Coedmadoc Quarry

Overview

A Nantlle Valley slate quarry, worked by the Coedmadoc Slate Company, which acquired one of Croesor quarry's own De Winton steam locomotives secondhand in the 1870s -- one of at least 37 quarries that made the Nantlle Valley a major, if independently and small-scale-run, centre of the Welsh slate industry.

History

Coedmadoc Quarry was worked by the Coedmadoc Slate Company of Nantlle, which acquired one of two 0-4-0 vertical-boilered tank locomotives, built by De Winton of Caernarfon, that had originally worked at the neighbouring Croesor quarry in the 1870s. Unlike the large integrated enterprises run at Bethesda, Llanberis and Blaenau Ffestiniog, the Nantlle Valley's slate quarries -- Coedmadoc among them -- were characteristically run independently and on a much smaller scale, though the valley as a whole, with at least 37 operating quarries at one time, was still a world-leading slate producer during the 19th century. Slate from the valley's quarries, including Coedmadoc, was carried by the Nantlle Railway, opened in 1828, down to the port of Caernarfon.

Workings

Slate haulage used a secondhand De Winton 0-4-0 vertical-boilered locomotive, acquired from the neighbouring Croesor quarry in the 1870s, alongside the quarry's own connection to the Nantlle Railway.

Abandoned workings can be dangerous — unstable ground, uncapped shafts, flooding and bad air are common even where a site looks safe from the surface. This entry describes history and general location only; it is not an access guide.

Recorded claims

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

• The Coedmadoc Slate Company of Nantlle acquired one of two 0-4-0 vertical-boilered tank locomotives, built by De Winton of Caernarfon, that had originally worked at the neighbouring Croesor quarry in the 1870s. ¹
• Unlike the large integrated enterprises at Bethesda, Llanberis and Blaenau Ffestiniog, the Nantlle Valley's slate quarries -- Coedmadoc among them -- were run independently and on a much smaller scale, though the valley as a whole, with at least 37 operating quarries at one time, was still a world-leading slate producer in the 19th century. ²

Photographs & further reading

This page doesn't try to reproduce everything — these are the best original sources found for this mine.

Sources

1. (secondary) Croesor quarry — Wikipedia
2. (secondary) Slate industry in the Nantlle Valley — Wikipedia

Record created: 30 August 2026 · Last researched: 31 August 2026