Slate is as old as the planet we live on and it has been quarried and split to provide roof coverings for hundreds of years. British slate, predominantly from North Wales and Cumbria, has a reputation for being the best in the world. It is not uncommon to find a British slate roof still in perfect condition up to 200-years after it was laid. Slate is a fine-grained, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low grade regional metamorphism. Slate is a totally natural product that has been used for centuries. Slate has two lines of breakability – cleavage and grain – which make it possible to split the stone into thin sheets. When broken, slate retains a natural appearance while remaining relatively flat. Slate had been used for building since Roman times. It was used in the Roman fort in Segontium, Caernarfon, as well as Edward I’s castle in Conwy. But it was not until the 19th century that its use expanded considerably as it was adopted as the main roofing material of the industrial age.