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Sabugalite mineral

Sabugalite is the aluminium uranyl phosphate hydrate mineral H0.5Al0.5(UO2)2(PO4)2·8H2O in the September 2026 IMA list, with grandfathered status G. The year 1951 denotes the original description, not a numbered IMA approval. Frondel's original HAl(UO2)4(PO4)4·16H2O formula uses twice this formula unit. The mineral is distinct from magnesium saléeite, calcium autunite or meta-autunite, and elemental aluminium or uranium. The original study distinguished natural Portuguese material by chemical analysis, optics and powder diffraction, while documenting mixed specimens and uncertainty in the historical symmetry assignment. Its thermal experiments support laboratory dehydration of a particular natural specimen, not an industrial uranium recovery process. No criticality or microbial mechanism is inferred from composition or mineral occurrence.

Microbial & Biochemical Mechanisms (1)

Abiotic laboratory dehydration of natural sabugalite

other

Heating natural sabugalite changed its water content and optical properties, then its powder diffraction pattern. Frondel assigned the strongly heated product to a historical meta-II hydrate by comparison with heated autunite; this is the source's phase interpretation and does not establish a separately verified modern mineral species or recovered uranium product.

Experimental Context & Analytical Limits:
The study heated fresh air-dried material from Mina da Quarta Seira, Sabugal, Portugal, to reported essentially constant weight at 44, 68, 101, 117, 135 and 165 degrees C. An unheated air-dried sample provided the comparison. Powder X-ray diffraction and optical examination assessed products; Table 5 gives the 135-degree-C product's Cu/Ni pattern. Heating durations, rate, atmosphere, humidity, sample masses and replication were not specified. Subsequent exposure to a moist atmosphere at room temperature tested changes in optical properties and diffraction, without a reported exposure duration or numerical humidity.
Curated Evidence Points:
Pages 677-678 and Tables 5-6 report unchanged powder patterns after heating to 44 or 68 degrees C, mixed original and new patterns at 101 or 117 degrees C, and a new source-assigned meta-II pattern at 135 or 165 degrees C. Table 6 reports losses of 3.4, 20, 57, 63, 82 and 91 percent of the original water, respectively, not percentages of total mineral mass or uranium recovery. These are results of the particular historical assay, not universal transition temperatures.
Page 678 states that even products with one powder pattern were optically heterogeneous and attributes this to varying water content and insufficient heating time to reach equilibrium. This limits the earlier constant-weight description and prevents an equilibrium dehydration boundary from being inferred. Pages 678-679 report that moist-air exposure lowered refractive indices, but the highly heated products retained the meta-II powder pattern under the reported conditions. That observation does not establish irreversible behavior under every hydration regime. Unheated material immersed in water retained its pattern; no quantitative dissolution rate was measured.
Context_only Source: frondel1951
The Mina da Quarta Seira chemistry sample was separated in heavy liquids and described as optically homogeneous after removal of quartz and meta-autunite. The Kariz analysis instead retained an estimated five percent meta-autunite admixture; its water-by-difference and a separate direct-water measurement are not interchangeable. Neither composition is a pooled feed assay. Page 679 also reports unsuccessful sabugalite syntheses: uranyl nitrate, aluminium chloride and phosphoric acid produced source-assigned hydrogen-autunite; aluminium-acetate precipitation and exchange in 1 N aluminium chloride were negative. These null results concern those preparations, not proof that sabugalite cannot be synthesized by other routes. Later synthesis and controlled-rate thermal studies require separate full-text and publication-version checks before extending this record.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Sabugalite row, PDF page 190: H0.5Al0.5(UO2)2(PO4)2·8H2O, G, 1951; definitions on page 1. Fresh authority PDF acquired and the row visually checked.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15)
  2. frondel1951: Frondel C (1951). Studies of uranium minerals (VIII): Sabugalite, an aluminum-autunite. American Mineralogist 36:671-679. Complete original nine-page article and Tables 1-6 visually inspected; specimen chemistry on pages 674-675, dehydration and negative synthesis results on pages 677-679. Table 6 reports loss of original water, not mineral-mass loss.
    https://www.rruff.net/doclib/am/vol36/AM36_671.pdf (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T23:50:58.469480Z codex (GPT-6; codex) CREATE Added current-IMA sabugalite identity and the original natural-sample dehydration experiment, preserving assay limits, phase uncertainty and negative synthesis results.

Record source: data/records/sabugalite.yaml