Bwlch-y-Groes is a small open quarry which operated in the 18th century and was revived during 1870s. Taken over by Cefn-du in 1886. Product carried by tramway to the head of the Ffridd incline. The site remains consist of a surprisingly large pit with rubbish runs, a very degraded tramway formation and ruins of a barrack building to the west.

Richards, A. 1999. The Slate Regions of North and Mid Wales. Gwasg Carreg Gwalch
RCAHMW AP945131/51
RCAHMW, 2009