Decades ago scientists realised that they could synthesise diamonds and colored gemstones in laboratories. The specimens resulting from these laboratory processes were flawless and had the most enrapturing appearances. They were virtually indistinguishable from the highest quality stones but lacked one significant factor that makes gemstones valuable - their rarity.
At Precious Earth, we believe that anything that nature makes on its own isn’t bound by the limitations of ‘perfection’, and that in itself is what makes it unique. Natural gemstones are no exception to this, but are there ways to make them better suit our use? Keep reading to find out.
What Does the Treatment of Gemstones Entail?
Gemstones are formed deep within the earth’s crust under extreme heat and pressure conditions, over millions of years. While virtually flawless specimens are occasionally found, most natural gemstones contain some kind of imperfection such as inclusions, blemishes, cracks, fissures, discolourations, and gaps. Procedures that address a gemstone’s imperfections, enhance its aesthetics, or improve its durability are called treatments.
Treatments can make a gemstone suitable for a purpose it wouldn’t have otherwise fulfilled, such as a stone with a major fracture that may not be perceptible to the eye but cannot be used in jewelry as it may be prone to breakage. Some procedures can also be used to enhance the colour of a gemstone - making its hues more saturated and scintillating, to create a truly breath-taking specimen. At the same time, some treatments enhance the clarity and transparency of a stone but may make the gemstone more brittle and prone to breakage.
While some treatments are minor and temporary, others have a permanent effect on a gemstone’s appearance and structure. Understanding the different types of treatments, and how they affect a gemstone can help you make a more informed decision whilst making a purchase.
Does Treatment Affect the Value of a Natural Gemstone?
An uncut and unpolished gemstone is of value only to a gemologist or a lapidary. Similarly, treatments are not just a way to improve a gemstone’s appearance but also make its beauty accessible to everyone who sees it.
Because these treatments and enhancements are usually imperceptible to unpractised eyes – and sometimes even difficult for experts to detect - not disclosing the particular treatment that a gemstone has undergone can cause a buyer to believe that it is naturally of higher quality and therefore more valuable. Untreated gemstones of similar appearance as enhanced gemstones cost significantly more, and as such, it is important for sellers to disclose these enhancements, to the best extent of their knowledge.
What Are the Different Types of Gemstone Treatments?
Different types of gemstones may be treated or enhanced in different ways, and not all treatments have the same effect on the gemstone. It's important to be aware of these treatments when purchasing a gemstone, as they can affect the value and durability of the stone. The following is a non-exhaustive list of common gemstone treatments.
1. Oiling
Oiling is among the oldest gemstone treatments. It involves filling the surface cracks and fissures of a gemstone with colourless oils, resin, or wax, to improve the gemstone’s colours and transparency by making surface fractures, pores, and cracks less visible.
Oiling is commonly done to emeralds, but can sometimes also be done to semi-precious gemstones like opal, peridot, and turquoise. It is a minor and temporary treatment and does not affect the structural integrity of the gemstone. Oiling can make existing surface fractures harder to detect, and therefore the gemstone may require magnified inspection before purchasing.
Figure 1: An Emerald before & after oil diffusion (Source: GGTL Labs)
2. Surface Coating
Surface coating involves applying a thin coating formula to the surface of a gemstone to enhance its colour, lustre, or scintillation. These coatings are designed individually for different gem species and do not permeate the surface of the stone. Some coating formulas can improve surface wear resistance, and others may also be applied to the back surface or girdle of a gemstone to improve its appearance when viewed from the top - such as when they are set in jewelry pieces.
Coating is a minor and common treatment, usually used for diamonds, tanzanites, lapis, topaz, pearls, and quartz. Usually, coloured coatings can be easily spotted by seasoned gemologists, but colourless coatings, which are used to enhance durability, may be harder to detect.
Figure 2: The intense pink colour of these diamonds is the result of a surface coating (Source: GIA)
3. Lead-Glass Filling Treatment
Lead-glass or silica-glass filling is a common treatment for small inclusions in gemstones. These are used to fill cavities in the gemstone and improve their clarity. The treatment can enhance the clarity of low-quality and translucent gemstones and is commonly used for rubies of inferior quality.
Glass-filled gemstones are stable at high temperatures but are susceptible to household chemicals and cleaners. This treatment can be easily detected by a skilled gemologist using an eyeglass. While the treatment enhances the scintillation of a gemstone, it is detrimental to its structural integrity.
Figure 3: A Ruby before (left) and after (right) lead-glass filling (Source: First State Auctions)
4. Thermal Enhancement
Thermal enhancement or heat treatment is among the oldest and most common treatments, in which gemstones are exposed to high temperatures to enhance their colour or clarity. The traditional blow-pipe method of heating, which dates back thousands of years, is still used across the world. Modern methods that use ovens and furnaces have also been developed, and offer better control over temperatures.
In colored gemstones like topaz, tourmaline, and tanzanite, heat treatment can completely alter the colour. In rubies and sapphires, it can cause the recrystallization of silk inclusions (read more about silk inclusions here) leading to an overall improvement of the gemstone’s clarity, scintillation, and colour. Similar to rubies and sapphires (both part of the corundum mineral group), thermal treatment is also used to enhance the clarity of an amethyst gemstone to make it fit for use in jewelry.
Heat treatment can completely alter a gemstone’s colour. While an amethyst’s natural colour can range from a light lilac hue to deep overtones of purple, it is heat-treated to produce its signature astonishing hues and achieve its famed royal purple colour. Prolonged heating at temperatures between 400°C - 500°C will turn an amethyst into a citrine with a deep orange colour. Natural citrines can have a golden-yellow or brownish and orange colour. Most of the citrines in the market are actually heated amethysts. On the other hand, except for the rare demantoid garnet, garnet gemstones are mostly unaffected by heat treatment.
Thermal treatment is not easy to detect even though most gemstones available in the market today are thermally enhanced. The treatment is usually permanent and stable, but some zircon gemstones, which are heat-treated to achieve a lighter appearance, have been known to revert to their original colour upon prolonged exposure to light. Heat can also affect the colour of some treated zircons. Thermal treatment is usually not detrimental to the longevity of the gemstone, but it cannot be performed on gemstones with abundant liquid inclusions.
Figure 4: A natural blue sapphire before (left) and after (right) thermal enhancement (Source: GIT Thailand)
5. Lattice Diffusion Treatment
The colour of most gemstones comes from the presence of trace elements (such as iron or chromium) in the crystals’ structures. Lattice diffusion involves the penetration of such trace elements into the atomic structures of the gemstones during heat treatment to enhance or alter their colour.
This treatment is usually done for rubies, sapphires, and feldspar. It is a permanent treatment that does not affect the gemstone’s durability. Though it is detectable only in advanced gem testing laboratories, lattice-diffused gemstones are safe to purchase.
Figure 5: Sapphires at various levels of lattice diffusion - from untreated (left-most) to successful titanium diffusion (right-most) (Source: GIA)
6. Beryllium Heating
Beryllium heating is a modification of lattice diffusion treatment. It involves using heat to introduce the element Beryllium into the structure of the gemstone, which results in the reduction of the gemstone’s blue colour tones. The treatment is usually used for blue and yellow sapphires and can be used to produce stunning sapphires with highly saturated colours.
Beryllium heating causes the new colour to penetrate deep into the gemstone; sapphires with pale yellow, brown, and green hues can be treated to become vivid yellow or orange, and dark opaque blue sapphires can be lightened to a cornflower blue. It is a permanent and stable treatment that does not affect the integrity of the gemstone and is safe for use in jewelry as well as in astrology.
Figure 6: A Pink Sapphire from Madagascar (left) changes colour to Orange (right) after BE Diffusion (Source: GIA)
Figure 7: A group of rough sapphires before (left) & after (right) BE Diffusion (Source: GIA)
7. Fracture-Filling Treatment
This gemstone treatment involves filling surface-reaching fractures or cavities with colourless materials like lead glass, epoxy, wax, or oil to conceal them and enhance the clarity of the gemstone. This treatment can add to the weight of a gemstone. It is usually done to gemstones like topaz, tourmaline, peridots, aquamarine, garnets, and quartz, as well as diamonds and emeralds. Fracture-filling is one of the few treatments done to garnets because of their naturally high clarity and wide range of colours.
The durability of this treatment depends on the filler, as significant changes in air pressure and temperature, or exposure to chemicals can affect the appearance of filled gems by altering or even removing the filler substance. Filled gemstones are easily recognized by skilled gemologists using an eyeglass, and are safe to purchase as long as the treatment is disclosed to the consumer.
Figure 8: An Emerald with surface-reaching fractures (left) filled with oil and resin (right) (Source: GIA)
8. Irradiation Treatment
Irradiation treatment is an advanced method utilised to transform the appearance of gemstones by utilising radiation, resulting in distinctive and unconventional hues. Often, this process is complemented by heat treatment to further refine the colours. It's commonly applied to diamonds, topaz, tourmaline, and quartz.
Identifying whether a gemstone has undergone irradiation typically needs sophisticated testing, except for blue topaz, which is always treated because naturally occurring blue topaz is quite rare. Aquamarines frequently undergo irradiation treatment to eliminate any greenish tint from their blue colouration.
While irradiated blue topaz, diamond, and quartz typically maintain stable colours, certain gemstones like tourmaline and aquamarine may experience fading of their enhanced hues upon prolonged exposure to heat or intense light. Notably, garnets remain unaffected by irradiation, and this treatment doesn't compromise the durability of the gemstone.
Figure 9: Colourless & other diamonds (left) can be artificially irradiated causing a variety of colours. Some of the irradiated colours are then heated as a 2nd step, resulting in additional colours (group right) (Source: GIA)
9. Laser Treatment
Although generally uncommon, laser treatment involves using a laser to burn minute channels into a stone, followed by forcing chemicals into the channel to dissolve certain inclusions. The treatment is primarily done for diamonds and can be easily detected by a skilled gemologist. Although the lasers change the diamond’s structure, most holes are microscopic and do not affect its durability.
Figure 10: A Diamond before (left) & after (right) being treated with lasers to reduce the impact of the eye-visible inclusion on its table (Source: US Diamond Technologies)
Are Treated Natural Gemstones Authentic?
Treated gemstones are just as natural as their untreated counterparts - the only difference being that they are scientifically enhanced to look their best. Most of the gemstones available in the market today are treated – simply because perfect-looking gemstones are so rare that they cost a fortune and therefore, are not accessible to most individuals.
A gemstone’s treatment does not make them worth any less, rather highlights that extra time and effort has gone into making them beautiful. Unless the gemstone you are purchasing has undergone treatments that affect its strength and longevity or is designed to hide any internal cracks or flaws, you need not worry. That being said, an authentic natural gemstone that has been enhanced must always carry a disclosure label of its treatment. Many a time, traders may sell enhanced gemstones without proper documentation of their treatments, and for this reason, you should always purchase gemstones from a seller that you trust.
Are There Any Risks Associated With Buying Treated Gemstones?
Treatments may affect the durability or stability of the gemstone, making it more prone to damage or colour alteration over time. Some treatments also need special care while cleaning. When buying gemstones, keep in mind that two things matter: the type of treatment, and which gemstone you are buying. Heating sapphires or oil-filling emeralds don't affect the gemstone’s durability. However, filling rubies with glass or emeralds with resin can decrease their clarity and durability. Remember that each gemstone has its own needs. For example, blue topaz needs to be heated to get an appealing colour, most citrines are heated amethysts, and heating emeralds is a bad idea because they can break easily.
When buying a natural gemstone, inquire about whether the gemstone has been treated to enhance colour, clarity, or fracture-filling. Undisclosed treatments can lead to misrepresentation of the gemstone's value and quality and result in dissatisfaction with your purchase.
Where Can I Buy High-Quality Treated Natural Gemstones Online in India?
Whether you are buying a precious gemstone like rubies, emeralds, sapphires, or diamonds, or semi-precious gemstones like aquamarines, amethysts, citrines, turquoises, peridots, zircons, or opals, always make sure you are buying from an authentic seller. At Precious Earth, we are 4th generation gemstone sellers with over 85 years in the business. We deliver gemstones all over India with full transparency of any treatments. What's more, we provide a lifetime return policy so that you can be 100% satisfied with your purchased gemstone.
