slate

Slate is composed of shale, with fine grains of quartz, mica and other minerals. It is metamorphic, meaning that it has been transformed from its original state by massive pressure and heat. The material has been used in building for centuries, with quarries in North Wales known to have been in operation since Roman times. Slate is often thought of as grey, but actually comes in every shade of the colour, from pale through to nearly black. It can also be found in green, purple and blue. Much of the satisfaction for Joe derives from the splitting or riving of the slabs, when the chisel reveals surfaces which have been hidden from sight for many millions of years.