Gem News International Gems & Gemology, Summer 2014, Vol. 50, No. 2

Jadeite Bangle with the Appearance of Polymer Treatment

Larry Tai-An Lai

翡翠手镯呈现透明区域
Figure 1. This 244.29 ct translucent light to deep green and brownish yellow bangle measures approximately 70 × 14 mm. It contained a transparent, light-colored area that suggested the possibility of a polymer impregnation process. Photo courtesy of Lai Tai-An Gem Lab.
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.

Jadeite bangle revealing natural inclusions
Figure 2. Microscopic examination of the suspect area revealed natural inclusions and a crystalline form. Neither would be found in an impregnated specimen. Photo courtesy of Lai Tai-An Gem Lab.

Raman Spectrum
Figure 3. Sharp absorption peaks around 207, 347, 400, 465, and 990 cm–1 were consistent
with nepheline, a mineral sometimes associated with albite in jadeite.

Larry Tai-An Lai (service@laitaian.com.tw) owns the Lai Tai-An Gem Laboratory in Taiwan.