Clastic Rocks

Clastic Rocks (Gr. klastos, 'broken'), secondary or derivative rocks, as composed of fragmental materials—e.g. conglomerate, sandstone, shale, &c., which have been formed out of the remains of previously existing rocks. Besides the large class of sand-and-gravel rocks, it also embraces many rocks of organic origin, such as certain Limestones (q.v.), composed of the debris of shells, corals, &c.; Coals (q.v.), made up of the remains of plants; some Ironstones (q.v.), consisting in whole or in part of organic debris. Fragmental volcanic rocks, such as Tuff (q.v.) and Agglomerate (q.v.), come also into the same division.