What does cordierite mean?
Cordierite is a magnesium iron aluminium silicate mineral best known to scientists and collectors under its gemstone name, iolite. Found mainly in metamorphic rocks such as schists and gneisses, its most striking property is pronounced pleochroism: a single cut stone can shift from deep sapphire blue to pale yellow or gray depending on the angle from which it is viewed, a trait that historically earned it the nickname water sapphire. Beyond the jewelry trade, cordierite has an important industrial life. Because its crystal structure expands very little when heated, synthetic cordierite ceramics are ideal for applications exposed to sudden temperature swings, including the honeycomb substrates inside automobile catalytic converters and the shelves of pottery kilns. The mineral was named in honor of the French geologist Pierre Cordier, who described it in the early nineteenth century, and it remains a word encountered mostly in technical and gemmological contexts.
A magnesium iron aluminium cyclosilicate mineral occurring in metamorphic and some igneous rocks, strongly pleochroic and known in its transparent blue form as the gemstone iolite.
"Thin sections of the gneiss revealed porphyroblasts of cordierite surrounded by mica."
In gemmological contexts the blue transparent variety is usually called iolite rather than cordierite.
A low-thermal-expansion ceramic material with the cordierite crystal structure, widely used in catalytic converter substrates, kiln furniture, and other heat-resistant components.
"The exhaust system relies on a cordierite monolith to hold the precious-metal catalyst."
As a mass noun denoting the substance, cordierite is usually uncountable; the plural cordierites appears mainly when referring to distinct specimens, varieties, or occurrences of the mineral.
"The museum's collection includes cordierites from several famous localities."
Vikings are said to have used thin slices of this color-shifting gemstone — known as iolite — as a natural 'sunstone' to locate the sun through overcast skies while navigating at sea.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cordierite
Cordierite was named after the French geologist and mining engineer Pierre Louis Antoine Cordier, who first described the mineral in the early nineteenth century. The name follows the standard mineralogical convention of attaching the suffix -ite to a person's surname. Its transparent blue gem variety has long been marketed separately as iolite, a name derived from the Greek ion, meaning violet.
How cordierite is actually used
Cordierite is a technical term used chiefly in geology, mineralogy, and materials science; in the gem trade the transparent blue variety is more commonly called iolite, so general readers may not recognize the two names as referring to the same species. It carries no figurative or informal usage.
Easily confused with cordierite
Cordite is a smokeless explosive propellant made of nitroglycerine and guncotton, whereas cordierite is a silicate mineral used as a gemstone and in ceramics.