Lab Notes Gems & Gemology, Summer 2023, Vol. 59, No. 2

Plastic Imitations of Emerald

Emily Jones and Abadie Ludlam

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Figure 1. An imitation emerald in the form of a chess knight measuring approximately 35.05 mm in height. Photo by Kristin Reinheimer.
 
Figure 1. An imitation emerald in the form of a chess knight measuring approximately 35.05 mm in height. Photo by Kristin Reinheimer.
Figure 2. A closer look at the knight’s head (left, in daylight) reveals the material’s aggregate structure when viewed under long-wave ultraviolet light (right). Photos by Emily Jones.
 
Figure 2. A closer look at the knight’s head (left, in daylight) reveals the material’s aggregate structure when viewed under long-wave ultraviolet light (right). Photos by Emily Jones.

GIA’s New York laboratory recently examined two imitations, each submitted for an emerald identification report, that might have been convincing to the untrained eye. One was a chess piece weighing 46.55 ct (figure 1). At a glance, the knight appeared to be carved emerald with remnants of metallic yellow “matrix” still intact. However, the low heft and relatively warm feel of the piece suggested otherwise. Microscopic examination revealed an aggregate structure composed of jagged blocks, clearly illustrated under long-wave ultraviolet light due to its marked whitish fluorescence, typical of plastic (figure 2). The presence of gas bubbles and bluish dye concentrations indicated that the material was in fact an assemblage. The lack of a polished surface prevented a refractive index reading. Infrared and Raman spectroscopy were used to identify the main component as plastic; no beryl was detected. The metallic yellow crystal fragments were identified as pyrite, consistent with matrix associated with natural emeralds, notably those from Colombia.

Figure 3. An assemblage of plastic and various minerals imitating rough emerald in matrix, measuring approximately 51.79 mm in height. Photo by Michele Wong.
 
Figure 3. An assemblage of plastic and various minerals imitating rough emerald in matrix, measuring approximately 51.79 mm in height. Photo by Michele Wong.
Figure 4. Gas bubbles and bluish green dye concentrations indicate that this “crystal” is in fact a manufactured product. Photomicrograph by Abadie Ludlam; field of view 8.23 mm.
 
Figure 4. Gas bubbles and bluish green dye concentrations indicate that this “crystal” is in fact a manufactured product. Photomicrograph by Abadie Ludlam; field of view 8.23 mm.

The second imitation emerald (figure 3) was in the form of an elongated hexagonal “rough” emerald crystal embedded in a “matrix” of white and metallic yellow crystals, with a total weight of 179.71 ct. It too appeared natural to the unaided eye, but microscopic examination quickly distinguished the specimen as an imitation. The “emerald” portion of the rough contained large gas bubbles as well as bluish green dye concentrations (figure 4), an overall blotchy color appearance, and parallel surface striations. This material was identified as plastic using Raman and infrared spectroscopy. The surface striations were presumably created in the mold or carved to resemble the texture of a rough emerald crystal. Raman spectroscopy revealed that the smaller crystals mixed into the plastic were quartz and beryl. The white portion of the “matrix” was identified as calcite and the metallic crystals as pyrite, making this piece another convincing imitation of Colombian emerald.

The natural materials incorporated into these mostly plastic manufactured products might lead some astray upon first inspection. These two pieces demonstrate the need for a deeper inspection of all materials, regardless of how genuine they may seem on the surface.

Emily Jones is a staff gemologist, and Abadie Ludlam is a gemologist trainee, at GIA in New York.