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Alunite

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Formula:
KAl3(SO4)2(OH)6
System:
Trigonal
Colour:
white, pale shades of ...
Hardness:
3½ - 4
Name:
Named from the Latin for alum.
Alunite Subgroup.

Alunite has been used for dating (K-Ar method) of weathering processes in ore deposits or of the deposition of alunite in caves.

Classification of Alunite

Approved
7.BC.10

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
B : Sulfates (selenates, etc.) with additional anions, without H2O
C : With medium-sized and large cations
30.2.4.1

30 : ANHYDROUS SULFATES CONTAINING HYDROXYL OR HALOGEN
2 : (AB)2(XO4)Zq
25.6.18

25 : Sulphates
6 : Sulphates of Al and Tl
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Type Occurrence of Alunite

Year of Discovery:
1824

Occurrences of Alunite

Geological Setting:
Formed between 15 C and 400 C by the action of sulfate, which may be generated from pyrite or solfataric action, on aluminous rocks, commonly accompanied by kaolinitization and silicification.

Physical Properties of Alunite

Vitreous, Pearly
Diaphaneity (Transparency):
Transparent, Translucent
Comment:
Somewhat pearly on {0001}.
Colour:
white, pale shades of gray, yellow, red, to reddish brown
Comment:
Colorless if pure
Streak:
White
Hardness (Mohs):
3½ - 4
Hardness Data:
Measured
Tenacity:
Brittle
Cleavage:
Distinct/Good
On {0001}, distinct; on {0112}, traces. Handbook of mineralogy: On {0001}, perfect
Fracture:
Irregular/Uneven, Splintery, Conchoidal
Density:
2.6 - 2.9 g/cm3 (Measured)    2.82 g/cm3 (Calculated)
Comment:
Values on massive material.

Crystallography of Alunite

Crystal System:
Trigonal
Class (H-M):
3m - Ditrigonal Pyramidal
Space Group:
R3m
Cell Parameters:
a = 6.98Å, c = 17.32Å
Ratio:
a:c = 1 : 2.481
Unit Cell Volume:
V 730.78 ų (Calculated from Unit Cell)
Morphology:
Rarely in small crystals; as druses in massive material or as aggregates. Crystals tabular {0001} or terminated by flat vicinal rhombohedra; rhombohedral and commonly pseudo-cubic {0112}. Lenticular based on distortion or vicinal development. Massive, granular to dense. As rocky, admixed masses.

Crystallographic forms of Alunite

Crystal Atlas:
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Alunite no.1 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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Edge Lines | Miller Indicies | Axes

Transparency
Opaque | Translucent | Transparent

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Along a-axis | Along b-axis | Along c-axis | Start rotation | Stop rotation

Optical Data of Alunite

Type:
Uniaxial (+)
RI values:
nω = 1.572 nε = 1.592
Max Birefringence:
δ = 0.020
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Moderate

Chemical Properties of Alunite

Formula:
KAl3(SO4)2(OH)6
Essential elements:
All elements listed in formula:
Common Impurities:
Na,Fe

Relationship of Alunite to other Species

Other Members of Group:
Ammonioalunite(NH4)Al3(SO4)2(OH)6
Ammoniojarosite(NH4)Fe33+(SO4)2(OH)6
ArgentojarositeAgFe33+(SO4)2(OH)6
Beaverite-(Cu)Pb(Fe3+,Cu)3(SO4)2(OH)6
Beaverite-(Zn)Pb(Fe23+Zn)(SO4)2(OH)6
DorallchariteTlFe33+(SO4)2(OH)6
HuangiteCa0.5Al3(SO4)2(OH)6
Hydroniumjarosite(H3O)Fe33+(SO4)2(OH)6
JarositeKFe3+ 3(SO4)2(OH)6
NatroaluniteNaAl3(SO4)2(OH)6
Natroalunite-2c(Na,Ca0.5,K)Al3(SO4)2(OH)6
NatrojarositeNaFe3(SO4)2(OH)6
OsarizawaitePb(Al,Cu)3(SO4)2(OH)6
PlumbojarositePb0.5Fe33+(SO4)2(OH)6
Schlossmacherite(H3O)Al3(SO4)2(OH)6
WalthieriteBa0.5Al3(SO4)2(OH)6
7.BC.05D'AnsiteNa21Mg(SO4)10Cl3
7.BC.10Ammonioalunite(NH4)Al3(SO4)2(OH)6
7.BC.10Ammoniojarosite(NH4)Fe33+(SO4)2(OH)6
7.BC.10ArgentojarositeAgFe33+(SO4)2(OH)6
7.BC.10Beaverite-(Cu)Pb(Fe3+,Cu)3(SO4)2(OH)6
7.BC.10DorallchariteTlFe33+(SO4)2(OH)6
7.BC.10HuangiteCa0.5Al3(SO4)2(OH)6
7.BC.10Hydroniumjarosite(H3O)Fe33+(SO4)2(OH)6
7.BC.10JarositeKFe3+ 3(SO4)2(OH)6
7.BC.10Natroalunite-2c(Na,Ca0.5,K)Al3(SO4)2(OH)6
7.BC.10NatroaluniteNaAl3(SO4)2(OH)6
7.BC.10NatrojarositeNaFe3(SO4)2(OH)6
7.BC.10OsarizawaitePb(Al,Cu)3(SO4)2(OH)6
7.BC.10PlumbojarositePb0.5Fe33+(SO4)2(OH)6
7.BC.10Schlossmacherite(H3O)Al3(SO4)2(OH)6
7.BC.10WalthieriteBa0.5Al3(SO4)2(OH)6
7.BC.10Beaverite-(Zn)Pb(Fe23+Zn)(SO4)2(OH)6
7.BC.15Ye'elimiteCa4Al6(SO4)O12
7.BC.20AtlasoviteK(BiO)Cu6Fe3+(SO4)5O3Cl
7.BC.20NabokoiteKCu7(SO4)5(Te4+O3)OCl
7.BC.25ChlorothioniteK2Cu(SO4)Cl2
7.BC.30EuchlorineKNaCu3(SO4)3O
7.BC.30FedotoviteK2Cu3(SO4)3O
7.BC.35KamchatkiteKCu3(SO4)2OCl
7.BC.40PiypiteK2Cu2(SO4)2O
7.BC.45KlyuchevskiteK3Cu3(Fe3+,Al)(SO4)4O2
7.BC.45AlumoklyuchevskiteK3Cu3(Al,Fe3+)(SO4)4O2
7.BC.50CaledonitePb5Cu2(SO4)3(CO3)(OH)6
7.BC.55WherryitePb7Cu2(SO4)4(SiO4)2(OH)2
7.BC.60MammothitePb6Cu4AlSb5+O2(OH)16Cl4(SO4)2
7.BC.65LinaritePbCu(SO4)(OH)2
7.BC.65SchmiederitePb2Cu2(Se6+O4)(Se4+O3)(OH)4
7.BC.65MunakataitePb2Cu2(Se4+O3)(SO4)(OH)4
7.BC.70ChenitePb4Cu(SO4)2(OH)6
7.BC.75KrivovichevitePb3Al(SO4)(OH)7
7.BC.80AnhydrokainiteKMg(SO4)Cl
25.6.1RostiteAl(SO4)(OH) · 5H2O
25.6.2JurbaniteAl(SO4)(OH) · 5H2O
25.6.3KhademiteAl(SO4)F · 5H2O
25.6.4Meta-aluminiteAl2(SO4)(OH)4 · 5H2O
25.6.5AluminiteAl2(SO4)(OH)4 · 7H2O
25.6.6Meta-alunogenAl2(SO4)3 · 12H2O
25.6.7AlunogenAl2(SO4)3 · 17H2O
25.6.8FelsőbányaiteAl4(SO4)(OH)10 · 4H2O
25.6.9Basaluminite
25.6.10HydrobasaluminiteAl4(SO4)(OH)10 · 12-36H2O
25.6.11ZaheriteAl12(SO4)5(OH)26 · 20H2O
25.6.12TamarugiteNaAl(SO4)2 · 6H2O
25.6.13MendoziteNaAl(SO4)2 · 11H2O
25.6.14Alum-(Na)NaAl(SO4)2 · 12H2O
25.6.15NatroaluniteNaAl3(SO4)2(OH)6
25.6.16KaliniteKAl(SO4)2 · 11H2O Not confirmed
25.6.17Alum-(K)KAl(SO4)2 · 12H2O
25.6.19Natroalunite-2c(Na,Ca0.5,K)Al3(SO4)2(OH)6
25.6.20Tschermigite(NH4)Al(SO4)2 · 12H2O

Other Names for Alunite

Other Information

Electrical:
Strongly pyroelectric.
Other Information:
Insoluble in water.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Alunite

Reference List:
Gesner C. (1565) De omni rerum fossilium genere, gemmis, lapidibus, metallis, etc. Tiguri: 13 (as Alumen de Tolpha).

Wallerius, J.G (1747) Mineralogia, eller Mineralriket. Stockholm: 163 (as Romersk Alunsten).

Delamétherie, J.C. (1797) Théorie de la Terre, 2nd. Edition, 5 volumes, Paris: 2: 113 (as Aluminilite).

Haüy, R.J. (1801) Traité de minéralogie. First edition: in 4 volumes with atlas in fol.: 2: 119 (as Alum de Rome).

Jameson, R. (1804) A System of Mineralogy. First edition, 2 volumes, Edinburgh: 1: 319 (as Alumstone).

Cordier (1820) Mém. mus. d'hist. nat.: 6: 204.

Beudant, F.S. (1824), Trailé élémentaire de Minéralogie, Paris: 449.

Mitscherlich (1861) Journal für praktische Chemie, Leipzig: 83: 474 (as Lœwigite).

Jereméjev (1883) Mineralogicheskoe Obshchestvo, Leningrad, Zapiski: 18 [2]: 221.

Flug (1887) Mineralogicheskoe Obshchestvo, Leningrad. Materialien zur Geologie Russlands. Verhandlungen: [2]: 23: 116 (as Ignatiewite).

Michel-Lévy and Lacroix (1888) Les Minéraux des Roches: 140.

Brackett and Williams (1891) American Journal of Science: 42: 11 (as Newtonite).

Calderón y Arana, S. (1910) Los minerales de España, 2 volumes, Madrid: 2: 205 (as Calafatite).

Butler and Gale (1912) USGS Bull. 511.

Schaller (1916) USGS Bull. 610: 150.

Foshag (1926) American Mineralogist: 11: 33.

Doelter, C. (1927) Handbuch der Mineral-chemie (in 4 volumes divided into parts): 4 [2]: 495-497 (as Kalioalunit).

Hintze, Carl (1929) Handbuch der Mineralogie. Berlin and Leipzig. 6 volumes: 1 [3]: 4192.

Laudermilk (1935) American Mineralogist: 20: 57.

Kagaya (1936) Journal of the Japanese Association of Mineralogy, Petrology and Economic Geology: 16: 276.

Hendricks (1937) American Mineralogist: 22: 773.

Kawano (1937) Journal of the Japanese Association of Mineralogy, Petrology and Economic Geology: 17: 31.

Willard and Proctor (1946) Economic Geology: 41: 619.

Pabst, Adolf (1947), Some computations on svanbergite, Woodhouseite and Alunite: Am. Min.: 31: 16-30.

Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.: 556-560.

Acta Crystallographica: 18: 2490-252.

Neues Jahrbuch für Mineralogie, Monatshefte (1976): 406-417.

Sato, E., Nakai, I., Miyawaki, R. & Matsubara, S. (2009): Crystal structures of alunite family minerals: beaverite, corkite, alunite, natroalunite, jarosite, svanbergite, and woodhouseite. Neues Jahrbuch für Mineralogie Abhandlungen 185, 313-322.

Zema, M.; Callegari, A.M.; Tarantino, S.C.; Gasparini, E.; Ghigna, P. (2012): Thermal expansion of alunite up to dehydroxylation and collapse of the crystal structure. Mineralogical Magazine, 76, 613-623.

Internet Links for Alunite

Specimens:
The following Alunite specimens are currently listed for sale on minfind.com.

Localities for Alunite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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