| Slate is the polychrome rock which can be split into thin sheets. It is a metamorphic rock formed from clay sediments. The sedimentary layers formed from clay are folded and produce cleavage planes at right angles to the direction of pressure. The principal minerals in slate are mica, chlorite and quartz. Slate was used from ancient times to make flat writing tablets, tombstones, roofing tiles and other objects that require a smooth, flat surface. Later the stone came into wide use in such items as roofing, flooring, paving, sinks, wall clading, and billiard tables. |
