Vauquelinite

 Vauquelinite is a complex mineral with the formula CuPb₂(CrO₄)(PO₄)(OH) making it a combined chromate and phosphate of copper and lead. It forms a series with the arsenate mineral fornacite.^[1]

Vauquelinite
Vauquelinite
General
Category	Phosphate mineral
Formula (repeating unit)	CuPb2(CrO4)(PO4)(OH)
Strunz classification	7.FC.05
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/n
Unit cell	a = 13.754(5) Å, b = 5.806(6) Å c = 9.563(3) Å; β = 94.55°; Z = 4
Identification
Color	Olive-green, apple-green, brown to nearly black
Crystal habit	Irregular wedge shaped crystals, mammillary, reniform masses
Twinning	Present on {102}
Cleavage	Indistinct
Fracture	Irregular
Tenacity	Brittle
Mohs scale hardness	2.5 - 3
Luster	Adamantine, resinous
Streak	Greenish or brownish
Diaphaneity	Translucent
Specific gravity	6.16
Optical properties	Biaxial (-)
Refractive index	nα = 2.110 nβ = 2.220 nγ = 2.220
Birefringence	δ = 0.110
Pleochroism	X = Light green, Y = Light brown, Z = Light brown
2V angle	Near zero
References

It was first described in 1818 in the Beryozovskoye deposit, Urals, Russia, and named for Louis Vauquelin (1763–1829), a French chemist.^[1] It occurs in oxidized hydrothermal ore deposits and is associated with crocoite, pyromorphite, mimetite, cerussite, beudantite and duftite at the type locality in Russia.

This article uses material from the Wikipedia article  Metasyntactic variable, which is released under the  Creative Commons Attribution-ShareAlike 3.0 Unported License.