gems, jade, jadeite, fei cui, Burma, assembled stones, treatments, B-jade, bleached and impregnated, dyed nephrite

JADEITE — Bleached and impregnated, with distinctive surface texture: The West Coast laboratory received for identification a 6.78-ct translucent, mottled-green cabochon that revealed properties typical for jadeite jade, with an R.I. of 1.66 (by the spot method) and an S.G. of 3.34. Chromium lines, seen with a spectroscope, proved that the green color was natural. The stone was inert to short-wave UV radiation, but some areas fluoresced a faint green to long-wave UV. The gemstone had an unusual, etched appearance in reflected light (figure 6): the aggregate structure of the cabochon appeared to be made up of many interlocking grains in various orientations, with certain grains preferentially eroded. Because of this surface texture, we suspected that the stone had been bleached and polymer impregnated. Infrared spectroscopy confirmed this treatment by revealing several peaks between 2800 and 3200 cm⁻¹; the relative positions and intensities of these peaks matched those of “polymer 5” in ICA (International Colored Gemstone Association) Laboratory Alert No. 75, 1993, issued by S. McClure and E. Fritsch. Therefore, we identified the stone as impregnated jadeite jade, natural green color, sometimes known in the trade as “B jade.” Interestingly, the S.G. of this stone was higher than that of most polymer-treated jadeites we have encountered thus far. JADEITE — Treated and untreated beads in one necklace: A comprehensive report on bleached and impregnated jadeite in the Fall 1992 Gems & Gemology (Fritsch et al., pp. 176–187) described features diagnostic of this treatment. The Lab Notes section has also reported on jade objects treated in this fashion, including entries on necklaces constructed of treated beads (see, e.g., Fall 1994, p. 187). Until recently, however, our testing had shown that all of the beads in these necklaces were treated. In November 1994, the West Coast lab was asked to identify a double-strand necklace with 69 beads (7.88–5.08 mm) on one strand and 74 beads (8.18–5.49 mm) on the other. Standard gemological testing proved that the translucent to semi-translucent, mottled green-and-white beads were jadeite jade. A desk-model prism spectroscope showed chrome lines, proving that the green color was natural. One unusual feature was noted during testing: some of the beads on both strands fluoresced a weak-to-moderate, mottled yellow to long-wave UV radiation, while others were inert. Most polymer-impregnated jadeite fluoresces. However, some untreated material may also fluoresce a weak yellow to long-wave UV. In our experience, we usually do not get such varied reactions from beads on one necklace. Further testing, using infrared spectroscopy, proved that there were treated (impregnated) and untreated beads in both strands. This was our first encounter with such mixed strands. Dyed green nephrite. Of the two jades (jadeite and nephrite), jadeite is much more commonly color enhanced (usually dyed green). Nevertheless, we occasionally find evidence of green dye in nephrite submitted for identification (see, e.g., Spring and Summer 1984 Gem Trade Lab Notes, pp. 48 and 108, respectively). In December 1994, the West Coast lab was asked to identify five oval, translucent, mottled-green cabochons, which ranged from 6.38 to 7.12 ct. All had an appearance similar to that of good-quality jadeite. However, standard gemological testing—including a 1.61 spot R.I. and an S.G. of 2.95 or 2.96—identified the five stones as nephrite. Magnification revealed dye concentrations (figure 7) like those seen in dyed jadeite and other similarly treated gem materials. The absorption spectrum observed with a desk-model prism spectroscope revealed a broad dye band in the red region, much like that seen in dyed-green jadeite and quartzite. In these stones, the diagnostic absorption band was centered at about 660 nm. All five specimens were therefore identified as dyed nephrite.