Clastic Rocks

Clastic Rocks, so named from the Greek klastos, broken, are taken by modern geologists to include not merely those commonly called fragmentary, such as gravel, shingle, breccia, or conglomerate, consisting obviously of pieces once broken off some earlier rock, but also all other rocks neither crystalline nor glassy, such as fine-grained sediments and precipitates, sand, clay, and gypsum, for example, and those rocks formed of organic remains, of which chalk and other limestones and coal are well-known types.