Alunogen

Al2 (SO4 )3 • 17H2 O
c 2001-2005 Mineral Data Publishing, version 1

Crystal Data: Triclinic. Point Group: 1. Crystals rare, as thin plates or prismatic [001] or{010} with a six-sided outline about [010], very complex, with about 60 forms noted. Commonly
fibrous, to 5 mm, forming delicate masses, crusts, and efflorescences. Twinning: On {010}.
Physical Properties:
Cleavage: {010}, perfect; probable on {100} and {313}.
Hardness = 1.5–2 D(meas.) = 1.72–1.77 D(calc.) = 1.79 Soluble in H2 O; taste alumlike, acidand sharp.
Optical Properties: Transparent. Color: Colorless in crystals, aggregates white, or pale yellow
or red from impurities; colorless in transmitted light. Luster: Vitreous to silky.
Optical Class: Biaxial (+). Orientation: X ' b; Z ∧ c = 42◦ .
α = 1.459–1.475
β = 1.461–1.478 γ = 1.470–1.485 2V(meas.) = 31◦
Cell Data: Space Group: P 1. a = 7.420(6)β = 97◦ 34(5)0 γ = 91◦ 53(5)0 Z = 2b = 26.97(2)c = 6.062(5)α = 89◦ 57(5)0

X-ray Powder Pattern: Nová Baňa, Slovakia.
4.489 (100), 4.390 (81), 3.969 (81), 4.329 (76), 13.46 (54), 3.897 (52), 3.675 (45)Chemistry:
SO3Al2 O3H2 O
insol.

(1)
37.74
16.59
44.64
0.94

(2)
37.04
15.73
47.23

Total
99.91
100.00(1) Pintado Canyon, Guadalupe Co., New Mexico, USA. (2) Al2 (SO4 )3 • 17H2 O.
Occurrence: Forms by reaction of sulfates from decomposing sulfides with aluminous minerals
in shales and slates; in gossan or altered wall rock of pyritic deposits in arid regions; in coal seams;
in relatively low-temperature fumaroles.
Association:Pyrite, marcasite, halotrichite, pickeringite, epsomite, alum, melanterite, gypsum.

Distribution: Many localities, at some in large amounts. From near Nová Baňa (Königsberg),
Slovakia. In Italy, on Vesuvius, and from Solfatara di Pozzuoli, Campi Flegrei, and at Miseno,
near Naples, Campania; on Vulcano, Lipari Islands. In France, at Sain-Bel, Rhône; in coal atRonchamp, Haute-Saône. At Libros, near Teruel, Teruel Province, Spain. From the StammAsser mine, near Schwartzenberg, and at Bräunsdorf, near Freiberg, Saxony, Germany. From theAvacha and other volcanoes, Kamchatka Peninsula, Russia. In Chile, at Francisco de Vergara,Antofagasta, and from Cerros Pintados, near Iquique, Tarapacá. On Mount Pelée, Martinique. Inthe USA, abundant at Smoky Mountain, Jackson Co., North Carolina; at Alum Cave Bluff, SevierCo., Tennessee; extensive deposits in the Alum Mountain district, Grant Co., New Mexico; atThe Geysers, Sonoma Co., California; good crystals from the Dexter No. 7 mine, Calf Mesa, San
Rafael district, Emery Co., Utah; from the Mount St. Augustine volcano, Alaska. In Canada
near Vernon, British Columbia; and Scotia mine, Cumberland Co., Nova Scotia. At geothermalareas of Tengchong, Yunnan Province, China. Found in the Heritage Range, Ellsworth Mountains,
Antarctica. From near Joadja, New South Wales, Australia.
Name:

From the Latin for alum and the Greek for to make.

References: (1) Palache, C., H. Berman, and C. Frondel (1951) Dana’s system of mineralogy,(7th edition), v. II, 537–540. (2) Cesbron, F. and M. Sadrzadeh (1972) Nouvelles données surl’alunogène Al2 (SO4 )3 • 18H2 O. Bull. Soc. fr. Minéral., 96, 385–387 (in French). (3) Fang, J. H.
and P.D. Robinson (1976) Alunogen, Al2 (H2 O)12 (SO4 )3 • 5H2 O: its atomic arrangement and watercontent. Amer. Mineral., 61, 311–317.
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