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Sklodowskite mineral

Sklodowskite is the magnesium uranyl silicate hydrate mineral Mg(UO2)2(SiO3OH)2(H2O)4·2H2O in the September 2026 IMA list, equivalent in bulk composition to Mg[(UO2)(SiO3OH)]2·6H2O. It has monoclinic C2/m symmetry and is distinct from copper-bearing cuprosklodowskite. IMA status G and year 1924 mean grandfathered species and original description, not a numbered approval accession. New natural-crystal data in Plášil 2018 refine hydrogen positions and distinguish its interlayer linkage from the copper mineral. A separate 1997 experiment formed synthetic sklodowskite from synthetic boltwoodite under hydrothermal MgSO4 treatment. Neither uranium or magnesium content alone establishes criticality, microbial activity or industrial recovery.

Microbial & Biochemical Mechanisms (1)

Abiotic hydrothermal formation from boltwoodite

other

Synthetic boltwoodite treated with aqueous magnesium sulfate produced an air-dried solid identified as sklodowskite by powder X-ray diffraction. The treatment establishes formation of the magnesium mineral under the reported laboratory conditions; it does not resolve ion exchange versus dissolution and reprecipitation, quantify conversion, or demonstrate recovered uranium or magnesium product yield.

Experimental Context & Analytical Limits:
Vochten and colleagues suspended synthetic boltwoodite in 2 mol/L MgSO4, using a Teflon vessel in a Parr reaction bomb at 185 degrees C and reported pressure 1.3 MPa for 24 hours. After cooling and centrifugation they tested the supernatant for potassium using sodium tetraphenylborate and repeated the procedure until no trace was detected. The number of cycles, detection limit, solid loading, solution volume, treatment pH and independent replicates were not supplied for this Mg arm. Its synthetic precursor was prepared in a separate hydrothermal synthesis; that precursor's pH 11.5, seven-day duration and reagent amounts do not define the MgSO4 transformation conditions. The other Ca, Pb and Na salt arms produced other minerals.
Curated Evidence Points:
The page-736 synthesis paragraph explicitly pairs MgSO4 with sklodowskite. Powder diffraction of the air-dried product and Table 4 give a monoclinic cell with a = 17.372(2), b = 7.058(5), c = 6.6216(4) angstrom and beta = 105.890(8) degrees. Page 740 describes Cu K-alpha-1 diffraction with a silicon internal standard and powder indexing and refinement. These values belong to synthetic product and are not substituted for the later natural-crystal refinement.
A negative qualitative supernatant potassium test is not a measured zero-potassium solid or a quantitative conversion endpoint. Product mass, phase fractions, dissolution kinetics and sklodowskite-specific aqueous uranium concentrations were not reported. The solubility experiments and Table 3 concern synthetic boltwoodite, not sklodowskite. The Na arm's Teflon-derived fluorinated byproduct is reported separately and is not assigned to the Mg arm. No industrial treatment or microbial participation was tested.
Context_only Source: plasil2018
Section 2.1 reports new single-crystal data from the Museum of Natural History in Luxembourg collection; it does not equate that diffraction specimen with the photographed Kamoto-East specimen in Figure 2c. Table 2 and the CIF agree on R1 = 1.96% for 836 reflections above I > 3 sigma(I), and C2/m symmetry. Section 3.1 revises the earlier hydroxyl-site inference and distinguishes Mg linkage to silicate oxygen from Cu linkage to uranyl oxygen in cuprosklodowskite. Table 2 gives beta = 105.882(14) degrees while the CIF gives 105.882(3); that uncertainty difference is unresolved. The CIF has incomplete publication metadata and a Cu0 term in its formula sum, neither of which establishes a copper-bearing species or another publication. This study supplies mineral identity, not a replication of the 1997 transformation.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Sklodowskite row on PDF page 201; status/year definitions on page 1. Fresh authority PDF visually inspected: Mg(UO2)2(SiO3OH)2(H2O)4·2H2O, G, 1924.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-16)
  2. plasil2018: Plášil J (2018). Mineralogy, Crystallography and Structural Complexity of Natural Uranyl Silicates. Minerals 8(12):551. DOI 10.3390/min8120551. Complete original 15-page article, publisher XML and original supplementary archive inspected. Primary new natural-crystal measurements occur in section 2.1, Table 2 and sklodowskite_final.cif despite the Review article label; section 3.1 and Figure 4b discuss the structure and corrected hydroxyl position.
    https://doi.org/10.3390/min8120551 (accessed 2026-10-16)
  3. vochten1997: Vochten R, Blaton N, Peeters O, Van Springel K, Van Haverbeke L (1997). A new method of synthesis of boltwoodite and of formation of sodium boltwoodite, uranophane, sklodowskite and kasolite from boltwoodite. The Canadian Mineralogist 35:735-741. Complete original seven-page article inspected through the public RRUFF document library, including Figures 1-3 and Tables 1-4. Sklodowskite formation is on page 736 and its powder-derived cell parameters are in Table 4 on page 740. No DOI was verified for this article in the bounded identifier search.
    https://www.rruff.net/doclib/cm/vol35/CM35_735.pdf (accessed 2026-10-16)

Curation History

Timestamp Curator Action Summary
2026-10-16T01:34:23.344602Z codex (GPT-6; codex) CREATE Added sklodowskite with natural crystal identity and synthetic hydrothermal formation, preserving repeated treatment and missing quantitative conversion details.
2026-10-16T01:47:37.102800Z codex (GPT-6; codex) EDIT Corrected the synthetic product c parameter to 6.6216(4) angstrom from Vochten1997 Table4 after independent review, addressing issue 432.

Record source: data/records/sklodowskite.yaml