Minllyn Slate Quarry

Overview

A slate quarry on the western flank of Foel Dinas, a mile south of Dinas Mawddwy, working the easternmost of the three Ordovician slate veins of mid Wales. It opened before 1793 and worked intermittently until 1925, through a succession of companies that mostly ended in bankruptcy — the Minllen Slate and Slab Company in 1844, the Merioneth Slate and Slab Company in 1871, the Carlyle company in 1886 — and one landowner, Sir Edmund Buckley, who built a railway to serve it and went bankrupt himself in 1876. Its mill was the first integrated slate mill in the region.

History

Slate quarrying at Dinas Mawddwy dates back to at least 1793, and the first working at Minllyn was from open pits before 1840. In 1839 the Minllen Slate and Slab Company was formed to work the quarry; it went bankrupt in 1844. The quarry’s fortunes then followed a wealthy owner. In 1856 Sir Edmund Buckley, a prosperous mill owner from Ardwick, bought the Lordship of Dinas Mawddwy with an estate of 12,000 acres; his eldest son, also Edmund, took over in 1864 and spent lavishly. He bought Minllyn quarry and, to get the slate to market, built the Mawddwy Railway to connect with the Newtown and Machynlleth line at Cemmes Road. The quarry was reopened and re-equipped in 1872, and for a short period a workforce of over a hundred was employed. The companies came and went. William Bullock, mayor of Congleton, formed the Merioneth Slate and Slab Company in 1864 and leased the quarry; that company failed in 1871, and Bullock and a new partner, Robert Carlyle, formed the Carlyle Slate and Slab Company to take it over. Edmund Buckley declared bankruptcy in 1876 and most of his assets were sold, the part of the estate containing Minllyn going to the Carlyle company. Carlyle in turn was declared bankrupt in 1886. In 1889 William Bullock’s two sons formed the Minllyn Slate Company — though the quarry went on being called the Carlyle Quarry for many years afterwards. It operated until the First World War, when its warehouse at Dinas Mawddwy station was requisitioned for timber cutting. Work restarted around 1919 and the quarry closed for the last time in 1925.

Geology

Three parallel veins of Ordovician slate run through mid Wales, surfacing around Abergynolwyn in the west, around Corris in the middle, and at their easternmost in the district around Dinas Mawddwy. Corris was much the largest producer of the three; Minllyn worked the eastern end, on the western flank of Foel Dinas, and was a Narrow Vein quarry.

Workings

Open pits at first, with underground working following, and an incline half a mile long of 2 feet 2 inches gauge connecting the quarry to the Mawddwy Railway’s Dinas Mawddwy station. The mill mattered more than the size of the hole. A water-powered mill stood on the dressing floor alongside the open pit by 1845, and it was the first integrated mill in the region — three saws, three planers and slate dressing machines under one drive. The water wheel was later replaced by a pelton wheel with steam back-up.

Closure

Minllyn never found a company that could hold it. Bankruptcy took the Minllen company in 1844, the Merioneth company in 1871, its own landowner in 1876 and the Carlyle company in 1886; the First World War took its warehouse; and the collapse of the slate market after 1919 finished it in 1925.

What remains

Disused, with underground workings that remain accessible and are visited by mine explorers; an old underground winch survives in place. The site is on the western flank of Foel Dinas above the road south from Dinas Mawddwy.

The open pits, the dressing floor and mill site, the incline formation down to the former station, and underground chambers with fixed plant including a winch.

Related mines

• Hendreddu Quarry — Edward Davies, Edmund Buckley’s quarry supervisor, re-opened Minllyn in the 1860s and then oversaw the opening of Hendreddu near Aberangell, managing the new quarry from Minllyn — the same man and the same estate behind both.

Nearby mines

• Hendreddu Quarry — 4.0 km W
• Gartheiniog Quarry — 4.9 km W
• Maesygamfa Quarry — 5.1 km SW
• Cymerau Quarry — 7.4 km W
• Ratgoed Quarry — 7.7 km W

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.

• Minllyn quarry was a slate quarry near Dinas Mawddwy that opened before 1793 and continued working intermittently until 1925, located on the western flank of Foel Dinas. The first slate quarrying at Minllyn was from open pits before 1840. ¹
• The Minllen Slate and Slab Company, formed in 1839, went bankrupt in 1844; the Merioneth Slate and Slab Company, formed by William Bullock in 1864, failed in 1871; the Carlyle Slate and Slab Company that replaced it was declared bankrupt in 1886; and Edmund Buckley, who owned the quarry, declared bankruptcy in 1876. ¹
• Sir Edmund Buckley purchased the Lordship of Dinas Mawddwy in 1856 with a 12,000-acre estate; his son took over in 1864, purchased Minllyn quarry and built the Mawddwy Railway to connect to the Newtown and Machynlleth Railway at Cemmes Road. ¹
• A water-powered mill stood on the dressing floor alongside the open pit by 1845 and was the first integrated mill in the region, employing three saws, three planers and slate dressing machines; the water wheel was later replaced by a pelton wheel with steam back-up. ¹
• The quarry was connected to the Mawddwy Railway’s Dinas Mawddwy station by a half-mile incline of 2 ft 2 in gauge. ¹
• The quarry operated until the First World War, when its warehouse at Dinas Mawddwy station was requisitioned for timber cutting; work restarted around 1919 but it closed for the final time in 1925. ¹

Photographs & further reading

Sources

1. (secondary) Minllyn quarry — Wikipedia
2. (observational) Minllyn Slate Quarry — Subterranea Britannica

Record created: 8 September 2026 · Last researched: 8 September 2026