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Voltaite mineral

Voltaite is a cubic mixed-valence iron sulfate mineral with the September 2026 IMA ideal formula K2Fe(II)5Fe(III)3Al(SO4)12(H2O)18. This species is distinct from the voltaite mineral group, tetragonal pertlikite and the magnesium-, zinc- or ammonium-dominant analogues. Zhitova et al. (2023) characterized two samples labelled voltaite: Ni4225 from a coal-fire pseudofumarole in Nikitovka and SCCIII-14-20s from the Bolshoi Semiachik geothermal field. Their selected crystals were refined in cubic Fd-3c at 293 K, without clear evidence of lowered symmetry. The surrounding assemblages include other sulfates and are not pure voltaite feeds. Composition was measured by EDS on beam-sensitive hydrated grains; Fe(II)/Fe(III) proportions were calculated by charge balance, water was assigned from stoichiometry, and totals for these unpolished samples were normalized. Table 4 gives approximately one monovalent cation per formula unit for these samples, whereas the ideal formula and fully occupied structural A site imply two; this unresolved analytical/refinement discrepancy is not silently corrected. SCCIII-14-20s is also close to the Fe/Mg species boundary. These observations support a qualified natural-specimen identity record, without transferring every sample composition to ideal voltaite or treating geological occurrence as a controlled formation experiment. No microbial mechanism, extraction, recovery yield, industrial deployment or criticality designation is curated.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026; Voltaite row on PDF page 230 and field definitions on pages 1-2. Grandfathered status G; 1841 is the original-description year, not an IMA approval number. Current ideal formula includes Al.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15)
  2. zhitova2023: Zhitova, E. S. et al. (2023). The Crystal Chemistry of Voltaite-Group Minerals from Post-Volcanic and Anthropogenic Occurrences. Symmetry 15, 2126. Complete fourteen-page original; specimen provenance section 2.1, methods section 2.2, Tables 1-4 and Figures 1-5. Only Ni4225 and SCCIII-14-20s are labelled voltaite; the other group species are not pooled. Table 4's estimated oxidation-state/water values and near-equal Fe/Mg ratio require qualification. Al-bound water disorder prevents refining all hydrogen positions. Estimated formation temperatures are field interpretation, not a measured synthesis protocol. The CIF deposit numbers reported on page 12 were not acquired or independently re-refined in this curation.
    https://doi.org/10.3390/sym15122126 (accessed 2026-10-15)
  3. zhitova2023_pdf: Official publisher PDF of Zhitova et al. (2023), fourteen pages, published November 29, 2023. Same study as zhitova2023, not independent replication. Table 4 prints SKCIII in a footnote while tables and specimen discussion use SCCIII; that spelling difference is not evidence of another specimen.
    https://mdpi-res.com/d_attachment/symmetry/symmetry-15-02126/article_deploy/symmetry-15-02126.pdf (accessed 2026-10-15)
  4. handbook_voltaite: Handbook of Mineralogy. Voltaite, version 1 (2001-2005), complete one-page entry. Historical cubic mineral description and variable Fe(III)/Al formula; its Fe(III)-only calculated composition is not substituted for the September 2026 IMA Al-bearing ideal formula or presented as a new natural assay.
    https://handbookofmineralogy.org/pdfs/voltaite.pdf (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T18:27:58Z codex (GPT-6; codex) CREATE Created a species-specific natural-crystal identity record, retaining calculated chemistry, near-boundary composition and inconsistent monovalent-site accounting; deferred unavailable synthesis evidence.

Record source: data/records/voltaite.yaml