The zone of collision between the continental plates that led to the formation of the Wicklow Mountains also led to mineralisation and the formation of Ireland's most significant metalliferous belt. The most important mining sites have been at Avoca and Glendalough. Mining has taken place at Avoca since at least the Bronze Age (c. 2,500-600 BCE). Iron ore extraction took place between the 12th and 17th centuries before being replaced by lead mining up to the mid 18th century. The principal activity from 1720 to the closure of the last mine in 1982 was copper extraction. Sulphur has also been extracted at certain times and, in smaller quantities, gold, silver and zinc. Lead mining has been the principal activity in the Glendalough valley and its neighbouring valleys of Glendasan and Glenmalure. Lead was first discovered in Glendasan in the early 19th century and the lead veins were later followed through Camaderry mountain to Glendalough. Mining on a smaller scale took place in Glenmalure. Ore from these mines was shipped to Ballycorus for processing. The last mine closed in 1957.