Slate from the Cambrian succession of North Wales is a well-known source of building products from the United Kingdom and is here advocated as a suitable “Global Heritage Stone Resource”. Its first recorded use was in the Roman period in Wales, and subsequently from the sixteenth century throughout the British Isles. During the 16th and 17th centuries several small companies worked the slate belt from Bethesda to the Nantlle valley but in the mid-18th these were gradually taken over or amalgamated and three large operations came to dominate the industry: Penrhyn, Dinorwic, and the Moel Tryfan to Dorothea group of quarries. From the late eighteenth century production expanded rapidly supplying markets worldwide especially to northern Europe and the British colonies. Slate has been used in all its forms but most notably as roofing slates in the construction of buildings at all levels in society and for buildings of the highest historical and architectural importance. Modernisation of the industry has enabled Cambrian Welsh Slate to continue to be quarried today in an environmentally sensitive manner by Welsh Slate Ltd.