Natural or Treated? Common Gemstone Treatments

Did you know that many gemstones are routinely treated (also called enhanced)?
These treatments are generally used to change or improve the color, clarity, or durability of a gem. Some gemstones are significantly more valuable if they are not treated, but treatments allow many more beautiful stones to be made available to consumers. It is important to understand treatments are not inherently “bad” but that legally,  they must be disclosed to the customer if they are not permanent, require special care, or if they affect the value of the stone.

Here are some of the most common gemstone treatments, why they are used, and a few examples of the gems that may be treated in this way.  Sometimes more than one treatment is used to achieve a desired result.

Process: Bleach
Why: Improve color
Examples: Pearls and jadeite jade are commonly bleached to remove undesirable coloring.


PEGFN103_a Pearls are commonly bleached (top) and are often dyed or irradiated (bottom)

Process: Dye
Why: Change or improve color
Examples: Stones such as lapis lazuli may be dyed darker blue to improve their color. White stones such as howlite or pearls may be dyed to resemble other stones such as turquoise or just to provide fun options for jewelry design.

Process: Fracture filling with dyes, glass, oils, polymers or resins
Why: Improve clarity and/or color
Examples: Emeralds are commonly fracture-filled to improve their clarity.

Process: Heat
Why: Change or improve color
Examples: Sapphires and amber are commonly heated to improve clarity. Tanzanite changes from brown to blue when heated and amethyst can be turned yellow and is sometimes then sold as citrine.

Process: ––Irradiation
Why: Change or improve color
Examples: Some gray pearls have been irradiated.  Colorless topaz is both heated and irradiated to create blue gems.

–Process: Stabilization/Impregnation with plastic, polymers or wax
Why: Improve durability and appearance
Examples: Soft stones such as turquoise, lapis lazuli and rhodochrosite are commonly stabilized.

Other treatments not covered here include high pressure high temperature (hpht), surface coating and lattice diffusion. You can learn more about these as well as the treatments above by clicking the GIA link below.

Code of Federal Regulations Part 23 – Guides for the Jewelry, Precious Metals, and Pewter Industries
Gemological Institute of America (GIA) – Gem Treatments

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