a rare clay mineral, aluminum silicate, Al 6 Si 2 O 1 3 , produced artificially during various melting and firing processes: used as a refractory.
Also called porcelainite.

1924; after Mull, source of the rocks in which it was first identified; see -ite1 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
mullite (ˈmʌlaɪt)
a colourless mineral consisting of aluminium silicate in orthorhombic crystalline form: used as a refractory. Formula: Al6Si2O13
[from island of Mull]

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Encyclopedia Britannica


any of a type of rare mineral consisting of aluminum silicate (3Al2O32SiO2). It is formed upon firing aluminosilicate raw materials and is the most important constituent of ceramic whiteware, porcelains, and high-temperature insulating and refractory materials. Compositions, such as mullite, having an alumina-silica ratio of at least 3:2 will not melt below 1,810 C (3,290 F), whereas those with a lower ratio partially melt at temperatures as low as 1,545 C (2,813 F)

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Mullite in refractories increases the fired strength, resistance to deformation under load, and thermal resistivity.
Second formed in brightly incandescent area into which a mullite gas-sampling tube is inserted.
Exclude plastic refractories and ramming mixes of mullite or extra high alumina.
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