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Zeunerite mineral

Zeunerite is the copper uranyl arsenate mineral Cu(UO2)2(AsO4)2(H2O)4·8H2O in the September 2026 IMA list, with grandfathered status G. The year 1872 denotes its original description, not a numbered IMA approval. Its ideal twelve-water composition is distinct from eight-water metazeunerite, phosphate torbernite, calcium meta-autunite and elemental uranium, copper or arsenic. Synthetic-crystal X-ray diffraction and a later partially deuterated synthetic-powder neutron study support P4/nnc models under their respective conditions. Hydrogen positions and disorder are model-dependent; these experiments do not establish natural-specimen homogeneity, long-term containment, a universal dehydration threshold or an extraction yield. No criticality or microbial activity is inferred from composition.

Microbial & Biochemical Mechanisms (1)

Abiotic laboratory crystallization of a synthetic zeunerite analogue

other

Copper, uranyl and arsenate reagents produced crystals or powder assigned to zeunerite by diffraction. Slow gel growth and solution precipitation are separate laboratory preparations; neither is a microbial process or a demonstrated industrial recovery operation.

Experimental Context & Analytical Limits:
Locock and Burns grew zeunerite at room temperature over three weeks by slow diffusion of reported 0.167 M H5As3O10 and 0.5 M uranyl-nitrate solutions into copper-bearing silica gel. A crystal was epoxy-coated to limit dehydration before room-temperature MoK-alpha single-crystal diffraction. Separately, MacIver-Jones precipitated material from uranyl nitrate in 0.2 M nitric acid, copper nitrate and arsenic acid, matured it for 48 h, filtered and washed it, and dried it at room temperature. Subsequent repeated reflux in D2O at 75 degrees C prepared the neutron sample; residual H was detected by FTIR. The zeunerite refinement used data collected at 50 degrees C, not an untreated natural crystal. Neither preparation supplies a mass-balanced metal recovery yield.
Curated Evidence Points:
Pages 490-492 and Tables 1, 3 and 7 support synthetic twelve-water zeunerite in P4/nnc. The refined cell is a = 7.1797(3) and c = 20.857(1) angstrom, with R1 = 1.6% for 468 observed unique reflections. Page 498 identifies pseudo-I-centering and argues that observed reflections require P-centering, disagreeing with the earlier Hennig et al. I4/mmm model. This is the authors' interpretation of their dataset, not an independent re-refinement here.
Hydrogen positions were refined with O-H distance constraints and fixed isotropic displacement parameters. Page 497 presumes equivalence to natural zeunerite from compatible cell dimensions; natural material was not the measured crystal. The hydrothermal 220-degree-C synthesis and twinning refinements belong to metazeunerite and are not zeunerite results. The inaccessible Hennig full text and CISTI reflection deposit limit independent adjudication of the competing model.
Printed pages 61-65 and 77-82, Figures 3.1-3.3 and Tables 3.1-3.4 support preparation and a P4/nnc neutron model of partially deuterated zeunerite at 50 degrees C, with twelve water molecules per formula unit. Figures 3.8-3.9 and pages 93-97 propose a split H/D site and hydrogen-bond network. The model used soft bond restraints and constrained displacement parameters; AIRSS verification was performed only for metatorbernite.
The source calls the sample container stainless steel in Chapter 2 but vanadium in Chapter 3. Copper occupancy uncertainty is 1.00(2) in prose versus 1.00(3) in Table 3.1; water-angle uncertainties also differ between prose and Table 3.3. Appendix 3.2 repeats a zeunerite caption despite phosphorus-labelled spectra, so it is not used as a zeunerite assay. The proposed hydrogen-bond explanation for greater stability than torbernite remains a hypothesis, with neutron analysis of torbernite requested as future work. Raw neutron runs were not reanalysed. No quantitative solubility, microbial mechanism or long-term field performance is established by this scoped structural evidence.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Zeunerite row, PDF page 240: Cu(UO2)2(AsO4)2(H2O)4·8H2O, G, 1872; definitions on page 1. Current authority PDF acquired and row visually checked.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15)
  2. locock2003: Locock AJ and Burns PC (2003). Crystal structures and synthesis of the copper-dominant members of the autunite and meta-autunite groups: torbernite, zeunerite, metatorbernite and metazeunerite. Canadian Mineralogist 41:489-502. DOI 10.2113/gscanmin.41.2.489. Complete 14-page original rechecked, especially pages 490-492, 497-499 and Tables 1, 3, 7 and 11. Figures 1-4 illustrate the phosphate analogues, not additional zeunerite experiments. CISTI reflection deposit remains unacquired.
    https://www.rruff.net/doclib/cm/vol41/CM41_489.pdf (accessed 2026-10-15)
  3. maciver_jones_thesis: MacIver-Jones F. The Structure, Stability, and Synthesis of Copper Autunite Minerals with Implications for Uranium Remediation. PhD thesis, University of Edinburgh. Institutional item 1842/40395, DOI 10.7488/era/3163, issued 2023-03-13 as MacIver-JonesF_2023.pdf; title page says 2021. Complete 272-page deposited PDF acquired; Chapters 2-3 (printed pages 61-107), including Figures 3.1-3.14, Tables 3.1-3.12 and Appendices 3.1-3.3 inspected. Zeunerite neutron results are thesis evidence; the linked 2021 IUCrJ paper and AIRSS calculations concern metatorbernite.
    https://era.ed.ac.uk/handle/1842/40395 (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T23:02:38.475765Z codex (GPT-6; codex) CREATE Added current-IMA zeunerite identity and separate abiotic synthetic preparations, with deposited-thesis neutron evidence, competing models and explicit version, assay, refinement and access limitations.

Record source: data/records/zeunerite.yaml