AGTA Treatment Codes
IntroductionMany Gemstones are treated and have been from the onset of the gemstone industry.
Over time new treatments have and continue to been introduced.
Stonemangems will always disclose any industry accepted treatments within the specifications of a particular gemstone in adherence to AGTA guidelines.
Stonemangems * Allan A. Goldman Inc. has been a member of the AGTA, (American Gemstone Association),since its inception in 1981.
The Symbols and AGTA enhancement chart that is for purposes of helping you understand the various treatment types that are commonly applied to gemstones in addition the care that should be applied.
Definition of EnhancementEnhancement: 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.
Please keep in mind that many of the materials shown in the chart that display traditional treatments, especially those that are noted as "Rarely" enhanced are often not enhanced at all and completely "N" Natural.
In those cases the item will be AGTA rated "N".
Defined below are the specific enhancement codes and designations that are used in the AGTA gemstone enhancement information chart.
AGTA SYMBOLS FOR SPECIFIC FORMS OF ENHANCEMENTN | Natural: No modification (or currently has no known modification process). |
ASBL | Assembled: Material made up more than one material.Some or all components can be natural but still boned together. |
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 and/or appearance, and/or to 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. |
SIM | Simulated: Man-made material with only the visual qualities as their genuine counter-part. |
SYN | Synthetic: Man-made material with the same physical, chemical and visual qualities as their genuine counter-part. |
U | Diffusion: The use of chemicals in conjunction with high temperatures to produce ARTIFICIAL color change and/or asterism-producing inclusions. |
W | Waxing/Oiling: The impregnation of a colorless wax, paraffin or oil in porous opaque or translucent gemstones to improve appearance. |
GEMSTONE | TAG CODE | ENHANCEMENT METHOD | FREQUENCY USED | STABILITY | CARE REQUIRED | SPECIAL ADVICE |
---|---|---|---|---|---|---|
Alexandrite | N | None | Normal | |||
Amazonite | W | Impregnated with a colorless wax,paraffin or oil to improve appearance | Usually | Good to Fair | Special Care | Avoid heat, chemicals and ultrasonic |
I | Impregnated with plastic and other hardened resins to improve appearance | Usually | Very Good | Special Care | Avoid chemicals and ultrasonic | |
D | Dyed or surface treated to add color | Occasionally | Fair | Special Care | ||
Amber | H | Heated to improve appearance and "sun spangles," or deepen color | Usually | Very Good to Good | Special Care | Avoid chemicals and ultrasonic |
D | Dyed or surface treated to add color | Rarely | Variable | Special Care | Color fades, avoid heat and extended sun | |
HP | Changed color and/or artificially aged, treated in autoclave | Commonly | Very Good | Normal | Avoid chemicals and ultrasonic | |
Amblygonite | R | Irradiated to improve colors | Occasionally | Special Care | Color fades, avoid heat and chemicals | |
Amethyst | H | Heated to lighten color and/or to remove "smokey" components | Occasionally | Excellent | Special Care | Some unheated material may fade in long exposure to sunlight |
Ametrine | H | None | Normal | |||
Ammolite | ASBL | Impregnated with colorless hardened substances to increase stability | Commonly | Good to Fair | Special Care | Avoid heat, household chemicals and ultrasonic |
Andalusite | N | None | Normal | |||
Apatite | H | Heated to improve color | Commonly | Good | Normal | |
R | Irradiated to improve color | Occasionally | Fair to Poor | Special Care | Avoid heat | |
Aquamarine | 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 |
Pink | R | Irradiated to improve color | Rarely | Fair | care | Avoid heat |
Yellow-Green | N | None | Normal | |||
Red | O | The penetration of colorless oil and resins into fissures to improve appearance | Commonly | Very Good to Fair | Special Care | Avoid high temperatures, steam cleaning, chemicals and ultrasonic |
Yellow | R | Produced by irradiation | Usually | Variable | Normal/Special Care depending on method | Certain stones may fade in light or heat |
Chalcedony | ||||||
Agate | D | Dyed | Usually | Excellent to Good | Normal | |
Black (Onyx) | D | Dyed | Always | Excellent to Good | Normal | |
Banded | D | Dyed | Usually | Excellent | Normal | |
Blue | D | Dyed | Commonly | Good to Fair | Special Care | Certain stones may fade in light or heat |
Green | D | Dyed | Usually | Good to Fair | Special Care | Certain stones may fade in light or heat |
Carnelian | H | Heated to produce color | Usually | Excellent | Normal | |
D | Dyed to produce color | Occasionally | Excellent to Good | Special Care | Certain stones may fade in light or heat | |
Jasper | W | Waxed | Commonly | Fair | Normal | Avoid chemicals |
Chrysoprase | N | None | Normal | |||
Chrysoberyl | ||||||
Cat's Eye | R | Irradiated to change color | Rarely | Excellent | Normal | |
Transparent Varieties: | ||||||
Yellow | N | None | Normal | |||
Brown | N | None | Normal | |||
Green | N | None | Normal | |||
Citrine | H | Produced by heating various types of quartz | Usually | Excellent | Normal | |
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 | Surface cavities or fractures filled with a hardened substance | Occasionally | Very Good | Special Care | Recutting or extreme heat may remove filling material | |
HP | Heated with pressure to alter color and/or clarity | Rarely | Unknown | Normal | ||
Colored | L | Laser drilled to improve appearance | Occasionally | Very Good | Normal | |
F | Surface cavities or fractures filled with a hardened substance | Rarely | Very Good | Special Care | Recutting or extreme heat may remove filling material | |
R | Irradiated and/or heated to induce | Occasionally | Excellent to | Normal | Avoid heating treated green stones as the color | |
"fancy" colors | Very Good | except green | 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 Care | Recutting, steaming and ultrasonic may adversely affect color and appearance | |
H | Heated to alter color | Rarely | Unknown | Normal | ||
HP | To create fancy colors | Commonly | Excellent | |||
Diopside (Chrome) | N | None | Special Care | Avoid sudden temperature changes and harsh chemicals | ||
Emerald | O | The penetration of colorless oil. wax and resins into fissures to improve appearance | Usually | Very Good to Fair | Special Care | Avoid sudden temperature changes, steaming, chemicals and ultrasonic |
D | Dyed with color agents | Occasionally | Variable | Special Care | Avoid sudden temperature changes, steaming, chemicals and ultrasonic | |
Garnet | ||||||
Almandite | N | None | Normal | Avoid sudden temperature change | ||
Demantoid | H | To improve color | Occasionally | Good | Normal | Avoid sudden temperature change |
Grossularite | N | None | Normal | Avoid sudden temperature change | ||
Pyrope | N | None | Normal | Avoid sudden temperature change | ||
Rhodolite | N | None | Normal | Avoid sudden temperature change | ||
Spessartite | N | None | Normal | Avoid sudden temperature change | ||
Tsavorite | N | None | Normal | Avoid sudden temperature change | ||
Hematite | N | None | Normal | |||
lolite | N | None | Normal | |||
Ivory and Bone | B | Bleached to whiten and remove discoloration | Commonly | Good | Special Care | Avoid chemicals and ultrasonic, may discolor in time |
D | Dyed for artistic purposes | Occasionally | Good | Special Care | Avoid chemicals and ultrasonic, may discolor in time | |
W | Impregnated with colorless paraffin wax | Occasionally | Good | Special Care | Avoid chemicals and ultrasonic, may discolor in time | |
Jade | ||||||
Jadeite | W | Coated with colorless wax | Commonly | Fair | Normal to Special Care | Avoid ultrasonic |
B or W | Two-step bleaching and wax impregnation | Rarely | Poor | Special Care | Avoid heat, chemicals and ultrasonic | |
Green, White Band and Purple | B and S | Two-step bleaching and polymer impregnation | Commonly | Very Good to Good | Special Care | Avoid heat, chemicals and ultrasonic |
D | Dyed to imitate natural colors | Occasionally | Variable | Special Care | Avoid strong light, chemicals and ultrasonic, may discolor in time | |
Nephrite | D | Dyed selectively to alter color for artistic purposes in carvings | Rarely | Unknown | Special Care | Avoid chemicals, ultrasonic and strong light |
Kunzite | H | Heated to improve color from certain locations | Commonly | Fair | Special Care | Natural and/or treated materials may fade - avoid ultrasonic and strong light |
R | Irradiated and heated to darken color | Commonly | Fair to Poor | Special Care | Natural and/or treated materials may fade - avoid heat, ultrasonic and strong light | |
Kyanite | O | The penetration of colorless oil into fissures to improve appearance | Occasionally | Fair | Special Care | Avoid sudden temperature changes, steaming, chemicals and ultrasonic |
Lapis Lazuli | W | Coated with colorless wax or oil to improve appearance | Commonly | Fair | Normal to Special Care | Avoid chemicals and ultrasonic |
D | Dyed to provide color and/or uniformity | Commonly | Variable | Special Care | Avoid chemicals and ultrasonic | |
Malachite | W | Coated with colorless wax | Occasionally | Fair | Special Care | Avoid chemicals and ultrasonic |
I | Impregnated with plastic and/or other hardened agents to improve durability and appearance | Rarely | Good | Special Care | Avoid chemicals and ultrasonic | |
Moonstone | O | Oiled to improve clarity | Occasionally | Fair | Normal | Avoid ultrasonic |
Opal | ||||||
White, Black and Semi-Black | O | Impregnated with colorless oil,wax and resins | Rarely | Fair | Special Care | Avoid ultrasonic, heat and solvents |
I | Impregnated with colorless plastic to increase durability and improve appearance | Rarely | Good | Special Care | Avoid heat and solvents | |
Matrix | D | Sugar solution infilling in acid bath to darken background and enhance color play and intensity | Commonly | Good | Special Care | Avoid solvents and repolishing |
Boulder | O | Infusion of unhardened essentially colorless substances into voids to improve appearance | Occasionally | Fair | Special Care | Avoid heat, chemicals, ultrasonic and repolishing |
Fire Opal | N | None | Special Care | Avoid heat | ||
Cat's Eye | I | Impregnated with colorless resins to give durability and improve appearance | Usually | Good | Special Care | Avoid heat, chemicals and ultrasonic |
Hydrophane | O | Impregnated with colorless oil, wax and resins to hide crazing | Commonly | Fair | Special Care | Avoid heat, solvents and ultrasonic |
D | Dyed with colorants | Occasionally | Good | Special Care | Avoid fluids and oils | |
I | Impregnated with colorless plastic to improve appearance and increase durability | Commonly | Good | Special Care | Avoid heat and solvents | |
Pearl | ||||||
Natural | B | Bleached to improve color and appearance | Usually | Very Good | Special Care | Avoid chemicals, cosmetics and ultrasonic |
D | Dyed with or without chemical treatment combined with heat to produce gray to black | Rarely | Very Good | Special Care to Good | Avoid chemicals, cosmetics and ultrasonic | |
Cultured | B | Bleached to improve color and uniformity of white color only | Usually | Excellent | Special Care | Avoid chemicals, cosmetics and ultrasonic |
D | Dyed to give rose, blue or golden overtones | Usually | Good | Special Care | Avoid chemicals, cosmetics and ultrasonic | |
D | Dyed blue, black and other colors includes use of colored nuclei | Occasionally | Variable | Special Care | Avoid chemicals, cosmetics and ultrasonic | |
D | Dyed all colors (freshwater) | Usually | Very Good | Special Care | Avoid chemicals, cosmetics and ultrasonic | |
R | Irradiated to produce blue, gray, black and bronze colors | Occasionally | Very Good | Special Care | Avoid chemicals, cosmetics and ultrasonic | |
D | Chemical treatment combined with heat to produce gray to black. | Commonly | Very Good to Good | Special Care | Avoid chemicals, cosmetics and ultrasonic | |
Mabe "Pearl" | ASBL | Assembled | Extra Special Care | Avoid household chemicals, cosmetics, abrasives and sudden shock | ||
Peridot | O | Penetration of colorless oil, wax and resins into voids to improve appearance | Rarely | Good to Fair | Special Care | Avoid sudden temperature changes, harsh chemicals and ultrasonic |
F | Surface fractures filled with a colorless hardened substance | Rarely | Good | Special Care | Avoid sudden temperature changes, harsh chemicals and ultrasonic | |
Rhodonite | D | Dyed to "even out color" | Occasionally | Poor | Special Care | 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 Care | 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 | Fair to Poor | Special Care | Fracture filling requires special care.Avoid heat, ultrasonic and common household chemicals. | |
R | Irradiated to change color | Rarely | Unknown | 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. | Occasionally | Excellent or good when effect is not near surface | Normal | ||
U | Effects may be throughout the stone or at or near the surface. | Occasionally | Normal or Special when effect is near surface | Special Care | Avoid repolishing or recutting when effect is near surface | |
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. Most colors may be produced. | Normal or Special when effect is near surface | Special Care | Avoid repolishing or recutting when effect is near surface. | |||
R | Irradiated to provide temporary intense yellow or orange color | Occasionally | Very Poor | Extra SpeciaL Care | Fades quickly in light or heat | |
Serpentine | D | Dyed various colors | Commonly | Good to Fair | Special Care | Dye may fade |
W | Impregnated with colorless wax | Commonly | Very Good to Good | Special Care | ||
Sodalite | D | Dyed | Rarely | Fair | Special Care | Dye may fade |
Spinel | N | None | Normal | |||
Spodumene | ||||||
Green or Yellow | R | Irradiated to produce green color | Rarely | Poor | Extra Special Care | Color fades in light or heat |
Sugilite | D | Improvement of color | Fair | Normal | Avoid chemicals | |
Tanzanite | H | Heated to produce violet-blue color | Usually | Excellent | Special Care | Avoid sudden temperature changes and harsh abrasives |
Topaz | ||||||
Blue | R | Irradiated brown and often heated to produce blue color | Usually | Excellent | Normal | |
Yellow/Orange | R | Irradiated to intensify color | Occasionally | Variable | Special Care | Avoid heat and strong light |
Pink/Red | H | Heated chromium-bearing pinkish-brown to orange stones | Usually | Excellent | Normal | |
Brown | N | None | Special Care | May fade in exposure to sunlight | ||
Green | R | Irradiated to produce a green color | Occasionally | Poor | Extra Special | Color fades in exposure to sunlight |
Green | U | Diffusion of color at or near surface. See Specific Forms of Enhancement, page 7 | Usually | Good | Special Care | Avoid repolishing or recutting |
All Colors | C | Any substance applied to the surface of the gemstone to artificially modify color and/or appearance | Commonly | Poor | Special Care | Avoid repolishing or recutting, steaming, chemicals or ultrasonic |
Tourmaline | ||||||
Chrome Vanadium | N | None | Normal | |||
Cat's Eye | N | None | Normal | |||
Yellow/Orange | H | Heated to improve color | Rarely | Excellent | Normal | |
R | Irradiated to improve color | Rarely | Very Good | Normal | ||
Green, Blue | H | Heated to improve color | Occasionally | Excellent | Normal | |
O | The penetration of colorless oil or resins into voids to improve appearance | Occasionally | Good to Fair | Special Care | Avoid temperature changes, steaming chemicals and ultrasonic. | |
Pink, Red, Purple | 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 Care | Avoid temperature changes steaming chemicals and ultrasonic. | |
D | Penetration of coloring agents into voids to improve appearance | Occasionally | Fair to Poor | Special Care | Avoid temperature changes. steaming chemicals and ultrasonic. | |
Turquoise | I | Impregnated with plastic to create or improve color and increase durability | Commonly | Good | Special Care | Avoid hot water and household chemicals |
W | Impregnated with colorless oil or wax to enhance or create color | Commonly | Fair to Poor | Special Care | Avoid hot water and household chemicals | |
Z | Zachery Treatment. Electrocution sealing the pours of the material | Commonly | Excellent | Normal | ||
D | Dyed to improve color | Rarely | Poor | Extra Special care | Avoid hot water and household chemicals | |
Zircon | ||||||
Green, Brown | N | None | Good | Special Care | Avoid harsh abrasives | |
Yellow | H | Heated to improve color | Rarely | Good | Special Care | Avoid harsh abrasives |
Blue and Colorless | H | Brownish crystals are heated to these colors | Always | Good | Special Care | Avoid strong UV light |
Red | H | Heated to change brownish crystals to red | Commonly | Good | Special Care | Avoid harsh abrasives and strong UV light |
Pink | H | Improves color to pink | Usually | Good | Special Care | Avoid harsh abrasives and strong UV light |