Hausmannite
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.
| Hausmannite | |
|---|---|
 | |
| General | |
| Category | Oxide mineral |
| Formula (repeating unit) | Mn2+Mn3+2O4 |
| Strunz classification | 4.BB.10 |
| Crystal system | Tetragonal |
| Crystal class | Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) |
| Space group | I41/amd |
| Unit cell | a = 5.76 Å c = 9.46 Å; Z = 4 |
| Identification | |
| Formula mass | 228.81 g/mol |
| Color | Brownish black, grayish. |
| Crystal habit | Massive - granular - common texture observed in granite and other igneous rock. pseudo octahedral - crystals show an octahedral outline. |
| Twinning | Repeated twins on {112} |
| Cleavage | [001] Perfect |
| Fracture | Uneven - flat surfaces (not cleavage) fractured in an uneven pattern. |
| Tenacity | Brittle |
| Mohs scale hardness | 5.5 |
| Luster | Submetallic |
| Streak | Dark reddish brown |
| Diaphaneity | Opaque, transparent on thin edges |
| Specific gravity | 4.7 - 4.84, average = 4.76 |
| Optical properties | Uniaxial (-) |
| Refractive index | nε = 2.15, nω = 2.46 |
| Birefringence | δ = 0.31 |
| Other characteristics | Anisotropism: Distinct, bireflectance: weak; O = light gray; E = dark gray. |
| References | [1][2][3] |
The type locality is Oehrenstock (Öhrenstock), Ilmenau, Thuringian Forest, Thuringia, Germany, where it was first described in 1813.[2] Locations include Batesville, Arkansas, US; Ilfeld, Germany; Langban, Sweden; and the Ural Mountains, Russia.[1] High quality 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.[2]
Image gallery
Hausmannite from Wessels Mine, Kalahari manganese fields, Northern Cape Province, South Africa
Crystal structure of hausmannite
Cluster from Wessels Mine, Hotazel, Kalahari manganese fields, Northern Cape Province, South Africa
Ettringite crystal on a matrix of hausmannite and hematite, coated by oyelite
