Jadeite Classification and Identification
Taywiga Phataphol B.Sc., G.G.
There are three basic types of jadeite jade in the trade.
Type A is totally natural jadeite which is not treated with any chemicals except waxing after cutting and polishing. Waxing is not considered as treatment.
Type B is natural jadeite that is subjected to a strong acid to remove unwanted stains and followed by impregnating with polymer resin or paraffin. This treatment can improve luster and transparency of jadeite.
Type C is natural jadeite that is introduced by dye in order to improve pale colored jadeite.
In some cases, Type B jadeite is dyed by adding dye to the polymer filler. This jadeite type is called Type B+C
Figure 1: Sample of oval cabochon Type A jadeite.
For standard gemological testing, jadeite commonly shows refractive index 1.66 spot reading and specific gravity 3.34 (may be considerably lower due to albite content). To classify jadeite type, advanced instrument – FTIR spectrometer is required. As a polymer is an organic compound that FTIR is able to detect. This will indicate that jadeite is Type “A” or “B” jadeite.
Type “C” jadeite is examined by using spectroscope, microscope and Chelsea filter. Dyed jadeite commonly shows a wide absorption band in the red area when testing with spectroscope. Microscopic examination reveals dye concentrations in cracks as shown in figure below.
Figure 2: Type B Jadeite – showed a large peak located in the C-H region. This indicates the presence of polymer.
Figure 3: Dye concentrations in cracks.
Sometimes, dyed jadeite appears reddish under Chelsea filter. But, not all dyed jadeite have this reaction.
In conclusion, both of basic and advanced analysis are required for jadeite classification. The type of jadeite must be disclosed since it has an effect on its value.