Diamonds are currently grown as yellow, blue or white, and these colors are our primary focus. On a rare occasion, we have created experimental as-grown light green diamonds, where the color comes from a little boron (blue) and a little nitrogen (yellow). Other colors are achievable by using post-growth treatment of as-grown yellows, normally through irradiation.
Pink, Green, Purple and Other Colors
Irradiation
Irradiation is a safe process where a diamond is bombarded, normally with neutrons or electrons, which alters the diamond’s crystal lattice. This alteration creates new color centers, modifying the as-grown color of the diamond. Irradiated diamonds are normally annealed, or heated, to further achieve the appropriate color. This annealing process corrects some of the alterations from irradiation, creating new colors in the process.
Despite sounding menacing, there is no radiation in an irradiated diamond and is perfectly safe to wear.
This process uses as-grown yellow diamonds to create mainly pink, purple, red and green colors.
Successful Candidates
The post-growth treatment process is most successful with smaller, low saturation yellows. The more saturation in the as-grown color (intense and vivid colors), the higher the saturation and darker the tone will be in the output color. For example, fancy intense yellows intended for pink normally come out a fancy vivid or deep pink or purple color.
The weight of the stone also affects the resulting color. The “thicker” the diamond, the greater the chance the center many not be fully treated. Most stones under 1/2 carat are fully treated. The lighter the tone and saturation, the easier it is to fully treat the stone. However, a one carat yellow intended for pink may turn a peachy color, as the center may have some yellow color remaining, adding to the surrounding pink colors.
We have successfully irradiated green diamonds up to one carat, and vivid or lighter pink diamonds up to 1/2ct.
Stability
The treated colors are permanent and stable under day-to-day wear. Care should be taken when servicing a color treated diamond, as they may be exposed to high temperatures (>800°C), such as a jeweler’s torch. These extreme temperatures may cause the colors to become unstable. Most jewelers can safely and securely “cold set” the diamond, without applying heat.
All of the as-grown colors (blue, yellow, white) are stable and permanent under all conditions, including when setting into jewelry with a torch.