It is also alloyed with gold, as mentioned under that 

 metal. A bismuth silver from Copiapo, S. A., contained 16 

 per ceut. of bismuth. 



B.B. fuses easily to a silver-white globule. Dissolves in 

 nitric acid, from which it is precipitated as white chloride 

 on adding hydrochloric acid. A clean plate of copper' im- 

 mersed in the nitric solution becomes coated with silver. 



Diff. Distinguished by being malleable ; from bismuth 

 and other white native metals by affording no fumes before 

 the blowpipe ; by affording a precipitate with hydrochloric 

 acid which becomes black on exposure. 



Obs. Xative silver occurs in masses and string-like ar- 

 borescences, penetrating the gangue, or its minerals, in 



