South Terras Mine

Overview

Britain's only uranium and radium mine, worked in turn for iron, uranium and finally radium — supplying ore for early cancer treatment in London — and now one of the most radioactive sites in Britain.

History

South Terras opened around 1870, initially worked by the South Terras Tin Mining Company for iron ore and ochre, with only minor tin returns. In 1885 miners encountered an unusual apple-green mineral, later identified as torbernite and nicknamed 'Green Jim' locally after the mine's then managing director, James Harris-James. Uranium Mines Ltd took over in 1889 to exploit the discovery, roughly tripling the workforce to around 30 men, and for a period sold uranium ore to Bettmann & Kupfer in Germany for use in uranium glass manufacture. The mine's most distinctive chapter began in 1905, when British Metalliferous Mines Ltd took over and pivoted toward radium extraction, driven by soaring demand after Edward VII's 1906 radium-based cancer treatment. Operations were reorganised in 1921 to extract radium on site — the only mine in Britain ever equipped to do so — under manager Marcel Pochon, formerly an assistant to Pierre Curie in Paris. The 'Kingsway Syndicate' contracted to buy 7.5g of radium bromide from South Terras, worth over £30,000, to supply the London Radium Institute, which began treating patients around 1906-07. The mine was abandoned in the early 1930s; Pochon himself went on to manage the Eldorado radium refinery in Canada from 1932, later a critical supplier to the Manhattan Project. It is often repeated that Marie Curie herself sourced early radium samples from South Terras, though the better-documented connection runs through Pochon and the London Radium Institute rather than Curie's own laboratory directly — the two claims are not necessarily the same thing, and this site has not been able to independently confirm the stronger version.

Geology

South Terras is unusual in Cornwall for hosting a lode roughly 250 fathoms (457m) long in which uranium minerals were the principal ore, rather than a by-product: hydrated uranium minerals such as torbernite occurred close to the surface, giving way to pitchblende (uraninite) at greater depth, which became the mine's economic mainstay in its later radium years.

Workings

Ore was worked from underground levels typical of Cornish hard-rock mining, targeting the uranium-rich lode directly rather than as a secondary product of tin or copper working.

Closure

The mine was abandoned in the early 1930s once the radium operation ceased to be viable; it received Site of Special Scientific Interest designation in 1996 for its rare uranium mineral suite.

What remains

The site carries an extreme radiation hazard: radon measurements between 1992 and 2000 recorded levels exceeding 3 million Bq/m3 deep within the adit, described as among the highest for any non-nuclear site in Europe, and access is restricted accordingly.

Adit entrances, spoil heaps and mineral-stained ground remain, now studied as a natural analogue site for uranium contamination research.

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.

This site carries genuine, serious radiological hazards beyond the generic risks of old mine workings — extremely high radon levels have been measured underground — and should not be entered.

Recorded claims

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

• Miners encountered an unusual apple-green mineral, later identified as torbernite, in 1885; it was nicknamed 'Green Jim' after the mine's managing director James Harris-James. ¹
• From 1921 South Terras was equipped to extract radium on site — the only mine in Britain ever to do so — under manager Marcel Pochon, formerly an assistant to Pierre Curie; the 'Kingsway Syndicate' contracted to buy 7.5g of radium bromide, worth over £30,000, to supply the London Radium Institute. ^1,2
• It is often stated that Marie Curie herself sourced early radium samples from South Terras; the better-documented historical connection is through Marcel Pochon (a former assistant to her husband Pierre Curie) and the London Radium Institute, and this stronger claim about Marie Curie personally has not been independently confirmed here. (disputed) ³
• Radon measurements taken between 1992 and 2000 recorded levels exceeding 3 million Bq/m3 deep within the mine's adit, among the highest recorded for any non-nuclear site in Europe. ^1,2

Mine plans

Sources

1. (secondary) South Terras mine — Wikipedia
2. (secondary) Abandoned Cornish mine may hold clues to uranium clean-up — Chemistry World
3. (secondary) South Terras Mine Cornwall — Cornwall Calling

Record created: 21 August 2026 · Last researched: 21 August 2026