Cambergi Slate Quarry is located to the north-west of Aberllefenni, on the north side of the valley of the Afon Llefenni, a tributary of the Dulas. It is a steep-sided location in which hillside terraces are spectacularly developed on nine levels with an incline down to the valley floor where there was a water-powered mill. There were some tentative attempts to work underground. The quarry may have used the Aberllefenni tramroad. The workings were short-lived, operating for only a few years around the 1880s. They are portrayed on the Ordnance Survey first-edition map of 1889 but by the second edition of 1901 the quarry was portrayed as 'Disused'.

The main feature of the surviving remains (in 1991) is a five-pitch incline, though much degraded. There are also several ruined drumhouses and dressing sheds. On the valley floor, are remains of the mill which contained several saw-tables driven by a shaft in a massive underfloor tunnel powered by a wheel behind and below the mill. Associated is a leat from a reservoir some distance up valley with a tunnel taking the tailrace to the river.

Sources:
A.J.Richards, A Gazeteer of the Welsh Slate Industry (1991), p.189.
OS County Series 25-inch maps: sheet Merionethshire XLII.4.

David Leighton, RCAHMW, 15 January 2015