Powder mixtures of NH4-exchanged zeolite A and MgO, and of NH4-exchanged mordenite and MgO were used as starting materials in the synthesis of crystalline ceramic materials. Conventional ball milling was applied in order to amorphize NH4-exchanged zeolites, reduce the particle size of MgO, and produce a homogeneous mixture. Solid-state transformation of the mixtures after heating at the temperature of their phase transformations in the interval 800 °C–1000 °C for 3 hours yielded crystalline forsterite (Mg2SiO4) with possible minor amounts of sapphirine (Mg4Al10Si2O23) in the first case, and to crystalline forsterite (Mg2SiO4) with traces of enstatite (MgSiO3) in the second case