Enhanced Diamonds
Diamond "enhancements" are specific treatments performed on cut, polished natural diamonds, which are designed to improve the visual or gemological characteristics of the stone, but not necessarily increase its value.
Minor inclusions or surface imperfections which are not visible to the naked eye ("VVS1" to "SI2") can be disguised, altered, or removed by employing several invasive techniques from fracture filling to laser drilling. These techniques do not eliminate the imperfection, but instead attempt to hide their visual effect.
There are also heating treatments to improve a white diamond's color grade, or treatments to give a fancy color to a off-white diamond. A trained gemologist should be able to identify most traditional "enhancements" made to a particular stone.
 Unfilled Fractures around Garnet Inclusion - © AGS Lab |
 Telltale Signs of Fracture Filling - © AGS Lab |
Diamonds that have been altered or enhanced by Fracture Filling and/or Laser Drilling should always be labeled and their "improvements" identified to the potential consumer, in accordance with Federal Trade Commission (FTC) guidelines for the gem trade.
Diamond Fracture Filling
Diamond clarity is sometimes improved and enhanced by filling tiny fractures or feathers with molten glass, much like you would repair a crack in a car's windshield glass. Such diamonds are sometimes then branded as "fracture filled diamonds." Reputable filling companies will always use filling agents which show an orange or pink flash of color when viewed under a microscope with certain controlled lighting conditions.
There should always be a significant price discount for any diamond that has been fracture-filled, and the GIA will not even grade a fracture-filled diamond, in part because the treatment isn't permanent.
Due to its low melting-point, the heat generated by a blowtorch used to work on settings can cause damage to the filling material. It is therefor essential to inform anyone working on a setting where the diamond has been fracture-filled, so that the jeweler can use greater care while working on the piece. Reputable filling companies will often provide repeat treatments if heat causes damage to the filling.
Laser Drilling of Diamonds
Laser drilling involves the use of a laser to burn a tunnel or hole down to any dark carbon inclusions or piqué, followed by acid washing to remove the coloring agent. The drilling process leave tiny telltale shafts or tunnels that are visible under high magnification (see photos below).
 Signs of Laser Drilling - © AGS Lab |
 Laser Drilling Tubes - © AGS Lab |
The laser-drilling treatment is considered permanent, and both the GIA and AGS will issue grades for laser drilled diamonds. The final clarity grade will be the grade that is assigned after treatment. According to Fred Cuellar in his book How to Buy a Diamond, "One out of every three diamonds sold in the United States is laser-drilled."
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Bibliography on Diamond Enhancements
1. Dept of Geology, UofG, Mineral inclusions from African & Brazilian Diamond 
. www.minsocam.org
2. , Inclusions in Diamonds from K14 and K10 Kimberlites. www.sciencedirect.com
3. V R Howes 1962 Proc. Phys. Soc., The Graphitization of Diamond . www.iop.org
4. Nature Article, Growing Diamond Crystals . www.nature.com
5. Steve Sque, University of Exeter, Physical Properties of Diamonds . www.newton.ex.ac.uk
6. Wired magazine, The New Diamond Age . www.wired.com
7. Nano Diamonds, The High Strength-To-Weight Ratio Diamonds . www.nanodiamond.info
10. Chemical & Engineering News, Man Made Diamonds . www.pubs.acs.org
8. Adamas Gemological Laboratory, Spectrophotometers to Measure Gem Color . www.gis.net
9. GIA, Gemological Institute of America . www.gia.edu
10. AGSL, American Gem Society Laboratories . www.ags.org
On To: Diamond Chemistry & Composition
