Fougèrite

Fe2+4Fe3+2(OH)12(CO3) · 3H2O
IMA status
  • Approved
IMA symbol
Fgè
IMA approved
2003
Also known as
  • Fougèriet
  • Green Rust
  • IMA2003-057

Where it forms, where it's found

Geological setting

Subsurface horizon of a Gleysol soil. Partial oxidation and hydrolysis of aqueous Fe2+.

Type locality
Fougères Forest
  1. Fougères
  2. Fougères-Vitré
  3. Ille-et-Vilaine
  4. Brittany
  5. France

48.3950°, -1.1633°

25recorded occurrences
Source · OpenStreetMap

Physical

Transparency
Opaque
Colour
Bluish green · green · green-black · blackish

Only when fresh; alters within hours and days

Optical

UV response
Not fluorescent.

Crystallography

Crystal system
Trigonal
Space group
#99
Cell parameters
a = 3.125 Å · c = 22.5 Å
Type-locality form

Small crystals (400-500 nm) in the form of hexagonal plates.

Crystal structure

Chemical composition

Constituent elements
Mass composition breakdown
ElementAtoms At. mass g/mol Mass g/molMass share
26FeIronIron655.845335.070
51.29%
8OOxygenOxygen1815.999287.982
44.09%
1HHydrogenHydrogen181.00818.144
2.78%
6CCarbonCarbon112.01112.011
1.84%
Total653.207100.00%

Mass share = atoms × atomic mass ÷ molar mass × 100

From IMA formula

Synonyms

  • Fougèriet
  • Green Rust
  • IMA2003-057

In other languages

French
Fougérite · rouille verte
German
Fougèrit
Italian
fougèrite
Chinese
Fe3(OH)8 · 绿锈

Classification

Strunz
10th ed.

4.FL.05

  • 4OxidesClass
  • 4.FHydroxides (without V or U)Division
  • 4.FLHydroxides with H2O +- (OH); sheets of edge-sharing octahedraGroup
  • 4.FL.05FougèriteSpecies
Dana
8th ed.

06.04.06.02

  • 06Hydroxides and Oxides Containing HydroxylClass
  • 06.04MiscellaneousType
  • 06.04.06— unnamed intermediate level —Group
  • 06.04.06.02FougèriteSpecies

Group, growth & confusion

In the same group
2 members

Literature, links & citation

Citations
  1. 1985Nieding, E. (1985) Rezente Mineralbildungen in urzeitlichen Kupferschlacken aus Österreich. Aufschluss: 36: 313–318. (in German)
  2. 1986Nieding, E. (1986) Pseudohexagonaler Goethit aus einer Schlacke von Lölling/Kärnten. Carinthia II: 176(96): 57–59. (in German)
  3. 1996Trolard, F., Abdelmoula, M., Bourrie, G., Humbert, B., Genin, J. (1996) Evidence of the occurrence of a 'green rusts' component in hydromorphic soils. Proposed existence of a new mineral fougerite. CRAS (Paris), serie IIa: 232: 1015-1022.
  4. 1997Blaß, G., Graf, H.-W., Pichler, A. (1997) Sekundäre Neubildungen in Schlacken von St. Martin am Silberberg in Kärnten (2). Mineralien-Welt: 8(6): 54-55. (in German)
  5. 1997Trolard, F.; Génin, J.-M.R.; Abdelmoula, M.; Bourrié, G.; Humbert, B.; Herbillon, A. (1997) Identification of a green rust mineral in a reductomorphic soil by Mössbauer and Raman spectroscopies. Geochimica et Cosmochimica Acta, 61 (5). 1107-1111 doi:10.1016/s0016-7037(96)00381-xDOI: 10.1016/s0016-7037(96)00381-x
Cite this entry
@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Fougèrite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/fougerite-27543},
  note      = {Accessed 2026-05-11}
}