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Marcasite mineral

Marcasite is the orthorhombic FeS2 mineral species, distinct from cubic pyrite, other iron sulfides, elemental iron and mixed sulfide ores. The September 2026 IMA list records grandfathered status and original-description year 1845; the year is not an approval accession. The accepted experiment used powder characterized as marcasite by composition and diffraction, without a reported refined phase fraction or specific surface area. No constituent criticality is inherited.

Microbial & Biochemical Mechanisms (1)

Culture-associated ferric-iron accumulation during marcasite oxidation

bioleaching Microbial

Associated Organisms: Acidithiobacillus ferrooxidans (NCBITaxon:920)

Live cultures reported as Thiobacillus ferrooxidans produced greater measured ferric-iron accumulation from marcasite powder than the study's chemically altered inactive-inoculum references. The observation supports conditional culture-associated oxidation and iron mobilization. It does not isolate direct cell attack, quantify total dissolved iron or establish isolated iron-product recovery.

Experimental Context & Analytical Limits:
Nowaczyk and Domka (2000), Methods pp.88–89 and figure/table captions: bacteria were isolated from Siersza colliery mine water, with no strain accession, sequence or independent purity test supplied. Precultures used Silverman 9K medium in 50 mL Erlenmeyer flasks in thermostated shakers. Leaching used 350 mL Erlenmeyer flasks with iron-free Silverman medium, 1%, 2% or 3% (wt/vol) mineral and 10% inoculum; the inoculum basis is printed as wt/vol and is not silently converted to a cell density. Conditions were 37 degrees C and initial pH 2.2, with grain size below 0.125 mm. Figure 4 extends to 40 days. The actual liquid volume, shaker speed, inoculum washing and cell concentration are unreported. Quantitative composition was 45.9% Fe and 53.5% S for marcasite; powder XRD was compared with a standard. Fe(III) was measured colorimetrically by the rhodanate method. Reference samples used boiled inoculum and reported 1500 ppm HgI2 as bacteriostat. No time-resolved pH or redox matching is established.
Curated Evidence Points:
Figure 2 compares the examined marcasite powder with a standard diffraction pattern. Figure 4 shows increasing Fe(III)-based leaching response in inoculated arms, with much smaller responses in the corresponding ch reference series. The response decreases as mineral loading increases from 1% to 3% within this design. Table 1 labels marcasite values 28.1%, 18.5% and 10.4% as yield of iron leaching; these are source-reported assay-based percentages, not independently verified total-iron extraction or recovered-product yields.
Only Fe(III), rather than total dissolved Fe, was monitored. Oxidation-state partitioning, inoculum iron carryover, precipitation and a closed solid/solution iron balance were not independently resolved. Boiling and HgI2 distinguish the reference chemistry from the live cultures, so this is not a matched redox-controlled comparison of biological and abiotic dissolution. Replicate counts, biological variability and the meaning of fitted-parameter uncertainties are not given; model fits do not demonstrate a unique inhibitory mechanism.
The introduction calls marcasite rhombohedral, contrary to the orthorhombic species identity established by the mineral authority. Page 89 says the marcasite rate increased threefold with loading, while Table 1 decreases its fitted k1 from 14.5 to 5.0 in the printed 10^-3 per day scaling. The table/curve direction is retained without repairing the source. The abstract asserts no structure effect, whereas the conclusion says the results cannot unambiguously verify that relationship. Different surfaces, incomplete sample characterization and absent replication prevent a universal pyrite-versus-marcasite reactivity ranking.
Context_only Source: ncbi920
Taxon 920 maps the historical species name to Acidithiobacillus ferrooxidans. It does not authenticate the Siersza isolate or establish a strain-specific molecular mechanism. Neither the paper's introductory reaction schemes nor the kinetic fit is direct enzyme evidence, and no industrial application or purified product was demonstrated.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026; PDF page 136 Marcasite row, pages 1–2 definitions and terms.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14)
  2. handbook: Handbook of Mineralogy. Marcasite; one-page mineral description, crystal data and pyrite dimorphism.
    https://handbookofmineralogy.org/pdfs/marcasite.pdf (accessed 2026-10-14)
  3. nowaczyk2000: Nowaczyk, K. and Domka, F. (2000). Oxidation of Pyrite and Marcasite by Thiobacillus ferrooxidans Bacteria. Polish Journal of Environmental Studies 9(2):87–90. Complete four-page original; Methods pp.88–89, Figures 2–4 and Table 1.
    https://www.pjoes.com/pdf-87281-21140?filename=21140.pdf (accessed 2026-10-14)
  4. ncbi920: NCBI Taxonomy 920, Acidithiobacillus ferrooxidans; Thiobacillus ferrooxidans is a listed synonym. Current authority resolves species nomenclature, not the experimental isolate.
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=920 (accessed 2026-10-14)

Curation History

Timestamp Curator Action Summary
2026-10-14T14:44:37.481657+00:00 codex (GPT-6; codex) CREATE Created distinct marcasite identity and qualified culture-associated Fe(III) evidence, retaining altered controls, assay limitations and internal source conflicts.

Record source: data/records/marcasite.yaml