Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely used by humans, e.g., as iron ores, pigments, catalysts, in thermite (see the diagram) and hemoglobin. Common rust is a form of iron(III) oxide. Iron oxides are widely used as inexpensive, durable pigments in paints, coatings and colored concretes. Colors commonly available are in the "earthy" end of the yellow/orange/red/brown/black range. When used as a food coloring, it has E number E172.
- iron(II) oxide, wüstite (FeO)
- iron(II,III) oxides:
- iron(III) oxide (Fe2O3)
- goethite (α-FeOOH),
- akaganéite (β-FeOOH),
- lepidocrocite (γ-FeOOH),
- feroxyhyte (δ-FeOOH),
- ferrihydrite ( approx.), or , better recast as
- high-pressure FeOOH
- schwertmannite (ideally or )
- green rust ( where A− is Cl− or 0.5SO42−)
Several species of bacteria, including Shewanella oneidensis, Geobacter sulfurreducens and Geobacter metallireducens metabolically utilize solid iron oxides as a terminal electron acceptor, reducing Fe(III) oxides to Fe(II) containing oxides.
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- http://www.mindat.org/min-7281.html Mindat
- Bretschger, O.; Obraztsova, A.; Sturm, C. A.; Chang, I. S.; Gorby, Y. A.; Reed, S. B.; Culley, D. E.; Reardon, C. L.; Barua, S.; Romine, M. F.; Zhou, J.; Beliaev, A. S.; Bouhenni, R.; Saffarini, D.; Mansfeld, F.; Kim, B.-H.; Fredrickson, J. K.; Nealson, K. H. (20 July 2007). "Current Production and Metal Oxide Reduction by Shewanella oneidensis MR-1 Wild Type and Mutants". Applied and Environmental Microbiology. 73 (21): 7003–7012. doi:10.1128/AEM.01087-07.
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