Raman spectroscopic detection of wyartite in the presence of rablejacite

Raman microscopy was used to confirm the presence of wyartite, CaU5+(UO2)(2)(CO3)O-4(OH)(H2O)(7), in the presence of rabejacite, (Ca(UO2)(4)(SO4)(2)(OH)(5)(.)6H(2)O), obtained from the Ranger Mine, Northern Territory, Australia. This occurrence is unusual in that it means that a uranyl carbonate has been formed under acidic conditions. Wyartite is a mineral known for the occurrence of pentavalent U5+. A band is observed at 818 cm(-1) in the Raman spectrum of wyartite assigned to the nu(2) symmetric bending mode of the (CO3)(2-) units. The presence of carbonate is confirmed by the nu(1) stretching vibration at 1071 cm(-1) and the nu(3) stretching vibrations at 1445 and 1345 cm(-1). Two bands are observed at 853 and 837 cm(-1) and are assigned to the nu(1) stretching modes of the UO2 units. Raman spectroscopy allows the partial band separation of the nu(2) (CO3)(2-) and nu(1) modes of UO2. The Raman spectrum of rabejacite is characterized by an intense sharp band at 1010 cm(-1) assigned to the nu(1) stretching mode of (SO4)(2-). Three bands observed at 1086, 1123 and 1175 cm(-1) are attributed to the nu(3) antisymmetric stretching modes of (SO4)(2-). The mineral rabejacite is also characterized by nu(2) bending modes at 457 and 394 cm(-1) and nu(4) bending modes at 666,605,537 and 505 cm(-1). Raman spectroscopy has proven most useful for the detection of wyartite in the presence of other mineral phases. Copyright (C) 2004 John Wiley Sons, Ltd.