sediment composition in a clastic rock is determined by
Clastic sedimentary rocks form when individual grains (the sediment), made by fragments of rocks, minerals, or shells, are cemented together (the clastic sediemntary rock).These are the only type of rock that is NOT made simply of crystals, but rather fragments of other materials, broken and then reassembled together.ediment is a general term that indicates loose grains (such as the sand at the beach) and chemical precipitates (such as crystals of salt). Sedimentary rocks can be subdivided in three categories: clastic, chemical, and biochemical sedimentary rocks.