Metastudtite mineral
Metastudtite is the uranyl peroxide dihydrate mineral UO4·2H2O, equivalent in composition to (UO2)(O2)(H2O)2. The September 2026 IMA list gives approved status A and approval accession 1981-055. It is distinct from studtite, other uranium hydrates, elemental uranium and uranium commodities. The original description concerns natural Shinkolobwe material and a separate heated natural-studtite mixture; modern thermal and aqueous experiments used synthetic substrates. A particular historical structure model is not asserted as the unique current structure. No criticality, microbial activity, isolated uranium recovery or industrial deployment is inferred.
Identifiers & Classification
| System | Identifier | Label |
|---|---|---|
| IMA |
IMA:1981-055
|
Metastudtite |
Microbial & Biochemical Mechanisms (3)
Abiotic production in a heated natural studtite mixture
other
Heating natural studtite-bearing fibers produced a powder pattern dominated by metastudtite together with curite. The experiment supports a hydrate transformation in a mixed natural specimen; it does not establish a phase-pure product or a quantitative yield.
Experimental Context & Analytical Limits:
Deliens and Piret heated yellow studtite fibers with a reddish core at 100 degrees C for two hours. Their separately analyzed natural metastudtite fibers also contained uranium-lead hydrate material in the cores. Natural morphology alone was unreliable: historical collection fibers labeled studtite included studtite, metastudtite and lepersonnite.
Deliens and Piret heated yellow studtite fibers with a reddish core at 100 degrees C for two hours. Their separately analyzed natural metastudtite fibers also contained uranium-lead hydrate material in the cores. Natural morphology alone was unreliable: historical collection fibers labeled studtite included studtite, metastudtite and lepersonnite.
Curated Evidence Points:
Support
Source:
deliens1983
Page 457 and Table 1 identify metastudtite plus curite after the two-hour treatment. Table 1 distinguishes the authors' heated natural-studtite pattern from natural metastudtite, a prior synthetic preparation and an earlier heated specimen. These columns are not replicate measurements of one substrate.
Partial
Source:
deliens1983
Natural fibers gave additional reflections attributed to uranium-lead hydrates; neither a pure precursor nor full conversion was established. The historical irreversibility statement cites earlier work and is not a controlled reversibility test in this experiment. The paper's printed calculated-density unit is inconsistent with an ordinary mineral density and is not adopted.
Abiotic decomposition of metastudtite formed during studtite heating
other
Metastudtite formed in situ during heating of synthetic studtite subsequently lost crystalline diffraction features and developed amorphous uranium-bearing products. Dehydration and peroxide loss are supported interpretations; a single pure final oxide and a unique molecular pathway were not established.
Experimental Context & Analytical Limits:
Spano et al. synthesized the starting studtite from equal volumes of 0.5 M uranyl nitrate and 30 percent H2O2, washed and air-dried it, and heated samples from approximately 25 to 250 degrees C. PXRD and Raman measurements were in air every 5 degrees C; TGA used approximately 25 mg in continuous argon after a 30-minute equilibration at 25 degrees C. Nominal rates of 1, 2, 5 and 10 degrees C/min differed from effective PXRD rates 0.075-0.080 and Raman rates 0.830-3.283 degrees C/min because of measurement dwell times. Metastudtite was an intermediate of these experiments, not an independently identical pure starting powder for every thermal arm.
Spano et al. synthesized the starting studtite from equal volumes of 0.5 M uranyl nitrate and 30 percent H2O2, washed and air-dried it, and heated samples from approximately 25 to 250 degrees C. PXRD and Raman measurements were in air every 5 degrees C; TGA used approximately 25 mg in continuous argon after a 30-minute equilibration at 25 degrees C. Nominal rates of 1, 2, 5 and 10 degrees C/min differed from effective PXRD rates 0.075-0.080 and Raman rates 0.830-3.283 degrees C/min because of measurement dwell times. Metastudtite was an intermediate of these experiments, not an independently identical pure starting powder for every thermal arm.
Curated Evidence Points:
Support
Source:
spano2020
Proof pages E-I and Figures 3, 7-11 document loss of metastudtite diffraction and changes in uranyl/peroxo Raman bands. PXRD product-dominant crossovers averaged 144.0 +/- 1.8 degrees C under the long-dwell protocol. Raman model-derived crossovers ranged from 195.7 to 206.2 degrees C across the nominal rates. These method-dependent crossovers are not onset temperatures or a universal stability boundary. Table 3's second-order kinetic model is a fit to TGA conversion data, not independent proof of one elementary chemical reaction.
Partial
Source:
spano2020
Pages G and I and Figures 8 and 11 retain residual peroxide spectral contributions and differing mass losses at 250 degrees C. No run reached the theoretical 21.4 percent loss expected for full conversion of the starting studtite to U2O7. The authors explicitly leave final amorphous-product speciation unresolved. Starting-material water retention, probe depth, sample amount, heating schedule and air-versus-argon conditions limit direct comparison of techniques. The paper's Pnma metastudtite model is historical evidence, not a newly verified unique structure for all natural and synthetic metastudtite.
Abiotic early metastudtite formation on peroxide-exposed U3O8
other
Metastudtite was the largest identified alteration-phase contribution after one day on synthetic U3O8 exposed to peroxide, followed by studtite-dominated alteration spectra from day eight onward. Dissolution/reprecipitation was proposed; direct reversible solid-state hydration of an isolated metastudtite substrate was not tested.
Experimental Context & Analytical Limits:
Chamberlain et al. used separate approximately 50 mg alpha- and beta-U3O8 powders in 50 mL solutions with measured initial H2O2 concentrations 0.16, 0.0030 or 0.000054 M. Water-only U3O8 and peroxide-only controls were included. Beakers prepared in ambient atmosphere were parafilm-sealed between sampling; pH strips gave approximately 6.5 and no numerical incubation temperature was specified. Solid aliquots were air-dried for at least four hours before analysis. Fifteen Raman spots per aliquot represented spatial subsampling rather than independent reaction replicates.
Chamberlain et al. used separate approximately 50 mg alpha- and beta-U3O8 powders in 50 mL solutions with measured initial H2O2 concentrations 0.16, 0.0030 or 0.000054 M. Water-only U3O8 and peroxide-only controls were included. Beakers prepared in ambient atmosphere were parafilm-sealed between sampling; pH strips gave approximately 6.5 and no numerical incubation temperature was specified. Solid aliquots were air-dried for at least four hours before analysis. Fifteen Raman spots per aliquot represented spatial subsampling rather than independent reaction replicates.
Curated Evidence Points:
Support
Source:
chamberlain2025
Figure 4 and Tables S-2-S-4 and S-6-S-8 support the surface-phase succession in peroxide-added arms, with unaltered U3O8 often remaining the largest total component. Metastudtite's fitted contribution was reduced rather than uniformly exactly zero after day eight. For alpha-U3O8 in 0.16 M H2O2, Table S-2 gives 0.49734 on day 1 and 0.0225 on day 8; these normalized PLSR contributions are not bulk mass fractions or recovery yields.
Partial
Source:
chamberlain2025
Pages 10-11 explicitly limit conclusions to surface alteration. Small nonzero alteration components occur in fitted water-control spectra, without obvious SEM morphological change. Continuing U3O8 reaction, air drying before analysis and reference-spectrum selection prevent assigning the later studtite exclusively to dissolution of metastudtite or proving solid-state rehydration. The authors call for mechanism studies. Their observations limit an unconditional irreversibility claim; they do not establish reversible equilibrium, bulk conversion rates or a microbial process.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Metastudtite row, PDF page 142; status and accession 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) -
deliens1983: Deliens M, Piret P (1983). Metastudtite, UO4·2H2O, a new mineral from Shinkolobwe, Shaba, Zaire. American Mineralogist 68:456-458. Complete three-page published PDF inspected, including Table 1 and Figure 1. Natural specimens RGM 13748 and 13755; heated-studtite experiment page 457. No DOI verified.
https://msaweb.org/AmMin/AM68/AM68_456.pdf (accessed 2026-10-16) -
spano2020: Spano TL, Niedziela JL, Shields AE, McFarlane J, Zirakparvar A, Brubaker Z, Kapsimalis RJ, Miskowiec A (2020). Structural, Spectroscopic, and Kinetic Insight into the Heating Rate Dependence of Studtite and Metastudtite Dehydration. Journal of Physical Chemistry C 124:26699-26713. DOI 10.1021/acs.jpcc.0c09082. Complete 15-page OSTI 1735445 accepted-manuscript deposit inspected; it has proof pagination A-O and placeholder final page numbers. Methods B-C, Table 1 C, Figures 3-14 D-L and discussion M. Locators use that proof, not an inspected final published layout.
https://doi.org/10.1021/acs.jpcc.0c09082 (accessed 2026-10-16) -
chamberlain2025: Chamberlain CE, Spano TL, Hunt R, Burns PC, Miskowiec A (2025). Rehydration of metastudtite in the alteration kinetics of alpha- and beta-U3O8 in dilute aqueous solutions of hydrogen peroxide. Journal of Nuclear Materials 615:155941. DOI 10.1016/j.jnucmat.2025.155941. OSTI 3002745 complete 48-page accepted manuscript inspected, with main text pages 1-28 and appended supplement pages 29-48. Methods pages 4-11, Table 1 pages 5-6, Figure 4 page 12, Tables S-1-S-9 pages 32-38. Separate additional SEM ZIP not acquired. Locators refer to manuscript pagination, not final published layout.
https://doi.org/10.1016/j.jnucmat.2025.155941 (accessed 2026-10-16)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-16T05:16:46.772692Z |
codex (GPT-6; codex) | CREATE | Added verified mineral identity and scoped abiotic transformations with natural/synthetic, method and reversibility limits. |
Record source: data/records/metastudtite.yaml