bismuthinite

Bismuthinite is a sulfide mineral with the formula Bi2S3. It is the principal ore of bismuth and a common bismuth sulfide in hydrothermal ore deposits. The mineral crystallizes in the orthorhombic system and is most often found as slender, prismatic or needle-like crystals, though it also occurs in fibrous aggregates or massive grains.

Physical properties include a metallic luster and a lead-gray to steel-gray color; it is opaque with a gray streak. Bismuthinite is relatively soft, with a Mohs hardness around 2.0–2.5, and has a high specific gravity about 7.6–7.8. It is brittle and typically shows a conchoidal to uneven fracture.

Formation and occurrence: Bismuthinite forms in hydrothermal veins and replacement deposits where sulfur-bearing fluids interact with bismuth-bearing minerals. It is commonly associated with quartz, calcite, sphalerite, galena, pyrite, and other sulfides, and may appear as acicular crystals or as masses.

Geographic distribution: The mineral is found in ore deposits worldwide, reflecting its formation in hydrothermal systems. It is typically mined as part of bismuth-bearing ore concentrates rather than as a stand-alone large crystal.

Uses and significance: Bismuthinite serves as the primary source of bismuth metal, which is extracted through processing of the ore. Bismuth has applications in metallurgy, cosmetics, pharmaceuticals, and various industrial alloys. In mineral collecting, bismuthinite is valued for its metallic luster and, when present, its slender, needle-like crystals.