NMR-SPECTRA OF MOGANITE AND CHALCEDONY

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