For the new corundum treatment coming out of Thailand

Over the past six months, significant numbers of pinkish orange to orangy pink sapphires have been entering the international gemstone market. The increased availability of this color variety of corundum is the result of a new treatment that is taking place in Thailand and being applied to certain colors and sources of corundum (e.g., pink sapphires from Madagascar and brownish red rubies from Songea, Tanzania).

These stones are being treated at high temperatures to produce a surface-related orange coloration. Examination of different samples that have been treated in this manner revealed that the surface-related coloration was usually restricted to a shallow layer; however, this layer may also extend to a considerable depth. The induced orange layer combines with the original color of the stone to produce the overall color appearance after treatment (shallow color layers produce an orangy modifier to the original color, whereas deeper color layers produce a more dominant orange appearance).

The surface-related orange coloration of these stones is reminiscent of the shallow coloration that is characteristic of blue and red surface diffusion treated corundum. However, certain features are different. The penetration of this orange color layer may be significantly deeper than what is seen with blue and red surface diffusion treated corundum. As a result, the outlining of facet junctions--which clearly identifies those types of treated corundum--is not observed in this new type of treatment. In addition, routine chemical analyses do not readily identify an elevated concentration of the color-causing elements (such as titanium or chromium) that are typically encountered in that material, although highly advanced analytical testing has produced indications that much smaller amounts of lighter elements (such as beryllium) may be responsible for the induced orange coloration.

After reviewing these facts and findings, the four laboratories unanimously agreed that it was imperative to devise a unified disclosure policy to address this matter, so that the existing atmosphere of uncertainty could be settled and the new treatment properly disclosed. Therefore, during the Tucson Gem and Mineral Show, the directors of the AGTA-GTC, GIA, Gübelin, and SSEF laboratories came together to formulate a unified terminology and disclosure policy.

Unified Declaration Policy
This unified terminology and disclosure policy applies only to those color varieties of corundum that reveal evidence of heat treatment and possess a surface-related orange color layer, as described above. There are two parts to the agreed-upon declaration policy. The first concerns the use of the name “padparadscha” and the second concerns the actual wording indicated on the laboratory report.

1. For the labs that apply the variety name “padparadscha” to those sapphires that display an orangy pink to pinkish orange face-up appearance: The name “padparadscha” will not be applied to these newly treated stones.

2. On all reports for these treated sapphires, the following statements will be made:

Species:   Natural Corundum

Variety:   Treated (Orange) Sapphire

Comments/Treatments: Indications of heating.

The orange coloration of this stone is confined to a surface-related layer.

POSSIBLE QUESTIONS AND ANSWERS

Why not call it “padparadscha”?
We believe that this new treatment has been applied to imitate a “padparadscha”-like color appearance. However, because the orange component is confined to a surface-related layer, these stones should not be identified as the color variety ”padparadscha.”

Why the sentence under the Comments section of the report?
It is vitally important that the report clearly establishes that the orange coloration is confined to a surface-related layer. This is significant for two reasons. First, this new form of orange coloration is distinctly different from the orange color zones that may result in the interior of sapphires subjected to traditional types of heat treatment, as well as from naturally occurring orange color zones that may be encountered in non-heated sapphires. Second, the buyer or owner of the stone must fully understand that if the stone is re-cut for any reason, the color is likely to change.

Why the term “Treated Sapphire”?
The term “treated” has been applied before “sapphire” for sapphires that have been surface treated, so they may be easily separated from those that do not owe their color to a surface-related layer.

Will all heated orange/pink stones be reported in this manner?
No. Those stones that have been subjected to traditional heating will be disclosed according to the traditional/standard policies of each lab. Such stones will not have the word “treated” in their description; nor will they be subjected to the additional comment.

Why not the term “Diffusion-Treated”?
None of the agreeing laboratories knows of a likely mechanism that could produce these visual effects or apparent differences in trace-element concentrations from the rim of the stone to the interior, other than diffusion of a chemical or chemicals into the surface of the stones.  Nevertheless, as the trade usage of the term “diffusion” without any qualifier (such as the inadvertent dropping of the word “surface,” hence “surface diffusion” – see the CIBJO rules) has, upon analysis, been found lacking both in terms of technical accuracy and descriptive purpose, it has been decided to remove the term from our report wording in relation to this treatment.

Does the penetration depth of the orange color alter the report wording?
No. If any amount of pink is seen to be present under the overlying orange, the same report wording applies.

In terms of the ICA “NET” system, where do these new treated sapphires fall?
They fall in the T category.

Feb. 26, 2002