Despite similarities in the physical and physico-chemical properties of Na- and K-feldspars, their flotation separation with monovalent ions exhibited a reasonable success. Further studies have been therefore initiated to ascertain whether multivalent ions, i.e., Ca and Ba can widen the window of separation of individual feldspar minerals. Upon addition of multivalent ions, ion exchange between the added ions and those in the crystal lattice and ion adsorption in the electrical double layer occurs. The ionic size of Na and Ca cations and those of K and Ba cations are almost the same indicating the ability of exchange among each couple. The compatibility of this exchange determines the extent of surface modification with the added ions. In this study, amine flotation together with zeta potential measurements has been studied as a function of bivalent salts to understand their effects on differential separation of feldspar minerals. It is found that bivalent ions exhibit complex and yet interesting features of adsorption and ion exchange patterns. The mechanism of action is elaborated on the basis of flotation and zeta potential data. (C) 2003 Elsevier Science Ltd. All rights reserved.