hausmannite

hausmannite, a manganese oxide mineral (Mn²⁺Mn³⁺₂O₄) that occurs as brownish black crystals or granular masses in high-temperature hydrothermal veins and in contact metamorphic zones. It is found associated with other oxide minerals of manganese and other metals at Ilmenau, Ger.; Långban, Swed.; and Batesville, Ark., U.S. For detailed physical properties, see oxide mineral (table).