Chemical Formula: (Mg,Fe)2Al3(AlSi5O18) Locality: Bodenmais, Germany. Name Origin: From the French mining engineer and geologist P. L. A. Cordier (1777-1861). 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: (Mg,Fe)2Al3(Si5AlO18) to (Fe,Mg)2Al3(Si5AlO18). A … Continue reading Cordierite