Treforgan Colliery

Overview

A National Coal Board anthracite drift mine at Crynant in the Dulais valley, driven in 1963-66 on the site of the old Llwyn-on Colliery. Meant to be short-lived, it became the most profitable anthracite mine in Britain; a £7 million extension into deeper seams failed, and it closed in September 1985.

History

The first turves for Treforgan were cut in June 1963, when the Dulais valley had just seen four of five threatened pits reprieved. The National Coal Board drove the mine between 1963 and 1966, at a cost of about £1.5 million, on the site of the old Llwyn-on Colliery, abandoned in 1927. Two slants were driven down at 1 in 3 to the Red Vein anthracite, and in 1967 it was linked to Cefn Coed Colliery for ventilation. Its coal went by road to the Abernant washery.

Treforgan was meant to have a short life on limited Red Vein reserves, but its output per man made it one of the most profitable mines in Britain and the most profitable anthracite mine; in January 1968 it was called the most highly automated mine in the South Wales Coalfield. It employed 316 in 1969 and about 475 through the 1970s. In July 1971 a manriding train ran away and forty-three men were hurt.

With the Red Vein near its end, the Board decided in the 1970s to spend £7 million opening the Nine Feet and Bute seams below, with a new drift bringing coal from about 770 yards down. By 1981 those faces were working with self-advancing supports, but the manager reported bad geology and steep gradients, and early in 1983 the mine had no working face. After the strike of 1984-85 a planned link to Aberpergwm was dropped, and Treforgan closed on 30 September 1985. Part of the site is now Crynant Business Park.

Geology

Anthracite of the South Wales Coalfield: the Red Vein, then the Upper Nine Feet and Bute seams below it.

Workings

Two slants at 1 in 3 to the Red Vein, a later drift and long roadways to the Nine Feet and Bute; ventilation link to Cefn Coed from 1967.

Closure

Closed on 30 September 1985, after the Nine Feet and Bute development failed and a planned link to Aberpergwm was abandoned after the 1984-85 strike.

What remains

The colliery has been demolished; its tips are grown over with silver birch.

Redevelopment

Part of the site is occupied by Crynant Business Park.

Related mines

• Cefn Coed Colliery — Treforgan was linked to Cefn Coed for ventilation in 1967.

Recorded claims

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

• The National Coal Board developed Treforgan as an anthracite drift mine between 1963 and 1966, at a cost of £1.5 million, on the site of the old Llwyn-on Colliery. ^1,2
• Two slants were driven at 1 in 3 to the Red Vein seam. ²
• It became one of the most profitable mines in the UK and the most profitable anthracite mine. ^1,2
• In 1969 it employed 285 men underground and 31 on the surface. ²
• The National Coal Board invested £7 million to open the Nine Feet and Bute seams, with new drifts bringing coal from a depth of 770 yards. ^1,2
• In July 1971 forty-three miners were injured when their manriding train ran loose. ²
• Treforgan closed on 30 September 1985. ¹
• The colliery has been demolished and part of its site used for Crynant Business Park. ³
• A mine plan survives of Treforgan Colliery's workings in the Bute seam. ⁴

Photographs & further reading

Sources

1. (secondary) Treforgan Colliery — Welsh Coal Mines
2. (secondary) Treforgan Colliery, Crynant, Dulais Valley — Northern Mine Research Society
3. (secondary) Crynant — Wikipedia
4. (primary) TREFORGAN COLLIERY MINE, Bute seam: mine plan catalogue entry — British Geological Survey / Mining Remediation Authority

Record created: 8 October 2026 · Last researched: 8 October 2026