Raman and infrared spectroscopic study of boussingaultite and nickelboussingaultite

The Raman and infrared spectra of two secondary sulphate minerals, boussingaultite [(NH4)2Mg(SO4)2·6H2O] and nickelboussingaultite [(NH4)2Ni,Mg(SO4)2·6H2O] have been collected. Two bands observed at 983 and 990 cm−1 were attributed to the ν1(SO42−) 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 ν3(SO42−) antisymmetric stretching vibration. The splitting of the ν4(SO42−) 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 ν2(SO4) 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 NH4+ bending vibration region were observed at 1705 and 1678 cm−1 (ν2), 1460 and 1438 cm−1 (ν4) for the mineral boussingaultite. In the high wavenumber region the bands arising from the OH (bands above 3000 cm−1) and the NH4+ (2940, 2918 and 2845 cm−1) stretching vibrations were identified.