Aluminium silicate (or 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.
Aluminum silicate has been used commercially and medicinally for hundreds of years. It is currently found in the manufacture of pottery, bricks, cement, plastering material, color lakes (insoluble dyes), and insulators. As a raw material, it is commonly found in paper, plastics, cosmetics, and pharmaceuticals, and it is also used in pharmaceutical preparations as a filtering agent to clarify liquids.