Description: China clay in Cornwall and Devon resulted from a sequence of events that began over 300 million years ago; molten rock cooled into granite: a mixture of quartz, feldspar and mica. As it cooled, the feldspar reacted with other minerals to form china clay. The pure white porcelain used by the Chinese, was discovered millennia ago and has always been a much-prized material. Despite many attempts to find it elsewhere, it remained elusive until a few deposits were found in parts of Europe and in America early in the eighteenth century, on which the search to find sources in Britain intensified. It was finally discovered in Cornwall in 1746, and was found to be a much finer quality than elsewhere in Europe. It is also the largest deposit in the world. The extraction of china clay has dramatically altered the landscape. For every 1 tonne of china clay, there are 9 tonnes of mineral waste products (a gritty sand of quartz and mica), which has led to the creation of large areas of tips. The now disused conical or "sky tips", can be seen near St Austell from as far away as Bodmin Moor.