AGTA GTC Laboratory Update
Orange-Pink Sapphire Alert
Pink sapphires with an artificially diffused orange color at or near their surface.
January 8, 2002 – According to the information presently available, already faceted pink sapphires from Madagascar are being coated in borax and heated at high temperatures in the presence of oxygen. This results is the production of an orange rim that penetrates the surface or near-surface areas of the gemstone only. When removed from the furnace the orange coloration is obvious (see Figure 1). The five treated stones to the right in Figure 1 show how these stones appear as they come out of the furnace, still coated with the remains of the borax (hence the fuzzy appearance) and with an obvious orange color.
Once cleaned and repolished the obviousness of the orange color is reduced. The stones then look pink with only a subtle orange color being present (a padparadscha color), see Figure 2. If they were repolished to a greater extent, this could remove the orange component completely.
The results of this treatment are similar to the results obtained for other surface diffusion treated corundum that have been on the market for some time. However, the orange color appears to penetrate a little deeper (see Figures 3, 8a and 8b) than, for example, the surface color in a blue surface diffusion treated corundum. In addition, the color concentrations normally seen at the facet edges of blue surface diffusion treated corundum are not observed in stones treated by this newer technique.
Dealers purchasing potential padparadscha colored sapphires should now examine these stones very closely.
- If the inclusion scene has significantly altered crystals or glassy residues present (see Figures 4, 5 and 6), and
- If when you lie the gemstone table facet down on a white background, an orange rim can be seen around the girdle (see Figure 7).
You may have a Madagascar pink sapphire with an artificially diffused near-surface orange color.
- If in doubt, the gemstone should be submitted to a gem laboratory for examination. The laboratory will immerse the gemstone in methylene iodide to observe the color distribution.
The AGTA GTC Laboratory Committee and The AGTA Industry Rules Committee have reviewed the situation and have concluded that the proper description for the stones described above shall be consistent with other surface diffusion treated stones. Therefore, AGTA Gemological Testing Center documents on faceted sapphires that have a padparadscha type color due to the describ ed artificially diffused 3-dimensional orange rim shall contain the following statements.
| Enhancement: | Enhanced by heat. Surface color diffusion1 |
| Species: | Natural Corundum |
| Variety: | Treated Sapphire |
| Comments: | Indications of heating. The orange coloration of this gemstone is confined to a surface-related layer. |
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| Figure 1. Ten untreated pink sapphires from Madagascar of the type used to produce the five treated orange-pink stones on the right. |
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| Figure 2. Following treatment the stones are cleaned and repolished. This removes much but not the entire orange rim. The resulting overall color is pink with a subtle orange – a padparadscha color. |
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| Figure 3. An example of the depth penetration of the orange color. |
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| Figure 4. Included crystal altered by the heating process. |
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| Figure 5. Included crystals altered by the heating process along with an expansion halo. |
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| Figure 6. Included crystal altered by the heating process surrounded by an expansion halo. |
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| Figure 7. Two treated stones placed table down on a white background show an orange rim around the girdle. |
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| Figure 8. When an orange color has been artificially diffused into the near-surface area only of a pink sapphire from Madagascar, this color distribution is seen as an orange rim that follows the 3-dimensional outline of the gemstone. This rim surrounds a pink center. The 4ct treated gemstone, seen here immersed in methylene, shows this color distribution. |
