Many geological and technological processes depend on diffusion in crystalline silicates and oxides, but models of the dynamics of diffusion have only rarely been based on relatively direct microscopic information on the rates and energetics of the hopping of cations from site to site. Two-dimensional nuclear magnetic resonance (NMR) exchange spectra for lithium-6 in lithium orthosilicate (Li(4)SiO4) provided a detailed picture of the hopping rates of Li+ ions among structurally distinct sites and helped to define the diffusion pathway. Rates and activation energies depended measurably on site geometry, and bulk electrical conductivity was accurately predicted.