The crystal structure of feitknechtite (β-MnOOH) and a new MnOOH polymorph

Studies suggest that feitknechtite (β-MnOOH) is a prevalent, and perhaps necessary, intermediate phase during the synthesis of birnessite-like phases, the abiotic oxidation of Mn2+, and the transformation of biogenic hexagonal phyllomanganates to more complex Mn oxides in laboratory and natural systems. Researchers have generally described feitknechtite as consisting of pyrochroite-like (or cadmium iodide-like) Mn-O octahedral layers, but a detailed crystal structure has not been reported. We used TEM/SAED and powder XRD and Rietveld refinements to derive the unit cell and, for the first time, report a complete structure description for feitknechtite (β-MnOOH). Rietveld refinements were also completed for three natural feitknechtite/hausmannite samples, and time-resolved synchrotron XRD experiments were used to follow the thermal transformation of feitknechtite to hausmannite. Additionally, we identified and report the structure for a second, and perhaps novel, MnOOH polymorph (proposed designation ϵ-MnOOH), mixed with the synthetic feitknechtite, that is similar to β-MnOOH but with a different layer stacking.

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Work Title The crystal structure of feitknechtite (β-MnOOH) and a new MnOOH polymorph
Access
Open Access
Creators
  1. Jeffrey E. Post
  2. Peter J. Heaney
  3. Eugene S. Ilton
  4. Evert J. Elzinga
Keyword
  1. Feitknechtite
  2. manganese oxide
  3. Beta-MnOOH
  4. Rietveld
  5. birnessite
License In Copyright (Rights Reserved)
Work Type Article
Publisher
  1. American Mineralogist
Publication Date November 1, 2023
Publisher Identifier (DOI)
  1. https://doi.org/10.2138/am-2022-8729
Deposited September 23, 2024

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Version 1
published

  • Created
  • Added Post_FeitknechtiteStructure_AmMin_2023.pdf
  • Added Chen_VacancyInfilling_AmMin_2023.pdf
  • Added Creator Jeffrey E. Post
  • Added Creator Peter J. Heaney
  • Added Creator Eugene S. Ilton
  • Added Creator Evert J. Elzinga
  • Published
  • Updated
  • Updated Keyword Show Changes
    Keyword
    • Feitknechtite, manganese oxide, Beta-MnOOH, Rietveld, birnessite
  • Deleted Chen_VacancyInfilling_AmMin_2023.pdf