Slate

Slate is a metamorphic sedimentary rock composed of clay or volcanic ash. It has a sheet-like planar structure, so it is almost always used in flat installations. It is typically cut by striking it parallel to the sheets, which gives the material a smooth and flat surface. It is usually seen in a dark gray color, but can be found in a variety of colors, even in the same quarrying location. Because it was formed under low heat and compression (compared to other rocks), it sometimes contains small fossils.

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Slate has long been used for man-made items. From Neolithic hunters that fashioned arrows from the material, to the roof of Roman forts in Wales, slate’s workability has made it favored in a number of applications. Industrialization in Europe drove demand for slate, where most slate is still quarried in Spain. Slate roofing declined in popularity with the development of cheaper alternatives in the 20th century.

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Slate is ideal for roofing as it has 0.4% water absorption, so it has been used as a roofing material in residential applications since 1300 AD. It is also fireproof, which provides protection from fireworks, wildfires and neighboring house fires. It is also often used in bathroom and landscape applications.