Becquerelite mineral
Becquerelite is a calcium uranyl oxide hydroxide hydrate mineral, Ca(UO2)6O4(OH)6·8H2O in the September 2026 IMA list. Its status is grandfathered G; 1922 is the original-description year, not an IMA approval accession. The mineral is distinct from elemental uranium, schoepite, other uranyl oxide hydrates and Sr-exchanged synthetic derivatives. The accepted dissolution experiment used synthesized becquerelite crystals, not an ore or a natural field population. Surface morphology and later spectroscopy support a restricted laboratory dissolution and secondary-precipitation account; they do not establish microbial activity, criticality, bulk uranium recovery efficiency or industrial deployment.
Microbial & Biochemical Mechanisms (1)
Abiotic acidic dissolution of synthesized becquerelite surfaces
other
Acidic solutions produced etch pits and other dissolution features on the basal surfaces and edges of synthesized becquerelite. Pit orientation differed with the dissolved cation under the tested conditions. Protonation and cation adsorption were proposed to explain these patterns; adsorbed cation rows were not directly mapped. Surface coatings formed under other conditions must be distinguished from removal of the underlying solid.
Experimental Context & Analytical Limits:
The 2006 crystals were prepared from 0.31 g uranyl acetate, 0.05 g calcium carbonate and 4 mL ultrapure water in a 23 mL Teflon-lined vessel at 160 degrees C for 50 hours, then washed rapidly and air-dried. Four or five crystals per experiment were placed in 1 mL solution at room temperature, whose numerical value was not specified. The pH 2 arms lasted 30 minutes: HCl alone, 1.0 mol/L NaCl or KCl, or 0.5 mol/L BaCl2, SrCl2, MgCl2 or Pb(NO3)2 in acidic solution. These electrolyte arms had equal cation normality, not equal ionic strength; measured high-ionic-strength pH uncertainty was approximately 0.2. Samples were washed in pure water and dried before ex-situ AFM, SEM and optical examination.
The 2006 crystals were prepared from 0.31 g uranyl acetate, 0.05 g calcium carbonate and 4 mL ultrapure water in a 23 mL Teflon-lined vessel at 160 degrees C for 50 hours, then washed rapidly and air-dried. Four or five crystals per experiment were placed in 1 mL solution at room temperature, whose numerical value was not specified. The pH 2 arms lasted 30 minutes: HCl alone, 1.0 mol/L NaCl or KCl, or 0.5 mol/L BaCl2, SrCl2, MgCl2 or Pb(NO3)2 in acidic solution. These electrolyte arms had equal cation normality, not equal ionic strength; measured high-ionic-strength pH uncertainty was approximately 0.2. Samples were washed in pure water and dried before ex-situ AFM, SEM and optical examination.
Curated Evidence Points:
Support
Source:
schindler2006
Figures 4 and 6-9 show dissolution features after the pH 2 exposures. Etch pits in HCl alone had irregular or rounded boundaries. Pits in Ba-, K-, Mg- and Na-bearing solutions elongated parallel to [100], whereas Sr- and Pb-bearing solutions produced pits elongated parallel to [010], using the paper's morphology axis convention. Figure 7 compares edge and basal-face appearance. These images support condition-dependent surface alteration, not measured solution uranium release or an intrinsic ranking of bulk dissolution rates.
Partial
Source:
schindler2006
Figure 5 shows hillocks after separate exposures to HCl at pH 3.5 for one hour, ultrapure water for 24 hours, or Na2CO3 at pH 10.5 for one hour. The carbonate arms used 0.1 and 0.5 mol/L, with Figure 5c specifically showing 0.1 mol/L. The page 1219 proof-stage note identifies hillocks as products of precipitation of a uranium-enriched phase on the basis of later XPS and in-situ AFM, limiting the earlier dissolution-only interpretation. Unequal durations, solution composition and post-exposure washing/drying prevent a clean pH-only comparison. The paper did not perform in-situ kinetics or report a bulk extraction percentage; its saturation indices are calculated.
Partial
Source:
schindler2011
Table 1 explicitly reuses the 2006 AFM/SEM results and adds in-situ AFM and XPS; it is not independent replication of all earlier arms. Figure 2 shows a becquerelite pit evolving at 0, 4, 8 and 11 minutes relative to the first image shortly after HCl pH 2 injection. Methods give room temperature near 22 degrees C and fresh fluid replacement every 20 minutes. Solution composition was not monitored, so changing saturation is interpreted rather than directly measured. The general methods include natural and synthetic specimens without an unambiguous specimen identifier for every displayed arm. These limits prevent assigning that sequence to the exact 2006 synthesis batch or deriving a mass-normalized release rate.
Context_only
Source:
schindler2011
Pages 88-92, Table 3 and Figures 8-11 add surface-composition evidence for uranium-rich coatings after water or weak-acid treatment, and sodium-bearing uranyl hydroxide hydrate coatings after alkaline carbonate treatment. The 2011 methods use 24 hours for water and carbonate and three hours for HCl pH 3.5, distinct from the 2006 durations. Schoepite-type and clarkeite-type interpretations do not prove pure identified mineral products; surface XPS ratios are not bulk composition or isolated-product yields. Proposed passivation remains unquantified for this record.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Becquerelite row, PDF page 22; status and year definitions page 1. Fresh official PDF and row inspected. The row cites Comptes Rendus de l'Académie des Sciences de Paris 174 (1922), 1240 and American Mineralogist 87 (2002), 550. The latter's downloaded full-text file was malformed and is not accepted as inspected experimental evidence here.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-16) -
schindler2006: Schindler M, Hawthorne FC, Burns PC, Maurice PA (2006). Dissolution of uranyl-oxide-hydroxy-hydrate minerals. II. Becquerelite. Canadian Mineralogist 44:1207-1225. DOI 10.2113/gscanmin.44.5.1207. Author-hosted complete published original inspected: 19 article pages plus a blank final PDF page. Synthesis, exposure conditions and Table 1 page 1212; Figures 4-9 pages 1213-1218; proof-stage correction to hillock interpretation page 1219; models and limits pages 1219-1223.
https://doi.org/10.2113/gscanmin.44.5.1207 (accessed 2026-10-16) -
schindler2011: Schindler M, Hawthorne FC, Mandaliev P, Burns PC, Maurice PA (2011). An integrated study of uranyl mineral dissolution processes: etch pit formation, effects of cations in solution, and secondary precipitation. Radiochimica Acta 99:79-94. DOI 10.1524/ract.2011.1802. Complete 16-page author-hosted published original inspected, including Tables 1-4 and Figures 1-11. Table 1 separates reused AFM/SEM evidence from new in-situ AFM and XPS work; methods pages 80-82; Figure 2 page 84; secondary coatings pages 88-92, Table 3 and Figures 8-11.
https://doi.org/10.1524/ract.2011.1802 (accessed 2026-10-16)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-16T04:28:04.167810Z |
codex (GPT-6; codex) | CREATE | Added becquerelite identity and acidic surface dissolution evidence with distinct later spectroscopy, secondary coatings and experimental limits. |
Record source: data/records/becquerelite.yaml