Hendreddu quarry
United Kingdom
Hendreddu quarry was a slate quarry about three miles west of Aberangell in Merioneth (now Gwynedd), North Wales, near Nant Hendreddu on the slopes of Mynydd Hendre-ddu. The quarry worked the Narrow Vein, the highest-quality slate vein in the Abercorris Group. For the majority of the quarry's existence, the Hendre Ddu Tramway was owned by the same company that owned the quarry, and the two were run as a single enterprise.
Data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).