Polymer-impregnated Jadeite

(via ICA Early Warning Flash, No.75, November 23, 1993) GIA GTL writes:

Background
Over the last several years polymer-impregnated jadeite has become prevalent in the jade market. This has given rise to some colors of jadeite being routinely tested for the presence of this treatment.

Recently, the GIA GTL in Santa Monica received for identification a 15 carat purple oval cabochon that we identified as jadeite. Subsequent testing determined the stone to be polymer impregnated. To the best of our knowledge, this is the first report of a jadeite of this color that is polymer-impregnated.

Polymer-impregnated ‘lavender’ jadeite
Gemological properties: Gemological testing revealed an index of refraction and visible absorption spectrum consistent with jadeite jade. Specific gravity was measured by the hydrostatic method and determined to be 3.32, which is slightly lower than the norm for jadeite. This is consistent with previous findings of polymer-impregnated jadeite. The stone was inert to longwave ultraviolet radiation. Magnification did not reveal any evidence of treatment. As is often the case with purple jadeite, the origin of the color could be be determined.

Infrared spectroscopy
The spectrum of this stone reveals intense absorptions around 2900cm¯¹ which are not found in natural jadeite. These additional features are due to the presence of an ‘opticon-like’ polymer. This is not surprising, since this type of polymer is the most commonly employed for jadeite impregnation, according to many reports and our own experience.

Discussion
This finding is particularly significant since none of the polymer-impregnated jadeite (or B jade) we have seen so far was purple in color. They have all been green or mottled green and white, some with applied spots of brown. This means that we will now have to expand our routine testing for polymer impregnation to include purple jadeites as well.

New polymers for jadeite impregnation
We have recently encountered two new types of polymer used for the treatment of jadeite, in addition to the three previously described which are wax, an ‘opticon-like’ polymer, and phthalate-like polymer. Since we do not know yet their exact nature, we will refer to them as polymer 4 and polymer 5.

Polymer 4
The infrared spectrum of polymer 4 is very similar—but not identical—to that of wax. In particular, the major absorption is slightly shifted and of different width than that for wax. Jadeites treated with this product do not ‘sweat’ when tested with the thermal reaction tester, as opposed to those impregnated with wax which do. We measured the SG of one stone showing this kind of impregnation at 3.33.

Polymer 5
The infrared spectrum of polymer 5 shows similar absorption features as polymer 4, plus five more in the range of 2950-3150 cm¯¹. The three jadeites impregnated with this material that we studied are inert in ultraviolet radiation. We could measure the SG on only one of them, and the stone floated in the 3.32 SG liquid (methylene iodide). It is interesting to note that two of these stones displayed ‘sweating’ when tested with T.R.T.

Conclusion
These two new polymers have been seen on a few jadeites submitted for identification, and laboratories involved in B-jade detection should be aware of them. They demonstrate the growing variety of polymers that are being used for jade treatment. One reason for this could be the increasing number of companies involved in this treatment.