Ball Clay is a variety of Kaolinite, like china-clay. It differs from china-clay in having high plasticity and less refractoriness. In chemical composition, ball and china clays do not differ greatly except that the former contains a larger proportion of silica. It has derived its name from the practice of removing it in the form of ball-like lumps from the clay pits in the UK. Ball clays are kaolinitic sedimentary clays that commonly consist of 20-80% kaolinite, 10-25% mica, 6-65% quartz. Localized seams in the same deposit have variations in composition, including the quantity of the major minerals, accessory minerals and carbonaceous materials such as lignite. They are fine-grained and plastic in nature, and, unlike most earthenware clays, produce a fine quality white-coloured pottery body when fired, which is the key to their popularity with potters. Ball clays are relatively scarce deposits due to the combination of geological factors needed for their formation and preservation.
