Гётит: Гёте атымен аталған темір оксид гидроксиді

Iron(III) oxide hydroxide named in honor to the poet Goethe

Goethite ('/ɡ//ɜːr//t//aɪ//t/, /usalso/'/ɡ//oʊ//θ//aɪ//t/) is a mineral of the diaspore group, consisting of iron(III) oxide hydroxide, specifically the α polymorph. It is found in soil and other low temperature environments such as sediment. Goethite has been well known since ancient times for its use as a pigment (brown ochre). Evidence has been found of its use in paint pigment samples taken from the caves of Lascaux in France. It was first described in 1806 based on samples found in the Hollertszug Mine in Herdorf, Germany. a cubic pyrite type polymorph with or without losing hydrogen and an ultradense hexagonal structure. Goethite has the same crystal structure as diaspore, the analogous aluminium oxide hydroxide mineral. Oxygen and hydroxide ions form a hexagonal close packed structure, with iron ions filling octahedral sites between the anions. The sites filled by iron ions form paired chains running the length of the crystal, with the two chains in each pair joined by hydroxide ions.

Goethite often forms through the weathering of other iron rich minerals, and thus is a common component of soils, concentrated in laterite soils. nanoparticulate authigenic goethite is a common diagenetic iron oxyhydroxide in both marine and lake sediments. The formation of goethite is marked by the oxidation state change of Fe2+ (ferrous) to Fe3+ (ferric), which allows for goethite to exist at surface conditions. Because of this oxidation state change, goethite is commonly seen as a pseudomorph. As iron bearing minerals are brought to the zone of oxidation within the soil, the iron turns from iron(II) to iron(III), while the original shape of the parent mineral is retained. Common goethite pseudomorphs include pyrite, siderite, and marcasite, though any iron(II) bearing mineral could become a goethite pseudomorph if proper conditions are met. It may also be precipitated by groundwater or in other sedimentary conditions, or form as a primary mineral in hydrothermal deposits. Goethite has also been found to be produced by the excretion processes of certain bacteria types.

Its main modern use is as an iron ore, being referred to as brown iron ore. and has been heat treated for use as a red pigment since Paleolithic times. Iron rich lateritic soils that have developed over serpentinite rocks in tropical climates are mined for their iron content, as well as other metals. Fine goethite specimens are rare and therefore are valued collectibles. In a royal tomb of the ancient kingdom of Phrygia, a body was found believed to be King Gordias, father of the legendary King Midas. The burial shroud had been colored with a dye containing goethite, which in its original unfaded state would have made the shroud look like it was woven from gold. Historians speculate that the legend of King Midas' golden touch might have originated from Phrygian royalty wearing clothes made from such golden colored textiles.