A Quick Guide to Gemstone Treatments

Treated gemstones are natural, they’ve just been enhanced to display the best color or clarity. That doesn’t mean that they should be sold as natural without explaining why they have their special sparkle and color. In fact, it’s a law that anyone selling a gem must disclose the treatment procedure it received. Full disclosure of gemstone treatments isn’t just a matter of obeying the law; it’s about the ethics and obligations of a jewelry professional.

You can buy gemstones and diamond jewelry with confidence at Jewelers of America Member jewelry stores, because they pledge that they will:

  • fully and accurately disclose the material characteristics of the products and merchandise they sell
  • conduct business with honesty, sincerity, truthfulness, integrity and transparency

You should feel comfortable asking about any gemstone enhancements, their stability (whether permanent, long lasting or short-lived), and any special care required. A trustworthy jeweler will explain all of this to you. Gemstone grading reports or receipts from the jewelers should also include details regarding the gem treatment.


Common Gemstone Treatments

Let’s cover common diamond and gemstone treatments, so that you can better communicate with your jeweler when shopping for gemstone jewelry:

Bleach – chemically treated (hydrogen peroxide) to alter or remove color, and is practically undetectable, even to the trained eye. Used for pearls and jadeite jade.

Diffusion – heat treating a stone and adding other elements, like beryllium, to permanently enhance its color. Most often seen with corundum, which are rubies and sapphires. This treatment is not always the most stable, and can fade with time and exposure to certain elements.

Dye – a process that dates back to the first century A.D. and is most often used on lower quality pearls but also turquoise, black onyx, lapis lazuli, chalcedony, emerald, quartz and ruby. Dyes can fade over time or alter, so do not expose to acetone, rubbing alcohol and prolonged direct sunlight (like a day at the beach).

Filling – process of filling small fractures or cavities in the gemstone, with glass, resin, oil or wax to smooth surface and enhance clarity. Seen in diamonds, rubies, emerald and sapphires. The enhancements is not permanent. Avoid high heat, hot water, changes in air pressure and household cleaners, which can potentially alter the filler.

Heat – gems exposed to high temperature to permanently alter their color. One of the most common gemstone treatments; for example, over 95% of all rubies on the market today are heat-treated. In most cases the treatment improves the gem’s apparent color and/or clarity. Traditional heat treatment results in a very durable gem requiring no special care or handling issues. Common heat-treated gems include amber, amethyst, aquamarine, citrine, ruby, sapphire, tanzanite, topaz, tourmaline.

High Heat High Temperature (HPHT) – used for diamonds. Changes brown diamonds permanently to colorless, or to yellow, orange, blue. Colored diamonds treated this way are not considered Natural colored diamonds.

Irradiation – using small doses of radiation to physically alter the gemstone’s color permanently. Blue topaz is achieved through irradiation combined with heat treatment. Irradiation may also treat sapphires, quartz, and colored diamonds (like black, green, blue, yellow and red).

Oil – treatment for gemstones with surface inclusions, like emeralds. The oil smooths the surface and improves clarity. This treatment is not permanent and care must be taken to avoid ultrasonic cleaning techniques. Take this gemstone jewelry to your jeweler for professional cleaning instead.


Determining Gem or Diamond Treatments

Qualified laboratories test gemstone and diamonds for known treatments and issue reports of authenticity. Look for “natural” which means no treatments have been made, “Treated” or “Undetermined” if the lab cannot determine the original color.


Source: Jewelers of America