This volume describes oxidic Mn minerals of the type M2O3 (bixbyite, pyrophanite, melanostibite, landauite, and zenzenite). Crystallographic data, physical properties, and the chemical and thermal behavior are discussed with special emphasis placed on the various aspects of occurrence and genesis, and their influence on the chemical composition of the minerals. Minerals which contain Mn as a minor constituent (minimum concentration: > 1 %) are briefly summarized.