Raman spectroscopic study of the uranyl minerals vanmeersscheite U(OH)4[(UO2)3(PO4)2(OH)2]·4H2O and arsenouranylite Ca(UO2)[(UO2)3(AsO4)2(OH)2]·(OH)2·6H2O

Raman and infrared spectra of secondary uranyl phosphate vanmeersscheite and Raman spectrum of secondary uranyl arsenate arsenuranylite were recorded and interpreted, and the spectra related to the structure of the minerals. Observed bands were attributed to the stretching and bending vibrations of uranyl, phosphate and/or arsenate units and OH (H2O and OH−) units. Phosphuranylite sheet topology is characteristic for both minerals. U–O bond lengths in uranyl were calculated from the spectra and compared with those inferred for vanmeersscheite from the X-ray single crystal structure analysis. OH⋯O hydrogen bonds in both minerals were also inferred using the Libowitzky empirical relation.