Infrared and Raman spectroscopy of tschermigite, (NH4)Al(SO4)2•12H2O

Abstract Tschermigite, (NH4)Al(SO4)2·12H2O, is a rather rare mineral of the alum group that occurs in such environments as burning coal seams, guano deposits and volcanic-related conditions in association with other hydrated sulphates. The remote identification of hydrated ammonium sulphates is relevant to volcanology and Martian mineralogy and require detailed vibrational characterization of reference species of which tschermigite can serve. The study provides analysis of infrared and Raman spectra of the mineral tschermigite that originate from low-temperature volcanic (geothermal) environment at Southern Kamchatka, Russia. The detailed analysis of tschermigite infrared and Raman spectra revealed that its signatures agree with structural and chemical characteristics. However, it was possible to distinguish stretching vibrations of ammonium ion from those of water molecules by infrared (8030, 6430, 3203, 3045, 2843 cm-1) and Raman (∼ 3163, 2883 cm-1) spectroscopy. The bending vibrations of ammonium are found ∼ 1680 cm-1, whereas H ˗ O˗H bending occurs ∼ 1630 cm-1. The data were compared to other hydrated ammonium sulphates, hydrated non-ammonium sulphates and mascagnite, (NH4)2SO4.