Operated at the western end of the Cathole Vein, along the eastern bank of the River Alyn. This area, owned by the Grosvenor family, characterized by steep Carboniferous Limestone valleys, was historically mined on a small scale.

The primary mining activity took place along the River Alyn at SJ 1965 6280, with the main shafts positioned atop the limestone cliffs. Four capped and fenced shafts remain on the cliff tops—two associated with Glan Alyn (SJ 1970 6291) and two with the True Blue Mine (SJ 1975 6305). Additionally, the True Blue Adit is located at SJ 1930 6320, north of the Glan Alyn Adit at SJ 1950 6290, both on the east bank of the river.

Transport infrastructure likely included an incline railway, which would have been used to move materials between the main Glan Alun mine shaft and the valley floor. This incline may have been installed in a gulley previously used for pump rods connected to a water wheel dating back to 1870.

Water power played a crucial role in the mine’s operations. Williams (1987) documents significant investment in water-driven systems along the River Alyn. A waterwheel, installed between 1772 and 1774 at SJ 1962 6294, initially powered pump rods leading up to the Pen-y-garreg Wen Shaft. As the mine expanded, a larger wheel replaced the original. In 1864, the 1774 wheel was modified to accommodate a turbine. The remains of a later, 40-foot waterwheel, constructed in 1870 for mine drainage, still stand at SJ 1960 6285.

A highly intricate “leete” (water channel) system was built throughout the Alyn Valley to facilitate mine drainage. Though initially developed in the 18th century, most of the system was constructed between 1823 and 1845 under John Taylor’s management of the Mold Mines (Williams, 1987). One of the earliest segments, the corn mill leat, was later extended to supply water to Glan Alyn Mine (SJ 1981 6265). Well-preserved sections of the leete remain today, with measurements indicating it was approximately 7 feet wide and between 4 feet 6 inches to 5 feet deep.

At Pen-y-garreg Wen Shaft (SJ 1986 6292), a horse whim was reportedly in use, while True Blue Mine employed a rope hoist for lifting materials.

The ore processing areas were located along the banks of the River Alyn at SJ 1960 6285, where dressing floors once stood.