Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original Paper

Anthony R. Kampf, Stuart J. Mills

The role of hydrogen in tellurites: crystal structure refinements of juabite, poughite and rodalquilarite

Journal of Geosciences, volume 56 (2011), issue 3, 235 - 247

DOI: http://doi.org/10.3190/jgeosci.093

The crystal structures of the tellurite minerals juabite, CaCu₁₀(Te⁴⁺O₃)₄(AsO₄)₄(OH)₂(H₂O)₄, poughite, Fe³⁺₂(Te⁴⁺O₃)₂(SO₄)(H₂O)₂·H₂O and rodalquilarite, Fe³⁺₂(Te⁴⁺O₂OH)₃(Te⁴⁺O₃)Cl, have been refined to R₁ (F_o > 4sF) = 2.36%, 2.38% and 1.84%, respectively. The determination of H atom positions in all three structures has allowed the elucidation of the hydrogen bonding schemes and detailed bond-valence analyses. These are the only tellurite mineral structures for which H atom positions have been determined. The structures of all contain one-sided Te⁴⁺ coordinations as Te⁴⁺O₃ pyramids with additional anions at greater distances. The one-sided coordinations are attributable to the stereochemically active 6s² lone-electron-pair of the Te⁴⁺. The overall linkage schemes in these structures are quite different, yet all can be considered layer structures in which relatively weak long Te-O and/or Te-Cl bonds are involved in the linkages between layers. In juabite, a long apical Cu-O bond participates in the linkage between layers and, in poughite and rodalquilarite, hydrogen bonding also links the layers.