Early ore extraction involved working an alluvial deposit, either in a stream or the soil. The evolved process for extracting ore was ‘streaming’, suspending the ore in water where the heavier tin bearing minerals would sink and the rest could be washed away. In the medieval period deposits on the surface became scarce and miners were forced to dig for the ore underground. However, in a few areas the age old process still continued.Cassiterite/Tin was an important commodity and King John saw an opportunity to tax the workers and control the trade. The tinners were good negotiators, considering the King was going to have his own way anyway, and they emerged with their own charter which made them ‘free’ men and excused military service. They had to pay a tax on the tin they provided but nothing else. The miners were allowed to create their own ‘Stannary’ parliament which operated in the 4 main mining areas called Stannaries. Each Stannary then elected 6 representatives, Stannators, for their Parliament in Lostwithial.
Cassiterite (Tin ore) was the main ore sought as it was easily obtainable near the surface, but soon mines had sank to depths of 100 meters. This led to problems with flooding and primitive attempts at solving the drainage problem became more desperate. Some mines went ever deeper, particularly where veins of copper were detected. By the 1700’s the resolution was simply to dig large horizontal tunnels, adits, to take the water away. In 1748 John Williams, the owner of Poldice Mine, and Sir William Lemon constructed a large adit called the Great County Adit which drained the Poldice mine into the Carnon River. It was extended through 38 miles of tunnels to cover 40 mines in the area draining 13 million gallons a day. The system fell into neglect but still exists as one of the world’s largest tunnels, a great feat of Cornish engineering. When tin became scarce, or its price dropped, copper would then be worked in the deeper parts of the mine, some even venturing out under the sea. Some mines became so big that they swallowed up smaller mines. The term ‘Consols’ or ‘Setts’ is a mine system that consists of a group of mines that is managed by a single Company and you see the term used quite frequently.
By the 18th Century, Cornwall had become a major producer of tin and copper as well as lead, silver and arsenic. Cornwall lacked its own coal resource so steam power, by necessity, had to be more advanced. The development of the Cornish Beam Engine solved the persistent problem of removing water from deep mines. By 1740 the deep mining of copper was in progress and demand for the ore was high. At its peak, the copper industry employed 30% of Cornwall’s male workforce and encompassed not only mining but also the refining and smelting of ore as well.
A new steam process had been developed by Harvey’s of Hayle improving the pumping of water out of the mines, the moving of miners up and down the shafts and in working the big new ore crushing machines on the surface. The ports of Hayle and Portreath were developed to support the export of copper ore to the big smelter in Swansea and the import of Welsh coal. William Bickford invented the safety fuse in 1831 and made blasting safer. In the 1860’s, Nobel invented a high explosive which was based on nitro-glycerine. This was widely welcomed as it reduced the fumes significantly and broke the rock into finer pieces making it easier to haul away. In the mid-19th century new deposits of copper were being discovered elsewhere in the world and immediately the price for Cornish copper dropped. The best deposits of Cornish copper had all but been depleted and copper mining in Cornwall was in decline. Tin mining had been overshadowed by the search for copper but some new tin seams had been discovered in the deeper mines and this had started a second boom for tin. In an attempt to survive, some mines switched to mining for Uranium, Zinc, Silver, Antimony and Arsenic. Some survived into the 20th Century but mainly by producing arsenic, like the Devon Consols Mine in Tavistock. Many mines had closed by the nineteen twenties and the last big mine that was left, closed about 25 years ago.
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