Mullite

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Description

A stable crystalline form of aluminum silicate. Mullite is formed by heating aluminum silicate compounds, such as cyanite, sillimanite and andalusite, to high temperatures. It begins forming at 1000 C and the conversion is nearly complete by 1340 C. Mullite has needle-shaped crystals which provide a felting effect for strengthening stoneware and porcelain (Fournier 1996).

Synonyms and Related Terms

none; Mullit (Deut.); mulliet (Ned.)

Other Properties

Insoluble in water.

Orthorhombic system with needle-shaped crystals. Good cleavage in one direction

Composition 3Al2O3 - 2SiO2
Melting Point 1810
Density 3.15
Refractive Index 1.642 -1.679

Additional Information

R. Fournier, Illustrated Dictionary of Practical Pottery, Chilton Book Co., Radnor, PA, 1996.