corundum, color.4, inclusions.5, treatments.6, synthetic corundum.7, gems

Some minerals, such as rutile, hematite and ilmenite, found as inclusions in sapphires are capable of imparting body—colour to their host during high temperature heat treatment. The inclusions are cannibalized by the host sapphire for the chromophoric elements they contain. If the inclusions are not completely consumed by their host this ‘internal diffusion’ results in a zone of intensely coloured sapphire surrounding the remaining inclusions.