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Articles > Gemstone Information Chart Glossary

18 Mar 2009


(B) Bleaching: The use of heat, light and/or other agents to lighten or remove a gemstone’s color.

(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.
(D) Dyeing: The introduction of coloring matter into a gemstone to give it new color, intensify present color or improve color uniformity.

(F) Filling: The filling of surface-breaking cavities or fissures with colorless glass, plastic, solidified borax or similar substances. This process may improve durability, appearance and/or add weight.

(H) Heating: The use of heat to effect desired alteration of color, clarity and/or phenomena. If residue of foreign substances in open fissures is visible under properly illuminated 10X magnification, H F should be used.

(HP) Heating and Pressure: The use of heat and pressure combined to effect desired alterations of color, clarity and/or phenomena.

(I) Impregnation: The impregnation of a porous gemstone with a colorless agent (usually plastic) to improve durability and appearance.

(L) Lasering: The use of a laser and chemicals to reach and alter inclusions in gemstones, usually diamonds.

(O) Oiling/Resin Infusion: The filling of surface-breaking fissures with 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 rays or beta particles (high energy electrons) to alter a gemstone’s color. The irradiation may be followed by a heating process.

(U) Diffusion: The use of chemicals in conjunction with high temperatures to produce ARTIFICIAL color change and/or asterism-producing inclusions.

Note: It is a violation of the FTC Guides to fail to disclose diffusion on gemstones in advertising, promotional literature or commercial documents. Suggested methods of disclosure are:

“(Gemstone): chemically colored (Color) by diffusion.”

Example: “Sapphire: chemically colored blue by diffusion.”

If the color of the diffused gemstone does not permeate the entire stone, then the following statement must also appear:

“Although the color induced in diffusion treated gemstones is permanent, it does not permeate the entire gemstone; therefore, recutting or repolishing is not recommended.”

The above disclosure language must be printed in a type size and location so as to be conspicuous.


(W) Waxing/Oiling: The impregnation of a colorless wax, paraffin or oil in porous opaque or translucent gemstones to improve appearance.




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

A gemstone enhancement is considered permanent as long as the effect of the enhancement does not change under normal wear, cutting, repair, cleaning or display conditions. If a gemstone enhancement is not permanent, appropriate disclosure is required.

All natural gemstones can be divided into three basic categories:


1) Those which are not enhanced.


(N) The “N” symbol appears on the chart only for natural stones which are not currently known to be enhanced (Alexandrite, Garnet, etc.). However, the “N” symbol can also be used for other natural gemstones in the event that a gemstone has received no enhancement and the seller will provide a guarantee that there has been none. That gemstone must be accompanied by a commercial document, such as an invoice, memorandum and/or a laboratory report, to support the fact that the gemstone is not enhanced.


2) Those which are normally enhanced.


(E) The “E” symbol indicates that the gemstone has undergone its traditional enhancement process. The type of enhancement process covered by this symbol is indicated on the charts on pages 107 through 116. For example: The “E” designation for Aquamarine means only the enhancement that is described in the chart on page 107, i.e., thermal enhancement. In the case of Emerald, the “E” designation refers only to the penetration of colorless oil, wax and/or resins into fissures.

Since many enhancements are difficult or impractical to prove definitively, the approach taken in this manual is, unless otherwise indicated, to assume that such traditional enhancement has been done to that particular gemstone. This assumption has been made in order to protect both the seller and the consumer.

The “E” symbol may be used for those gemstones and for those enhancements as prescribed on the chart. However, if the specific method of enhancement is known, the seller should use the specific enhancement code in place of the “E” symbol. (For example: “H” would be used for an Aquamarine in place of “E” [see page 107]).


3) Those treatment processes not covered under the “N” or “E” symbols are addressed in a specific manner as shown on pages 107 through 116.

For example, Ruby “F.” The surface cavities are filled with a foreign matter such as glass. Within the industry, this gemstone must be labeled with the letter “F.” This information must also be provided to the consuming public in writing using plain language. Abbreviations and codes are not sufficient.

NOTE: Multiple enhancement techniques are sometimes applied to the same material. All treatments must be listed. Example: Diamond “LF” (Lasering and Filling).