PHYSIOGRAPHY. CLASS II. 



Compound Varieties. Reticulated, arborescent, 

 dentiform, filiform, and capillary shapes : indivi- 

 duals sometimes distinguishable, sometimes impalp- 

 able ; the dentiform and some other imitative shapes 

 are longitudinally streaked. Massive : composi- 

 tion impalpable ; fracture uneven. Plates, and 

 superficial coatings. 



OBSERVATIONS. 



1. According to KLAPROTH, the hexahedral Silver-glance 

 is composed of 



Silver 85-00. 



Sulphur 15-00. 



It is Ag S 2 , according to BERZELIUS, which would make 

 the proportion = 87'05 : 12-96. It is easily fusible before 

 the blowpipe, and intumesces, but it gives a globule of sil- 

 ver by a continuation of the blast. It is soluble in dilute 

 nitric acid. 



2. It has been hitherto found almost exclusively in veins, 

 accompanied by a great variety of species, particularly 

 ores of silver, lead, and antimony, dodecahedral Garnet- 

 blende, several species of the order Pyrites and of the genus 

 Lime-haloide. Sometimes, though rarely, it is found along 

 with hexahedral Gold. The rock adjoining the veins is often 

 impregnated with it, and it is itself often covered with 

 Silver-black, which sometimes owes its formation to the 

 decomposition of hexahedral Silver-glance. 



3. There are but few localities where the present species 

 is found in any considerable quantity. It occurs at Frei- 

 berg, Marienberg, Annaberg, Schneeberg, Johanngeorgen- 

 stadt in Saxony ; in Bohemia, principally at Joachimsthal ; 

 at Schemnitz and Cremnitz in Hungary, where it is 

 called Weichge-w'dchs ; in the Koliwan mountains in Siberia, 

 in Mexico and Peru. It has been found in smaller quan- 

 tities, both massive and crystallised, in several mines of 

 Cornwall, in the Hartz, in Norway, in Dauphiny, &c. 



