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Curite mineral

Curite is the lead uranyl oxide hydroxide hydrate mineral with the IMA formula Pb3+x[(UO2)4O4+x(OH)3-x]2(H2O)2, distinct from elemental uranium, lead commodities and synthetic strontium analogues. The September 2026 IMA list gives grandfathered status G; 1921 is its original-description year, not an approval accession. A natural Shinkolobwe crystal was refined in orthorhombic Pnma in 2019. Hydroxyl hydrogen positions were refined from X-ray data, whereas water orientations required Torque calculations; these are not wholly independent experimental determinations of all hydrogen positions. Slight lead nonstoichiometry and a proposed local hydroxyl/oxide charge-balance mechanism remain distinguished from directly resolved substitution. Natural structural evidence and synthetic surface experiments concern separate specimens. No criticality designation, microbial mechanism or industrial recovery is inferred.

Microbial & Biochemical Mechanisms (1)

Abiotic dissolution-associated surface alteration of synthetic curite

other

Exsitu AFM showed etch pits after water and acidic treatments, with lower relief and greater lateral extent in the more acidic non-strontium arms. Strontium-bearing acid treatment produced differently shaped, more symmetrical pits. Alkaline carbonate treatment produced hillocks without observed etch pits; swelling and precipitation could not be distinguished. These are laboratory surface observations, not bulk uranium extraction yields, time-resolved dissolution rates or demonstrated radionuclide immobilization.

Experimental Context & Analytical Limits:
Synthetic crystals were prepared from 20 mL each of 0.1 mol/L uranyl acetate and Pb(NO3)2 solutions at 220 degrees C for two weeks; powder XRD detected no other phase. The dissolution methods describe 70 mg of crystals with 50 mL doubly distilled water or HCl-adjusted solutions at pH 3.5 and 2.1, and a separate 70 mg/50 mL arm with 0.1 mol/L Na2CO3 at pH 10.5. Strontium arms instead used 70 mg with 70 mL of 0.50 mol/L SrCl2, initially pH 5.5 or HCl-adjusted to pH 2.7. Methods prescribe 60 degrees C for 24 hours in Teflon Parr bombs, followed by water washing, air drying and contact-mode AFM in air on the (100) face in the 2006 paper's axis convention. Initial acid pH uncertainty was 0.1; final pH differed by at most 0.5 according to the authors. The pH 3.5 result separately says 12 hours, and the weakly acidic Sr result says pH 5.8; those discrepancies are unresolved. Replicate counts per arm and bulk dissolved uranium concentrations were not reported.
Curated Evidence Points:
Figures 4-6 show water and HCl etch-pit morphology and cross sections. Figure 7 shows the pH 2.7 SrCl2 pits; page 423 reports only three pits on the crystal examined after the weakly acidic Sr treatment. Figure 8 and page 423 show carbonate-associated hillocks and explicitly no observed pits. Absence of pits is not evidence that all dissolution ceased.
Pages 424-429 interpret pit geometry using edge protonation, bond-valence models and possible nonstoichiometric detachment or Sr adsorption. These molecular explanations were inferred, not directly measured. Pit depth is relief relative to an evolving surrounding surface, so Figure 9 is not a calibrated dissolution-rate dataset. The authors leave swelling versus precipitation unresolved and acknowledge undersaturation as an alternative contributor to increased acid pit density.
Context_only Source: schindler2006
Page 419 gives 24 hours for all treatments, but page 421 describes 12 hours for the pH 3.5 image. Methods and abstract give weakly acidic Sr pH 5.5, while page 423 gives 5.8. The abstract lists [110] among observed edges whereas the body and Figures 4-8 generally use [011]; disputed indices are not transferred as quantitative observations. The synthetic Sr analogue discussed as background is not the starting curite used in these dissolution experiments.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Curite row, PDF page 53; status and year definitions page 1. Fresh official PDF and row inspected.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-16)
  2. ghazisaeed2019: Ghazisaeed S, Kiefer B, Plasil J (2019). Revealing hydrogen atoms in a highly-absorbing material: an X-ray diffraction study and Torque method calculations for lead-uranyl-oxide mineral curite. RSC Advances 9:10058-10063. DOI 10.1039/C8RA09557D. Complete six-page published PDF and Europe PMC XML acquired; methods page 10059, Tables 1-3 and hydrogen limitations pages 10060-10062 inspected. Supplementary atom-coordinate files were not acquired; no deposited CIF was re-refined.
    https://doi.org/10.1039/C8RA09557D (accessed 2026-10-16)
  3. schindler2006: Schindler M, Mandaliev P, Hawthorne FC, Putnis A (2006). Dissolution of uranyl-oxide-hydroxy-hydrate minerals. I. Curite. Canadian Mineralogist 44:415-431. DOI 10.2113/gscanmin.44.2.415. Complete 17-page published PDF acquired from the coauthor's publication site. Methods pages 419-420; original AFM Figures 4-9 and results pages 420-426; interpretations pages 427-429 inspected. The received and accepted manuscript dates in 2005 are not the publication year.
    https://doi.org/10.2113/gscanmin.44.2.415 (accessed 2026-10-16)

Curation History

Timestamp Curator Action Summary
2026-10-16T06:50:17Z codex (GPT-6; codex) CREATE Added verified curite identity and scoped synthetic surface dissolution with source conflicts and interpretation limits.

Record source: data/records/curite.yaml