Feature Gems & Gemology, Fall 1986, Vol. 22, No. 3

Carbon Dioxide Fluid Inclusions as Proof of Natural-Colored Corundum

The question of how to identify natural-colored from heat-treated corundum has long puzzled the gemological community. One important clue is now provided by carbon dioxide fluid inclusions. Because such inclusions cannot survive heat treatment, their existence intact and unruptured in rubies and sapphires is conclusive proof that no heat treatment has occurred.