Color Diamonds and Other Gemstone Treatments

Gemstone Treatments

Enhancements have been used for centuries, involving everything from coarsely dabbing the gemstone with dye to today’s more sophisticated methods like irradiation. Anyone who believes color-enhancing diamonds is unusual should consider the fact that many other gemstones regularly get treated one way or another to intensify color, diminish imperfections, or improve durability.

For instance, that beautiful deep purplish blue color many have come to associate with tanzanites is rarely these stones’ natural color. Though some natural blue tanzanites exist, the vast majority are brown or orange-brown when mined. Gentle heating gives these crystals more marketable colors.

Common treatments include bleaching, cavity filling, coating, diffusion, dyeing, fracture filling, heat treatment, irradiation, laser drilling, oiling and impregnation. As you can imagine, bleaching is used to lighten the color of a stone, cavity filling and fracture filling can disguise impurities, diffusion uses chemical agents to change the surface color of a stone, while dyeing, irradiation, oiling and impregnation are all used to change the color or lustre of a stone.

When considered from this perspective, the enhancement of diamonds is in no way unusual. The irradiation process is only designed to mimic nature, which makes it far more ‘natural’ than most of the alternative processes. Furthermore, while most gems are enhanced in order to hide flaws, diamond enhancement will only make flaws more obvious which means that it can only be carried out on the highest quality raw materials.

Find out what types of treatments are used today.

View a list of gemstones to find out which treatments are used to enhance each one.

Types Of Treatments

Here are the different types of treatments commonly used in the jewelry industry today:

Bleaching –

Color can be lightened or removed from a gemstone by using chemicals or other agents. Pearls are often bleached.

Cavity Filling –

The surface-reaching cavities, pits, or other depressions in the surface of a gemstone can be filled with glass, plastic, or other substances. The shallow surface-reaching cavities in corundum, usually ruby, are usually filled with glass-like substances.

Coating –

In order to add color or special effects to a gemstone, a thin layer of lacquer, enamel, ink, foil or film is coated on to the gem's surface. The gems most often coated are turquoise, quartz, topaz or opal and now diamonds.

Diffusion –

Chemical agents are used in the presence of heat to penetrate a shallow layer of the surface, become part of the crystal structure, and change the color or cause asterism. Sapphires and rubies can be diffusion-treated. Unlike coatings, the diffused substance is actually incorporated into the stone's structure.

Dyeing –

A gemstone's color can be changed or improved by using chemicals. Pearls, jade and turquoise are commonly dyed.

Fracture Filling –

Surface-reaching fractures, cleavages, laser drill holes and other voids can be filled with glass, plastic, or other substances to improve the gemstone’s clarity. The internal fractures of a diamond are filled with a transparent material that has the same refractive index as the diamond, thereby improving its clarity grade.

Heat Treatment –

Gemstones are subjected to high temperatures in order to lighten, darken, deepen, or even completely change their color. In certain gemstones heat treatment is also used to improve clarity. For example, heat treatment may be used to develop or improve colors such as blue or yellow in sapphires; to remove colors, like yellow, from aquamarines, or blue from rubies; to improve transparency by dissolving silk in sapphires or removing gas bubbles in amber; or to induce asterism, as in corundum. Heating is generally permanent, and heated stones do not require special care.

Irradiation –

This is used in gemstones like diamonds to affect only their color. Subatomic particles are used to bombard the electrons of the gem, causing them to be 'knocked' loose, and captured by other atoms. The light-absorbing pattern of the gems is thereby changed and as a result, so is their color. See Enhancement Process for details. This treatment is used to permanently create or intensify the gem's color. Diamonds, topazes and aquamarines are often irradiated to enhance their color.

Laser Drilling –

Laser Drilling - A laser is used to drill a hole in a diamond to reach a dark inclusion inside the stone. Chemicals are then inserted in order to bleach these black inclusions, thereby improving the appearance of the stone. The effects of the treatment are permanent and require no special care.

Oiling & Impregnation –

This involves the filling of surface-reaching fractures with oil (in oiling) or a plastic polymer substance (in impregnation) to make them appear less noticeable. Emeralds are routinely oiled and jadeite is commonly polymer-impregnated.

Table Of Gemstone Treatments

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.

Color Diamonds And Other Gemstone Treatments

Gemstone Treatments

Enhancements have been used for centuries, involving everything from coarsely dabbing the gemstone with dye to today’s more sophisticated methods like irradiation. Anyone who believes color-enhancing diamonds is unusual should consider the fact that many other gemstones regularly get treated one way or another to intensify color, diminish imperfections, or improve durability.

For instance, that beautiful deep purplish blue color many have come to associate with tanzanites is rarely these stones’ natural color. Though some natural blue tanzanites exist, the vast majority are brown or orange-brown when mined. Gentle heating gives these crystals more marketable colors.

Common treatments include bleaching, cavity filling, coating, diffusion, dyeing, fracture filling, heat treatment, irradiation, laser drilling, oiling and impregnation. As you can imagine, bleaching is used to lighten the color of a stone, cavity filling and fracture filling can disguise impurities, diffusion uses chemical agents to change the surface color of a stone, while dyeing, irradiation, oiling and impregnation are all used to change the color or lustre of a stone.

When considered from this perspective, the enhancement of diamonds is in no way unusual. The irradiation process is only designed to mimic nature, which makes it far more ‘natural’ than most of the alternative processes. Furthermore, while most gems are enhanced in order to hide flaws, diamond enhancement will only make flaws more obvious which means that it can only be carried out on the highest quality raw materials.

Find out what types of treatments are used today.

View a list of gemstones to find out which treatments are used to enhance each one.

Types Of Treatments

Here are the different types of treatments commonly used in the jewelry industry today:

Bleaching –

Color can be lightened or removed from a gemstone by using chemicals or other agents. Pearls are often bleached.

Dyeing –

A gemstone's color can be changed or improved by using chemicals. Pearls, jade and turquoise are commonly dyed.

Irradiation –

This is used in gemstones like diamonds to affect only their color. Subatomic particles are used to bombard the electrons of the gem, causing them to be 'knocked' loose, and captured by other atoms. The light-absorbing pattern of the gems is thereby changed and as a result, so is their color. See Enhancement Process for details. This treatment is used to permanently create or intensify the gem's color. Diamonds, topazes and aquamarines are often irradiated to enhance their color.

Cavity Filling –

The surface-reaching cavities, pits, or other depressions in the surface of a gemstone can be filled with glass, plastic, or other substances. The shallow surface-reaching cavities in corundum, usually ruby, are usually filled with glass-like substances.

Fracture Filling –

Surface-reaching fractures, cleavages, laser drill holes and other voids can be filled with glass, plastic, or other substances to improve the gemstone’s clarity. The internal fractures of a diamond are filled with a transparent material that has the same refractive index as the diamond, thereby improving its clarity grade.

Coating –

In order to add color or special effects to a gemstone, a thin layer of lacquer, enamel, ink, foil or film is coated on to the gem's surface. The gems most often coated are turquoise, quartz, topaz or opal and now diamonds.

Heat Treatment –

Gemstones are subjected to high temperatures in order to lighten, darken, deepen, or even completely change their color. In certain gemstones heat treatment is also used to improve clarity. For example, heat treatment may be used to develop or improve colors such as blue or yellow in sapphires; to remove colors, like yellow, from aquamarines, or blue from rubies; to improve transparency by dissolving silk in sapphires or removing gas bubbles in amber; or to induce asterism, as in corundum. Heating is generally permanent, and heated stones do not require special care.

Laser Drilling –

Laser Drilling - A laser is used to drill a hole in a diamond to reach a dark inclusion inside the stone. Chemicals are then inserted in order to bleach these black inclusions, thereby improving the appearance of the stone. The effects of the treatment are permanent and require no special care.

Diffusion –

Chemical agents are used in the presence of heat to penetrate a shallow layer of the surface, become part of the crystal structure, and change the color or cause asterism. Sapphires and rubies can be diffusion-treated. Unlike coatings, the diffused substance is actually incorporated into the stone's structure.

Oiling & Impregnation –

This involves the filling of surface-reaching fractures with oil (in oiling) or a plastic polymer substance (in impregnation) to make them appear less noticeable. Emeralds are routinely oiled and jadeite is commonly polymer-impregnated.

Table Of Gemstone Treatments

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.