Beudantite

Beudandite is a secondary mineral occurring in the oxidized zones of polymetallic deposits.[3] It is a lead, iron, arsenate, sulfate with endmember formula: PbFe3(OH)6SO4AsO4.

Beudantite
Beudantite-ea12a.jpg
Large brown crystals of Beudantite.
General
CategoryArsenate minerals
Formula
(repeating unit)
PbFe3(OH)6SO4AsO4
Strunz classification8.BL.10
Dana classification43.4.1.1
Crystal systemTrigonal
Crystal classHexagonal scalenohedral (3m)
H-M symbol: (3 2/m)
Space groupR3m
Unit cella = 7.32 Å, c = 17.02 Å; Z = 3
Identification
Colorblack, dark green, brown, yellowish, red, greenish yellow, brown
Crystal habittabular, acute rhombohedral, pseudo-cubic, pseudo-cuboctahedral
Cleavagedistinct; good on {0001}
Mohs scale hardness3.5-4.5
Lustervitreous, resinous
Streakgrayish yellow to green
Diaphaneitytransparent, translucent
Specific gravity4.48
Optical propertiesUniaxial (-)
Refractive indexnω = 1.957 nε = 1.943
Birefringenceδ = 0.014
Pleochroismvisible
Other characteristicsSoluble in HCl
References[1][2][3]

Beudantite is in a subgroup of the alunite group. It is the arsenate analogue of the phosphate corkite. Beudantite also forms a solid-solution with segnitite and plumbojarosite.[1]

It crystallizes in the trigonal crystal system and shows a variety of crystal habits including tabular, acute rhombohedral, pseudo-cubic and pseudo-cuboctahedral.

It occurs in association with carminite, scorodite, mimetite, dussertite, arseniosiderite, pharmacosiderite, olivenite, bayldonite, duftite, anglesite, cerussite and azurite.[3]

DiscoveryEdit

Beudantite was first described in 1826 for an occurrence in the Louise Mine, Wied Iron Spar District, Westerwald, Rhineland-Palatinate, Germany. It was named by Armand Lévy after his fellow Frenchman and mineralogist François Sulpice Beudant (1787–1850).[1]

ReferencesEdit