The muscovite mica-electrolyte interface was investigated using an electrokinetic (electro-osmosis) technique after ion exchange and low temperature calcination at 300 degrees C. Samples calcined after ion exchange with H+ and K+ showed similar electrokinetic properties to the freshly cleaved sample whereas those calcined after ion exchange with either Li+ or Mg2+ ions showed a significant reduction in the magnitude of the zeta potential. This reduction was attributed to an irreversible fixation during calcination of Li+ and Mg2+ ions respectively to the basal plane of the muscovite mica. Modeling of the electrical double layer properties using a Gouy-Chapman-Stern-Grahame approach indicated that greater than 90% of the charge in the lattice had been neutralized by the calcination procedure.