Beryllium treatment is a recent addition to techniques for treating gemstones. Beryllium treatment is a form of heat treatment, mainly for sapphire, that adds the element beryllium to the heating process. Beryllium is an element well known in the gem world, since it is an essential constituent in many gemstones, including emerald, beryl, aquamarine and chrysoberyl. When sapphires are heated with beryllium, the result is a reduction in blue tones. Thus bright yellow or orange sapphire can be produced from weak yellow or greenish gems. Some stunning colors have been produced using this method.

This method is sometimes known as lattice diffusion. However, unlike some older forms of diffusion treatment, with beryllium diffusion the new color is deep within the stone; and these stones can be recut if needed. This is unlike the older diffusion treatment process, which only colors the surface of the stone. After some initial controversy, beryllium treatment is now widely accepted in the gem business as a legitimate method for treating stones. However, it is very important that gems treated with this method be disclosed as such. The most common terms are "Beryllium treated" or "Be treated" ("Be" is the symbol for the chemical element beryllium).