Alumina

Alumina is another name for the compound aluminum oxide. It is a white powder used as a thickener, absorbent, and abrasive.

As an absorbent, alumina can give a mattifying effect. It is used in mineral sunscreens to help coat nano-sized filters, such as titanium dioxide. By increasing the size of the UV filters, these ingredients stay on the skin for a longer time. By coating small sized ingredients, alumina helps thicken a product.

Alumina may be used as an abrasive, or exfoliant.

Alumina is naturally occurring in the mineral corundum. Certain varieties of corundum create rubies and sapphires. Corundum is also the crystalline form of alumina.