Ball Clay

diagram illustrating the formation of ball clays

Al2O3×2SiO2×2H2O —Secondary clays deposited in marshy areas. Very fine particle size, high plasticity, high in organic contaminates, and fires white or off-white. Used as the primary plasticizing clay in most clay bodies, but in large quantities promotes high shrinkage.  

Learn more about ball clays in this helpful post!

Source: Clay: A Studio Handbook