Raman spectroscopic detection of wyartite in the presence of rabejacite

Abstract

AbstractRaman microscopy was used to confirm the presence of wyartite, CaU5+(UO2)2(CO3)O4(OH)(H2O)7, in the presence of rabejacite, (Ca(UO2)4(SO4)2(OH)5·6H2O), 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 ν2 symmetric bending mode of the (CO3)2− units. The presence of carbonate is confirmed by the ν1 stretching vibration at 1071 cm−1 and the ν3 stretching vibrations at 1445 and 1345 cm−1. Two bands are observed at 853 and 837 cm−1 and are assigned to the ν1 stretching modes of the UO2 units. Raman spectroscopy allows the partial band separation of the ν2 (CO3)2− and ν1 modes of UO2. The Raman spectrum of rabejacite is characterized by an intense sharp band at 1010 cm−1 assigned to the ν1 stretching mode of (SO4)2−. Three bands observed at 1086, 1123 and 1175 cm−1 are attributed to the ν3 antisymmetric stretching modes of (SO4)2−. The mineral rabejacite is also characterized by ν2 bending modes at 457 and 394 cm−1 and ν4 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 © 2004 John Wiley & Sons, Ltd.