Gem treatments refer to any process or technique applied to a gemstone to alter its appearance, improve its color or clarity. These treatments have been used for centuries to enhance the beauty and market value of precious stones. As a professional gemmologist, it’s essential to understand the various gem treatments and their impact on precious stones. So what are the most common treatments?
Heat treatment
Heat treatment is one of the oldest and most common gemstone treatments. It involves subjecting a gemstone to controlled heat to improve its color, clarity, or both. Heat treatment can intensify the color of gemstones, eliminate or reduce inclusions and improve their overall appearance. This treatment is widely used for gemstones such as sapphires, rubies and tanzanites.
The process involves heating the gemstone to a specific temperature and holding it there for a certain length of time. The gemstone is then slowly cooled to stabilize the changes. Heat treatment is generally permanent and requires no special care. However, it is important to mention heat-treated gemstones when selling them to maintain transparency.
Irradiation
Irradiation involves exposing a gemstone to various forms of radiation to induce color changes. This treatment can enhance or modify the color of gemstones, creating bright, attractive hues. Irradiation is commonly used on gemstones such as topaz, diamonds and pearls.
There are two types of irradiation: natural and artificial. Natural irradiation occurs when gemstones are exposed to radiation from natural sources, such as the earth’s crust. Artificial irradiation involves the use of controlled radiation in the laboratory. Both types can produce magnificent color transformations.
It is important to note that some irradiated gemstones may fade or change color when exposed to prolonged sunlight or high temperatures. It is therefore advisable to store these gems away from direct sunlight and avoid exposing them to extreme heat.
Broadcast
Diffusion treatment involves applying chemicals or heat to the surface of a gemstone to enhance its color or create decorative patterns. This treatment allows the color to penetrate the surface of the gemstone, giving it a deeper, more intense appearance. It is commonly used on gemstones such as sapphire and corundum.
The diffusion process may involve the use of chemicals such as titanium or beryllium, which react with the gemstone’s crystalline structure to produce color effects. This treatment is generally permanent, but it is important to note that diffusion-treated gemstones may require special care when cleaning or repairing, as certain chemicals can affect the color or stability of the stone.
Filling
Filling is a treatment used to enhance the appearance of certain gemstones by filling their fractures or cavities with transparent or colored substances. This treatment is commonly used on gemstones such as emerald, opal and turquoise.
Filling can improve the clarity and brilliance of the gemstone by reducing the appearance of inclusions or enhancing the color. However, it is important to note that filling may be temporary and may require special care to avoid damaging or removing the filling material.
Surface coating
Surface coating, also known as plating, involves applying a thin layer of color or material to the surface of a gemstone to enhance its appearance. This treatment is commonly used to create iridescent effects, color play or to imitate the appearance of more precious gemstones.
A popular surface coating technique is known as “mystic” treatment, where a thin metallic layer is deposited on the surface of a gemstone to create a rainbow effect. Another technique is to apply a thin layer of synthetic spinel or other colored materials to simulate the appearance of a specific gemstone.
Surface coatings are generally not permanent and can wear over time, especially with prolonged wear or exposure to chemicals. It is important to mention surface-coated gemstones when selling them, and to take extra care when cleaning to avoid damaging or removing the coating.
Bleaching and dyeing
Bleaching and dyeing are treatments used to improve or modify the color of certain gemstones. Bleaching is the use of chemicals or other agents to remove or lighten the color of a gemstone. This treatment is commonly used on pearls, coral and certain lighter-colored gemstones.
Tinting, on the other hand, involves introducing colored substances into the pores or fractures of a gemstone to enhance or change its color. This treatment is commonly used on gemstones such as agate and jade.
It is important to note that bleached or tinted gemstones may require special care to preserve their appearance and stability. They can be sensitive to scratches, excessive heat or exposure to certain chemicals, so it’s advisable to protect them and clean them with care.
More doubts?
Gem treatments are techniques commonly used in the jewelry industry to enhance the appearance and value of precious stones. It is important to understand these treatments and their impact on gemstones before buying or selling jewelry. When buying a gemstone, it is advisable to ask for a certificate of authenticity, which indicates whether the stone has been treated and what type of treatment has been applied. This guarantees transparency and precise knowledge of the gemstone you are buying.
If you have any doubts or questions about gem treatments, it’s best to consult a professional gemmologist, who will be able to provide you with personalized advice and detailed information on the various gemstones and their treatments.
Lauréline Colliard FGA
FGA Gemmologist, graduate of London's prestigious Gem-A Academy (and former lead 3D animator in the video game industry). Her focus is on research, the ethics of gemstones and their environmental and social impact, and the protection and education of gemstone buyers and enthusiasts.
