Prince of Wales Quarry, Cwm Trwsgl

Spoil heaps of the Prince of Wales Quarry (background, right of centre) with the eastern end of the Nantlle Ridge behind (Trum y Ddysgl and Mynydd Drws y Coed)


24 April 2011

Cwm Trwsgl, Cwm Pennant

SH 54525 49277; 53.02095°N, 4.17028°W Slab mill
SH 54814 49486; 53.02290°N, 4.16606°W Reservoir dam
SH 54703 49472; 53.02274°N, 4.16771°W Mill incline drum house
SH 55027 49872; 53.02642°N, 4.16306°W Level 3 adit
SH 54916 49996; 53.02750°N, 4.16478°W Level 5 (top level) barracks
SH 55106 50103; 53.02852°N, 4.16200°W Level 5 (top level) adit


The Prince of Wales Quarry nestles in Cwm Trwsgl, at the head of Cwm Pennant, with the peaks of the Nantlle ridge dominating the view to the north and west. Approaching along the tramway from the south, a long incline can be seen rising up the centre of the waste tips of the quarry’s five levels. The worked areas are to the right of the spoil heaps, on the western face of Y Gyrn.

A dammed reservoir to the right of the tramway provided the power source for the slab-processing mill, some 37 m lower down the hill and 350 m distant. There are various open quarry faces and pits, shafts and adits to be seen. Numerous ruined buildings are in evidence. Of particular note is the slab mill and, on the top (fifth) level, a row of barracks with a row of waliau opposite. The barracks provided accommodation for the quarrymen, and the waliau were small, open-fronted, sloping-roofed shelters where slate-splitting work was carried out.

In addition to the mill on site, the grand Pont y Pandy mill was also purchased to process slate from the quarry, although it might not ever have been used for this.

The quarry was served by the ‘Gorseddau Junction and Portmadoc Railways’. The 2 ft gauge line was built in 1872 and replaced and extended the previous 3 ft gauge Gorseddau Tramway, which had been built for the failed Gorseddau Quarry. Pert, a vertical-boilered steam engine, ran on the line, although most of its traffic was horse drawn and, near the end of its life, it saw single wagons being hand propelled down to Porthmadog. The line had fallen into disuse by 1887 and had been dismantled by the time the land it ran on was sold in 1897

The quarry itself was a dismal failure. It opened in 1873 and closed in 1886, with production in the intervening years never having amounted to very much.

Prince of Wales Quarry (; The Prince of Wales Quarry (Treasure Maps);
The Gorseddau Junction & Portmadoc Railways (Welsh Highland Railway Society)

Slab mill and launder pillars

Dam wall

Twin-walled dam (the cavity would have been filled with clay)

Reservoir. Water from here powered the mill below. The row of stone pillars by the mill supported the launders feeding the water wheel.

Ruined drum house at the top of the mill incline. The main quarry incline can be seen in the distance.

Main incline up the middle of the waste heaps

Quarrymen's barracks (left) and waliau (right). Waliau are open-fronted shelters where slate splitting was carried out.

Grating covering a shaft on the top level

Entrance to short adit from chamber at rear

Chamber at end of short adit, ending in open shaft (level 3)

Entrance to blind adit on top (fifth) level. This adit is around 30 paces long.


2 thoughts on “Prince of Wales Quarry, Cwm Trwsgl

  1. Pingback: Dereliction « GeoTopoi

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