Legrandite

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Legrandite
Legrandite, limonite 1100.1.2839.jpg
General
CategoryArsenate minerals
Formula
(repeating unit)
Zn2(AsO4)(OH)·(H2O)
Strunz classification8.DC.10
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/c
Unit cella = 12.805(2), b = 7.933(1)
c = 10.215(2) [Å]; β = 104.23°; Z = 8
Identification
ColorBright yellow, wax-yellow, colorless
Crystal habitCrystalline, prismatic, typically in sprays or sheaflike aggregates
CleavageImperfect, poor one {100}
FractureConchoidal
TenacityBrittle
Mohs scale hardness4.5-5
LusterVitreous
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity3.98–4.01
Optical propertiesBiaxial (+)
Refractive indexnα = 1.675 - 1.702 nβ = 1.690 - 1.709 nγ = 1.735 - 1.740
Birefringenceδ = 0.060
PleochroismX = Y = Colorless to yellow Z = Yellow
2V angleMeasured: 50°
References[1][2][3]

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.[1][2] It has been reported from Tsumeb, Namibia; the Ojuela mine in Durango, Mexico and at Sterling Hill, New Jersey, US.[1]

It was first described in 1934 for an occurrence in the Flor de Peña Mine, Nuevo León, Mexico and named after M. Legrand, a Belgian mining engineer .[2]

References[edit]