Lyonsite

Lyonsite (Cu₃Fe⁺³₄(VO₄)₆) is a black vanadate mineral that is opaque with a metalic lustre. It crystallizes in the orthorhombic crystal system. Lyonsite often occurs as small tabular typically well formed crystals with good external form. Lyonsite has a good cleavage and a dark gray streak.

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Lyonsite occurs in volcano crater fumarole. It is often associated with howardevansite and thenardite. It was first described in 1987 for an occurrence on the Izalco volcano, El Salvador (Pacific area of Central America). It was named for mineralogist John Bartholomew Lyones of Dartmouth College.

References

• Mineral Handbook
• Webmineral
• Mindat