Sedimentary rock formed from sand-sized grains (0.0025–0.08 in., or 0.06–2 mm, in diameter). The spaces between grains may be empty or filled with either a chemical cement of silica or calcium carbonate or a fine-grained matrix of silt and clay particles. The principal mineral constituents of the grain framework are quartz, feldspar, and rock fragments. Sandstones are quarried for use as building stone. Because of their abundance, diversity, and mineralogy, sandstones are also important to geologists as indicators of erosional and depositional processes. See alsograywacke.