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Parauranophane mineral

Parauranophane is the calcium uranyl silicate hydrate mineral Ca(UO2)2(SiO3OH)2(H2O)4·H2O listed by IMA in September 2026. It is the historical beta-uranophane or uranophane-beta, renamed by CNMNC in August 2022. Rn, 2022 s.p. denotes that nomenclature action, not a unique approval accession. The alpha polymorph is the separate species uranophane; identical ideal composition does not make their experiments interchangeable. Cesbron and colleagues characterized natural beta material from Nopal I, Sierra Peña Blanca, Chihuahua, Mexico, by morphology and powder X-ray diffraction, including a refined monoclinic cell with space group P21/a in the reported setting. Their synthesis campaign produced uranophane but no beta polymorph under the tested conditions; its stability field remained unresolved. No criticality, microbial activity, extraction yield or industrial deployment is inferred from these mineralogical studies.

Microbial & Biochemical Mechanisms (1)

Abiotic acid exposure without a detected surface redox shift

other

The source's XPS comparison of natural fibrous beta-uranophane before and after acid exposure found similar fitted uranium-valence proportions. This is a bounded null surface-redox result, not proof of no dissolution, no surface alteration or universal resistance to reduction.

Experimental Context & Analytical Limits:
The natural crystals came from the William Pinch collection at the Canadian Museum of Nature and the Shinkolobwe mine, Democratic Republic of Congo. The beta-specific treatment used HCl at initial pH 3.5 for three hours at room temperature, in the study's mounted-single-crystal, 5-mL batch setup. Untreated cleaved surfaces supplied comparisons. XPS U 4f spectra were fitted to U(VI) and U(IV) components; these are surface spectral assignments, not bulk uranium speciation or product recovery measurements. Independent reaction replication and the beta-specific final solution pH were not clearly documented.
Curated Evidence Points:
Table 3's explicitly beta-labelled rows and Figure 3a-b show similar spectra before and after the pH-3.5, three-hour treatment. Section 4.6 interprets the comparison as no significant oxidation or reduction during that treatment. This narrow observation does not transfer the synthetic alpha-powder uranium-release ranking or alpha-surface coating identifications to parauranophane.
The methods and several figure captions use uranophane generically, while Table 3 separates fibrous beta specimens from alpha specimens. Table 3 labels the beta Ca-HCl treatment 60 minutes but Table 4 lists Ca-HCl at 30 minutes, so that arm is not adopted. Other unresolved source labels include Figure 3d's alpha treatment duration, Figure 8e's lead salt, and Figure 10d's sampling interval. Only the explicitly beta-labelled HCl comparison is accepted here. XPS analysis, washing, drying and vacuum exposure do not establish in-situ aqueous speciation; companion studies would need separate inspection before adopting their explanation for the original U(IV) component.
Context_only Source: cesbron1993
The independent natural Nopal I material has its own XRD evidence in Tables 1-2, not an identity inferred solely from yellow colour or uranium content. Figure 3 shows etched natural crystals and opal coatings but provides no measured environmental dissolution rate. About fifty hydrothermal preparations across several uranyl silicates, principally at 150 degrees C with some trials as low as 60 degrees C, did not produce beta-uranophane. Their failure is restricted to the tested preparations; it neither proves universal synthesis failure nor measures a thermodynamic stability boundary.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Parauranophane row, PDF page 166; formula, Rn and 2022 s.p.; definitions on page 1. Fresh authority PDF and original row visually inspected.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-16)
  2. cnmnc2022: Miyawaki R, Hatert F, Pasero M, Mills SJ (2022). IMA Commission on New Minerals, Nomenclature and Classification (CNMNC), Newsletter 69. European Journal of Mineralogy 34:463-468. DOI 10.5194/ejm-34-463-2022. Section 3, page 467 records the August 2022 approval of uranophane-beta becoming parauranophane and uranophane-alpha becoming uranophane.
    https://ejm.copernicus.org/articles/34/463/2022/ (accessed 2026-10-16)
  3. cesbron1993: Cesbron F, Ildefonse P, Sichere MC (1993). New mineralogical data on uranophane and beta-uranophane; synthesis of uranophane. Mineralogical Magazine 57:301-308. DOI 10.1180/minmag.1993.057.387.12. Complete original eight-page article from RRUFF visually inspected. Figures 1-4 and Tables 1-2 distinguish natural Nopal I material; pages 304-305 and 308 report negative beta synthesis. The 2018 online posting is not the publication year of the experiment.
    https://doi.org/10.1180/minmag.1993.057.387.12 (accessed 2026-10-16)
  4. schindler2009: Schindler M, Freund M, Hawthorne FC, Burns PC, Maurice PA (2009). Dissolution of uranophane: An AFM, XPS, SEM and ICP study. Geochimica et Cosmochimica Acta 73:2510-2533. DOI 10.1016/j.gca.2009.01.031. Complete coauthor-hosted original, all 24 pages, Tables 1-4 and Figures 1-13 inspected. The beta-specific acid-exposure comparison is in Table 3, Figure 3a-b and section 4.6; synthetic powder assays concern uranophane.
    https://doi.org/10.1016/j.gca.2009.01.031 (accessed 2026-10-16)

Curation History

Timestamp Curator Action Summary
2026-10-16T00:37:22.893936Z codex (GPT-6; codex) CREATE Added current-name parauranophane with historical-beta mapping, primary natural diffraction identity, negative synthesis context and a narrowly scoped null surface-redox comparison.

Record source: data/records/parauranophane.yaml