beudantite

{{Short description|Secondary mineral of the alunite group}}

{{Infobox mineral

| name = Beudantite

| category = Arsenate minerals

| image = Beudantite-ea12a.jpg

| imagesize = 170px

| alt =

| caption = Large brown crystals of beudantite

| formula = PbFe₃(OH)₆SO₄AsO₄

| IMAsymbol=Bdn{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|url=https://www.cambridge.org/core/journals/mineralogical-magazine/article/imacnmnc-approved-mineral-symbols/62311F45ED37831D78603C6E6B25EE0A|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}

| molweight =

| strunz = 8.BL.10

| dana = 43.4.1.1

| system = Trigonal

| class = Hexagonal scalenohedral ({{overline|3}}m)
H-M symbol: ({{overline|3}} 2/m)

| symmetry = R{{overline|3}}m

| 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

| twinning =

| cleavage = distinct; good on {0001}

| fracture =

| tenacity =

| mohs = 3.5–4.5

| luster = vitreous, resinous

| refractive = n_ω = 1.957 n_ε = 1.943

| opticalprop = Uniaxial (−)

| birefringence = δ = 0.014

| pleochroism = visible

| 2V =

| dispersion =

| streak = grayish yellow to green

| gravity = 4.48

| density =

| melt =

| fusibility =

| diagnostic =

| solubility =

| diaphaneity = transparent, translucent

| other = Soluble in HCl

|references = [http://www.mindat.org/min-652.html Mindat.org][http://webmineral.com/data/Beudantite.shtml Web Mineral data][http://rruff.geo.arizona.edu/doclib/hom/beudantite.pdf Handbook of Mineralogy]

}}

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.