See telluride minerals for more information on individual naturally occurring tellurides. Its chemical properties are highly instrumental in distinguishing it from other tellurides. It reacts with many metals to form tellurides. These include natural gold tellurides, like calaverite and krennerite (AuTe), and sylvanite (AgAuTe). It occurs with other tellurides in vein gold deposits. Bilibinskite is a very rare mineral that formed in the weathering zones of gold tellurides. Metal chalcogenide dimers also occur as lower tellurides, such as ZrTe. Reduction of Te metal produces the tellurides and polytellurides, Te. Many metal tellurides are known, including some telluride minerals. Lead tin tellurides have been used in thermoelectric devices. The ore minerals are gold and silver tellurides, with accessory fluorite. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides). Many tellurides can be regarded as metallic alloys. Altaite and other rare tellurides are classified in the sulfide mineral class (Dana classification). Gold usually occurs within tellurides, such as coloradoite, as a high-finess native metal.