Ocher is a natural dye that has been used by men for nearly 300,000 years. Its color is derived from minerals such as goethite (yellow ocher), hematite (red ocher), and limonite (brown ocher). Prehistoric people already knew that heated yellow ocher went through orange and brown to become red. The chemical properties of ocher do not depend on its color, and prehistoric people arguably favored red ocher for its symbolic meaning and resemblance with blood.