Graig Ddu quarry is a disused slate quarry near Blaenau Ffestiniog, in Gwynedd, North Wales. Although output was only about 3,000 tons a year, it reputedly has 36 saw tables and the same number of dressing machines on site. As with others in the area, the quarry suffered from a lack of water, resulting in the siting of the mill some distance away, at a lower level.

The Cwt y Bugail quarry is a former slate quarry located east of Blaenau Ffestiniog in Wales. It was first worked as a trial pit around 1840. Continuous production began in 1863 and continued until closure in 1961. The quarry was connected to the Ffestiniog Railway at Duffws Station via the Rhiwbach Tramway.