Under earth surface conditions between pH 4 and 10, the rates of primary silicate and oxide dissolution are controlled by surface reactions. For many oxides and hydroxides as well as some silicates, dissolution reactions can be modeled by surface complexation theory, which states that reaction rates are proportional to the population of surface complexes with H+, OH-, or ligands. The rate of release is controlled by the detachment of the complexes from the surface. This theory, however, fails to explain many observations including the dissolution of oxides at low pH, which is first-order with respect to solution H+, the dependence of rates on ionic strength, and the incongruent nature of the initial dissolution of most silicates. Rapid hydrolysis of charge balancing cations in silicates results in rapid release from surfaces. Even after removal of surficially exposed cations, the reaction is commonly incongruent. Much, but not all, of the nonlinear rates observed in silicate dissolution can be explained by the presence of high energy sites, such as dislocation outcrops, twinning planes, or damaged sites on ground mineral surfaces. These sites dissolve more rapidly than the bulk of the mineral, causing the high initial rates and producing etch pits, which results in increased surface area. The exact nature of the material remaining on reacted mineral surfaces (indicated by incongruence) is the subject of debate.