Vauquelinite

Formula: Pb₂Cu(CrO₄)(PO₄)(OH)

Origin of name: for Louis N. Vauquelin (1763-1829), French chemist and discoverer of chromium.

Crystal system: Monoclinic

Crystal class: 2/m

Twinning: On {102}

Unit cell: a = 13.68 Å, b = 5.83 Å, c = 9.53 Å, b = 94.0°

Colour: Brown, apple-green, siskin-green, olive-green, canary-yellow, ocher-brown, liver-brown  to brownish green to nearly black

Diaphaneity: Transparent to translucent

Luster: Adamantine to resinous

Habit: Crystals wedge-shaped, minute, irregular aggregates, fibrous, granular, compact, reniform, mammillary

Hardness: 2.5 to 3

Specific gravity: 5.99 to 6.06

Cleavage: None

Tenacity: Brittle, uneven fracture

Streak: Greenish or brown

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