ラボの記録 Gems & Gemology, Summer 2018, Vol. 54, No. 2

A Repaired Diamond


修復されたダイヤモンド
Figure 1. A face-up photo of the repaired diamond. Photo by Robison McMurtry.

A 1.38 ct marquise-cut diamond (figure 1) was submitted to the Carlsbad lab for colored diamond grading services. It was initially noted that large fractures and a large cavity were present on the table. Careful examination of the stone with a gemological microscope revealed that it had previously broken in half and been repaired with an unknown adhesive. The first clue was a large fracture from the crown to the pavilion that showed a sizeable gap present throughout the stone. Further­more, the facets the fracture passed through all showed slight to moderate misalignment, which cannot happen during polishing (figure 2). Finally, large trapped air bubbles could be seen in the fracture when viewed at an angle. These clues proved that the diamond had broken and been put back together again, though not perfectly. Polish lines on the pavilion facets showed a pattern that would line up if not for the fracture separating them, demonstrating that the breakage occurred after the diamond had been at least partially polished. Beyond that, it is impossible to tell when the damage occurred.

Bezel facet of repaired diamond.
Figure 2. A bezel facet of the repaired diamond as seen in reflected light. The wide fracture can be seen cutting across the facet, and the upper edge of the facet does not form a straight line. Photo by Troy Ardon; field of view 3.3 mm.

Diamonds have been adhered together with glue to form a diamond-diamond doublet (E. Barrie and E. Biermans, “A different type of deception: ‘Diamond-diamond’ doublet,” HRD Antwerp, 2014, www.hrdantwerp.com/en/news/a-different-type-of-deception-diamond-diamond-doublet), but a broken diamond that has been repaired was not something previously reported by GIA. The fracture in the item was not a flat, straight surface but very irregular, indicating that it was not two separate diamonds glued together to make a larger diamond, but rather a repair. Since the item was simply two pieces of diamond joined together, it was not eligible to receive a diamond grading report. None of the 4Cs apply to a composite such as this (e.g., the carat weight of the item was actually the sum of the weights of two diamonds plus the weight of the adhesive). The decision to repair a diamond in this manner is unusual. Careful gemological examination will, however, reveal the repair work done.

Troy Ardon is a research associate at GIA in Carlsbad, California.