Diamond enhancements are specific treatments, performed on natural and sometimes synthetic gems (usually those already cut and polished into gems), which are designed to improve the gemological characteristics ? and therefore the value ? of the stone in one or more ways. These include clairty treatments such as laser drilling to remove inclusions, application of sealants to fill cracks, color treatments to improve a white diamond's color grade, and treatments to give fancy color to a white or off-color diamond.
Government agencies such as the FTC 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, if for no other reason than a fear of damaging consumer confidence.
Treated diamonds usually trade at a significant discount to untreated diamonds. This is due to several factors, including relative scarcity ? a much larger number of stones can be treated to reach gem quality than are found naturally occurring in a gem quality state ? and the potential impermenance of various treatments. Therefore, it is unusual to see a diamond with good overall gemological characteristics undergo treatment. Diamonds which are chosen for treatment are usually those that would be otherwise difficult to sell as gem diamonds, where inclusions or fractures noticeably detract from the beauty of the diamond to even casual observers. In these cases, the loss in value due to treating the diamond is more than overcome by the value added by mitigating obvious flaws.
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 diamond are fractures (commonly called feathers due to their feathery whitish appearance), and solid foreign crystals within the diamond; such as garnet, diopside, 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.
The combustibility of diamond has allowed the development of laser drilling techniques which, on a microscopic scale, are able to selectively target and either remove or significantly reduce the visibility of crystal oriron oxide-stained fracture inclusions. Diamonds have been laser-drilled since at latest the mid-1980's. Laser drilling is often followed by glass infilling.
The drilling process involves the use of an infrared laser to bore very fine holes (less than 0.2 millimeters or 0.005 inches in diameter) into a diamond to create a route of access to an inclusion. Because diamond is transparent to the wavelength of the laser beam, a coating of amorphous carbon or other energy-absorbent substance is applied to the surface of the diamond to initiate the drilling process. The laser then burns a narrow tube to the inclusion. Once the included crystal has been reached by the drill, the diamond is immersed in sulfuric acid to dissolve the crystal or iron oxide staining. This process is not effective for inclusions which are diamonds themselves, as diamond is not soluble in sulfuric acid.
Several inclusions can be thusly removed from the same diamond, and under microscopic inspection the fine bore holes are readily detectable. They are whitish and more or less straight, but may change direction slightly, and are often described as having a "wrinkled" appearance. In reflected light, the surface-reaching holes can be seen as dark circles breaching the diamond's facets. The diamond material removed during the drilling process is destroyed, and is often replaced with glass infilling, using the fracture filling techniques described below.
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