Raman and infrared spectroscopic study of boussingaultite and nickelboussingaultite

Abstract

The Raman and infrared spectra of two secondary sulphate minerals, boussingaultite [(NH 4) 2Mg(SO 4) 2·6H 2O] and nickelboussingaultite [(NH 4) 2Ni,Mg(SO 4) 2·6H 2O] have been collected. Two bands observed at 983 and 990 cm −1 were attributed to the ν 1(SO 4 2−) symmetric stretching vibration. The bands at 1133, 1096 and 1063 cm −1 in boussingaultite spectra and bands at 1149, 1093 and 1063 cm −1 in nickelboussingaultite spectra were attributed to the ν 3(SO 4 2−) antisymmetric stretching vibration. The splitting of the ν 4(SO 4 2−) bending vibration produced bands at 625 and 615 cm −1 in the boussingaultite spectra and 652, 624 and 602 cm −1 in the nickelboussingaultite spectra. Similarly, in the case of the ν 2(SO 4) bending vibration, the bands were observed at 454 cm −1 in the boussingaultite spectra and 482, 457 and 440 cm −1 in the nickelboussingaultite spectra. The splitting of bands is the result of lowered symmetry of sulphate ions and possibly a result of substitution of Mg ions by Ni ions in nickelboussingaultite. The bands in the NH 4 + bending vibration region were observed at 1705 and 1678 cm −1 ( ν 2), 1460 and 1438 cm −1 ( ν 4) for the mineral boussingaultite. In the high wavenumber region the bands arising from the OH (bands above 3000 cm −1) and the NH 4 + (2940, 2918 and 2845 cm −1) stretching vibrations were identified.