Cordierite

Cordierite, called iolite in gemology, is a magnesium iron aluminium cyclosilicate in which iron is almost always present, and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite. It was discovered in 1813 in specimens from Nijar, Almeria, Spain, and is named after the French geologist Louis Cordier. It typically occurs in contact or regional metamorphism of pelitic rocks and is especially common in hornfels, and it is synthesized for high-temperature uses such as catalytic converters and pizza stones. In this atlas it is the mineral species behind the gemstone iolite.