Moelwyn Quarry

Overview

A financially troubled slate quarry south of Tanygrisiau, prospected from the 1820s and formally worked from 1860 to 1897, notable for an early water turbine, a spectacular seven-incline transport system, and literacy classes for its workforce said to have been visited by the Prime Minister of the day.

History

The Rothschild-backed Royal Cambrian Company carried out exploratory prospecting on the eastern slopes of Moelwyn Bach between 1826 and 1828, and the Ruthin lawyer Humphrey Jones opened workings on the southern slopes in 1841, but it was not until 1860 that the Great Moelwyn Slate Company Ltd formally purchased the site, for £9,890, and began excavating underground chambers in earnest. The company was reconstituted in 1865 with £50,000 of working capital, and ownership changed hands repeatedly over the following decades -- Pemberton, Flavell and Allison of Birmingham, who bought the lease for £17,000 in 1871 and sold it in 1873 to the Union Slate Co. Ltd, liquidated in 1875, and finally J. Solomon Jones's Moelwyn Slate Company from 1891 until closure in 1897. The quarry was hampered throughout by a poor natural water supply, which the mill (built between the fourth and fifth of seven inclines) addressed by drawing water from Llyn Stwlan, a reservoir higher up the mountain; a 40-by-4-foot waterwheel and, from 1864, a water turbine -- one of the first two installed at any slate quarry anywhere, alongside the same year's installation at the neighbouring Ratgoed quarry -- powered six sawing tables and seven dressing machines in the mill. A spectacular series of seven inclines descended around 1,100 feet from the workings to connect with the Ffestiniog Railway. Unusually, the barracks built for the workforce were occupied not by single lodging quarrymen but by whole families living permanently on the mountain, and even in this remote setting the quarry ran basic literacy classes for its workers in the 1860s, visited by the Prime Minister of the day, Lord Palmerston. Despite the technological investment, the quarry never achieved lasting commercial success and operated only sporadically before closing for good in 1897.

Geology

Slate on the eastern slopes of Moelwyn Bach, the same vein as the neighbouring Fron Boeth and Pant Mawr workings.

Workings

Underground chambers worked via a mill (sited between the fourth and fifth of seven descending inclines) housing six sawing tables and seven dressing machines, powered first by a 40-by-4-foot waterwheel and, from 1864, by one of the earliest water turbines installed at any slate quarry, fed by the Llyn Stwlan reservoir; finished slate descended the seven inclines to the Ffestiniog Railway.

Closure

Closed in 1897 after operating only sporadically through a long series of ownership changes, never achieving lasting financial success despite its early adoption of water-turbine power.

What remains

The quarry and its inclines remain largely intact, though Llyn Stwlan -- extended in 1960 to become the upper reservoir of the Ffestiniog Power Station pumped-storage hydroelectric scheme -- sits just below the quarry and has obliterated the sixth incline, parts of the seventh, and much of the mill area; the Ffestiniog Railway's own deviation around Llyn Ystradau has also destroyed the lower section of the first incline. Several adits remain accessible on the mountainside but have been fitted with metal grilles to prevent entry.

Largely intact inclines and quarry workings, though partly lost to the 1960 extension of Llyn Stwlan reservoir and the Ffestiniog Railway's deviation around Llyn Ystradau; several grilled adits survive on the mountainside.

Related mines

• Fron-Boeth and Pant Mawr Quarry — The two quarries worked the same slate vein, with underground pillars deliberately aligned between them to preserve structural integrity.

What's uncertain

Points where sources disagree or the record could not be settled; both accounts are kept. All open questions in the archive.

• The quarry ran basic literacy classes for its workforce in the 1860s, which were, on one account, visited by the sitting Prime Minister, Lord Palmerston. (uncertain) ¹

Recorded claims

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

• Moelwyn was one of the first two slate quarries known to have used a water turbine, installed in 1864, the same year the neighbouring Ratgoed quarry adopted the same technology; turbines remained uncommon at other quarries until electrical generation made them standard around the turn of the century. ¹
• The quarry ran basic literacy classes for its workforce in the 1860s, which were, on one account, visited by the sitting Prime Minister, Lord Palmerston. (uncertain) ¹
• Ownership passed through the Great Moelwyn Slate Company Ltd (from 1860), Pemberton/Flavell/Allison and the Union Slate Co. Ltd (1871-1875), and finally J. Solomon Jones's Moelwyn Slate Company (1891-1897), before the quarry closed for good in 1897 having never achieved lasting financial success. ¹
• Llyn Stwlan, extended in 1960 as the upper reservoir of the Ffestiniog Power Station pumped-storage scheme, has obliterated the sixth incline, parts of the seventh, and much of the mill area; the Ffestiniog Railway's own deviation around Llyn Ystradau destroyed the lower section of the first incline. Surviving adits have been fitted with metal grilles. ¹
• The quarry's inclines joined the Festiniog Railway by a left-hand junction at Tunnel Cottage above Moelwyn Halt; Llyn Stwlan drowned the part of the system where a number of small inclines met the main pitch, and the surviving inclines are fairly well preserved. ²
• Pemberton, Flavell and Allison, all of Birmingham, bought the lease in 1871 for £17,000 and sold it on to the Union Slate Co. Ltd in 1873, which was liquidated in 1875. ¹

Photographs & further reading

Sources

1. (secondary) Moelwyn quarry — Wikipedia
2. (secondary) Moelwyn Quarry Incline (Festipedia, Ffestiniog Railway Society) — Festipedia
3. (secondary) Ratgoed quarry — Wikipedia

Record created: 30 August 2026 · Last researched: 24 September 2026