Prince Llewellyn Slate Quarry is located on the north side of the Lledr valley, to the south-west of Betws-y-coed. It is an open hillside quarry and pit with some later underground workings. It was established in about 1820 and had an output of 1685 tons (mainly slab) with 74 men in 1882; ouput may have been more in earlier years. The quarry is believed to have been an early user of saws, the original mill having four horizontal handsaws, rising to nine saw-tables and three planers with the building of a second mill. The mills also dealt with slate from Chwarel Fedw which was brought across the valley by tramroad on the still extant causeway. Variously, a 30 foot waterwheel, steam and water turbine were used for power, and possibly steam for pumping; a reservoir is located just above the site to the north. Product was carted out by road. The workings closed in 1917.

Sources:
Ordnance Survey County Series 25-inch map: Caernarvonshire sheet XXIII.11 (editions of 1889, 1900 & 1913).
A.J.Richards, A Gazeteer of the Welsh Slate Industry (1991), p.78.

David Leighton, RCAHMW, 14 January 2015