AGTA Enhancement Codes

We disclose ALL gemstone treatments or enhancements. The "enhancement codes" that we have listed in our online catalog for each gem are explained below.

Definition: ENHANCEMENT = Any treatment process other than cutting and polishing that improves the appearance (color/clarity/phenomena), durability, or availability of a gemstone.

The following table describes the AGTA enhancment codes we use on our site.
For other codes visit .

If you have any questions about treatments that a specific gem has undergone please contact us and we will gladly give you more information.

Code Name Description

No Treatment
The "N" symbol can be used for stones in the event that a stone has received no enhancement and the seller will provide a guarantee that there has been none.
F Filling As a by-product of heat enhancement, the presence of solidified borax or similar colorless substances which are visible under properly illuminated 10X magnification.
H Heating The use of heat to effect desired alteration of color, clarity, and /or phenomena. (Residue of foreign substances in open fractures is not visible under properly illuminated 10X magnification.
I Infilling The intentional filling of surface breaking cavities or fractures usually with glass, plastic, opticon with hardeners and/or other hardened foreign substances to improve durability, appearance and/or weight.
O Oiling/Resin Infusion The intentional filling of surface breaking cavities of a colorless oil, wax, natural resin, or unhardened man-made material into fissured transparent/translucent gemstones to improve appearance (i.e., oil, man-made resin, cedar wood oil, Canada balsam, paraffin, etc.).
R Irradiation The use of irradiation to alter a gemstone's color, may be followed by a heating process.

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