Beudantite mineral

Beudantite is the lead ferric arsenate-sulfate hydroxide mineral with ideal formula PbFe3(AsO4)(SO4)(OH)6, distinct from phosphate-bearing corkite, plumbojarosite, segnitite and elemental lead or arsenic. The September 2026 IMA list records its redefinition by special procedure in 1987; that date is not an individual approval accession. Szymański (1988) examined compositionally zoned natural material from Tsumeb, Namibia. Electron-microprobe analyses showed variable Al substitution for Fe and variable As/S ratios rather than a uniform ideal endmember. The accepted single-crystal refinement was crystal 2, with a = 7.3151(9) and c = 17.0355(5) angstrom, R-3m symmetry, 644 unique reflections and a final R factor of 3.7 percent. It supported disordered As/S sites and displaced Pb positions. Crystal 1 had unresolved diffraction-profile problems; crystal 3 showed a slight triclinic distortion but could not be satisfactorily refined and its composition was not determined. Neither the preferred symmetry nor the proposed Pb lone-pair explanation is generalized to every specimen. The article's separately deposited structure-factor Table 4 was not acquired; the published experimental methods, Tables 1-3/5 and Figures 1-3 support this bounded identity assessment. Bari et al. (2024) provide adjacent abiotic dissolution context for a synthetic solid they call beudantite. Its reported bulk formula, Pb0.32(H3O)0.68Fe3(AsO4)0.32(SO4)1.68(OH)6, differs markedly from the ideal species, and initial TEM-EDX detected grains lacking both As and Pb. Their 56-day tests at initial pH 2, 4, 6 and 8 used 0.06 g solid in 40 mL solution at 22 degrees C with triplicate sacrificial sampling. Filtered aqueous element contents, residual diffraction and arsenic X-ray absorption measurements describe that substituted, heterogeneous preparation. Greater mobilization at pH 2 and persistent residual diffraction do not establish dissolution rates or long-term stability of pure natural beudantite. No phase-specific dissolution mechanism is assigned here from those data. The source's inconsistent Fe unit, duplicated sulfate in its reaction equation, and comparison to an ideal Fe/Pb ratio despite the measured composition are not adopted as quantitative or balanced-reaction claims. These sources do not establish microbial transformation, isolated-product recovery or industrial operation. No constituent-element criticality is inherited.

Record source: data/records/beudantite.yaml