The term enhancement is defined as any treatment or process other than cutting and polishing that improves the appearance (color/clarity/phenomena), durability, value or availability of a gemstone. In today’s gem marketplace, many gemstones have been enhanced by a variety of methods. Such processes may range from simple heating (such as with tanzanite) to high-tech irradiation (such as blue topaz).
At Pala International, we take enhancement disclosure seriously and guarantee, to the best of our abilities, to provide our customers with complete information on any and all enhancements to which a gem has been subjected. While many enhancements are currently undetectable, we do our best to provide all the information you need for informed buying decisions.
The guidelines we follow are those of the AGTA and are the most stringent in the industry. In addition, we have modified these guidelines slightly in areas where we feel they are not stringent enough (example: flux healing of ruby).
Some gemstone enhancements are less stable than others, meaning that the appearance of a gem may change with time. It is the general policy of Pala International to sell only those gemstones whose enhancements (if any) have good to excellent stability. In the event that we offer a gem with less than good stability, we will ensure you are aware of the special care needed for that stone. A gemstone enhancement is considered stable as long as the gem does not change in appearance (color and/or clarity) under normal wear, cutting, cleaning, repair or display conditions. Gemstones can be divided into three basic enhancement categories.
- Not Enhanced (N)
The “N” symbol is used on our invoices to indicate one of two situations. First, there are certain gemstones that are not currently known to be enhanced (alexandrite, some garnets, etc.). Second, the “N” symbol may also be used for a gem where it can be proved via gemological or other means that a gem has not been subjected to any enhancement. When you see the “N” symbol on our invoice, we guarantee that the gem in question is unenhanced.
- Normally Enhanced (E)
The “E” symbol is used for gemstones that are routinely enhanced. Since many enhancements are difficult or impractical to prove definitively, unless otherwise indicated, our approach is to assume that such enhancements have been applied to that particular gemstone. This assumption is made to protect both buyer and seller. If a more specific method of enhancement is known, then the specific enhancement code will be used.
- Nontraditional Enhancements (T)
For gemstones not covered by the “N” and “E” symbols, a code covering the specific gemstone enhancement will be listed.
Symbols for Specific Forms of Enhancement
- B = Bleaching: The use of heat, light and/or chemicals or other agents to lighten or remove a gemstone's color. This is often accompanied by subsequent dying and/or impregnation.
Example: bleached cultured pearl; bleached/impregnated jadeite (‘B-jade’)
- C = Coating: The use of such surface enhancements as lacquering, enameling, inking, foiling, or sputtering of films to improve appearance, provide color or add other special effects.
Example: coated diamond
- D = Dyeing (staining): The introduction of coloring matter into a gemstone to give it new color, intensify existing color or improve color uniformity.
Example: dyed green jadeite
- F = Filling: The filling of surface-breaking cavities or fissures with colorless glass, plastic, or some similar substance. This process will improve durability, appearance and/or add weight.
- Fh = Flux healing: During heat enhancement, fluxes (or heat alone) may be used to heal fractures/fissures which were formerly open. The process dissolves the walls of the fractures and redeposits the molten gem material, healing the fractures closed.
Example: ruby (particularly that from Möng Hsu, Burma)
- H = Heating: The use of heat to alter color, clarity, and/or phenomena.
Example: Ruby, sapphire, tanzanite, aquamarine, demantoid garnet
- I = Impregnation: The impregnation of a porous gemstone with a colorless agent (usually plastic) to give it durability and improve appearance.
Example: Stabilized turquoise
- L = Lasering: The use of a laser and chemicals to reach and alter inclusions.
- O = Oiling/Resin Infusion: The filling of surface-breaking fissures with a colorless oil, wax, resin or other colorless substances, except glass or plastic, to improve the gemstone’s appearance.
- R = Irradiation: The use of neutrons, gamma, ultraviolet and/or electron bombardment to alter a gemstone’s color. The irradiation may be followed by a heating process.
Example: blue topaz
- U = Lattice (‘bulk’ or ‘surface’) Diffusion: Outside-in diffusion of coloring chemicals via high-temperature heat treatment to produce color and/or asterism.
Example: lattice diffusion-treated sapphire
- W = Waxing/Oiling: The impregnation of a colorless wax, paraffin and/or oil in porous gemstones to improve appearance.
Natural Gemstone Enhancement Chart
(based on the AGTA Source Directory 2000–2001)
|Gemstone Information Chart|
|Gemstone||Tag Code||Enhancement||Frequency Used||Stability||Care Required||Special Advice|
||E or W||Impregnated with a colorless wax, paraffin or oil to improve appearance||Usually||Good to Fair||Special||Avoid heat, chemicals and ultrasonic|
|I||Impregnated with plastic and other hardened resins to improve appearance||Usually||Very Good||Special||Avoid chemicals and ultrasonic.|
|E or H||Heated to improve appearance and ''sun spangles,'' or deepen color||Usually||Very Good to Good||Special||Avoid chemicals and ultrasonic.|
|D||Dyed or surface treated to add color||Rarely||Variable||Special||Avoid repolishing surface, chemicals and ultrasonic|
|Amethyst||E or H||Heated to lighten color and/or to remove ''smokey'' components||Occasionally||Excellent||Special||Some unheated material may fade in long exposure to sunlight|
|Ammolite||I||Impregnated with colorless hardened substances to increase stability||Usually||Good to Fair||Special||Avoid heat, household chemicals and ultrasonic|
|Aquamarine||E or H||Heated to remove yellow component, thereby producing a pure blue color||Usually||Excellent||Normal||--|
|Beryl, Blue (''Maxixe'' Type)||R||Irradiated blue from pale pink to colorless||Always||Poor||Extra Special||Color fades, avoid light and heat|
|Beryl, Pink||E or H||Heated to remove yellow component, thereby producing a purer pink color||Commonly||Excellent||Normal||--|
|Beryl, Red||E or O||The penetration of colorless oil and resins into fissures to improve appearance||Commonly||Very Good to Fair||Special||Avoid high temperatures, steam cleaning, chemicals and ultrasonic|
|Beryl, Yellow||R||Produced by irradiation||Usually||Variable||Normal/Special depending on method||Certain stones may fade in light or heat|
|Chalcedony, Agate||D||Dyed||Usually||Excellent to Good||Normal||--|
|Chalcedony, Black (Onyx)||D||Dyed||Always||Excellent to Good||Normal||--|
|Chalcedony, Blue||D||Dyed||Commonly||Good to Fair||Special||Certain stones may fade in light or heat|
|Chalcedony, Green||D||Dyed||Usually||Good to Fair||Special||Certain stones may fade in light or heat|
|E or H||Heated to produce color||Usually||Excellent||Normal||--|
|D||Dyed to produce color||Occasionally||Excellent to Good||Special||Certain stones may fade in light or heat|
|Chalcedony, Jasper||D||Sometimes dyed to imitate other stones||Occasionally||Excellent||Normal||--|
|Chrysoberyl, Cat's Eye||R||Irradiated to change color||Occasionally||Excellent||Normal||For safety requirements, if neutron irradiated, refer to the AGTA website provided in the resources section of this article.|
|Chrysoberyl, Yellow (Transparent)||N||None||--||--||Normal||--|
|Chrysoberyl, Brown (Transparent)||N||None||--||--||Normal||--|
|Chrysoberyl, Green (Transparent)||N||None||--||--||Normal||--|
|Citrine||E or H||Produced by heating various types of quartz||Usually||Excellent||Normal||--|
|Coral, Black||N||None||--||--||Special||Avoid chemicals, cosmetics and ultrasonic|
|Coral, White||E or B||Bleached||Commonly||Good||Special||Avoid chemicals, cosmetics and ultrasonic, material may discolor in time|
|Coral, Pink||E or W||Impregnated with colorless wax||Commonly||Good||Special||Avoid chemical and ultrasonic|
|Coral, Orange||I||Stabilized with plastic to improve color and durability||Commonly||Good||Special||Avoid chemical and ultrasonic|
|Coral, ''Gold''||B||Bleached from black coral||Usually||Very Good||Special||Avoid chemical and ultrasonic|
|Coral, Red||D||Dyed||Occasionally||Variable||Special to Extra Special depending on type of dye||Certain materials may face in light or heat. Avoid chemicals, cosmetics and ultrasonic|
Diamond, Colorless to Faint Yellow
|L||Laser drilled to improve appearance||Occasionally to Commonly||Very Good||Normal||--|
||C||Coated to disguise off-color||Rarely||Very Good to Poor Depending on Method||Variable||Recutting, steam cleaning, ultrasonic and occasionally alcohol may adversely affect color and appearance|
||F||Filling of surface cavities or fractures with a hardened substance||Occasionally||Very Good||Special||Recutting or extreme heat may remove filling material|
|HP||Use of heat with pressure to alter color and/or clarity||Rarely||Unknown||Normal||--|
|L||Laser drilled to improve appearance||Occasionally||Very Good||Normal||--|
||F||Filling of surface cavities or fractures with a hardened substance||Rarely||Very Good||Special||Recutting or extreme heat may remove filling material|
||R||Irradiated and/or heated to induce ''fancy'' colors||Occasionally||Excellent to Very Good||Normal except green||Avoid heating treated green stones as the color may change. Some green stones have been radium irradiated for safety requirements; refer to the NRC|
||C||Coated to ''fancy'' colors||Rarely||Fair to Poor||Special||Recutting, steaming and ultrasonic may adversely affect color and appearance|
|H||Use of heat to alter color||Rarely||Unknown||Normal||--|
|Diopside (Chrome)||N||None||--||--||Special||Avoid sudden temperature changes and harsh chemicals|
|E or O||The penetration of colorless oil, wax and resins into fissures to improve appearance||Usually||Very Good to Fair||Special||Avoid sudden temperature changes, steaming, chemicals and ultrasonic|
|D||Dyed with color agents||Occasionally||Variable||Special||Avoid sudden temperature changes, steaming, chemicals and ultrasonic|
|Garnet, Alamandite||N||None||--||--||Normal||Avoid sudden temperature change|
|Garnet, Demantoid||N||None||--||--||Normal||Avoid sudden temperature change|
|Garnet, Grossularite||N||None||--||--||Normal||Avoid sudden temperature change|
|Garnet, Pyrope||N||None||--||--||Normal||Avoid sudden temperature change|
|Garnet, Rhodolite||N||None||--||--||Normal||Avoid sudden temperature change|
|Garnet, Spessartite||N||None||--||--||Normal||Avoid sudden temperature change|
|Garnet, Tsavorite||N||None||--||--||Normal||Avoid sudden temperature change|
Ivory and Bone
|E or B||Bleached to whiten and remove discoloration||Commonly||Good||Special||Avoid chemicals and ultrasonic, may discolor in time|
||D||Dyed for artistic purposes||Occasionally||Good||Special||Avoid chemicals and ultrasonic, may discolor in time|
|W||Impregnated with colorless paraffin wax||Occasionally||Good||Special||Avoid chemicals and ultrasonic, may discolor in time|
|Mammoth (Ivory)||I||Impregnated with colorless hardened substances to increase stability||Commonly||Good||Normal||--|
|E or W||Coated with colorless wax||Commonly||Fair||Normal to Special||Avoid ultrasonic|
|B or W||Two-step bleaching and wax impregnation||Rarely||Poor||Special||Avoid heat, chemicals and ultrasonic|
Jade; Green, White and Purple
|B and S||Two-step bleaching and polymer impregnation||Commonly||Very Good to Good||Special||Avoid heat, chemicals and ultrasonic|
|D||Dyed to imitate natural colors||Occasionally||Variable||Special||Avoid strong light, chemicals and ultrasonic, may discolor in time|
|Jade, Nephrite||D||Dyed selectively to alter color for artistic purposes in carvings||Rarely||Unknown||Special||Avoid chemicals, ultrasonic and strong light|
|E or H||Heated to improve color from certain locations||Commonly||Fair||Special||Natural and/or treated materials may fade--avoid strong light, ultrasonic|
|R||Irradiated and heated to darken color||Commonly||Fair||Special||Natural and/or treated materials may fade--avoid strong light, ultrasonic|
|E or W||Coated with colorless wax or oil to improve appearance||Commonly||Fair||Normal to Special||Avoid chemicals and ultrasonic|
|D||Dyed to provide color and/or uniformity||Commonly||Variable||Special||Avoid chemicals and ultrasonic|
|W||Coated with colorless wax||Occasionally||Fair||Special||Avoid chemicals and ultrasonic|
|I||Impregnated with plastic and/or other hardened agents to improve durability and appearance||Rarely||Good||Special||Avoid chemicals and ultrasonic|
Opal; White, Black and Semi-Black
|O||Impregnated with colorless oil, wax and resins||Rarely||Fair||Special||Avoid ultrasonic, heat and solvents|
|I||Impregnated with colorless plastic to increase durability and improve appearance||Rarely||Good||Special||Avoid heat and solvents|
|Opal, Matrix||D||Sugar solution infilling in acid bath to darken background and enhance color play and intensity||Commonly||Good||Special||Avoid solvents and repolishing|
|Opal, Boulder||O||Infusion of unhardened essentially colorless substances into voids to improve appearance||Occasionally||Fair||Special||Avoid heat, chemicals, ultrasonic and repolishing|
|Opal, Fire Opal||N||None||--||--||Special||Avoid heat|
|Opal, Cat's Eye||I||Impregnated with colorless resins to give durability and improve appearance||Usually||Good||Special||Avoid heat, chemicals and ultrasonic|
|O||Impregnated with colorless oil, wax and resins to hide crazing||Commonly||Fair||Special||Avoid heat, solvents and ultrasonic|
||D||Impregnated with hardened agents to improve appearance and increase durability||Commonly||Good||Special||Avoid heat and solvents|
|I||Impregnated with colorless plastic to improve appearance and increase durability||Commonly||Good||Special||Avoid heat and solvents|
|E or B||Bleached to improve color and appearance||Usually||Very Good||Special||Avoid cosmetics and household chemicals|
|D||Dyed with or without chemical treatment combined with heat to produce gray to black||Rarely||Very Good to Good||Special||Avoid chemicals, cosmetics and ultrasonic|
|E or B||Bleached to improve color and uniformity of white color only||Usually||Excellent||Special||Avoid chemicals, cosmetics and ultrasonic|
||D||Dyed to give rose, blue or golden overtones||Usually||Good||Special||Avoid chemicals, cosmetics and ultrasonic|
||D||Dyed blue, black and other colors includes use of colored nuclei||Occasionally||Variable||Special||Avoid chemicals, cosmetics and ultrasonic|
||D||Dyed all colors (freshwater)||Usually||Very Good||Special||Avoid chemicals, cosmetics and ultrasonic|
|R||Irradiated to produce blue, gray, black and bronze colors||Occasionally||Very Good||Special||Avoid chemicals, cosmetics and ultrasonic|
|D||Chemical treatment combined with heat to produce gray to black||Commonly||Very Good to Good||Special||Avoid chemicals, cosmetics and ultrasonic|
|Pearl, Mabe ''Pearl''||--||For more information, please refer to the AGTA website provided in the resources section of this article.||--||--||Extra Special||Avoid household chemicals, cosmetics, abrasives and sudden shock|
|E or O||Penetration of colorless oil, wax and resins into voids to improve appearance||Rarely||Good to Fair||Special||Avoid sudden temperature changes, harsh chemicals and ultrasonic|
|F||Filling of surface fractures with a colorless hardened substance||Rarely||Good||Special||Avoid sudden temperature changes, harsh chemicals and ultrasonic|
|Rhodonite||D||Dyed to ''even out color''||Occasionally||Poor||Special||Avoid chemicals and ultrasonic|
|H||Heated to improve color and appearance. (residue of foreign substance is not visible under 10X magnification)||Usually||Excellent||Normal||--|
||D||Dyed with colored oil to improve appearance||Rarely||Poor||Special||Avoid household chemicals and ultrasonic|
||F||Intentional filling of surface cavities and fractures with a foreign material, including glass, which is visible under 10X magnification||Commonly||Very Good to Fair||Special||Fracture filling in Rubies may be fragile and may fall out under extreme pressure. Avoid heat and ultrasonic|
||R||Irradiated to change color||Rarely||Unknown||Normal||For safety requirements, if neutron irradiated, refer to the AGTA website provided in the resources section of this article.|
|Diffusion of an element or elements (with the exception of hydrogen) into the lattice of a stone during the application of heat to create artificial color or asterism.||Occasionally||Excellent or Good when effect is not near surface (I)||Normal||--|
|Effects may be throughout the stone or at or near the surface (I). For more information, please refer to the AGTA website provided in the resources section of this article.||--||Normal or Special when effect is near surface||Special||Avoid repolishing or recutting when effect is near surface (I)|
|H||Heated to produce, intensify or lighten color and/or improve color uniformity and appearance||Usually||Excellent||Normal||--|
|Diffusion with an element or elements (with the exception of hydrogen) into the lattice of a stone during the application of heat to create artificial color or asterism.||Commonly||Good when effect is not near surface||Normal||--|
||Effects may be throughout the stone or at or near the surface (I). Most colors may be produced. For more information, please refer to the AGTA website provided in the resources section of this article.||--||Normal or Special when effect is near surface||Special||Avoid repolishing or recutting when effect is near surface|
|R||Irradiation to provide temporary intense yellow or orange color||Occasionally||Very Poor||Extra Special||Fades quickly in light or heat|
|D||Dyed various colors||Commonly||Good to Fair||Special||Dye may fade|
|E or W||Impregnated with colorless wax||Commonly||Very Good to Good||Special||Avoid ultrasonic|
|Sodalite||D||Dyed||Rarely||Fair||Special||Dye may fade|
|Spodumene, Green||R||Irradiated to produce yellow color||Rarely||Poor||Extra Special||Color fades in light or heat|
|Spodumene, Yellow||R||Irradiated to produce green color||Rarely||Poor||Extra Special||Color fades in light or heat|
|Tanzanite||E or H||Heated to produce violet-blue color||Usually||Excellent||Special||Avoid sudden temperature changes|
|Topaz, Blue||R||Irradiated brown and often heated to produce blue color||Usually||Excellent||Normal||For safety requirements, if neutron irradiated, refer to the AGTA website provided in the resources section of this article.|
|Topaz, Yellow/Orange||R||Irradiated to intensify color||Occasionally||Variable||Special||Avoid heat and strong light|
|Topaz, Pink/Red||E or H||Heated chromium-bearing pinkish-brown to orange stones||Usually||Excellent||Normal||--|
|Topaz, Brown||N||None||--||--||Special||May fade in exposure to sunlight|
|Topaz, Green||R||Irradiated to produce a green color||Occasionally||Poor||Extra Special||Color fades in exposure to sunlight|
|Topaz, Green||U||Diffusion of color at or near surface. For more information, please refer to the AGTA website provided in the resources section of this article.||Usually||Good||Special||Avoid repolishing or recutting|
|Topaz, All Colors||C||Any substance applied to the surface of the gemstone to artificially modify color and/or appearance||Commonly||Poor||Special||Avoid repolishing or recutting, steaming, chemicals or ultrasonic|
|Tourmaline, Chrome Vanadium||N||None||--||--||Normal||--|
|Tourmaline, Cat's Eye||N||None||--||--||Normal||--|
|E or H||Heated to improve color||Rarely||Excellent||Normal||--|
|R||Irradiated to improve color||Rarely||Very Good||Normal||--|
Tourmaline; Green, Blue
|E or H||Heated to improve color||Commonly||Excellent||Normal||--|
|O||The penetration of colorless oil or resins into voids to improve appearance||Occasionally||Good to Fair||Special||Avoid temperature changes, steaming, chemicals and ultrasonic|
Tourmaline; Pink, Red, Purple
|E or H||Heated to improve color||Occasionally||Excellent||Normal||--|
||R||Irradiated to intensify color||Commonly||Good||Normal||--|
||O||Penetration of colorless oil or unhardened resins into voids to improve appearance||Occasionally||Good to Fair||Special||Avoid temperature changes, steaming, chemicals and ultrasonic|
|D||Penetration of coloring agents into voids to improve appearance||Occasionally||Fair to Poor||Special||Avoid temperature changes, steaming, chemicals and ultrasonic|
|I||Impregnated with plastic to create or improve color and increase durability||Commonly||Good||Special||Avoid hot water and household chemicals|
||W||Impregnated with colorless oil or wax to enhance or create color||Commonly||Fair to Poor||Special||Avoid hot water and household chemicals|
|D||Dyed to improve color||Rarely||Poor||Extra Special||Avoid hot water and household chemicals|
|Zircon; Green, Brown||N||None||--||--||Special||Avoid harsh abrasives|
|Zircon, Yellow||E or H||Heated to improve color||Rarely||Good||Special||Avoid harsh abrasives|
|Zircon, Blue and Colorless||E or H||Brownish crystals are heated to these colors||Always||Fair to Poor||Special||Avoid harsh abrasives and strong light|
|Zircon, Red||E or H||Heated to change brownish crystals to red||Commonly||Fair to Poor||Special||Avoid harsh abrasives and strong light|
- The “N” symbol is used only for gemstones that we guarantee have not been enhanced.
- All jewelry (with or without stones) requires special care; some jewelry requires extra-special
- * Indicates a gemstone that generally requires special or extra-special care (although the need for care is not necessarily related to the enhancement).
If you need additional information on gemstone enhancements or care, call us at 800-854-1598.