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Legrandite

Legrandite
Yellow radiating prismatic crystals on limonite
General
Category	Mineral
Chemical formula	Zn₂(As O₄)(O H)·(H₂O)
Identification
Color	Yellow or yellowish orange to colourless
Crystal habit	Crystalline, prismatic
Crystal system	Monoclinic
Cleavage	Imperfect, poor in one direction
Fracture	Brittle, conchoidal
Mohs Scale hardness	4.5-5
Refractive index	1.675-1.74
Streak	White
Specific gravity	4.0

Legrandite is a rare arsenate mineral, discovered in 1934 and named after the Belgian mining engineer Legrand. Chemically, it is a hydrated zinc arsenate hydroxide, found as a secondary mineral in zinc ores, often in association with limonite. The most notable source of the mineral is the now abandoned Ojuela mine in Durango, Mexico. It is highly praised for its vitreous rich yellow colour and is a desirable item among mineral collectors.