Order-Disorder Effects in Minerals

If the various aluminosilicate units present in a mineral can be resolved sufficiently for their relative populations to be simulated, the Al-for-Si disorder can in principle be determined. In practice, the resonances from the various structural units often overlap, making it necessary to deconvolute the broad spectral envelope by curve-fitting procedures. Gaussian peaks are most commonly fitted, since they allow good visual fits to 

Determination of the distribution of Si over the various aluminosilicate units by curve fitting provides an accurate and eonvenient method of obtaining the Si/Al ratio of the aluminosilicate framework by applying Loewenstein s Rule. This proeedure has been used in conjunction with Al NMR in a structural study of NaY zeolite stabilised 

The availability of NMR probes capable of operating at elevated temperatures up to 600-700°C has opened up the possibility of studying temperature-induced processes in minerals. The thermal changes in analcime have been studied in situ by multinuclear NMR including Si (Kim and Kirkpatrick 1998). Pre-melting processes in lithium and sodium metasilicates have also been studied by Si NMR at temperature (George et al. 1998). 

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