Ruins of Rhosydd quarry barracks and mills, near Tanygrisiau

Link to Welsh translation

This mountain pass, named Bwlch y Rhosydd, is like no other because it’s covered with relics of a large slate quarry. Slate from the underground Rhosydd quarry to the south was processed at the mills whose ruins you can see here today.

Many of the quarrymen lived in the barracks here, because the site was too remote for daily commuting from villages or towns. The quarry also had barracks in a lower, more sheltered spot. The quarrymen had their own chapel, now a lonely ruin in Cwmorthin.

Quarrying began at Rhosydd in the 1830s, initially on the surface. The routes of surface inclines are still visible. As most of the slate was deep inside Moel-yr-Hydd, the quarry was worked as underground levels from the 1850s. The chambers on each level were separated by thick pillars of rock which had to be left in place to hold up the roof.

Water to power the mills and underground transport was piped from the higher ground to the north. Ingenious mechanisms moved slate up or down inclines inside the mountain. Water balances were used to bring slate up to the mills from lower levels. This involved filling with water a tank on rails, which hauled up the laden wagons via a cable as it descended. The water was released at the bottom, and descending empty wagons returned the tank to the top. The discarded water flowed out of the mine through an exit tunnel.

Rhoysdd slates were taken by horse-drawn cart on the track through Cwmorthin until 1864, when a narrow-gauge tramway was built westwards from the mills to a long incline, which connected into the Croesor Tramway to Porthmadog.

Many accidents happened at the quarry. In 1906 Owen Thomas of Tanygrisiau, an experienced quarryman, was killed by a fall of rock. He left a wife and three children. His father was accidentally killed at Cwmorthin quarry 10 years earlier.

The quarry struggled to survive in the 20th century. In autumn 1914 it was temporarily closed and many of the workers moved to South Wales collieries. The quarry ceased to operate in 1930.

Sources include ‘Gazeteer of Slate Quarrying in Wales’ by Alun John Richards, Llygad Gwalch 2007

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