What is franzite?

Franzite is a rare mineral that primarily consists of bismuth and other elements like arsenic and sulfur. It typically occurs in hydrothermal veins associated with bismuth-rich ores. The mineral is named after the Austrian mineralogist Franz Xaver von Kobell, and it is often studied for its unique crystalline structure and potential industrial applications. Due to its rarity, it is of interest primarily to mineral collectors and researchers.