Gemstones go through a series of processes—from the standard cutting and polishing to enhancement treatments—that transform the rough material into beautiful finished pieces to satisfy all types of customers. Jade is no exception to this. For centuries, producers have treated lower-quality jade to improve its marketability. This practice is still common today, and is accepted in the trade if full disclosure is respected, avoiding any kind of misrepresentation.
Enhancement treatments in jade seek to improve the stone’s colour, transparency, or stability. Even in the case of nephrite jade—which is seldom treated, as its structure rarely allows for dyes or resins—heat treatments may be used to improve the colour.
The main concern with all these treatments resides in the difficulty of their detection, as they rarely change the specimens’ refractive index (RI), specific gravity (SG), or hardness, which are the main tools most appraisers and jewellers rely on to identify a gemstone. The most reliable method to detect enhancements for both nephrite and jadeite jade is the use of fourier-transform infrared (FTIR) spectrometry and specialized lab equipment. For this reason, buyers in every stage of the value chain should require their suppliers to provide gemmological reports and certificates to validate the type and origin of traded pieces.
Another crucial factor for the jade trade is grading, which evaluates the quality of a piece regardless of its type or treatment status. As jade has been prominently marketed in Asia, Western markets have struggled to agree on a standardized process to grade the material. However, it is crucial to develop a clear system that allows transparent communication between buyers and sellers from anywhere in the world.
Gemstone grading aims to evaluate the different factors comprising a stone’s beauty. The effort to quantify a concept as subjective as beauty might seem impossible; however, with every gemstone, the main quality factors that contribute to a piece’s appeal are colour, transparency, cut, and clarity. In the case of jade, another factor is included: texture. A detailed description of how these factors are graded and their effect on a gem’s price would make a book unto itself. However, in this article, we would like to present a brief overview of the traits measured and treatments available in each category.
1. Color:
In gemstone grading, colour is the most important factor determining a gem’s attractiveness and marketability. In gemmological terms, colour is usually divided into three components:
hue (the ‘name’ of the colour, such as red, blue, or green);
tone (its lightness or darkness); and
saturation (its brightness or intensity).
Jade is mainly known for its green variety. However, both nephrite and jadeite are available in other hues. For example, jadeite can be lavender, yellow, black, white, red, orange, blue, grey, or even colourless, while nephrite can be found in white, grey, black, yellow, and brown. Both usually present unevenly distributed colouration, which make uniform vivid and medium-tone hues the most valuable ones, with pure green being the preferred colour.
The most common treatments impacting jade colour are bleaching and dyeing in jadeite and low-heat processing in nephrite. These treatments are not very reliable, and in some cases, they can bring out undesirable colours. The main concern with colour-treated pieces is the process compromises the stability and can be considered impermanent.
The impact on value of the jade piece here is twofold. The treatment can enhance value if the resulting colour is desirable in the market. However, a certified analysis of the piece can lower the value of the treated jade due to the aforementioned loss of stability and therefore lifespan.
2. Transparency and texture:
Chinese systems of jadeite evaluation measure ‘Zhong,’ or transparency and texture, to grade the quality of gem pieces. (See the second edition of R. Wise’s Secrets of the Gem Trade, published by Brunswick House Press in 2016.) These factors are closely related to the composition of jade stones, which are comprised of different microcrystals with varying degrees of uniformity. The finest specimens are those where these tiny crystals are evenly distributed, creating a smooth and soft look.
Jade transparency ranges from translucent to opaque. Neither jadeite nor nephrite can be fully transparent. However, the most desirable pieces present a high translucency that gives them a glass-like appearance. Jade texture refers to the smoothness and visual texture of the stone’s grain.
Wax coating to improve jade texture is a standard process observed in most A-grade pieces. It is widely accepted and has no impact on value. The main treatment to enhance lower-quality pieces is polymer resin impregnation, which is common practice in Asian markets and very difficult to detect if undisclosed. If unsure, buyers should either request a gemmological report or refer the pieces for further examination.
3. Cut:
Jade is usually cut into cabochons or carved into ornamental pieces. The quality of the cut is measured by the lustre achieved during the polishing process. Fine jadeite specimens can achieve a high glass lustre, which gives them the appearance of being wet and is enhanced by the transparency of fine material. Being softer than jadeite, nephrite jade undergoes less polishing and may present a resin or waxy lustre. Polymer impregnation can alter the polished look of finished pieces.
4. Clarity:
The last quality factor measured in jade is its clarity, which is determined by the absence of visible defects such as spotting, cottony or silky inclusions, and fractures. These characteristics influence the value of more high-quality transparent gems. However, inclusions can increase the value of nephrite if the presence of silk creates chatoyancy, giving rise to the most sought-after cat’s eye jade. Clarity enhancement is usually achieved with the same polymer impregnation process to deal with surface-reaching fractures, which would otherwise compromise the stone’s durability.
As noted previously, nephrite is seldom treated because its microscopic, nonporous, oil- and acid-resistant, ‘fabric-like’ structure rarely allows for dyes or resins. Heat treatments may be used; however, the comparative availability of nephrite over the rarer jadeite does not command manipulation for it to be placed in the market as a valuable gemstone. Its identity is almost always natural. Also, some heat treatments can actually reduce the stability of the mineral, as with tanzanite.
Conclusion
This article offers a brief overview of the five key characteristics of jade consumers consider when purchasing either jadeite or nephrite. As with all gemstones, personal preference and purchasing agenda influence how value is ascribed to jade items. Refer to Lucky Qi’s articles for more in-depth insights, detailed information, and analyses to help you better understand and make informed jade purchasing decisions.
By Samuel Michael Dilts, Laura Acosta Vidales và Andrew Loo - jewellrybusiness.com