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Schwertmannite, a new iron oxyhydroxysulphate from Pyhäsalmi, Finland, and other localities

  • J. M. Bigham (a1), L. Carlson (a2) and E. Murad (a3)

Schwertmannite is a new oxyhydroxysulphate of iron from the Pyhäisalmi sulphide mine, Province of Oulu, Finland. It occurs there, and elsewhere, as an ochreous precipitate from acid, sulphate-rich waters. Associated minerals at other localities may include jarosite, natrojarosite, goethite and ferrihydrite. Schwertmannite is a poorly crystalline, yellowish brown mineral with a fibrous morphology under the electron microscope. A high specific surface area in the range of 100 to 200 m2/g, rapid dissolution in cold, 5 M HCl or in ammonium oxalate at pH 3, and pronounced X-ray diffraction line broadening are consistent with its poorly crystalline character.

Colour parameters for the type specimen as related to CIE illuminant C are L* = 53.85, a* = + 15.93, and b* = +47.96. Chemical analysis gives Fe2O3, 62.6; SO3, 12.7; CO2, 1.5; H2O, 10.2; H2O+, 12.9; total 99.9 wt.%. These data yield an empirical unit cell formula of Fe16O16(OH)9.6(SO4)3.2·10H2O after exclusion of CO2 and H2O. The most general simplified formula is Fe16O16(OH)y(SO4)z·nH2O, where 16 − y = 2z and 2.0 ⩽ z ⩽ 3.5. Schwertmannite has a structure akin to that of akaganéite (nominally β-FeOOH) with a doubled c dimension. Its X-ray powder diffraction pattern consists of eight broad peaks [dobs in (Iobs) (hkl)] 4.86(37)(200,111); 3.39(46)(310); 2.55(100)(212); 2.28(23)(302); 1.95(12)(412); 1.66(21)(522); 1.51(24)(004); and 1.46(18)(204,542), giving a = 10.66(4), c = 6.04(1) Å, and V = 686(6) Å3 for a primitive, tetragonal unit cell. The probable space group is P4/m. Upon heating, schwertmannite transforms to hematite with Fe2(SO4)3 occurring as an intermediate phase. Bidentate bridging complexes between Fe and SO4 are apparent in infrared spectra. Mössbauer data show the Fe in schwertmannite to be exclusively trivalent and in octahedral coordination; it has a Néel temperature of 75 ± 5 K and a saturation magnetic hyperfine field of about 45.6 T. Pronounced asymmetry of the Mössbauer spectra indicates different locations for Fe atoms relative to SO4 groups in the structure. The name is for Udo Schwertmann, professor of soil science at the Technical University of Munich.

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Bigham, J. M., Schwertmann, U., Carlson, L. and Murad, E. (1990) A poorly crystallized oxyhy-droxysulfate of iron formed by bacterial oxidation of Fe(II) in acid mine waters. Geochim. Cosmo-chim. Ada, 54, 2743–58.
Bigham, J. M., Schwertmann, U. and Carlson, L. (1992) Mineralogy of precipitates formed by the biogeochemical oxidation of Fe(II) in mine drainage. In: Biomineralization processes of iron and manganese: modern and ancient environments (H. C. W. Skinner and R. W. Fitzpatrick, eds.), Catena Supplement 21, Catena-Verlag, Cremlin-gen-Destedt, 219-32.
Brady, K. S., Bigham, J. M., Jaynes, W. F. and Logan, T. J. (1986) Influence of sulfate on Fe-oxide formation: comparisons with a stream receiving acid mine drainage. Clays Clay Minerals, 34, 266–74.
Commission Internationale de l'Eclairage (1978) Recommendations on uniform colour spaces, col-our difference and psychometric colour terms. Publ. 15, Suppl. 2, Colourimetry. CIE 1971, Paris.
Fanning, D. S., Rabenhorst, M. C. and Bigham, J. M. (1993) Colors of acid sulfate soils. In: Soil color (J. M. Bigham and E. J. Ciolkosz, eds.), Soil Sci. Soc. Am. Spec. Pub. 31, p. 91-108.
Fitzpatrick, R. W., Naidu, R. and Self, P. G. (1992) Iron deposits and microorganisms in saline sulfidic soils with altered soil water regimes in South Australia. In: Biomineralization processes of iron and manganese: modern and ancient environments (H. C. W. Skinner and R. W. Fitzpatrick, eds.), Catena Supplement 21, Catena-Verlag, Cremlingen-Destedt, 263-86.
Janik, L. M. and Raupach, M. (1977) An iterative, least-squares program to separate infrared absorption spectra into their component bands. CSIRO Div. Soils Tech. Paper 35, 1–37.
Lazaroff, N., Sigal, W. and Wasserman, A. (1982) Iron oxidation and precipitation of ferric hydro-xysulphates by resting Thiobacillus ferrooxidans cells. Appl. Environ. Microbiol., 43, 924–38.
Lazaroff, N., Melanson, L., Lewis, E., Santoro, N. and Pueschel, C. (1985) Scanning electron micro-scopy and infrared spectroscopy of iron sediments formed by Thiobacillus ferrooxidans. Geomicro-biol. J., 4, 231–68.
Murad, E. (1988) The Mossbauer spectrum of ‘welT-crystallized ferrihydrite. J. Magnetism Magnetic Mater., 74, 153–7.
Murad, E., Bigham, J. M., Bowen, L. H. and Schwertmann, U. (1990) Magnetic properties of iron oxides produced by bacterial oxidation of Fe2+ under acid conditions. Hyperfine Interactions, 58, 2373–6.
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Mineralogical Magazine
  • ISSN: 0026-461X
  • EISSN: 1471-8022
  • URL: /core/journals/mineralogical-magazine
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