sentences:  Lead and zinc were intensively mined in the Cwmystwyth area of mid Wales and a lead mine operated at Minera near Wrexham from the Middle Ages until the early twentieth century.In Victorian times the Sygun Copper Mine was opened near Beddgelert in Snowdonia.Ironstone is a component of the Lower Coal Measures rock sequence and where it outcrops along the northern edge of the South Wales Coalfield, it was extensively worked for the production of iron and was important in the initiation of the Industrial Revolution in South Wales.