Iron Oxides are found naturally in the world but are full of impurities and cannot be purified.
Iron Oxides (E 172) are very stable inorganic pigments but tend to be rather dull in appearance. They can be easily blended into dry mixtures or dispersed into a variety of aqueous or oil based liquid mediums. Most commonly used as a combination of Black, Red and Yellow Iron Oxide to give a variety of brown shades.