Slate

Slate is hard, dense, and fine-grained low-grade metamorphic rock that splits into thin slabs along planar surfaces. This splitting, known as slaty cleavage, results from recrystallization under pressure and commonly develops at an angle to the bedding planes. Slates are formed from clays, shale, volcanic ash, and other fine-grained rocks. Minerals present are quartz, sericite, chlorite, titanium oxide, and iron oxides.

Slate is commonly found in areas where shale has been subjected to heat and pressure during mountain building. Because of its physical characteristics and its cleavage, slate has been used form a great variety of surfaces in different forms of construction.