Thursday, 2 October 2014

Cornwall's Submarine Mines


The short stretch of coastline in the St. Just region of Cornwall, between St. Ives and Land's End, is designated a Cornish Mining World Heritage site. In this area lies the highest concentration of tin and copper submarine deposits in the world, which were mined at Botallack, Levant and Geevor. Some of the engine houses of these coastal mines were positioned dramatically on the cliffs to allow the mine shafts to be sunk as close as possible to the mineral lodes, which extended beneath the ocean floor in a vast labyrinth of tunnels extending more than a mile out to sea. Positioning the pumping engines nearer sea level also reduced the distance the water had to be lifted before being discharged into the sea.
Last Sunday Barbara and I took a fairly easy six and a quarter mile walk (Elevation Gain 880 feet) commencing at the car park in the small mining village of Pendeen.

 

 
Geevor Tin Mine
The Geevor Tin Mine entrance is on the main road (B3306) between St. Ives and Land's End. Now a museum, the mine was operational between 1911 and 1990 during which time it produced about 50,000 tons of tin concentrate. During the 1970s and 80s I was a regular visitor, with parties of students from Camborne School of Mines, and it was here that many of Richard Mozley's inventions were piloted, such as the Bartles-Mozley Frame, and the Jones HIMS, which was developed by Dr. Jones at CSM, with his undergraduate project student Richard Mozley, to remove paramagnetic hematite from the ground ore.

Froth flotation was introduced to Geevor in 1931, to remove dense sulphide minerals, particularly arsenopyrite, from the cassiterite concentrate, and as we followed the track out of the mine to the coastal path, passing a set of old stamp mills and waterwheel, I noticed a junk yard with the rusting remains of the old banks of Wemco cells.

Stamp battery and waterwheel

Rusting Wemco flotation machines
Arsenopyrite was a problem with most Cornish tin ores, as it is a very dense mineral which reports into the tin concentrate. It had to be removed before smelting, as arsenic seriously embrittles tin metal.  As we proceeded further down the path we encountered the remains of the old Brunton calciners which, prior to flotation, were used to oxidise the arsenopyrite and produce arsenic trioxide which was condensed in a series of labyrinths.



Calcining produced much pollution of the local environment, as well as providing jobs which were probably more dangerous than those working underground.

Digging arsenic soot from the labyrinths
Reaching the coast path we arrived at Levant Mine, with its beam engine still in operation for the tourists. There are other operating beam engines in Cornwall, such as the excellent examples on the road between Camborne and Redruth (posting of 12 June 2010), but Levant's is the only one driven by steam.

Levant Mine
Copper and tin was mined at Levant for generations, and the mine workings extend over a mile out under the sea bed. The Levant Mining Company was formed in 1820 with a capital of £400, though Levant Mine first appeared on a map in 1748. By 1836, 320 men, 44 women and 186 children were employed on the site. In its first 20 years of business, £170,000 was made from mining copper. New technology was introduced to streamline production, and in 1857 the now-infamous man engine was installed. This engine carried men many fathoms up and down the mine, to and from work each day. In 1919, the man engine suffered a disastrous failure when a link between the rod and the engine snapped, killing 31 men. This tragedy was the death knell of Levant mining, which experienced a steady decline until its final closure in 1930.
The coast path west of Levant is heavily eroded, and has been split into several paths by thousands of walkers. I would strongly advise that you stay on the upper paths, however, as the lower paths wander very close to the edge of the 300 ft cliffs and as can be seen on the map of our walk, at one stage we had to retrace our steps as the path was becoming too dangerous to follow.


Of all the submarine mines, the Crowns Engine Houses of the mines at Botallack are the most painted and photographed in Cornwall (see also postings of 30 May 2010 and 8 February 2014). Dramatically perched on Crowns Rocks on the very edge of the precipitous cliff they are a testament to the skills of the 19th century engineers.

Crowns Mines, Botallack
Botallack mines in the 19th century
Botallack is an ancient group of mines formerly worked for tin, copper and arsenic. During the 1870s, as a result of a severe mining depression, Botallack began to make heavy losses, and in 1874 the Crowns section was abandoned.
The lower pumping engine house was built in 1835 and in 1842 a discovery of rich copper ore was made in the 85 fathom (510 ft) level on Crowns Lode, extending out under the sea. This lode was the principal copper producing lode of the mine, and 7,200 tons of copper ore were produced in 1842-1845. When copper mining became uneconomic it was largely tin from the inland parts of the mine that kept the mine going for the next 50 years, its peak production being in the 1860s.
Walking down the steep path to the upper winding engine house, built in 1862,  is a humbling experience, in the knowledge that the miners walked up and down this path daily before disappearing into the bowels of the earth via the Boscawen diagonal shaft to work the lodes up to a mile out to sea.


Returning to the cliff top we passed the ruins of the arsenic calciners and tin dressing floors, and then made our way back to Pendeen cross-country, making a hasty detour en route to avoid a herd of aggressive-looking bulls!

The remains of the Botallack tin dressing floors

Cross country to Pendeen

More Cornish Walks
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1 comment:

  1. Thank you for an excellent posting - I've added this to the bucket list!

    ReplyDelete

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