Coetmor Quarry

Overview

An early slate quarry on the east side of the Ogwen at Bethesda, on ground belonging to the old Coetmor estate, which was superseded by the Pantdreiniog Slate Quarry and absorbed into it during the 1860s. Very little is recorded of Coetmor as a working quarry in its own right. It survives in the landscape mostly as a name and as a tip: the standard gauge railway that reached Bethesda in 1884 was built on land reclaimed from it, and Coetmor Road, Coetmor New Road and the Coetmor housing of the mid twentieth century all took the name from the estate.

History

Slate was being got on both sides of the Ogwen valley long before Bethesda was a village. On the west side, the Penrhyn Slate Quarry grew into one of the largest in North Wales; on the east, a series of smaller workings included one on the Coetmor land. The Royal Commission's character study of Bethesda records simply that the Pantdreiniog Slate Quarry, which opened in 1850, superseded an older quarry known as Coetmor, and Wikipedia's account of Pantdreiniog has that quarry expanding during the 1860s and taking over the adjacent Coetmor Quarry. Both statements point the same way, and neither gives a date at which Coetmor itself began. The name is older than the quarry and belongs to an estate. One of the two ancient paths through the parish of Llanllechid, on which the earliest settlement at Bethesda was strung, ran from Coetmor to Gochwillan, and slates were once carried down that way in baskets on horseback, past Coetmor and on towards Aber Ogwen. In 1855 the Penrhyn estate bought the old Coetmor estate outright, tightening its hold on the ground around the independent core of the growing village. What happened to the quarry hole and its waste is better recorded than what came out of it. The Coetmor Road and Bryntirion character area of nineteenth-century terraces was built uphill of the High Street on the west side of the Pantdreiniog tip. When the London and North Western Railway branch from Bangor reached Bethesda in 1884, its terminus on the north side of the town was built on reclaimed quarry tip, and the station in turn drew new streets and a new chapel, Capel Bethania, to that end of the village. In the twentieth century a new road was driven from the post road to Coetmor and Hen Barc, giving access to the County School and to W. J. Parry's house at Coetmor Hall, and by the 1940s and 1950s the Coetmor and Maes Coetmor housing estates had been built on the land.

Geology

Coetmor lay on the east side of the Ogwen valley at Bethesda, in the Cambrian slate belt of Dyffryn Ogwen that also carries the Penrhyn quarry on the west side of the river. The slate here is the product of regional metamorphism, its cleavage running independently of the original bedding, which is what allows it to be split into roofing slates. No description specific to the Coetmor workings, of the veins worked or the quality of their product, was found in the sources read.

Geological setting: Slate and Regional Metamorphism (historical documentary reference)

Workings

Nothing has been established about how Coetmor was worked: whether by open pit like Pantdreiniog next to it or by terraced galleries like Penrhyn across the valley, how its slate was dressed, or how many men it employed. What is recorded is how the slate left the valley in the earliest period, carried in baskets on horseback along the old track through Pantdreiniog and past Coetmor towards Aber Ogwen, and that in the railway era the Bethesda transfer bank took in slate brought by cart from local quarries.

Closure

Coetmor did not close so much as disappear into its neighbour. Pantdreiniog, which had started around 1825 and was certainly working by 1845, expanded through the 1860s and took over the adjacent Coetmor Quarry; the Royal Commission's Bethesda study puts the same relationship the other way round, with Pantdreiniog superseding the older Coetmor. No closing date for Coetmor as a separate concern has been found, and no record of its output, workforce or ownership was located in the sources read.

What remains

The quarry is not a visible working site. Its tip was reclaimed for the railway terminus in 1884, and the land bearing the name now carries the Coetmor and Maes Coetmor housing estates, Coetmor Road and Coetmor New Road, a cemetery and chapel on Coetmor Road, and the Ogwen Sports Centre near Coetmor New Road. The large Pantdreiniog tip that overwhelmed the centre of Bethesda is the surviving industrial scar in this part of the town, and it belongs to the successor quarry rather than to Coetmor.

No surviving remains attributable to Coetmor specifically have been identified. The sources locate the quarry's ground and its tip, but everything they describe on the site today is either later development or belongs to the Pantdreiniog workings that absorbed it.

Redevelopment

Bethesda railway station, terminus of the 1884 London and North Western Railway branch from Bangor, was built on land reclaimed from quarry tip, and drew residential streets and Capel Bethania to the north end of the town. The Coetmor and Maes Coetmor housing estates followed in the 1940s and 1950s, reached by Coetmor New Road, which had been driven earlier in the century to serve the County School and Coetmor Hall.

Related mines

• Pantdreiniog Quarry — Pantdreiniog superseded Coetmor and absorbed the adjacent quarry into its own workings during the 1860s; the Royal Commission's Bethesda study and Wikipedia's account of Pantdreiniog both record the takeover, and the tip below the 1884 railway terminus is attributed to Coetmor by the former.

Nearby mines

• Pantdreiniog Quarry — 0.2 km SE
• Penrhyn Quarry — 1.2 km NE
• Cwm Eigiau Quarry — 6.1 km E
• Dinorwig Slate Quarry — 7.1 km SW
• Marchlyn Quarry — 7.6 km S

Straight-line distance, within 15 km. Show on the map.

Recorded claims

Individual factual claims, each attached to the source(s) that support it below. Where sources disagree, both are kept.

• The Royal Commission's Bethesda character study records that Pantdreiniog Slate Quarry, which opened in 1850, superseded an older quarry known as Coetmor. ¹
• Wikipedia's account of Pantdreiniog states that during the 1860s that quarry expanded and took over the adjacent Coetmor Quarry. ²
• The Royal Commission's study states that the standard gauge railway reached Bethesda in 1884 and that its terminus, on the north side of the town, was built on land reclaimed from the Coetmor Quarry tip. (disputed) ¹
• The Dyffryn Ogwen community history instead says the 1884 station was built on the rubble tips of the former Bird's Lodging slate quarry. (disputed) ³
• The Penrhyn estate bought the old Coetmor estate in 1855. One of the two ancient routes through the parish of Llanllechid ran from Coetmor to Gochwillan, and slates were carried along it by packhorse towards Aber Ogwen. ³

Photographs & further reading

Sources

1. (primary) Bethesda: an urban character study — Coflein, Royal Commission on the Ancient and Historical Monuments of Wales
2. (secondary) Pantdreiniog quarry — Wikipedia
3. (secondary) History of Bethesda — Dyffryn Ogwen Community Website

Record created: 9 September 2026 · Last researched: 10 September 2026