Disclosing Emerald Treatment

RAPAPORT…

During the past few years, emerald has become an increasingly popular colored gemstone. Sales of the green gem are catching up to those of ruby and sapphire, and its popularity is booming in the U.S., Europe and even more so in Asia. Thanks to a steady supply of high-quality stones, mainly from Colombia and Zambia, the ever-increasing demand can be fulfilled. Strict testing and reporting by gem labs has helped to build confidence in the market and to make the emerald a safe buy. Consumers can rely on lab reports that disclose the one type of commonly applied treatment, the filling of fissures with a foreign substance to enhance the clarity and transparency of the stone.

Naturally Formed Fissures

Fissures are mostly the result of the formation of emeralds in nature, typically related to geological events such as movements in the earth’s crust. During and after growth, the emerald may experience significant mechanical strain, resulting in fissures and fractures throughout the stone. These fissures affect the transparency of the stone to a certain extent, depending on their number and extent (see example in Figure 1, on opposite page).

By filling these fissures with a foreign substance, such as oil, resin or wax, the transparency of the emerald can be enhanced (see Figure 1, left). The detection and quantification of this man-made clarity improvement, or “make-up,” is done by gem labs, and is disclosed on gemological reports.

Clarity Enhancement

Today, most reputable labs apply a grading system to quantify the degree of clarity enhancement, ranging from “insignificant,” “minor” and “moderate” to “significant.”  The end consumer is then able to make an educated decision on what he or she is buying, as the report indicates the amount of enhancement that has been applied to the stone (see Figure 2, horizontal axis, above).

Only a very small percentage of emeralds show no indication of clarity enhancement. These are either “natural beauties,” i.e., they are naturally free from fissures (see top left stone in Figure 2), or fissures are present, but they do not contain any filling material. This absence of any foreign substance in the fissures again has two possible explanations: Either the fissures are pristine, i.e., they have not been filled to date, or the fissures have been cleaned to remove filling material that was introduced at an earlier time. The latter is far more common, as most emeralds are routinely treated with some kind of clarity-enhancing material shortly after mining.

Multiple Treatments

The clarity enhancement of emeralds is a reversible and repeatable process and stones may be filled and cleaned multiple times during their “life” as a gemstone. This is especially true when oil is used as a filling agent because oil dries out over time and it can leak out when heated or when surrounding air pressure is changed. Oil also is more easily and safely removed. But generally, all types of filling material, including epoxy and resins, can be removed. Consequently, consumers must be aware that an emerald could potentially be treated again after being tested in the lab and receiving a gemological report.

If clarity-enhancement treatments are applied to an emerald with a high density of fissures, the appearance of the stone changes dramatically. Figure 1 and the bottom row in Figure 2 emphasize this changing appearance. Most labs — including Gübelin — add a clause in the small-print statement addressing this limitation of the report’s validity and noting that it may not reflect treatments done after the stone was tested by the lab.

The end consumer, however, might want more protection beyond the laboratory report. Buying from a trustworthy source is recommended, and ensures that a stone can be returned if necessary. In addition, the Gübelin Lab has taken a further step toward protecting the final customer, by judging the susceptibility of a stone to clarity enhancement. In this step, an emerald with fissures is declared “susceptible” to a clarity-enhancement process, whereas an emerald without fissures is not, as there are no fissures to receive a clarity-enhancing agent. Obviously, a fissure-free emerald does not require any clarity enhancement.

A brief comment by the laboratory about the presence or absence of fissures is especially helpful for a stone that has no indications of clarity enhancement at the time it is tested. This gives clients either peace of mind, or alerts them. If the emerald is free of fissures (see example in Figure 2, stone at top of left column), the customer gets complete assurance that the stone is not susceptible to any clarity enhancement, and that it is one of the very rare specimens of emerald that is free of fissures. On the other hand, a statement that mentions the presence of fissures (see the examples in Figure 2, i.e., the four stones in left column, excluding the top fissure-free stone) and the predisposition for treatment draws the customer’s attention to the possibility that the emerald might be clarity enhanced, in spite of a gem lab report stating the opposite.

The Gübelin Gem Lab’s emerald report traditionally has contained a comment about the absence or presence of clarity enhancement. That practice continues. More recently, for every emerald that does not show any indications of clarity enhancement, the lab had included an additional comment on the report plus a note on a separate page indicating either that the stone is without fissures or the stone has fissures. These notes (see box, at left) distinguish the two different types of emeralds: One note addresses the rare emeralds without fissures; the other note emphasizes the possibility of subsequent clarity enhancement. The intention of this new service is to supply the end consumer with additional information that is considered relevant and critical in making an informed buying decision, and also to protect the credibility and sustainability of the emerald market.

Sample of note concerning fissures and clarity enhancements attached to a report on an emerald without any fissures by the Gübelin Gem Lab.

The formation of emeralds in nature is related to tectonic events affecting the rock in which the emerald is forming. The developing emerald experiences significant mechanical strain, resulting in fissures and fractures throughout the stone. In most cases, this process lowers the transparency of the stone, depending on the number and extent of the fractures.

Only a very small number of emeralds are not affected by this natural process. Thus, emeralds with only very minute fissures or no fissures at all are true rarities and deserve special notice. The absence of fissures makes them immune to any enhancement of the clarity by filling the fissures with a foreign substance such as oil, resin or wax. The emerald described in Gübelin Gemstone Report No. 1234567 is one of those rare specimens.

Sample of note concerning fissures and clarity enhancements attached to a report on an emerald with fissures by the Gübelin Gem Lab.

The formation of emeralds in nature is related to tectonic events affecting the rock in which the emerald is forming. The developing emerald experiences significant mechanical strain, resulting in fissures and fractures throughout the stone. In most cases, this process lowers the transparency of the stone, depending on the number and extent of the fractures.

By filling these fissures and fractures with a foreign substance such as oil, resin or wax, the transparency of the emerald can be enhanced. Such a clarity-enhancement process is usually reversible and repeatable at any time. At the time of the analysis mentioned on the Gübelin Gem Lab Report, the emerald described in Gübelin Gemstone Report No. 9876543 did not show any indications of clarity enhancement.