Gemstone treatments and enhancements have been around for almost as long as the gemstone trade itself. Recently however treated gemstones have been flooding the markets.
Now it is more important than ever to know what treatments are around and how to recognize them. So that you do become a victim of these practices.
From waxing to irradiation this article gives an overview of all common gemstone treatments and enhancements and the advantages and disadvantages of these practices.
Advantages of Gemstone Treatments
There are a number of advantages to enhancing and treating gemstones. First of all it increases the supply of amazing gemstones making it available at a price more people can afford. A prime example of this is citrine, they are rare in nature and would be quite expensive if they could not be created by heat treating amethyst.
The second advantage is creating colors that do not even exist in nature either by dyeing or by irradiation. A good example of this is black onyx, a chalcedony (also known as agate) in a color that does not exist in nature.
Thirdly certain treatments can (dramatically) increase the durability of a gemstone. Stabilizing a gemstone is often done with oil or wax. This is commonly done to lapis lazuli and turquoise to improve its appearance and durability.
Disadvantages of Gemstone Treatments
With its many advantages also come disadvantages. The main problem with this practice is that it’s used by unscrupulous dealers to con customers (sometimes even dealers fall victim to this). A treated gemstone that is sold as if it is natural can be sold for a higher price because of its better appearance.
Another disadvantage is that some treatments can have drawbacks. The main example being gemstones that have been treated by oiling or waxing. Gemstones that normally can be cleaned in hot water or a jewelry steam cleaner cannot be cleaned in this way anymore, because wax and oil melt at high temperatures.
Common Gemstone Treatments
A gemstone is bombarded with electrons or neutrons that often permanently change its color. Some color changes are not as stable, but it is not that common to see these on the market. The second most common treatment is irradiation.
It is almost impossible to distinguish an irradiated gemstone from a natural one. The reason being that most gemstones are irradiated by natural radiation during and after they are formed.When this treatment was first used the main problem was that gemstones stayed radioactive for a long time.
Today however improvements in the process have almost removed the radioactivity. Irradiated gemstones can also not be imported until they no longer pose a health concern and this policy is strictly enforced.Gemstones that are commonly irradiated include: blue topaz, tourmaline, quartz and more recently colored diamonds are irradiated to produce fancy colors.
Dyeing is often done to gemstones with a high porosity, because the pores easily take up the dye. For these gemstones the change is often permanent. Gemstones in a crystal form can be dyed as well, however usually this change is temporary. Often this is used to fill up fractures that reach the surface.
The practice of dyeing is frowned upon in the gemstone industry and when it is discovered that a material is dyed the value usually plummets. The only gemstone where it is generally accepted is the black onyx.Gemstones that are commonly dyed include: Black onyx, howlite, jade and coral.
Also called impregnation, a porous gemstone is impregnated with a resin, plastic or wax that hardens. This increases the durability and at times the appearance of a gemstone. This change is permanent in the case of plastic stabilization but for wax and resin high temperatures could weaken the bonding.
Heating is the most commonly used treatment around. Reportedly some of the gemstones that were recovered from the tomb of Tutankhamun were heat-treated and we are talking about 1300 BC here! The way a gemstone is heated can vary, sometimes they are heated to near their melting point. While at other times they are heated for days on end at lower temperatures. It all depends on what change is desired.
Heat treatment is virtually always a permanent change.The benefits of heat treatment are improvement of color, clarity and at times brightness. In some cases even creating colors that are extremely rare or non-existent in nature. Gemstones that are commonly heat-treated include: citrine, tanzanite, ruby, sapphire and amber.
The surface of a gemstone is covered in wax to improve the durability and in some cases appearance. Waxing is generally accepted in the gemstone trade when it is disclosed. This is because this practice is so old it is considered a tradition. Though waxing is not permanent it is fairly simple to wax the gem again, even as a novice.Gemstones that are often waxed are: Jadeite, turquoise, lapis lazuli and rhodochrosite.
Laser drilling is almost only seen in diamonds, where it is used to increase diamond clarity. Basically a laser is used to drill a hole to an inclusion or other imperfection. This problem area is then either filled with a substance or first burned away and then filled. The easiest way to identify this treatment is by the tiny holes that are left behind that are usually visible at a standard magnification of 10 times.
Another method to improve the color and appearance of a gemstone through the use of paint, ink, etc. These are fairly easy to detect, though there are methods used that can be quite hard to detect.
One of these methods is adding a small blot of ink beneath a diamond that is slightly yellow. The light reflects of the blue dot and mixes with the yellow light of the diamond, leading to a color that is more white that before.
Often making it appear several shades lighter and quite a bit more expensive. When this is not disclosed this is clearly fraudulent.
Another great example is mystic topaz, it is coated with a metallic vapor creating a beautiful iridescent topaz. This type of topaz is not found in nature and is entirely artificial.Gemstones that are at times coated include: topaz and quartz.
Often used on gemstones that have surface fractures or small holes in them. Usually they are filled with colorless glass or a plastic. The advantages are that it improves the appearance and feel of a gemstone. A disadvantage is that this is a permanent change and over time the color of the filling may change, showing discolored areas on a gemstone.
The filling almost always is made of a material that is not as durable as the material of the host and may be damaged more easily. A filled gemstone is worth far less than a natural gemstone. When a colored filling is used this is considered dyeing and the price decreases even further.For more information on this treatment take a look at the following article: Mahaleo ruby
In effect the same as the filling mentioned above, only in this case it is filled with a liquid substance. Though temporary it is more accepted than filling with glass. Virtually all emeralds are oiled and prices for these are almost the same as for non-oiled emeralds. Unless a colored oil is used, this is considered dyeing and the price should be far lower.
Essentially diffusion is heat treatment except first different elements are added to the gemstone. These elements diffuse into the surface of the gemstone under high temperatures. Titanium and chromium are two elements that are often used in this process. For example when you add titanium and iron powder to a sapphire and heat them to the near melting point of sapphire the surface layer of the sapphire becomes a darker blue.
The advantage of diffusion is that you can buy a gemstone with a deep color for a fraction of the cost of a gemstone with the same natural color. The problem is that this color is only present in a tiny surface layer. Normally if the gemstone is scratched or chipped you could simply get it polished or recut. With a diffused gemstone this is not possible because it would show areas without the colored surface layer.
This makes a diffused gemstone particularly useful for jewelry that you only wear on special occasions. Definitely not something you’d want to put in an engagement ring worn every day.
Newer diffusion methods (bulk or lattice diffusion) using lighter elements make it possible to extent the new color further into the gemstone. Which makes it harder to detect, but also more resistant to wear and tear.
Bleaching is a treatment that is permanent and not detectable. It is mostly used for organic gemstones to lighten their color. Particularly pearls are often bleached either through chemicals or simply by exposing it to sunlight. This is the easiest way to get a large number of pearls in an even color which is what the market demands. Gemstone that are commonly bleached are: pearls, ivory, coral‘and jadeite.
Gemstone treatments and enhancements are becoming more and more common, leading to an increase in availability (and a decrease in price) of previously rare gemstones. The disclosure however of such practices unfortunately is lacking at times.
To avoid paying the price for a natural gemstone when you are in fact getting a glass-filled, diffused gemstone worth a fraction, you should only buy from dealers that can be trusted to give full disclosure. Especially because some treatments are almost impossible to detect even with specialized equipment, let alone the naked eye.
For expensive gemstones I advise always getting a grading report from a renowned gemological institute such as the GIA, AGS and AIGS. A report is fairly expensive, but can save you from making a very costly mistake.