Open-cast mining began at Ballycorus around 1807 on the western side of Carrickgollogan hill, close to the later site of the flue chimney. The site was taken over by the Mining Company of Ireland (MCI) in 1826 who undertook underground mining in the area up until 1863. This activity was carried out on an intermittent basis on account of the discontinuous nature of the vein and depending on lead prices. A vein of silver was discovered in 1843 but production was limited.