At one time, most of what is now the British Isles was covered by sea, upon the bed of which vast deposits of mud and silt collected. In time, the accumulated weight of the sediments caused them to become compressed and hardened, converting them from loose sediments into highly cleavable forms of rock - the slates and shales which still abound on the costs of Cornwall and Devon to this day.

At the time when the sediments were being laid down, great landmasses were drifting towards each other on a collision course. The pressures generated by this movement caused the seabed to fracture and fold. The folding process was accompanied by intense subterranean activity, the masses of molten rock forced their way upwards.

When the rock cooled, it became granite, a rock made of a mixture of quartz, feldspar and mica. The formation of the granite took place between 290 and 270 million years ago and today it forms the rocky backbone of the south-west of England, being exposed in the Scilly Isles, Lands End, Carnmenelis, Hensbarrow near St Austell, Bodmin Moor and Dartmoor.

Granite is one of the commonest igneous rocks, but varies considerably in its composition from place to place. While the quartz is never anything but quartz, the feldspar can be a silicate of alumina with potash, soda or lime and the mica the potash-rich muscovite or the iron-rich biotite. In some parts of the South West, the feldspar in the granite is higher in its soda content than its potash content and these places are where china clay is found today. It came into being through a complex sequence of events. While the molten rock was still cooling, it was attacked successively by steam, boron, fluorine and tin vapour, these acting on the alkali content of the feldspar and converting it into china clay.

The South Western granite has been converted into china clay only in those areas where the feldspar contained the necessary high soda content. Though no china clay is to be found in the Scilly Isles, it occurs in some places in the Lands End peninsula, at Tregonning Hill, near Helston, at Carnmenellis, on the St Austell moors around Hensbarrow Beacon, on Bodmin Moor and on parts of Dartmoor. The greatest amount of china clay is found on the St Austell moors.The china clay deposits are roughly funnel-shaped, with the widest part uppermost, and the base of these funnels can be as much as 300 metres deep. In certain locations, the deposits occur in clusters, and here one finds the largest of the china clay workings, including Blackpool, Goonbarrow, Littlejohns and Melbur in the St Austell area, Stannon on Bodmin Moor and Lee Moor on Dartmoor.