Tellurium Discovered in 1782, tellurium is a semimetal , sharing properties with metals and nonmetals . In its purest state, tellurium has a metallic luster and is silvery-white in appearance. Tellurium occurs in nature in its elemental state, but more reliable sources include the minerals sylvanite , calaverite , and krennerite . Tellurium is recovered as a by-product of copper ore refining. In many respects it is very similar to its sister elements selenium and sulfur .
Tellurium is used as an alloying agent.
Alloyed with copper and stainless steel, tellurium increases the machinability of those metals. Some are used in the rubber industry and it is also used in the manufacture of blasting caps.