NMR-SPECTRA OF MORGANITE AND CHALCEDONY

Si-29 MAS NMR, Si-29 {H-1} CP MAS NMR and H-1 MAS NMR spectra of the w ater-containing micro-crystalline silica varieties chalcedony, moganit e.and three intermediate samples are reported. The Si-29 MAS NMR spect ra give evidence that, unlike quartz, the silicon atoms occupy two sym metrically different sites in moganite. The H-1 MAS NMR spectra show s ignals of molecular water and four different species of silanol groups .