Two types of intercalated and exfoliated silicate platelets were allowed to disperse in phenol-cured epoxy matrixes. The different dispersing forms of these silicate platelets in the composites may alter their hardness, transparency, thermal stability, and coefficient of thermal expansion (CTE). In particular, the presence of silicate platelets in the epoxy substantially enhances the hardness of the pristine epoxy from 2 to 6 H by loading only 0.5 wt % of the exfoliated platelets but only to 4 H hardness by loading the intercalated form (pristine 58 angstrom d spacing). Analyses by X-ray diffraction, transmission electron microscopy (TEM), differential scanning calorimetry, thermal mechanics, and thermal gravimetry were performed to characterize these silicate-added epoxies. Physical properties including CTE and T-g were correlated with the silicate platelet dispersion in a matrix revealed by the TEM observations.