Gem News International Gems & Gemology, Spring 2020, Vol. 56, No. 1

Jadeite Jade and Serpentine Doublet

Jadeite jade and serpentine doublet carving.
Figure 1. This “jadeite jade” carving submitted for identification proved to be a jadeite jade and serpentine doublet. Photo by Lai Tai-An Gem Lab.

The Lai Tai-An Gem Lab in Taipei recently received a carving presented as jadeite jade. The rectangular, uneven green piece, carved on one side but almost plain on the back and sides, weighed approximately 171.01 ct and measured approximately 50.4 × 39.9 × 7.4 mm (figure 1). Standard gemological testing revealed a spot RI of 1.66 on an area of the carved side, but surprisingly the smoother surfaces failed to yield clear readings. Microscopic observation revealed a coating in the areas where the failed RI attempts were made.

FTIR analysis of the jadeite jade and serpentine portions of the carving.
Figure 2. FTIR analysis revealed absorption valleys at 1167, 1077, 962, 853, 665, 587, 529, 476, and 433 cm–1 in the jadeite jade portion (red spectrum) and valleys at 1001, 646, 557, and 460 cm–1 in the serpentine portion (green spectrum).

Subsequent infrared analysis proved the carved side was jadeite jade owing to the relevant absorption valleys observed at 1167, 1077, 962, 853, 665, 587, 529, 476, and 433 cm–1. However, the four sides and base revealed valleys at 1001, 646, 557, and 460 cm–1, characteristic of serpentine despite the surface coating observed (figure 2).

Before and after removing the coating.
Figure 3. Removal of the coating from the four sides and base exposed a clear boundary between the two materials (B and D). Prior to the coating’s removal (A and C), there were no indications the item was a doublet. Photos by Lai Tai-An Gem Lab.

The client granted us permission to remove the coating in order to analyze the item in more detail. After removal of the coating, the four sides and base showed a lighter saturation of green color separated by a visible horizontal line (figure 3, B and D). Before coating removal, the layering was not as obvious (figure 3, A and C). Magnification confirmed that the object was composed of two different materials. Standard gemological testing of the lighter colored material yielded RIs of 1.56, consistent with those expected for serpentine and supported by the FTIR and Raman analyses. Jadeite jade and serpentine can have a very similar appearance. The identification of this particular piece proved relatively straightforward, but if it were mounted in a closed-back setting with only the carved face visible, a costly identification error could easily result.

Larry Tai-An Lai ( operates the Lai Tai-An Gem Laboratory in Taipei.