What Are Fracture Filled Diamonds and Why You Should Be Careful

When choosing diamonds, it’s tempting to believe you’ve found a great deal, especially if the price seems too good to be true. But in the world of diamonds, you typically get what you pay for. A low price often signals a hidden issue. For example a poor cut quality, noticeable inclusions, or even a lower colour grade. However, one of the most subtle problems you might miss is a fracture-filled diamond.

What Are Fracture-Filled Diamonds?

In the last 8 years, I’ve personally come across two fracture-filled diamonds in our jewellery shops and studios. Both times, the customers had purchased diamonds from other sources and brought them in to include in a bespoke piece. So, what exactly is fracture filling, and why does it matter?

This is a treatment designed to enhance a diamond’s clarity. To improve the appearance of the diamond, a small laser is used to drill into the stone, reaching a dark inclusion. The cavity is then filled with a substance like glass or resin. While it can make the diamond appear clearer to the naked eye, it’s important to understand it’s a filled channel that is not diamond.

This treatment isn’t illegal, but it should always be disclosed to you at the time of purchase. Unfortunately, many buyers—especially those who purchase diamonds overseas or through friends—aren’t aware that the diamond has been treated. They might think they’ve got a great deal, not realising that they’ve paid more for a stone that’s been altered to look better than it is.

Why Should You Be Cautious with Fracture-Filled Diamonds?

While fracture-filled diamonds might look like a great find initially, there are significant downsides to this treatment. The most important concern is that they are fragile and prone to chipping or cracking. In fact, even something as simple as heating the diamond for resizing or small repair can cause the treated areas to react, potentially leading to the diamond exploding.

Another thing to consider is that they are too delicate for ultrasonic cleaning, which is a common method for cleaning jewellery. On the occasion we come across this at our free jewellery cleaning days we do not put them through the ultrasonic, instead advise customers to contact the original seller.

How Can You Identify a Fracture-Filled Diamond?

The good news is that fracture-filled diamonds are identifiable, even though they can be tricky to spot at first glance. The material used to fill the fracture often has a different refractive index than the diamond itself. This means light bends differently through the filled area, which can create a rainbow effect that doesn’t match the surrounding diamond. For a trained eye, this difference is relatively easy to spot.

In those I’ve seen, the fracture was usually small—just one channel filled with resin or glass. However, in some cases, multiple fractures can be filled. If you’re uncertain about the authenticity of a diamond, it’s always worth checking.

Always Know What You’re Buying

If you’re considering purchasing a diamond, make sure you’re informed about its treatment history. While it may improve the appearance temporarily, the risks and potential issues associated with fracture-filled diamonds could cost you down the line. My friend Julia goes into more detail about spotting fracture-filled diamonds, so you can be more informed before your purchase.