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Talc mineral

Talc is the Mg3Si4O10(OH)2 mineral species, grandfathered in the September 2026 IMA list. This species is distinct from elemental magnesium or silicon and from generic magnesium-bearing rocks or commercial mineral mixtures. No constituent criticality is inherited. This record and the companion forsterite record curate different substrates in the same Cai 2013 experiment, not independent studies.

Microbial & Biochemical Mechanisms (1)

Limited magnesium release from talc during fungal culture

bioleaching Microbial

Associated Organisms: Aspergillus niger (NCBITaxon:5061)

Aspergillus niger grew with talc as the supplied magnesium source, but the final dissolved magnesium concentration was much smaller than in the companion forsterite culture. No secondary mineral was recovered from the talc treatment after ten days. This is a substrate-dependent laboratory observation, not evidence that talc is universally resistant to microbial transformation.

Experimental Context & Analytical Limits:
The reported Aspergillus niger strain has no collection accession in the inspected paper; NCBI:5061 resolves only the species. Mineral powders were washed and sonicated, exposed to 0.1 mM HCl for one hour, rinsed and air-dried; feed XRD purity is reported but its patterns are not shown. In the selected Mg-source comparison, minus-200-mesh particles supplied 0.01 mol Mg to 95 mL Czapek-based medium plus 5 mL inoculum at 10^7 spores/mL. Initial pH was adjusted to 8.15; growing cultures were shaken at 150 rpm and 30 degrees C for ten days. The separate particle-size and filtered-MgSO4-supernatant experiments are not pooled with this comparison.
Curated Evidence Points:
Table 1 reports final talc-culture Mg of 3.121 x 10^-4 mol/L by ICP-AES and total oxalate species of 0.039 mol/L by HPLC, compared with forsterite-culture Mg of 1.854 x 10^-2 mol/L. Results pp304-305 report acidification followed by pH increase and no secondary precipitate after ten days in the talc arm.
Table 2 tests abiotic oxalic-acid dissolution of forsterite, not talc. A matched uninoculated talc trajectory is not reported, so the talc observation does not quantify a microbial enhancement over abiotic dissolution. Replicate counts and uncertainties for Table 1 are unspecified. The authors explain the precipitation null by an apparent concentration product, but this is not a measured recovery yield or general thermodynamic validation. The experiment does not establish purified magnesium recovery or industrial deployment.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026; PDF page 211, Talc row, and pages 1-2 definitions and terms.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-11)
  2. cai_2013: Cai, Xiao, Huang, Li and Zhou (2013). Solubilization of Magnesium-Bearing Silicate Minerals and the Subsequent Formation of Glushinskite by Aspergillus niger. Geomicrobiology Journal 30(4):302-312. DOI 10.1080/01490451.2012.688924; methods pp303-304, Tables 1-2, Results pp304-305 and Discussion pp307-308.
    https://doi.org/10.1080/01490451.2012.688924 (accessed 2026-10-11)
  3. ncbi_niger: NCBI Taxonomy 5061 - Aspergillus niger, species rank; taxonomy XML inspected 11 October 2026.
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=5061&mode=Info (accessed 2026-10-11)

Curation History

Timestamp Curator Action Summary
2026-10-11T10:24:47.919181+00:00 codex (GPT-6; codex) CREATE Created talc species record preserving low-release and no-secondary-mineral outcomes.

Record source: data/records/talc.yaml