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On the labyrinthine crystal-chemistry of boleite, a Pb-Ag-Cu hydroxyhalide

  • G. Diego Gatta ORCID logo EMAIL logo , Giorgio Guastella , Pierino Malizia , Tommaso Battiston , Marco Merlini , Geoffrey Bromiley and Oscar Fabelo
Published/Copyright: October 3, 2025
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American Mineralogist
From the journal American Mineralogist Volume 110 Issue 10

Abstract

The chemical composition and crystal structure of boleite from the Amelia Mine (Boléo District, Mexico) were investigated by a series of chemical analytical techniques and single-crystal X-ray (data collected at 293 K) and neutron diffraction (at 20 K). The concentrations of more than 60 elements were measured. The empirical formula of boleite, based on the multi-analytical approach, is: (K0.390Ca0.165Na0.095Rb0.075Cd0.040Cs0.035Tl0.002)Σ0.80Pb26.05Ag8.93Cu23.91Cl61.64(OH)48.39, of which the simplified formula should be given as (K,Ca,Na,Rb,Cd,Cs)Pb26Ag9Cu24Cl62(OH)48. However, as Cd can also be considered as a potential substituent for Ag or Cu, the simplified formula transforms to (K,Ca,Na,Rb,Cs)Pb26Ag9Cu24Cl62(OH)48. This finding indicates a more complex scenario with respect to the previous formula reported in the literature, i.e., KPb26Ag9Cu24Cl62(OH)48. Chemical data obtained in this study show no significant evidence of potential substituents of Pb, Ag, and Cu; the concentrations of REE, PGE, and other industrially relevant elements are insignificant. Despite a lack of crystallographic evidence, chemical data appear to suggest that partial Cl− vs. OH− substitution can occur. Other potential substituents of Cl−, such as F−, have not been detected at a significant level. X-ray and neutron diffraction data confirm the previously reported general structural model of boleite but consistently show that a substitutional disorder affects the K site, manifested by a large and unusual displacement parameter. The magnitude of the displacement parameter reflects static disorder, in the form of substitutional disorder, due to differences in the local bonding topology among K, Ca, Na, Rb, (Cd), and Cs statistically populating the same site. The H-bonding network in the structure of boleite is now unambiguously described on the basis of the neutron structural model, with two energetically favorable bonds, both having an Odonor-H···Clacceptor configuration. The structure of boleite does not contain H2O molecules but, instead, only two crystallographically independent hydroxyl groups.

Keywords: Boleite; crystal chemistry; X-ray diffraction; neutron diffraction; hydrogen bonding

Acknowledgments and Funding

The authors thank the Institut Laue-Langevin (Grenoble, France) for the allocation of the neutron beamtime (DOI: 10.5291/ILL-DATA.5-11-452). X-ray (with KUMA diffract.) and EPMA-WDS data were collected using the facilities of the UniTech COSPECT – University of Milan (Italy). G.D.G., T.B., and M.M. acknowledge the support of the Italian Ministry of Education (MUR) through the projects “Dipartimenti di Eccellenza 2023–2027.” The Associate Editor, Oliver Tschauner, and an anonymous reviewer are warmly thanked for the revision of the manuscript.

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Received: 2024-12-14
Accepted: 2025-02-23
Published Online: 2025-10-03
Published in Print: 2025-10-27

© 2025 Mineralogical Society of America

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https://doi.org/10.2138/am-2024-9721
Keywords for this article
Boleite; crystal chemistry; X-ray diffraction; neutron diffraction; hydrogen bonding

Articles in the same Issue

  1. Theoretical studies of thermodynamic and elastic properties of diamond under Earth’s mantle conditions
  2. Natrojarosite formed in the Matanomadh Formation, Kutch, India: A Na analog of jarosite on Mars
  3. Moxuanxueite, NaCa6Zr(Si2O7)2OF3, a new wöhlerite-group mineral from Gejiu alkaline complex, Yunnan Province, China
  4. EBSD mapping of Cu-Fe-sulfides reveals microstructures enriched in critical/precious metals and resolves deformation histories
  5. The sulfate-bearing associations of fumarolic environments of Somma-Vesuvius volcano (Italy): A review from historical samples (Royal Mineralogical Museum of Naples)
  6. Snowball quartz in highly fractionated peraluminous granites: An indicator of multiple magma degassing
  7. Oxybarometry of reduced silicate glasses: Using multivariate methods to constrain Cr oxidation states with application to lunar glasses
  8. Nigelcookite, PbFe22+V23+(PO4)3(OH)3,and plumbojohntomaite, PbFe22+Fe23+(PO4)3(OH)3,two new members of the bjarebyite group from the Yushui Cu deposit, South China
  9. Rare occurrence of jarosite-alunite solid solutions with intermediate Al-Fe contents in the Jurassic Aztec Sandstone, Nevada, U.S.A
  10. Olgafrankite, Ni3Ge, a new mineral as the carrier of siderophile germanium in reduced systems
  11. Fuyuanite [Mg7Nb6O18(OH)8], a new hydrous magnesic-niobic oxide mineral from the Bayan Obo deposit, China
  12. Laboratory synthesis, spectroscopic characteristics, and thermal behavior of phoxite
  13. Sublattice disorder and Fe-Mg substitution in brucite: Implications for the subduction-zone water cycle
  14. On the labyrinthine crystal-chemistry of boleite, a Pb-Ag-Cu hydroxyhalide
  15. Book Review
  16. Book Review: Exoplanets: Compositions, Mineralogy, Evolution
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