Gottlobite
Gottlobite, CaMg(VO4,AsO4)(OH), is a mineral found as isolated crystals or isometric grains of orange or orange-brown color. The size of the crystals are a half millimeter in diameter and are part of the orthorhombic crystal system. Gottlobite forms a solid solution with adelite, which is an end member composition of CaMg(VO4)(OH), as well as being classified in the adelite group. Gottlobite is also part of the vanadates and arsenates group. With these characteristics, it is similar to the minerals tangeite and austinite by X-ray diffraction methods.
| Gottlobite | |
|---|---|
| General | |
| Category | Hydroxide mineral, Vanadate mineral, Arsenate mineral |
| Formula (repeating unit) | CaMg(VO4,AsO4)(OH) |
| IMA symbol | Got |
| Strunz classification | 08.BH.35 |
| Dana classification | 41.05.01.10 |
| Crystal system | Orthorhombic |
| Space group | P222 |
| Unit cell | a = 7.501(4) Å; b = 9.010(7) Å; c = 5.941(4) Å; Z = 4, V = 401.5Å3 |
| Identification | |
| Formula mass | 205.20 gm |
| Color | Orange to orange-brown |
| Crystal habit | Isometric to tabular crystals |
| Twinning | Not observed |
| Cleavage | Not observed |
| Fracture | Conchoidal to irregular |
| Tenacity | Brittle |
| Mohs scale hardness | 4.5 |
| Luster | Vitreous to adamantine |
| Streak | Light brownish |
| Diaphaneity | Transparent |
| Specific gravity | 3.46 g/cm3 (calculated) |
| Optical properties | Biaxial negative |
| Refractive index | nα = 1.797 nβ = 1.805-1.815 nγ = 1.828 |
| Pleochroism | Medium strong with X = orange-brown, Y = pale yellowish brown, and Z = orange-brown |
| Group | Vandates and arsenates |
| References | |
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