Drum Slate Quarry (nprn 305779) was worked from the 1860s but had been abandoned by the time of the 1891 OS map. The mill stands at the foot of an inclined plane (nprn 537043), facing a track to Gamallt lead mines (nprn 537495). It is a large roofless building of drystone rubble, 20m long SW-NE x 4.5m wide, the gable end walls standing up to 2.5m high. The NW wall faces a track and has 3 lintelled windows, and there were probably also 3 windows to the SE side. The entrance is in the SW end wall and is 2m wide. Outside the NE wall is the wheelpit, which is at least 10m long, 1.7m wide and 4m deep.
Recorded as part of RCAHMW Uplands Initiative Project, W B Horton, H & H, 07/01/2014.