China Clay (rocks which are rich in Kaolinite) was first used by the Chinese over 1,000 years ago as the base material for the manufacture of porcelain. Chemically speaking, Kaolinite is hydrated Aluminium Silicate and is formed by the weathering of granite rocks which contain the mineral Feldspar. Echoing the common name, ‘Kaolinite’ is derived from the Chinese word Kao-Ling or literally ‘High Hill’. The western world envied the quality of Chinese porcelain and searched hard through the 18th century to find the raw material in Europe or America.
It was a Quaker potter, William Cookworthy, who at last made the discovery of China Clay in Cornwall at Tregonning Hill in 1746, and it was soon realised it was of a much finer quality than elsewhere in Europe. The deposits he found have been worked for 230 years and are amongst the largest in the world. Around 120 million tons of China Clay have been produced in Cornwall since deposits were first discovered and reserves are estimated to be sufficient for perhaps another hundred years.
Cookworthy experimented with various samples and in 1768 took out a patent to use the material, soon producing items at his Plymouth Porcelain Factory. Until that time English pottery had consisted of coarse earthenware and stoneware ceramics and had suffered considerable competition from elsewhere. As more potteries made use of porcelain, so the demand grew and by the early nineteenth century the kaolin industry had become highly successful. In addition, by the middle of the nineteenth century, china clay was increasingly being used as a raw material by the developing paper industry. Early in the twentieth century, the industry was made up of some seventy or so individual producers, each competing on price. By 1910 production was approaching a million tons a year and paper had completely overtaken ceramics as the prime user. Over 75% of output was exported, with North America and Europe being major markets, and the china clay industry in Cornwall and Devon held a virtual monopoly on supply to the world.
The Directors of E.C.C. Just after World War I in 1919, the three leading producers joined forces, forming English China Clays Limited, placing almost 50% of the industry’s capacity under one banner. The new company, ECC, was to become the leading clay producing company for the rest of the century, laying down the foundations of the modern industry. In 1999, ECC was taken over by the French Company IMERYS.
Situated on the edge of the massive China Clay pits, Wheal Martyn is the site of two Victorian china clay works, now a Scheduled Ancient Monument. The site now hosts a museum that tells the story of this fascinating industry and the people who worked and lived in the shadows of Cornwall’s iconic ‘white pyramids’.