The challenges involved in identifying carved objets d’art are different from those encountered with a faceted gemstone. In particular, depending on the shape and artistry of the carving, delicate handling and special dexterity are required to perform standard gemological tests. This was certainly the case as the West Coast lab examined an intricately carved statue of an Asian woman (see illustration) that was submitted this winter for identification.

We were quite intrigued by the carving, which had been labeled as “rare jade.” The figure itself measured approximately 12 × 5 × 2 cm, and was carved out of a single massive piece of translucent to semi-translucent purplish pink material with some areas of green coloration. The carving was beautifully finished with a very high polish. As is customary with such carvings, however, the flat base, designed to rest on a tightly fitting carved wooden stand, was left unpolished.

Consequently, we could obtain a refractive index reading only by using the spot method on a carved part of the figure; a small area on the back of the statue yielded a reading of 1.71. This value is too high for either nephrite or jadeite jade.

Other standard gemological tests did not provide any diagnostic information. There was no fluorescence to either long- or short-wave UV radiation, and the absorption spectrum did not show any characteristic features. Because of the size and delicacy of this statue, we could not obtain an accurate specific gravity determination. Instead we turned to laser Raman microspectrometry, which gave a spectrum that matched the reference we had for grossular garnet. Because this translucent material showed a low refractive index, below the lower end (1.73) of the normal range for grossular, we identified it as hydrogrossular garnet. As the name implies, hydrogrossular is the water-bearing member of the garnet group, typically occurring in the massive form (R. Webster, Gems, 5th ed., 1994, Butterworth-Heinemann Ltd., Oxford, pp. 202–203).

Hydrogrossular is used only rarely as a carving material, and it occurs in pink hues even more rarely. However, this contributing editor recalled two similar items previously reported in the Lab Notes section: a carving of massive green grossular (Spring 1985, p. 44), and a strand of pink and green grossular beads that were also presented to that client as “rare jade” (Summer 1982, p. 103). KH

Karin Hurwit
GIA Gem Trade Laboratory
Carlsbad, California

Photo by Maha Tannous