Background: On two occasions this year, the GIA Gem Trade Laboratory received for examination yellow metal pendants, each of which was mounted with a single carved gem material. The two carvings were similar in appearance, differing essentially only in size: one measured approximately 33 mm long x 22 mm wide, the other about 25 mm x 19 mm.
Visual Appearance: Both of the carved items were translucent, with a mottled, saturated green color. Our first impression was that they were fairly good quality jadeite jade.
Gemmological Testing: Our investigation using standard gem-testing methods was limited due to the mountings. However, each of the carvings produced spot refractive index values of 1.66 and revealed through the desk-model spectroscope an absorption pattern consistent with that of natural-color green jadeite, including a series of "chromium" absorption lines in the red end of the spectrum.
Magnification: Examination with a binocular gemmological microscope revealed that the items were actually composed of thin, hollowed out carvings that had been filled with a transparent, colorless substance. Using intense fiber-optic illumination, we noted that the filler contained small gas bubbles, at least a few of which could be seen through the tops of the carvings (in the smaller specimen, numerous gas bubbles could be seen just under the surface in the contact zone). The filler was also noted on the surface of the carvings at various points around their circumference and was exposed at one point where the thin shell of one of the carvings had a small chip. When probed with a sharp metal pin, the filler was easily indented. Using a millimeter gauge in conjunction with magnification, we estimated the thickness at the edge of the larger carving to be only 0.05 to 0.10 mm, while the outer shell of the small carving was only about 0.04 mm thick.
FTIR Spectroscope: Examination using Fournier-Transform Infrared Spectroscopy revealed strong absorptions similar to those of some polymers known to have been used in the impregnation of jadeite.
Discussion: Based on our examination, the items were identified as assemblages consisting of thin, hollow carvings of natural-color jadeite jade that were filled with colorless plastic.
Although these are the first such items we have encountered in the GIA GTL, we have previously examined thin, dark-colored jadeite that was mounted in closed-back settings, in which the backing had been highly polished on the inside to act like a mirror. This had the result of improving the apparent transparency and lightening the color to a pleasing tone. It is likely that the assemblages described herein were carved from similar, perhaps even darker-toned pieces of jadeite, the thin shells then filled with plastic to give them strength.
Source: GIA Gem Trade Laboratory, July 18, 1995