Cu3BiS3

Cu3BiS3, also known as wittichenite, is a mineral composed of copper, bismuth, and sulfur. It is a relatively rare copper bismuth sulfide mineral. Wittichenite crystallizes in the orthorhombic crystal system and typically forms granular or massive aggregates. Individual crystals are often small and prismatic. The color of wittichenite ranges from steel-gray to black with a metallic luster. It is a soft mineral, with a Mohs hardness typically around 3.5. The density is approximately 6.7 g/cm³.

Wittichenite is found in hydrothermal ore veins, often associated with other bismuth and copper minerals such as bismutinite, native bismuth, chalcopyrite, and bornite. It is known to occur in various mining districts worldwide, with notable occurrences in Germany (Wittichen), the United States, Canada, and Australia. The mineral was first described in 1867 and named after the Wittichen mine in the Black Forest, Germany, where it was discovered. Its occurrence is generally considered to be of secondary formation, meaning it forms from the alteration of other minerals. While not a primary ore of copper or bismuth, its presence can indicate favorable conditions for mineralization.