Kaolin is a commercial term used to describe a claystone comprised mostly of kaolinite or related clay minerals, characterized by being white or nearly white, even when calcined. On the other hand, kaolinitic clay is a much more comprehensive term, as it is used to refer to rocks where clay minerals from the kaolinite group are a dominant portion, although upper and lower limits are no well-established, and therefore much broader ranges of concentration for kaolinite minerals are accepted in comparison with industrial grade kaolin. Kaolinitic clays are not necessarily white or nearly white, and may contain large amounts of other clay and non-clay minerals.