|
Bauxite, an aluminium ore, is the world's main source of aluminium. It consists mostly of the minerals gibbsite Al(OH)3, boehmite γ-AlO(OH) and diaspore α-AlO(OH), mixed with the two iron oxides goethite and haematite, the clay mineral kaolinite and small amounts of anatase TiO2. In 1821 the French geologist Pierre Berthier discovered bauxite near the village of Les Baux in Provence, southern France.〔P. Berthier (1821) ("Analyse de l'alumine hydratée des Beaux, département des Bouches-du-Rhóne" ) (Analysis of hydrated alumina from Les Beaux, department of the Mouths-of-the-Rhone), ''Annales des mines'', 1st series, 6 : 531-534.〕 In 1861, French chemist Henri Sainte-Claire Deville named the mineral "bauxite".〔Notes: * In 1847, in the cumulative index of volume 3 of his series, ''Traité de minéralogie'', French mineralogist Armand Dufrénoy listed the hydrated alumina from Les Beaux as "beauxite". (See: A. Dufrénoy, ''Traité de minéralogie'', volume 3 (Paris, France: Carilian-Goeury et Vor Dalmont, 1847), (p. 799. )) * In 1861, H. Sainte-Claire Deville named "bauxite" on p. 309, "Chapitre 1. Minerais alumineux ou bauxite" of: H. Sainte-Claire Deville (1861) ("De la présence du vanadium dans un minerai alumineux du midi de la France. Études analytiques sur les matières alumineuses." ) (On the presence of vanadium in an alumina mineral from the Midi of France. Analytical studies of aluminum substances.), ''Annales de Chimie de de Physique'', 3rd series, 61 : 309-342.〕 == Formation == Lateritic bauxites (silicate bauxites) are distinguished from karst bauxite ores (carbonate bauxites). The carbonate bauxites occur predominantly in Europe and Jamaica above carbonate rocks (limestone and dolomite), where they were formed by lateritic weathering and residual accumulation of intercalated clay layers – dispersed clays which were concentrated as the enclosing limestones gradually dissolved during chemical weathering. The lateritic bauxites are found mostly in the countries of the tropics. They were formed by lateritization of various silicate rocks such as granite, gneiss, basalt, syenite, and shale. In comparison with the iron-rich laterites, the formation of bauxites depends even more on intense weathering conditions in a location with very good drainage. This enables the dissolution of the kaolinite and the precipitation of the gibbsite. Zones with highest aluminium content are frequently located below a ferruginous surface layer. The aluminium hydroxide in the lateritic bauxite deposits is almost exclusively gibbsite. In the case of Jamaica, recent analysis of the soils showed elevated levels of cadmium, suggesting that the bauxite originates from recent Miocene ash deposits from episodes of significant volcanism in Central America. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「bauxite」の詳細全文を読む スポンサード リンク
|