The dispersion electrokinetic behavior and rheology of two mineralogically similar muscovites with subtle differences in their bulk chemistry (low-Fe versus high-Fe substitution) were investigated as functions of pH and temperature. At 25 degrees C, the zeta potentials of both samples were quite similar for dilute dispersions with a common isoelectric point (iep) at pH approximate to 2. For concentrated dispersions, the high-Fe-substituted particles displayed lower zeta potential and higher iep values than the low-Fe-substituted particles. The incongruent leaching of Fe(III), Al(III), Si(IV), and K+ ions from muscovite particles was facilitated by both higher Fe substitution and lower pH. Temperature elevation to 70 degrees C marginally enhanced the cations' leaching rates but suppressed Si(IV) release. The yield stresses of the two dispersions were similar in the pH ranges of 4-9 and 1-9 at 25 and 70 degrees C, respectively, and notably characteristic of dispersed sols/weak gels. At 25 degrees C and pH < 3, however, the high-Fe-substituted dispersion displayed an unusually strong gel structure. In contrast, the low-Fe-substituted dispersion remained dispersed. These observations reflect the different pH- and temperature-mediated muscovite-mineral-specific leaching and pulp chemistry behaviors that prevailed under the investigated conditions.