Jade has been revered since the Stone Age, especially in China where it was associated with royalty. According to the Gemological Institute of America (GIA), the character for jade is one of the oldest in written Chinese. Confucius wrote that jade is like virtue and its brightness represents heaven.
To see ancient Chinese jade carvings, visit the Colors of the Universe: Chinese Hardstone Carvings exhibition at New York’s Metropolitan Museum of Art. According to a review on the GIA web site, Colors of the Universe showcases 75 of the finest examples of Qing dynasty lapidary art and includes carvings in jade, agate, quartz, malachite, turquoise, amber, coral, lapis lazuli, and other hardstones. (Wikipedia defines hardstone as “an unscientific term, mostly encountered in the decorative arts or archaeology, that has a similar meaning to semi-precious stones, or gemstones.)
Jade carvings from the Heber R. Bishop Collection include the large “Boulder with Daoist Paradise,” an example of yu shan or “jade mountain” and the even more massive “Jade Basin,” modeled after the famous original in Beijing’s Beihai Park Imperial Garden, believed to have been commissioned in 1265 by Kublai Khan. The original is one of the most famous of all Chinese jades. In the mid-1700s the Qianlong Emperor recovered it from priests in a Daoist temple who were using it to store pickled vegetables. The emperor was so enthralled by this jade basin that he wrote three poems about it, had them inscribed inside, and erected a pavilion to display his treasure. Read the full review here. Colors of the Universe: Chinese Hardstone Carvings will run until until October 9, 2017.
Jade is actually two minerals, jadeite and nephrite, jadeite being the more rare and valuable. Today there are three classes of jadeite jade which differ in value, one of which is chemically treated and resin impregnated to enhance its translucency. The acid wash treatment removes unwanted material, but may damage the structure of jadeite causing it to lose its lustre over time. The resin fills the voids, and is formulated to match the jade closely, making it difficult to identify by optical microscopy. Other long-term issues include skin burns from residual acid and discoloration of the epoxy resin.
Standard microscope examination may not reveal the resin treatment, and in fact treated jade often passes most of the normal testing done by a jeweler. Fourier Transform infrared (FT-IR) spectroscopy provides an excellent tool for analyzing natural and treated jade. Signals due to the wax or epoxy resin are quite definitive. The analysis takes only a few seconds, and the procedure yields clear results. Similar analyses of diamonds and other gemstones can also be accomplished with FT-IR spectroscopy. To learn more, read Gemstone Analysis by FT-IR: Identifying Treated Jades.