| Beudantite | |
| Category: | Arsenate minerals |
| Formula: | PbFe3(OH)6SO4AsO4 |
| Imasymbol: | Bdn[1] |
| Strunz: | 8.BL.10 |
| Dana: | 43.4.1.1 |
| System: | Trigonal |
| Class: | Hexagonal scalenohedral (m) H-M symbol: (2/m) |
| Symmetry: | Rm |
| Unit Cell: | a = 7.32 Å, c = 17.02 Å; Z = 3 |
| Color: | black, dark green, brown, yellowish, red, greenish yellow, brown |
| Habit: | tabular, acute rhombohedral, pseudo-cubic, pseudo-cuboctahedral |
| Cleavage: | distinct; good on |
| Mohs: | 3.5–4.5 |
| Luster: | vitreous, resinous |
| Refractive: | nω = 1.957 nε = 1.943 |
| Opticalprop: | Uniaxial (−) |
| Birefringence: | δ = 0.014 |
| Pleochroism: | visible |
| Streak: | grayish yellow to green |
| Gravity: | 4.48 |
| Diaphaneity: | transparent, translucent |
| Other: | Soluble in HCl |
| References: | [2] [3] [4] |
Beudandite is a secondary mineral occurring in the oxidized zones of polymetallic deposits.[4] 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.[2]
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.[4]
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).[2]