Graig Ddu Quarry

Overview

A remote, high-altitude slate quarry above Blaenau Ffestiniog — reputedly the highest industrial site in Britain — worked from around 1800 and famous among Welsh slate quarries for the ceir gwyllt, home-built 'wild cars' that let quarrymen ride the mile-long inclines down at the end of a shift, a practice that also caused a string of fatal accidents before it was finally stopped in 1939. Still worked today by Welsh Slate.

History

Quarrying began around 1800 on this exposed, over-600m-high site above Blaenau Ffestiniog under the name Manod Quarry, but the workings only really developed once they were absorbed into the neighbouring Graig Ddu concern in the 1840s. The site's remoteness was a persistent handicap: slate was at first floated down the River Dwyryd, until around 1865-67 when three cable-worked inclines, on a shallow gradient of about 1 in 6, were built down to the road at Tan y Manod. The New Craig Ddu Slate Company Ltd, formed in 1864-65, consolidated the operation, and once the Festiniog and Blaenau Railway opened in 1868 a fourth incline was added, connecting in late 1869 to give the quarry a proper rail outlet for the first time. Ownership passed to the Craigddu Slate Company from 1880. Despite its difficult location, the quarry grew into a substantial operation with around 36 saw tables and the same number of dressing machines on site, output reaching over 6,000 tons a year around the turn of the century (against 3,140 tons in 1882) and employment peaking at 110 men in 1882. It was also a genuine technical pioneer, among the first Welsh slate quarries to adopt compressed-air drills and winches, powered by steam-driven compressors, in operation by 1902; underground working began in the 1920s, a gas engine was installed in 1925, and a small hydro-electric plant was later built partway down one of the inclines. Graig Ddu's most distinctive feature, though, was the ceir gwyllt — 'wild cars' — invented by the company's own blacksmith in the 1870s: simple wheeled devices, likened to a skateboard sitting on a single rail with a double-flanged wheel at the front, that let quarrymen ride the shallow-graded inclines down to the road at the end of a shift rather than walk. The practice was, by contemporary accounts, unique to Graig Ddu among all the Blaenau Ffestiniog quarries, and it came at a real cost: fatal accidents are recorded in 1897, 1898 and again in the 1920s, yet the practice continued regardless until 1939, when the quarry itself closed at the outbreak of the Second World War. It reopened briefly after the war to supply slate for bomb-damage repairs before closing again in 1946, by which time 86 men were still employed. Graig Ddu did not stay closed for good. From the mid-1980s the site was worked by the Alfred McAlpine group in an untopping operation — quarrying down from the surface into former underground workings — in conjunction with the neighbouring Bwlch y Slaters quarry, and the site remains in production today under Welsh Slate, part of the Breedon Group, targeting around 15,000 tonnes of finished slate a year and supporting around 40 jobs; planning permission has since been extended to run to 2048.

Geology

Graig Ddu works the same belt of high-quality Ordovician slate that runs through the Blaenau Ffestiniog district, quarried here at unusually high altitude on the flank of Manod Mawr rather than in the valley workings more typical of the area — one of very few genuinely open-cast slate sites in the district, later supplemented by underground working once the accessible surface rock was exhausted.

Workings

Originally worked as an open quarry — one of the few true opencast slate sites in the Blaenau Ffestiniog area — with underground working added from the 1920s; later 20th-century operations under Alfred McAlpine reworked much of the site by untopping, quarrying down from the surface through former underground galleries.

Closure

The original quarry closed in 1939, reopened briefly after the war for bomb-damage repair slate, and closed again in 1946; the site was later reopened for untopping operations from the mid-1980s and remains in production today.

What remains

Graig Ddu remains an active quarry, operated by Welsh Slate (part of the Breedon Group) and described as the highest industrial site in Britain, currently producing standard-sized roofing slates to British Standard thicknesses; planning permission has been extended to run until 2048.

As a still-working quarry, the site retains its historic incline routes down to Tan y Manod alongside active modern quarrying areas; waste tips from the historic workings are visible on the north summit of Manod Mawr.

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.

Graig Ddu is an active working quarry — this entry describes history and general location only, 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.

• Opened around 1800 as Manod Quarry, redeveloped as Graig Ddu from the 1840s; three cable-worked inclines to Tan y Manod were built around 1865-67, and a fourth incline connected the quarry to the Festiniog and Blaenau Railway in late 1869. ^1,2
• The quarry held around 36 saw tables and dressing machines, employed 110 men at its 1882 peak, produced over 6,000 tons of slate a year around 1900, and was among the first Welsh slate quarries to adopt compressed-air drills and winches, in use by 1902. ¹
• Invented by the company blacksmith in the 1870s and, by contemporary account, unique to Graig Ddu among the Blaenau Ffestiniog quarries, these wheeled devices let quarrymen ride the inclines down at shift's end; fatal accidents are recorded in 1897, 1898 and the 1920s, and the practice continued until the quarry's 1939 closure. ^1,2
• The quarry closed in 1939, briefly reopened after the war for bomb-damage repair slate, closed again in 1946, and was reopened for untopping operations by Alfred McAlpine from the mid-1980s; it remains in production today under Welsh Slate (Breedon Group). ¹

Images

Sources

1. (secondary) Graig Ddu quarry — Wikipedia
2. (secondary) Graig Ddu Quarry — Festipedia (Ffestiniog Railway heritage wiki)

Record created: 26 August 2026 · Last researched: 26 August 2026