Sand-pulverizer
Any machine that will crush lumps and grind the particles of sand together, and thus produce a thorough blending of the materials employed for producing sand and loam mixtures in the foundry. The ordinary loam-mill and crusher may be classed as such; but for the purpose of mixing and sifting the finer grades of sand there are other excellent contrivances, with which, by means of a grinding-plate and vertical yielding bed set in below the hopper, the sand is pulverized and mixed, and finally delivered into a horizontal revolving screen to be sifted. See ROCK-CRUSHER; LOAM-MILL; SAND SCREEN.
Sandstone is a rock composed of siliceous or calcareous grains of sand cemented together by siliceous, calcareous, or ferruginous infiltrations, though the loose sand solidifies by pressure alone. The sand grains are invariably composed of quartz with a slight admixture of other minerals, which gives rise to the variations in color. Some of these sandstones, owing to the highly refractory nature of their composition, are occasionally employed as hearths of blast-furnaces, also for the beds of air-furnaces; but the want of homogeneity in the stone makes them liable to crack, and for this reason other refractory materials are generally preferred. See ROCK-SAND; FACING-SAND.