The northern working at Llyn y Gader contains several open faces. A two-way incline leads to a mill that was constructed on top of an earlier building. Two wheel pits, likely used for pumping and haulage as well as mill drive, were fed by a large leat embankment that brought water to power the operations.

The southern working at Gader Wyllt comprises an open working with a small mill. An adjacent rubbish run retains Hudson track still in place. A short incline descends to a lower level where a large, uncompleted mill stands. Above this area, a tramway route leads to a tentative underground working accompanied by ruined dressing sheds, other structures, and an office. A further trial working lies about 200 yards to the east.

Both had early open excavations that were drained by a rubbish run leading to the lake. This run is overlain by an unfinished exit causeway that was intended to carry a tramway. A forge sits partway along this causeway. At the northern end of the site stand the bridge pillars for the railway branch that was never built

The site consisted of two adjacent workings known as Llyn y Gader to the north and Gader Wyllt to the south. Various owners worked the quarries from the late 18th century onwards, including a brief and unsuccessful ownership attempt by the North Wales Quarrymen’s Union. After the opening of the North Wales Narrow Gauge Railway, slate could be loaded at Rhyd Ddu, though a tramway to the road may never have been completed. A branch from the railway was planned but never built. The workings closed in 1928.