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These large faceted samples approxi-
mately 13.6-16.3 cts.) proved to be
beryl triplets. Photo by S. Singbamroong.
© Dubai Gemstone Laboratory.
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The Dubai Gemstone Laboratory recently received five large (approximately 13.6–16.3 cts.) transparent green emerald cuts for identification (figure 1). The client who submitted these samples prior to purchase had been informed that they were good-quality emeralds from Colombia.
The following gemological properties were obtained:
- RI – no=1.588–1.596 and ne=1.570–1.578
- Hydrostatic SG – 2.69–2.71
- Fluorescence – inert to both long- and short-wave UV radiation
- Chelsea filter – green reaction
- A smudgy band in the red region of the spectrum seen with a desk-model spectroscope.
These properties were consistent with emerald except for the absence of chromium lines in the absorption spectra, which prompted a more detailed investigation of the cause of color.
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Immersion in benzyl benzoate with diffused transmitted light readily revealed the layer of green cement between the two pieces of near-colorless beryl in this triplet. Photo by S. Singbamroong.
© Dubai Gemstone Laboratory.
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Observation of the samples in profile view with diffused transmitted light showed green crowns and colorless pavilions, which established that they were assemblages. Microscopic examination of both halves revealed the two-phase (liquid and gas) inclusions, "fingerprints," and parallel growth tubes that are typical of beryl, as well as small flattened, rounded, and irregularly shaped gas bubbles along the separation plane in each of the assemblages. Examination with immersion in a direction parallel to the girdle plane proved that the samples were triplets composed of two pieces of near-colorless beryl (crown and pavilion) held together by green cement (figure 2).
FTIR spectroscopy performed on all samples (through the crown and pavilion) revealed features that were very similar to those of some synthetic resins used in the fracture filling of emerald.
The properties of these samples were consistent with those reported for beryl assemblages that have been produced by the firm Kämmerling of Idar-Oberstein, Germany, since 1966 and marketed under the trade name "Smaryll." Beryl doublets and triplets have been used to imitate emerald since the early 20th century; though less common today, they still continue to show up in the marketplace.
Sutas Singbamroong and Moza Rashed Al Falasi
Dubai Gemstone Laboratory
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