Diamond Drilling – the Science Behind the Book

As the old line from the Bionic Man goes “We can rebuild him, we can make him better than he was.”  The same holds true for diamonds.  The main solution that is employed is diamond drilling.

As any good bride could tell you, there are 4 prime factors in a diamonds value.

  • Cut – The cut of the diamond is the prime control of the diamond’s optical qualities.
  • Color – The lack of color is important.  Particularly Yellow Diamonds are considered of less value.
  • Clarity – The clarity of a diamondis decided it’s inclusions
  • Carat Weight – the size of the diamond

Carbon diamond inclusions – the black specs in the image

It’s the 3rd factor that is interesting.  By removing inclusions, the price of a diamond can be improved.  General types of inclusions:

  • Clouds
  • Feathers
  • Included crystals or minerals
  • Knots
  • Cavities
  • Cleavage
  • Bearding
  • Internal graining

(from Wikipedia – more on inclusions here.)

So the question then is, how to clean up inclusions?  Again from Wikipedia:

Laser drilling

Diamond lasers now are used to inscribe stones

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 or iron oxide-stained fracture inclusions. Diamonds have been laser-drilled since at least the mid-1980s. Laser drilling is often followed by glass infilling.

The drilling process involves the use of an infrared laser (wavelength about 1060 nm) 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 thus 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.

So there it is – the basics of how diamonds are cleaned with lasers.  Enjoy!


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