Gemstone | Form of Treatment | Frequency | Reason for Treatment |
Amethyst | Heating | Occasional | To lighten color and/or remove smokiness. |
Aquamarine | Heating | Routine | To remove yellow in order to produce a purer blue color. |
Beryl | Irradiation | Routine | To create blues and yellows from colorless stones. |
Diamond |
Laser Drilling Fracture Filling Irradiation HPHT Coating |
Occasional Occasional Routine Occasional Occasional |
To bleach out dark inclusions. Filled with chemicals sharing the same refractive index of diamonds. To make existing colors more intense or induce new colors. To change brown diamonds to whites, yellows, greens and some pinks.Can make all colors but primarily used to make pinks |
Emerald |
Oiling Impregnation |
Routine Occasional |
Colorless oil is used to penetrate into surface reaching fractures making them less noticeable. High-grade epoxy resins can be used to fill the surface reaching fractures to make them seem less noticeable. |
Jade |
Bleaching Impregnation Dyeing |
Occasional Occasional Occasional |
To remove any dark discoloration. With colorless wax, to improve appearance. To imitate natural colors. |
Opal |
Assembledproduct Impregnation |
Routine Routine |
Usually opal doublets can be made by combining via epoxy, a thin layer of opal backed by either chalcedony or boulder rock. Impregnated with colorless resins and hardeners. |
Pearl |
Bleaching Dyeing Irradiation |
Routine Routine Occasional |
To remove discoloration. To improve color. Certain pearls can be subjected to irradiation to permanently alter their color to gray, black or blue. |
Quartz | Heating | Routine | To improve color. |
Ruby |
Heating Cavity Filling Diffusion |
Routine Occasional Routine |
To intensify or lighten color. Surface cavities are filled with foreign material (sometimes glass). To produce an artificial star on a natural stone. |
Sapphire |
Heating Diffusion Irradiation |
Routine Routine Occasional |
To intensify or lighten color. To produce an artificial star on a natural stone. To obtain yellow or orange color from colorless stone. |
Tanzanite | Heating | Routine | To produce the violet-blue color for which the stone is known. |
Topaz |
Irradiation Heating |
Routine Routine |
To create blue, yellow and green topaz. To create pink or red topaz. |
Tourmaline |
Heating IrradiationCavity Filling |
Routine Occasional Occasional |
To improve intensity for blue-green colors. To intensify pink, purple and red colors; blue tourmaline can be irradiated to purple. Hardened colorless substances are often used to fill cavity. |
Zircon | Heating | Routine | Brown zircon is heated to make red, blue and white zircon. |