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Ball clays are fine-grained and plastic sedimentary clays that are distinct for their white or off-white colour when fired.

In the UK, ball clays occur only in Devon and Dorset, occurring in the Wareham Basin (Dorset) and the Bovey and Petrockstowe Basins (Devon). These are globally significant deposits, and the UK is leading world exporter of ball clays, particularly for those used in sanitaryware casting.

The clays are deposited by sedimentary geological processes that produce layered strata, interspersing high purity ball clays seams with interburden consisting of sand and lower purity, lignitic clays. The interburden must be extracted to access the ball clay and this is the primary source of waste from the ball clay mining process (BGS, 2011).

Like slate and china clay, the wastes derived from ball clay excavation are exempt from the aggregates levy and both sand and lignite are sold as secondary products. Some lower-grade ball clay seams are also sold as supplementary clays for brickmaking, useful for producing lighter firing bricks (Bloodworth et al., 2006).

The sand wastes derived from ball clay extraction can still contain up to 20% clay, which is washed off to achieve a clean saleable construction sand and discharged into settlement ponds (Bovey, 2007). Based on the makeup of the material, this residue will contain a combination of silt-grade quartz sand and clay residue derived from a wide range of geological deposits.