GEMSTONE TREATMENTS & ENHANCEMENTS
While many gemstones used in high-end jewelry designs are formed naturally in the earth’s crust, some of these have undergone treatments to improve their appearance. Jewelry professionals also use gemstone treatments to improve durability, color, and clarity.
Standard gemstone enhancements include heat treatment, fracture filling, irradiation, waxing, dyeing, bleaching, diffusion treatment, polishing, and cutting with the help of gem cutters.
Common Gemstone Enhancements
Dyeing is a treatment technique that involves applying a coloring agent to the surface of a gemstone. The surface of the gem material must be porous or fractured for the dye to permeate it. Chalcedony is one of the many gems often treated using this method. Lower-grade lapis lazuli, with lots of white calcite, is another gem dyed to achieve its desired royal or pale blue color.
Bleaching is one of many gem treatments that use chemicals or other methods (such as strong light elements) to lighten a gemstone’s color, improve its clarity, or fade dark spots. Jade and pearls are among the many gems often bleached to enhance their appearance. What is interesting about this treatment, though, is that it is virtually undetectable, even to a trained eye. So, gem crystals that have been bleached often appear to have been found or mined that way, even though this is not actually the case.
Coating a gem involves the application of lacquer or some other type of coloring agent to its surface, which is done to improve its coloration and appearance.
Fractures occur naturally in gemstones, but surface-reaching fractures can often lower the value of a gem. Thus, fracture filling is another of the many gemstone treatments used to improve the appearance and overall quality of gem materials. The filling materials used in this type of treatment include leaded glass, plastic, resin, wax, and oil. By filling the cavities in the gem’s surface with one of these materials, the visibility of the imperfections is reduced. In some cases, fracture filling also adds a slight amount of weight to the gemstone. In others, fracture filling is used for clarity enhancement. For example, oil is used to fill fissures in emeralds to improve their apparent clarity (a treated emerald is sometimes called an “oiled” emerald). Fancy color diamonds and rubies are also often treated for surface-reaching fractures using this gemstone enhancement technique.
The most common method used for gemstone color and clarity enhancement is heat treatment. Heat treatment involves using high temperatures to lighten, darken, or even change the natural color of a gemstone to improve its overall appearance. These color changes are permanent, and the treatment is often performed on gemstones such as aquamarine, topaz, ruby, and sapphire. Heat treatment can also sometimes improve the clarity of a gemstone. For example, heating aquamarine can eliminate the yellow component or green color, resulting in a bluer gem. In the same way, using heat treatment on a blue sapphire will result in a deep blue color while also removing some of the minute inclusions (imperfections) that are naturally present in this particular gemstone.
Diffusion treatment is used to alter or accentuate the appearance of pale or colorless gems. The process usually involves applying chemicals to the surface of such stones in combination with heat treatment. The combination of these two gemstone enhancement methods allows the chemicals on the surface to travel into the crystal structure of the gemstone, introducing a color that was previously not there. Ruby and sapphire are commonly treated with diffusion but bear in mind that while the value of the treated stones is usually much less than the naturally colorful ones, this doesn’t make them any less genuine. Diffusion treatment may also sometimes only penetrate the outermost surface of gem materials. In this case, the original color may be exposed if the gemstone is chipped or scratched.
Irradiation is a gem treatment technique that exposes a gemstone to artificial radiation for color enhancement purposes. Irradiation is sometimes followed by heat treatment to permanently alter the gem coloring, as in the case of natural blue topaz. Virtually all blue topaz on the market has been subject to irradiation to turn the color of the raw stone from white to blue. Other gems often subjected to radiation treatment besides blue topaz include colored diamonds, smoky quartz, kunzites, tourmalines, and cultured pearls. Except for irradiated blue topaz, irradiated gems are usually quite difficult to detect. So much so that only the sophisticated equipment of the gem laboratories at a gemological institute can identify irradiated gem materials.
Frequently Asked Questions
A filled gemstone refers to one that has undergone treatment to reduce the appearance of surface-reaching fractures or inclusions, improve durability, and for clarity enhancement. The process involves filling the cavities in the gemstone with leaded glass, oil, wax, or resin. There is quite a lot of debate surrounding this practice, with purists believing that resin should not be used because it devalues the finished gem.
Naturally-enhanced rubies have undergone heat treatment to try and improve their appearance. However, they are still rubies, although there is some debate regarding whether they should still be considered natural because heating enhances the gemstone’s color and shine.
Thermal enhancement is a gemstone treatment technique that involves applying heat to gemstones like rubies and blue sapphires to improve their color and clarity. Thus, the minerals are changed from their natural rough state for use in fine jewelry.
A treated stone is still a genuine gemstone, but it has been enhanced via jewelry repair procedures to improve its appearance and increase its value. Common treatments include high-temperature heat treatment, coating the surface of the stone, dyeing, and irradiation. Gemstones can also be subject to combination treatments to improve their clarity.
Stones you can wear daily without worrying too much about damaging them are diamonds, colorless topaz, yellow beryl, ruby, and sapphire. Other gems that you need to be more careful with due to their lack of hardness, durability, and wearability are pearls, opals, jades, aquamarines, onyx, and green quartz.
The vast majority of natural gemstones have been subjected to some kind of treatment, such as heat, radiation, or diffusion. These gemstone enhancements are usually done to alter the stone’s color to the one the gem trade desires or increase its apparent clarity. Sometimes it involves a combination of common treatments to achieve the desired result. Besides having an improved appearance, the price for an enhanced gemstone is also not as high as an untreated natural gem.
Common heat-treated gemstones include amber, aquamarine, tanzanite, amethyst, citrine, topaz (resulting in blue topaz), zircon (resulting in blue zircon), tourmaline, rubies, and sapphires. High-Temperature Heat Treatment (HPHT) processes are also often applied to diamonds with a brownish tint, transforming them into the colorless diamonds most people associate with fine jewelry. This type of heat treatment can even turn some diamonds blue, orange, or yellow.
Most colored gemstones are formed naturally below the earth’s surface, but some have also been grown in gem labs. The latter are known as lab-grown or synthetic gems. Naturally-occurring gemstones, however, are brought to the surface through mining and other naturally occurring earth processes, such as faulting, folding, uplifts, and volcanic activity.
The most common heat-treated gems include amber, ruby, sapphire, amethyst, tourmaline, aquamarine, citrine, tanzanite, and topaz. However, there are also many types of irradiated gemstones.
All gem materials found by humans have been treated to some extent. This is because the raw stones are cut and polished when prepared for use in jewelry. However, gems that are not treated in the sense of the techniques mentioned above include spinel (in a range of colors), orange spessartite, rhodolite garnet (known for its natural pink color), and peridot.
Gemstone treatments that use heat are not “bad” in the sense that they reduce the quality of the gemstone. On the contrary, heat treatment can actually increase and improve the durability of colored gemstones.
If you study the surface coating and notice parts where the color is highly concentrated, then it is likely that the stone has been dyed. Unfortunately, dyed crystals lose their overall value.
A sapphire that has been exposed to heat treatments is considered acceptable by the jewelry industry or gem trade. However, a sapphire that has no evidence of heat treatment tends to have a higher value.
Laser drilling is one of many gemstone enhancements that increase a diamond’s clarity. The process involves drilling tiny holes on the diamond’ surface, usually thinner than a hair. The primary reason for laser drilling a diamond is to remove black spots.