Nepheline mineral
Nepheline is a feldspathoid mineral species, listed with formula Na3K(Al4Si4O16) and redefined status in the September 2026 IMA list. It is distinct from feldspar minerals, nepheline syenite and phonolite rocks, traded feldspar commodity, and its constituent elements. The curated fungal experiment used a characterized nepheline-rich Bancroft specimen containing other minerals, not a pure endmember. No constituent or commodity criticality designation is inherited.
Microbial & Biochemical Mechanisms (1)
Fungal pitting and aluminium mobilization from nepheline-rich Bancroft discs
bioleaching
Microbial
Associated Organisms:
Aspergillus niger (NCBITaxon:5061)
Historical Aspergillus niger CMI 31821 cultures produced greater pitting of Bancroft nepheline-rich discs than the plotted uninoculated blank. Pitting depth covaried with aluminium in filtered culture liquid. These observations support fungal weathering of the characterized specimen, with nepheline identified as its principal reactive mineral; they do not partition aluminium release among every constituent phase or demonstrate a purified recovery product.
Experimental Context & Analytical Limits:
King used Bancroft material characterized by optical microscopy, electron microprobe and physical/chemical separation. Table 2.7 gives nepheline estimates of 78.81 plus/minus 0.6 wt% by chemical allocation and 84.0 plus/minus 8.5 wt% by microprobe, with albite, sodalite, biotite and magnetite also present. These method-specific estimates are not pure-phase certification. Discs were 1.0 cm in diameter and 4 mm thick, polished on one face with 600-mesh carborundum; remaining surfaces were silicone-sealed and briefly flame-sterilized in burning methanol. Petri dishes held sucrose medium LM1 just wetting the exposed face, replenished with fresh medium for evaporation. Tables 2.10-2.11 specify sucrose 10 g/L, ammonium carbonate 1.5 g/L, KH2PO4 0.1 g/L, MgSO4·7H2O 0.8 g/L, initial pH 6.5 and Cu, Zn and Fe ions each 0.01 mg/L. Each inoculated disc received one pregrown 3-4 mm fungal pellet. Five discs per material per strain supplied one destructive sample at each of 1, 2, 4, 6 and 8 weeks; one additional disc per material was an uninoculated blank. The disc subsection does not restate a specific incubation temperature, agitation rate or liquid volume, so conditions from separate flask screening and optimized fermentations are not transferred. Pitting was measured through the reported silica-gel layer to unreacted material with a micrometer divider; residual liquid was filtered before aluminium analysis. Norwegian syenite and Czech phonolite were separate comparison feeds and are not treated as equivalent nepheline specimens.
King used Bancroft material characterized by optical microscopy, electron microprobe and physical/chemical separation. Table 2.7 gives nepheline estimates of 78.81 plus/minus 0.6 wt% by chemical allocation and 84.0 plus/minus 8.5 wt% by microprobe, with albite, sodalite, biotite and magnetite also present. These method-specific estimates are not pure-phase certification. Discs were 1.0 cm in diameter and 4 mm thick, polished on one face with 600-mesh carborundum; remaining surfaces were silicone-sealed and briefly flame-sterilized in burning methanol. Petri dishes held sucrose medium LM1 just wetting the exposed face, replenished with fresh medium for evaporation. Tables 2.10-2.11 specify sucrose 10 g/L, ammonium carbonate 1.5 g/L, KH2PO4 0.1 g/L, MgSO4·7H2O 0.8 g/L, initial pH 6.5 and Cu, Zn and Fe ions each 0.01 mg/L. Each inoculated disc received one pregrown 3-4 mm fungal pellet. Five discs per material per strain supplied one destructive sample at each of 1, 2, 4, 6 and 8 weeks; one additional disc per material was an uninoculated blank. The disc subsection does not restate a specific incubation temperature, agitation rate or liquid volume, so conditions from separate flask screening and optimized fermentations are not transferred. Pitting was measured through the reported silica-gel layer to unreacted material with a micrometer divider; residual liquid was filtered before aluminium analysis. Norwegian syenite and Czech phonolite were separate comparison feeds and are not treated as equivalent nepheline specimens.
Curated Evidence Points:
Support
Source:
king_1985
Section 2.3.4, printed pages 125-133 (PDF pages 133-141), and Figures 2.21-2.25 show fungal mats, hyphae associated with the altered surface, greater pitting for the CMI 31821 Bancroft treatment than the near-zero blank trace, and a positive relationship between pitting and aluminium release. Section 2.2 and Tables 2.4/2.7 establish the specimen's nepheline-rich but mixed mineralogy. No plotted values are digitized or asserted as exact yields.
Partial
Source:
king_1985
One destructively sampled disc per time point and a single stated blank per material do not establish replicated effect sizes or uncertainty intervals. Figure 2.25 presents one generic blank trace without separately resolving the materials' blanks. The second strain is CMI 243400 in Table 2.8 and section 2.3.4, but the Figure 2.25 legend prints CMI 234300. Its identity is unresolved; no exact second-strain performance claim is adopted. Nepheline fraction estimates differ between analytical methods, and other Al-bearing phases occur, so whole-disc aluminium release is not a nepheline-specific mass balance.
Partial
Source:
king_1985
Organic-acid production and mineral-contact observations motivate an acid-mediated weathering interpretation, but this disc experiment does not isolate proton attack, ligand effects and physical interaction using matched acid, pH or killed-biomass controls. The reported gel coating and attached hyphae are not independent proof of a particular molecular pathway. Other thesis chapters' kinetic models, semi-continuous equipment and economic projections are outside this curated assay and do not establish industrial deployment.
Context_only
Source:
ncbi_niger
Taxon 5061 resolves the source's species name, not the historical strain stocks. CMI 31821 is retained as reported; no genome, strain-specific taxonomy identifier or modern sequence authentication is inferred.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Definitions pages 1-2 and nepheline row page 154, formula Na3K(Al4Si4O16), Rd, 2018 s.p.; original description cited to 1801. Retained original row visually re-inspected on 14 October 2026.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14) -
king_1985: King, Andrew (1985). The biodegradation of nepheline by Aspergillus niger. PhD thesis, University of London, Imperial College, February 1985. Complete 340-page original acquired from Imperial Spiral; curated scope is Chapter 2 specimen characterization and disc assay, sections 2.2-2.3.4, especially printed pages 89-133, Tables 2.4, 2.7, 2.8, 2.10-2.11 and Figures 2.21-2.26. This is original doctoral research, not a journal replication.
https://hdl.handle.net/10044/1/37745 (accessed 2026-10-14) -
ncbi_niger: NCBI Taxonomy, Aspergillus niger, taxon 5061, species rank. Taxonomy XML inspected; this species-level mapping does not authenticate historical CMI cultures or their modern classification.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=5061 (accessed 2026-10-14)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-14T12:20:57Z |
codex | create | Added nepheline identity and a bounded original fungal disc-weathering assay, retaining mixed specimen, limited replication, source strain-label conflict and unresolved causal partitioning. |
2026-10-14T12:29:18Z |
codex | edit | Corrected Figure 2.25 legend transcription to CMI 234300 after independent finding F1 and issue 227; preserved its conflict with text CMI 243400 and unchanged CMI 31821 evidence. |
Record source: data/records/nepheline.yaml