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 Natural Gemstone, 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 Natural Gemstone 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)

Natural Gemstone Enhancement Symbol Description Used Frequency Encountered Stability Care Requirements
Agate D Usually Excellent to good Normal
     Fire Agate N Normal
Alexandrite N Normal
Amber E or H Usually Very good to good *Special
D Rarely Variable Special
Amethyst E or H Occasionally Excellent *Special
Ametrine N Normal
Andalusite N Normal
Aquamarine E or H Usually Excellent Normal
Beryl R Maxixe Always Poor X-Special
R Yellow Usually Variable Special
N Yellow-green Normal
E or O Red Commonly Very good to fair Special
Chalcedony D Black Always Excellent to good Normal
D Banded Usually Excellent Normal
D Green Usually Good to fair Special
D Blue Commonly Good to fair Special
E or H Carnelian Usually Excellent Normal
D Carnelian Occasionally Excellent to good *Special
D Jasper Occasionally Excellent Normal
N Chrysoprase Normal
Chrysoberyl N Transparent Normal
R Cat’s eye Occasionally Excellent Normal
Citrine E or H Usually Excellent Normal
Coral N Black *Special
E or B White Commonly Good Special
E or W Pink Commonly Good Special
I Orange Commonly Good Special
B Gold Usually Very good Special
D Red Occasionally Variable X-Special
Natural
Gemstone
Enhancement
Symbol
Description
Used
Frequency
Encountered
Stability Care
Requirements
Diamond L Occasionally Very good Normal
C Rarely Very good to poor Special
F Occasionally Very good Special
HP Rarely Unknown Special
Diamond – Fancy R Occasionally Excellent to very good Special
L Occasionally Very good Normal
F Rarely Very good Special
C Rarely Fair to poor Normal
H Rarely Unknown Normal
Diopside – Chrome N *Special
Emerald E or O Usually Very good to fair Special
D Occasionally Variable Special
Garnet N All varieties *Special
E or H Some demantoid Commonly Very good *Special
Hematite N Normal
Iolite N Normal
Jade – Jadeite E or W Commonly Fair Special
B and I Green/purple/white Commonly Very good to good Special
D Occasionally Variable Special
B and W Rarely Poor Special
Jade – Nephrite D Rarely Unknown Special
Kunzite E or H Commonly Fair Special
R Commonly Fair Special
Natural
Gemstone
Enhancement
Symbol
Description
Used
Frequency
Encountered
Stability Care
Requirements
Lapis lazuli E or W Commonly Fair Special
D Commonly Variable Special
Moonstone N Normal
Morganite E or H Commonly Excellent Normal
Opal O White/black Rarely Fair Special
I Rarely Good Special
O Boulder Usually Good Special
D Matrix Commonly Good Special
N Fire opal *Special
I Cat’s eye Usually Good Special
I/O/D Hydrophane Commonly Good to fair Special
Pearl – Natural E or B White Usually Very good Special
D Rarely Very good to good Special
Pearl – Cultured E or B White Usually Excellent Special
D Many colors Usually Variable Special
R Black/gray Occasionally Very good Special
Peridot E or O Rarely Good to fair Special
F Rarely Good Special
Ruby E or H Usually Excellent Normal
Fh Commonly Excellent Normal
O Occasionally Good to fair Special
D Rarely Poor Special
R Rarely Unknown Normal
F Commonly Very good to fair Special
U Rarely Good Special
Natural
Gemstone
Enhancement
Symbol
Description
Used
Frequency
Encountered
Stability Care
Requirements
Sapphire E or H Usually Excellent Normal
U Occasionally Good to fair Special
O Occasionally Good to fair Special
Sapphire – Fancy E or H Usually Excellent Normal
R Yellow/orange Occasionally Very poor X-Special
O Occasionally Good to fair Special
U Occasionally Good to fair Special
Serpentine D Various colors Commonly Good to fair Special
E or W Commonly Very good to good Special
Spinel N Normal
O Occasionally Good to fair Special
Sugelite N Normal
Sunstone N Normal
Tanzanite E or H Usually Excellent *Special
Topaz R Blue Usually Excellent Normal
R Yellow/orange Occasionally Variable Special
R Green Occasionally Poor X-Special
U Green Usually Good Special
N Brown *Special
E or H Red/pink Usually Excellent Normal
Natural
Gemstone
Enhancement
Symbol
Description
Used
Frequency
Encountered
Stability Care
Requirements
Tourmaline N Chrome green Normal
N Cat’s Eye Normal
E or H Yellow/orange Rarely Excellent Normal
R Yellow/orange Rarely Very good Normal
E or H Green/blue Commonly Excellent Normal
O Any color Occasionally Good to fair Special
E or H Pink/red/purple Occasionally Excellent Normal
R Pink/red/purple Commonly Good Normal
D Pink/red/purple Occasionally Fair to poor Special
Turquoise W Commonly Fair to poor Special
D Rarely Poor X-Special
I Commonly Good Special
Zircon N Green/brown *Special
E or H Blue/colorless Always Fair to poor Special
E or H Yellow Rarely Good Special
E or H Red Commonly Fair to poor Special

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: +971 4 321 9422.