Tags: Chemical Substance, Mineral.
Cordierite (mineralogy) or iolite (gemology) is a magnesium iron aluminium cyclosilicate. Iron is almost always present and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite with a series formula: (MgFe)2Al3(Si5AlO18) to (FeMg)2Al3(Si5AlO18). A high temperature polymorph exists indialite which is isostructural with beryl and has a random distribution of Al in the (SiAl)6O18 rings.
