Electrokinetic properties of a series of boron minerals, i.e., colemanite, ulexite, inderite, and tunellite, are investigated using the microelectrophoresis technique. Colemanite exhibits an isoelectric point at pH 10.5. Ulexite, inderite, and tunellite yield practically no isoelectric point in the pH range of 7 to 11. While ulexite remains negatively charged, inderite and tunellite show positive charges in the pH range studied. The potential determining ions for these minerals are the constituent lattice cations, Ca2+, Mg2+, and Sr2+, and the anion, B4O72-. The H+ and OH- ions which indirectly control the ratio of HCO3-/CO32- are also the potential determining ions for the hydrated boron minerals studied. The electrokinetic results generally support the adsorption of oppositely charged flotation collectors on boron minerals through electrostatic attraction. (C) 1995 Academic Press, Inc.