A medium-grained sedimentary rock composed of abundant rounded or angular fragments of sand size set in a fine-grained matrix (silt or clay) and more or less firmly united by a cementing material (commonly silica, iron oxide, or calcium carbonate); the consolidated equivalent of sand, intermediate in texture between conglomerate and shale. The sand particles usually consist of quartz, and the term sandstone, when used without qualification, indicates a rock containing about 85-90% quartz (Krynine, 1940). The rock varies in color, may be deposited by water or wind, and contains numerous primary features (sedimentary structures and fossils). Sandstones may be classified according to composition of particles, mineralogic or textural maturity, fluidity index, diastrophism, primary structures, and type of cement (Klein, 1963). (b) A field term for any clastic rock containing individual particles that are visible to the unaided eye or slightly larger.