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
General
CategoryVanadate mineral
Formula
(repeating unit)
Cu3Fe+34(VO4)6
IMA symbolLyo[1]
Strunz classification8.AB.40
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPmcn
Unit cella = 10.29, b = 17.2
c = 4.91 [Å]; Z = 2
Identification
ColorBlack; creamy white in reflected light in polished section
Crystal habitAs euhedral flattened lath shaped crystals
CleavageGood on {001}
TenacityBrittle
LusterMetallic
StreakDark gray
DiaphaneityOpaque
Specific gravity4.215 calculated
References[2][3][4]

Lyonsite occurs as a sublimate in volcanic fumaroles. It is often associated with howardevansite and thenardite.[2] 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.[3] It has also been reported from a mine dump in the Lichtenberg Absetzer Mine of Thuringia, Germany.[4]

References


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