Gellideg Colliery

Overview

The No.2 level of a small Merthyr Tydfil mine that fed the Cyfarthfa Iron Works, working the seam that gave the colliery its name until its abandonment in March 1924.

History

No record of a No.1 working has been found, but Gellideg Colliery's No.2 level was worked to feed the Cyfarthfa Iron Works, and was abandoned in March 1924 along with several other small Cyfarthfa-feeder levels in the district. It took its name from the Gellideg seam, the lowest of three closely spaced coals in the Merthyr district that together made up what was formerly known as the Lower Four-Feet seam; the British Geological Survey's own district memoir records the Gellideg as 0.6 to 0.91 metres thick in the Taff Valley around Merthyr, thinning further west and splitting apart from the overlying Five-Feet seam by as much as 21 metres at Blaennant and Bwllfa.

Nearby mines

• Cornel Wain Colliery — 0.4 km SW
• Rhydycar Colliery — 0.7 km SW
• Albert Colliery — 0.8 km NE
• Robbins Colliery — 0.9 km SW
• Ynysfach Colliery — 1.0 km S

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.

• The No.2 level was worked to feed the Cyfarthfa Iron Works and was abandoned in March 1924; no record of a No.1 working has been found. ¹
• The British Geological Survey's district memoir independently describes the Gellideg seam that gave the colliery its name as the lowest of three closely spaced coals in the Taff Valley around Merthyr, 0.6 to 0.91 metres thick locally, forming what was formerly known as the Lower Four-Feet seam, and splitting away from the overlying Five-Feet seam by as much as 21 metres further west at Blaennant and Bwllfa. ²
• The colliery's No.2 level was abandoned in March 1924, the same closure date recorded for several other small Cyfarthfa-feeder levels in the same NMRS survey, consistent with a district-wide end to this phase of Cyfarthfa's own ironstone and coal working. ¹

Photographs & further reading

Sources

1. (secondary) Small Collieries around Merthyr Tydfil — Northern Mine Research Society
2. (primary) Geology of the South Wales Coalfield, Part V, the country around Merthyr Tydfil (Memoir, Sheet 231) — British Geological Survey

Record created: 15 September 2026 · Last researched: 15 September 2026