GENUINE nephrite jade is hard to come by these days, says art and antique dealer W.K. Chui. A beginner who wants to start a jade collection has to have deep pockets and should only buy from the most reputable auction houses and dealers overseas, advises Chui.
He does not know of any nephrite jade collector in Malaysia.
“Perhaps there are jade collectors here but they wish to remain anonymous. The biggest Chinese nephrite jade markets are Hong Kong, London and New York. Nephrite jade is available in China, too, but the auctioneers and dealers are not as honest as the other three markets mentioned earlier,” says Chui. “Even so, be very careful when buying jade in these markets because caveat emptor is still the name of the game.”
The potential buyer must read extensively and familiarise himself with the history of Chinese jade culture which dates back some 10,000 years.
“One can also train the eye by visiting museums, auction houses, private collections, exhibitions and reputable dealers,” he suggests.
The buyer also needs to learn the carving techniques of the different eras.
“Jade pieces from the Tang era are mainly low to mid relief and frequently with foreign figures. Song jade has multi-layered carvings, while typical Ming jade has two-layered carvings, especially for plaques,” he explains.
If the nephrite is genuine, one has to determine if the colours are artificially enhanced and aged to look ancient.
Chui offers some guidelines on how to avoid buying fake jade.
“It’s best to find someone who is knowledgeable to accompany you on a buying spree,” says Chui.
Often, we hear people talk about “injection jade,” a Cantonese term to refer to fake jade.
Chui explains that it meant colours can easily be added to jade via several methods such as heating, coating and diffusion.
Heating jade is a more common and modern treatment to dyeing jade.
“Heating jade causes the colour to lighten, darken or change completely; it also improves clarity and brightness,” explains Chui. “It is hard to detect a gemstone that has been heated to improve its look and grade unless analysed by trained observers in a laboratory. Heating is irreversible and allows for absolute manipulation of colour which can drive the price of jade higher than an unheated, less colourful stone.”
Coating is a dyeing technique used for over 200 years. Chui explains that it involves applying a lacquer or film to improve the general appearance of the jade. This can fill in fractures and alter the colour of the jade item. It is done carefully to fill in cracks so buyers cannot spot them.
Diffusion, Chui explains, is a dyeing technique which was originally used on sapphires. Today, it has been adapted for use on most gemstones. This technique also uses heat as the primary source of transformation. Chemicals added are said to penetrate the gem. The most common chemical used is beryllium.
Chui highlights two tests to check the authenticity of a jade item: the scratch test and the more scientific test.
Jade is a very hard stone, much harder than normal steel. (The hardness of steel is less than 5.0 on the Moh Scale). The scratch test involves scratching the jade with a needle or knife. If the metal object leaves a scratch mark on the jade, then it is not jade which has a hardness of between 6.0 and 7.0 on the Moh Scale.
The scientific test involves measuring the specific gravity (SG) of the stone. Nephrite has a SG of 2.90-3.02 whereas jadeite has a SG of 3.25-3.36. Specific gravity is measured using a formula that takes the weight in air and divides it by the weight in air minus the immersed weight. The immersed weight can be taken using a spring scale and tying the piece with thread, and immersing it in a beaker of water.
“These two tests can be easily carried out but they are by no means conclusive,” says Chui.
However, he says the best definitive tests are X-ray diffraction, refractive index and proton magnetic resonance spectroscopy.
“These tests are time consuming, difficult and expensive, and are reserved for testing very significant pieces found in royal tombs,” adds Chui.