The number of treated diamonds is growing. Here’s a look at the four basic treatments – as well as synthetics – with tips on how to detect them
No doubt about it, treated diamonds have become a big part of today’s market. They’re also becoming more sophisticated and difficult to detect.
Treated diamonds – and disclosure of the treatment – have become such as concern that De Beers formed a committee about a year ago to keep tabs on how many fracture-filled, irradiated and otherwise altered diamonds reach the market each year; what percentage are disclosed; and what impact they might have on consumers. The committee also keeps gemological laboratories around the world abreast of new developments.
De Beers admits it’s extremely difficult to get accurate information on how many treated diamonds are produced and disclosed. But the second part of its mission – keeping in touch with gem labs – is less complicated. Committee members meet regularly with gem lab representatives to exchange information. The committee also has helped to fund such related projects as an acclaimed video by the Gemological Institute of America on the nature and detection of fracture filling.
The gem labs themselves also have delved deeply into tracking and researching treatments. GIA’s Gem Trade Lab, for example, has conducted extensive research into all types of gem treatments and warns they are growing ever more sophisticated and difficult to detect.
However, the good news behind all these efforts is that all known treatments can be detected, and jewelers can use their own gemological equipment to detect them. The jeweler is likely to encounter four basic types of diamond treatments, plus synthetics. Here’s how they are produced and how to detect them.
Fracture filling: Fracture filling is a semipermanent process in which a substance with a refractive index close to diamond’s is infused into cracks or fissures to improve a stone’s clarity. That’s why the process sometimes is called clarity enhancement.
The process renders cracks or fissures in a diamond nearly invisible – but not undetectable. The easiest way to see them, says GIA, is to gently rock the diamond back and forth under a light while observing it through a 10X loupe or microscope. The fracture filling will display a distinctive purple, blue or orangy flash. Look carefully, however, because the flash can be tiny and gone in an instant. To be certain, look at the diamond from several angles.
In addition, a microscope can reveal trapped bubbles or tiny areas of incomplete filling that are highly reflective with darkfield illumination. And occasionally, some filling processes leave surface residue around the break or show small cloudy or colored areas inside.
Fracture fillings are durable, but not fully permanent. Acid boiling (or pickling) removes the filling. Heat from a jewelers’ torch can cause the filling to bubble out of the cracks onto the surface of the stone or to turn cloudy. In addition, prolonged exposure to ultraviolet radiation can discolor fillings of some diamonds (produced by Koss & Schechter and Goldman Oved, according to Gems & Gemology, GIA’s quarterly publication). However, it takes thousands of hours of exposure for these fillings to show any negative effects.
Because the filling is not permanent, GIA and most other major gem labs won’t grade diamonds with this treatment. Further, companies that fracture-fill diamonds treat stones as small as five points. Stones this small almost never get to a major gem lab, so the jeweler is responsible to check for fracture fillings.
Fracture-filled diamonds began to show up in world markets about seven years after Israeli diamond manufacturer Zvi Yehuda announced he had invented a process that could fill gletzes (cracks) almost invisibly. Today, Yehuda remains the leading producer of fracture-filled diamonds. Several other companies based in Israel also produce them, including Koss & Schechter, Oved Goldman, Clarity Enhanced Diamond House and Rovor Diamonds.
Major diamond bourses have adopted severe penalties for dealers who sell fracture-filled diamonds without disclosing the treatment. And some jewelry retailers now require suppliers to pledge in writing not to sell them any fracture-filled diamonds.
Lasering: Diamond manufacturers sometimes use a white hot laser to burn unsightly black inclusions out of a diamond. They and gemologists don’t always agree about lasering, however. The manufacturers have no qualms about disclosing the existence of lasering, but they see it as part of the cutting process. Others see it as a separate treatment and say it should be disclosed as such.
Lasering in loose diamonds usually is easy to detect with a 10X loupe. The laser beam leaves a tiny tunnel appearing as a line from the surface of the stone to the area where the inclusion was burned out. Larger inclusions often require lasering from several angles, so some diamonds have three or four laser tunnels. A note of caution: some stones with multiple drill holes are then fracture-filled.
Laser tunnels in mounted diamonds are visible unless the tunnel is very, very short or the treated area is covered by a prong.
GIA and other labs routinely grade lasered diamonds because the process is permanent and irreversible.
Irradiation: Irradiation dates back to the early part of this century, when researchers discovered that bombarding diamonds with radium turned them green. None of those early efforts circulates today because the radium treatment rendered the diamonds so radioactive they’ve had to be housed in safes to this day (and for about 500 more years).
More modern irradiation treatments can turn diamonds many colors and leave no residual radiation. The treatments are designed to transform near colorless or less attractive colored diamonds into vivid green, pink, purple, canary yellow, orange and near black (extremely dark green).
Irradiated diamonds carry the same disclosure rules as those that are fracture filled, but detection is more difficult. Examination with a spectroscope will show lines in certain absorption bands of irradiated diamonds that aren’t found in untreated stones. However, these bands can change, depending on the color of the diamond and the treatment process. (Note that all green diamonds get their color through irradiation – either through treatment in a lab or naturally in the ground. GIA has some promising leads for detecting irradiated diamonds. But there still is no concrete way to know whether that irradiation happened in the ground or in a lab.)
Diamond dealers have a less formal means of spotting potentially treated colored diamonds. Those with colors that look too good, too vivid or too uniform are thrown into a pile for a closer look.
Irradiation is permanent.
Coating and other deceptive additives: All of the treatments mentioned so far are permanent or durable. Disclosed, they enlarge the market for otherwise unsalable diamonds. The crime lies in non-disclosure, not in the treatment itself. Coatings are another story because they are easily removed and are used only to deceive.
Unscrupulous dealers discovered decades ago that a little blue dye on the culet makes a yellowish diamond appear white. And remember the clever switch artist who fooled a major auction house for awhile by leaving a poor quality white diamond with pink fingernail polish on the culet in place of a fabulous pink diamond on display.
While all of the current coatings will come off with a good cleaning, GIA researchers believe the next generation will be more high-tech. The researchers fear crooks will use carbon vapor deposit techniques to leave a thin diamond film on poor quality white diamonds, making them look like fine blue or yellow diamonds.
GIA has so treated several diamonds and says detection really isn’t difficult. The film doesn’t adhere well to facet junctures, leaving bare spots that can be spotted by dropping the stone in heavy liquid.
Synthetics: Synthetic diamonds are not a treatment and are not yet on the market in quantity. But they will be in due course, and they’ll be subjected to the same disclosure rules and detection methods as the above treatments.
The vast majority of commercially produced synthetics that can be processed into gems are orangy yellow because of the nitrogen added during the growth process. However, General Electric has produced clear crystals for the electronics industry.
The biggest potential source is Russia, where Chatham Created Gems of San Francisco, Cal., is trying to develop a line of commercial synthetic diamonds. Various scientific agencies in Russia have studied crystallography for defense purposes for decades. In recent years, they’ve turned their attention to the marketplace and have produced yellow, white and blue gem-quality diamonds, though not yet in commercial quantities.
Wherever synthetic diamonds are made, they have common identifying characteristics, say GIA researchers. These include distinctive growth lines, color zoning and distinctive metallic inclusions left from the flux material from which they are grown. All of these are visible with a gem microscope. Many synthetics turn yellow green under shortwave UV lamps, almost never seen in natural stones, and they have unique absorption bands that can be seen with a spectroscope.
De Beers and GIA are working on an easy detection device, but GIA stresses that knowledge is the best defense. In fact, all researchers say jewelers must stay on top of new developments in diamond treatments and maintain the proper equipment to identify them. (Sharon Wakefield offers further details in her article “Synthetic diamond jewelry: Are you prepared? also in this issue.)