Mg₂Al₄Si₅O₁₈

These samples of cordierite are displayed in the Smithsonian Museum of Natural History. Cordierite is a silicate mineral with the composition Mg₂Al₄Si₅O₁₈. The sample at left is about 8 cm across and is from Kragero, Telemark, Norway.

These cordierite gems have sizes 10.2, 15.5 nd 9.5 carats. They are from Sri Lanka.