CMMMech
CMMMech > Mineral > Billietite

Billietite mineral

Billietite is the barium uranyl oxide hydroxide hydrate mineral Ba(UO2)6O4(OH)6(H2O)8, distinct from elemental uranium, barium commodities and other uranyl oxide hydrates. The September 2026 IMA list gives grandfathered status G; 1947 is its original-description year, not an approval accession. Finch and colleagues refined a natural Shaba, Democratic Republic of Congo crystal in orthorhombic Pbn21, with two distinct uranyl polyhedral sheets linked by barium and interlayer water. Their eight-water refinement supersedes the incomplete four-water structural model discussed in that paper. Hydrogen bonding was inferred from geometry and bond valence; it was not a direct localization of all hydrogen atoms. The natural crystal used for structure refinement and the specimens used for surface experiments are separate evidence populations. No criticality, microbial mechanism or industrial recovery is inferred.

Microbial & Biochemical Mechanisms (1)

Abiotic surface etching and precipitation on natural billietite

other

Acidic exposure produced etch pits whose morphology depended on the electrolyte and initial surface state. Water and alkaline carbonate treatments produced different surface features. The observations establish laboratory surface alteration, with dissolution and precipitation occurring together; they do not quantify bulk uranium extraction or an intrinsic dissolution rate.

Experimental Context & Analytical Limits:
Natural Shaba specimens came from the William Pinch collection at the Canadian Museum of Nature. Each room-temperature experiment placed one platy crystal in a polyethylene cup containing 10 mL of solution. Non-freshly cleaved set 1 surfaces were exposed to pH 2 HCl or acidified electrolyte for 1.5 hours; freshly cleaved set 2 surfaces were exposed for 2 hours. Selected electrolytes were 1 M KCl and 0.5 M Pb(NO3)2 or SrCl2. Separate set 1 arms used ultrapure water for 24 hours or 0.1 M Na2CO3 at pH 10.5 for 1.5 and 24 hours. Samples were washed with ultrapure water, air-dried and examined by AFM in air within one hour, with optical microscopy and SEM. Numerical room temperature and replicate counts per condition were not reported. Surface freshness and acid exposure time changed together between sets.
Curated Evidence Points:
Figure 3 shows irregular, merging acid etch pits and water-induced hillock or ripple features; Figure 4 shows carbonate-associated stripes and steps. Figure 5 and pages 952-954 distinguish KCl etch pits elongated along [310] on non-freshly cleaved surfaces from [100] on freshly cleaved surfaces. Figure 8 and page 954 report an unidentified Pb-bearing precipitate without observed etch pits in the non-fresh Pb arm, but [010]-elongated pits in the fresh Pb arm. Sr arms showed [010]-elongated pits on both surface preparations. The absence of pits in one Pb arm is retained and is not interpreted as absence of all dissolution.
Hillocks and the Pb-bearing precipitate were not assigned a uniquely demonstrated crystalline product. Proposed cation adsorption sites and bond-protonation effects are explanatory models, not directly measured atomic pathways. Page 958 states that AFM pit depth is relief relative to adjacent material, not absolute vertical dissolution. Consequently Figure 10's relief ranking is not a ranking of bulk dissolution rates. Exsitu washing, drying, surface coatings and differing exposure times limit attribution of differences to electrolyte alone.
Context_only Source: schindler2007
Table 1 lists BaCl2 where methods and Figure 5 describe CaCl2; that disputed salt arm is excluded from the accepted recipe. Figure 7's Mg/Na caption names becquerelite although surrounding text discusses billietite; it is not used as unambiguous billietite evidence. The abstract's general [100] KCl statement does not erase the [310] non-fresh-surface exception. The 2007 text also gives c = 7.563(5) angstrom while the original 2006 refinement gives 7.1563(5); no cell parameter is transferred from the discrepant secondary transcription.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Billietite row, PDF page 26; 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. finch2006: Finch RJ, Burns PC, Hawthorne FC, Ewing RC (2006). Refinement of the crystal structure of billietite, Ba[(UO2)6O4(OH)6](H2O)8. Canadian Mineralogist 44:1197-1205. DOI 10.2113/gscanmin.44.5.1197. Complete published article acquired through RRUFF; original text and relevant structural tables and figures inspected. Natural specimen and refinement pages 1198-1199; interlayer water and inferred hydrogen bonding pages 1201-1204. Deposited structure factors were not acquired or re-refined.
    https://doi.org/10.2113/gscanmin.44.5.1197 (accessed 2026-10-16)
  3. schindler2007: Schindler M, Hawthorne FC, Halden NM, Burns PC, Maurice PA (2007). Dissolution of uranyl-oxide-hydroxy-hydrate minerals. III. Billietite. Canadian Mineralogist 45:945-962. DOI 10.2113/gscanmin.45.4.945. Complete 18-page published article acquired from the coauthor's publication site and inspected. Methods and Table 1 pages 949-951; acid, water and carbonate morphologies Figures 3-4; KCl Figure 5; Pb and Sr Figure 8; interpretation and limitations pages 954-960. Direction labels below retain this paper's stated morphological-axis convention.
    https://doi.org/10.2113/gscanmin.45.4.945 (accessed 2026-10-16)

Curation History

Timestamp Curator Action Summary
2026-10-16T05:59:16.057710Z codex (GPT-6; codex) CREATE Added verified identity and scoped natural-crystal surface dissolution with explicit source discrepancies and limits.
2026-10-16T06:03:26.246788Z codex (GPT-6; codex) EDIT Corrected 10 mL as solution volume rather than vessel capacity after independent review issue 476.

Record source: data/records/billietite.yaml