Relating to rocks formed when sediment is deposited and becomes tightly compacted. Depending on the origin of the sediments they contain, sedimentary rocks are classified as clastic sedimentary rocks, chemical sedimentary rocks, or evaporites. Sandstone and conglomerate, for example, consist of fragments of broken preexisting rocks or minerals and are classified as clastic sedimentary rocks. Limestone forms from the precipitation of calcium carbonate through water and is classified as a chemical sedimentary rock. Gypsum and halite deposits form through the evaporation of mineral-rich water and are classified as evaporites.