Dartmoor tin-mining

The Dartmoor tin mining industry is thought to have originated as early as pre-Roman times, and continued right through to the 20th century. Tin is smelted from cassiterite, a mineral found in hydrothermal veins in granite, so the uplands of Dartmoor, in Devon, England, were a particularly productive area. Many of the older sites carry the prefix Wheal (from a Celtic word meaning mine or works).

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Stannary laws

Mining became such an important part of life in the region that as early as the 12th century, tin miners developed their own set of laws (stannary laws) and, ultimately, their own parliaments (Stannary Parliaments). These laws applied to anyone involved in the industry.

Stannary parliaments were established in Tavistock, Ashburton and Chagford by King Edward I in 1305. Plympton followed soon after. A Devon stannary parliament is believed to have met in an open air forum at Crockern Tor in 1494 [1].

Anyone who broke a stannary law could find himself imprisoned at Lydford. The stannary courts were abolished in 1836.

Mining methods

  The simplest and earliest form of mining, known as 'streaming', simply involved collecting alluvial tin from stream and river beds, and required no complex tools or technology. Open cast mining followed, around the 16th century, and involved the digging of large trenches along the lodes, or veins of tin ore. Evidence of this early form of mining is evident on Dartmoor in the form of gullies and overgrown spoil heaps. Once gathered, the natural ore needed to be smelted to create 'white tin', which generally took place in a building known as a blowing house.

Underground mines did not appear until the 18th century, and in an area as waterlogged as Dartmoor, these were fraught with danger. Flooding occurred regularly, so waterwheels were often used to power pumps.

Man-made water channels called leats were dug to direct water from streams and rivers, following the contours of the hillsides, to the waterwheels. Many of these can be seen today, often still flowing with water.

The discovery of tin in the 'new world', particularly in the southern hemisphere, had a major impact on the Dartmoor industry, and many miners emigrated. The last tin mine on Dartmoor finally closed just before the Second World War.

Consequences

The effects of the large scale of early tin streaming were felt on the coast, as several harbours silted up due to the amount of fine material that was washed down the rivers. Because of this, in 1532 a Stannary Court decree ordained that all rubbish should be deposited in "old Hatches, Tipittes, miry Places, or other convenient Places" away from the main streams.^[1]

  The impact of mining on the Dartmoor landscape is still clear to see. Walkers on the moor will often stumble upon ruined blowing houses and mortar stones, featuring rows of semi-circular depressions, in which the ore was crushed. Many of the later mine shafts have now been filled in, but a few do still remain, fenced off to prevent walkers or animals from falling in.

References

• Harris, Helen (1972). Industrial Archaeology of Dartmoor. Newton Abbot: David & Charles, 24-69. ISBN 0 7153 4302 5.