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Formula: Fe2+4Fe3+2(OH)12(CO3).3H2O
Hydroxide, fougèrite group,
hydrotalcite supergroup
Crystal System: Trigonal
Colour: Bluish green, green, green-black, blackish
Luminescence: Not fluorescent under UV
Environments
Localities
At the type locality, Fougères Forest, Fougères, Fougères-Vitré, Ille-et-Vilaine, Brittany, France, fougèrite
occurs as Small crystals, 400 to 500 nm in size, in the form of hexagonal plates. It
forms by partial oxidation and hydrolysis of aqueous Fe2+. It is unstable in air and transforms to
lepidocrocite or goethite.
Associated minerals include kaolinite,
vermiculite, quartz,
illite and feldspars
(HOM).
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