The three valleys were formed during the Ice Age approximately 20,000 years ago which helped to sculpture the U-shaped glacial valleys we see today and the two lakes in Glendalough.
Millions of years ago the collision of the continental plates resulted in the formation of the Wicklow Mountains into a large granite mass. As the granite eventually cooled, cracks appeared which became filled with the hot fluids creating various minerals. Cooling and chemical reactions caused metal ores to be deposited as veins in the cracks. In the Wicklow Mountains, lead and zinc are the main ores to be found, although small quantities of silver were also extracted from the lead ore.
The earliest documented lead mine in operation in Co. Wicklow was at Ballinafunshoge in Glenmalure. It was discovered in 1726 and mining work began as early as 1783. Mining in the other valleys dates back to the turn of the nineteenth century when the Government commissioned a survey of gold in County Wicklow not long after the 1798 rebellion. A rich vein of lead ore was discovered in the Glendasan valley. Over the course of 150 years the exploration of mineral deposits was extended over the three valleys with mine sites and processing plants established in Glendasan at Luganure, Ruplagh, Hero, Fox Rock and Moll Doyle, in the Glendalough valley and at Van Diemen’s Land Mine and in Glenmalure at Ballyfunshoge, Ballinagoneen and Baravore.