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Jarosite mineral

Jarosite is the potassium ferric hydroxysulfate mineral with ideal formula KFe3(SO4)2(OH)6, with all three iron atoms ferric. The September 2026 IMA list records the species as redefined, 1987 s.p. This record denotes K-jarosite, not the broader jarosite family, natrojarosite, ammoniojarosite, hydroniumjarosite, elemental iron or an industrial jarosite-bearing waste. The experiment below uses a laboratory biosynthesized potassium-jarosite preparation whose bulk composition differs from the ideal endmember. No constituent-element criticality or commercial recovery status is inferred.

Microbial & Biochemical Mechanisms (1)

Culture-associated reductive dissolution with inorganic sulfur donors

redox transformation Microbial

Associated Organisms: Acidithiobacillus thiooxidans (NCBITaxon:930)

Acidithiobacillus thiooxidans DSM 504 cultures showed greater dissolved-iron release and Fe(II) accumulation from biosynthesized potassium jarosite than uninoculated controls supplied with the same sulfur donor. Sulfite gave the largest reported dissolution, followed by thiosulfate and elemental sulfur. The authors interpret this as dissimilatory iron reduction coupled to sulfur oxidation. The maintained claim is culture-associated reduction and dissolution; direct enzymatic reduction, growth by ferric-iron respiration and an exclusive electron-transfer pathway are not established.

Experimental Context & Analytical Limits:
The potassium-jarosite feed was prepared in a separate Acidianus manzaensis culture at 65 degrees C and 180 rpm, using 100 mL basal medium in 250 mL flasks, initially pH 2.0 plus or minus 0.05, with 0.2 M FeSO4 and 0.067 M K2SO4. After approximately six days the precipitate was filtered, washed with deoxygenated ultrapure water and vacuum dried at 30 degrees C. Dissolution assays used 0.5 g feed in 50 mL sterile basal salts medium in 150 mL serum bottles, initial pH 1.94 plus or minus 0.05, and elemental sulfur, Na2S2O3 or Na2SO3 supplied at an equivalent sulfur concentration of 10 g/L. Inoculated bottles began at 4 x 10^8 cells/mL; each donor had an uninoculated sterile control. Bottles were sealed with butyl stoppers and flushed for approximately 20 minutes with N2/CO2 at 80/20 by volume, then shaken at 30 degrees C and 180 rpm for up to 34 days. Assays were in duplicate and sampled every two to four days. These are nominally anaerobic laboratory batches; a measured dissolved-oxygen time course, killed-cell control and cell-free culture-filtrate comparison are not reported.
Curated Evidence Points:
Methods 2.2, Table 1 and Figure 1 support the prepared feed's potassium-jarosite assignment through XRD comparison with PDF 71-1777, SEM morphology and elemental analysis. Table 1 reports Fe 31.23%, K 5.33% and S 12.11%, compared with ideal reference values 33.45%, 7.78% and 12.81%. The near-ideal Fe/S molar ratio does not establish endmember stoichiometry or quantitative phase purity; potassium is lower than in the ideal reference. The study does not resolve all possible substitutions or amorphous fractions. This is not a sampled industrial residue.
Figure 2 shows donor-dependent dissolved total iron and Fe(II) accumulation in inoculated assays, with the sulfite arm highest. Methods 2.4 measure dissolved total and ferric iron by the sulfosalicylic acid method; Fe(II) is calculated as their difference, not measured by an independent ferrous assay. Supplementary Figures S2-S3 show substantially lower but nonzero iron release in uninoculated controls. These comparisons support a culture-associated enhancement under the reported conditions.
The exact final sulfite percentage is internally inconsistent. Section 3.2, manuscript line 246, states 96.4% after 34 days, whereas the abstract and conclusion state 98.4%; Figure 2c plots a near-complete extent. The manuscript gives no explicit leaching-percentage calculation or full solid-liquid iron balance. Its plotted extent and solution concentrations are not an isolated jarosite-derived product yield, and neither conflicting sulfite percentage is selected as an accepted recovery measurement.
Supplementary Figure S2 gives day-34 abiotic leaching extents of 1.3%, 6.3% and 8.5% for elemental sulfur, thiosulfate and sulfite, respectively; maxima across sampled times are 1.5%, 6.3% and 8.7%. These source-defined extents are retained to distinguish endpoint from maximum and to show that abiotic release was not zero. Statements in the main text that sulfite alone could not mediate dissolution are stronger than these control observations support. They do not establish a uniquely biological dissolution reaction.
Figures 4-8 compare final residues with controls. After 34 days, the sulfite culture residue lacks the characteristic jarosite Raman peaks seen in its uninoculated control, and its Fe L-edge spectrum resembles the Fe(II) sulfate standard rather than the initial ferric jarosite. SEM shows fine, poorly crystallized residue rather than the original jarosite morphology. These observations support substantial transformation of the sampled solid; non-detection without a quantified phase detection limit does not prove complete disappearance of every jarosite particle or recovery of a pure crystalline ferrous-sulfate product.
Figure 2b shows decreases in dissolved Fe(II) at some later sulfite-arm times; Fe(II)-bearing solids in Figure 7 are compatible with repartitioning. Solution iron alone therefore does not close the iron inventory. Figure 8 assigns sulfur spectra in the sulfite culture residue to sulfate and observes elemental sulfur in both biotic and abiotic thiosulfate residues. These spectra support sulfur transformation but do not resolve a complete electron balance or distinguish direct microbial electron transfer from reactions involving sulfur intermediates.
Figure 3 and Supplementary Figure S4 show donor-dependent pH and redox trajectories, including an early rise toward pH 2.8 in the abiotic thiosulfate control. This qualifies the main text's statement that abiotic pH and redox values showed no significant changes. There is no pH-clamped comparison isolating microbial effects from evolving solution chemistry. S4 also includes a sodium-sulfate control curve not described among the three dissolution donors in Methods 2.3; it is not used here to infer a fourth equivalently specified assay.
Figure 3c reports no significant increase in planktonic cell counts in the sulfite arm despite its largest dissolution response. Counts do not demonstrate viability, biomass yield or energy conservation by iron respiration. The experiment does not measure an enzyme, test respiratory mutants, or eliminate chemical reduction by cell-associated or released sulfur intermediates. Laboratory removal of this prepared jarosite does not establish improved extraction from a mixed ore, industrial jarosite-waste treatment or an industrial recovery process.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. PDF page 104, Jarosite row; page 1 explains status and approval/redefinition fields.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-11)
  2. chen2022: Chen et al. (2022). Reductive dissolution of jarosite by inorganic sulfur compounds catalyzed by Acidithiobacillus thiooxidans. Hydrometallurgy 212, 105908. Complete Coventry accepted manuscript, methods sections 2.1-2.4, Table 1, Figures 1-8, and appended Supplementary Figures S1-S4.
    https://doi.org/10.1016/j.hydromet.2022.105908 (accessed 2026-10-11)
  3. chen2022_postprint: Coventry University author accepted manuscript for Chen et al. (2022), 28-page PDF including repository cover and supplementary material; the repository identifies the version and CC BY-NC-ND 4.0 terms.
    https://pure.coventry.ac.uk/ws/files/65409385/Post_Print.pdf (accessed 2026-10-11)
  4. ncbi_thiooxidans: NCBI Taxonomy 930, Acidithiobacillus thiooxidans, species-level identity; this identifier does not identify the experimental strain.
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=930 (accessed 2026-10-11)
  5. dsm504: DSMZ culture catalogue, Acidithiobacillus thiooxidans DSM 504, including equivalent collection numbers ATCC 8085 and NCIMB 9112. The study names DSM 504 obtained from the Changsha biometallurgy laboratory.
    https://www.dsmz.de/collection/catalogue/details/culture/DSM-504 (accessed 2026-10-11)

Curation History

Timestamp Curator Action Summary
2026-10-11T21:41:36.525409+00:00 codex (GPT-6; codex) CREATE Created the K-jarosite species record with one laboratory culture-associated reductive dissolution comparison, retaining feed composition, conflicting source percentages, nonzero controls and unresolved causal and product claims.

Record source: data/records/jarosite.yaml