New Cambrian Slate Quarry lies to the west of Glynceiriog at the head of the valley formed by Nant Lafar, a tributary of the Afon Ceiriog. Open pit workings may have begun here as early as the seventeenth century, with underground extraction developed during the nineteenth century. A company was formed in 1857 to exploit the workings and substantial developments followed the opening of the Glyn Valley tramroad in 1873 (NPRN 309457), linking to a railway and canal at Chirk. Underground work began in the late 1890s. Working the quarry was made difficult by the piecemeal original layout, the necessity to uphaul rubbish (due to constraints of the site location), the faulted geology and the poor quality of the slate extracted. Output peaked at about 4000 tons per annum. The workforce numbered 73 in 1898 rising to 115 by 1938. But the Glyn Valley tramroad had closed in 1935 and by 1947 the quarry too had closed.
The entire site has been afforested with much demolition of the remains. Traces of former structures are highly degraded.

Sources:
Ordnance Survey County Series 25-inch maps: Denbighshire sheet XXXIX.10, editions of 1876, 1900 & 1912.
A.J.Richards, A Gazeteer of the Welsh Slate Industry (1991), pp.196-8.
RCAHM air photos: AP955027/62-64.

David Leighton & J.Wiles, RCAHMW, 15 January 2015