Forsterite was prepared via solid-state reaction by using hydromagnesite (basic magnesia carbonate) and fumed silica, aiming at completing the reaction 2MgO+SiO₂→Mg₂SiO₄ at low calcination temperature. The phase development and morphology evolution of the hydromagnesite and hydromagnesite–fumed silica mixture during heat treatment were characterized by means of scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) nitrogen-gas adsorption method, and X-ray powder diffraction (XRD). A diffusion distance of less than 300 nm for Mg²⁺ and Si⁴⁺ for forsterite formation was obtained because the formed high reactivity MgO with the nanosheet structure of its parental hydromagnesite and the fumed silica with particle size of less than 100 ...