TELLURIUM 



629 



thermal deposits of the telluride ores of Boulder 

 County, Colo., in which gold and silver tellurides are 

 abundant (Kingston, 1966; Kelly and Goddard, 

 1969). 



Sindeeva (1964) observed that tellurium forms 

 its own minerals in many diverse types of ore de- 

 posits. In lead-zinc deposits she reported that tellu- 

 rium concentrates in galena in microscopic segrega- 

 tions of altaite (PbTe) and hessite (AgTe). The 

 tellurium in copper deposits is associated with chal- 

 copyrite and may occur as microscopic segregations 

 of hessite inasmuch as there is more silver in such 

 ore than required to accommodate all of the tellu- 

 rium usually found in the ore (Cooper, 1971, table 

 2-1, p. 15). 



In the zone of active oxidation at or near the 

 surface, tellurium is readily oxidized to tellurites 

 (TeOa"') from tellurides (Te-=) throughout the 

 normal pH range (3-8). At relatively high, but 

 feasible, oxidation potentials, tellurites are oxidized 

 to tellurates (TeOi"^) in alkaline environments (pH 

 6-8.5). This oxidation is verified by minerals con- 

 sisting of ferric tellurite Fe2(Te03)3 and lead, bis- 

 muth, ferrous, and mercurous tellurates. The ready 

 oxidation of tellurides gives rise to the dispersal 

 of tellurium in ground water, from predominantly 

 telluride deposits. 



In acid environments produced by the oxidation 

 of pyrite, tellurium is captured in the iron oxide 

 gossans, presumably as basic ferric tellurites. Gos- 

 sans have been found that contain as much as 1 

 percent tellurium. 



Tellurium is not known to be essential for animal 

 or plant life. It occurs in minute quantities in plants 

 and animals but below concentrations that are 

 readily measured. To illustrate, a limber pine 

 (Pinus flexilus) was found to contain 0.05 ppm 

 tellurium in twigs, 0.012 ppm in bark, and < 0.005 

 ppm in the wood (Hubert, 1971). This tree was col- 

 lected in the Cripple Creek mining district, Colo- 

 rado, where the ore consisted of gold tellurides and 

 where soils are unusually rich in tellurium ; the soil 

 in which it grew contained 0.5 ppm tellurium to a 

 depth of 24 inches and 1 ppm tellurium in the 24- 

 to 30-inch layer. 



No tellurium has been found in phosphate depos- 

 its, Colorado Plateau uranium deposits, sedimentary 

 sulfur, or sedimentary sulfides. Tellurium is found 

 in the fly ash (as much as 0.2 ppm) of the power- 

 plants burning coal. The selenium-tellurium ratio 

 in coal used in certain southwestern U.S. power- 

 plants ranges from 50 to 100. This ratio indicates 

 a depletion of tellurium with respect to selenium. 



Although inadequate analytical methods hamper 



studies of these materials it is easily established 

 that the selenium-tellurium ratio is much larger in 

 organic-rich sedimentary materials than in their 

 assumed crustal abundance. One must conclude that 

 in the weathering processes, tellurium is dispersed 

 and is not reconcentrated again as selenium is in 

 biosinks. 



RESOURCES 



Tellurium is obtained primarily as a byproduct of 

 copper refining ; 80 percent of the production in the 

 United States is derived from the anode mud depos- 

 ited during electrolytic refining of copper. Blister 

 copper contains an average of 0.02 percent tellurium 

 or 0.4 of a pound of tellurium per ton of copper, but 

 actual recovery of tellurium is about 0.17 of a pound 

 per ton of copper. Thus, the production of tellurium 

 in the United States, and in most of the world, is 

 directly related to the production of copper. In-place 

 leaching processes for the recovery of copper do not 

 result in tellurium recovery, and the increasing use 

 of these processes could reduce the supply of tellu- 

 rium materially. Other countries with major po- 

 tential resources of tellurium are those with major 

 potential resources of copper: Chile, U.S.S.R., Zam- 

 bia, Peru, Zaire, Canada, and Mexico (Ageton, 

 1970; see also "Copper" chapter). Substantial 

 amounts of tellurium are recovered from lead ores. 



Resources of tellurium estimated to be potentially 

 available in the identified resources of copper, lead, 

 and coal in the United States and in other countries 

 together with the tellurium available in oceanic man- 

 ganiferous nodules are shown in table 129. 



In electrolytic refining of blister copper about 42 

 percent of the contained tellurium is recovered from 

 the slime residue. Using the ratio of 0.17 of a 

 pound of tellurium per ton of copper produced, we 

 estimate a total of 13.5 million pounds of tellurium 

 available in identified copper resources of the United 

 States, and 43.9 million pounds available in identi- 

 fied copper resources of the rest of the world. 



Refining of lead ores accounts for about 20 per- 

 cent of the present production of tellurium or one- 



Table 129. — Tellurium resources {in thousands of pounds) 

 potentially available in identified resources ' of copper ores, 

 lead ores, coal, and oceanic manganiferous nodules 



Source ' United States Other countries 



Copper ores' 13,500 43,900 



Lead ores 3,000 10,000 



Coal 47,400 237,600 



Oceanic manganiferous nodules. 1,980,000 



^Identified resources: Specific, identified mineral deposits that may or 

 may not be evaluated as to extent and grade, and whose contained min- 

 erals may or may not be profitably recoverable with existing technology 

 and economic conditions. 



^ Identified resources from respective chapters of this volume. 



3 Assuming 42-percent recovery of tellurium. 



