Hafod-y-wern slate quarry was located on enclosed land on the east side of the Gwyrfai valley, above Betws Garmon. It began as a small working but developed into a substantial undertaking with the coming of the railway. Originally a hillside working, it deepened into three pits accessed by tunnels. Material was carried down by incline to mills located at the valley floor. The mills were water-powered, the 2nd edition of the historic 25-inch O. S. map depicting two embanked ponds on the hillside and an aqueduct leading to the southernmost building on the mill site. A branch of the North Wales Narrow Gauge Railway ran right to the mill. In 1898 the quarry employed 49 men but after several years of small-scale working it closed in the mid-1920s.
Bulk excavation and clearance has disturbed much of the site, and the upper part of the site now lies in forestry. In 1991 remains of one incline were still evident with a ruined drumhouse at its head. The railway branch track bed was still prominent.

Sources:
A.J.Richards, A Gazeteer of the Welsh Slate Industry (1991), p.90.
Slate quarry, depicted in-use on OS County series (Caernarvon. XVI.14 1890, 1900, 1915).
RCAHMW air photos: AP94-CS 1014; AP945130/62.

RCAHMW, 28 May 2015