Mineral makeup owes its range of skin-complementing shades to iron oxide, a mineral that you may know better by its common name: rust. And while it might be hard to reconcile the notion of a rusty old fender with an ingredient in your favorite foundation, iron oxides have been used in cosmetics for centuries.
The iron oxides used in mineral makeup are naturally occurring, and before they're added to any cosmetic, they are purified and ground into a fine powder. Iron oxides are found in a range of Earth-tone colors, including reds, yellows, oranges, browns and black, and they are often used in powders, blushes, bronzers, foundations and eye shadows.
Like most of the ingredients used in mineral makeup, iron oxide is hypoallergenic, but if you have sensitive skin, you might want to skip the next mineral on our list.