Llanharan Colliery

Overview

A Powell Duffryn colliery on the steep south crop of the South Wales coalfield, sunk in 1922 after an 1870s failure, where Britain's first full horizon-mining scheme was launched in 1948; it closed in 1962.

History

Llanharan Colliery, originally called Bryn-y-Cae, stood near Llantrisant on the southern edge of the South Wales coalfield. A first attempt at two shafts in the 1870s got the South Pit to 144 yards, just below the Six Feet seam, but the ground was so wet and steeply inclined that it was abandoned; offered for sale in Cardiff in March 1882, it failed to reach its reserve.

Powell Duffryn tried again in 1922, deepening the South Pit and sinking a North Pit. Instead of eight seams the shafts passed through sixteen: a major east-west thrust fault had repeated the measures 750 to 800 feet lower down. The colliery was meant as a pilot for a larger scheme at Llantrisant, three miles away, abandoned after an explosion there in 1940. In 1935 Llanharan employed 610 and raised 200,000 tons.

Joint mapping by Powell Duffryn and the Geological Survey finally explained the thrust, and the company's general manager David Griffiths saw horizon mining, driving level stone roadways and reaching the steep seams from them, as the answer. Drivage began in October 1946 and the National Coal Board launched the system in 1948, the first full use of horizon mining in Britain. Output peaked at over 234,000 tons in 1952.

The ground defeated it. Of seven seams planned only one could be worked successfully, and an inspection found many roads in a deplorable state. Despite an investment of £9 million the colliery closed on 25 August 1962.

Geology

The south crop of the South Wales coalfield, where the seams are tilted so steeply along the anticline that they sometimes double back. A major east-west upthrust fault through Llanharan repeated the measures about 800 feet lower, so that the Lantern (Two Feet Nine) and No. 1 seams proved to be the same. Through 1,200 feet of ground there were eighteen seams totalling 97 feet 6 inches of coal. The Six Feet (No. 4 seam) was 75 to 84 inches thick, and the 'Thick' seam combined the Pentre Rider, Pentre and Lower Pentre.

Workings

Two shafts 1,000 yards from the southern outcrop: the South Pit, 15 feet across, the upcast, to the Gellideg at 454 yards, and the North Pit, 20 feet across, the downcast, to the Six Feet at 376 yards. From 1946 level horizons were driven through the measures, 15 feet wide and 11 feet 6 inches high, lined with steel arches; coal came down the steep faces on troughed pans and a spiral chute, worked faces were pneumatically stowed with crushed stone, and diesel locomotives hauled underground.

Closure

Only one of the seven seams planned could be worked successfully, and production fell sharply from 1959. The colliery closed on 25 August 1962 as unworkable, producing nearly 100,000 tons a year at the end.

What remains

Unknown.

Redevelopment

Unknown.

Related mines

• Werntarw Colliery — 87 men from Wern Tarw were transferred to Llanharan in 1951 to man its development scheme.

What's uncertain

Points where sources disagree or the record could not be settled; both accounts are kept. All open questions in the archive.

• Work on sinking two shafts at Llanharan began in 1873 but was abandoned because of financial difficulties. (disputed) ²

Recorded claims

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

• The South Pit was partly sunk in 1870 to 144 yards, just below the Six Feet seam, but was so wet and inclined that it was abandoned; in March 1882 it failed to reach its reserve at auction. ¹
• Work on sinking two shafts at Llanharan began in 1873 but was abandoned because of financial difficulties. (disputed) ²
• Powell Duffryn restarted the sinking in 1922, deepening the South Pit and sinking the North Pit, and found the seams repeated 750 feet further down by a thrust. ^1,2
• The South Pit, the upcast, was sunk to the Gellideg seam at 454 yards and the North Pit, the downcast, to the Six Feet at 376 yards. ¹
• The seams were so sharply tilted that horizon mining was the only way to extract the coal, the first time the system had been fully employed in the UK. ^1,2
• In 1935 the colliery employed 60 men on the surface and 550 underground and produced 200,000 tons. ^1,2
• Output was highest in the early and mid-1950s, over 234,000 tons in 1952. ³
• Despite an investment of £9,000,000 Llanharan Colliery closed on 25 August 1962 as its coal was unworkable; of seven seams planned only one was worked successfully. ^1,2
• The owners were the Powell Duffryn Steam Coal Co. Ltd, Powell Duffryn Associated Collieries Ltd and Powell Duffryn Ltd, and from 1947 the National Coal Board. ⁴
• Plans of the Five Feet, Nine Feet, Gellideg, Yard and Upper Nine Feet at Llanharan record abandonment in 1962. ⁵

Photographs & further reading

Sources

1. (secondary) Llanharan Colliery - Northern Mine Research Society — Northern Mine Research Society
2. (secondary) Llanharan Colliery - Welsh Coal Mines — Welsh Coal Mines
3. (secondary) Llanharan — Wikipedia
4. (primary) Durham Mining Museum - Llanharan Colliery (UK) — Durham Mining Museum
5. (primary) BGS mine plans: Llanharan (Five Feet, Nine Feet and Gellideg, abandoned 1962) — British Geological Survey / Mining Remediation Authority

Record created: 1 October 2026 · Last researched: 1 October 2026