Zinc element Critical Material
Zinc (Zn), atomic number 30. The zinc-atom identifier grounds this element record, not dissolved Zn(II), zinc sulfide, sphalerite, or a zinc concentrate. The United States designation maps the listed zinc commodity to this element; it does not designate every zinc-bearing mineral or waste. The curated experiments concern laboratory dissolution of a sphalerite concentrate.
Identifiers & Classification
| System | Identifier | Label |
|---|---|---|
| CHEBI |
CHEBI:27363
|
zinc atom |
Criticality Designations
| Jurisdiction | List Name | Edition / Document | Classification | Source |
|---|---|---|---|---|
| United States of America | USGS Final List of Critical Minerals | 2025; Federal Register 90:50494-50497; published 7 November 2025 | critical |
usgs_2025
|
Microbial & Biochemical Mechanisms (1)
Conditional enhancement of sphalerite-concentrate dissolution
bioleaching
Microbial
Associated Organisms:
Acidithiobacillus ferrooxidans (NCBITaxon:920)
Living Thiobacillus ferrooxidans FC1, using the paper's historical name, increased zinc dissolution relative to matched chemical controls at elevated ferrous concentrations after an initial period without an advantage. Surface analyses and kinetic modeling support sulfur-layer removal as the explanation; they do not establish a specific enzyme or direct biological oxidation of the ZnS lattice.
Experimental Context & Analytical Limits:
Gamsberg concentrate, reported as 98% sphalerite by XRD and 53.3% Zn, was milled to 45-53 micrometres and washed with 0.5 M sodium sulfide. The aerated, stirred laboratory electrolysis cell had a 2 L working volume, 5 g concentrate/L, 10% v/v inoculum, pH 1.6, 35 degrees C and dissolved oxygen 5.9 mg/L. Redox control maintained dissolved iron conditions; 1999 experiments held Fe(III) at 1 g/L while varying Fe(II). Zinc was assayed in 0.45-micrometre filtrate by atomic spectrophotometry. This is dissolution, not isolated zinc-product recovery or deployment. Analytical repeatability replicates do not establish biological replication. NCBITaxon:920 maps the published species name, not a verified strain accession or modern genomic reassignment of FC1.
Gamsberg concentrate, reported as 98% sphalerite by XRD and 53.3% Zn, was milled to 45-53 micrometres and washed with 0.5 M sodium sulfide. The aerated, stirred laboratory electrolysis cell had a 2 L working volume, 5 g concentrate/L, 10% v/v inoculum, pH 1.6, 35 degrees C and dissolved oxygen 5.9 mg/L. Redox control maintained dissolved iron conditions; 1999 experiments held Fe(III) at 1 g/L while varying Fe(II). Zinc was assayed in 0.45-micrometre filtrate by atomic spectrophotometry. This is dissolution, not isolated zinc-product recovery or deployment. Analytical repeatability replicates do not establish biological replication. NCBITaxon:920 maps the published species name, not a verified strain accession or modern genomic reassignment of FC1.
Curated Evidence Points:
Support
Source:
fowler_crundwell_1999
Methods and Figures 2-6 compare inoculated and microscopy-checked sterile runs. Dissolution diverged after approximately 8-12 h; surface comparisons at Fe(II) 4 g/L after 100 h and 8 g/L after 69 h support the authors' sulfur-removal interpretation. No recovery percentage is inferred from the plots.
Partial
Source:
fowler_crundwell_1999
Figures 2-3 include a 1 g/L Fe(II) series whose paired data appear inconsistent with the Discussion's sharp low-ferrous null boundary. A universal 1 g/L threshold is therefore not curated. Shrinking-core fits and SEM/EDAX are mechanistic support, not enzyme assays, sulfur mass balance, or independent process replication.
Partial
Source:
fowler_crundwell_1998
Methods and Figures 4-6 report similar zinc dissolution with FC1 and sterile controls when Fe(II) was held at 1 g/L and Fe(III) varied, at pH 1.6, 35 degrees C and 5 g concentrate/L. Bacterial iron oxidation and surface attachment occurred, but no additional dissolution was demonstrated under those conditions. This bounds the later enhancement claim; neither study justifies a universal direct bacterial leaching mechanism.
Sources & References
-
chebi_zinc: ChEBI CHEBI:27363 — zinc atom
https://www.ebi.ac.uk/chebi/CHEBI:27363 (accessed 2026-10-11) -
usgs_2025: USGS (2025). Final 2025 List of Critical Minerals. Federal Register 90:50494-50497, document 2025-19813; zinc commodity row.
https://www.govinfo.gov/content/pkg/FR-2025-11-07/html/2025-19813.htm (accessed 2026-10-11) -
fowler_crundwell_1999: Fowler TA and Crundwell FK (1999). Leaching of Zinc Sulfide by Thiobacillus ferrooxidans: Bacterial Oxidation of the Sulfur Product Layer Increases the Rate of Zinc Sulfide Dissolution at High Concentrations of Ferrous Ions. Applied and Environmental Microbiology 65:5285-5292. doi:10.1128/AEM.65.12.5285-5292.1999. Methods; Figures 2-6; Discussion.
https://doi.org/10.1128/AEM.65.12.5285-5292.1999 (accessed 2026-10-11) -
fowler_crundwell_1998: Fowler TA and Crundwell FK (1998). Leaching of Zinc Sulfide by Thiobacillus ferrooxidans: Experiments with a Controlled Redox Potential Indicate No Direct Bacterial Mechanism. Applied and Environmental Microbiology 64:3570-3575. doi:10.1128/AEM.64.10.3570-3575.1998. Methods; Figures 4-6; Results and Discussion.
https://doi.org/10.1128/AEM.64.10.3570-3575.1998 (accessed 2026-10-11) -
taxonomy_ferrooxidans: NCBI Taxonomy 920 — Acidithiobacillus ferrooxidans, species rank; Thiobacillus ferrooxidans basionym.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=920&mode=Info (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T04:20:59Z |
codex (GPT-6) | CREATE | Added zinc identity and dated US criticality with controlled FC1 sphalerite-leaching evidence, the primary low-ferrous null result, figure/prose uncertainty, and explicit laboratory recovery limits. |
Record source: data/records/zinc.yaml