Gemstone Treatments

Many of the gemstones available on the market today are treated in some way. The treating of
gemstones has been conducted for centuries and most of the treatments are accepted throughout the gem industry as long as the treatments are disclosed. Gemstones such as blue topaz and tanzanite are almost always treated and therefore the treatment of these gemstones is assumed and expected.

Most of the treatments are permanent and stable meaning the enhancement of the Amethyst gemstone will
last and the color will not fade over time. These treatments, also referred to as enhancements, are applied to natural gemstones. A treated natural gemstone is not the same as a synthetic or simulated gemstone. Synthetic gemstones are man made of the same chemical composition as natural gemstones and are usually priced considerably less than natural gemstones. Simulants are gemstones that may appear similar to a natural gemstone but do not have the same chemical
composition. A cubic zirconium is a diamond simulant. It looks like a diamond but has a completely different chemical structure.

Gemstones are usually treated to make them more visually appealing and therefore more
valuable. Common treatments include:

Heat is the most commonly used gem treatment. Heat can remove cloudiness, remove color centers, and enhance or even change the color of a gemstone. In many gems heat treatment is undetectable. Some gems such as aquamarine, citrine, topaz, tanzanite, and blue zircon are so frequently heat-treated that the treatment is accepted and expected within the gem industry. In other gems such as sapphires and rubies, heat treatment is detectable. Well-colored sapphires and rubies that have not been heat-treated demand higher prices. All heat treatment is not successful. The length of time and degree of temperature can make the difference in how the gem responds. Anytime a gem is heated there is the risk of damage to the stone or other undesirable changes. The exact formulas of time and temperature are well-guarded secrets.

Irradiation is used to change or enhance the color of a gemstone. When gems are subjected to gamma rays (cobalt 60) the electrons in the gem may relocate to a different location within the gem. This changes the way light is absorbed by the gem and therefore changes its color. Topaz is commonly irradiated to turn the colorless material blue. Irradiation is sometimes followed by heat treatment.

Diffusion is a process in which gems are heated while in the presence of another chemical compound. Sapphires, for example, are placed in a heater with a beryllium compound. When the temperature reaches a certain point the beryllium diffuses into a thin layer of the sapphire. The colored surface of the gem is only a millimeter or less so diffused gems can be damaged by wear. This process can cause dramatic changes to a gem’s appearance. In 2001 many padparadsha sapphires were sold as natural only to be proven later as having been beryllium
diffused. The process changes a relatively unattractive brownish color corundum (sapphire) and transforms it into a pinkish peach color known as padparadsha, one of the most valued colors of sapphires.

The process was eventually identified by a gemological laboratory and had a very negative effect on the sapphire market. Today, the process is understood and there are companies
specializing in the sale of diffused gems. The treatment of the gems is openly disclosed and therefore accepted within the gem trade.

Coating is another process that changes the gem’s appearance by placing a thin
coating of a substance to the entire gem or the pavilion of the gem. Much of the
fancy colored topaz such as Mystic Topaz have undergone this treatment.

Fracture filling is the process of filling the cracks of a gemstone with a
substance that makes the cracks less visible. Emeralds, for example, are commonly
oiled to reduce the visible inclusions in the gem. Diamonds are sometimes filled
with resins or other substances to hide inclusions

Gem treatments have become an important part of the gemstone industry and
provide customers with additional buying options. These treatments are accepted
throughout the industry providing full disclosure is made to the consumer.


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