GIA Detects Fracture-Filled Diamonds in Jewelry

The Gemological Institute of America (GIA) recently examined a pair of diamond earrings and a necklace that showed fractures containing a glass-like material in some of the stones.

The GIA received the jewels at its Jewelry Analysis Service at the India International Jewellery Show (IIJS) Premiere in August 2025. The institute studied them at its Mumbai laboratory, it wrote in the winter edition of Gems & Gemology, its quarterly journal. The necklace comprised 14 round brilliant-cut diamonds totaling 15.27 carats, and the earrings featured pear-, oval-, and marquise-shaped stones weighing a combined 10.84 carats.

A spectroscopic analysis confirmed that the mounted diamonds were all natural. The GIA observed findings — including rainbow-tone reflections, a flash effect, and cloudy, milky areas — that established two round diamonds on the necklace and one marquise-cut diamond from the earrings had undergone fracture-filling treatment.

Fracture filling is a clarity-enhancement technique that aims to improve a diamond’s apparent clarity by filling surface-reaching fractures with a glass-like material. This filler, typically a lead-based glass, closely matches the refractive index of diamond, thereby reducing the visibility of fractures and creating the appearance of higher clarity, the GIA explained. While some clarity-enhancement methods are permanent, fracture-filling is not: The filler may change color or degrade, especially when exposed to ultraviolet light, heat, ultrasonic cleaning and specific chemicals.

This kind of unstable treatment has a significant effect on a diamond’s value, durability, and care requirements, the GIA pointed out. Due to these concerns, its labs do not issue grading reports for fracture-filled diamonds.

Image: A fracture-filled diamond. (Gemological Institute of America)