Aluminium silicate

Aluminum silicate is a name commonly applied to chemical compounds which are derived from aluminium oxide, Al₂O₃ and silicon dioxide, SiO₂ which may be anhydrous or hydrated, naturally occurring as minerals or synthetic. Their chemical formulae are often expressed as xAl₂O₃·ySiO₂·zH₂O. It is known as E number E559.

Main representatives

, kyanite, and sillimanite are the principal aluminium silicate minerals. The triple point of the three polymorphs is located at a temperature of and a pressure of. These three minerals are commonly used as index minerals in metamorphic rocks.

Al₂SiO₅,, which occurs naturally as the minerals andalusite, kyanite and sillimanite which have distinct crystal structures.
Al₂Si₂O₇,, called metakaolinite, formed from kaolin by heating at.
Al₆Si₂O₁₃,, the mineral mullite, the only thermodynamically stable intermediate phase in the Al₂O₃-SiO₂ system at atmospheric pressure. This also called '3:2 mullite' to distinguish it from 2Al₂O₃·SiO₂, Al₄SiO₈ '2:1 mullite'.
2Al₂O₃·SiO₂, Al₄SiO₈ '2:1 mullite'.

The above list mentions ternary materials. Kaolinite is a quaternary material. Also called aluminium silicate dihydrate, kaolinite occurs naturally as a mineral. Its formula is Al₂Si₂O₅₄,.

Aluminium silicate composite materials, fibres

Aluminium silicate is a type of fibrous material made of aluminium oxide and silicon dioxide,. These are glassy solid solutions rather than chemical compounds. The compositions are often described in terms of % weight of alumina, Al₂O₃ and silica, SiO₂. Temperature resistance increases as the % alumina increases. These fibrous materials can be encountered as loose wool, blanket, felt, paper or boards.