Halloysite and Kaolinite | Clays and Minerals
Definition: The most important members of the kaolin sub group of minerals are kaolinite and halloysite. Kaolinite has the formula Al 2 Si 2 O 5 (OH) 4 and typically occurs in platy forms. Halloysite has a similar composition except that it contains additional water molecules between the layers and most commonly has a tubular morphology.