TIIK RARE METALS 285 



slimes or mud where it is left with the gold, silver, etc., in the 

 electrolytic refining of copper. The price per ounce is approxi- 

 mately $2. 



Tellurium 



Properties. Tellurium, symbol Te, is a semi-metallic element, 

 the least abundant of the sulphur group. It is brittle and 

 possesses a metallic luster. The color is tin-white or bluish- 

 while. It is a poor conductor of both heat and electricity.' 

 It burns with a blue flame to Te0 2 , its melting point is 446 

 (\, its hardness is 2.2; its specific gravity is 6.25, and its atomic 

 weight is 127.5. 



Ores of Tellurium. Native tellurium, Te, often with traces 

 of selenium and gold. It occurs in hexagonal crystals, also 

 massive. Selen-tellurium, SeTe, with the ratio of tellurium to 

 selenium nearly that of 2 to 3. Stiitzite, Ag 4 Te, is a telluride of 

 silver with metallic luster, containing 22.5 per cent, of Te and 

 75 . 5 per cent, of Ag. 



Hessite, Ag 2 Te, is another telluride of silver, with 36.7 per 

 cent, of Te and 63 . 3 per cent, of Ag. 



Petzite, (AgAu) 2 Te, is a telluride of both silver and gold. 

 If the ratio of the silver to the gold be 3:1, the analysis would 

 give 32.5 per cent. Te, 42 per cent. Ag, and 25.5 per cent. Au. 



Sylvanite, (AuAg)Te 2 , is a telluride of gold and silver. With 

 a ratio of 1:1, the analysis would give 62. 1 per cent. Te, 24.5 

 per cent. Au, and 13.4 per cent. Ag. 



Krennerite, Ag 2 Te, Au 2 Tes, appears to be an admixture of the 

 tellurides of gold and silver. 



Calaverite, AuTe 2 , is a telluride of gold, although a part of 

 the gold is often displaced by silver. These tellurides appear 

 in the nature of alloys rather than definite compounds, for 

 both tellurium and the tellurides of gold serve as a precipitant 

 for gold. 



Altaite, PbTe, is a telluride of lead, with 37.7 per cent. Te 

 and 62.3 per cent. Pb. 



Coloradoite, HgTe, is a telluride of mercury, with 38 . 5 per cent. 

 Te and 61 .5 per cent. Hg. 



Melonite, Ni 2 Te 3 , is a telluride of nickel, with 76 . 2 per cent. 

 Te, and 23.8 per cent. Ni. 



Rickardite, Cu 4 Te 3 , is the telluride of copper. 



