Quarry deepened to pit, finally to underground workings.

Very little survives due to bulk fill, clearing, and afforestation. The pit is flooded and adits are inaccessible. Some incline traces remain. A garage now occupies the original mill site.

Opened in the 1820s as a hillside operation and was later deepened into a pit with some underground workings. A steam mill was erected around 1850, originally equipped with 4 sand saws, though power sawing may predate the mill. The mill also processed blocks from Chwarel Fedwr. The original steam engine was replaced by a 30-foot water wheel, though steam was retained for pumping. In the 1890s, the mill was expanded to 9 saw tables and 3 planers, powered by a water turbine. In 1882, the quarry produced 1,865 tons of slate, mainly slab, with 74 men employed; production may have been higher in earlier years, making it the largest in the Dolwyddelan area. Output was initially carted to Trefriw, later to Dolwyddelan station. The quarry was likely one of the last users of sand saws. Operations closed in 1934.