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Kozulite, an Mn-rich alkali amphibole.

ABSTRACT: The crystal structure of kôzulite, an Mn-rich alkali amphibole with the ideal formula NaNa(2)[Mn(4) (2+)(Fe(3+),Al)]Si(8)O(22)(OH)(2), tris-odium tetra-manganese iron/aluminium octa-silicate dihydroxide, was refined from a natural specimen with composition (K(0.20)Na(0.80))(Na(1.60)Ca(0.18)Mn(2+) (0.22))(Mn(2+) (2.14)Mn(3+) (0.25)Mg(2.20)Fe(3+) (0.27)Al(0.14))(Si(7.92)Al(0.06)Ti(0.02))O(22)[(OH)(1.86)F(0.14)]. The site occupancies determined from the refinements are M1 = 0.453?(1) Mn + 0.547?(1) Mg, M2 = 0.766?(1) Mn + 0.234?(1) Mg, and M3 = 0.257?(1) Mn + 0.743?(1) Mg, where Mn and Mg represent (Mn+Fe) and (Mg+Al), respectively. The average M-O bond lengths are 2.064?(1), 2.139?(1), and 2.060?(1)?Å for the M1, M2, and M3 sites, respectively, indicating the preference of large Mn(2+) for the M2 site. Four partially occupied amphibole A sites were revealed from the refinement, with A(m) = 0.101?(4)?K, A(m)' = 0.187?(14) Na, A(2) = 0.073?(6) Na, and A(1) = 0.056?(18) Na, in accord with the result derived from microprobe analysis (0.20?K + 0.80 Na), considering experimental uncertainties.

SUBMITTER: Barkley MC

PROVIDER: S-EPMC3011386 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Kôzulite, an Mn-rich alkali amphibole.

Barkley Madison C MC Yang Hexiong H Downs Robert T RT

Acta crystallographica. Section E, Structure reports online 20101117 Pt 12

The crystal structure of kôzulite, an Mn-rich alkali amphibole with the ideal formula NaNa(2)[Mn(4) (2+)(Fe(3+),Al)]Si(8)O(22)(OH)(2), tris-odium tetra-manganese iron/aluminium octa-silicate dihydroxide, was refined from a natural specimen with composition (K(0.20)Na(0.80))(Na(1.60)Ca(0.18)Mn(2+) (0.22))(Mn(2+) (2.14)Mn(3+) (0.25)Mg(2.20)Fe(3+) (0.27)Al(0.14))(Si(7.92)Al(0.06)Ti(0.02))O(22)[(OH)(1.86)F(0.14)]. The site occupancies determined from the refinements are M1 = 0.453 (1) Mn + 0.547 (1) ...[more]

PMID: 21589206

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Project description:UnlabelledThe mechanisms, key organisms, and geochemical significance of biological low-pH Mn(II) oxidation are largely unexplored. Here, we investigated the structure of indigenous Mn(II)-oxidizing microbial communities in a secondary subsurface Mn oxide deposit influenced by acidic (pH 4.8) metal-rich groundwater in a former uranium mining area. Microbial diversity was highest in the Mn deposit compared to the adjacent soil layers and included the majority of known Mn(II)-oxidizing bacteria (MOB) and two genera of known Mn(II)-oxidizing fungi (MOF). Electron X-ray microanalysis showed that romanechite [(Ba,H2O)2(Mn(4+),Mn(3+))5O10] was conspicuously enriched in the deposit. Canonical correspondence analysis revealed that certain fungal, bacterial, and archaeal groups were firmly associated with the autochthonous Mn oxides. Eight MOB within the Proteobacteria, Actinobacteria, and Bacteroidetes and one MOF strain belonging to Ascomycota were isolated at pH 5.5 or 7.2 from the acidic Mn deposit. Soil-groundwater microcosms demonstrated 2.5-fold-faster Mn(II) depletion in the Mn deposit than adjacent soil layers. No depletion was observed in the abiotic controls, suggesting that biological contribution is the main driver for Mn(II) oxidation at low pH. The composition and species specificity of the native low-pH Mn(II) oxidizers were highly adapted to in situ conditions, and these organisms may play a central role in the fundamental biogeochemical processes (e.g., metal natural attenuation) occurring in the acidic, oligotrophic, and metalliferous subsoil ecosystems.ImportanceThis study provides multiple lines of evidence to show that microbes are the main drivers of Mn(II) oxidation even at acidic pH, offering new insights into Mn biogeochemical cycling. A distinct, highly adapted microbial community inhabits acidic, oligotrophic Mn deposits and mediates biological Mn oxidation. These data highlight the importance of biological processes for Mn biogeochemical cycling and show the potential for new bioremediation strategies aimed at enhancing biological Mn oxidation in low-pH environments for contaminant mitigation.

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Kozulite, an Mn-rich alkali amphibole.

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Kôzulite, an Mn-rich alkali amphibole.

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