Surface-Treated Diamonds Increase Risk For
Those Who Can’t Spot Them
By Antoinette Matlins
By Antoinette Matlins, gemologist-consultant and author of many award-winning books, including Diamonds: The Antoinette Matlins Buying Guide: How to Select, Buy, Care for & Enjoy Diamonds with Confidence and Knowledge (GemStone Press)
Colorless and fancy color diamonds are the focus of investors today, but few are aware that many artificially colored diamonds are being sold without disclosure, sometimes accompanied by counterfeit GIA reports.
A variety of techniques are now used to transform off-color diamonds into diamonds that appear to have rarer and costlier colors: colorless and rare fancy colors. Some use very sophisticated instrumentation; these are difficult and expensive to produce and the resulting colors are permanent. There are also an increasing number of surface-coated diamondsmade by a much easier and cheaper method that involves applying a special coating to the surface of the diamond; the resulting colors include colorless grades (D-F) as well as “fancy” colors, but the color produced is not permanent, and should sell for a fraction of the cost of other diamonds. This is an area of serious concern because they are being sold as “natural color” diamonds.
To complicate matters further, many diamond dealers and jewelers don’t have the knowledge and skill themselves to know whether or not a diamond has been coated to alter the color. Misleading terms have caused confusion as well. Treated-color diamonds reportedly treated by an infusion technique—the very term suggesting that the resulting color penetrates into the stone—have come into the marketplace. But these “infusion-treated” diamonds are off-color stones to which a surface coating had been applied—on the bottom of the stone only.
The number of such stones in the market is increasing. They are popping up in virtually every color—including shades of yellow, pink, and blue—and in every size, shape, and clarity.
But Have No Fear….A Simple Carbide Scriber* Can Solve the Mystery!
Fortunately, this particular treatment is one that is easy to spot, with a tool called a carbide scriber. By taking a carbide scriber – a simple tool that looks like a pen – and dragging its carbide point across one of the facets, the point will scratch through the coating. It will not scratch the diamond, just the coating. Then the “tell-tale” scratch can be seen immediately when one looks at the facet with magnification (a 10-power loupe – the little eye magnifier used by professionals -- will reveal it quickly).
How To Use The Carbide Scriber
A carbide scriber can be used by anyone. No gemological training is required, and it’s quick and easy. Here’s how to do it:
CAUTION: Do not use a carbide scriber on any gemstone except diamond. The carbide point is extremely hard and will scratch all other gemstones.
* Professional quality carbide scribers are available from the Accredited Gemologists Association at www.accreditedgemologists.org or call AGA headquarters at 619 501-5444. The cost is $20 for a high quality scriber with interchangeable points. Includes 2 carbide points—one “fine” and one “standard”—which are easily stored within the scriber. Replacement points are also available.