Clay minerals are the main mineral components of clay rock and soil. They are hydrous aluminium and magnesium phyllosilicates. When mixed with water, clay minerals have various degrees of plasticity. Clay minerals are usually ultrafine-grained, normally less than 0.01 mm. They have a layered structure, and only a few, such as sepiolite and palygorskite, have chain-like structures. Clay mineral families include the kaolinite, illite, montmorillonite, vermiculite and sepiolite families. Clay minerals are mainly used to make ceramics and fire-resistant materials. They are also used in the petroleum, construction, textile, paper-making and paint-making sectors.