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 Heat Treatment at About 400 C(750 F)
This is a traditional method that is used, for instance, to remove a greenish hue from aquamarine. It causes no changes to the interior of the gemstone crystal. |
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Mogok
Ruby |
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Sri Lankan
Sapphire |
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Mong Hsu
Ruby |
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Sri Lankan
Sapphire |
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Heat Treatment at 1,600 -1,900C(2,910-3,450F)
An example of this treatment is the high-temperature treatment of Mong Hsu rubies to remove a blackish color and make them a beautiful red. The treatment is permanent, but negative results, such as impurities entering fractures or a weakening of the crystal, may occur. |
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Zambian
Emerald |
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Emerald
Treatment:Moderate |
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Emerald
Treatment:Significant |
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Oil- or Polymer-
Impregnation Treatment
This treatment masks defects by filling surface-reaching fractures with oils or polymers. It is seen in emeralds and many cabochon-cut gemstones. The treated gemstone's color may fade with time, and surface-reaching fractures may become noticeable. Gemstones that are treated to hide defects have an inherently low value. |
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Irradiation-Treated
Blue Topaz |
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Diffusion-Treated
Sapphire |
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Irradiation Treatment and
Other Treatments
Treatments such as the irradiation treatment of blue topaz and the diffusion treatment of certain corundum use natural materials. However, they have virtually no value as gemstones. |
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