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Alunite

Alunite is a hydroxylated aluminium potassium sulfate mineral, formula KAl3(SO4)2(OH)6. It was first observed in the 15th century at Tolfa, near Rome, where it was mined for the manufacture of alum. First called aluminilite by J.C. Delamétherie in 1797, this name was contracted by François Beudant three decades later to alunite.

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Birefringence
δ = 0.020
Category
Sulfate minerals
Cleavage
On {0001}, perfect
Color
Yellow, red, to reddish brown, colorless if pure; may be white, pale shades of gray
Crystal class
Hexagonal scalenohedral (3m) Space group: (3 2/m)
Crystal habit
fibrous to columnar, porcelaneous, commonly granular to dense massive

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Alunite

Nodes40
Edges39
Triples24
Avg. degree1.95
Density0.05
Components1

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Alunite

Top relations

is a · 2
Alunite → analog of jarosite, hydroxylated aluminium potassium sulfate mineral
Birefringence · 1
Alunite → δ = 0.020
Category · 1
Alunite → Sulfate minerals
Cleavage · 1
Alunite → On {0001}, perfect
Color · 1
Alunite → Yellow, red, to reddish brown, colorless if pure; may be white, pale shades of gray
Crystal class · 1
Alunite → Hexagonal scalenohedral (3m) Space group: (3 2/m)
Crystal habit · 1
Alunite → fibrous to columnar, porcelaneous, commonly granular to dense massive
Crystal system · 1
Alunite → Trigonal
Diaphaneity · 1
Alunite → Transparent to translucent
Formula · 1
Alunite → KAl3(SO4)2(OH)6

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Important terminology

potassium found mined mineral aluminium near deposits alum also sulfate crystals white acid tolfa rhyolite hungary marysvale ore trigonal first

Entity relationships Subject–Predicate–Object triples

SubjectPredicateObjectConfidenceSrc
AluniteBirefringenceδ = 0.0201.00infobox
AluniteCategorySulfate minerals1.00infobox
AluniteCleavageOn {0001}, perfect1.00infobox
AluniteColorYellow, red, to reddish brown, colorless if pure; may be white, pale shades of gray1.00infobox
AluniteCrystal classHexagonal scalenohedral (3m) Space group: (3 2/m)1.00infobox
AluniteCrystal habitfibrous to columnar, porcelaneous, commonly granular to dense massive1.00infobox
AluniteCrystal systemTrigonal1.00infobox
AluniteDiaphaneityTransparent to translucent1.00infobox
AluniteFormulaKAl3(SO4)2(OH)61.00infobox
AluniteFractureConchoidal1.00infobox
AluniteIMA symbolAlu1.00infobox
AluniteLusterVitreous, somewhat pearly on {0001} for crystals, earthy if massive1.00infobox
AluniteMohs scale hardness3.5 – 41.00infobox
AluniteOptical propertiesUniaxial (+)1.00infobox
AluniteOther characteristicsStrongly pyroelectric Radioactive 9.44% (K)1.00infobox
AluniteRefractive indexnω = 1.572 nε = 1.5921.00infobox
AluniteSpace groupR3m1.00infobox
AluniteSpecific gravity2.6 – 2.91.00infobox
AluniteStreakWhite1.00infobox
AluniteStrunz classification7.BC.101.00infobox
AluniteTenacityBrittle1.00infobox
AluniteUnit cella = 6.98, c = 17.32 [Å]; Z = 31.00infobox
Aluniteis ahydroxylated aluminium potassium sulfate mineral0.90text
Aluniteis aanalog of jarosite0.90text

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