Palygorskite

Palygorskite or attapulgite is a magnesium aluminium phyllosilicate with the chemical formula (Mg,Al)2Si4O10(OH)·4(H2O) that occurs in a type of clay soil common to the Southeastern United States. It is one of the types of fuller's earth and commonly occurs as a fibrous clay mineral. Some smaller deposits of this mineral can be found in Mexico, where its use is tied to the manufacture of Maya blue in pre-Columbian times. Unlike layered phyllosilicates such as smectites, palygorskite has a chain-like crystal structure (ribbons) consisting of continuous tetrahedral silica chains linked to octahedral sheets of magnesium and aluminum, each ribbon being linked to the next by inversion of SiO4 tetrahedra along a set of Si-O-Si bonds. This structural feature contributes to many of its peculiar physicochemical properties.