The fibrous structure generated by the layer-chain structure is one of the three main types of formation of natural mineral fibrous structures. The crystal structure of 2:1 type phyllosilicate consists of two [SiO 4] tetrahedral sheets (T sheet) and an octahedral sheet (O sheet). For most of these minerals, their layer structure is horizontal. This horizontal layer-structured can be achieved through appropriate adjustment of the tetrahedra. For example, the chemical formula of talc is Mg₃[Si₂O₅]₂(OH)₂. Its tetrahedra can be rotated by about 35° to match the octahedron sheet, thus keeping the layer structure horizontal (Fig. 1a). For pyrophyllite (Al₂[Si₂O₅]₂(OH)₂), since the smaller-radius Al 3+ in the octahedron replaces the larger Mg 2+, the tetrahedra must rotate by about 10° to maintain a horizontal layer structure (Putnis 1992).