Rich veins in the area of Holywell Common were extensively worked starting in the early 18th century. Smith (1921) notes that both the True Blue Mine and the Cross Leavings Mine operated along the Garreg-Llwyd Vein in the early 19th century. Later, the larger Prince Patrick North Mine worked the same area to the north of the Pentre Halkyn to Babell Road, extending to the north and east of Pant-y-groes (SJ 1850 7260). The workings run northward toward the bank of limekilns at Waenbrodlas, situated west of the Pen-yr-Henblas Quarry.
