Hausmannite is a complex oxide of manganese containing both di- and tri-valent manganese. The formula can be represented as Mn2+Mn3+2O4. It belongs to the spinel group and forms tetragonal crystals. Hausmannite is a brown to black metallic mineral with Mohs hardness of 5.5 and a specific gravity of 4.8. The type locality is Oehrenstock (Öhrenstock), Ilmenau, Thuringian Forest, Thuringia, Germany. Locations include Batesville, Arkansas, USA; Ilfeld, Germany; Langban, Sweden; and the Ural Mountains, Russia. The best samples have been found in South Africa and Namibia where it is associated with other manganese oxides, pyrolusite and psilomelane and the iron-manganese mineral bixbyite. Wilhelm Haidinger (1827) named it in honour of Johann Friedrich Ludwig Hausmann (1782–1859), professor of mineralogy, University of Göttingen, Germany.
Crystal structure of hausmannite
Hausmannite from Wessels Mine, Kalahari manganese fields, Northern Cape Province
, South Africa. Size: 5.8 x 4.3 x 3.5 cm.