Pyrophyllite is a 2:1 dioctahedral phyllosilicate. Its unit formula is Al2Si4O10(OH)2. It has no layer charge due to the lack of atom proxying or isomorphous substitution, and only minimal edge charge. It has the simplest structure of any of the dioctahedral 2:1 phyllosilicates. Pyrophyllite crystals are constructed by oriented stacking of individual pyrophyllite layers to form thicker crystals. It has a monoclinic and triclinic crystal system.
Highlighting FeaturesPlanes of Si atoms Single silica tetrahedron Two silica tetrahedral layers Plane of Al atoms Single alumina octahedron One aluminum octahedral layer Single unit cell All atoms
Pyrophyllite has been used for carving ornaments and as tailor’s chalk.
Wardle, R., and G.W. Brindley. 1972. The crystal structures of pyrophyllite, 1Tc, and of its dehydroxylate. American Mineralogist. 57:732-750.