76 PHYSIOGRAPHY. 



Native Silver Native Tellurium. 



in the same repositories, is far more scarce. The formation of Black 

 Silver, a black, friable substance, which is very rich in silver, seems to 

 depend chiefly upon the presence of Native Silver. 



5. Native Silver is found in the mining districts of Saxony and Bohe- 

 mia, also in Norway and Siberia, but particularly in Mexico and Peru. 

 Native Silver is also found in Cornwall and in Siberia. No well authen- 

 ticated localit}' exists in the U. States. 



6. The employment of silver in coinage, and in the manufacture of 

 plate and articles of luxury, is well known. 



NATIVE TELLURIUM. Tellurium Melacone- 

 Metal. 



Primary form. Rhomboid. P on P=l 15 12'. 



Secondary form. Hexagonal prism, with the terminal 

 edges replaced by single planes, the secondary planes in- 

 clining to the lateral faces at 147 36'. 



Cleavage, parallel with the. primary form, but very ob- 

 scure. 



Lustre metallic. Color tin-white. Streak unchanged. 



Rather brittle. Hardness = 2-0 . . . 2-5. Sp. gr. = 

 6*115. KLAPROTH. 



Compound Varieties. Massive : composition distinctly 

 granular, individuals small ; sometimes a tendency to co- 

 lumnar composition. 



1. It melts upon charcoal with ease before the blow-pipe, burning 

 with a greenish flame, and emitting the odor of horse-radish, which how- 

 ever is owing to the presence of a small quantity of selenium. 



2. Analysis. 

 By KLAPROTH. 



Tellurium - - - - 92-55 



Iron 7-00 



Gold ..... 0-25 



3. The Native Tellurium 6ccurs in sandstone, probably in beds, or in 

 veins of a contemporaneous origin with the rock. It is accompanied by 

 Quartz and Iron Pyrites, as well as by Native Gold. 



