Groesfaen Colliery

History

The sinking of Groesfaen's 20-foot diameter shaft began in 1902 and was completed in 1906, at a depth of 2,159 feet -- 720 yards -- and a cost of 183,723 pounds, by the Rhymney Iron Company; its sister pit, Pengarreg, was sunk alongside it. A Walker ventilating fan 25 feet in diameter and 8 feet wide was installed in 1906. By 1908 the colliery employed 173 men underground and 99 on the surface under the manager William Thomas, producing steam coals from the Middle and Lower Coal Measures and served by the Rhymney Railway.

The workforce grew quickly: 674 in 1910, 1,204 in 1912, 1,248 in 1915-16 and 1,149 in 1918. A list of 1923 gives 1,061 men working the Rhas Las, Red, Big and Clay seams. In 1925 the Rhymney Iron Company was bought by the Powell Duffryn Steam Coal Company, which held the colliery until nationalisation. D. Williams was manager in 1927 and 1935, when 1,080 men worked underground and 200 on the surface; E. Morgan followed in 1938, with 694 underground in the Seven-Feet, Red and Upper Four-Feet seams, and I. G. Thomas was manager from the early 1940s into 1949. On the Sunday night shift of 30 July 1939, lightning knocked out all the power to the colliery and left the men underground for six hours. The pit had its own coal washery.

On nationalisation in 1947 Groesfaen went into the National Coal Board's South Western Division, No. 5 Area, Group No. 2, with 734 men underground and 200 on the surface in the Seven-Feet, Red Vein and Upper Four-Feet. The Yard seam was added by 1954, when manpower reached 1,067 under K. Butcher, and in 1954-55 Groesfaen was one of 42 collieries whose accident rate concerned both the Board and the National Union of Mineworkers. Of 1,029 men in 1955, 566 worked at the coalfaces; that figure fell steadily through the late 1950s to 467 in 1958 and 363 of 841 men in 1961, when the pit's Y1 face was used to train forty men or boys at a time. In May 1967, 720 men were employed, 535 of them underground in the Rhas Las, Six-Feet, Red, Seven-Feet and Lower Four-Feet seams, and a new ploughed face in the Lower Four-Feet raised output from 15.2 to 23.4 hundredweight per manshift. It was not enough.

Geology

Steam coals of the Middle and Lower Coal Measures, worked in the Rhas Las, Red, Big, Clay, Six-Feet, Seven-Feet, Nine-Feet, Yard, Four-Feet and Five-Feet/Gellideg seams; the Northern Mine Research Society records their sections, the Upper Six-Feet at 1,703 feet and the Five-Feet/Gellideg at 2,035 feet, as thin coals split by bands of dirt.

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

Workings

A 20-foot diameter shaft 2,159 feet deep, ventilated from 1906 by a Walker fan 25 feet across and 8 feet wide, with the sister Pengarreg pit alongside, a coal preparation plant of its own and rail connection to the Rhymney Railway. Power loading came late: the L7 face opened in 1967 in the Lower Four-Feet, 620 yards down and 530 feet long in a 44-inch section with clay roof and floor, worked by plough.

Closure

The National Coal Board closed Groesfaen on 22 November 1968 as uneconomic, despite the productivity gained from the new ploughed face in the Lower Four-Feet. Its power-loading equipment went to Cwmtillery Colliery and 350 of its men transferred to Ogilvie, Britannia, Bargoed, Markham, Bedwas, Deep Navigation and Trelewis Drift; eighty took early retirement and sixty were kept on.

Related mines

• Bargoed Colliery — Neighbouring Rhymney valley pits: both were worked by Powell Duffryn from 1925, and 350 of Groesfaen's men were transferred to Bargoed and six other collieries when Groesfaen closed in 1968.
• Cwmtillery Colliery — Groesfaen's power-loading equipment was transferred to Cwmtillery Colliery on its closure in 1968.

Disasters & major incidents

• Groesfaen Colliery roof fall, 1915
  19 April 1915 · Collapse / Roof Fall · 2 fatalities
  On Monday 19 April 1915 a stone fell from the roof at the Groesfaen Colliery, Deri, as two rippers worked under a staging after an earlier fall. Henry Roberts was killed instantly and David Cotterell was badly hurt; he died later in Rhymney Hospital.

Recorded claims

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

• The 20-foot diameter shaft was begun in 1902 and completed in 1906 at a depth of 2,159 feet and a cost of 183,723 pounds, sunk by the Rhymney Iron Company alongside its sister pit Pengarreg. ^1,2
• By 1908 the colliery employed 173 men underground and 99 on the surface under the manager William Thomas, and a list of 1923 gives 1,061 men working the Rhas Las, Red, Big and Clay seams. ^1,2
• The Rhymney Iron Company was bought by the Powell Duffryn Steam Coal Company in 1925, which held Groesfaen until nationalisation in 1947. ^1,2
• On the Sunday night shift of 30 July 1939, lightning knocked out all the power to the colliery and the men were left underground for six hours. ^1,2
• In 1954-55 Groesfaen was one of 42 collieries whose level of accidents concerned both the National Coal Board and the National Union of Mineworkers. ^1,2
• The National Coal Board closed Groesfaen on 22 November 1968 as uneconomic; its power-loading equipment went to Cwmtillery and 350 men were transferred to seven other collieries. ^1,2

Photographs & further reading

Sources

1. (secondary) Groesfaen Colliery, near Bargoed — Welsh Coal Mines
2. (secondary) Groesfaen Colliery 1902-1968 — Northern Mine Research Society (Internet Archive)

Record created: 20 September 2026 · Last researched: 20 September 2026