calaverite

Calaverite is a mineral consisting of gold telluride with the chemical formula AuTe2. It is one of the principal telluride minerals associated with gold deposits and can constitute a direct source of gold in hydrothermal ore bodies. The name is derived from the Calaveras district in California, where the mineral was first described.

Calaverite forms in hydrothermal vein systems and in replacement zones within metamorphic rocks. It commonly occurs in association with other telluride minerals and native gold, including sylvanite (a silver-gold telluride) and other gold tellurides. It is typically found as coarse-grained, metallic masses or small prismatic crystals, though well-formed crystals are not common.

In hand specimen, calaverite has a metallic luster and a brass-yellow to pale brass color, often appearing tarnished. It is opaque, with a yellow to brownish streak. The mineral is relatively soft, with a Mohs hardness around 3, and possesses a very high specific gravity, usually on the order of eight to nine. It is brittle and tends to fracture rather than cleave.

Economically, calaverite is valued as an ore of gold. Processing of telluride-bearing ores can be more complex than simple gold ores, sometimes requiring roasting to liberate tellurium and specialized leaching steps to recover gold efficiently. Calaverite remains of interest to mineral collectors due to its metallic appearance and association with hydrothermal gold systems.