A clay purification process, for removing impurities recovered with the clay, particularly a montmorillonite clay, includes the steps of separating the clay from rocks and other large non-clay impurities; dispersing the clay and smaller impurities in water, preferably at a concentration of at least about 4% by weight clay, based on the total weight of clay and water, more preferably about 6-10% by weight clay in water, to provide a clay slurry; passing the clay slurry through a series of hydrocyclones to remove the larger particles (impurities) while retaining clay particles having a size of about 100 microns or less, particularly about 80 microns or less; ion exchanging the clay to remove at least about 95% of the interlayer, multivalent (e.g., divalent and trivalent) cations in an ion exchange column, wherein the multivalent ions are replaced by monovalent cations, such as sodium, lithium and/or hydrogen; and then centrifuging the clay to remove a majority of the particles having a size in the range of about 0.5 .mu.m to about 100 .mu.m.