Nantymwyn Mine

Overview

Nantymwyn, on the ridge above Rhandirmwyn in the upper Tywi valley, was one of the largest and most productive lead mines in south Wales — employing over 400 people at its Georgian peak under Lord Cawdor — before closing for good in 1932.

History

Mining at Nantymwyn is believed to date back to Roman times, with a documentary reference to a mining ‘royalty’ of one-eleventh of ore produced at Rhandirmwyn as early as 1304. Modern workings began around 1742–47 under the ownership of Lord Cawdor, reaching their heyday in the late 18th century under the resident agent Mr Rolley; by the 1770s Nantymwyn was the largest lead mine in south Wales, employing over 400 people, with a recorded annual output of around 4,000 tons of ore, and profits reputed to have earned its owner some £300,000. Total output over the mine's life is estimated at around 100,000 tons of lead ore. The artist John ‘Warwick’ Smith painted the mine twice in 1792; both works are now held by the National Library of Wales in Aberystwyth. Underground, ore was moved along narrow level communications in sharp, narrow boats of around 5 tons, which workers in places propelled by pushing their feet against the tunnel ceiling. After closing in 1830, the mine reopened three years later and continued working until 1902; further unsuccessful attempts to reopen it followed in 1915, 1923 and 1930–32, before it closed for good in 1932.

Workings

Ore was moved underground in narrow, sharp boats of around 5 tons along level communications branching from the mine.

What remains

The site today survives as opencasts, ruined buildings and dressing floors on the ridge of Pen Cerrig-mwyn above Rhandirmwyn.

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.

Disasters & major incidents

• Nantymwyn dynamite explosion, 1892
  28 March 1892 · Explosion · 2 fatalities
  Two Cornish miners, William Beswetherick and John Lewarne, died after a box of gelatine dynamite they were handling caught fire and partly exploded underground — an incident that prompted a formal report to the Home Secretary by HM Inspector of Explosives.

Recorded claims

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

• A documentary reference records a mining ‘royalty’ of one-eleventh of ore produced at Rhandirmwyn as early as 1304. ¹
• In the 1770s, Nantymwyn was the largest lead mine in south Wales, employing over 400 people, with a recorded annual output of around 4,000 tons of ore; the mine is reputed to have earned its owner some £300,000. ¹
• The mine's total recorded output is estimated at around 100,000 tons of lead ore. ¹
• The artist John ‘Warwick’ Smith painted Nantymwyn twice in 1792; both works are now held by the National Library of Wales, Aberystwyth. ²
• Ore was moved underground in narrow, sharp boats of around 5 tons, which workers in places propelled by pushing their feet against the tunnel ceiling. ²
• After closing in 1830, the mine reopened three years later and continued working until 1902; further unsuccessful attempts to reopen it followed in 1915, 1923 and 1930–32, before it closed for good in 1932. ^1,2

Photographs & further reading

This page doesn't try to reproduce everything — these are the best original sources found for this mine.

Images

Sources

1. (secondary) Nant y Mwyn lead mine — Aspects of Wales
2. (secondary) Nantymwyn lead mine — Rhandirmwyn.net

Record created: 19 August 2026 · Last researched: 20 August 2026