Tellurium (Te), atomic number 52, is a rare, brittle, silver-white metalloid that exhibits properties of both metals and nonmetals. This classification makes it highly valuable for various modern technologies. It is one of the least abundant elements in the Earth’s crust, rarer than gold and comparable to some platinum group metals. Its distinct properties, particularly its ability to function as a semiconductor, make it indispensable for specialized electronic and energy applications.
Geological Context: How Tellurium Occurs in Nature
Tellurium is seldom found in a pure, native state. When discovered, it is typically bonded with other metals to form compounds called tellurides. These mineral associations involve elements such as gold, silver, copper, and nickel.
The most notable tellurides include calaverite, sylvanite, and petzite, which are historically significant gold-bearing ores. However, the majority of tellurium is thinly dispersed as a trace component within the sulfide ores of more common metals. It is most often concentrated in copper and gold porphyry deposits, establishing a geological link that dictates how the element is ultimately recovered.
Global Production and Major Mining Sources
The global supply of tellurium is almost entirely dependent on the production of other base metals, as it is overwhelmingly recovered as a byproduct. More than 90% of the world’s tellurium is sourced from the anode slimes generated during the electrolytic refining of blister copper. This process is designed to purify copper, and the insoluble impurities settle out in the sludge.
A smaller percentage is recovered from the skimmings produced during the refining of lead, and from the flue dusts collected from the smelting of copper, bismuth, and zinc ores. This byproduct status means the supply of tellurium is economically inelastic, meaning its availability does not increase directly with its own demand but rather with the global production of copper.
The leading global producer of refined tellurium is China, which accounts for an estimated 67% to 75% of the world’s output. However, a significant portion of the tellurium refined in China originates from copper mined and concentrated in other countries. Other major sources are often tied to large copper mining operations in regions like Peru, Russia, Canada, and the United States.
Industrial Applications: Where Tellurium is Used in Products
Tellurium’s unique electronic and thermal properties make it an indispensable component in several high-tech industries, with the largest volume consumed in renewable energy.
The single biggest use is in the manufacturing of Cadmium Telluride (CdTe) thin-film solar panels. When combined with cadmium, tellurium forms a highly efficient semiconductor layer capable of converting sunlight into electricity, often outperforming traditional silicon panels in low-light conditions.
Another major application is in thermoelectric devices, which utilize the compound Bismuth Telluride. These materials are capable of converting a temperature difference directly into an electric current, or conversely, using an electric current to create a temperature difference. This property is used for cooling electronic components, as well as generating power from waste heat in industrial processes and automotive systems.
Tellurium is also a significant alloying agent in metallurgy, used to improve the machinability of various metals. Small additions of tellurium to copper allow it to be cut more easily without reducing its electrical conductivity. Adding it to steel improves the metal’s ability to be machined and enhances chip breakage. It is also alloyed with lead to improve its resistance to fatigue and vibration, utilized in battery grids and cable sheathing.