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. An explosion of gas on 6 May 1846 killed seven (see Disasters, below). 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.

Related mines

• Clynmill Colliery — Both Hill's Plymouth pits; in 1921 Clynmill's remaining reserves were allocated to Graig Colliery.
• 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.
• South Duffryn Colliery — Both Plymouth-Ironworks collieries at Pentrebach.
• Waunwyllt Level — When the Waunwyllt tenancy ended in the mid 1830s the Thomases moved a mile south to the Graig, signing a lease in 1837 to work the same Four Foot seam; the Graig Coal Company that William Thomas formed there is also recorded as Waunwyllt's owner in 1869.
• Wernlas Colliery — Coflein records Wernlas Level at the Graig pits; both later Hill's Plymouth Company's.

Disasters & major incidents

• Graig Colliery explosion, 1846
  6 May 1846 · Explosion · 7 fatalities

  On Wednesday 6 May 1846 fire damp exploded in the Pwll y Graig pit of the Plymouth Iron Company, Pentrebach, near Merthyr, severely burning seven men and boys. All seven died.

  The Monmouthshire Merlin named the burned as David Lovett, 35, married with five children, one of them blind; William Thomas, 30, whose child had lately drowned in the Plymouth watercourse; the boys Evan Williams, 10, and Edward Jones, 12; John Evans, 23; Daniel Lewis, 25; and William Lewis. Evan Williams died on the Thursday, Lovett and Thomas on the Friday and Daniel Lewis on the Sunday, and the others were not expected to live.

• Graig Colliery explosion, 1925
  19 January 1925 · Explosion · 2 fatalities

  Gas fired during shotfiring at Graig Colliery, Abercanaid, on 19 January 1925 killed a collier and his seventeen-year-old assistant and burned the fireman.

  On 19 January 1925 gas was ignited during shotfiring at Graig Colliery, near Abercanaid. The collier Thomas Vaughn Williams and his assistant, Stanley Jenkins, 17, were killed, and the fireman was burned.

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
• 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