It's Elemental

Tellurium was discovered by Franz Joseph Müller von Reichenstein, a Romanian mining official, in 1782. Reichenstein was the chief inspector of all mines, smelters and saltworks in Transylvania. He also had an interest in chemistry and extracted a new metal from an ore of gold, known as aurum album, which he believed was antimony. He shortly realized that the metal he had produced wasn't antimony at all, but a previously unknown element. Reichenstein's work was forgotten until 1798 when Martin Heinrich Klaproth, a German chemist, mentioned the substance in a paper. Klaproth named the new element tellurium but gave full credit for its discovery to Reichenstein. Tellurium is found free in nature, but is most often found in the ores sylvanite (AgAuTe₄), calaverite (AuTe₂) and krennerite (AuTe₂). Today, most tellurium is obtained as a byproduct of mining and refining copper.

Tellurium is a semiconductor and is frequently doped with copper, tin, gold or silver. Tellurium is also used to color glass and ceramics and is one of the primary ingredients in blasting caps.

Tellurium is primarily used as an alloying agent. Small amounts of tellurium are added to copper and stainless steel to make them easier to machine and mill. Tellurium is also added to lead to increase its strength and resistance to sulfuric acid (H₂SO₄).

Tellurium forms many compounds, but none that are commercially important. They include: tellourous acid (H₂TeO₂), tellurium tetrachloride (TeCl₄), tellurium dichloride (TeCl₂), tellurium trioxide (TeO₃), tellurium monoxide (TeO) and sodium telluride (Na₂Te).