Chwarel Ddu quarry

Chwarel Ddu quarry was the earliest slate quarry in the Lledr Valley. It was working before 1810, and continued in sporadic operation until the late 1920s. It is about 0.5 miles west of Dolwyddelan, just beneath Dolwyddelan Castle.

The quarry is believed to have opened between 1800 and 1805. In 1810, the quarry was successful enough that the Gwydir Estate, who owned the land on which the quarry sat, constructed a cart road from the quarry to the Holyhead Road at Conwy. This now forms part of the A470. Despite this early success, the quarry only operated for short periods over the next few decade. For several years in the late 1850s, it produced significant amounts of slate, up to 700 tones per year. At this time a stationary steam engine was used to haul rock up from the open pit. By 1888 it was once more closed.

Wikipedia