Graig Colliery, Pentrebach

Overview

Pwll y Graig, two elliptical shafts on the hillside above Pentrebach in the Plymouth ironworks' take, sunk about 1810-20. An 1846 explosion killed seven there; after years of flooding it was reopened by Hill's Plymouth in 1903 and employed up to 800 men before being folded into South Duffryn.

History

Graig Colliery, called Pwll y Graig in its early days, stood on the mountainside behind Duffryn Fawr at Pentrebach, south of Merthyr Tydfil, and worked steam coal in the Plymouth ironworks' take. Welsh Coal Mines has its No.1 or Wern Las pit, the upcast, sunk about 1810 (after 1820 by other accounts) and the No.2 downcast pit about 1820, both elliptical, one raising coal and the other pumping. The Northern Mine Research Society records a Graig in 1837 with a 60-yard shaft and 50 men under W. and R. Thomas, and a Graig working steam coal in 1843, first for the Plymouth Iron Company and then for Hill's Plymouth Company; Lucy Thomas and her son William took a lease of the coal under Graig Farm in 1837, and the sources do not settle whether their pit was this one. On 6 May 1846 an explosion of gas killed seven men and boys, the youngest aged ten and twelve. Robert Rees was manager in 1860-70 and, with others, owner in 1869, and from 1871 it was part of the Plymouth Iron Company's operation. Unlisted between 1883 and 1903 and believed to have flooded, it was reopened in 1903 by Hill's Plymouth Company, working the Nine Feet and Lower Four Feet seams among others, and employed 800 men in 1919-20. Later owned by Llewellyn (Plymouth) Limited, it passed in 1937 to Powell Duffryn Associated Collieries and was worked with South Duffryn Colliery; production may have stopped in 1940, but it was kept on maintenance until at least 1953, and at nationalisation in 1947 it was part of South Duffryn.

Geology

Steam coal seams of the South Wales coalfield: the Red, Five Feet Six, Lower Two Feet Nine, Lower Four Feet, Upper Four Feet and Nine Feet.

Geological setting: Sedimentary Beds and Seams (well documented example)

Workings

Two elliptical shafts: No.1 (Wern Las, upcast) and No.2 (downcast), one winding coal and the other pumping. NMRS has No.1 working the Lower Four Feet at 142 yards and No.2 the Nine Feet at 128 yards; WCM gives the Lower Four Feet, the lowest workable seam, at 186 yards.

Closure

Welsh Coal Mines says it may have closed in 1940 but was retained on maintenance until at least 1953; the Northern Mine Research Society has it part of South Duffryn Colliery by nationalisation in 1947. It had also stood unlisted, and probably flooded, from 1883 to 1903.

What remains

Unknown.

Unknown.

Related mines

• Perthyglisson Colliery — Both worked by the Plymouth Iron Works Company for the Plymouth ironworks at Merthyr.
• Rhydycar Colliery — Both worked by the Plymouth Iron Works Company for the Plymouth ironworks at Merthyr.

Nearby mines

• Ffos-y-Fran — 0.3 km NW
• Gethin Colliery — 1.6 km SW
• Ynysfach Colliery — 2.7 km NW
• Perthyglisson Colliery — 2.8 km S
• Rhydycar Colliery — 3.0 km NW

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

People

• Henry John · manager, 1908 — Manager in 1908, when the pit employed 383 men.
• Robert Rees · manager, 1865–1870 — Manager in 1865-70 (NMRS); owner 'and others' in 1869 (WCM).

What's uncertain

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

• A Graig was recorded in 1837 with a 60-yard shaft and 50 men under W. and R. Thomas; in 1843 a Graig was working steam coal for the Plymouth Iron Company and then Hill's Plymouth Company. (uncertain) ²
• The Lower Four Feet, the lowest workable seam, lay at 186 yards. (disputed) ¹
• The No.1 Pit worked the Lower Four Feet seam at 142 yards and the No.2 the Nine Feet at 128 yards. (disputed) ²

Recorded claims

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

• Graig No.1 (Wern Las, upcast) was sunk about 1810, other sources say after 1820, and No.2 (downcast) about 1820, on the mountainside behind Duffryn Fawr at Pentrebach; it was called Pwll y Graig in the early days. ¹
• A Graig was recorded in 1837 with a 60-yard shaft and 50 men under W. and R. Thomas; in 1843 a Graig was working steam coal for the Plymouth Iron Company and then Hill's Plymouth Company. (uncertain) ²
• On 6 May 1846 an explosion of gas killed seven: William Lewis, John Davies (50), David Lovett (35), William Thomas (30), Evan Williams (10), Edward Jones (12) and Daniel Lewis (25). ¹
• Not listed between 1883 and 1903 and believed flooded, Graig was reopened in 1903 by Hill's Plymouth Co. Ltd, which employed 383 men in 1908, 488 in 1918 and 597 in 1923. ^1,2
• The Lower Four Feet, the lowest workable seam, lay at 186 yards. (disputed) ¹
• The No.1 Pit worked the Lower Four Feet seam at 142 yards and the No.2 the Nine Feet at 128 yards. (disputed) ²
• Owned by Llewellyn (Plymouth) Ltd, which employed 620 there in 1934, it passed to Powell Duffryn Associated Collieries in 1937 and was worked with South Duffryn; it may have closed in 1940 and was part of South Duffryn at nationalisation. ^1,2

Photographs & further reading

Sources

1. (secondary) Graig Colliery Merthyr, Taibach colliery, Dan y Deri colliery — Welsh Coal Mines
2. (secondary) Graig Colliery — Northern Mine Research Society
3. (primary) Plymouth Graig, Taibach, North Duffryn, South Duffryn (Mining Remediation Authority abandonment plan, via BGS catalogue item 21843368) — British Geological Survey / Mining Remediation Authority
4. (secondary) Lucy Thomas Colliery — Northern Mine Research Society

Record created: 19 September 2026 · Last researched: 19 September 2026