Just as wood furniture needs to be lacquered, so too gemstones require finishing before they are ready to be sold. Critical as good cutting and polishing, treatments have become an integral part of the modern gemstone industry. Akin to aging fine wine, most of the techniques used simply facilitate the beautiful end results of the earth’s natural processes.

While these treatments are taken as commonplace within the industry, the general public’s awareness has been much lower. This page provides clear answers to common treatment questions. If you need any further information on treatments, please email support@mandicollection.com or alternatively access the guidelines provided by the U.S. Federal Trade Commission.

Is the use of treatments globally accepted? Yes, with close to 99% of the more popular gem types treated, all permanent techniques are universally accepted. As the majority of gemstones traded internationally have undergone some form of treatment, always assume treatment when purchasing gemstones. In fact, some techniques such as heating are centuries old – in all likelihood your grandmother’s ruby ring has been heat-treated!

Are all the treatments used permanent? mandicollection.com, with the exception of Emeralds that are treated with Colorless Oil or Polymers, only knowingly accepts treatments that are permanent and stable.

Why are natural gemstones treated? Most commonly used to improve the color or appearance of the finished product, some gemstones simply would not exist in salable quantities without treatment. For example, heating greenish brown Zoisite to 600 degrees Celsius produces the currently popular vibrant violet-blue Tanzanite. No heating, no Tanzanite! Please note that the term “natural gemstones” refers to those formed in the earth, whether or not they have been treated after mining – this is in distinct contrast to “lab”, “man made” or “synthetic” gems.

Does treatment affect a gem’s value? Interestingly, in some precious and semi-precious colored gemstones there is no variation between the value of treated and untreated material. In fact, treating may even increase a gems value. For example, when greenish brown Zoisite is heated to 600 degrees Celsius, an incredible metamorphosis takes place. Vibrant violet blue Tanzanite is created, commanding a far higher market price. However, high quality unheated Rubies and Sapphires are extremely rare and command a much higher market price. When purchasing high quality Rubies and Sapphires, please be aware that unheated material is almost non-existent, as a result, always purchase from a reliable supplier who guarantees their gemstones or have the seller’s claim verified by a qualified expert. For other people, treatments are a godsend, as they make expensive gems more affordable.

What gemstones are usually treated and how? The following table provides information on the treatments used for specific types, their purpose and frequency:

AGATE 
Dyed or Heated 
Used to alter color, these treatments are usually applied.

AMAZONITE
Colorless Wax, Oil, Hardened Resin
Used to improve the gems’ appearance, these treatments are usually applied.

AMETHYST
Heated
Used to lighten color and/or to remove smokiness, this treatment is only occasionally applied.

AQUAMARINE
Heated
Used to remove yellow components to produce a purer blue color with fewer yellow/green undertones this treatment is occasionally applied.

CITRINE
Heated
Usually applied, this treatment produces color.
CONTROVERSIAL SAPPHIRE

The AGTA and GIA classify this treatment as “bulk diffusion”. The GIT classify this material as natural corundum with the indication of heating where the orange coloration is confined to the surface layer.

Always applied, this treatment alters color by the external diffusion of coloring elements.

DIAMOND (ENHANCED)
Irradiated (Diamonds subjected to this treatment DO NOT become radioactive. This process exactly duplicates the natural exposure of gem crystals to radioactive elements during their formation. All Enhanced Diamonds sold at Thaigem.com are irradiated in the U.S. to certified international standards.)

Used to improve color intensity or to produce unique colors, this treatment is always applied for enhanced Diamonds.

EMERALD
Colorless Oil or Polymers
Usually applied, this treatment improves the appearance. If properly cared for this treatment is permanent. Click here to learn simple tips to keep your Emeralds looking great.

JADE (LAVENDER)
Dyed
Used to alter color, this treatment is usually applied.

MORGANITE
Heated
Commonly used, this treatment eliminates yellow overtones.

MORGANITE (GREEN)
Cobalt Heated
Always applied, this treatment induces vivid green color.

OPAL (DOUBLET)
Assembled Product
Always used, this treatment improves durability and/or color.

PEARL (CULTURED)
Bleached, Dyed or Chemically Enhanced
Usually used, these treatments improve color and uniformity.

PRASIOLITE
Heated
This treatment improves color and appearance and is usually applied.

QUARTZ
Heated
Usually applied, this treatment improves color.

RUBY
Heated
This treatment improves color and appearance and is usually applied.

SAPPHIRE
Heated
Usually applied, this treatment produces, intensifies or lightens color and/or improves color uniformity and appearance.

STAR SAPPHIRE (DIFFUSION)
Diffusion
Always applied for this type, this treatment produces an artificial star on a natural stone.

TANZANITE
Heated
Always applied, this treatment produces the violet-blue color for which the stone is known.

TOPAZ (EXCEPT WHITE)
Heated, Cobalt or Diffusion
Used to improve color intensity or to produce unique colors, this treatment is usually applied

TOURMALINE
Heated
Used to improve color intensity, this treatment is commonly utilized for blue green colors and only rarely applied for other color hues.

ZIRCON (BLUE & WHITE)
Heated
Used to improve color, this treatment is always applied.