The old True Blue Mine worked the eastern end of the Deborah vein, located in what is now part of Loggerheads Country Park. Evidence of these old shafts can be found in the woodland of Coed Pwll-y-blawd on the east bank of the River Alyn, specifically at SJ 1945 6320. Four capped and fenced-off shafts are situated on top of the limestone cliffs, two of which are attributed to Glanalyn (SJ 1970 6291) and two to True Blue Mine (SJ 1975 6305). The shafts seem to have been ladder shafts or windlass. The True Blue Adit is located at SJ 1930 6320, to the north of the Glan Alyn Adit (SJ 1950 6290), on the east bank of the River Alyn.

Documentary evidence, including early leases deposited at CRO, Hawarden and referenced in Williams (1987), confirms small-scale workings in this area on land owned by the Grosvenors on Mold Mountain.