Diffusioosmosis is the flow of a fluid driven by concentration gradients. Although a small effect in many instances, in low permeability rocks such as feldspars, it can have a significant impact on the rates of weathering.The novel aspect of this work is that the surface properties of the mineral are determined from a self-consistent solution of the chemical equilibrium equations for the surface and the electrostatic equations for the double layer. Because the fluid velocity is determined by a balance of competing and cooperating effects, it is remarkably sensitive to small changes in the system parameters, such as pH, electrolyte concentration, or the substitution of one ion (K⁺) for another (Na⁺).