Böhmite mineral
Böhmite, commonly spelled boehmite in the experimental literature, is the orthorhombic aluminium oxyhydroxide mineral AlO(OH), commonly designated gamma-AlOOH. It is distinct from diaspore, the Al(OH)3 polymorphs, elemental aluminium, heterogeneous bauxite and the broad refined alumina commodity. The September 2026 IMA list gives grandfathered status and original-description year 1927, not a unique approval accession. The curated evidence concerns chemically synthesized nanoscale boehmite; no microbial mechanism, constituent criticality or industrial recovery performance is inferred.
Microbial & Biochemical Mechanisms (1)
Abiotic formation of nanocrystalline boehmite from aluminium sec-butoxide
other
Rapid hydrolysis of aluminium sec-butoxide, with recipe-dependent hydrothermal treatment, yielded solids assigned to boehmite by infrared spectroscopy and powder diffraction. Electron microscopy showed different aggregate morphologies. This laboratory synthesis establishes an abiotic formation route; it is not microbial mineralization, extraction from bauxite or a quantified product-recovery process.
Experimental Context & Analytical Limits:
Štefanić and Musić prepared six differently processed samples B1-B6 from analytical-grade aluminium sec-butoxide and water. Table 1 gives B1/B2 as 20 mL alkoxide vigorously mixed with respectively 179/179.5 mL water initially near 95 degrees C and 1/0.5 mL concentrated acetic acid, followed by autoclaving at 90 degrees C for three days; reported pH values are about 3.7/4.1. B3 used 40 mL alkoxide and 40 mL water, forming an exothermic thixotropic gel near pH 6; aging time and a controlled synthesis temperature are not specified. B4-B6 used 30 mL alkoxide, 210 mL water and 60 mL 25 wt percent aqueous tetramethylammonium hydroxide, near pH 13.5. B4 suspension was autoclaved at 90 degrees C for three days; B5/B6 suspensions were filtered and their clear solutions autoclaved at 120 degrees C for two/four days. These are six recipes, not six replicates. Subsequent room-temperature characterization used KBr-pellet FT-IR, FE-SEM of uncoated specimens, and CuKalpha powder XRD. Washing, drying and final solid-recovery procedures, independent synthesis replication and gravimetric yield are not supplied. No microorganisms, biomass or biogenic reagent production were used.
Štefanić and Musić prepared six differently processed samples B1-B6 from analytical-grade aluminium sec-butoxide and water. Table 1 gives B1/B2 as 20 mL alkoxide vigorously mixed with respectively 179/179.5 mL water initially near 95 degrees C and 1/0.5 mL concentrated acetic acid, followed by autoclaving at 90 degrees C for three days; reported pH values are about 3.7/4.1. B3 used 40 mL alkoxide and 40 mL water, forming an exothermic thixotropic gel near pH 6; aging time and a controlled synthesis temperature are not specified. B4-B6 used 30 mL alkoxide, 210 mL water and 60 mL 25 wt percent aqueous tetramethylammonium hydroxide, near pH 13.5. B4 suspension was autoclaved at 90 degrees C for three days; B5/B6 suspensions were filtered and their clear solutions autoclaved at 120 degrees C for two/four days. These are six recipes, not six replicates. Subsequent room-temperature characterization used KBr-pellet FT-IR, FE-SEM of uncoated specimens, and CuKalpha powder XRD. Washing, drying and final solid-recovery procedures, independent synthesis replication and gravimetric yield are not supplied. No microorganisms, biomass or biogenic reagent production were used.
Curated Evidence Points:
Support
Source:
stefanic2011
Experimental section, Table 1, Figure 1 and Results pp 482-484 support the source assignment of boehmite in all six recipes. Figure 4 displays Le Bail powder-pattern fits for B1, B2, B3, B4 and B6, but not B5. The statement that boehmite was the only crystalline phase detected is retained within the source scope; it does not quantify an amorphous fraction, prove total chemical purity or establish complete precursor conversion.
Partial
Source:
stefanic2011
Figures 2-3 show acidic-recipe conglomerates, a needle-associated star-like B3 morphology, B4 granular aggregates and B5/B6 plate aggregates. Some individual particles cannot be resolved in the acidic samples. These are selected processed-solid micrographs, not a time-resolved nucleation sequence or a particle-population measurement. Acetate bands in B1/B2 and broad water bands in Figure 1 also limit a chemically pure-product interpretation.
Partial
Source:
stefanic2011
Table 2 and Figure 4 report fitted, direction-dependent coherent-domain dimensions for five samples after correcting line broadening with a silicon instrumental standard. The fitted near-zero strain parameters are model results rather than proof of zero physical strain, and coherent-domain dimensions are not aggregate sizes. B5 has no corresponding displayed size fit. Changes in pH, reagent composition, temperature, filtration and duration are partly confounded across recipes, so the overall trend is not an independently isolated pH or temperature effect. No mineral mass balance or recovery yield was measured.
Sources & References
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ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026; definitions pages 1-2 and Böhmite row PDF page 28: AlO(OH), G, 1927. Official URL reopened and previously acquired 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) -
handbook: Handbook of Mineralogy. Böhmite, version 1, 2001-2005; complete one-page identity entry, orthorhombic AlO(OH), dimorphism with diaspore and natural occurrence.
https://www.handbookofmineralogy.org/pdfs/bohmite.pdf (accessed 2026-10-14) -
stefanic2011: Štefanić, Goran and Musić, Svetozar (2011). Microstructural Analysis of Boehmite Nanoparticles Prepared by Rapid Hydrolysis of Aluminum Sec-butoxide. Croatica Chemica Acta 84(4):481-485. DOI 10.5562/cca1884; complete five-page original, Tables 1-2 and Figures 1-4.
https://doi.org/10.5562/cca1884 (accessed 2026-10-14)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-14T11:26:58.745923+00:00 |
codex (GPT-6; codex) | CREATE | Created Böhmite mineral identity and a full-primary abiotic synthesis record, preserving recipe differences, fitted nanocrystal dimensions, incomplete phase-purity evidence and absent microbial or recovery claims. |
Record source: data/records/boehmite.yaml