Beudantite
| Beudantite | |
|---|---|
Large brown crystals of Beudantite.
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| General | |
| Category | Arsenate minerals |
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Formula (repeating unit) |
PbFe3(OH)6SO4AsO4 |
| Strunz classification | 8.BL.10 |
| Dana classification | 43.4.1.1 |
| Crystal system | Trigonal |
| Crystal class | Hexagonal scalenohedral (3m) H-M symbol: (3 2/m) |
| Space group | R3m |
| Unit cell | a = 7.32 Å, c = 17.02 Å; Z = 3 |
| Identification | |
| Color | black, dark green, brown, yellowish, red, greenish yellow, brown |
| Crystal habit | tabular, acute rhombohedral, pseudo-cubic, pseudo-cuboctahedral |
| Cleavage | distinct; good on {0001} |
| Mohs scale hardness | 3.5-4.5 |
| Luster | vitreous, resinous |
| Streak | grayish yellow to green |
| Diaphaneity | transparent, translucent |
| Specific gravity | 4.48 |
| Optical properties | Uniaxial (-) |
| Refractive index | nω = 1.957 nε = 1.943 |
| Birefringence | δ = 0.014 |
| Pleochroism | visible |
| Other characteristics | Soluble in HCl |
| References | |
Beudandite is a secondary mineral occurring in the oxidized zones of polymetallic deposits. It is a lead, iron, arsenate, sulfate with endmember formula: PbFe3(OH)6SO4AsO4.
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.
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.
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).
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