PHYSIOGRAPHY. 269 



Horn Silver. 



Cleavage none. Fracture more or less perfectly con- 

 choidal. Surface of the cube sometimes faintly streaked 

 parallel to the edges of combination with the dodecahedron. 



Lustre resinous, passing into adamantine. Faces of frac- 

 ture often more splendent than those of crystallization. Color 

 pearl-grey, passing on the one hand into lavender-blue and 

 violet blue, on the other, into greyish, yellowish and green- 

 ish white, into sisken-green,. asparagus-green, pistachio- 

 green, and leek-green. The color becomes brown on be- 

 ing exposed to light. Streak shining. Translucent . . . 

 feebly translucent on the edges. 



Sectile. Hardness =1-0 ... 1-5. Sp. gr. = 5-552, a 

 white granular variety from Peru. 



Compound Varieties. In crusts : composition scarcely 

 observable, sometimes columnar. Massive : composition 

 granular, strongly coherent, or imperfectly columnar, and of- 

 ten bent; faces of composition rough. 



1. It is fusible in the flame of a candle, and emits fumes of muriatic 

 acid. Upon charcoal, it may be almost entirely reduced before the 

 blow-pipe, and is 1 likewise easily reduced, if rubbed wet upon a clean sur- 

 face of iron or zinc. It is insoluble in nitric acid or in water. It may 

 be obtained in a crystallized state, either from fusion, or from the evapo- 

 ration of a solution of muriate of silver in ammonia. 



2. Analysis* 

 By KLAPROTH. 



from Saxony. from Peru. 



Silver - - 67-75 - - - 76-0 



Oxygen 4-75 - - - 7-6 



Muriatic acid - - 14-75 - 16-4 % 



Oxide of iron - - 6-00 - - - 0-0 



Alumina - - 1-75 ... 0-0 



Sulphuric acid - - 25 - 0-0 



23* 



