Sedimentary rock is a type of rock formed from the accumulation of sediment over time. SANDSTONE, shale, LIMESTONE, and siltstone are all examples of sedimentary rocks. SANDSTONE is a clastic sedimentary rock composed of sand-sized grains of mineral, rock, or organic material. Shale is a fine-grained sedimentary rock composed of clay-sized particles. LIMESTONE is a sedimentary rock composed mainly of calcium carbonate, often in the form of the minerals calcite or aragonite. Siltstone is a sedimentary rock composed of silt-sized particles.