Kaolinite mineral
Kaolinite is the aluminium phyllosilicate mineral Al2Si2O5(OH)4, distinct from kaolin as a natural clay resource and from halloysite, dickite and nacrite. The September 2026 IMA list records approval by a 1980 special procedure, not a numbered mineral accession. The curated CMS KGa-1b and KGa-2 reference specimens differ in ordering and accessory phases; kaolinite-associated iron is not established as exclusively structural iron. No criticality designation is inferred from aluminium or kaolin.
Microbial & Biochemical Mechanisms (1)
Aerobic acquisition of kaolinite-associated iron with a siderophore response
bioleaching
Microbial
Associated Organisms:
Ectopseudomonas mendocina (NCBITaxon:300)
The source-designated Pseudomonas mendocina isolate grew more in the presence of KGa-1b or KGa-2 than in no-added-iron, mineral-free medium. Under the study's iron-limited design this is indirect evidence of access to specimen-associated iron. A separate KGa-2 experiment detected siderophores and an iron-availability-dependent response. The experiments do not directly quantify iron release from kaolinite, identify the iron-host phase, demonstrate siderophores as the necessary cause, or establish an isolated iron or aluminium recovery product.
Experimental Context & Analytical Limits:
Ams2002 used an aerobic holding-pond isolate from the Nevada Test Site without a reported culture accession. Its source identification is retained without claiming modern strain authentication. CMS KGa-1b from Washington County, Georgia, was well ordered with trace halloysite; KGa-2 from Warren County, Georgia, was poorly ordered with trace anatase. Samples were weakly cleaned with 1 M NaCl adjusted to pH 3 and rinsed; this is not evidence of pure endmember or complete accessory-iron removal. Growth assays used 30 mL succinate-based medium in 150 mL Teflon flasks, 0.0571 g KGa-1b or 0.0324 g KGa-2, normalized to 24 square metres per litre, at 22 degrees C in darkness for four days. Triplicate arms included each kaolinite, 30 micromolar Fe-EDTA, Fe-EDTA plus KGa-1b, and a no-added-iron/no-mineral control. Population was estimated from optical density at 600 nm, not enumerated directly at each time point. The distinct siderophore assay used KGa-2, Fe-EDTA and no-added-iron controls at 28 degrees C and 50 rpm; sacrificial triplicates were sampled on days 2, 4 and 7, and supernatants were pooled by condition/time for extraction and HPLC. These are laboratory physiological assays, not an industrial kaolin beneficiation demonstration.
Ams2002 used an aerobic holding-pond isolate from the Nevada Test Site without a reported culture accession. Its source identification is retained without claiming modern strain authentication. CMS KGa-1b from Washington County, Georgia, was well ordered with trace halloysite; KGa-2 from Warren County, Georgia, was poorly ordered with trace anatase. Samples were weakly cleaned with 1 M NaCl adjusted to pH 3 and rinsed; this is not evidence of pure endmember or complete accessory-iron removal. Growth assays used 30 mL succinate-based medium in 150 mL Teflon flasks, 0.0571 g KGa-1b or 0.0324 g KGa-2, normalized to 24 square metres per litre, at 22 degrees C in darkness for four days. Triplicate arms included each kaolinite, 30 micromolar Fe-EDTA, Fe-EDTA plus KGa-1b, and a no-added-iron/no-mineral control. Population was estimated from optical density at 600 nm, not enumerated directly at each time point. The distinct siderophore assay used KGa-2, Fe-EDTA and no-added-iron controls at 28 degrees C and 50 rpm; sacrificial triplicates were sampled on days 2, 4 and 7, and supernatants were pooled by condition/time for extraction and HPLC. These are laboratory physiological assays, not an industrial kaolin beneficiation demonstration.
Curated Evidence Points:
Support
Source:
ams_2002
Sections 2.1–2.5 and 3.1, Figures 1–2, distinguish specimen preparation and the growth arms. Kaolinite-containing cultures exceeded the no-added-iron control, whereas Fe-EDTA plus KGa-1b supported the largest population. This supports the source's interpretation of access to solid-associated iron under limitation; it does not assign that iron to the kaolinite lattice. The medium retained possible trace iron below the reported analytical detection range, and inoculum carryover was possible, so no-added-iron does not mean iron-free.
Support
Source:
ams_2002
Sections 2.5 and 3.2, Figures 3–5, show different total versus per-cell siderophore patterns: KGa-2 cultures had more siderophore per estimated cell than the Fe-EDTA arm but less than the no-added-iron control. Total production was greatest with Fe-EDTA. Pooled extracts and calibration against the source-designated DFAM standard in the absence of a purified isolate-specific standard make these relative HPLC estimates; the plotted millimolar values are not curated as independently authenticated absolute concentrations. Figure 5's hematite series comes from an earlier experiment and is not a simultaneous kaolinite control.
Partial
Source:
ams_2002
Sections 2.1, 3.1 and 3.3 leave iron distribution among lattice substitution, accessory phases and surface-associated iron unresolved. Cultures with added iron or kaolinite became more alkaline, while the no-added-iron control became more acidic; these are not pH-matched conditions. Aluminium was detected in filtered four-day culture supernatants, but this article's cited earlier abiotic/dissolution comparisons are not an independently inspected matched control series. No quantitative microbial enhancement, stoichiometric kaolinite dissolution, dissimilatory iron reduction, or exclusive siderophore causality is claimed here.
Context_only
Source:
ncbi_mendocina
The current species name grounds the paper's organism label at species rank only. Section 2.2's historical identification wording and lack of a strain accession limit confidence in the experimental isolate; the taxon identifier does not resolve those limitations.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026; definitions pp.1–2 and Kaolinite row PDF p.109, Al2Si2O5(OH)4, A, 1980 s.p. Retained official original re-inspected 14 October 2026.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14) -
kaolinite_handbook: Handbook of Mineralogy: Kaolinite, 2001 version 1.2; complete two-page entry, triclinic mineral identity and composition.
https://www.handbookofmineralogy.org/pdfs/kaolinite.pdf (accessed 2026-10-14) -
ams_2002: Ams, D.A.; Maurice, P.A.; Hersman, L.E.; Forsythe, J.H. (2002). Siderophore production by an aerobic Pseudomonas mendocina bacterium in the presence of kaolinite. Chemical Geology 188:161–170. DOI 10.1016/S0009-2541(02)00077-3. Complete ten-page original and Figures 1–5 inspected.
https://doi.org/10.1016/S0009-2541(02)00077-3 (accessed 2026-10-14) -
ncbi_mendocina: NCBI Taxonomy taxon 300: Ectopseudomonas mendocina, species rank; authoritative XML checked 14 October 2026. Pseudomonas mendocina is the name used by the original study. Species-level naming does not authenticate its unaccessioned experimental isolate.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=300 (accessed 2026-10-14)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-14T14:48:14.855068+00:00 |
codex (GPT-6; codex) | CREATE | Created distinct kaolinite species record from the complete Ams2002 original, preserving indirect iron-access evidence, specimen impurities, pooled relative siderophore assay and unresolved causal/strain limits. |
2026-10-14T14:59:47.558402+00:00 |
codex (GPT-6; codex) | EDIT | Corrected unsupported expansion of the calibration-standard abbreviation to source-designated DFAM, preserving relative HPLC and causal limitations; addressed independent review finding and issue 242. |
Record source: data/records/kaolinite.yaml