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912 Live Oak Park Rd South
Fallbrook, CA, 92028
United States

+1 (760) 728-9121

Pala International has consistently earned its reputation as the direct source for the finest colored stones.

Gemstone Enhancements

Gemstone Enhancements

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.

    Example: ruby
     
  • 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.

    Example: diamond
     
  • 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.

    Example: emerald
     
  • 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.

    Example: jadeite

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
Alexandrite N None -- -- Normal --
 
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.
Amber
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
Ametrine N None -- -- Normal --
Ammolite I Impregnated with colorless hardened substances to increase stability Usually Good to Fair Special Avoid heat, household chemicals and ultrasonic
Andalusite N None -- -- Normal --
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, Yellow-Green N None -- -- 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, Banded D Dyed Usually Excellent 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
Chalcedony, Carnelian
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 --
Chalcedony, Chrysoprase N None -- -- 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 --
Diamond, Colored
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
Emerald
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
Hematite N None -- -- Normal --
Iolite N None -- -- Normal --
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 --
Jade, Jadeite
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
Kunzite
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
Lapis Lazuli
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
Malachite
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
Moonstone N None -- -- Normal --
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
Opal, Hydrophane
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
Pearl, Natural
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
Pearl, Cultured
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
Peridot
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
Ruby
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.
 
U
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)
Sapphire
H Heated to produce, intensify or lighten color and/or improve color uniformity and appearance Usually Excellent Normal --
 
U
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
Serpentine
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
Spinel N None -- -- Normal --
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
Sugilite N None -- -- Normal --
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 --
Tourmaline, Yellow/Orange
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
Turquoise
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

Notes:

  • 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 
    (X-Special) care.
  • * 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.