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Riebeckite mineral

Riebeckite is the sodium-iron amphibole species with IMA formula vacancy-Na2(Fe(II)3Fe(III)2)Si8O22(OH)2, redefined under the 2012 special procedure in the September 2026 IMA list. Crocidolite denotes its asbestiform variety; this record does not equate every riebeckite specimen with an asbestos feed, elemental iron, or an asbestos-containing waste. The reviewed laboratory assay used UICC crocidolite reference material as supplied. No criticality designation is inherited from its constituents.

Microbial & Biochemical Mechanisms (1)

Culture-associated iron reduction in UICC crocidolite

redox transformation Microbial

Associated Organisms: Deferrisoma palaeochoriense (NCBITaxon:1573172)

Deferrisoma palaeochoriense growth with a crocidolite feed was accompanied by increased acid-extractable Fe(II) relative to Fe(III) and a transient increase in dissolved iron over uninoculated controls. These laboratory observations support microbial iron reduction associated with this feed. Whether the reactive iron was structural or in a surface coating, and how electrons reached it, remain unresolved.

Experimental Context & Analytical Limits:
Choi et al. used 10 g/L UICC crocidolite as supplied, 25 mL modified DSM 1210 medium, 60 degrees C, pH 6.1-6.4, 1.5 wt% NaCl and H2/CO2 (80:20 by volume, 0.2 MPa) for one week in triplicate. Hydrogen was the electron donor and carbon dioxide the carbon source. The positive comparator contained poorly crystalline Fe(OH)3; triplicate uninoculated mineral-medium controls were included. Strain provenance is not independently authenticated here. Methods distinguish centrifuged, 0.2-micrometre-filtered ICP-OES/ferrozine samples from unfiltered samples subjected to an 8-hour HCl extraction. The extraction reports reagent concentration as 12 N HCl added 1:1; it is an analytical extraction, not the culture medium or an isolated recovery process.
Curated Evidence Points:
Results, Figures 1A/C and 2A show growth, increased Fe(II) in the acid-extractable fraction and higher dissolved iron in inoculated crocidolite bottles than medium-only bottles. Dissolved iron peaks and then declines. Acid-extractable Fe(II)/total-Fe fractions are not percentages of iron recovered from the feed.
Discussion and Figures 3A-C preserve crystallinity and grain boundaries; occasional surface amorphous material leaves structural versus coating-associated reduction unresolved. Figure 4C does not show appreciable iron in mapped biomass. Long-range electron transfer, substitutions and reintroduction of dissolved iron into the mineral are proposals. Methods describe negative-control subtraction for ICP-OES while also displaying medium-only series; the exact subtraction basis is unresolved. The unavailable supplement contains detailed recipes, tables and extraction/beam-control checks, so no precise extraction yield, rate advantage or complete mass balance is adopted. Neither fibre destruction, detoxification, purified-metal recovery nor industrial deployment is demonstrated.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026; pages 1-2 definitions, Chrysotile row PDF page 45 and Riebeckite row PDF page 185.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14)
  2. riebeckite_handbook: Handbook of Mineralogy, Riebeckite, version 1.2 (2001), page 1 Occurrence: asbestiform crocidolite; current formula/status taken from IMA rather than the older handbook.
    https://www.handbookofmineralogy.org/pdfs/riebeckite.pdf (accessed 2026-10-14)
  3. choi2023: Choi, Vigliaturo, Giere and Perez-Rodriguez (2023). Microbe-Mineral Interactions between Asbestos and Thermophilic Chemolithoautotrophic Anaerobes. Applied and Environmental Microbiology 89(6):e02048-22. DOI 10.1128/aem.02048-22; complete PMC main text and Figures 1-4 inspected; supplement not acquired.
    https://doi.org/10.1128/aem.02048-22 (accessed 2026-10-14)
  4. ncbi_deferrisoma: NCBI Taxonomy 1573172, Deferrisoma palaeochoriense, species; official taxonomy XML checked 14 October 2026. This species identifier does not authenticate the experimental culture at strain rank.
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=1573172&mode=Info (accessed 2026-10-14)

Curation History

Timestamp Curator Action Summary
2026-10-14T09:21:29.026997+00:00 codex (GPT-6; codex) CREATE Created mineral species record from primary thermophile assay evidence, with control outcomes, preparation limits and unresolved supplementary-data questions.

Record source: data/records/riebeckite.yaml