If you get confused over gemstone enhancements, you’re not alone. The industry today applies so many different treatments to gemstones – heat, oil, Opticon, irradiation – that it’s no easy task evaluating enhancements and gauging their effect on price.

Ruby and Sapphire
At least 95% of rubies and sapphires are heat-treated. Early heating methods involved the use of 55-gallon oil drums lined with fire bricks or clay and heated to extreme temperatures. Treaters now use sophisticated furnaces that provide a controlled heating environment. Customers should always be informed that their ruby or sapphire has been heated.

The problem with heat today is the extreme temperatures (up to 2,000ºC) that are used with some rubies, particularly those from Mong Hsu in Burma. These gems are packed in borax, silica, or aluminum for protection. During the heating process the crystalline powder melts, resulting in a “glass-like” substance that fills the surface fissures. The glass adds no weight and isn’t visible to the unaided eye.

Emerald
Because of the nature of emeralds, inclusions often extend to the surface, which makes them a prime target for some type of treatment. Pricing the various emerald enhancements gets tricky. For at least 2,000 years, emeralds have been enhanced with oil of one form or another. Pricing was never a big issue in the past because we always assumed that the emerald was oiled. Various oils were used, some more durable than others.

Irradiated gems. These can be difficult to price and are often sold undetected. For example, yellow, orange, and even padparadscha sapphire all can be irradiated. Standard gemological testing can’t determine if the gem has been irradiated. But an intense orange or yellow sapphire is extremely rare in nature, so you could assume that irradiation and/or heat played a part in obtaining the color. Also, heated or irradiated sapphires may fade over time with exposure to light. This, too, will affect the value of the gem.

Irradiated blue topaz and smoky quartz are almost always obtained through irradiation. Irradiation, however, is not a factor in their prices, which run just a few dollars per carat.

Aquamarine. These stones are routinely heated to improve their color. They’re typically greenish-blue before heating. The heat drives out the green, leaving a more desirable blue. Interestingly, the purer blue derived from enhancement commands a higher price than in the natural state. However, some dealers today are promoting the unheated greenish-blue material for its unique color, which distinguishes it from its blue topaz look-alike. With the growing interest in natural gems, perhaps one day the natural will cost as much as, if not more than, the heated gems.


Richard B. Drucker, G.G.
Contributing Editor