The 0.64-carat stone was surrounded by about 0.10-carats of Chemical Vapour Deposition synthetic diamond, with the GIA noting its colour was noticeably different from the natural material.
The outer layer was greyish-blue, while the inside was yellowish, giving the stone a fancy greenish-blue appearance.
It’s the second time the GIA has identified such a stone: a 0.33-carat fancy blue diamond was found to have the same type of synthetic layer back in 2017.
“With the second of these composites seen at GIA, this could be a new type of product entering the market,” research associate Troy Ardon and analytics technician Garrett McElhenny wrote in a lab note, published in the spring 2019 issue of the GIA journal, Gems & Gemology.
Meanwhile, 25 undisclosed synthetic diamonds were recently submitted to a GIA lab in California, with 16 showing unusual signs of colour. They ranged from faint yellow-green to very light green – the result of higher nickel concentrations. The synthetic diamonds were created using the High Pressure-High Temperature method.