The information below is to help you understand how a poor quality stone can be enhanced so it is salable. Here are some of the most common Treatments for Gemstones

Many gemstones are treated with various methods to try to improve colour and clarity. Some of these methods are accepted in the trade today, while other methods are not. The accepted trade methods are the ones that will change the colour of the gemstone permanently.

All ethical gem dealers should fully disclose gem treatments. But in our view it is also important to provide detailed information to the buyer so that you know exactly what you buying. So we have added information below that will help educate you about the common treatments, as well as some recent innovations. Keep in mind that most coloured commercial gemstones are treated, and this is a legitimate practice as long as all facts are disclosed to the buyer. If you know the facts, then you can feel safe about buying a gemstone that you will enjoy for many years to come.

Heat treatment

Beryllium treatment

Diffusion treatment

Fracture filled treatment

Irradiation treatment. 

Heat Treatment

Centuries ago, someone stumbled upon the magical effect of applying heat to gemstones. High heat, such as that from a charcoal fire, can make a bland looking gemstone change its colour into something spectacular

Heat treatment is considered a type of enhancement. During treatment, the stone is heated to very high temperatures (approximately 1600 Centigrade) causing inclusions, chemical elements, and other impurities to reform themselves and change the colour of the stone. This colour change may result either in the stone being darker, lighter, more intense, or of a different colour. An example of this is the dissolving of rutile silk inclusions in blue sapphires, which improves both clarity and colour. This heat treatment is permanent and irreversible.

Another example is ruby. This a stone that is commonly heat treated. Only the most valuable and expensive rubies possessing the richest colours are not heat-treated. Ruby is heated almost to its melting point, allowing the aluminium oxide in the stone to reform, creating a new crystal structure. This allows the chromium in the stone to combine with different atoms, allowing for a better colour of red. The same can apply to a type of sapphire known as gouda sapphires. These milky white sapphires turn blue, and account for many of the quality sapphires on today's market.

Detection of heat and diffusion treatment is possible because these treatments modify natural inclusions. The destruction of gas or fluid inclusions or the dissolving of mineral inclusions are clues to heat treatment. For gems that contained rutile needles, the needle margins may become diffuse. On rubies, inclusions may be found that are glassy in appearance. These are caused by borax-based substances that are used in the heat treatment process.

However, it is usually more difficult to know if a stone has not been treated, in other words, has the stone never been treated? Gemologist can examine the inner workings of the stone and study the inclusions for signs of heat treatment. For example, if the stone has been treated, tiny inclusions such as small crystals will melt during the heat treatment process. A  Gemologists can easily see this using a microscope.

Centuries ago, men sitting in front of charcoal fires were the first practitioners of this art. They would blow air through pieces of bamboo into their glowing charcoal where a few stones were placed in an attempt to coax some new colours into their stones. Today, the technology is much more sophisticated, with professionals using large computer controlled electric furnaces. The old, crude methods are gone, but the result is still the same: drab gemstones are turned into something beautiful. This allows us all to have the chance to own a coloured gemstone that we can be proud to show.

Amethyst, Citrine, ametrine, aquamarine, tourmaline, topaz, light green tourmaline, sapphire, ruby, tanzanite, and blue zircon are typically colour-enhanced by heat gemstones. Here is a full list of the more commonly heated stones and how heat treatment enhances them.

• Amethyst–lightens the colour and will change the colour of pale amethyst to "yellow" that will be sold as citrine.

• Aquamarine–removes the greenish undertones that are common in this stone to produce a more blue stone. Also deepens the colour

• Citrine–often produced by heating varieties of quartz

• Kunzite–to improve colour

• Morganite–heat treatment changes the colour from orange to pinkish

• Ruby–heat treatment will improve colours. Will also remove iron stains, dissolve inclusions and fill tiny cracks

• Sapphire–to lighten or intensify colour and to improve the uniformity of the colour

• Tanzanite–to produce a more desirable blue shade

• Topaz–when used with irradiation, heat treatment will produce shades of blue. Also done to produce a pink topaz

• Tourmaline–to lighten darker shades of tourmaline. This is usually done with the green and blue varieties

• Zircon–to produce red, blue, or colourless stone

Beryllium Treatment

Beryllium Treated Yellow Sapphire

Beryllium treatment is a recent addition to techniques for treating gemstones. Beryllium treatment is a form of heat treatment, mainly for sapphire, that adds the element beryllium to the heating process. Beryllium is an element well known in the gem world, since it is an essential constituent in many gemstones, including emerald, beryl, aquamarine and chrysoberyl. When sapphires are heated with beryllium, the result is a reduction in blue tones. Thus bright yellow or orange sapphire can be produced from weak yellow or greenish gems. Some stunning colours have been produced using this method.

Beryllium Treated Orange Sapphire

This method is sometimes known as lattice diffusion. However, unlike some older forms of diffusion treatment, with beryllium diffusion the new colour is deep within the stone; and these stones can be recut if needed. This is unlike the older diffusion treatment process, which only colours the surface of the stone. After some initial controversy, beryllium treatment is now widely accepted in the gem business as a legitimate method for treating stones. However, it is very important that gems treated with this method be disclosed as such. The most common terms are "Beryllium treated" or "Be treated" ("Be" is the symbol for the chemical element beryllium).

Diffusion Treatment

A treatment that one should be aware and cautious of is diffusion treatment. There is some controversy surrounding this method of treatment. Diffusion treatment consists of exposing the surface of the stone to certain chemicals combined with high heat in a furnace. Generally, only the surface colour changes, so if you sliced the gem in half, the inside of the stone would be a different colour, usually a paler, less valuable colour. The problem is the new surface colour is not very deep, only about half a millimetre. If the stone is damaged or perhaps re-cut, then the original, undesirable colour will be noticeable. Beware of this treatment. As of now, the method is used to change the colour of ruby, green topaz, and blue sapphire. Usually the original material is a pale or almost colourless stone that is treated to change the colour of the surface. Until methods are perfected where the entire stone colour is changed, reputable dealers will always tell you which stones have been altered by this method of treatment. Some dealers even refuse to trade in these stones.

However, for star sapphires, this practice is more accepted. is a popular method for treating star sapphire, as the treatment will increase the asterism (the star effect in sapphire and ruby). The diffusion process may reach half a millimetre of depth into the gemstone. The process creates the star effect on the gemstone and the stone can be sold as a diffused star sapphire. The hardness of the gemstone is not affected by the diffusion process and the gemstone therefore keeps its original physical properties. A sapphire made into a diffused star sapphire cannot be polished or re-cut for the second time as the treatment is only on the surface of the stone. Polishing or re-cutting would take off this surface treatment. However, most buyers never re-polish or re-cut the gemstones set in jewellery. This is especially true of sapphires, as they are hard and scratch resistant gemstones.

Fracture Filled

Small cracks or fractures in a gemstone can interrupt the flow of light through the stone, creating white or "dead" spots in the colour of the stone. Sometimes these fractures–if they reach the surface of the stone–will be filled with material that will allow the light to pass through smoothly. Different chemicals are used; oil, wax, glass, epoxy, and borax are common materials. These tiny filled cavities are difficult to see without the aid of optical instruments, so the buyer should be aware of this practice. The most commonly filled stones are emerald, aquamarine, ruby, sapphire, peridot, and turquoise. It is accepted for emeralds to be oiled, as they are naturally heavily fractured.

The process of fracture filling ruby with transparent lead glass is a recent innovation that began about 2004 in Chanthaburi, Thailand. Rubies of good colour, primarily from Madagascar, that are disfigured by fissures or surface cracks can be "repaired" using heat treatment with lead glass. The refractive index of corundum and lead glass are very similar, allowing light to travel through the stone, improving the colour and clarity. These rubies are often found in large sizes at a fraction of the cost of untreated ruby of similar colour. So they represent an excellent value in the market, so long as the treatment is disclosed and the price is appropriate.

AIGS advised against excessive heating with a jeweller’s torch, but found no negative effects from cleaning with detergents or ultrasonic devices. They advise that hydrofluoric acid should not be used on these gems, and that any re-cutting or re-polishing should be performed with care.

Irradiation Treatment

Virtually every blue topaz sold in the market today is the product of irradiation treatment.

Blue topaz is actually very rare in nature, and tends to a very pale blue. The lovely blue topaz we find today are produced by subjecting clear topaz to large doses of electrons from a linear accelerator or by exposing them to neutrons from a nuclear reactor.

The colour in topaz is produced from defects in the crystal structure rather than from chemical elements in the stone. So exposing topaz to radiation induces colour changes by modifying the way in which the crystal structure absorbs frequencies of light.

Depending on the duration and type of irradiation, and the sort of heating process used afterward, the results vary from sky, to Swiss to London blue. Other slight colour variations have been produced and given their own trade names like "electric blue" and "neon blue". London blue is the scarcest and most expensive type because it requires neutron exposure (the most expensive process), and the longest holding times.

Although the irradiation of gemstones can leave some residual radioactivity, its duration is relatively short. Government agencies in the USA, and other gem irradiating nations, have strict regulations for the holding and testing of irradiated gems to assure that they are not released to the public until they are safe to handle and wear