A Fourier investigation, of a glycerol-solvated soil montmorillonite, derived from olivine basalt, has been carried out. The investigation showed that the calculated formula [K.10Na.02H1.00] [Si6.36Al1.61[Al.82Fe3+2.30Fe2+.08Mg.48Ti.08] O18..36(OH)5.64was essentially the correct formula for the dehydrated mineral. In an electron density map of the mineral, partial resolution of the O-H and C-H planes of ions of the glycerol molecule was achieved. It was not possible to resolve the densities of the octahedral cations from those of the adjacent plane of oxygen-hydroxyl ions nor those of the tetrahedral cations from those of the adjacent plane of oxygen ions.