Altaite

Altaite is a rare lead telluride mineral with the chemical formula PbTe. It forms in hydrothermal ore veins as small grains and, less commonly, as well-formed crystals.

Crystallography and properties: Altaite crystallizes in the cubic isometric system with a rock-salt-type structure. It has a metallic luster and a lead-gray to steel-gray color; the streak is gray. On the Mohs scale, its hardness is about 2 to 3. It is opaque and has a relatively high specific gravity, typically around 7.2–7.8 g/cm3. The mineral commonly shows conchoidal to uneven fracture.

Occurrence and associations: Altaite occurs in telluride-rich hydrothermal ore deposits and is usually found with other tellurides such as calaverite (AuTe2), krennerite, and sylvanite, as well as with sulfides such as galena and sphalerite. It is often part of assemblages that reflect telluride-rich environments and may occur with native tellurium.

Significance: Altaite is primarily of interest to mineral collectors and researchers studying telluride minerals and solid-state chemistry. It is not a practical source of lead or tellurium due to its rarity. The mineral is one of several natural PbTe phases; while PbTe itself is used in thermoelectric materials, natural altaite is not exploited for such purposes.