Raman spectroscopic detection of wyartite in the presence of rabejacite

Raman microscopy was used to confirm the presence of wyartite, CaU 5+ (UO 2 ) 2 (CO 3 )O 4 (OH)(H 2 O) 7 , in the presence of rabejacite, (Ca(UO 2 ) 4 (SO 4 ) 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 U 5+ . A band is observed at 818 cm −1 in the Raman spectrum of wyartite assigned to the ν 2 symmetric bending mode of the (CO 3 ) 2− units. The presence of carbonate is confirmed by the ν 1 stretching vibration at 1071 cm −1 and the ν 3 stretching vibrations at 1445 and 1345 cm −1 . Two bands are observed at 853 and 837 cm −1 and are assigned to the ν 1 stretching modes of the UO 2 units. Raman spectroscopy allows the partial band separation of the ν 2 (CO 3 ) 2− and ν 1 modes of UO 2 . The Raman spectrum of rabejacite is characterized by an intense sharp band at 1010 cm −1 assigned to the ν 1 stretching mode of (SO 4 ) 2− . Three bands observed at 1086, 1123 and 1175 cm −1 are attributed to the ν 3 antisymmetric stretching modes of (SO 4 ) 2− . The mineral rabejacite is also characterized by ν 2 bending modes at 457 and 394 cm −1 and ν 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.