A sedimentary, usually lacustrine, kaolinitic clay, derived from the intense weathering of granitic and other rocks to give a unique clay sediment with both plasticity and strength. Ball clays were originally cut into cubes but by the time they had been hauled from Bovey Tracey, Devon, UK, to Stoke-on-Trent where they were to be used, the cubes had been turned into balls as they jostled together in barges and carts, hence the name.