brongniartite

Brongniartite is a rare mineral composed of bismuth, iron, and sulfur. It has the chemical formula (Bi,Fe)2S3. The mineral is named after Alexandre Brongniart, a French chemist and mineralogist. Brongniartite typically occurs as small, dark gray to black metallic crystals. It is usually found in hydrothermal veins associated with other bismuth-bearing minerals and sometimes with precious metals. Its hardness is relatively low, making it somewhat soft. Brongniartite is not a common ore of bismuth, as more abundant minerals like bismutinite are preferred for extraction. It is primarily of interest to mineral collectors and geologists studying the formation of ore deposits. The mineral was first described in 1974 from occurrences in the Potosi mine in Bolivia. Other locations where brongniartite has been reported include Germany and Canada. Its crystalline structure is monoclinic.