CMMMech
CMMMech > Mineral > Feroxyhyte

Feroxyhyte mineral

Feroxyhyte is the iron(III) oxyhydroxide mineral species Fe3+O(OH), listed as approved with IMA number 1975-032 in the September 2026 IMA-CNMNC list. The curated experiment used chemically synthesized feroxyhyte, described as delta-prime FeOOH, rather than a natural ore. This mineral identity is distinct from other FeOOH polymorphs, elemental iron and the mixed secondary solids formed during the experiment. No constituent-element criticality or industrial recovery is inferred.

Identifiers & Classification

System Identifier Label
IMA IMA:1975-032 Feroxyhyte

Microbial & Biochemical Mechanisms (1)

Culture-associated feroxyhyte reduction and condition-dependent secondary minerals

redox transformation Microbial

Associated Organisms: Shewanella putrefaciens CN-32 (NCBITaxon:319224)

Laboratory cultures reported as S. putrefaciens CN32 produced acid-extractable Fe(II) from synthetic feroxyhyte and secondary solids assigned to magnetite and chukanovite without added phosphate. AQDS accelerated the initial Fe(II) increase without a reported significant increase in the final amount in phosphate-free cultures. Phosphate additions in AQDS-containing cultures slowed initial Fe(II) production and changed the later phase distribution; the high-phosphate treatment yielded green-rust and vivianite assignments. These observations support conditional reductive transformation, not complete conversion of every Fe(III) atom to Fe(II), a demonstrated gene pathway or isolated iron recovery.

Experimental Context & Analytical Limits:
Section 2.1 describes peroxide oxidation of synthetic Fe(OH)2 to feroxyhyte, followed by repeated washing, drying at 60 degrees C and grinding through a 200-mesh sieve; phase identity was checked by pXRD. Duplicate 160 mL serum bottles contained 100 mL defined mineral medium, 80 mM Fe(III) as feroxyhyte and 75 mM formate. Medium was adjusted to pH 7.5 before sterilization and addition of filter-sterilized reagents; this is not a controlled constant-pH trajectory. Inoculated bottles were argon-sparged and incubated on a roller drum at 30 degrees C in darkness. Late-log-phase cultures were added to approximately 5 x 10^9 cells/mL as printed. The 2021 paper delegates the complete basal-medium and inoculum preparation to earlier references; those inherited recipes were not reconstructed here. The named strain is mapped to CN-32, but Section 2.2 prints ATCC BAA-543 whereas the authority assigns CN-32 to BAA-453 and BAA-543 to Cellulomonas sp. ES5; this discrepancy remains an experimental-provenance limitation. Treatments were no added phosphate without or with 100 micromolar AQDS, and 500 micromolar or 5 mM phosphate with 100 micromolar AQDS. No phosphate-amended, AQDS-free arm was included. Total Fe(II) was measured by ferrozine after one-week HCl extraction of suspension, with extra acid for magnetite-containing samples; it is not dissolved Fe(II) alone. Anoxic handling, pXRD, SEM and selected Mossbauer fits characterized solids. Figure 23 includes a sterile-control diffraction trace, but a matched sterile Fe(II) time series and complete control amendment/time details are not supplied with these results.
Curated Evidence Points:
Section 3.7, Figure 22 and Table 4 show an early plateau near 24 mM acid-extractable Fe(II) in both phosphate-free cultures. Table 4 reports final values of 24.28 +/- 2.10 mM without AQDS and 24.51 +/- 6.02 mM with AQDS at day 78, approximately 30 percent of the initially supplied 80 mM Fe(III). The paper's description of essentially complete bioreduction within 11 days therefore cannot mean reduction of all initial Fe(III) to Fe(II). AQDS changes the initial rate, and Section 4.2 explicitly reports no significant final-extent difference for feroxyhyte. The fitted maximum sustained rates are not instantaneous rates or enzyme-specific measurements.
Figure 23 compares the sterile-control feroxyhyte pattern with inoculated solids assigned to magnetite and chukanovite in the phosphate-free and 500 micromolar phosphate treatments. At 5 mM phosphate the assigned products are carbonate green rust and vivianite. Figure 24 supplies morphology, not standalone phase proof; Table 4 marks the high-phosphate SEM green-rust assignment with a question mark and supplies no Mossbauer result for that arm. Table 5's selected AQDS and AQDS-plus-500-micromolar-phosphate fits support magnetite/chukanovite mixtures; their relative spectral areas are not whole-feed mass recovery percentages.
Table 4 reports 55.07 +/- 2.92 and 59.93 +/- 1.65 mM final Fe(II) at day 156 for the 500 micromolar and 5 mM phosphate treatments, respectively. These longer-duration endpoints must not be treated as a same-day comparison with day-78 phosphate-free endpoints. Figure 23 labels the actual plotted patterns as day 78 or day 156, consistent with Table 4, while its caption says 46 days. That unresolved caption conflict is retained rather than assigning a fabricated common harvest date. No residual feroxyhyte was identified in the inoculated diffraction patterns, but nondetection and mixed Fe(II)/Fe(III) products do not establish total iron reduction or a quantitative pure-phase yield.
Sterile-control diffraction supports retention of the starting phase under one control condition; the absence of a reported matched sterile Fe(II) trajectory and fully specified control arms limits quantification of the microbial increment. No killed-cell, cell-free metabolite or mutant comparison resolves biological necessity or a particular electron-transfer pathway. Dissolution-reprecipitation is inferred from changed morphology in Section 4.1, not directly traced. All phosphate arms also contain AQDS, so phosphate effects cannot be generalized to shuttle-free systems. The study demonstrates laboratory solid transformation, with no isolated iron product, natural-ore performance or industrial deployment established.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. PDF page 68, Feroxyhyte row; page 1 column and approval-status definitions.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14)
  2. oloughlin_2021: O'Loughlin, Boyanov, Gorski, Scherer and Kemner (2021). Effects of Fe(III) Oxide Mineralogy and Phosphate on Fe(II) Secondary Mineral Formation during Microbial Iron Reduction. Minerals 11(2):149. DOI 10.3390/min11020149. Complete 43-page original publisher PDF; Sections 2.1-2.3, 3.7 and 4.1-4.4; Figures 22-24 and Tables 4-5.
    https://doi.org/10.3390/min11020149 (accessed 2026-10-14)
  3. ncbi_cn32: NCBI Taxonomy 319224, Shewanella putrefaciens CN-32. Named-strain identity; equivalent names include Shewanella putrefaciens strain CN-32. This does not authenticate the experimental stock.
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=319224 (accessed 2026-10-14)
  4. atcc_cn32: ATCC BAA-453, Shewanella putrefaciens, strain designation CN-32 [OCM 576, SMCC 576W]. Resolves the collection identifier for the named strain, unlike the BAA-543 number printed in the experimental paper.
    https://www.atcc.org/products/baa-453 (accessed 2026-10-14)
  5. atcc_baa543: ATCC BAA-543, Cellulomonas sp., strain ES5. Authority evidence that the BAA-543 identifier printed beside CN32 in the paper refers to a different organism; the experimental stock cannot be independently authenticated from that conflicting citation.
    https://www.atcc.org/products/baa-543 (accessed 2026-10-14)

Curation History

Timestamp Curator Action Summary
2026-10-14T06:28:06Z codex created Added species-grounded feroxyhyte with conditional CN32 culture-associated reduction from the complete 2021 original. Preserved sterile-XRD versus unreported kinetic controls, partial Fe(III) reduction, unlike endpoints, caption and strain-accession conflicts, and phase-identification limits.

Record source: data/records/feroxyhyte.yaml