Synthesis of gallium oxide pillared fluorine micas has been undertaken by using hydroxogallium solutions having different OH/Ga ratios and aging conditions as pillaring agents. The gallium oxide pillared fluorine micas obtained from aged hydroxogallium solutions have larger basal spacings and higher specific surface areas than those obtained from freshly prepared hydroxogallium solutions. Thermal durability of the pillared structure depends on the aging conditions of the hydroxogallium solutions; thermal durability of the pillared micas was enhanced by using the solutions aged under the optimized conditions. The pillared micas obtained from the hydroxogallium solution (OH/Ga = 2.0) aged at room temperature for 24 hours retained larger basal spacings and specific surface areas even after heated up to 750 degrees C.