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 Home / Gem Library / Columns / Gemstone Treatment July 15, 2024  

Gemstone Enhancement
by Jul Netco and David Weinberg
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Gemstone Enhancement

Enhancement is defined as any process other than cutting and polishing that improves the appearance (color/clarity/phenomena), durability, or availability of a gemstone

Gemstones rarely reach the customer in their rough, natural state. Perhaps the most basic "enhancement", is the faceting and polishing of a gemstone in order to enhance its beauty and wearability. This enhancement, of course, does not have to be disclosed because the gem's outward appearance makes it obvious that the process has taken place.

Other treatments may not be so obvious or quite so durable. Depending upon the material, some gems might be subjected to heating, irradiation, diffusion, filling of surface-reaching fractures with foreign compounds , bleaching, or dyeing

Gemstones are enhanced for a number of reasons:

Beauty: The treatment of a stone may alter and significantly improve the appearance of it. The modification may produce a stone that is cleaner, better color and in some cases more stable than the same material before treatment.

Price: Fine natural gem rough is always in short supply and usually very expensive. If lower quality less costly and more available materials can be treated or enhanced, the resulting production could look good and be available at a much lower price..

Demand: The demand for beautiful gem materials always exceeds the limited supply. The availability and affordability of enhanced stones fills the void and makes gemstones accessible to larger segments of the market.

Fashion: Consumers always seem to want something new. Enhanced or treated stones can be produced in quantities and in colors which are not available in natural materials at all.

The most common treatments for different types of colored stones are: heating (also known as a "burning"), oiling, irradiation, and diffusion.

Heating — is a widely accepted enhancement process used on rubies, sapphires, amber, aquamarine, amethyst, citrine, tanzanite, zircon, topaz, and tourmaline. This treatment improves the transparency and/or color of the stones. Techniques range from simply throwing gems in a fire to be cooked or burned to employing sophisticated electric or gas furnaces at specific pressures and atmospheric conditions. Much corundum has been heated to enhance the color. Tourmalines are frequently heated to lighten the color. Blue zircons are usually heated and the resulting color is permanent. Since heating is generally permanent, heated stones do not require special care.

New Heat Treatment — The new method for producing yellow and orange sapphires is a natural outgrowth of the traditional heating methods. Rough sapphire especially from Tanzania, Sri Lanka, and Madagascar is usually found associated with spinel, zircon, tourmaline, chrysoberyl and other gemstones. The mine run material is always very difficult and time consuming to separate before cooking. Thai burners noticed that some of these other gemstones could actually influence the burn. More specifically, it was discovered that the introduction of small quantities of natural chrysoberyl in the crucible would increase the preponderance of yellow and orange colors in the sapphires being burned.

Scientists discovered that beryllium from the chrysoberyl (BeAl2O4) was being diffused in extremely small and barely measurable quantities and that this was a critical aspect of the chemical reaction which affected the coloration in many of the sapphires. Whether beryllium is acting as a catalyst or not is still the subject of debate. The treatment can produce complete and total color penetration and is undetectable by conventional non-destructive gemological testing methods. Although new laser ablation technologies can detect and measure beryllium and other trace elements, these determinations are too expensive to be used for general gemological purposes.

Irradiation — gems may change color if exposed to radiation. This may come from radioactive elements within the Earth's crust, or from artificial sources. Natural radiation may take millions of years to have an effect, while artificial irradiation may take only few hours to change a gemsís color. In some cases a gem will revert to it's original color, or may fade with time. Irradiation is often used with blue topaz. The stone is irradiated brown and then heated to produce the blue color. Irradiated stones do not require special care.

Oiling — is an ancient process used to enhance the clarity of emeralds. Oil is applied to the emerald and seeps into the fissures, which reach the stone's surface. Aside from improving clarity, this process may prevent brittleness. Oiling is generally not permanent and may need to be reapplied every few years. Special care is required for cleaning; repairing or mounting oiled stones. This treatment may not be permanent but it because of its practicality it is generally accepted.

Surface Diffusion — is another method occasionally used particularly to produce blue color in sapphires. During treatment, a colorless sapphire is coated with a titanium and oxide compound and exposed to heat. This enhances and/or changes the color of the stone and is quite stable. Because the treatment is only surface related, it is generally not accepted in the trade.

The term "unacceptable" applies when the market decides that the treatment method and its products do not deserve a place in the market. Most unacceptable treatment methods alter the physical makeup of the stone in an easily recognizable way. Usually the method is recognizable due to it's crudity or because the alteration does not produce a product simulating a naturally occurring gem. Another type of unacceptable treatment happens when the resulting color is impermanent. You would not want to buy a vibrantly colored stone today only to have it lose 90% of its color tomorrow.

Most treatments that are done to improve the appearance of gemstones do not change the chemical composition of the stone. Some enhancements are difficult or impractical to prove definitively.

Beauty enhancing treatments can produce remarkable results. Less expensive materials can be transformed into beautiful gemstones. However, because fine looking enhanced stones are generally much more common than similar quality untreated stones, their value may be less. Enhancement should be disclosed. Customers can decide what they want but they should not be mislead and should be informed of the existence of any treatments or enhancements when making a purchase. The information allows them to make their own careful and informed choices.

The following is a list of accepted gemstone enhancements sanctioned by the gemstone industry. You may also review FTC abstract guide for the Definitions and Gemstone Enhancement Codes.

EMERALD: Usually oiled with colorless oil to improve appearance.
RUBY: Usually heated to improve color and appearance.
SAPPHIRE: Usually heated to produce intensity or light color and/or improve color uniformity.
TANZANITE: Usually heated to produce violet blue color.
AQUAMARINE: Usually heated to improve color.
BLUE TOPAZ: Usually irradiated and heated to produce blue color.
TOURMALINE: Commonly irradiated to intensify pink, red and purple color.
JADE: Commonly impregnated with colorless wax.
LAPIS LAZULI: Commonly impregnated with colorless wax or oil.
CORAL: Commonly bleached.
PEARLS: Commonly bleached to improve color and appearance.
BLACK ONYX: Always dyed.

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