Gibbsite mineral
Gibbsite is the monoclinic aluminium hydroxide mineral Al(OH)3, distinct from bayerite and other Al(OH)3 polymorphs, aluminium oxyhydroxides, elemental aluminium, the alumina commodity and heterogeneous bauxite. The September 2026 IMA list reports approved status with the special-procedure entry 1962 s.p.; this is not a unique numbered mineral accession. The curated experiment concerns abiotic dissolution of synthetic gibbsite nanoplates. No mineral-specific criticality designation, microbial mechanism or industrial recovery performance is inferred. The separate Lee and Fein 2000 bacterial-dissolution lead remains uncurated pending inspectable full primary evidence, tracked in CMMMech issue 219.
Microbial & Biochemical Mechanisms (1)
Abiotic alkaline dissolution with an inferred dimer-assisted surface pathway
other
In situ atomic-force microscopy showed orientation-dependent retreat of synthetic gibbsite step edges in sodium hydroxide. Atomic-resolution images, model-assisted surface reconstruction, bulk solution kinetics and molecular simulations support a proposed dimer-mediated pathway at acute armchair edges. Directly observed dissolution is distinguished from the inferred molecular intermediate and modeled event probabilities; the study also predicts monomer detachment at obtuse edges.
Experimental Context & Analytical Limits:
Li and colleagues synthesized nanoplates from 0.25 M aluminium nitrate solution adjusted near pH 5 with NaOH, washed the precipitated gel, heated it at 80 degrees C for five days, and washed and dried the product at 50 degrees C overnight. TEM, selected-area diffraction and XRD characterized the gibbsite product. Washed nanoplates deposited from about 50 microlitres of 20 mg/L suspension on a cleaned TiO2 (001) wafer were imaged in static NaOH at 20 degrees C. Tested concentrations were 0.01-0.4 M; at 0.4 M retreat was too fast to obtain individual edge velocities. Figure 2 and Movies S1-S2 concern 0.05 M, Figure 3 high-resolution edge imaging 0.1 M, and Figure 4 atomic-resolution etch-pit imaging 0.01 M. Separate bulk 27Al NMR experiments used 1 g/L gibbsite in 0.2 M NaOH at 20 degrees C, with ICP-OES-calibrated solution signals; Raman monitored the solid. These are synthetic-mineral laboratory assays without microorganisms, biomass, ore mixtures or a product-recovery step.
Li and colleagues synthesized nanoplates from 0.25 M aluminium nitrate solution adjusted near pH 5 with NaOH, washed the precipitated gel, heated it at 80 degrees C for five days, and washed and dried the product at 50 degrees C overnight. TEM, selected-area diffraction and XRD characterized the gibbsite product. Washed nanoplates deposited from about 50 microlitres of 20 mg/L suspension on a cleaned TiO2 (001) wafer were imaged in static NaOH at 20 degrees C. Tested concentrations were 0.01-0.4 M; at 0.4 M retreat was too fast to obtain individual edge velocities. Figure 2 and Movies S1-S2 concern 0.05 M, Figure 3 high-resolution edge imaging 0.1 M, and Figure 4 atomic-resolution etch-pit imaging 0.01 M. Separate bulk 27Al NMR experiments used 1 g/L gibbsite in 0.2 M NaOH at 20 degrees C, with ICP-OES-calibrated solution signals; Raman monitored the solid. These are synthetic-mineral laboratory assays without microorganisms, biomass, ore mixtures or a product-recovery step.
Curated Evidence Points:
Support
Source:
li2025
Figures 1-3, SI Figures S1-S8 and Movies S1-S2 show gibbsite identity, approximately single-layer retreat and contrasting directional velocities for adjacent spirals. Figure 2 averages more than ten edges per direction; the SI direction plots use more than three edges per direction from two spirals. These edge observations are not independent batch-replicate counts. No complete mineral mass balance or industrial recovery yield is established. SI Figures S4 and S5 both label their conditions 0.01 M; no alternative concentration is assigned to S5 by inference.
Partial
Source:
li2025
Figure 4 shows an etch pit and transient surface features interpreted as clusters, with U-Net-assisted Al-position reconstruction. This atomic-resolution observation has a different spatial scope from the earlier spiral images reporting no opening of etch pits. SI pages 3-4 and Figures S12-S16 describe 500 simulated training/validation image pairs, adjusted adatom heights and synthetic noise. Reported average tracking errors of 0.31 angstrom for surface atoms and 1.17 angstrom for adatoms were evaluated on simulated validation data, not experimentally known atomic positions. Image contrast and the reconstruction support the proposed surface-dimer interpretation but are not direct molecular identification of dimers in bulk solution.
Partial
Source:
li2025
SI page 2 and Figure S9 fit bulk dissolution to a pseudo-second-order model while approximating constant hydroxide and surface area; the source reports less than 2 percent hydroxide consumption and about 18 percent dissolved mass for that argument, not a recovered-product yield. NMR detects dissolved Al(OH)4- and does not show the additional resonances considered in S9B. Raman Figures S10-S11 support persistence of gibbsite within detection limits but do not detect the low-concentration dissolved aluminate signal. These observations support the proposed kinetics without directly resolving the dimer intermediate or establishing that no trace secondary phase exists.
Partial
Source:
li2025
Figure 5 and SI Figures S17-S21 use DFTB molecular dynamics and umbrella sampling to compare acute/obtuse armchair pathways. Dimer Al-Al separation is constrained, hydroxide attachment to newly undercoordinated sites is partly manual, and error bars derive from trajectory blocks. The predicted acute-edge dimer preference and obtuse-edge monomer preference are model results; the predicted two-order rate contrast is not identical to the approximately one-order contrast observed by AFM. The simulated greater-than-95-percent initial acute-edge dimer-event estimate is neither a measured dissolution fraction nor extraction efficiency. The study discusses sequential paired-monomer removal as an alternative kinetic explanation and does not establish one universal pathway for all surfaces or conditions.
Sources & References
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ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026; definitions pages 1-2 and Gibbsite row PDF page 82: Al(OH)3, A, 1962 s.p. Official URL reopened and previously acquired original visually re-inspected on 14 October 2026.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14) -
handbook: Handbook of Mineralogy. Gibbsite, version 1, 2001-2005; complete one-page identity entry, monoclinic Al(OH)3 and polymorphism with bayerite, doyleite and nordstrandite.
https://www.handbookofmineralogy.org/pdfs/gibbsite.pdf (accessed 2026-10-14) -
li2025: Li, Xiaoxu and colleagues (2025). Mineral dissolution by dimeric complexes. Proceedings of the National Academy of Sciences 122(41):e2504109122. DOI 10.1073/pnas.2504109122; complete primary text, Figures 1-5, 26-page Supporting Information including Figures S1-S21 and sampled Movies S1-S2. PMID 41052339; PMCID PMC12541406.
https://doi.org/10.1073/pnas.2504109122 (accessed 2026-10-14)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-14T11:32:40.975121+00:00 |
codex (GPT-6; codex) | CREATE | Created gibbsite identity and full-primary abiotic alkaline-dissolution evidence; separated observed retreat, bulk spectroscopy and model-dependent dimer interpretation, and retained the unresolved bacterial-source gap in issue 219. |
Record source: data/records/gibbsite.yaml