As the saying goes, “When it rains, it pours.” In this case, it’s pouring lizards. Recently, not one but two items resembling lizards trapped in amber were submitted to GIA’s West Coast laboratory for identification reports (see figure). Although the GIA Laboratory occasionally sees specimens with insects or animals enclosed in amber or amber imitations (i.e., plastic or copal), it is unusual to have two such pieces submitted within days of each other. Having both samples in the laboratory at the same time offered a special opportunity to examine the similarities and differences between two potentially rare specimens.

The first sample (58.14 × 35.75 × 24.41 mm; left in figure) contained a badly decomposed lizard with a broken tail and one foot missing. Microscopic examination between crossed polarizers revealed a narrow strain zone surrounding the lizard’s body. Gas bubbles and bits of fiber were also present, but these were inconclusive for determining whether the host material was amber, copal, or plastic. A spot refractive index (R.I.) reading of 1.55 was obtained – a bit high for amber, but still inconclusive. Nor was the fluorescence, which was chalky greenish yellow to both long- and short-wave ultraviolet (UV) radiation, sufficient to make an identification. The hydrostatic specific gravity (S.G.) was ~1.18. For confirmation, the piece was placed in a saturated saline solution (S.G. = 1.13), where it was observed to sink at a rate that was consistent with an S.G. of ~1.18–1.20. But since the presence of the lizard would affect the S.G. of the specimen, further testing was necessary.

The separation of amber from plastic or copal is gemologically challenging, because the easiest and most reliable tests are destructive. Therefore, the Laboratory decided first to analyze the sample with a Raman system using excitation from a 785 nm diode laser. The resulting Raman spectrum indicated that the specimen was neither amber nor copal, but rather a polystyrene plastic. All the gemological properties reported above were consistent with polystyrene. After consultation with the client, a small area of the sample was burned: The acrid odor confirmed this identification.

The second sample (74.5 × 31.9 × 25.32 mm; on the right in the figure) was more easily identified than the first. The lizard was in much better condition, having undergone markedly less decomposition. With magnification and reflected light, a separation plane was visible between the part of the sample below the lizard and the part above, clearly indicating that the specimen had been assembled. Microscopic observation also revealed numerous gas bubbles concentrated along this separation plane. The base of the specimen contained clouds, fractures, and various particles, whereas the upper portion showed a wide strain pattern, flow lines, and gas bubbles around the lizard’s body. The R.I. was 1.54 for the lower portion and 1.57 for the upper part. Both halves showed chalky greenish yellow to yellow UV fluorescence, but the lower half showed slightly stronger fluorescence when exposed to long-wave UV.

When the second sample was immersed in the saturated saline solution, it floated with the base up, suggesting an S.G. of ~1.10 for the upper portion – enough to flip the piece over while attached to the lighter base, but not to sink it. The base had been left rough and pitted, providing a surface on which to conduct heat and acetone tests where small blemishes would not be noticeable. When the pitted surface was burned, the odor was resinous and consistent with amber or copal. Application of acetone to a small area of the base softened the material and left the area slightly etched, a reaction consistent with copal. Both the top and bottom parts were analyzed using the 785 nm Raman system for comparison to the first sample. The spectrum for the lower half of the piece indicated amber or copal, whereas the spectrum from the upper half did not match amber, copal, or polystyrene. The R.I., S.G., Raman spectrum, and microscopic features were consistent with a plastic top, but not with polystyrene specifically. Thus, the final conclusion was that this second piece was an assembled specimen consisting of a copal base, a plastic top, and a lizard molded between.

These two items illustrate some of the means and materials that can be used to create imitations of creatures preserved in amber (see G&G's Winter 2005 Gem News International section, pp. 361–362, for yet another example). These circumstances also illustrate the ongoing need for gemological laboratories to develop effective nondestructive testing methods to supplement or replace traditional destructive tests.

Kimberly Rockwell
GIA Laboratory, Carlsbad, California