Sunday, 23 March 2014

Across the moor to a once great copper mining district

Barbara and I were in the Dartmoor town of Bovey Tracey on Friday to attend the memorial service for Gavin Wonnacott.

We stayed overnight near Haytor then yesterday morning drove across the moor to the attractive Devon town of Tavistock, birthplace of Sir Francis Drake.

The River Tavy at Tavistock
After coffee, we travelled the short distance down into the Tamar Valley, on the border with Cornwall to visit what was, in 1850, the richest copper mine in Europe. Devon Great Consols, on the Devon side of the River Tamar,  is a consolidation of five adjacent mines which were worked for copper and arsenic in the nineteenth and early twentieth centuries.  The mines were named mostly after the shareholders or their wives, Wheal Maria, Wheal Fanny, Wheal Anna-Maria, Wheal Josiah and Wheal Emma. The site had the largest sulphide lode in the west of England, the "fabulously rich" mineral vein, in the slates known locally as 'killas', containing deposits of chalcopyrite and arsenopyrite. At its peak, Devon Great Consols employed around 1,300 people.

Devon Great Consols was in operation from 1844 until 1900 and then again from 1915 to 1930. Copper was extracted first and in total over 750,000 tons of copper ore were recovered. Copper reserves started to run out around 1870. At this time, demand for arsenic increased due to its use in the dyeing, paint and glass industries, as well as a pesticide in the cotton fields of the USA, and Devon Great Consols became the largest arsenic mine in the world. In the 1870s half the world’s arsenic production was estimated to come from half a dozen mines in the Callington and Tavistock area, including Devon Great Consols.

The desolate Devon Great Consols landscape
Little remains now but a desolate landscape, but we walked along the original mineral railway route, now a mountain bike trail, to the remains of the Wheal Anna Maria arsenic workings. Around 72,000 tons of arsenic were refined on this site by calcining and in total yielded 72,000 tons of product.

The remains of the Brunton Calciner at Wheal Anna Maria
Arsenic labyrinth, 19th century
The Brunton Calciner, which had an enclosed revolving hearth,  was also commonly used in Cornwall for roasting tin concentrates to drive off the arsenic as poisonous arsenic trioxide, which was condensed as a 'white soot' in long labyrinths, which were periodically dug out by hand to recover the oxide, surely one of the worst ever jobs in mining!

The remains of the arsenic labrynth

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