On Wednesday 23rd March, we visited Wheal Martyn clay works in St Austell. The weather was glorious, and the behaviour of the children was impeccable. They all listened carefully to the tour guides and asked a number of inquisitive questions.
We learnt so much about china clay or kaolin. It is formed as a result of decomposition of some of the feldspar in granite. The feldspar changes into a white powder, but the other parts of the granite, mica and quartz remain unchanged. Once refined, the white powder is used as an ingredient in all sorts of familiar products including:
- Ceramics – such as porcelain
- Paper – as a glossy coating or filing
- Rubber – for example, tyres
- Pharmaceuticals – such as paracetamol
- Cosmetics – used by brands such as Lush and L’Oréal
- Aircraft components
As the traditional tin and copper mining industries in Cornwall started to decline in the late 19th century, the china clay industry grew and far outstripped those industries in size, economic contribution, mining technology and research into micro-mineralogy. The value of china clay sold to date is more than double the value of tin and copper sold from Cornwall, estimated at around £14 billion.
The clay works began at Wheal Martyn in the 1820s and were started by Elias Martyn on the Carthew Estate. Elias became one of the major clay producers in Cornwall and by 1869 he was producing 2,000 tons of clay a year at Wheal Martyn. After his death in 1872, the family kept the land but leased the works to other operators and the site continued to operate until 1969.
During the afternoon, Puffin class took part in a workshop learning more about rocks and soils. Gemma, our workshop leader, was very impressed with how much we already knew! We classified different rock types, made volcanoes and created our own fossils using clay. It truly was an amazing day!