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China clay mining is a complicated process which can be split into three distinct sections - opencast mining, refining and drying.

Known as pit operations, this process firstly requires the removal of ground overlying the clay. This is known as overburden, which can vary in depth between one and fifteen metres. Once the clay is exposed, the method of mining is best described as a hydraulic mining process. This means, quite simply, that a jet of water under enormous pressure is fired at the pit face from a water cannon known in the industry as a monitor. This liberates from the quarry face the china clay, together with sand and mica. The material runs in slurry form to the lowest part of the pit, known as the sink, where it is lifted by centrifugal pumps to mechanical sand classifiers, where the more coarse sand elements are removed. The sand is disposed of on belt conveyors, which deposit it on low profile tips that can then be landscaped and seeded with grass.

Having removed the coarsest of the sand, the clay suspension is then transported by underground pipeline to the second process: refining.

Refining consists of a series of mineral processing techniques - predominantly sedimentation - designed to remove the smaller sized waste particles, mainly minerals such as very fine quartz, mica and feldspar, leaving only the required china clay behind. Value can also be added to the clay at this stage by a variety of processes designed to engineer size and shape of the product, together with the use of a chemical bleaching process that improves its whiteness

Having refined the clay, it is moved on to the final process: drying.

Drying consists of firstly converting the liquid clay into a solid material by a process known as filtration. The products of filtration normally have a moisture content of about 25%. Passing the clay through a thermal drier further reduces this moisture content. The driers are fired by natural gas and see a product emerging at around 10% moisture. The product is normally sold in pelletised form - particle size ranges from 6-12mm.

Despite its extensive china clay deposits in Cornwall and Devon, Imerys continually researches new methods of extending the life of its reserves. For example, new refining techniques have been developed to obtain more china clay per matrix and sophisticated technical innovations provide the ability to adjust particle size. Consequently, the company is confident that its reserves are sufficient to last for many generations.

87% of the china clay produced in is exported and some 60 grades are produced. The major markets are Western Europe, with the Nordic countries being the most important.