Goethite

Goethite, common ore of iron, and one of the most commonly occurring minerals in nature. An iron hydroxide mineral, FeO(OH), goethite generally contains about 63 per cent iron. Manganese is often present in amounts up to 5 per cent. Goethite is formed as a weathering product of other iron minerals. It is also precipitated from water and deposited at the bottom of bogs and springs in a form known as bog-iron ore. Such deposits are usually associated with foreign materials and are too impure to be worked commercially for the iron.

Goethite is widely distributed; some of the most notable workable deposits are found, usually associated with other iron materials, in Alsace-Lorraine, Westphalia, Bohemia, and in the Lake Superior and Appalachian Mountain regions in the United States. The ore is yellow-brown to dark brown in colour, has a hardness of 5.5, and a relative density of 4.3. It crystallizes in the rhombic system in acicular crystals and in stalactitic aggregates. Goethite is named in honour of the German poet-philosopher Johann Wolfgang von Goethe.