Synthetic corundum (Al2O3), gibbsite (Al(OH)3), bayerite (Al(OH)3), boehmite (AlO(OH)) and pseudoboehmite (AlO(OH)) have been studied by high resolution XPS. The chemical compositions based on the XPS survey scans were in good agreement with the expected composition. High resolution Al2p scans showed no significant changes in binding energy, with all values between 73.9 and 74.4 eV. Only bayerite showed two transitions, associated with the presence of amorphous material in the sample. More information about the chemical and crystallographic environment was obtained from the O1s high resolution spectra. Here a clear distinction could be made between oxygen in the crystal structure, hydroxyl groups and adsorbed water. Oxygen in the crystal structure was characterised by a binding energy of about 530.6 eV in all minerals. Hydroxyl groups, present either in the crystal structure or on the surface, exhibited binding energies around 531.9 eV, while water on the surface showed binding energies around 533.0 eV. A distinction could be made between boehmite and pseudoboehmite based on the slightly lower ratio of oxygen to hydroxyl groups and water in pseudoboehmite.

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Lecontite, (NH 4 )Na(SO 4 ).2H 2 O, was synthesised at room temperature in high purity compared to earlier work with a minor impurity of mascagnite, (NH 4 ) 2 SO 4 . Rietveld refinement of the XRD results confirmed the crystal structure and unit cell dimensions as published earlier. Raman and Infrared spectroscopy, in conjunction with factor group analysis, resulted in a complex pattern of overlapping sulphate, NH and OH modes. The NH modes υ 1 was observed around 2880 cm -1 , υ 2 around 1700 cmoverlapping with water OH-bending modes, υ 3 around 3300 cm -1 overlapping with water OH-stretching modes around 3023, 3185 and 3422 cm -1 , and υ 4 around 1432, 1447 and 1462 cm -1 . The sulphate group in the crystal structure displays a decrease in symmetry from T d as evidenced by the activation of the ν 1 mode at 982 cm -1 and the ν 2 mode around 452 cm -1 in the Infrared spectrum. The υ 3 mode shows clear splitting in the infrared spectra with a strong band at 1064 cm -1 accompanied by two shoulders at 1107 and 1139 cm -1 . The Raman spectra show three weak bands at 1068, 1109 and 1135 cm -1 with a shoulder at 1155 cm -1 . Similar splitting was observed for the υ 4 mode around 611 and 632 cm -1 in the Infrared and Raman spectra, respectively.

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