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In the last few issues of the ICA Gazette, we have described GIA Gem Trade Laboratory policy relating to the detection of gemstone treatments and their description on identification reports. In those articles, we focused on how we address the treatment of specific gemstones: emerald, ruby and sapphire, and jadeite. These are all commercially important ge stones whose treatments have generated considerable debate within the gem and jewelry trade.
In addition to discus sions in the trade about the treatment of different gem stone varieties, there have also been proposals for an overall system to address gemstone treatment nomen clature, including the pro posed coding system cur rently being debated by the ICA.
An overall system for labeling gemstone materials, designed to ensure that information about treat ments is passed on at each level of the distribution pipeline, must be based on a framework of general cate gories of treatments. The definition of these categories is at the center of much of the debate on this issue.
In this article, we would like to present an overview of the general categories used by the GIA Gem Trade Laboratory in describing treatments on identification reports: cavity filling, frac ture filling, coating, luster enhancement, impregnation, diffusion treatment, dyeing, heat treatment, irradiation, and reconstruction.
CAVITY FILLING
The first general catego ry is cavity filling: the filling of surface-reaching cavities, pits, or other depressions in the surface of a gemstone with glass, plastic, or other substance or substances. The most commonly seen example of this type of treat ment is the filling of shallow surface-reaching cavities in corundum, usually ruby, with glass-like substances. This may occur as an inten tional treatment or it may be a by-product of heat treat ment: material used to fire coat a stone can fill cavities,
We have also encoun tered, in rare instances, plastic-like cavity fillings in emerald and ruby. It is quite possible that these fill ings in emerald represent excess polymer resin from fracture filling for clarity enhancement that has hard ened in wider cavities which are entry points for fractures.
When cavity filling is detected, a note is added to the conclusion of an identification report stating that a foreign material is present in surface cavities.
FRACTURE FILLING
The next category is the filling of surface-reaching fractures, cleavages, laser drill holes, and other voids with glass, plastic, or other substances. This category includes the treatment often referred to as "oiling" of emerald in the trade. Emerald and diamond are the two gem materials that in our experience are most often treated in this manner, although we have encoun tered other gems that have been so treated, including tourmaline, amethyst, gar nets, and tanzanite.
The generic statement that we use in the note to the conclusion when this treatment is detected is "Evidence of clarity enhancement is present."
It is important to note that the term "clarity enhancement" is used to describe this type of treat ment only in those instances when its use is unambigu ous, that is, when it is the prevalent, if not only, type of "clarification" process used on a gem material. Corundum is the primary exception, as heat treatment is also used to improve transparency by dissolving rutile "silk." When fracture filling is encountered in corundum, therefore, the note to the conclusion instead states that a foreign material
COATING
In our use of the term coating, we are referring to the application of a foreign colored substance to the sur face of the stone to alter its appearance. One example would be the application of a green coating to a pale-col ored beryl to give the appearance of a darker toned emerald. We have also encountered light yel low diamonds that have been coated with a pink sub stance to give the appear ance of a fancy-colored dia mond.
When this type of treatment is encountered and the base material can be conclusively identified, the main conclusion would read, for example, "color coated beryl" and a note would be added for clarification that "the coating prevents deter mination of the color of the base material." Sometimes, the coating will also pre clude the identification of the base material, in which case the conclusion would state that the item consists of a color coating on an unidentified base. To this conclusion we would add
LUSTER ENHANCEMENT
In contrast to the category above, luster enhancement is the application of an essentially colorless sub stance such as wax, paraffin, oil or lacquer to the surface or subsurface of a gemstone to improve the apparent lus ter or polish. While luster enhancement of transparent single-crystal gem materials is possible, in practice, we most often encounter it on aggregate gem materials where the colorless coating increases the overall bright ness of reflections from the surface. It may also have the added e
IMPREGNATION
Impregnation is the infusing of a gem material with a foreign substance such as wax, polymer resin, or plastic. Although this treatment has been used for many years to improve the appearance of porous and chalky-looking turquoise, impregnation has drawn much more attention and controversy over the past few years for its use on jadeite in conjunction with an acid bleaching process. Impregnation is also used on some types of opal, for example, porous material from Piaui state in Brazil, to improve apparen
When impregnation is detected, we describe the material in the conclusion of the identification report as, for example, "impregnated jadeite jade." In addition, in the case of jadeite, we add a note to the conclusion that reads "sometimes known in the trade as 'B' jade," in recognition that this term is in widespread use for this type of treated material.
DIFFUSION TREATMENT
Commercially used to date only on corundum, diffusion treatment employs high temperatures to diffuse compounds which cause color or asterism into a shallow surface layer of the stone. Unlike coatings, the diffused substance is actually incorporated into the stone's structure. The most often encountered use of this process is the introtion of a shallow layer of blue coloration into the surface of colorless natural or synthetic sapphire. Other colors have also been produced in small quantities, includi
When this treatment is detected, the material is described in the primary conclusion of the identifica tion reports as "diffusion treated natural sapphire" or "diffusion-treated synthetic sapphire." We add an explanatory note that the color or asterism is confined to a shallow surface layer that has been artificially pro duced by diffusing chemicals into the surface.
DYEING AND STAINING
Basically, this category includes all those treatments in which a colored foreign substance is introduced into a gemstone to produce or otherwise alter its color. A great number of gem materials may be enhanced by dyeing and, depending on the material, dyeing may be combined with other treatments.
If the treatment is simple dyeing of the surface of the material, this is indicat ed in the main conclusion of the identification report as, for example, "dyed jadeite jade."
Dyeing may be combined with clarity enhancement through the use of colored oils or resins. This is most often seen with beryl. This treatment would be disclosed on a report with a note added to the conclusion that reads "evidence of color and clarity enhance ment is present."
Dyeing can also be com bined with impregnation. In this case, the material would be described in the conclusion of the report as dyed and impregnated.
We also sometimes encounter gem materials in which color treatment is applied to localized areas of a gem material as part of its overall design. For exam ple, colored substances might be applied only to incised areas on jade or ivory carvings to highlight relief. To distinguish this from overall color treatments, this is described in a note to the conclusion that reads "areas of artistic staining are present."
HEAT TREATMENT
Heat treatment is the subjecting of gemstone material to elevated temperatures, the purpose and effects of which may vary with the material and specif ic procedure, atmosphere, and temperatures used. For example, heat treatment may be used to develop or improve color, such as blue or yellow in sapphire; to remove color, such as yel low in aquamarine or blue in ruby; to improve trans parency, such as dissolving silk in sapphire or removing gas bubbles in amber; or to induce asterism, as in corundum.
Depending on the specific material and application, heat treatment may involve temperatures as low as 100° C or as high as 2,000° C, or even higher. In practice, heat treatment can only be detected with any consis tency in corundum, because the temperatures used are much higher.
When evidence of heat treatment is detected, a note is added to the conclusion of the identification report that reads "evidence of heat treatment is present."
One exception to this heat treatment wording is the case of amber which is heated to produce the disk like fractures commonly referred to as "sun spangles." This type of heated amber is described in the main conclusion of the identification report as "sun spangled amber" and a note is added which explains that the sun spangles are induced by heating.
IRRADIATION
Irradiation treatment is the process of using high energy particles or electromagnetic waves to alter the color of a gem material. Some gems may have their color altered by relatively low-energy radiation, for example, the gamma-ray treatment of some tourma line to produce a red color or some beryl to produce a golden color. This type of treatment generally cannot be detected. However, higher-energy radiation treatments, such as the treat ment of topaz in a nuclear reactor to produce dark blue colors or
When such treatments are detected, the treatment is disclosed on identification reports using nomenclature that varies with the specific situation and isotopes detected, in accordance with GIA's licenses from the United States Nuclear Regulatory Commission and the State of California where we conduct such testing. Depending on the results of the testing, the material will be described as non-radioactive, slightly radioactive, or radioactive.
RECONSTRUCTION
Reconstruction is the process of combining several pieces of similar material with heat and/or pressure to produce larger pieces. Depending on the specific treatment method, a binding agent may or may not be used.
The only gem materials treated with this process are amber and some other less ancient natural resins. When this treatment is detected, the material is described in the conclusion of our laboratory report as, for example, "reconstructed amber."
CONCLUSION
This brief overview is a summary of the system used by the GIA Gem Trade Laboratory to describe gem stone treatments on identification reports. The system is comprehensive in that it provides a format for describing all known types of treatment that might be detected during a routine examination in the laboratory. It is important to note that we only include treat ment statements on reports when positive evidence of treatment is detected.
The system is also flexible in that the format pro ides for the disclosure of multiple treatments in those cases when they are present. Furthermore, the system provides consistency of approach as the nomencla ture used for all treatments describes them according to treatment process. In this latter respect, it differs from some proposed disclosure systems which describe some treatments by process, such as heat treatment, and others according to the sub stance used, such as oiling.
Source: ICA Gazette, June 1995