68 PHYSIOGRAPHY. 



Black Tellurium. 



5. On account of the large proportion of silver which it contains, it is & 

 valuable ore for the extraction of that metal. 



BLACK TELLURIUM. Prismatic Polypoione- 



Glan c e. 



Primary form. Right square prism. 

 Secondary form. 



Fig. 64. 



x on x 90 00' c. g.) 



x on x f - - 135 00 c. g.f 

 Pona - - 118 35 I PHILLIPS. 



Pone .- 110 00 c. g.J 



Cleavage parallel with P, perfect. * 



Fracture not observable. 



Surface P smooth. 



Lustre metallic. Color blackish lead-grey. Streak un- 

 changed. 



Highly flexible in thin laminae. Very sectile. Hard- 

 ness = 1 -0 ... 1-5. Sp. gr. =7-085. 



Compound varieties. Massive : composition granular, 

 of various sizes of individuals, sometimes longish, 



1. Before the blow-pipe, upon charcoal, it melts easily, emits white 

 fumes, whicji are deposited upon the charcoal, and gives a metallic glob- 

 ule. With borax, it gives a bead of gold containing a little silver. It is 

 easily soluble in nitric acid. 



2. Analysis. 

 By KLAPROTH. 



Tellurium .... 32-20 



Lead 54-00 



Gold .... 9-00 



Silver .... 0-50 



Copper * 1-30 



Sulphur .... 3-00 



