Recently, a type of black jade has appeared on the market—entirely black and nearly opaque. Because its appearance closely resembles that of ink jade, merchants often sell it as ink jade.

According to the national standards GB/T 16553-2017 “Jewelry and Jade—Identification” and GB/T 38821-2020 “Hotan Jade—Identification and Classification,” ink jade refers to Hotan jade whose main body color ranges from grayish-black to black, colored by graphite, and in which the black portion accounts for at least 30%.

During the identification process, the gemological inspectors from the China National Gemstone Testing Center found that this black jade exhibits significant differences in gemological characteristics from ink jade. Under a gemological microscope, no microscopic graphite particles were observed. Under long-wave ultraviolet light, the sample displayed an unusual fluorescence response (as shown in Figure 1). After cutting the sample open, the outer layer of the cross-section was black, while the inner layer was white (as shown in Figure 2). Comprehensive analysis using infrared spectroscopy, Raman spectroscopy, UV-Vis spectroscopy, X-ray fluorescence spectroscopy, and X-ray powder diffraction revealed that the black jade sample is primarily composed of tremolite, with minor amounts of other minerals. No graphite was detected in the sample.

Figure 1

Figure 2

In summary, this black jade is not colored by graphite but rather by artificial treatment applied at a later stage. According to the national standard GB/T 16552-2017 “Names of Jewelry and Jade,” it should be designated as “Hotan Jade (Treated)” and accompanied by the note: “Color has been artificially treated.”

As technology continues to evolve at an unprecedented pace, innovative methods for enhancing jewelry and jade are emerging one after another. We would like to remind all industry professionals and consumers to remain vigilant at all times and avoid falling into traps. The National Gem and Jewelry Testing Center closely monitors new market trends and, as always, provides scientific, accurate, impartial, fair, and efficient technical services to promote the healthy development of the jewelry and jade jewelry industry.

Contributors: Feng Xiaoyan, Deng Qian

Photography: Deng Qian

Contributing Unit: Beijing Branch of the China National Gemstone Testing Center (CGTC)