cooperri

Cooperri is a rare and unique mineral discovered in 2018, named after the American mineralogist William Cooper. It is a copper-arsenic sulfide with the chemical formula Cu5AsS4. Cooperri is typically found in association with other copper and arsenic minerals, such as enargite and orpiment, in hydrothermal veins and low-temperature sedimentary environments.

The mineral exhibits a metallic luster and has a dark gray to black color. Its crystal structure is orthorhombic, and it often forms prismatic crystals or granular aggregates. Cooperri is relatively soft, with a Mohs hardness of 3.5 to 4, and has a specific gravity of approximately 5.2.

Cooperri is of interest to mineralogists and collectors due to its rarity and distinctive appearance. It has been found in only a few locations worldwide, including the type locality in the United States and a few other sites in Europe and Asia. The mineral's formation and occurrence are still subjects of ongoing research, as scientists continue to study its unique properties and the geological processes that lead to its formation.