Ball clays are kaolinitic sedimentary clays with 20-80% kaolinite, 10-25% mica, and 6-65% quartz. The number of main minerals, accessory minerals, and carbonaceous elements such as lignite varies between localised seams within the same deposit. They are fine-grained and pliable in nature, and when burnt, unlike most earthenware clays, they produce a high-quality white-colored pottery body, which is why they are so popular with potters. Due to the complex geological variables required for their production and preservation, ball clays are rather rare deposits.
It varies from china clay in that it is more flexible and less refractory. Ball and china clays are chemically similar, with the exception that the latter has a higher amount of silica. It got its name from the practice of extracting it from clay mines in the UK in the shape of ball-like bulges.
