Goethite

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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.

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