Several clays in commercial use consist largely of kaolinite, a hydrated aluminum silicate. Large deposits of this mineral occur in China; Czechoslovakia; Cornwall, England; and several states of the United States. Various grades of kaolin clays may be distinguished. White kaolin clays are fine in particle size, soft, nonabrasive, and chemically inert over a wide pH range. Their largest consumer is the paper industry, which uses them as a coating to make paper smoother, whiter, and more printable, and as a filler to enhance opacity and ink receptivity. Ball clays are usually much darker because they contain more organic carbonaceous material. These fine grained refractory bond clays have excellent plasticity and strength, and they fire to a light cream to white color. For these reasons, ball clays are used in ceramics.