Sapphire

Sapphire

Corundum in every colour other than red, with the classic blue produced by iron and titanium working together.

Overview

Sapphire shares its mineral species, corundum, with ruby. Blue sapphire owes its colour to charge transfer between iron and titanium, while other trace elements give rise to yellow, green, pink, purple and the rare pink-orange padparadscha.

Important deposits occur in metamorphic rocks, as in Sri Lanka, Kashmir and Madagascar, and in basaltic terrains such as Australia and Thailand. The two settings leave different chemical fingerprints, particularly in gallium, magnesium and iron content.

Because the great majority of sapphire on the market has been heated, and some has been diffusion treated with titanium or beryllium, our research pairs microscopy with spectroscopy to establish what has, and has not, been done to a stone.