Pyrolusite mineral
Pyrolusite is the MnO2 mineral species in the September 2026 IMA list (status A, 1982 s.p.). The special-procedure entry is not a sequential approval accession. The species is distinct from elemental manganese, unspecified MnO2 polymorphs and source-labelled pyrolusite ores. The accepted experiment below is an explicitly abiotic reaction of characterized commercial beta-MnO2. A microbial ore study was inspected but cannot establish phase-specific microbial causality. No manganese-commodity criticality is inherited.
Microbial & Biochemical Mechanisms (1)
Abiotic Fe(II)-driven pyrolusite reduction and manganese mobilization
redox transformation
Aqueous Fe(II) reacted with characterized beta-MnO2 in an anoxic buffered laboratory system, releasing filter-passing manganese and depositing Fe-bearing secondary phases. Fe-free comparisons did not show measurable Mn release. The experiment contains no microbial culture and therefore supports a chemical alternative pathway, not microbial catalysis, organism activity or industrial metal recovery.
Experimental Context & Analytical Limits:
Schaefer et al. used commercial Sigma-Aldrich MnO2, ground and sieved at 150 micrometres; XRD identified pyrolusite as the sole detected Mn oxide phase, with no detected impurity peaks. BET surface area was 1-2 m2/g. Assays used 18 mg solid in 18 mL deoxygenated 25 mM HEPES plus 25 mM KBr at initial pH 7.5, in a 95% N2/5% H2 chamber below 1 ppmv O2. Approximately 3 mM enriched Fe(II) was added, with an equal-volume NaOH counter-spike; Figure 2 kinetic runs started at 2.4 mM measured Fe(II). Reactors rotated in darkness. Methods describe typical runs of about 90 minutes, while the Figure 2 kinetic series follows 75-minute exposures. The reaction temperature and replicate count are not specified in the inspected methods; no temperature or replicate count is inferred. Samples were filtered through 0.2-micrometre nylon before photometric Fe and formaldoxime Mn analysis. Washed solids could receive additional Fe(II) or Fe-free buffer. This is laboratory chemical mobilization from reagent material, not an organism experiment, natural-ore recovery or an isolated manganese product.
Schaefer et al. used commercial Sigma-Aldrich MnO2, ground and sieved at 150 micrometres; XRD identified pyrolusite as the sole detected Mn oxide phase, with no detected impurity peaks. BET surface area was 1-2 m2/g. Assays used 18 mg solid in 18 mL deoxygenated 25 mM HEPES plus 25 mM KBr at initial pH 7.5, in a 95% N2/5% H2 chamber below 1 ppmv O2. Approximately 3 mM enriched Fe(II) was added, with an equal-volume NaOH counter-spike; Figure 2 kinetic runs started at 2.4 mM measured Fe(II). Reactors rotated in darkness. Methods describe typical runs of about 90 minutes, while the Figure 2 kinetic series follows 75-minute exposures. The reaction temperature and replicate count are not specified in the inspected methods; no temperature or replicate count is inferred. Samples were filtered through 0.2-micrometre nylon before photometric Fe and formaldoxime Mn analysis. Washed solids could receive additional Fe(II) or Fe-free buffer. This is laboratory chemical mobilization from reagent material, not an organism experiment, natural-ore recovery or an isolated manganese product.
Curated Evidence Points:
Support
Source:
schaefer2017
Experimental and Figure 1 establish the starting phase. Figure 2 and the first Results subsection show near-complete solution Fe(II) loss by 75 minutes from the 2.4 mM arm, with approximately 0.6 mM solution Mn and no measured Mn in Fe-free controls. These source-reported values describe filter-passing solution concentrations, not a recovered-product yield. Figure 3 and diffraction/Mossbauer analyses identify an Fe-rich surface coating initially interpreted as lepidocrocite.
Partial
Source:
schaefer2017
The Mn colorimetric assay does not speciate aqueous manganese: Mn(II) is inferred from chemical constraints. Solution Mn was lower than the simple two-Fe-per-Mn stoichiometric prediction; sorption, incorporation, reoxidation and later phase transformation remain possible explanations. Subsequent solids contain a magnetite/maghemite contribution; the paper explicitly groups these as magnetite, so pure magnetite is not established. Co versus Cu radiation labels conflict between Experimental and Figure 1, and no exact XRD angles are transcribed here. This chemical result neither demonstrates nor rules out microbial reduction under other conditions.
Context_only
Source:
retnaningrum2019
The distinct 16-day KL3 study reported Mn mobilization from Kliripan ore labelled pyrolusite, but no diffraction phase confirmation was provided, and feed contained reported 25% Mn, 30.4% Fe and 34% S. Its C arm is no added mineral, not an uninoculated mineral control. Methods specify pH 6.0 whereas Figure 2 caption says 2.0; a pulp-density list repeats 0.03, and Table 1 mixes atomic/mass labels with a nonclosing day-16 composition. Surface cells/EPS, acidification and Mn release therefore do not prove a mineral-specific microbial pathway or isolate sulfur causality. No KL3 taxon identifier, bioleaching yield or direct-versus-indirect mechanism is accepted. This contextual study is not the abiotic control for Schaefer and is not transferred into microbial evidence for the species.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. PDF page 179, Pyrolusite row; page 1 column definitions and page 2 distribution terms.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-11) -
schaefer2017: Schaefer, Handler and Scherer (2017). Fe(II) reduction of pyrolusite (beta-MnO2) and secondary mineral evolution. Geochemical Transactions 18:7. DOI 10.1186/s12932-017-0045-0; PMC5716966; Experimental, Figures 1-3, Results and discussion.
https://doi.org/10.1186/s12932-017-0045-0 (accessed 2026-10-11) -
retnaningrum2019: Retnaningrum and Wilopo (2019). Pyrolusite Bioleaching by an Indigenous Acidithiobacillus sp KL3 Isolated from an Indonesian Sulfurous River Sediment. Indonesian Journal of Chemistry 19(3):712-719. DOI 10.22146/ijc.38898; contextual mixed-ore study with unresolved phase and reporting limitations.
https://doi.org/10.22146/ijc.38898 (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T09:27:06.884364+00:00 |
codex (GPT-6; codex) | CREATE | Created pyrolusite species identity and controlled abiotic reduction; deferred unproven microbial phase-specific causality. |
Record source: data/records/pyrolusite.yaml