After the various phases of extraction, washing, settling, and drying, the ocher is transported to the factory to complete its manufacture and to be calcined. The iron oxide of raw ochres is a goethite (hydrated oxide) which, when heated to 1472-1652° F (800-900° C) in gas rotary ovens, dehydrates and turns into hematite. Its color, usually yellow, then becomes red. The ovens used have a length of 49.2 ft (15 m), a diameter of 3.2 ft (1 m), and are bricked to retain the heat.