Slate

is a fine-grained metamorphic rock easily split into smooth, flat pieces. Slate occurs in such colors as black, blue, green, purple, red, and grey. It is mainly composed of clay minerals, quartz, muscovite or illite, pyrite, and feldspar. Because of its cleavage and grain, slate readily breaks into sheets. Slate is generally used in construction for roofs, tiles, and flooring.