Glued-Together Diamond Turns Up at GIA

Carlsbad, Calif.—The Gemological Institute of America said its Carlsbad lab recently received a diamond that had broken in half and been repaired with an adhesive of some sort.

In the summer 2018 issue of Gems & Gemology, GIA research associate Troy Ardon wrote a lab note about a 1.38-carat marquise-cut diamond submitted to the laboratory for colored diamond grading services.

Graders initially noted large fractures and a large cavity on the table. After careful examination under a microscope, they discovered that the stone had been broken in half and then repaired with an “unknown adhesive,” a method the lab noted was unusual.

The GIA said there were a number of factors that hinted to it being broken and put back together imperfectly, the first being a large fracture from crown to pavilion showing a “sizeable gap” throughout the diamond.

The fracture indicated it was a repair, rather than two separate diamonds glued together to make a larger stone, because it had an irregular surface, according to Gems & Gemology.

From a certain angle, graders could also see large air bubbles trapped in the fracture.

Additionally, the facets that the fracture transected showed “slight to moderate” misalignment, which the GIA confirmed can’t happen during the polishing process.

The GIA said polish lines on the pavilion facets contained a pattern that would’ve lined up if it wasn’t for the fracture that separated them, demonstrating that the breakage occurred after the diamond had been at least somewhat polished. Beyond that, it’s not possible to tell when the damage happened, the lab said.

While the application of glue to diamonds to form a diamond-diamond doublet has been done before, the GIA noted that it has never seen a broken diamond repaired with adhesive in this manner.

The lab was not able to grade the diamond because the 4Cs don’t apply to “composites” like this. For example, the carat weight would actually represent the sum of the two diamond weights plus that of the adhesive.