Matlockite
Matlockite is a rare lead halide mineral, named after the town of Matlock in Derbyshire, England, where it was first discovered in a nearby mine. Matlockite (chemical formula: PbFCl) gives its name to the matlockite group which consists of rare minerals of a similar structure.
| Matlockite | |
|---|---|
| General | |
| Category | Halide minerals |
| Formula (repeating unit) | PbFCl |
| IMA symbol | Mtl |
| Strunz classification | 3.DC.25 |
| Dana classification | 9.2.11.1 |
| Crystal system | Tetragonal |
| Crystal class | Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) |
| Space group | P4/nmm |
| Unit cell | a = 4.11 Å, c = 7.23 Å; Z = 2 |
| Identification | |
| Colour | Colourless to yellow and greenish |
| Crystal habit | Flattened, tabular crystals occurring as aggregates, rosettelike, radiating, hemispherical; also massive |
| Cleavage | {001}, perfect |
| Fracture | Uneven to subconchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 2.5 – 3 |
| Luster | Adamantine, pearly on {001} |
| Diaphaneity | Transparent |
| Specific gravity | 7.1 – 7.2 |
| Optical properties | Uniaxial (−) |
| Refractive index | nω = 2.150 nε = 2.040 |
| References | |
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