Lab Notes Gems & Gemology, Summer 2016, Vol. 52, No. 2

Unique Drilled Emerald

Emerald with two drill holes
Figure 1. This 3.39 ct emerald (8.91 × 8.87 × 7.61 mm) is moderately clarity enhanced, obscuring two drill holes (not visible in this photo). Photo by Sood Oil (Judy) Chia.

A 3.39 ct emerald, as confirmed by standard gemological testing, was received by the New York lab (figure 1). At first glance it appeared to be a typical emerald with moderate clarity enhancement. It was categorized as F2, indicating that the fracturing present in the stone had a noticeable but not significant effect on the face-up appearance. Further microscopic examination of the pavilion revealed two prominent drill holes filled with a resin and emerald fragments (figure 2). The resin displayed a blue and yellow flash effect, and gas bubbles trapped in the resin were also present (figure 3). The filler had much higher relief than the emerald host and was clearly visible under reflected light due to the difference in luster between the two materials (figure 4).

Drill hole under microscope.
Figure 2. With microscopic examination, the circular outline of the drill hole is apparent on the pavilion facet of the emerald. Photo by Edyta J. Banasiak; field of view 4.08 mm.
Flash effect in emerald.
Figure 3. This drill hole shows a blue and orange flash effect along the interface between the emerald and the resin filler. Photo by Edyta J. Banasiak; field of view 3.57 mm.

The question arose as to why such a treatment would be performed on this stone. Microscopic observation did not yield any clues. One hypothesis would be that eye-visible inclusions were removed by drilling, analogous to the laser-drilling treatment well known in diamonds. Assuming this theory is true, the “enhancement” actually significantly reduced the value of this good-quality emerald. We concluded that the stone contained a resinous material in the drill holes along with emerald fragments. This was the first time GIA’s New York lab had witnessed this type of enhancement in an emerald.

Drill hole in reflected light
Figure 4. Examination of the drill hole in reflected light shows an emerald fragment intentionally placed in the opening, presumably to conceal the hole. Note the luster difference between the emerald and the resin filler. Photo by Edyta J. Banasiak; field of view 3.57 mm.

Edyta J. Banasiak is a staff gemologist at GIA in New York.