Legrandite is a rare zinc arsenate mineral, Zn2(AsO4)(OH)·(H2O).

It is an uncommon secondary mineral in the oxidized zone of arsenic bearing zinc deposits and occurs rarely in granite pegmatite.

Associated minerals include: adamite, paradamite, köttigite, scorodite, smithsonite, leiteite, renierite, pharmacosiderite, aurichalcite, siderite, goethite and pyrite.

[2][3] It has been reported from Tsumeb, Namibia; the Ojuela mine in Durango, Mexico and at Sterling Hill, New Jersey, US.

[2] It was first described in 1934 for an occurrence in the Flor de Peña Mine, Nuevo León, Mexico and named after Louis C.A.