The Gemological Institute of America reports that a mined white diamond with an extremely thin layer of blue lab-grown diamond on top was submitted to its New York laboratory recently.
According to an article published online now and slated for the summer print edition of “Gems & Gemology,” the 0.33-carat stone is a composite of CVD synthetic Type IIb diamond overgrowth on a natural Type Ia.
The lab-grown diamond layer is only 80 microns (0.003 inches) thick, but it’s enough for the diamond to grade as a fancy blue.
Though the GIA said the stone was not submitted as a lab-grown diamond, there were a few things that tipped off researchers.
As the article states, the diamond had both nitrogen and boron defects. Nitrogen defects are the most common defect found in natural diamonds, while boron is the element that gives diamonds a blue tint and is a rare impurity, which is why natural blue diamonds are so few and so valuable.
The GIA said it is “very unusual” to see these two elements together in a single diamond, as essentially what they were looking at was a mixed Type Ia and Type IIb diamond. The last time the GIA reported on one of these being found in nature was nearly 10 years ago, in the spring 2009 edition of Gems & Gemology.
Secondly, a detailed analysis conducted using the DiamondView machine showed a yellowish-green fluorescence zone at the top of the crown that had a clearly defined boundary visible along the interface layer on the crown facets.
This, combined with SiV- defects and phosphorescence, indicated to GIA researchers that the top layer was a diamond grown using the chemical vapor deposition (CVD) process.