Glossary term
Diffusion treatment
A treatment that introduces colouring elements into a gem’s surface at high temperature.
Lattice diffusion introduces elements such as titanium or beryllium into a gemstone at high temperature to change its colour. Depending on the element, the colour layer may be shallow or penetrate deeply. Diffusion-treated stones are worth much less than comparably coloured untreated or simply heated stones and require laboratory identification.