Moelwyn Quarry

Looking down the incline towards Llyn Stwlan, Ffestiniog Power Station’s upper reservoir


24 November 2012

Llyn Stwlan, Moelwynion

SH 66089 44279; 52.97906°N, 3.99593°W


Moelwyn Quarry, located on the eastern slopes of the Moelwyn mountains near Blaenau Ffestiniog, met with only limited success and closed around 1900. Exploration had started in the 1820s with a number of trial levels and the site was further developed in the 1860s when larger scale underground operations began. A slate processing mill, powered by waterwheel, was built at that time and its remains are visible below Stwlan Dam. The exit tramway descended the mountainside via a series of inclines to join the Ffestiniog Railway, the site of the actual junction now being submerged below the waters of Llyn Ystradau, Ffestiniog Power Station’s lower reservoir. Llyn Stwlan, the upper reservoir of this pumped-storage hydroelectric system built in the 1960s, now also covers part of the quarry complex.

Moelwyn Slate Mine (Royal Commission on the Ancient and Historical Monuments of Wales)

Outbye, top adit

Inbye, top adit. Looking towards the top of a large chamber.

A room with a view. Looking from the barracks down on Llyn Stwlan, much enlarged since the working days of the quarry.

Looking up the main incline towards the short tunnel at the top


4 thoughts on “Moelwyn Quarry

  1. Nice photos, Graham. You will be surprised to find that P and I have not explored this quarry, as we assumed it was gated . I like your inbye, top adit shot.

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