Beryllium diffusion is heating corundum with an added element, such as beryllium. The element diffuses into the crystal and changes its color.
In more detail
It appeared on the market in the early 2000s and can strongly change the color of ruby and sapphire. In many stones it is extremely difficult to detect with certainty. If the new color is shallow, recutting can remove it. The LMHC wording also covers what labs once called 'surface diffusion'.
On a grading report
Further information: indications of heating, color modified by (lattice) diffusion of a chemical element from an external source. Labs may add 'shallow' and name the element.
Related terms
- Heat treatment: Heat treatment is controlled heating of a gem to change its color or clarity.
- Treatment: A treatment is any process, other than cutting and polishing, that changes a gem's color or apparent clarity. Anyone who sells a treated gem must disclose the treatment.
- Padparadscha: Padparadscha is a sapphire of soft pinkish orange to orangey pink. Its tones are pastel and its saturation low to medium.
- Disclosure: Disclosure is telling the buyer, before the sale, that a gem is treated, laboratory-grown or an imitation.
- Sapphire: Sapphire is corundum of any color other than red. The word alone means a blue stone; other colors take a color word, such as yellow sapphire.