Cordierite is a mineral that belongs to the group of cyclosilicates. It has the chemical formula (Mg,Fe)2Al4Si5O18. The mineral is named after the French geologist Pierre Cordier. Cordierite is commonly found in metamorphic rocks, such as schist and gneiss, and in some igneous rocks. It often occurs in association with other minerals like garnet, biotite, and sillimanite.

One notable characteristic of cordierite is its strong pleochroism, which means that it can exhibit different colors when viewed from different angles. Typically, it appears blue or violet-blue in one direction, colorless in another, and yellow or brown in the third direction.

Cordierite also has industrial applications. It is used as a refractory material, particularly in the production of kiln furniture (supports and structures in kilns), and as a pizza stone (both in conventional ovens and in high temperature pizza ovens) as it has a high resistance to thermal shock and can withstand high temperatures. Additionally, cordierite is utilized in the manufacturing of certain ceramics, including cookware and catalytic converters for automobiles.