What is "aluminium silicate"

alt. A chemical compound composed of aluminium, silicon and oxygen, chemical formula Al₂SiO₅, found in minerals and clays in several forms and used commercially as food additive E559 as an anti-caking agent. n. A chemical compound composed of aluminium, silicon and oxygen, chemical formula Al₂SiO₅, found in minerals and clays in several forms and used commercially as food additive E559 as an anti-caking agent.

Aluminium silicate (or aluminum silicate) is a name commonly applied to chemical compounds which are derived from aluminium oxide, AlO and silicon dioxide, SiO which may be anhydrous or hydrated, naturally occurring as minerals or synthetic. Their chemical formulae are often expressed as xAlO.ySiO.zHO These include the compounds:-

• AlSiO, (AlO.SiO), which occurs naturally as the minerals andalusite, kyanite and sillimanite which have different crystal structures.
• AlSiO(OH), (AlO·2SiO·2HO), which occurs naturally as the mineral kaolinite and is also called aluminium silicate dihydrate. It is a fine white powder and is used as a filler in paper and rubber and also used in paints.
• AlSiO, (AlO.2SiO), called metakaolinite, formed from kaolin by heating at .
• AlSiO, (3AlO.2SiO), the mineral mullite, the only thermodynamically stable intermediate phase in the AlO-SiO system at atmospheric pressure. This also called '3:2 mullite' to distinguish it from 2AlO.SiO, AlSiO '2:1 mullite'.
• 2AlO.SiO, AlSiO '2:1 mullite'.