A metamorphic rock that's formed from shale is slate. Slate is a low-grade rock that's used as a building material. It is often used for roofing tile because of the ease with which it can be split into thin sheets. If slate is installed properly, it's also waterproof.
Slate is created when shale is compressed under moderately high temperatures. This compression can be due to the movement of the earth in a process called dynamic metamorphism. The pressure causes water to be squeezed out of the rock and the tiny clay mineral or mica grains in the shale to line up at right angles to the direction of the pressure. The pressure can also cause the resulting slate to be foliated. This means its materials are arranged in parallel bands.
Slate is often a gray rock with a matte luster and a very fine grain. It can also be green, black or purple. Slate quarries are found in Cornwall and the Lake District in England as well as Italy, Portugal, Brazil, Vermont and New York state. Slate was traditionally used for blackboards as well as roofing tiles.
Fossils are often found in slate. However, sometimes the formation of cleavage, or the plane through which the rock naturally breaks, deforms the rock to the point where any fossils are destroyed.