The Clays

Mining in Cornwall, in the southwest of England, began in the early Bronze Age, around 2150 BC. Tin, and later copper, were the most commonly extracted metals. Some tin mining continued long after the mining of other metals had become unprofitable, but ended in the late 20th century. In 2021, it was announced that a new mine was extracting battery-grade lithium carbonate, more than 20 years after the closure of the last South Crofty tin mine in Cornwall in 1998.

Historically, tin and copper as well as a few other metals (e.g. arsenic, silver, and zinc) have been mined in Cornwall. Tin deposits still exist in Cornwall, and there has been talk of reopening the South Crofty tin mine. In addition, work has begun on re-opening the Hemerdon tungsten and tin mine in south-west Devon. In view of the economic importance of mines and quarries, geological studies have been conducted; about forty distinct minerals have been identified from type localities in Cornwall (e.g. endellionite from St Endellion). Quarrying of the igneous and metamorphic rocks has also been a significant industry. In the 20th century the extraction of kaolin (Clay) was important economically.

The deposit required work to extract it from the degraded granite. Using water he would separate the decomposing granite and the soft talc like material. Once refined, this material could be worked as kaolin and was quickly taken up and used in the British manufacturing processes. If the Chinese product was finer, this was disregarded, and the Cornish market exploded. A deposit north of St Austell was revealed to be the largest in the world and a global industry began to rapidly develop.

The material didn’t require deep mining like tin or copper, and was retrieved using open cast mining. It was then blasted with water cannons, to separate the soft clay from the decomposing granite. The water turned white and ran off into the rivers, and as they ran down into St Austell Bay, the whole sea would turn white. Even in the 1970s, locals remember swimming in milky white water. For each tonne of clay extracted, there was five tonnes of mica waste. When the two materials were separated, the slag was taken and dumped back on the land, in long hills or in large conical structures. These large white hills were soon referred to as the Cornish Alps or Pyramids and rapidly changed the local skyline. Finally the good wet clay was recovered and laid out in massive long low buildings, known as dries. With a chimney at each end, heat was run along the base and the clay above would slowly dried out. Women, known as bal maidens, would shape and turn the mixture until it resembled dry blocks, that could be cut and easily transported up country and overseas to the waiting mills. This industry far out performed fishing or farming and there wasn’t a single family that wasn’t in some way impacted by the new industry.

Looking about you today every strange hill you see, will be a slag heap. The largest pyramid towering over St Austell is now only vaguely white but it must have been an incredible sight before nature began to reclaim it. Some of the heaps have been flattened and terraformed providing excellent walks and bike rides, and if you look at the floor you will see, that rather than soil, the ground is made up of a gritty mica residue. Strange building are hidden under trees and ivy, overs can be explored in safety. Some areas of the terraformed lands still seem reminiscent of a foreign planet, others are more established, and the flora and fauna has established itself and smoothed over the harsh scars on the landscape. The world famous Eden Project is built in a clay pit, showing the ingenuity of mankind to reclaim the land. Across the countryside are large lakes where the miners dug down to extract the raw material. As well as the lakes are large shallow pans of water, full of strange glowing green water, each pan a slightly different shade, covering many acres.

Nowhere in mid-Cornwall is untouched. Although the industry is still active here, it has declined with the discovery of a massive deposit in Brazil. The industry has moved to a fresher source, that is easier to extract with cheaper labour costs. It is hard to look around at some of the towns and villages today and appreciate that these were once the white hot hubs of industry at the top of a global market. A time when Cornwall led the world.