Kaolin is referring to a group of clay minerals, such as kaolinite, Al2Si2O5(OH)4, derived from the alteration of aluminum silicate minerals, such as feldspars and mica.
It is used in medicine to treat digestive upsets, and in poultices.
Kaolinite is economically important in the ceramic and paper industries. The places where it is mostly found are the United Kingdon, the USA, and some countries in Europe and Asia.