Some aspects of the structural relationship between “Messbach-Type” And “Lucin-Type” Yariscites

A comparative structural study of “Lucin-type” (VL) and “Messbach-type” (VM) variscites by X-ray diffraction and infrared spectroscopy has been performed.

Like “Lucin-type”, “Messbach-type” variscite crystallizes in the orthorhombic system, probably with the same space group Pcab. The lattice constants found for VM: a, 9.90₂, b, 9.65₉, c, 17.18₀ Å are, however, sufficiently different from those assigned to VL (a, 9.83₁b, 9.63₅, c, 8.55₅ Å), as to presume the existence of net structural differences. Infrared spectra support this assumption showing the existence of two different types of water molecules, which are present in both structures in different proportion. Some differences in the symmetry of PO₄^3-anions between both variscite types were also found.