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Fougèrite is a relatively recently described naturally occurring green rust mineral. It is the archetype of the fougèrite group in the larger hydrotalcite supergroup of naturally occurring layered double hydroxides.[2] The structure is based on brucite-like layers containing Fe2+ and Fe3+ cations, O2− and OH− anions, with loosely bound [CO3]2− groups and H2O molecules between the layers. Fougèrite crystallizes in trigonal system. The ideal formula for fougèrite is [Fe2+4Fe3+2(OH)12][CO3]·3H2O. Higher degrees of oxidation produce the other members of the fougèrite group, namely trébeurdenite, [Fe2+2Fe3+4O2(OH)10][CO3]·3H2O and mössbauerite, [Fe3+6O4(OH)8][CO3]·3H2O.

Fougèrite was first found in forested soils near Fougères, Brittany, France, and recognised as a valid mineral species by the International Mineralogical Association in 2002.[1] It is blue-green to bluish-gray in colour, and resembles clay minerals in habit, forming hexagonal platelets of submicron diameter. In this environment, it is intimately intergrown with trébeurdenite, to give varying overall ratios of Fe2+:Fe3+. The existence of two intergrown fixed-composition phases has been demonstrated by Mössbauer spectroscopy. The mineral is unstable in air, and decomposes by oxidation, dehydration and decarbonation, to ferrihydrite, and ultimately to lepidocrocite or goethite, Fe3+O(OH).[3][4]

CategoryHydroxide mineral
(repeating unit)
Strunz classification4.FL.05
Crystal systemTrigonal
Crystal class3m (32/m) - Hexagonal scalenohedral
Space groupR3m
Unit cella = 3.125 Å, c = 22.5 Å
ColourBluish green
Alters toUnstable - alters to goethite or limonite

See also

  • Clay minerals

  • Gley soil

  • Iron(II) hydroxide


Citation Linkwww.mindat.orgFougèrite data on Mindat.org
Sep 21, 2019, 12:32 AM
Citation Linkpubsites.uws.edu.auMills, S.J., Christy, A.G., Génin J.-M.R., Kameda, T. and Colombo, F. 2012: Nomenclature of the hydrotalcite supergroup: natural layered double hydroxides, Mineralogical Magazine, 76, 1289-1336. [1]
Sep 21, 2019, 12:32 AM
Citation Linkdoi.orgTrolard F., Bourrié G., Abdelmoula M., Refait P. and Feder F. 2007: Fougerite, a new mineral of the pyroaurite-iowaite group: description and crystal structure, Clays and Clay Minerals, vol. 55, no. 3, p. 323-334; doi:10.1346/CCMN.2007.0550308
Sep 21, 2019, 12:32 AM
Citation Linkdoi.orgGénin J.-M. R., Aïssa R., Géhin A., Abdelmoula M., Benali O., Ernstsen V., Ona-Nguema G., Upadhyay Ch. and Ruby Ch.; 2005: Fougerite and FeII-III hydroxycarbonate green rust; ordering, deprotonation and/or cation substitution; structure of hydrotalcite-like compounds and mythic ferrosic hydroxide Fe(OH)2+x, Solid State Sciences, vol. 7., no. 5, p. 545-572. doi:10.1016/j.solidstatesciences.2005.02.001.
Sep 21, 2019, 12:32 AM
Citation Linkwww.mindat.orgFougèrite data on Mindat.org
Sep 21, 2019, 12:32 AM
Citation Linkpubsites.uws.edu.au[1]
Sep 21, 2019, 12:32 AM
Citation Linkdoi.org10.1346/CCMN.2007.0550308
Sep 21, 2019, 12:32 AM
Citation Linkdoi.org10.1016/j.solidstatesciences.2005.02.001
Sep 21, 2019, 12:32 AM
Citation Linken.wikipedia.orgThe original version of this page is from Wikipedia, you can edit the page right here on Everipedia.Text is available under the Creative Commons Attribution-ShareAlike License.Additional terms may apply.See everipedia.org/everipedia-termsfor further details.Images/media credited individually (click the icon for details).
Sep 21, 2019, 12:32 AM