Twyn-y-Waun Colliery

Overview

A Merthyr Tydfil drift mine whose extraordinarily thick coal measures — 97.5 feet of coal across eighteen seams — were recorded in detail by NMRS and independently confirmed by the British Geological Survey's own district memoir.

History

Twyn-y-Waun Colliery, also recorded as Tyn-y-Waun, was a drift mine owned by the Tynywaun Colliery Company by 1917 — a firm that was not a member of the Monmouthshire and South Wales Coal Owners Association. It worked the Upper-Nine-Feet seam at a thickness of 46 inches, and a detailed survey of the strata it passed through recorded a remarkable eighteen separate coal seams within 1,200 feet of strata, totalling 97.5 feet of coal: the Six-Feet seam alone ran to 13 feet of mixed coal and dirt, the Red Vein 21 inches, the Lower-Nine-Feet 9 feet, the Bute seam 30 inches, the Seven-Feet seam 76 inches, and the Five-Feet/Gellideg seam 13 feet 6 inches of mixed coal and dirt. The mine was not shown on Gordon's 1921 Map of the Coalfield. The locality's unusual seam thickness is independently confirmed in the British Geological Survey's own district memoir, which cites "a typical section, as at Twyn y Waun, east of Dowlais" for the Gellideg seam specifically — coal, clod, coal, shale, engine coal, shale and bottom (Gellideg) coal in close succession, drawing on an earlier 1933 geological survey. A landscape-archaeology survey of the wider Merthyr coalfield separately records extensive 19th-century patch workings for coal and ironstone in the ground between Longtown Cottages and Twyn-y-Waun, shown on the first-edition Ordnance Survey map of 1879.

Nearby mines

• Vanwain Colliery — 0.3 km W
• Coslet Colliery — 0.4 km NE
• Banwaun Colliery — 0.7 km N
• Penyard Colliery — 0.9 km W
• Price's Colliery — 1.1 km NE

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 mine's own workings passed through eighteen separate coal seams within 1,200 feet of strata, totalling 97.5 feet of coal, including a Six-Feet seam of 13 feet of mixed coal and dirt and a Five-Feet/Gellideg seam of 13 feet 6 inches. ¹
• The British Geological Survey's own district memoir independently cites "a typical section, as at Twyn y Waun, east of Dowlais" for the Gellideg seam specifically, drawing on an earlier 1933 geological survey — corroborating the locality's unusually detailed, thickly-bedded coal measures from an entirely separate, official source. ²
• A landscape-archaeology survey of the wider Merthyr coalfield records extensive 19th-century coal and ironstone patch workings in the ground between Longtown Cottages (Tre-hir) and Twyn-y-Waun, shown on the first-edition Ordnance Survey map of 1879. ³

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
3. (secondary) Merthyr Tydfil - Historic Landscape Character Area — Heneb (Glamorgan-Gwent Archaeological Trust)

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