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|System:||Trigonal||Colour:||dark brown, yellow-brown|
|Name:||For the chemical composition (hydrated ferric iron oxide).|
A poorly crystalline nanomineral built up of about 20% (FeO4) and 80% (FeO6) polyhedra. It forms by rapid oxidation and hydrolysis, and exists in varying degrees of structure disorder; the two extremes are the so-called 2-line and 6-line ferrihydrites (distinguished by their X-ray powder diffraction patterns). It is a metastable nanomineral precursor to other minerals, e.g. hematite.
Two structure models have been proposed: the "f-phase" model and the "akdalaite" model; the first one seems to be correct (Paktunc et al., 2013).
Classification of Ferrihydrite
|IMA status:||Approved 1971|
|Strunz 8th edition ID:||4/F.09-20|
|Nickel-Strunz 10th (pending) edition ID:||4.FE.35|
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
F : Hydroxides (without V or U)
E : Hydroxides with OH, without H2O; sheets of edge-sharing octahedra
|Dana 8th edition ID:||188.8.131.52|
4 : SIMPLE OXIDES
3 : A2X3
|Hey's CIM Ref.:||7.20.9|
7 : Oxides and Hydroxides
20 : Oxides of Fe
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Type Occurrence of Ferrihydrite
|Co-type Localities:||Belousovskii Mine, Altai Mts (Rudnyi Altai), Eastern Kazakhstan Province (Shyghys Qazaqstan Oblysy; Vostochno-Kazakhstanskaya Oblast'), Kazakhstan|
Ridder Mine (Leninogorsk Mine), Altai Mts (Rudnyi Altai), Eastern Kazakhstan Province (Shyghys Qazaqstan Oblysy; Vostochno-Kazakhstanskaya Oblast'), Kazakhstan
|Year of Discovery:||1971|
Physical Properties of Ferrihydrite
|Colour:||dark brown, yellow-brown|
Crystallography of Ferrihydrite
|Cell Parameters:||a = 2.96Å, c = 9.4Å|
|Ratio:||a:c = 1 : 3.176|
|Unit Cell Volume:||V 71.33 Å³ (Calculated from Unit Cell)|
Chemical Properties of Ferrihydrite
|Simplified for copy/paste:||Fe3+5O3(OH)9|
|Essential elements:||Fe, H, O|
|All elements listed in formula:||Fe, H, O|
Relationship of Ferrihydrite to other Species
|Related Minerals - Nickel-Strunz Grouping):|
|Related Minerals - Hey's Index Grouping:|
Other Names for Ferrihydrite
|Health Warning:||No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.|
References for Ferrihydrite
American Mineralogist: 60: 485-486.
American Mineralogist: 75: 437.
American Mineralogist: 79: 767.
Izvestiya Akademii nauk SSSR (1973): (4): 23-33.
Clays and Clay Minerals: 36: 111-124.
Canadian Mineralogist: 28: 185-207.
Paktunc, D., Manceau, A., Dutrizac, J. (2013): Incorporation of Ge in ferrihydrite: Implications for the structure of ferrihydrite. American Mineralogist, 98, 848-858.
Internet Links for Ferrihydrite
Localities for Ferrihydrite
The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
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