Since ancient times, humans have coveted the classic gemstones because they exhibit a beauty unique to the mineral world. It is this beauty, combined with the perception of rarity as well as durability, that motivates people to seek out—and spend significant amounts of money on—the earth's most precious resources.
In recent years, however, the trade has witnessed the birth of a new breed of "gem" that has forced buyers and sellers to revisit the very meaning of the term. Subject to extensive treatment, these so-called gems bear little resemblance to the much-desired stones that have inspired traders and collectors to cross continents over the centuries.
The American Gem Trade Association  defines gem treatment as "any traditional process other than cutting and polishing that improves the appearance (color/clarity/phenomena), durability, or availability of a gemstone." But the practice is hardly new. The truth is that for nearly as long as people have been seduced by gems, they have also tinkered with ways to improve their appearance.
Several references to gem treatment appear in early scholarly works. Arguably the best known is that of the Roman naturalist Pliny the Elder (23–79 A.D.), who deemed treating gems tantamount to fraud. There is evidence that Pliny was referring to methods used to make lesser materials look like different, more valuable stones. Two thousand years later, the questions that plagued Pliny still vex the trade: Is there a distinction between treating a stone to improve its appearance and transforming a near-worthless stone into a product that carries some degree of value? I believe there is.
Let's first address the former: Heat treatment is one of the oldest gem enhancement methods. It can lighten the color of dark material, improve color in pale stones, and/or improve transparency. The method is widely used to modify ruby and sapphire, but many gem species can be enhanced with heat.
Except for treatments such as heating, the gem trade would not have achieved the growth it experienced during the 20th century. The use of treatments allowed finer-quality gemstones to become more affordable and, therefore, more available to a wider population.
However, Josh Hall of Pala International Inc. , a gem dealer based in Fallbrook, Calif., says there's another issue to keep in mind when evaluating the benefit of treatments. "The rarity of fine unenhanced ruby and sapphire is particularly prized by buyers because it has achieved this quality naturally—a consideration reflected in the higher price of these gems."
This is an important point. Truly fine, gem-quality, natural rubies and sapphires sell at prices that support their rarity in the market.
Thus, the market has relied on the abundance of treated gems to satisfy demand among all but the most elite buyers. All of this is well and good—except in those increasing instances when heavily treated stones are sold as natural. Even when buyers are told that "most gems are treated," in my experience, most consumers do not conceptualize just how drastically a stone's appearance can be improved by treatment. As the supply of treated gems increases, the concept of rarity—one of the original pillars of the definition of a gem—is compromised.
Take the corundum market, for example. Gem-quality corundum is rare. However, vast quantities of the mineral corundum are present in the earth. Treaters possess the ability to convert this material into attractive ruby and sapphire. During the past 20 years, heat treatment facilitated the healing of fractures in a significant population of ruby rough that otherwise would have been mostly unsalable. This material accounted for the majority of faceted ruby sold during the 1990s. Likewise, a decade ago, the diffusion of beryllium into sapphires created an array of colors that are quite rare in nature. As is often the case, these stones entered the market without proper disclosure, promptly wreaking havoc on the market.
But in the latest treatment cases, we're seeing a new, far more insidious trend: Gem treatments no longer improve quality. They create it. The problem is not the treated stones themselves, but that they are offered as natural. Unless they are clearly understood by consumers, disclosing them as treated natural gemstones invites confusion. For one thing, buyers must understand how to care for them.
Disclosure is the key to protecting confidence. As technology unlocks even more methods of modifying the vast quantities of mineral rough present in the earth, we increase the risk that large quantities of attractive gems will enter the market owing virtually every aspect of their appearance to treatment. This raises the potential for quality expectations to evolve to a level where natural gems will not be able to compete. Unless there is a meaningful strategy to distinguish these stones from fine natural gems, the industry risks creating a market that consumers can't navigate. The implications of that for the global trade are quite ominous.