Wales has a large region rich in coal deposits called the South Wales Coalfield.
The South Wales Coalfield ( Welsh : Maes glo De Cymru ) is a large region of south Wales that is rich in coal deposits , especially the South Wales Valleys . Wales . At the dawn of the Industrial Revolution , development of the mining and metallurgical industries transformed the country from an agricultural society into an industrial nation ; the South Wales Coalfield 's exploitation caused a rapid expansion of Wales ' population .