Abstract: A method of making a building block from waste particulate siliceous materials, such as fly ash, bottom ash, and rock mineral fines, includes employing a major amount of such waste particulate materials in combination with a calciferous additive and water to cure and shape the same under the influence of controlled pressure and temperature for a predetermined time to create building block which is characterized by a mineralogical crystalline phase. Preferred ratios of fine waste particulate material and coarser waste particulate materials are disclosed. The product produced by the method is also disclosed.