Raspite and studtite: Raman spectra of two unique minerals

The Raman and IR spectra of monoclinic naturally occurring raspite, α‐PbWO 4 (space group P 2 1 / a ) were measured; it is irreversibly transformed to the tetragonal stolzite, β‐PbWO 4 , by heating to 450°C, and this process was followed by Raman spectroscopy. Assignments of fundamental modes are proposed. New data are also presented on single crystals of stolzite (space group I 4 1 / a ), and it is shown that raspite and stolzite can easily be distinguished by their Raman spectra. We also present Raman and IR spectroscopic data on natural and synthetic studtite, UO 4 ·4H 2 O, and its synthetic dehydration product metastudtite, UO 4 ·2H 2 O, the only two naturally occurring peroxide‐containing minerals, and on partially deuterated synthetic forms of these materials. Assignments of fundamental modes are proposed and both TGA and DSC data are presented for studtite.