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South Terras Uranium Mine  -  St Stephen Area

Ordinance Survey Landranger map 200 - Grid ref SW 935-523South terras mine

We visited South Terras in summer 2001 and again in April 2002. The mine site covers the area mainly to the left but also to the right of the lane just after the bridge over the river Fal coming from the east.

The area of the mine including the chimney (pictured above) plus some mine buildings in various states of ruin is enclosed in some overgrown woodland surrounded by the path leading off left from the road after the bridge, and the river Fal.

Further along the path are some more mine buildings (pictures below of parts of the upper mine buildings) against the hillside behind an area of open ground used by the local farmer.

Now for the Uranium hunting!. Even standing near the site the counters were chattering wildly, and once you step into the wooded area, there is a considerably higher count. The ground around the area is literally covered in radioactive rock samples, some on the surface and some just below the topsoil. Even the walls of the mine buildings have chunks of highly radioactive pitchblende in them!.

We collected many samples, most of which still have to be identified. However, we believe that the samples were mostly greenstone and iron ore mixed with pitchblende.

Some areas of the mine that are particularly radioactive are : 

An area on the side of the track which runs between the wooded area of the mine and the mine and the clearing used by the local farmer. We measured a count of about 120 microsieverts there.

A rectangular mine building with no roof next to the clearing used by the farmer. We measured about 100 microsieverts there.

Because the OS map is vague about the area and the actual mine site so small, the detail diagram should be used for close location.

OS map of south terras

South terras diagram

Checking the wall

Checking the radioactivity of the walls of the mine buildings (high).

Radioactive ground

Very hot area just to the north where the dirt track winds around the back of the site. Off the scale just sitting on the ground!! (200 counts per second). We dug for a here but found only radioactive sand, perhaps this was sediment left over from the radium production of the mine?.

Settling pond

The radium settling pond in the upper mine buildings area.

History of the mine

Union mine is better known as South Terras Mine and is between the villages of St. Stephen and Grampound Road. The mine was originally worked for iron, and the uranium lode was discovered in 1873. The bulk of the ore, mainly pitchblende, was worked out when the mine closed in 1900. However the operating life of the mine spanned approximately six decades.

In it's later years, South Terras was mainly worked for Radium from the spoil tips due to it's increasing demand and high value.

The mine was reopened several times and ore recovered from the dumps before finally closing in 1929. A total of 736 tons of ore was produced, including 286 tons from the dumps. The early production was sent to Germany for making green glass, and contained on average about 11 per cent U3O8, although the best ore contained up to 36 per cent. The dumps used to be a fruitful source of uranium ores for amateur geologists with army-surplus Geiger counters.

For a more detailed history of South Terras go to the Dangerous Laboratories visit of this mine.

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