This extensive pit working was located on the lower west slopes of Moel Tryfan, south of Rhosgadfan, and was part of a cottager-quarryman landscape. It began as a small site that expanded rapidly during the 1880s, following rail connection, with 81 men producing 1880 tons in 1882. By 1898 236 men were employed. Material was taken by tunnel to a substantial mills area where guillotine dressers are believed to have been used, unusual in this area. The quarry produced a variety of coloured slates. Finished product went down a long incline to the Bryngwyn drumhead (SH49765609). Water power was used though mill steam engines were installed as an auxiliary to water power. De Winton locomotives were used. A cableway and rail system was used here but was superseded in 1966 by Matador dumper- lorries, with their good off-road performance. Latterly, when workings broke into the adjacent Alexandra quarry (NPRN 400656) material from that quarry was reduced in the two Moel Tryfan mills. The quarry continued working on a small scale into the 1970s.
The site has since been much disturbed by bulkfill operations and the tunnel has gone. Extensive traces of the mills area survive along with the quarter mile-long incline.

Sources:
D.Gwyn, Welsh Slate: the Archaeology and History of an Industry (RCAHMW 2015), 18-19, 122, 130-1 & 170.
Ordnance Survey County Series 25-inch maps: sheet Caernarvonshire XXI.1, editions of 1899, 1900 & 1915.
A.J.Richards, A Gazeteer of the Welsh Slate Industry (1991), p.91.
RCAHMW air photos: AP1013; 945129/53-5; 945130/56-7 & 59.

David Leighton, RCAHMW, 19 February 2015