- Fougerite
Fougerite is a recently discovered representative of
clay minerals , chemically and structurally related to so-called green rust, hydrotalcite-like minerals (hydrotalcite, pyroaurite, iowaite, manasseite) and otherlayered double hydroxides . The formula of the mineral is complex due to structural variabilites, as is for green rust, thus different formulas can be found elsewhere. The structure is based onbrucite -like layers. Fougerite crystallizes in trigonal system. The originally given formula for fougerite is [Fe2+1-xFe3+xMgy(OH)2+2y] +x [x/n A-n.mH2O] -x where A denotes an interlayer anion, n denotes valency, by 1/4 ≤ x/(1+y) ≤ 1/3 and m ≤ (1-x+y) (Trolard et al. 2007).The interlayer anions may be OH-, Cl-, CO32-, SO42- and other. Fougerite is unique among other
clay minerals due to having a positive layer charge.Fougerite was found in forested soils near Fougères. It possess blue-green to bluish-gray colour. It is regarded as a precursor for other iron hydroxides and related compounds, like
goethite ,lepidocrocite andferrihydrite (Trolard et al. 2007, Génin et al. 2005).ee also
*
Iron(II) hydroxide
*Layered double hydroxides
*Clay minerals References
1. Trolard 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
2. Génin 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
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