Lyonsite
| Lyonsite | |
|---|---|
| General | |
| Category | Vanadate mineral |
| Formula (repeating unit) | Cu3Fe+34(VO4)6 |
| Strunz classification | 8.AB.40 |
| Crystal symmetry |
Orthorhombic dipyramidal H-M symbol: (2/m 2/m 2/m) Space group: Pmcn |
| Unit cell |
a = 10.29 Å, b = 17.2 Å, c = 4.91 Å; Z = 2 |
| Identification | |
| Color | Black; creamy white in reflected light in polished section |
| Crystal habit | As euhedral flattened lath shaped crystals |
| Crystal system | Orthorhombic |
| Cleavage | Good on {001} |
| Tenacity | Brittle |
| Luster | Metallic |
| Streak | Dark gray |
| Diaphaneity | Opaque |
| Specific gravity | 4.215 calculated |
| References | [1][2][3] |
Lyonsite (Cu3Fe+34(VO4)6) is a rare black vanadate mineral that is opaque with a metallic lustre. It crystallizes in the orthorhombic crystal system. Lyonsite often occurs as small tabular typically well formed crystals. Lyonsite has a good cleavage and a dark gray streak.
Lyonsite occurs as a sublimate in volcanic fumaroles. It is often associated with howardevansite and thenardite.[1] It was first described in 1987 for an occurrence on the Izalco volcano, El Salvador. It was named for mineralogist John Bartholomew Lyons of Dartmouth College.[2] It has also been reported from a mine dump in the Lichtenberg Absetzer Mine of Thuringia, Germany.[3]
References
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