Alunite Mineral Data

Alunite Mineral Data +

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General Alunite Information

Chemical Formula:

KAl3(SO4)2(OH)6

Composition:

Molecular Weight = 414.21 gm

Potassium 9.44 % K 11.37 % K₂O

Aluminum 19.54 % Al 36.92 % Al₂O₃

Hydrogen 1.46 % H 13.05 % H₂O

Sulfur 15.48 % S 38.66 % SO₃

Oxygen 54.08 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

KAl₃(SO₄)₂(OH)₆

Environment:

Rock forming mineral where acid, often ore-bearing, solutions have altered orthoclase feldspar-rich rocks.

IMA Status:

Valid Species (Pre-IMA) 1824

Locality:

Marysvale, Utah. Link to MinDat.org Location Data.

Name Origin:

From the Latin alunit, meaning "alum."

Synonym:

Aluminilite

ICSD 12106

PDF 13-136

Alunite Image

Images:

Alunite

Comments: Octahedral clear to tan tinted crystals of alunite.
Location: Marysvale, Piute County, Utah, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Alunite Crystallography

Axial Ratios:

a:c = 1:2.49354

Cell Dimensions:

a = 6.97, c = 17.38, Z = 4; V = 731.22 Den(Calc)= 3.76

Crystal System:

TrigonalSpace Group: R 3m, R 3m

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 2.89(1), 2.99(1), 2.293(0.8),

Forms:

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Forms: [ 0 1 2] [ 0 0 1]

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Crystal Structure:

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Hendricks S B , American Mineralogist , 22 (1937) p.773-784, The crystal structures of alunite and the jarosites

View Additional jPOWD Structure files for Alunite
[1]

Physical Properties of Alunite

Cleavage:

[0001] Good

Color:

White, Gray, Yellowish gray, Reddish gray, Yellowish white.

Density:

2.59 - 2.9, Average = 2.74

Diaphaniety:

Transparent to translucent

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habit:

Earthy - Dull, clay-like texture with no visible crystalline affinities, (e.g. howlite).

Habit:

Fibrous - Crystals made up of fibers.

Habit:

Massive - Granular - Common texture observed in granite and other igneous rock.

Hardness:

3.5-4 - Copper Penny-Fluorite

Luminescence:

None.

Luster:

Vitreous - Pearly

Streak:

white

Optical Properties of Alunite

Gladstone-Dale:

CI meas= -0.002 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.268 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1548,KPDmeas= 0.212,KC= 0.2115

Optical Data:

Uniaxial (+), w=1.572, e=1.592, bire=0.0200.

Calculated Properties of Alunite

Electron Density:

r_electron=2.76 gm/cc
note: r_Alunite=2.75 gm/cc.

Fermion Index

Fermion Index = 0.00143
Boson Index = 0.99857

Photoelectric:

PE_Alunite= 2.47 barns/electron
U=PE_Alunite x r_electron= 6.80 barns/cc.

Radioactivity:

GRapi = 136.78 (Gamma Ray American Petroleum Institute Units)

Estimated Radioactivity from Alunite - barely detectable

Alunite Classification

Dana Class:

30.2.4.1 (30)Anhydrous Sulfates Containing Hydroxyl or Halogen

(30.2)where (A B)2 XO4 Zq

(30.2.4)Alunite Group (Alunite Subgroup)

30.2.4.1 Alunite KAl3(SO4)2(OH)6 R 3m, R 3m Trig

30.2.4.2 Natroalunite NaAl3(SO4)2(OH)6 R 3m 3 2/m

30.2.4.3 Schlossmacherite (H3O,Ca)Al3(AsO4,SO4)2(OH)6 R 3m 3 2/m

30.2.4.4 Osarizawaite PbCuAl2(SO4)2(OH)6 R 3m 3m

30.2.4.5 Minamiite (Na,Ca,K)Al3(SO4)2(OH)6 R 3m 3 2/m

30.2.4.6 Ammonioalunite (NH4)Al3(SO4)2(OH)6 R 3m 3 2/m

30.2.4.7 Walthierite Ba0.5Al3(SO4)2(OH)6 R 3m 3 2/m

30.2.4.8 Huangite Ca0.5Al3(SO4)2(OH)6 R 3m 3 2/m

Strunz Class:

VI/B.11-20 VI - Sulfates,Chromates,Molybdates and Tungstates

VI/B - Waterfree sulfates [SO4]2- with unfamiliar anions. mostly big cations

VI/B.11 - Alunite group, Natroalunite - Jarosite - Beaverite

VI/B.11-10 Natroalunite NaAl3(SO4)2(OH)6 R 3m 3 2/m

VI/B.11-20 Alunite KAl3(SO4)2(OH)6 R 3m, R 3m Trig

VI/B.11-30 Ammonioalunite (NH4)Al3(SO4)2(OH)6 R 3m 3 2/m

VI/B.11-40 Minamiite (Na,Ca,K)Al3(SO4)2(OH)6 R 3m 3 2/m

VI/B.11-43 Huangite Ca0.5Al3(SO4)2(OH)6 R 3m 3 2/m

VI/B.11-45 Walthierite Ba0.5Al3(SO4)2(OH)6 R 3m 3 2/m

VI/B.11-50 Natrojarosite NaFe3(SO4)2(OH)6 R 3m 3m

VI/B.11-60 Jarosite KFe3(SO4)2(OH)6 R 3 3

VI/B.11-65 Dorallcharite (Tl,K)Fe3(SO4)2(OH)6 R 3m 3 2/m

VI/B.11-70 Ammoniojarosite (NH4)Fe3(SO4)2(OH)6 R 3m 3m

VI/B.11-80 Hydronium-jarosite (H3O)Fe3(SO4)2(OH)6 R 3m 3m

VI/B.11-90 Argentojarosite AgFe3(SO4)2(OH)6 R 3m 3m

VI/B.11-100 Plumbojarosite PbFe6(SO4)4(OH)12 R 3m 3 2/m

VI/B.11-110 Osarizawaite PbCuAl2(SO4)2(OH)6 R 3m 3m

VI/B.11-120 Beaverite PbCu(Fe,Al)2(SO4)2(OH)6 R 3m 3m

Other Alunite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Mason68)

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Alunite

KAl3(SO4)2(OH)6
Dana No: 30.2.4.1 Strunz No: VI/B.11-20
Locality:

Notes: