Clay is widely used for cosmetic purposes because it draws out and absorbs oil from the skin. Soaps made with clay are somewhat drying.
Clays are fine grained particles that originated thousands of years ago as igneous rock. All clays are perhaps the finest grained materials obtained from the earth. Clays, water, air, and organic matter are the four major constituents of soil.

Chemically, clays are silicates-compounds of silicon, oxygen, and other metals that are chemically combined with water. About 30 % of all minerals occur in the form of silicates. The silicates are arranged in layers with water trapped in-between. Clays are known for their ability to expand, as they can absorb large quantities of water between their sheets or layers.

Both kaolin and French clays are used by natural cosmetic companies in masks, soaps, and powders. It properties are astringent and cleansing. Kaolin is generally the mildest of clays used cosmetically.