| Legrandite | |
| Category: | Arsenate minerals |
| Formula: | Zn2(AsO4)(OH)·(H2O) |
| Imasymbol: | Leg[1] |
| Strunz: | 8.DC.10 |
| System: | Monoclinic |
| Class: | Prismatic (2/m) (same H-M symbol) |
| Symmetry: | P21/c |
| Unit Cell: | a = 12.805(2), b = 7.933(1) c = 10.215(2) [Å]; β = 104.23°; Z = 8 |
| Color: | Bright yellow, wax-yellow, colorless |
| Habit: | Crystalline, prismatic, typically in sprays or sheaflike aggregates |
| Cleavage: | Imperfect, poor one |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Mohs: | 4.5–5 |
| Luster: | Vitreous |
| Refractive: | nα = 1.675 – 1.702 nβ = 1.690 – 1.709 nγ = 1.735 – 1.740 |
| Opticalprop: | Biaxial (+) |
| Birefringence: | δ = 0.060 |
| Pleochroism: | X = Y = Colorless to yellow Z = Yellow |
| 2V: | Measured: 50° |
| Streak: | White |
| Gravity: | 3.98–4.01 |
| Diaphaneity: | Transparent to translucent |
| References: | [2] [3] [4] |
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. Legrand, a Belgian mining engineer.[3]