Iron element Critical Material
The element Fe, distinct from its dissolved ions, iron-bearing minerals, alloys, and ore grades. The UK designation maps to the explicitly named iron entry in the government's technical annex; it does not designate every Fe-bearing compound or Canada's separate high-purity iron ore commodity.
Identifiers & Classification
| System | Identifier | Label |
|---|---|---|
| CHEBI |
CHEBI:18248
|
iron atom |
Criticality Designations
| Jurisdiction | List Name | Edition / Document | Classification | Source |
|---|---|---|---|---|
| United Kingdom | Department for Business and Trade Critical Minerals technical annex, Annex 1 | 23 January 2026 update; list sourced from CMIC 2024 Criticality Assessment | critical |
uk2026
|
Microbial & Biochemical Mechanisms (1)
Ferrihydrite reduction and magnetite-rich mineral formation by strain Ax17
biomineralization
Microbial
Associated Organisms:
Desulfovulcanus ferrireducens (NCBITaxon:2831190)
Growing Desulfovulcanus ferrireducens Ax17 (DSM 111878) reduced synthetic two-line nanophase ferrihydrite and produced a black magnetic solid interpreted from complementary analyses as primarily cation-deficient magnetite. This is microbial Fe redox transformation with secondary mineral formation, not elemental iron production or a purified recovery product. The taxon identifier is species-level; the paper and DSMZ identify the experimental strain.
Experimental Context & Analytical Limits:
Laboratory triplicates used 50 mL modified DSM 981 medium in 160 mL serum bottles, reported 100 mmol/L ferrihydrite, initial pH 6.80 +/- 0.05, 0.5 mM cysteine-HCl, and 1.3 mM FeCl2 supplementation. The headspace was H2:CO2 (80:20) at 200 kPa; cultures received a 1% logarithmic-phase inoculum previously transferred at least three times on the acceptor, and grew at 55 degrees C for about five days. Identically composed uninoculated controls were incubated at 55 degrees C or room temperature. Ferrozine after oxalate dissolution gave reported Fe(II) of 24 mM in the biotic medium versus 2-3 mM in controls; this extraction-based measurement is not a dissolved-iron concentration or a recovery percentage. No pilot, industrial, or natural-ore extraction operation was tested.
Laboratory triplicates used 50 mL modified DSM 981 medium in 160 mL serum bottles, reported 100 mmol/L ferrihydrite, initial pH 6.80 +/- 0.05, 0.5 mM cysteine-HCl, and 1.3 mM FeCl2 supplementation. The headspace was H2:CO2 (80:20) at 200 kPa; cultures received a 1% logarithmic-phase inoculum previously transferred at least three times on the acceptor, and grew at 55 degrees C for about five days. Identically composed uninoculated controls were incubated at 55 degrees C or room temperature. Ferrozine after oxalate dissolution gave reported Fe(II) of 24 mM in the biotic medium versus 2-3 mM in controls; this extraction-based measurement is not a dissolved-iron concentration or a recovery percentage. No pilot, industrial, or natural-ore extraction operation was tested.
Curated Evidence Points:
Support
Source:
sklute2023
Methods and Results, Cell growth on ferrihydrite, link Ax17 growth, greater oxalate-extractable Fe(II), and the magnetic product to the inoculated treatment. Figures 1A, 2-4 and Supplementary Figures S2-S5 compare controls and mineral standards using reflectance, FTIR-ATR, Mossbauer spectroscopy, XRD, and TEM with electron diffraction.
Partial
Source:
sklute2023
This supports a magnetite-rich mixed product, not pure stoichiometric magnetite or uniquely biological magnetite formation. Low-temperature Mossbauer spectra exclude a pure magnetite product; XRD alone cannot distinguish magnetite, maghemite, and cation-deficient magnetite. The heated abiotic control formed lepidocrocite and may contain minor magnetite. Cysteine and added Fe(II) were present in all arms. Akaganeite and lepidocrocite treatments gave different, nonmagnetic poorly resolved products, limiting extrapolation across iron minerals.
Sources & References
-
chebi_iron: ChEBI CHEBI:18248 - iron atom; atomic number 26, formula Fe
https://www.ebi.ac.uk/chebi/CHEBI:18248 (accessed 2026-10-11) -
uk2026: UK Department for Business and Trade. Critical Minerals technical annex, updated 23 January 2026. Annex 1, Complete list of UK critical minerals, sourced from the CMIC 2024 Criticality Assessment; iron entry.
https://www.gov.uk/government/publications/uk-critical-minerals-strategy/critical-minerals-technical-annex (accessed 2026-10-11) -
sklute2023: Sklute et al. (2023). Fe(III) (oxyhydr)oxide reduction by the thermophilic iron-reducing bacterium Desulfovulcanus ferrireducens. Frontiers in Microbiology 14:1272245. Methods, ferrihydrite Results, Figures 1-4, and Supplementary Figures S2-S5.
https://doi.org/10.3389/fmicb.2023.1272245 (accessed 2026-10-11) -
ncbi_ferrireducens: NCBI Taxonomy 2831190 - Desulfovulcanus ferrireducens; species rank
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=2831190 (accessed 2026-10-11) -
dsm_ax17: DSMZ DSM 111878 - Desulfovulcanus ferrireducens, type strain Ax17
https://www.dsmz.de/collection/catalogue/details/culture/DSM-111878 (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T05:19:08Z |
Codex (GPT-6; Codex) | record_creation | Created elemental iron with verified identity, dated UK criticality, and Ax17 ferrihydrite biomineralization evidence. Preserved mixed-product, abiotic-control, assay-fraction, and laboratory-scale limits. Independent scientific review is separate. |
Record source: data/records/iron.yaml