Electron diffraction data for some members of the metatorbernite group

The metatorbernite group of minerals is characterized by the formula A^z(UO₂XO₄)_z·nH₂O, where A may be almost any monovalent or divalent cation, and X may be P or As. These minerals have received a great deal of study, but there are still problems concerning the crystallography of some members of the group. Different authors arrive at different results in the determination of unit cell and space group (Alver and Sellevol, 1957; Donnay and Donnay, 1955; Nuffield and Milne, 1953; Ross, 1963; Ross, Evans and Appleman, 1964; Ross and Evans, 1965; Takano, 1961; Volborth, 1959).