A processing method is presented for treating sludges from municipal and waste materials. The ashes from such sludges, containing SiO.sub.2 as a primary constituent, are treated with additives to tailor the feed material composition. Thermal processing, including melting, rapid cooling and subsequent annealing, produces a crystallized glass microstructure in which needle-shaped shaped crystals of anorthite and .beta.-wollastnite are infiltrated with a vitreous material. Such crystallized glasses having superior mechanical and aesthetic properties are an attractive architectural material which can be utilized for interior finishing, exterior walls, flooring as well as for interior decorations.