Workings can be traced running eastward from the old Cathole sett at SJ 2060 6270. Worked the E-W Pulkington and Cathole vein that runs eastwards from the River Alyn. At the eastern extent of the vein, the remains of the mine are situated on Gwernymynydd Farm. Several filled shafts are located in this area, including a shaft and horse whim platform at SJ 2220 6250, which is likely No. 1 Shaft or St. Catherine’s Whimsey. Other filled shafts of varying diameters can be found at SJ 2230 6255, SJ 2240 6255, SJ 2245 6260, SJ 2250 6260, and SJ 2250 6255. A mound at SJ 2270 6260 appears to be the result of waste dumping rather than a shaft.

The Lords of Mold initially worked St. Catherine’s Mine from the 1730s, which later became known as the Gwernymynydd Mine. In the 19th century, the Glan Alyn Mining Company took over operations, working a mine sett located to the east of the Cathole sett. The mining activity in this area continued under various operators, with the Brunner Mond Company managing the workings between 1896 and 1903.

Documented shafts associated with the Gwernymynydd Mine include No. 1 Engine Shaft, No. 2 Shaft (also known as Treasury Shaft), Tom and Jerry Shaft (which extended to 140 yards), Shaft Las, Rainbow Engine Shaft, Edwards Shaft, Williams Shaft, and Boundary Shaft.

During this period, a powerful Cornish engine was reportedly used to deepen the No. 2 Treasury Shaft to a depth of 200 yards.