Treatments for Changing the Color of Gemstones that are Common Foil backings are the oldest way for enhancing the colour of jewels. Modern tactics, unfortunately, are far more subtle and harder to detect.
Coatings and Dyes
Coating the back of the opal with a black material can increase the colour. Diamonds are occasionally "painted" with a pale-coloured dye to counteract a yellowish hue. The coating, however, quickly fades off.
Quartz can be coloured or stained to seem like jade or tourmaline. Because chalcedony is porous, it rapidly absorbs dyes, resulting in a wide range of vibrantly coloured stones. By soaking greyish-coloured chalcedony in a sugar solution and then blackening it in sulfuric acid, "black onyx" is created. This Gemstone treatment leaves very few carbon particles in the chalcedony's pore spaces.
Turquoise can be enhanced in a variety of ways. "Stabilization" refers to Gemstone treatment like soaking in wax (paraffin) or impregnating with polymers. Although such tactics are usually detectable, suspect them if a deep-colour turquoise is offered at a low price.
Greyish jadeite can be stained to make it look "Imperial" or coloured a deep mauve colour. Although natural mauve jadeite exists, the coloured material is much darker. Serpentine, a non-jade material, can also be stained with a rich, green stain to give it the appearance of Imperial jade.
Coral can be dyed to make it a more appealing (usually red) colour. Black coral can also be bleached to create a "golden" substance.
Blue lapis lazuli is often tinted or "touched up" with coloured solutions.
Dyes and Coatings Detection
Because dyes tend to cluster along fine cracks and fractures, they are often easy to spot. Under magnification, these dark lines can be seen. Scratched surface coatings (wax, polymers) are common. Raman spectrometers, for example, provide a high-tech option for detecting impregnations and layers. Simple tests, such as using a cotton swab to apply solvents (alcohol, acetone) and checking if any colour comes off, can sometimes rapidly and effectively reveal dye treatments.
Irradiation and heating
This Gemstone treatment has unpredictably unpredictable effects on jewels. However, they can also improve the colour of gems in some situations.
Heating is a time-honoured and extensively utilized Gemstone treatment for enhancing gemstone colour. The trade considers it acceptable with transparency. On the other hand, diffusion is difficult to detect and provides unscrupulous sellers with an opportunity to perpetrate fraud by withholding information about the procedure. Furthermore, this artificial enhancing Gemstone treatment frequently alters the appearance of a gemstone dramatically. As a result, it is not regarded as "harmless" in the same way as heating is.
On an atomic level, the diffusion process permits chemical contaminants to penetrate the structure of gem material. These imperfections disrupt the material's structure and alter how it absorbs light, resulting in colour. "Color centres" refer to the atomically disordered places.
Colour centres are found in all types of mineral crystals and are the source of colouration in most transparent gemstones. However, laboratory experiments have shown chemical techniques that allow the forced introduction of impurities into various gem materials, resulting in artificial colour centres and colours in these stones.
Mineral diffusion rates are exceedingly low unless done out at extremely high temperatures, which will harm or kill the majority of jewels. Minerals like corundum (sapphire) and feldspar, which crystallize from a melt in nature, are exceptions. As a result, they might attain high temperatures during treatment, approaching their melting point.
Gemstone Treatment using Beryllium
The migration of the element beryllium into sapphire is the most well-studied gemstone diffusion treatment. As a result, the material takes on a new colour, usually orange, blue, yellow, or red. The altered colour zone can be seen as a surface layer on huge stones through immersion in a refraction liquid. However, little stones of BerylliumBeryllium can permeate the entire body, leaving no obvious colour zones.
Spectrometers and other modern instruments are now frequently used to identify Beryllium treatments. But, unfortunately, most merchants in the jewellery market do not employ this technology.
Clarity Gemstone treatment
Many gem materials have microscopic (or larger) cracks and fissures that reach the cut stone's surface. These cracks are apparent because of the considerable contrast in the refractive characteristics of air and the host material. However, when filled with a substance (such as oil, wax, epoxy, etc.) that nearly matches the refractive index of the surrounding matrix, the fissures "disappear."
Emeralds are by far the most well-known example of a gemstone that has undergone this treatment. The trade has politely and euphemistically dubbed these jewels Jardin because they nearly invariably have a maze of internal flaws (French for the garden). When an emerald is heated after being soaked in green-dyed oil, the oil penetrates the stone and fills the fissures, thus "clarifying" it and increasing transparency and brilliance.
For millennia, emeralds have been oiled, usually directly at the source. The oil eventually evaporates and escapes, restoring the stone to its original, plainly defective state. It can, however, be re-oiled regularly. Epoxy and polymer fillers provide a more lasting solution. This Gemstone treatment can usually be detected by careful testing.
Various "fillers" are used to improve the purity of many other gems. For example, dark-coloured inclusions in diamonds are frequently "burned away" with lasers. Because the powerful light beam makes a minuscule "tunnel" through the diamond, you can immediately notice this laser clarity treatment. (Some diamond laser treatments result in tunnels that are more difficult to see.) To find them, you'll need a microscope).