Slate Slate Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression. The foliation in slate is called "slaty cleavage". It is caused by strong compression causing fine grained clay flakes to regrow in planes perpendicular to the compression. When expertly "cut" by striking parallel to the foliation, with a specialized tool in the quarry, many slates
Slate industry in Wales slate quarry near Machynlleth is now the site of the Centre for Alternative Technology. A number of the railways which carried the slates to the ports have been restored as tourist attractions, for example the Ffestiniog Railway and the Talyllyn Railway. The Welsh slate industry was essentially a Welsh-speaking industry. Most of the workforce in the main slate-producing areas of North Wales were drawn from the local area, with little immigration from outside Wales. The industry had a considerable influence on the culture of the area and on that of Wales as a whole. The "caban", the cabin where the