What are the cobwebs in sapphire?
Diffusion treatments can be divided into surface diffusion and body diffusion
Surface diffusion: Chromogenic compounds are added at high temperatures to improve the color of the stone. However, the chromogenic elements (Fe and Ti) cannot diffuse deeply into the gemstone for color enhancement and are limited to the surface only, which can be removed by over-polishing.
Body Diffusion: Diffusion of light elements (Be) from the outside into corundum at high temperatures to improve the color of the stone. The small radius of the light element atoms results in deeper color penetration, sometimes through the entire stone.
Under the microscope, it was observed that the color was clustered at the prisms and there was no dichroism or banding, which led to suspicion of the color genesis of the sample. Instrumental tests to analyze the chromogenicity of the sample confirmed the theory that it was an Fe-Ti diffused sapphire.
The sample is very similar in appearance to the untreated sapphire, but the darker color and setting made it more difficult to observe. The laboratory has received a number of diffusion-treated sapphires, of which this sample is only one representative. It is hoped that consumers will be more vigilant in their purchases and should choose goods with authoritative laboratory certificates as far as possible to minimize unnecessary losses.