Fracture Filling
Fracture filling as a method to enhance gems has been found in gems over 2,500 years old.

But the diamond’s unique refractive index required a more advanced solution than simple wax and oil treatments.

This technology became available roughly 20 years after the time the laser drilling technique was developed.

Simply put, “fracture filling” fill tiny natural fractures inside diamonds, and make them less visible to the naked eye or even under magnification. Fractures are very common inside diamonds and are created during the diamond’s creation in the earth’s crust.

As the rough diamond travels up from the earth’s crust through volcanic pipes it comes under extreme stresses and pressures, and during this travel tiny fractures can form inside the diamond. If these fractures are visible and damaging to the beauty of the diamond, it will have much lower demand and won’t be as salable to jewelers and the general public, making them candidates for fracture filling and thus visually improve the appearance of the diamond.

The solution present in fracture-filled diamonds can usually be detected by a trained gemologist under the microscope: while each diamond gets a treatment that fits its unique shape, state and fracture status, there may be traces of surface-reaching bore holes and fractures associated with drilled diamonds, air bubbles and flow lines, which are features never seen in untreated diamond.

More dramatic is the so-called “flash effect”, which refers to the bright flashes of color seen when a fracture-filled diamond is rotated; the color of these flashes ranges from an electric blue or purple to an orange or yellow, depending on lighting conditions (light field and dark field, respectively).

The flashes are best seen with the field of view nearly parallel to the filled fracture’s plane (although specific fractures in untreated diamonds may cause similar “flash effect”).

It is important to note that while fracture filling is a durable process, some solutions are damaged and may even melt at certain temperatures (1,400 °C or 1,670 K), causing the diamond to “sweats” the solution under the heat of a jeweler’s torch; thus routine jewelry repair can lead to degradation of clarity caused by the loss of the solution used to fill the cracks, especially if the jeweler is not aware of the treatment.

It is notable that most major gemological laboratories, including that of the influential Gemological Institute of America, refuse to issue certificates for fracture-filled diamonds. Labs that do certify these diamonds may render any treatment benefit moot by disregarding apparent clarity and instead assigning the diamond a grade reflecting its original, pre-treatment clarity. This has raised quite a commotion, as this puts fracture-filled diamonds outside of the traditional realm of diamond certification, damaging their legitimacy as mostly natural diamonds. This demand for clarity enhanced diamond grading has caused the creation of new labs or an update to existing lab procedures to include remarks regarding any clarity enhancements procedures (drilling, fracture filling) into their regular reports, boosting the validity of this trade.