goethite

goethite

Widespread iron hydroxide mineral, α-FeO(OH), the most common ingredient of iron rust. In terms of relative abundance, it is second only to hematite (α-Fe₂O₃) among iron oxides. Goethite varies in colour from yellow-brown to red and is the source for the pigment known as yellow ocher; it is also the primary mineral in some important iron ores, such as those in the Alsace-Lorraine basin in France. Other important deposits are found in the southern Appalachian Mountains of the U.S., and in Brazil, South Africa, Russia, and Australia.