New Mexico Mineral Symposium
November 8-9, 2014
20 Years After: A Brief Update on
the Study of Telluride Minerals & Deposits
B. A. Geller
Colorado School of Mines Geology Museum, 1310 Maple St, Golden, CO, 80401
Much research has been conducted on telluride deposits (those containing the element Te), applying new tools and insights, in the twenty years since the completion of my doctoral studies (Geller, 1993). Te has become a more sought-after commodity, since its application in modern photovoltaic (PV) cells, thermoelectric devices (in military and medical applications), certain memory chips, and guided missiles (George, 2013a). Twenty years ago, Te was only employed in industrial applications, such as metal alloying, rubber vulcanization, and in glass/ceramic pigments, but continues to be used in these industries today (George, 2013b). It is likely that demand for Te will grow, as technology advances, catalyzing better understanding of telluride mineral distribution, exploration for more Te deposits, and improved methods of Te extraction. All Te produced until recently, came as a by-product from processing sulfide ores. Only one deposit in China has recently been mined specifically for its Te.
Although Te remains one of the rarest elements on earth, the IMA has approved 85 unoxidized telluride minerals (those lacking O in their formulae). These are found in diverse geologic environments, generally in the trigonal crystal system. Despite similar chemical behavior with Se, only about 9% of worldwide Te deposits have any reported Se species (Ralph, 2014). Literature reported correlations of tellurides with V minerals are also over-exaggerated and run only at about 6% (Ibid). Nineteen elements have been found to bond with Te in nature, the most common being Bi, S, and Ag. There is no known natural Cd telluride phase. Ralph (2014) reports that the six most typically occurring tellurides on earth (referred to in this talk as ‘the big six’) in order of occurrences are: hessite, tetradymite, altaite, petzite, sylvanite, and calaverite, which strongly corroborates data presented in my dissertation, but not entirely in that order.
Tellurides have been reported on six continents. From data in Ralph (2014), many countries now report tellurides that did not in 1993. China has seen the largest increase in the number of telluride deposits. In 1993, the Boulder Telluride Belt (BTB) in Colorado had the largest diversity of telluride minerals in the geologic literature. Today, eight districts on four continents eclipse the BTB in this distinction (Figure 1).
The countries with the most telluride occurrences as reported by Ralph (2014) are: the United States, China, Canada, and Russia, which correlates well with their overall land size. Colorado had the most telluride occurrences per square kilometer of any region in the U.S. in 1993 (Geller, 1993). Extrapolating from data presented by Ralph (2014), Colorado presently has the most telluride occurrences per square kilometer of any known region in the world, statistically.
In the future, more tellurides will be discovered, from more worldwide occurrences, from type localities and occurrences with extremely diverse telluride mineralogy, but they will remain rare, occur in trace amounts, and probably possess similarities to “typical” telluride chemistry (the predominance of Bi, S, Ag, Pb, Pd, Cu, Au, etc.). The ‘big six’ will continue to dominate world occurrences. This study corroborates the value of mineral databases in mineral research.
- Geller, Bruce Alan, 1993, Mineralogy and origin of telluride deposits in Boulder County, Colorado, Univ. of Colorado at Boulder Ph.D. dissertation, 731 pp.
- George, M.W., 2013a, Mineral resource of the month, Tellurium, Earth Magazine, March 2013, p. 57.
- George, M.W., 2013b, Tellurium, Mineral Commodity Summaries, U.S. Geological Survey, January 2013: http://minerals.usgs.gov/minerals/pubs/commodity/selenium/mcs-2013-tellu.pdf.
- Ralph, J., 2014, Retrieved from http://www.mindat.org/
35th Annual New Mexico Mineral Symposium
November 8-9, 2014, Socorro, NM