Goethite
The goethite is a Minéral, Hydroxyde of Fer, polymorphic α of made up FeO (OH). Oxygens and oxhydryles form layers with hexagonal stacking, the cations Fer fill half of the octahedral cavities. The polymorphic with cubic stacking is the Lépidocrocite, γ-FeO (OH).
The goethite is presented in the form of crystals in the shape of needle. It does not present private interest for the collector, but is exploited like ore of Fer, and also like Pigment.
Enough common, the goethite is formed in the grounds rich in iron, by deterioration of other minerals. It is the component main thing of the Limonite in the Chapeau of iron. One also finds some in the form of Sédiment S, or directly formed by hydrothermal action.
The goethite is known since prehistory. It was used as pigment in paintings of the Grotte of Lascaux. Its name comes from the German writer Johann Wolfgang von Goethe, which was also interested in mineralogy.
The goethite is present on the whole of the ground. The principal layers are located in England, with Cuba, the United States in the States of the Michigan, Minnesota, Missouri, Colorado, Alabama, Georgia, Virginia, and Tennessee. In France, it is in particular present in the Ocres of the " Colorado of Provence " with Rustrel.
The robot of NASA Spirit also discovered samples of goethite on the planet Mars, in the crater of Gusev, bringing an index of the liquid presence of water in the past of this planet.
See too
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crystalline Structures of the hydroxides oxy-hydroxides and iron oxides
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