mullite

Mullite or porcelainite is a rare silicate mineral formed during contact metamorphism of clay minerals. It can form two stoichiometric forms: 3Al2O32SiO2 or 2Al2O3 SiO2. Unusually, mullite has no charge-balancing cations present. As a result, there are three different aluminium sites: two distorted tetrahedral and one octahedral.

Key facts

Mineral.name: Mullite
Mineral.category: Nesosilicate
Mineral.image: Osumilite, thick tabulars with Mullite - Ochtendung, Eifel, Germany.jpg
Mineral.imagesize: 260px
Mineral.caption: White, filamentous mullite in front of thicker osumilite platelets(Photo width 1.5 mm)Found in Wannenköpfe, Ochtendung, Eifel, Germany
Mineral.formula: Al6Si2O13
Mineral.IMAsymbol: Mul
Mineral.strunz: 9.AF.20
Mineral.system: Orthorhombic
Mineral.class: Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Mineral.symmetry: Pbnm, Pnnm
Mineral.unit cell: a = 7.5785(6) Å, b = 7.6817(7) Å, c = 2.8864(3) Å; Z = 1
Mineral.color: Colorless to pale pink or grey
Mineral.habit: Prismatic to acicular crystals
Mineral.cleavage: Good on [010]
Mineral.opticalprop: Biaxial (+)
Mineral.refractive: nα = 1.642–1.653 nβ = 1.644–1.655 nγ = 1.654–1.679
Mineral.birefringence: δ = 0.012–0.026

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Wikidata facts

Image: Mullite-655833.jpg

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Nickel-Strunz '10th ed', review of (9th ed/ 2009 update): 9.AF.20
Commons category: Mullite
Nickel-Strunz 9th edition (updated 2009): 9.AF.20
IMA Mineral Symbol: Mul
chemical formula: 3Al₂O₃·2SiO₂
Strunz 8th edition (series ID, updated): VIII/A’.02 – Anhang

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Article

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Contents

Porcellanite
Use in porcelain
Use as a catalyst
References

Mullite was first described in 1924 for an occurrence on the Isle of Mull, Scotland. It occurs as argillaceous inclusions in volcanic rocks in the Isle of Mull, inclusions in sillimanite within a tonalite at Val Sissone, Italy and with emerylike rocks in Argyllshire, Scotland.