Diamond treatments refer to clarity or color enhancement techniques. Even if you are not in the market for a treated diamond, an understanding of these methods may help you advise those who are comfortable in passing on the knowledge they’ve learned here.
Clarity Enhanced Diamonds
Clarity enhancement techniques include laser drilling or fracture filling. The justification for clarity enhancement is that if you can remove the inclusion of an otherwise beautiful diamond so that it will be loved by its eventual wearer, then why should you not do it?
The problem with clarity enhancement is a matter of disclosure. ABC recently did a story on the issue that you can watch here.
There are many variations of laser drilling but the general concept is to create a hole, the diameter of a human hair, into the diamond where the inclusion is. Depending on the inclusion, it can then either be bleached or dissolved thus turning a black inclusion white. Sometimes, inclusions only appear dark because of the way they handle light and simply drilling into the void introduces air that changes the way the inclusion handles light and thus making the inclusion less obvious.
The newer methods of laser drilling are increasingly difficult to detect. For example, the holes can be filled and sealed with a material that makes them less obvious, sometimes the holes appear irregular and natural, but other methods don’t require drill holes at all. Laser drilling takes a long time and that is why diamonds with inclusions close to the surface are more suited to this method. The newer methods exploit heat and pressure to move inclusions that are deeper in the diamond closer to the surface.
Contrary to popular belief, GIA does issue certificates for diamonds that have been laser drilled. A laser drill hole can be indicated on a lab report in one of two ways. A “laser drill hole” will be indicated on a clarity plot in red and green and will be plotted as the first clarity characteristics regardless of whether it is the grade-setting inclusion. Alternatively, if there are no obvious drill holes, then a comment “Internal laser drilling is present” will be made. The clarity grade stated on the certificate will be the final clarity grade after enhancement.
The FTC requires, again contrary to popular belief, a seller to mention the fact that the diamond is laser drilled. In general, the test for whether disclosure is required is whether a treatment severely affects the price of the diamond. Laser drilling definitely severely affects the price of a diamond!
For those who wish to seek comfort by purchasing a stone before fracture filling was invented, you should know that the first laser-drilled holes were graded in 1970. It is not my intention to influence you on how you perceive laser drilled diamonds, all I will say is that a laser-drilled hole is considered a permanent enhancement and that the diamond should be sold by its pre-enhanced clarity grade. Although some people may consider this a ‘mind-clean’ issue, laser drilled diamonds definitely have their market and are commonly traded.
A fracture filling means introducing a filler material into cracks that extends to the surface. The most common process is known as the “Yehuda Process”, named after the company that carries out the treatment. The refraction index of the filler material is closer to diamond than the air originally in the crack and thus the crack becomes less visible. In many cases SI quality stones can appear like they are VS quality.
Unlike laser-drilled stones, GIA will not issue a lab report for a fracture filled stone. The problem with fracture filled stones is that the filler material usually has a much lower melting point than diamond such that it can literally fall out when repair work is being done to the setting. It is important to make sure the jeweler removes a fracture-filled diamond before working on the setting.
Color Enhanced Diamonds
Color enhancement may refer to making a Cape series (D-Z color) diamond more colorless, or to create various types of fancy color diamonds. I will only be discussing the method of making a D-Z color diamond more colorless. The method I am referring to is known as high pressure high temperature (HPHT). As you learned from the basics tutorial on diamond color, the yellow tint in colorless diamonds is caused by nitrogen impurities. The HPHT process can improve the color by removing these impurities at the atomic level so the HPHT process is permanent. The catch is that the only type of diamond is that can be used in this treatment is the type-2a.
Unfortunately type-2a diamonds are quite rare (less than 2% of all gem quality diamonds). Also, because it is not easy to determine whether a type-2a diamond has gone through HPHT, GIA will not usually test for it. Instead, GIA has an agreement that all HPHT diamonds are laser inscribed to indicate that the diamond has undergone the HPHT process. The only problem with this is that a laser inscription is not permanent and may be removed by re-polishing or re-cutting.
Would I recommend a clarity-enhanced diamond? I think that the answer depends too much on your personal circumstances. I don’t think it’s fair to say that you should avoid all clarity-enhanced diamonds. Neither do I like vendors downplaying the issue that a diamond is laser-drilled or fracture-filled; certainly much worse if there is any misrepresentation involved. Just be more careful if you are being sold a clarity-enhanced diamond and assess whether you are being offered a fair price for it by comparing with other stones with its original clarity grade before the enhancement. Finally, do not expect that an HPHT diamond will be priced significantly lower than its natural counterpart. A good approximation is about 15-20% cheaper.