Gemstone Treatments ~ an information page provided by Northwest Jewelry

What do you think when you hear a gemstone has been treated in some fashion? Does it make you hesitate to buy? Do you think the stone is not genuine or natural once it’s been treated? Are you worried that the treatment won’t last or that it will negatively affect the value of your gemstone?

These are fair questions, and a buyer should have these answered before buying any loose gemstone or finished piece of gemstone jewelry. Treatments are also known as enhancements, but the FTC (Federal Trade Commission) considers “treatment” a more accurate term than enhancement.

The truth is, all treatments are not considered equal! Many of the most common, popular gemstones are routinely treated, and these treatments are not only permanent, they also enhance the stone’s appearance, color, clarity, luster or durability. Other treatments are not as well thought-of, and although a stone purchased with these types of treatments may be a great buy, you should be notified by the seller of the treatment so that you can make an informed decision.

The bottom line is that gemstone treatments can make some gemstones much more available and affordable to the general public. The key is disclosure by the seller and an informed buyer.

Why are gems treated? A finished gemstone goes through many processes before it comes to you as a beautiful, finished stone. It starts out in a piece of “rough”, which is the form it is in prior to being cut, faceted, and polished. All rough is not the same quality and color, and most gemstones require some additional treatment to help them become a consistent representative of their species.

Heat treatment:
Heat treatment is one of the oldest processes and is probably the most widely used today. It is generally considered to be a stable treatment, and for some stones, is absolutely necessary to make them marketable. Tanzanite is a good example of this. It starts out as a nondescript brown color, and only by heat treatment does its beautiful purples, blues, and violets emerge.

Almost all corundum (sapphires) are heat-treated. Those that aren’t are extremely valuable and rare. Other stones commonly treated with heat are aquamarine, zircon, topaz, and amber.

Although dealers should notify customers if a gemstone is heat-treated, it is often assumed the customer is aware of this because of the commonness of the process. If you have questions about whether a piece you are considering has been treated with heat, ASK!

Fracture-filling:
This is another very common treatment where a gemstone’s fractures are filled with a colorless substance that closely matches the refractive index of the gem. Some types of fillers are oil, resins, polymers and glass.

Emeralds are an example of a gemstone which is almost always enhanced by fracture-filling. Emeralds are not as hard as diamonds, corundum, or other gemstones commonly used in jewelry, and they are often damaged when mined, cut, and fashioned. This damage, usually in the forum of fractures, is very commonly treated by filling.

Although filling is a generally accepted practice for emeralds, there is disagreement in the industry as to what filling substance is the best. Most of the fillings generally used are permanent provided the emerald is cleaned correctly and not exposed to harsh treatment or chemicals.

Emeralds should NOT every be cleaned with ultrasonic equipment. The best way to clean a piece of emerald jewelry is with warm water, mild soap, and a toothbrush. This will ensure that any treatment it has received is permanent.

Rubies, aquamarine, and other gemstones are sometimes treated with fracture-filling, but by far, emerald is the gemstone for which this treatment is most utilized.

Surface diffusion:
Surface diffusion is a type of heat treatment is used when regular heat treatment fails to adequately enhance the gemstones color. Corundum (sapphire) that doesn’t respond well to heat treatment is sometimes treated with surface diffusion.

Surface diffusion changes the color of the stone, but the color change is only in a very thin layer of outer gemstone. This color can be removed by polishing.

This treatment can also cause asterism in corundum, so the beautiful blue star sapphire you are considering buying may have been treated by surface diffusion. If it has, the star is only a few millimeters deep and may not be permanent.

This is a treatment that should definitely be disclosed by the seller to the buyer. It can be a permanent treatment and a treated gem may not be a bad purchase, but this treatment normally lowers the value of the gemstone and should not be priced in the same range as a stone not treated in this manner. Also, the buyer should be aware of the treatment and how it will affect the care of the piece of jewelry.

Irradiation:
This is a treatment which involves using x-rays, gamma rays, or subatomic particles to change a gemstone’s color. It’s used on a number of different gemstones, such as blue topaz, tourmaline, golden beryl, sapphire, spudomene, pearls, and diamonds.

Irradiation is not always stable. Exposure to heat and light can cause the color to fade. In tourmaline and golden beryl, however, irradiation is undetectable and stable.

Irradiation should always be disclosed. If you own a piece of irradiated jewelry and plan to have work done on the piece, advise the jeweler so that care will be used with the jewelers’ torch.

Dyeing:
Dyeing to enhance gemstone color is one of the oldest treatments. It is used to change the color of gems with porous surfaces, such as coral, turquoise, lapis lazuli, and jadeite, or gems that have surface-reaching fractures, as emeralds or corundum sometimes do.

Dye can be difficult to detect, but is not always permanent. It is vital that a seller disclose to a buyer if a stone has been dyed to enhance color, and the purchase price should reflect this enhancement.

Bleaching and Colorless Impregnation:
Bleaching is a treatment which uses chemicals to lighten or remove color in a gemstone. Pearls are often bleached to remove imperfections.

In colorless impregnation, melted wax, polymer, resin, or plastic is poured into openings on the gem’s surface and allowed to solidify. This treatment can improve the gem’s color, luster, translucence, and durability.

Bleaching and colorless impregnation can also be used together to enhance gemstones, such as jadeite.

As with all treatments, it is important that the seller fully disclose to the buyer the type of enhancement used. With proper care, these treated gemstones will remain beautiful indefinitely.

Surface modification:
This is another gem enhancement which has been used for generations. It involves changing a gem’s color by adding something to its surface, such as paint, a backing, another coating.

Some of these treatments are used to fraudulently sell a gemstone. Painting a gemstone to change its color is not permanent, and an unsuspecting buyer could be fooled into paying more than a gemstone’s value.

Many gemstones are coated, such as corundum, quartz, beryl, jadeite and pearls. A foil backing in a mounted can change or enhance the color of the gemstone. A very thin layer of gold on the surface of quartz or topaz can fool a buyer into thinking the gem has iridescence. All of these treatments can be difficult to detect and should always be disclosed by the seller.

Sugar and Smoke Treatments:
These two treatments are used almost exclusively to darken and/or enhance a porous opal’s play-of-color. Since the treatment only affects a thin layer of the gem’s surface, wear or polishing can remove it. A seller must disclose this treatment when selling a sugar or smoke enhanced opal.