“…Feldspar and feldspathoid crystals (like sanidine, trikalsilite, nepheline), known to give notably stable glasses, practically unable to crystallize, have been recently found as the main crystal phase of several sintered glass-ceramics. 15,17,18 Secondly, using fine glass powders may allow the incorporation of secondary phases, like alumina platelets, 14,15 useful for the preparation of strong glass-ceramic matrix composites. Finally, the fine powders may be useful for the preparation of cellular glass-ceramics, deposited on polymeric foams, by the so-called "replication process" (the polymeric foam models the solid fraction of the final cellular material), 19 or mixed with "foaming agents", i.e.…”