crystals of legrandite, crystals of limonite : Ojuela Mine, Mapimi, Mun. de Mapimi, Durango, Mexico — Photo: Parent Géry · CC BY-SA 3.0
Legrandite
A rare bright-yellow zinc arsenate of the oxidized zone — among the most coveted collector's minerals of Mexico.
Intro adapted from Wikipedia (CC BY-SA).
Legrandite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Zn₂(AsO₄)(OH)·H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/c).
Key properties: Mohs hardness 4.5; specific gravity 3.98–4.01; typically yellow; white streak; Vitreous luster; refractive index 1.709; optically biaxial.
IMA symbol Leg, grandfathered status — known before the IMA’s founding, named in 1932.
Occurs as an uncommon secondary mineral in the oxidized zone of Zn–As-bearing deposits; rare in granite pegmatite.
It is found associated with Adamite, paradamite, köttigite, scorodite, smithsonite (Ojuela mine, Mexico); leiteite, smithsonite, reniérite (Tsumeb, Namibia); köttigite, adamite.
The mineral was named to honor a Mr. Legrand, Belgian mine manager, who collected the first specimen.
Collections: Collector Favorites, Rare & Remarkable.