The Probert Encyclopaedia of Rocks & Minerals

SHALE

Shale is a fine black sedimentary rock that splits easily into thin plates along well-defined planes parallel to the original stratification. Shale is composed of a complex mixture of microscopic clay minerals plus mica and quartz. Shale is often rich in fossils and dinosaur tracks. Shale is formed in quiet water environments, such as lake bottoms, river floodplains, tidal flats, marshes and the floors of deep oceans, where the finest particles carried by the water have settled. These clays gradually petrify forming shale.
Research Shale