Mottramite
| Mottramite | |
|---|---|
| General | |
| Category | Vanadate minerals |
| Formula | PbCu(VO4)(OH) |
| IMA symbol | Mott |
| Strunz classification | 8.BH.40 |
| Dana classification | 41.5.2.2 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Pnma |
| Unit cell | a = 7.68 Å, b = 9.27 Å, c = 6.03 Å; Z = 4 |
| Identification | |
| Formula mass | 402.69 g/mol |
| Colour | Grass-green, olive-green, yellow-green, siskin-green, blackish brown, nearly black |
| Crystal habit | Encrustations, aggregates of plume-like forms and radial crystals |
| Cleavage | None observed |
| Fracture | Irregular/uneven, sub-conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 3 – 3+1⁄2 |
| Lustre | Greasy |
| Streak | Yellowish green |
| Diaphaneity | Transparent, opaque |
| Specific gravity | 5.9 |
| Optical properties | Usually biaxial (−) rarely biaxial (+) |
| Refractive index | nα = 2.170(2) nβ = 2.260(2) nγ = 2.320(2) |
| Birefringence | δ = 0.150 |
| Pleochroism | Visible X=Y= canary yellow to greenish yellow, Z= brownish yellow |
| 2V angle | Measured: 73°, calculated: 46° |
| Dispersion | Strong r > v rarely r < v |
| Solubility | Readily soluble in acids |
| Common impurities | Zinc |
| References | |
Mottramite is an orthorhombic anhydrous vanadate hydroxide mineral, PbCu(VO4)(OH), at the copper end of the descloizite subgroup. It was formerly called cuprodescloizite or psittacinite (this mineral characterized in 1868 by Frederick Augustus Genth). Duhamelite is a calcium- and bismuth-bearing variety of mottramite, typically with acicular habit.
Mottramite is a member of the adelite-descloizite group. Mottramite, which is a copper rich member, forms a series with descloizite, which is a zinc rich member. These two minerals usually contain significant percentages of both copper and zinc and are seldom pure. Mottramite also forms a series with duftite.
It was discovered in 1876 and named for the locality, Mottram St Andrew, Cheshire, England, where ore was stockpiled, although it was probably mined from Pim Hill Mine, Shrewsbury, Shropshire, England.