Lyonsite
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 | |
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General | |
Category | Vanadate mineral |
Formula (repeating unit) | Cu3Fe+34(VO4)6 |
Strunz classification | 8.AB.40 |
Crystal system | Orthorhombic |
Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
Space group | Pmcn |
Unit cell | a = 10.29, b = 17.2 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 |
Cleavage | Good on {001} |
Tenacity | Brittle |
Luster | Metallic |
Streak | Dark gray |
Diaphaneity | Opaque |
Specific gravity | 4.215 calculated |
References | [1][2][3] |
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 (1916–1998) of Dartmouth College.[2] It has also been reported from a mine dump in the Lichtenberg Absetzer Mine of Thuringia, Germany.[3]
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