[muhl-ahyt] 
| a rare clay mineral, aluminum silicate, Al6Si2O1 3, produced artificially during various melting and firing processes: used as a refractory. |
mullite
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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