#4 Clay / Ball Clay
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-colored 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. They are commonly used in the construction of many ceramic articles, where their primary role, apart from their white color, is either to impart plasticity or to aid rheological stability during the shaping processes