The Gemological Institute of America (GIA) has warned of “hybrid” diamonds entering the supply chain after uncovering a natural diamond with a blue synthetic coating.
Claiming that the stone was the first of its kind that the institute had encountered, it reported that a number of “unusual characteristics” gave away the gem’s synthetic nature.
It had both nitrogen and boron defects, which were described as a “rare combination”, and was also uncommonly a mixed Type Ia and IIb.
The ‘natural-synthetic’ gem was sent to the GIA’s New York lab as a natural fancy 0.33-carat blue diamond.
The stone has silicon deficiency defects, which although found in natural diamonds, had a unique combination of sharp boundaries, fluorescence, phosphorescence and sIV which suggested it was a chemical vapour deposition (CVD) synthetic.
The GIA stated that it was likely that there would be more discoveries of similar diamonds.
Its statement said: “Identification of colored diamonds should be performed very carefully by looking for unusual characteristics, such as a straight boundary line associated with an interface plane, and fluorescence zones with sharp edges in DiamondView images.
“Examination of this fancy-coloured composite diamond indicated that similar challenges could exist for colourless and near-colourless diamonds.”