PHYSIOGRAPHY. 261 



Vitreous Silver Vivianite. 



Malleable. Hardness = 2-0 . . . 2-5. Sp. gr. = 7-196 

 ...7-366. 



Compound Varieties. Reticulated, arborescent, denti- 

 form, filiform, and capillary shapes : individuals sometimes 

 distinguishable, sometimes impalpable; the dentiform and 

 some other imitative shapes are longitudinally streaked. 

 Massive : composition impalpable; fracture uneven. Plates, 

 and superficial coatings. 



1. It is easily fusible before the blow-pipe, attended by intumescence, 

 and it gives a globule of silver by a continuation of the heat. It is solu- 

 ble in nitric acid. 



2. Analysis. 



By KL.APROTH. By BERZELIUS. 



Silver . . . 85-00 . . . 87-05 



Sulphur . . . 15-00 . . . 12-96 



3. It has been found almost exclusively in veins, accompanied by a 

 great variety of species, particularly by ores of silver, lead, and antimo- 

 ny ; by Blende, several species of Pyrites, and by Calcareous Spar. 

 Rarely, it is found with Native Gold. The rock adjoining the veins is 

 often impregnated with it, and it is itself covered with Silver-black, 

 which sometimes owes its formation to the decomposition of Vitreous 

 Silver. 



4. It occurs at Freiberg, Marienberg, Annaberg, Schneeberg and Jo- 

 hanngeorgenstadt in Saxony; in Bohemia, principally at Joachimsthal; 

 at Schemnitz and Cremnitz in Hungary. Other localities are Siberia, 

 Mexico and Peru. 



5. It is a valuable ore for the extraction of silver. 



VIVIANITE. Prismatic Iron-Mica. 



Primary form. Right oblique-angled prism. M on T 

 = 125 18'. 



