The results of a 29Si NMR study of the 2:1 magnesium ribbon silicates, sepiolite and palygorskite are presented. Separate resonances between −92 and −98 ppm for the three and two types, respectively, of silica units across the ribbons are observed. This provides information on factors other than tetrahedral aluminium substitution which can affect the Q3 chemical shift. Also observed is a Q2 SiOH resonance from crystal defects or edges. The structural changes which occur at the various stages of dehydration have been studied. Finally, some interesting observations on 29Si relaxation and cross-polarization dynamics are presented.