Heat treatment has created more salable gems than Mother Nature ever created on her own. But heat treatment can also reduce the value of gemstones. When color origin cannot be determined, prices for many colored gemstones usually sink to the lowest common denominator, as they have for aquamarine, one of a dozen popular gems whose color can only rarely be identified as natural vs. heat-derived.
Unfortunately, the list of gems with unidentifiable color origins is growing, and two of the big three—rubies and sapphires—are in danger of joining the list. (Emeralds, which have not yet been enhanced through heat, have their own unique problems with filler identification.) Add to that list the difficult, if not impossible, identification of diamonds treated with high pressure and high temperature (HPHT), and it becomes obvious why so many gemologists in the industry are concerned. Curiously, though, retail jewelers don’t have a problem with it.
Over the next three months, we’ll look at what the industry has been facing, how they are dealing with it, and the challenges that lie ahead.
Part I: Cooking Up a Tradition
The first recorded evidence of gemstone enhancement is attributed to Pliny the Elder (that’s C. Plinius Secundus, 23-79 A.D.). According to Sydney Ball’s A Roman Book on Precious Stones; Including an English Modernization of the 37th Book of the Historie of the World by C. Plinius Secundus (GIA, 1950), Pliny says gemstones were heated to improve color. But these references concerned oiling and dyeing gem materials rather than changing color, which we now understand as the change of valance states of trace elements or the alteration of color centers.
According to Kurt Nassau (Gemstone Enhancement, Butterworths, 1994), experiments for this type of enhancement by heat didn’t appear in writings until the 14th century, when experimenters may have used the medieval equivalent of the modern glass or assay furnace. Those experimenters exposed gems to heat in an attempt to create diamond imitations—i.e., colorless gems.
Nassau’s historical review shows that it wasn’t until the 19th century that true commercial color enhancement from heat was accomplished in the labs and written in the texts, beginning with the pinking of topaz. Nassau notes the great work of Max Bauer, Precious Stones, written in 1896, in which Bauer describes in detail all of the gems whose colors are enhanced through heat treatment, which he called “burning.” That puts color-enhancing heat treatment at just over 100 years old. With a century of color-enhancing heat treatment, one can feel comfortable calling it a tradition.
But in the early 20th century, it was still a relatively new process. Herbert Smith, gemologist and author of Gemstones (1912), wrote an entire chapter devoted to the “Treatment of Stones” and didn’t mention one word about color or clarity enhancements. The chapter was devoted to the topics of cutting, polishing, and mounting gems.
But Smith did write about heat treatment, saying that the heating of gemstones was “familiar” with pink topaz, and he mentioned heated yellow stones from Brazil: “Zircons will lose all of their color through heat, becoming excellent diamond imitations.” Under different heating conditions, says Smith, zircon could yield “lovely blue stones.” Less familiar changes include amethyst to citrine, pale green beryl to aquamarine, and some corundum going from violet to pink and yellow to colorless. “Generally it may be said that the effect of heating is to weaken the color,” Smith wrote, and if sufficiently prolonged, drive color off completely—again, trying for the ultimate diamond imitation.
Enter the gemologist. By the mid 1930s, heat treatment for improving color, not just eliminating color, was considered an established practice. Henry Briggs, in GIA’s Spring 1936 issue of Gems & Gemology, lists more than half a dozen gems and their color improvements. He writes in his continuing gemological encyclopedia: “Gems and gem materials are often treated to alter their color and thus render them more readily salable. … Heat treatment is applied to many gems, and with a certain amount of success.”
The 1950s saw an increase in gemological understanding along with a new world of gemological tools to make gemstone identification easier. Color-enhancing heat treatment of some gems was, from the beginning, impossible to identify, so even at that time gems such as pink topaz and citrine were presumed to be enhanced through heat.
And while gemological equipment has advanced tremendously and now is available to the retail jeweler, indications of heat treatment haven’t become any easier for the gemologist. Unless one can find inclusions that are either in pristine condition as Mother Nature interred them or have obviously been damaged by heat, there is little on which gemologists can base their conclusions.
Retailers respond, “Who cares?” The information being disseminated into the trade is that most aquamarines, most citrines, and almost 100% of all tanzanites have been heated. Yet, according to a recent JCK poll, there are still a small number of retail jewelers who do not understand how prolific heat treatment has become. The list of gems that are commonly heat-treated to improve color is considerable and includes traditional birthstones like amethyst, citrine, aquamarine, ruby, sapphire, tourmaline, and blue zircon.
Other retailers do know what’s been heated but don’t disclose this information to customers. Perhaps they think that heat treatment is a deception, or that their customers will think it’s a deception. Pliny wasn’t too keen on enhanced gems, either, calling them “sham curiosities and mostly not genuine.”
Still, responsibility for disclosure rests on the shoulders of retail jewelers. According to FTC guidelines, rules and regulations for the gem and jewelry industry, jewelers must disclose to customers any enhancement that dramatically affects a gemstone’s value and must indicate whether the treatment is permanent and/or requires special care. And even if retail jewelers can’t tell, they can’t claim ignorance. Besides, today’s wholesalers, for the most part, are doing their best to inform their retail clients about enhancements.
However, a typical jeweler’s inventory contains numerous heated gems that have permanent color requiring no special care. If the enhancement does not appreciably affect value, retail jewelers are not required to share disclosure information with their customers. And even when customers are told at the counter that a gemstone has been enhanced by heat, many retailers say their customers show little interest.
“Some clients are hesitant at first,” say a few of JCK‘s Retail Panelists, “but when you give them the history, show them the beauty of the gemstone, and explain that the color is permanent, then it’s okay.” Many state that customers are comfortable knowing that the enhancement is an accepted trade practice. So for both the retailer and consumer, disclosure is only a matter of offering general information, which makes good business sense and fully satisfies FTC requirements for disclosure.
Apathetic retailers, take note: Saying nothing can get you into big trouble with your customer. According to an American Gem Trade Association poll, customers don’t mind enhancements if they’ve been told about them during the sales presentation. It’s when they are not told—and find out later—that it becomes an issue.
Even with all of this information about disclosure available, only slightly more than half of the retail jewelers polled disclose 100% of the time. Some say they can’t monitor what their sales staff is doing, and a small percentage say they disclose only when the ticket price of the item is high. Why? The consensus: “Most customers don’t care, as long as we stand behind the product.”
No wonder disclosure for traditionally heated gems is a hard sell. As Lucy of “Peanuts” comic strip fame once complained, “There’s just too much apathy, Charlie Brown! … Eh, but who cares?”
Next month: From traditional heat treatment of Geuda sapphire to glass-filled fractures in ruby, is the reaction in the trade the same for heat-treated sapphire and ruby as it has been for citrine and tanzanite?