 Although slate quarrying has been described as 'the most Welsh of Welsh industries', it is coal mining which has become the single industry synonymous with Wales and its people.Initially, coal seams were exploited to provide energy for local metal industries but, with the opening of canal systems and later the railways, Welsh coal mining saw a boom in its demand.As the South Wales coalfield was exploited, Cardiff, Swansea, Penarth and Barry grew as world exporters of coal.