What You Should Know About Enhancements and Gem Pricing

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.

Take ruby, for example. We know that most rubies are heated. The question is how much the heat treatment affects the value of the gem. Emerald enhancements also raise concerns. In the past, we simply assumed that all emeralds were oiled. Today there’s Opticon and other resins as well as many different oils of varying durability. These treatments make a difference in the emerald’s value, but just how much?

Many jewelers rely on information from their gemstone suppliers and trust that the price they pay is fair. But how can you convey to consumers accurate information about gemstone enhancements? Do they know if the price they pay is reasonable for the treatment they’re getting? Appraising treated gems poses a similar challenge. Yet, when it comes to the effect of enhancements on pricing, information is scarce.

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.

The industry has debated whether this treatment should be disclosed. The Gemological Institute of America will note the glass-like residue on its laboratory report, and many dealers support the disclosure policy. Yet retail jewelers generally do not discuss with their customers the possible existence of this residue. Further complicating matters, the residue from the insulation may fuse to the gem material itself. If this residue is present, you should disclose it to the customer as an unintentional byproduct of the heating process. GIA will note this residue on its laboratory report.

Another possible treatment, one that’s rarely used, is intentional filling of cavities. Natural cavities in rubies can be filled with a silica-based gel that transforms into glass when heated. The process effectively fills large cavities and adds weight to the ruby.

Unfortunately, there’s no consensus on how much these treatments affect the price of rubies and sapphires. This question remains the focus of much debate in the industry. Through research, I’ve developed some guidelines to aid in the valuation process. The accompanying table shows the approximate premiums and discounts associated with corundum. Bear in mind that the origin of the stone also will affect pricing in the unheated category, but that’s a separate issue. For example, an unheated Burma ruby or Kashmir sapphire will command higher premiums than those shown in the table.

How Ruby & Sapphire Treatments Affect Price

Commercial Good Fine Extra-fine
Untreated Sapphire 0% to +5% 0% to +5% +5% to +10% +10% to +15%
Untreated Ruby 0% to +5% +5% to +10% +10% to +15% +15% to +20%
Heating (Base) 0% 0% 0% 0%
Surface Infilling of Ruby 0% 0% to -5% -5% to -10% -10% to -15%
Fracture Filling -10% to -50% -10% to -50% -10% to -50% -10% to -50%
Notes: 1. Surface infilling is the glass residue associated with heat as a byproduct of the process. Melted borax fills in surface fissures. 2. Fracture filling refers to cavities intentionally filled with glass. 3. Some exceptional untreated rubies and sapphires may command higher premiums.


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. But few seemed to care.

How Emerald Treatments Affect Price

Commercial Good Fine Extra-fine
Untreated +5% to +10% +5% to +10% +10% to +15% +15% to +20%
Treatment Level Slight (Base) 0% 0% 0% 0%
Treatment Level Moderate 0% to -5% -5% to -10% -10% to -15% -15% to -25%
Treatment Level Extensive -10% to -15% -15% to -20% -20% to -25% -25% to -35%
Notes: 1. Some dealers may have a preference for type of treatment, thus affecting their particular price structure. 2. Some exceptional untreated emeralds may command higher premiums. 3. An extra-fine emerald by definition may not have many fissures that will accept the treatment. However, it is possible for the gem to exhibit a top color and have many fissures that the enhancement process has potentially masked, thus requiring greater discounts.

Then came Opticon, an epoxy resin with a hardener made by Hughes Associates in Wyzatta, Minn. Although dozens of similar epoxy-type resins are in use today, Opticon is the best known. (The name is erroneously becoming a generic term to describe all resin fillers.) The use of Opticon in emeralds dates back about 10 years or so. Only in recent years has it gained notoriety owing to negative publicity. It’s used primarily with Brazilian emeralds, although emeralds from any origin can be treated long after they’re imported.

At first the industry gave a thumbs-down rating to Opticon because of the bad publicity and a lack of knowledge about the product. I suspect that, ironically, many of the same dealers who are now critical of Opticon have bought and sold Opticon-treated emeralds unknowingly for years. In fact, Opticon and other resins and hardeners can add durability to emeralds. Over time, however, the resins may discolor or deteriorate. The Arthur Groom Co. has developed a resin called Gematrat that purportedly is more durable than other resins and will not discolor.

The industry has yet to approve a single emerald treatment. When it comes to oil, most people favor cedarwood. As for epoxies, some see Opticon as the death of the emerald industry, while others welcome the use of resins, especially if they add durability. With so many enhancements available, how can anyone determine with certainty what was used in a particular emerald? Raman spectroscopy can distinguish between treatments, but it’s expensive and impractical for the thousands of emeralds sold yearly.

In fact, the amount of treatment may be easier to gauge than the type of enhancement. By observing the emerald under magnification, with practice you can learn to estimate the level of treatment in the gem. Last year at the First World Emerald Congress, California emerald dealer Ron Ringsrud proposed a system for gauging enhancements. He suggested four treatment levels: negligible, slight, medium, and heavy. In my publications, I’ve whittled it down to three classifications: slight, moderate, and extensive.

Before disclosing an emerald enhancement, make sure you can positively identify it. Your supplier may provide a guarantee as to the type of treatment. Remember that the “flash’ effect associated with some resins is merely an indication of the type of treatment, not a guarantee. GIA warns that some oils may also give a flash because of the difference in refractive index from the host emerald. The Groom company has added a tracer to its filler that fluoresces violet-blue under long-wave ultraviolet light. This will help identify the filler and determine how much of the material is present.

The table on the preceding page shows the potential effect of emerald enhancements on price. Here, too, there are exceptions that may not fit into this pricing structure.

The rest of the list. While the industry may consider enhancements of gems beyond ruby, sapphire, and emerald as unimportant, in fact, they are very important. Here are some of the more noteworthy cases.

  • B-jade. One critical pricing issue concerns “B-jade,’ jadeite that has been acid-bleached and polymer-impregnated. The only reliable test for this treatment is infrared spectroscopy. Labs equipped to do this include GIA, the American Gem Trade Association, and the Mason-Kay Co. of Denver. According to Don Kay of Mason-Kay, more than half the jade sold in Hong Kong is B-jade. Its major market is Asia.

  • There is less B-jade in the United States, but it’s still a problem because it’s difficult to recognize and the price difference is vast. B-jade sells for about 10% to 15% of the price of untreated jadeite. Kay says he was recently offered a green cabochon that would have been worth $6,000 to $7,000 if untreated. The seller quoted him $700 for the piece.

  • 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.

Stay informed. Gemstone enhancements have become increasingly sophisticated. We rely on research from GIA to keep us informed of new advances in gem treatments. Even so, we need to be realistic in our goal of accurate detection of enhancements. Yes, they do affect the price of gems. And no, we probably can’t detect each enhancement with total accuracy.

However, it’s every jeweler’s responsibility to stay as informed as possible regarding enhancements. This information will be crucial to your business when you buy and sell gemstones.

Richard B. Drucker is the president of Gemworld International and publisher of The Guide, a pricing periodical he began in 1982. An international gemstone consultant, he has published numerous books on the jewelry industry.