- GeoRef, Copyright 2004, American Geological Institute.
NMR spectroscopy with magic-angle spinning was used to study two smectites, two illites and a vermiculite. 27 Al NMR was able to directly observe the coordination of aluminum. 29 Si NMR was sensitive to both the chemical nature of the interlayer species and the presence of aluminium in the tetrahedral sheet. Well-resolved resonances in the vermiculite at delta = -84.6, -88.7 and -92.9 (ppm relative to TMS) were assigned to Q 3 (2Al), Q 3 (lAl) and Q 3 (0Al) respectively. The smectites exhibited single resonances centred at delta = -93 (Q 3 (0Al)). The illites displayed broad resonances between delta = -80 and -105. The 29 Si spectrum of a smectite complexed with alkylammonium cations showed a shielding of up to 1 ppm relative to the untreated sample.