Shale

Sedimentary

Shale is a fine-grained clastic sedimentary rock formed by the consolidation of clay, silt, or mud. It is characterized by finely laminated structure; this layering allows the rock to break in thin layers parallel to bedding. Shales form on lake bottoms and the deep sea-floor. Slate is the metamorphic equivalent of shale and can be distinguished by a sheen from aligned mica grains.