Jadeite Bangle with the Appearance of Polymer Treatment
Jadeite jade always comes under close scrutiny in the market because it is so frequently treated. The treatment options for jadeite jade are numerous: bleaching, dyeing, polymer impregnation, or a combination of these. Polymer impregnation is a particular favorite, a process that is not always easy to observe by magnification. A 244.29 ct translucent light to deep green and brownish yellow bangle measuring approximately 70 × 14 mm was recently submitted to the Lai Tai-An Gem Lab in Taipei. The client was concerned about a more transparent light-colored area (figure 1) that appeared to be possible evidence of impregnation.
Standard gemological testing indicated a spot RI reading of 1.54 at the more transparent light-colored area and 1.66 elsewhere on the bangle, an SG of approximately 3.32, and a characteristic jadeite spectrum exhibiting a band at about 437 nm. FTIR and Raman spectroscopy were also applied, producing spectral features that confirmed the bangle’s identity as jadeite jade. Microscopic examination revealed natural inclusions within the transparent area that appeared to be polycrystalline (figure 2). Neither would be seen in an impregnated specimen, ruling out this treatment. Further analysis with Raman microscopy was conducted to identify its true nature.
Sharp absorption peaks at around 207, 347, 400, 465, and 990 cm–1 were a match for nepheline (figure 3), a mineral sometimes associated with albite in jadeite. The nepheline crystal remained intact during the fashioning process, and its presence led to confusion over whether the bangle had been treated.