Hausmannite mineral
Hausmannite is the grandfathered tetragonal manganese oxide mineral Mn2+Mn3+2O4, commonly written Mn3O4; the IMA September 2026 list gives 1828 as its historical entry. It is distinct from elemental manganese, other manganese oxides, manganese oxalate products and mixed natural manganese ores. The curated laboratory experiment used a synthesized oxide preparation identified by the authors as hausmannite, not a natural mineral specimen. No criticality designation is inherited from manganese.
Microbial & Biochemical Mechanisms (1)
Selenium-conditioned manganese mobilization during fungal culture with synthetic hausmannite
bioleaching
Microbial
Associated Organisms:
Aspergillus niger (NCBITaxon:5061)
In laboratory cultures of Aspergillus niger with a synthesized oxide assigned to hausmannite, selenate addition was associated with a lower final culture pH and a higher manganese concentration in the filtered spent medium than in selenium-free fungal cultures. This supports a condition-dependent culture-associated mobilization observation. It does not isolate a fungal contribution relative to a time-matched sterile system, identify a particular acid or enzyme, demonstrate manganese redox speciation, or establish an isolated product yield or industrial deployment.
Experimental Context & Analytical Limits:
Section 2 identifies the inoculum as spores from a seven-day colony of A. niger CBS 140837, originally isolated from mercury-contaminated soil. The species TaxID does not resolve that strain; inoculum concentration and volume are not reported. The manganese oxide was prepared by alkaline precipitation of manganese sulfate, heated under reflux for five hours, filtered, washed, dried at 80 degrees C and oven-heated at 95 degrees C for one hour before use. The paper cites earlier X-ray diffraction characterization for its hausmannite assignment; it does not show a fresh diffraction pattern or quantified phase purity for the tested batch. Flasks contained 45 mL of autoclaved Sabouraud Dextrose Broth and 0.11 g of oxide; selenate treatments received 5 mL of solution providing a final total selenium concentration of 50 mg/L. The stated final oxide loading was 2.2 g/L. Suspensions were stirred at 130 rpm for 24 hours before sampling and inoculation, then incubated statically for three weeks at 25 degrees C in the dark. Treatments were in triplicate. Initial medium pH is not reported. Fungal biomass was separated, washed and dried; spent medium was filtered at 0.45 micrometres, and residual solids were collected separately. The ferric oxyhydroxide arm was a different feed.
Section 2 identifies the inoculum as spores from a seven-day colony of A. niger CBS 140837, originally isolated from mercury-contaminated soil. The species TaxID does not resolve that strain; inoculum concentration and volume are not reported. The manganese oxide was prepared by alkaline precipitation of manganese sulfate, heated under reflux for five hours, filtered, washed, dried at 80 degrees C and oven-heated at 95 degrees C for one hour before use. The paper cites earlier X-ray diffraction characterization for its hausmannite assignment; it does not show a fresh diffraction pattern or quantified phase purity for the tested batch. Flasks contained 45 mL of autoclaved Sabouraud Dextrose Broth and 0.11 g of oxide; selenate treatments received 5 mL of solution providing a final total selenium concentration of 50 mg/L. The stated final oxide loading was 2.2 g/L. Suspensions were stirred at 130 rpm for 24 hours before sampling and inoculation, then incubated statically for three weeks at 25 degrees C in the dark. Treatments were in triplicate. Initial medium pH is not reported. Fungal biomass was separated, washed and dried; spent medium was filtered at 0.45 micrometres, and residual solids were collected separately. The ferric oxyhydroxide arm was a different feed.
Curated Evidence Points:
Support
Source:
farkas2021
Sections 3.1 and 3.3 and original Figures 1a and 2a show lower final pH and greater filtrate manganese in selenate-containing fungal cultures with the hausmannite preparation than in selenium-free fungal cultures with that preparation. The authors report final average pH values of 3.2 and 4.4, respectively. Figure 2a presents a three-week endpoint, not a time-resolved dissolution rate. Section 2.4 measures total manganese by flame atomic absorption spectrometry; the operationally filtered fraction is not a measurement of free manganese ions or their oxidation state.
Partial
Source:
farkas2021
Section 2.3 and figure captions define the plotted control as fungal culture without the added inorganic solid. Selenium-free cultures are additional comparisons. The 24-hour pre-inoculation measurements in Figure 3 precede the three-week inoculated endpoint; they are not a time-matched sterile control. No three-week uninoculated manganese-release series, matched-pH chemical control or killed-biomass comparator is reported. Consequently these data do not quantify the fungal enhancement over abiotic dissolution, nor isolate selenate's direct chemical contribution.
Partial
Source:
farkas2021
Section 3.3 and Figure 2a use g/L for manganese in the medium, whereas Section 4 proposes a protective-cell threshold of 0.25-1.4 mg/L while citing that figure. This three-order unit discrepancy is unresolved; the proposed numerical threshold is not adopted. Section 4's acid, redox-active metabolite, enzyme and manganese-transport explanations are hypotheses supported by literature comparisons, not direct measurements of those causal steps in this experiment. No post-culture manganese mineral identification or manganese recovery percentage is provided.
Partial
Source:
farkas2021
Original Figure 1b supports reduced biomass in the selenate-treated oxide cultures, but Section 3.2 assigns the 86% and 65% inhibition figures to ferric and manganese matrices, respectively, whereas the last paragraph of Section 4 assigns an 86% decrease to the manganese treatment. The graph's selenium-free manganese bar is above 100% despite its label referring to selenium-free treatment, leaving the normalization basis insufficiently clear for resolving the prose by recalculation. No precise inhibition percentage is adopted. The article does not specify the statistical test or define the error bars for its significance claims.
Context_only
Source:
farkas2021
Sections 3.3-3.4 and Figures 3-5 describe selenium redistribution and concentrations in washed biomass alongside the manganese observation. The initial selenium sorption to the hausmannite preparation was small; selenium remained distributed among medium, residual solid and biomass after cultivation. Biomass selenium concentration was higher with hausmannite than in the no-solid culture, while biomass manganese concentration was lower in the selenate-containing than selenium-free hausmannite culture. These are compartment and dry-biomass concentration comparisons, not proof of intracellular localization, measured selenium reduction, total uptake mass or purified selenium recovery. Ferric-oxyhydroxide desorption results cannot be transferred to hausmannite, and no oxalate-product assignment is imported from the separate 2020 arsenic experiment cited in this paper.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Hausmannite row, PDF page 90; formula, grandfathered status and historical year.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-11) -
hausmannite_handbook: Mineralogical Society of America, Handbook of Mineralogy. Hausmannite, one-page entry, Mineral Data Publishing version 1 (2001-2005). Formula and tetragonal crystal data.
https://handbookofmineralogy.org/pdfs/hausmannite.pdf (accessed 2026-10-11) -
farkas2021: Farkas et al. (2021). Fungal Mobilization of Selenium in the Presence of Hausmannite and Ferric Oxyhydroxides. Journal of Fungi 7(10):810. Complete ten-page article, Sections 2-4 and Figures 1-5; publisher PDF/XML and PMC8539610 full text.
https://doi.org/10.3390/jof7100810 (accessed 2026-10-11) -
ncbi_niger: NCBI Taxonomy 5061. Aspergillus niger, current species node.
https://api.ncbi.nlm.nih.gov/datasets/v2/taxonomy/taxon/5061/dataset_report (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T23:42:16.318801Z |
codex | CREATE | Added hausmannite identity and a qualified 2021 selenium-conditioned fungal mobilization observation, preserving controls, phase, unit and biomass-normalization limits without a recovery or industrial claim. |
Record source: data/records/hausmannite.yaml