Cefn Coed Colliery

Also known as	Cefn Coed Colliery Museum, Llwyn-on Colliery
Location	Crynant, Dulais Valley, Neath Port Talbot — 51.7166, -3.7594 (approximate)
Commodity	Coal
Type	Coal
Worked	Sinking begun 1921; completed 1928–20 April 1968
Maximum depth	No. 2 downcast shaft 2,106 ft 1 in to the Eighteen-Feet seam — claimed the deepest anthracite mine in the world
Operators	Llwyn-on Colliery Company (1921–1928), Amalgamated Anthracite Collieries (1928–1947), National Coal Board (1947–1968)
Status	Researched

Overview

Three attempts to sink here failed before the fourth got through the Blue Pennant sandstone, and what it reached was the deepest anthracite in the world: over 2,100 feet down, in a valley where the coal was worth the trouble and the sinking very nearly wasn't.

History

Sinking at Cefn Coed was attempted three times without success before the Llwyn-on Colliery Company began again in 1921. Work stopped, resumed in 1924, and the shafts were not finished until 1928 — seven years to get through hard Blue Pennant sandstone. The Amalgamated Anthracite combine, which had bought out the Llwyn-on company, took it on and brought the pit into production, its winding and workings driven by steam raised on gas drawn from the old workings. Employment peaked at around 1,200 in 1933 and was still over 900 in 1945. The National Coal Board took it over in 1947. Numbers fell steadily from the mid-1950s — 552 men by 1961 — and the colliery closed on 20 April 1968 despite a petition against closure carrying 51,500 signatures.

Geology

The western end of the South Wales coalfield yields anthracite: coal carried further through the coalification process than the steam and house coals to the east, harder, with a very high carbon content and burning almost without smoke. It is the most valuable coal in Britain and the most difficult to reach, because the same earth movements that made it also buried it deep and threw hard Pennant sandstone over the top. Cefn Coed's nine workable seams held some 72 feet of coal in total, the best of it in the Big Vein.

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

Workings

Two shafts, both twenty feet in diameter. The No. 1 upcast reached the Four-Feet White seam at 2,094 feet; the No. 2 downcast went to the Eighteen-Feet seam at 2,106 feet and one inch, and it was on that depth that the colliery's claim to be the deepest anthracite mine in the world rested. Nine major seams were worked, among them the Graig at 34 inches, the Six-Feet at 33 and the Peacock at 42 — thin coal, a long way down.

Closure

Cefn Coed closed on 20 April 1968. Coal Authority abandonment plans for the colliery are dated October 1967 and 1968. Neighbouring Blaenant took over some of the ground and worked on into the 1990s.

What remains

Preserved as the Cefn Coed Colliery Museum, opened in 1978, with the surface buildings conserved and the steam winding engines still in place. Among the machinery preserved on site is the 1927 Worsley Mesnes horizontal duplex steam winding engine that worked the No. 2 shaft — the largest running winding engine in Wales.

Unusually complete for a South Wales colliery: the original steam boilerhouse and chimney, the compressor house, the electrical generating house, and the No. 2 winding house with its original steam winding engines. Both headframes and the engine house range with its steam capstan engine are listed.

Redevelopment

A museum since 1978, and the subject of proposals to develop it further as a major heritage attraction for the Dulais Valley.

Abandoned workings can be dangerous — unstable ground, uncapped shafts, flooding and bad air are common even where a site looks safe from the surface. This entry describes history and general location only; it is not an access guide.

Recorded claims

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

Three attempts to sink at Cefn Coed failed before the Llwyn-on Colliery Company began in 1921; work halted, resumed in 1924, and the shafts were completed in 1928. ¹
Both shafts were 20 feet in diameter: the No. 1 upcast reached the Four-Feet White seam at 2,094 feet and the No. 2 downcast the Eighteen-Feet seam at 2,106 feet 1 inch, claimed as the deepest anthracite mine in the world. ¹
Nine major seams were worked, including the Graig at 34 inches, the Six-Feet at 33 and the Peacock at 42, with about 72 feet of coal in total. ¹
The shaft and workings were powered by a steam engine fuelled by gas drawn from the old workings. ²
Employment peaked at around 1,200 in 1933 and was over 900 in 1945, falling to 552 by 1961; output ran between roughly 80,000 and 200,000 tons a year in the 1950s. ¹
The colliery closed on 20 April 1968 despite a petition of 51,500 signatures; abandonment plans are dated 27 October 1967 and 1968. ^3,1
The site has been the Cefn Coed Colliery Museum since 1978, retaining the steam boilerhouse and chimney, compressor house, electrical generating house and the No. 2 winding house with its original steam winding engines. ²
The 1927 Worsley Mesnes horizontal duplex steam winding engine that powered the No. 2 shaft survives on site and is the largest running winding engine in Wales. ⁴