1. n. 
A clastic sedimentary rock whose grains are predominantly sand-sized. The term is commonly used to imply consolidated sand or a rock made of predominantly quartz sand, although sandstones often contain feldspar, rock fragments, mica and numerous additional mineral grains held together with silica or another type of cement. The relatively high porosity and permeability of sandstones make them good reservoir rocks.
See: barite, cement, chlorite, clastic sediment, clean, dirty, eolian, feldspar, gas sand, lamination, matrix, oil sand, permeability, porosity, quartz, reservoir, rock, sand, sedimentary, silica, siliciclastic sediment