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Alunite

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Formula:
KAl
 
3
(SO
 
4
)
 
2
(OH)
 
6
System:TrigonalColour:white, pale shades of ...
Hardness:3½ - 4
Member of:Alunite Group > Alunite Supergroup
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

IMA status:Approved
Strunz 8th edition ID:6/B.11-20
Nickel-Strunz 10th (pending) edition ID: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
Dana 8th edition ID:30.2.4.1

30 : ANHYDROUS SULFATES CONTAINING HYDROXYL OR HALOGEN
2 : (AB)2(XO4)Zq
Hey's CIM Ref.:25.6.18

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

Type Locality:Allumiere Quarries, Allumiere, Tolfa Mts District, Rome Province, Latium, Italy
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

Lustre: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 (measured):2.6 - 2.9 g/cm3
Density (calculated):2.82 g/cm3
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.

Crystal Atlas:
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Alunite no.1 - Goldschmidt (1913-1926)

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The mindat.org Crystal Atlas allows you to view a selection of crystal drawings of real and idealised crystal forms for this mineral and, in certain cases, 3d rotating crystal objects. The 3d models and HTML5 code are kindly provided by www.smorf.nl.

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Optical Data of Alunite

Type:Uniaxial (+)
RI values: nω = 1.572 nε = 1.592
Maximum Birefringence:δ = 0.020

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Moderate

Chemical Properties of Alunite

Formula:
KAl
 
3
(SO
 
4
)
 
2
(OH)
 
6
Simplified for copy/paste:KAl3(SO4)2(OH)6
Essential elements:Al, H, K, O, S
All elements listed in formula:Al, H, K, O, S
Common Impurities:Na,Fe

Relationship of Alunite to other Species

Member of:Alunite Group > Alunite Supergroup
Other Members of Group:

- +
Ammonioalunite
(NH
 
4
)Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
Ammoniojarosite
(NH
 
4
)Fe
3+
3
(SO
 
4
)
 
2
(OH)
 
6
Argentojarosite
AgFe
3+
3
(SO
 
4
)
 
2
(OH)
 
6
Beaverite-(Cu)
Pb(Fe
3+
 
,Cu)
 
3
(SO
 
4
)
 
2
(OH)
 
6
Beaverite-(Zn)
Pb(Fe
3+
2
Zn)(SO
 
4
)
 
2
(OH)
 
6
Dorallcharite
(Tl,K)Fe
3+
3
(SO
 
4
)
 
2
(OH)
 
6
Huangite
Ca
 
0.5
Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
Hydroniumjarosite
(H
 
3
O)Fe
3+
3
(SO
 
4
)
 
2
(OH)
 
6
Jarosite
KFe
3+
 
 
3
(SO
 
4
)
 
2
(OH)
 
6
Natroalunite
(Na,K)Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
Natroalunite-2c
(Na,Ca
 
0.5
,K)Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
Natrojarosite
NaFe
 
3
(SO
 
4
)
 
2
(OH)
 
6
Osarizawaite
Pb(Al,Cu)
 
3
(SO
 
4
)
 
2
(OH)
 
6
Plumbojarosite
Pb
 
0.5
Fe
3+
3
(SO
 
4
)
 
2
(OH)
 
6
Schlossmacherite
(H
 
3
O)Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
Walthierite
Ba
 
0.5
Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
Common Associates:
QuartzPyriteKaoliniteHalloysiteGypsum
Diaspore
Related Minerals - Nickel-Strunz Grouping):

- +
7.BC.05D'Ansite
Na
 
21
Mg(SO
 
4
)
 
10
Cl
 
3
7.BC.10Ammonioalunite
(NH
 
4
)Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Ammoniojarosite
(NH
 
4
)Fe
3+
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Argentojarosite
AgFe
3+
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Beaverite-(Cu)
Pb(Fe
3+
 
,Cu)
 
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Dorallcharite
(Tl,K)Fe
3+
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Huangite
Ca
 
0.5
Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Hydroniumjarosite
(H
 
3
O)Fe
3+
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Jarosite
KFe
3+
 
 
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Natroalunite-2c
(Na,Ca
 
0.5
,K)Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Natroalunite
(Na,K)Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Natrojarosite
NaFe
 
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Osarizawaite
Pb(Al,Cu)
 
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Plumbojarosite
Pb
 
0.5
Fe
3+
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Schlossmacherite
(H
 
3
O)Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Walthierite
Ba
 
0.5
Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
7.BC.10Beaverite-(Zn)
Pb(Fe
3+
2
Zn)(SO
 
4
)
 
2
(OH)
 
6
7.BC.15Ye'elimite
Ca
 
4
Al
 
6
(SO
 
4
)O
 
12
7.BC.20Atlasovite
K(BiO)Cu
 
6
Fe
3+
 
(SO
 
4
)
 
5
O
 
3
Cl
7.BC.20Nabokoite
KCu
 
7
(SO
 
4
)
 
5
(Te
4+
 
O
 
3
)OCl
7.BC.25Chlorothionite
K
 
2
Cu(SO
 
4
)Cl
 
2
7.BC.30Euchlorine
KNaCu
 
3
(SO
 
4
)
 
3
O
7.BC.30Fedotovite
K
 
2
Cu
 
3
(SO
 
4
)
 
3
O
7.BC.35Kamchatkite
KCu
 
3
(SO
 
4
)
 
2
OCl
7.BC.40Piypite
K
 
2
Cu
 
2
(SO
 
4
)
 
2
O
7.BC.45Klyuchevskite
K
 
3
Cu
 
3
(Fe
3+
 
,Al)(SO
 
4
)
 
4
O
 
2
7.BC.45Alumoklyuchevskite
K
 
3
Cu
 
3
(Al,Fe
3+
 
)(SO
 
4
)
 
4
O
 
2
7.BC.50Caledonite
Pb
 
5
Cu
 
2
(SO
 
4
)
 
3
(CO
 
3
)(OH)
 
6
7.BC.55Wherryite
Pb
 
7
Cu
 
2
(SO
 
4
)
 
4
(SiO
 
4
)
 
2
(OH)
 
2
7.BC.60Mammothite
Pb
 
6
Cu
 
4
AlSb
5+
 
O
 
2
(OH)
 
16
Cl
 
4
(SO
 
4
)
 
2
7.BC.65Linarite
PbCu(SO
 
4
)(OH)
 
2
7.BC.65Schmiederite
Pb
 
2
Cu
 
2
(Se
6+
 
O
 
4
)(Se
4+
 
O
 
3
)(OH)
 
4
7.BC.65Munakataite
Pb
 
2
Cu
 
2
(Se
4+
 
O
 
3
)(SO
 
4
)(OH)
 
4
7.BC.70Chenite
Pb
 
4
Cu(SO
 
4
)
 
2
(OH)
 
6
7.BC.75Krivovichevite
Pb
 
3
Al(SO
 
4
)(OH)
 
7
7.BC.80Anhydrokainite
KMg(SO
 
4
)Cl
Related Minerals - Hey's Index Grouping:

- +
25.6.1Rostite
Al(SO
 
4
)(OH) · 5H
 
2
O
25.6.2Jurbanite
Al(SO
 
4
)(OH) · 5H
 
2
O
25.6.3Khademite
Al(SO
 
4
)F · 5H
 
2
O
25.6.4Meta-aluminite
Al
 
2
(SO
 
4
)(OH)
 
4
· 5H
 
2
O
25.6.5Aluminite
Al
 
2
(SO
 
4
)(OH)
 
4
· 7H
 
2
O
25.6.6Meta-alunogen
Al
 
2
(SO
 
4
)
 
3
· 12H
 
2
O
25.6.7Alunogen
Al
 
2
(SO
 
4
)
 
3
· 17H
 
2
O
25.6.8Felsőbányaite
Al
 
4
(SO
 
4
)(OH)
 
10
· 4H
 
2
O
25.6.9Basaluminite
25.6.10Hydrobasaluminite
Al
 
4
(SO
 
4
)(OH)
 
10
· 12-36H
 
2
O
25.6.11Zaherite
Al
 
12
(SO
 
4
)
 
5
(OH)
 
26
· 20H
 
2
O
25.6.12Tamarugite
NaAl(SO
 
4
)
 
2
· 6H
 
2
O
25.6.13Mendozite
NaAl(SO
 
4
)
 
2
· 11H
 
2
O
25.6.14Alum-(Na)
NaAl(SO
 
4
)
 
2
· 12H
 
2
O
25.6.15Natroalunite
(Na,K)Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
25.6.16Kalinite
KAl(SO
 
4
)
 
2
· 11H
 
2
O Not confirmed
25.6.17Alum-(K)
KAl(SO
 
4
)
 
2
· 12H
 
2
O
25.6.19Natroalunite-2c
(Na,Ca
 
0.5
,K)Al
 
3
(SO
 
4
)
 
2
(OH)
 
6
25.6.20Tschermigite
(NH
 
4
)Al(SO
 
4
)
 
2
· 12H
 
2
O

Other Names for Alunite

Synonyms:
AluminiliteAlumstoneCalafatiteIgnatiewiteKalioalunite
K-AluniteLœvigiteLœwigiteLowigite
Other Languages:
French:Alum de Rome
Pierre alumineuse de la Tolfa
German:Alaun-Grammit
Alaunspat
Alaunstein (of Werner)
Aluminilit
Alunit
Kalioalunit
K-Alunit
Lœvigit
Lœwigit
Lowigit
Latin:Alumen de Tolpha
Russian:Алунит
Simplified Chinese:明矾石
Spanish:Aluminilita
Alunita
Kalioalunita
Lœvigita
Lœwigita
Lowigita
Swedish:Romersk Alunsten

Other Information

Electrical:Strongly pyroelectric.
Other Information:Insoluble in water.
Health Warning: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

Search Engines:
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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Alunite details from Handbook of Mineralogy (PDF)
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    Localities for Alunite

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