Mine workings to the east of the Bryn Mawr Chert Quarry, near Penyrhwylfa Farm and Penyrhwylfa Cottages. Shafts are still present at coordinates SJ 1902 7354, located to the west of Rose Cottage, while two disused shafts can be found at SJ 1903 7360, to the west of the farm. Additional shafts are situated along the northern edge of the quarry, following an east-to-west vein that runs from Bryn Hyfryd at SJ 1864 7372 towards Dolphin. At the eastern end of this vein, the mining workings have been cut by the A55 trunk road.