The present paper deals with the synthesis of porous, sintered glass-ceramics obtained at temperatures below 1150 degrees C, originating from inorganic polymers based on fayalite slag. Firing led to the evaporation of water, dehydroxylation, and oxidation of Fe2+ above 345 degrees C. For heating > 700 degrees C, the Si-O stretching band shifted from the 1160 and 750 cm(-1) to the 1255 and 830 cm(-1) region, due to a structural reorganization of the amorphous phase, whereas Fe-O bands appeared at 550 cm(-1). The final microstructure consisted predominantly of an amorphous phase, hematite, and franklinite. The open porosity and compressive strength decreased and increased, respectively, as the firing temperature increased. The final values suggest properties comparable to that of structural lightweight concrete, still, the materials synthesized herein, are lighter, and made primarily from secondary resources.