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.

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goethite [′gə‚tīt]

(mineralogy)

FeO(OH) A yellow, red, or dark-brown mineral crystallizing in the orthorhombic system, although it is usually found in radiating fibrous aggregates; a common constituent of natural rust or limonite. Also known as xanthosiderite.

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Goethite 

(named in honor of the poet J. W. Goethe), a mineral of the iron hydroxide group; chemical composition FeOOH. It contains admixtures of manganese and aluminum, as well as surplus adsorbed water (hydrogoethite). The mineral crystallizes in a rhombic system, forming columnar, needle-like crystals and their growths, sinter aggregates, and powdery and earthy masses mixed with hydrogoethite, hydrohematite, and other minerals (so-called limonites and bog iron ores). The color is brownish yellow to dark reddish brown. Needlelike crystals of goethite gathered into bundles are called needle ironstone. The hardness of goethite on the mineralogical scale is 5-5.5; density, 4,140-4,280 kg/m³. Goethite in crystals sprouting quartz, together with iron sulfides and other sulfides, is found in hydrothermal deposits, which are numerous in the USSR and abroad. The widest distribution of goethite in nature is associated with supergene and sedimentary deposits of iron ores.

G. P. BARSANOV