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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.; Langban, Swed.; and Batesville, Ark., U.S. For detailed physical properties, see oxide mineral (table)