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Clarity Enhancement of Diamonds

• Laser Drilling

• Fracture Filling

• What Should You Do?

The clarity, or purity, of a diamond — the relative or apparent severity of flaws within the stone — has, like the other "four Cs", a strong bearing on the evaluation of a diamond's worth. The most common flaws, or inclusions, seen in diamonds are fractures (commonly called feathers, due to their feathery whitish appearance), and solid foreign crystals within the diamond; such as garnet, diopside, carbon or even other diamonds. The size, color, and position of inclusions can reduce the value of a diamond, especially when other gemological characteristics are good. Those who prepare diamonds for sale sometimes choose to reduce the visual impact of inclusions through one or more of a variety of treatments. This discussion will focus on the two major forms of "enhancements:" Laser Drilling and Fracture Filling. There is a big difference between these two methods of improving the look of a diamond as will be described.

Laser Drilling
The development of laser drilling techniques on a microscopic scale, has enabled diamond manufacturers and cutters to selectively target and either remove or significantly reduce the visibility of crystal or iron oxide-stained fracture inclusions. Diamonds have been laser-drilled since at least the mid-1980s. Most often it is used to whiten a black carbon crystal which is prominently visible in the diamond to the naked eye. Since the development of the laser drilling technique, and until more recently, laser drilling was an accepted part of the diamond manufacturing process. It is still used today on diamonds which have a significant presence of black carbon crystals imbedded in the diamond.

The drilling process involves the use of an infrared laser to bore very fine holes, or tubes, into a diamond to create a route of access to an inclusion. Once the included crystal has been reached by the drill, the diamond is immersed in sulfuric acid and the acid travels down the tube to dissolve the carbon crystal or iron oxide staining.

Several inclusions can be thus removed from the same diamond, and under microscopic inspection the fine bore holes are readily detectable, usually when the diamond is viewed from the side or bottom of the diamond.

Unlike fracture-filling described below, a laser drill hole is considered by the Gemological Institute of America's Diamond Trade Laboratory to be an internal inclusion which is marked on their certificates just like other inclusions such as feathers, clouds and crystals.  This is because the process of laser-drilling is a permanent process. In contrast to fracture-filled diamonds, the GIA does issue their certificates (called "Diamond Grading Reports") for diamonds which have laser drill holes in them. The following is a direct quotation from GIA's website concerning the range of diamonds for which the GIA Laboratory will and will not issue certificates.

A diamond which is certified but which has a laser drill hole as one of its inclusions is not as valuable as another diamond of the same grade which does not have a laser drill hole.  At A. Fishman & Son, we do not sell diamonds with laser drill holes.

Fracture Filling
The fracture-filling of diamond is a very controversial treatment within the industry — and increasingly among the public as well — due to its radical and impermanent nature. The process involves filling open fractures in a diamond (e.g., large and multiple feathers) with a glass-like substance which will camouflage the visibility of these large feathers. This results in the diamond having an "apparent" clarity grade which is better than it would actually merit without the treatment. In fact, most diamonds which are suitable for the fracture filling process are so imperfect that they run the danger of breaking under stress due to the significant fractures present in the diamond.

Because the filling glass melts at such a low temperature, it easily "sweats" out of a diamond under the heat of a jeweler's torch; thus routine jewelry repair can lead to a complete degradation of clarity or in some cases shattering, especially if the jeweler is not aware of the treatment. Similarly, a fracture-filled diamond placed in an ultrasonic cleaner may not survive intact.

The glass present in fracture-filled diamonds can usually be detected by a trained gemologist under the microscope: the most obvious signs are air bubbles and flow lines within the glass, which are features never seen in untreated diamond. More dramatic is the so-called "flash effect", which refers to the bright flashes of color seen when a fracture-filled diamond is rotated; the color of these flashes ranges from an electric blue or purple to an orange or yellow, depending on lighting conditions. One last but important feature of fracture-filled diamonds is the color of the glass itself: it is often a yellowish to brownish, and along with being highly visible in transmitted light, it can significantly impact the overall color of the diamond. Indeed, it is not unusual for a diamond to fall an entire color grade after fracture-filling. For this reason fracture-filling is normally only applied to stones whose size is large enough to justify the treatment: however, stones as small as 0.02 carats have been fracture-filled. This is an important factor in the very low price of some diamond jewelry products too, for example, tennis bracelets.

It is notable that most major gemological laboratories, including that of the influential GIA Diamond Trading Lab, refuse to issue certificates for fracture-filled diamonds. However, there are other Labs that do certify these diamonds so it is important to know what Lab is issuing the certificate on a particular diamond.

Fracture-filled diamonds with a specific "apparent" clarity grade sell at a very significant discount compared to what I like to describe as a "real" diamond of the same clarity grade will sell at. For a buyer who is uninformed, it may appear to be a bargain.  It is not!

At A. Fishman & Son, we do not sell or otherwise deal in fracture-filled diamonds. We do not consider it worthy of any investment of our money and we recommend that our customers do the same.

What Should You Do?
The World Federation of Diamond Bourses and government agencies such as the United States Federal Trade Commission explicitly require the disclosure of most diamond treatments at the time of sale. Some treatments, particularly those applied to clarity, remain highly controversial within the industry — this arises from the traditional notion that diamond holds a unique or "sacred" place among the gemstones, and should not be treated too radically. While, as noted above, there is a distinct difference between laser-drilled diamonds and fracture-filled diamonds, our recommendation is to stay away from diamonds with either type of treatment.  I say this with regard to laser-drilled diamonds not because I place them in the same category as fracture-filled diamonds. I don't.  But because in today's market a laser-drilled diamond is a very difficult diamond to sell or trade-up for a better diamond and you are better off buying a better quality, smaller diamond, than a larger one which has been laser-drilled.  In no uncertain terms should you ever purchase a fracture-filled diamond!