| Mottramite | |
|---|---|
| General | |
| Category | Vanadate minerals |
| Chemical formula | PbCu(VO4)(OH) |
| Strunz classification | 08.BH.40 |
| Crystal symmetry | mmm (2/m 2/m 2/m) - Dipyramidal |
| Unit cell | a = 7.68Å, b = 9.27Å, c = 6.03Å |
| Identification | |
| Color | Grass-green, olive-green, yellow-green, siskin-green, blackish brown, nearly black |
| Crystal system | Orthorhombic |
| Cleavage | None observed |
| Fracture | Irregular/uneven, sub-conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 3 - 3½ |
| Luster | Greasy |
| Streak | Yellowish green |
| Diaphaneity | Transparent, opaque |
| Specific gravity | 5.9 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 2.170(2) nβ = 2.260(2) nγ = 2.320(2) |
| Birefringence | δ = 0.150 |
| Pleochroism | Visible |
| 2V angle | Measured: 73° , Calculated: 46° |
| Dispersion | strong r > v rarely r < v |
Mottramite is an orthorhombic mineral, PbCu(VO4)(OH), at the copper end of the descloizite group. It was formerly called cuprodescloizite or psittacinite (this mineral characterized in 1868 by Frederick Augustus Genth).