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Category Phosphate mineral
(repeating unit)
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
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 [1][2][3]

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]

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.[3]