Diamond Cavity: Should They be Avoided?

All diamonds have imperfections, but some flaws are more impactful than others and can warrant a significant drop in value.

One example of a diamond inclusion is a cavity.

In this article, we’ll explore:

• An overview of diamond cavities 
• How they form 
• Their impact 
• Whether you should buy a diamond with a cavity

What is a Diamond Cavity?

A diamond cavity is an indentation on its surface that appears like a crack and extends inside. It’s a hole on the outside penetrating the diamond to form a crevasse.

Most cavities are small and invisible to the naked eye, but others are large enough to be seen without magnification.

They can appear almost anywhere on the diamond, and its exact position and size determine how much it affects the overall quality.

Check out the image below, where I’ve highlighted the cavity in a round-cut diamond.

It’s located on its table but is difficult to identify even in high-resolution.

You can visit the vendor’s website and rotate the image a full 360 degrees to view the cavity and other inclusions at multiple angles.

How are They Formed?

The most common way a diamond cavity forms is during manufacturing. 

When the diamond is polished to enhance its smoothness and shine, diamond cutters remove other inclusions from within the diamond, leaving the cavity on its surface.

This is often the case when there is a dark, noticeable inclusion in the diamond. 

The cutter decides it’s worth forming a cavity in order to remove the other inclusion.

For example, there may be a crystal lodged within the stone, and when it’s knocked out, a cavity is formed. 

In other instances, there are diamond feathers near the surface. If the feather is impacted during polishing, the void left results in a cavity.

Here’s a close-up view of what that occurrence of a cavity looks like.

Notice the slight, uneven dip that creates a rough surface in that area. In your ran your finger through the blemish, you’d likely notice it isn’t as smooth as the rest of its facets.

They also form naturally.

Diamonds are put under tremendous pressure when they’re created beneath the earth, so when an inclusion is dislodged during formation, it leaves that same indentation.

How Do Cavities Impact a Diamond?

1. Appearance

The degree to which a cavity affects a diamond’s appearance depends on its size and location.  The way you learn these details is through the GIA report.

Many online diamond vendors allow you to view the GIA report on their website in addition to a high-resolution photo of the diamond. 

For example, here’s the GIA report for a 1.50 carat diamond that two small cavities on the outer edge of the crown and pavilion.

They’re marked by a green oval with red lines through it.

These cavities are small enough to escape the naked eye, but the other flaws in this diamond result in visible inclusions.

It’s an example of how you should view the diamond’s inclusions holistically and how they affect its appearance.

Most diamond buyers are primarily concerned with how the diamond appears to the naked eye.

Small cavities on diamonds graded at least SI1 on the GIA clarity scale are generally not visible when viewed in a normal setting.

This is more often true for diamonds that weigh less than one carat.

For large diamonds with cavities, graded as slightly included, the indentations are more likely to be visible without a microscope.

Another way cavities impact appearance is by filling with dirt and grime over time. As you wear the piece of jewelry each day, it’s inevitable the holes will fill with debris.

So it’s important to keep a diamond with cavities clean and sparkling by having a professional cleaning once or twice a year.

2. Brilliance and Fire

The second aspect of a diamond that’s critical for buyers is its brilliance and fire.

Brilliance is the white light that reflects from a diamond, and fire is the flashes of color.

These features are primarily determined by the quality of its cut, but cavities also impact light performance.

Any inclusion has the potential to negatively affect the way light enters and exits the diamond. 

For cavities, you don’t have to worry as much about one near the girdle or crown. The area to watch is if a cavity has formed near the pavilion or on the table. That rule applies to other inclusions as well.

Take this GIA report as an example.

The reason this one is problematic is when light enters the diamond, the best performance results from the diamond’s internal angles directing it back out through the table.

A cavity inclusion prevents light from traveling out through the table at the perfect angle.

3. Durability

Even though diamonds are the hardest naturally-occurring substance on Earth, they’re vulnerable to chipping. Another reason to pay close attention to a diamond’s number and type of clarity characteristics is these flaws can make the diamond less durable.

Small cavities that aren’t located near the diamond’s edges generally don’t cause durability issues.

To illustrate, here’s a one-carat diamond that earned an SI1 clarity grade.

The GIA report notes one cavity is located on the pavilion. It’s not positioned near an edge. Combined with its size, there’s no reason to suspect challenges with durability because of that cavity.

On the other hand, be wary of diamonds with a large cavity in a place the diamond is already susceptible to a chip.

For example, princess cut diamonds are known for their squarish shape and sharp corners. This feature presents a downside because if the edges experience hard impact, it may break off.

The chances increase if there’s a cavity nearby.

As a counterexample, here’s a princess cut with a cavity positioned toward the middle of its table, which I’ve highlighted with a red arrow.

It isn’t as prone to chipping compared to if it was located near the sharp corner.

But to offset any risk, many buyers choose a type of setting that covers the weaker areas, while also hiding the visibility of imperfections.

4. Price

The best way to understand how cavities impact price is by comparing the prices of diamonds with various degrees of cavities and other inclusions, where all other qualities are equal.

For example, I compiled prices for one-carat round-cut cuts from James Allen. They had a very good cut grade, an F color, and VVS1 clarity grads. The average price was $7,436.

The average price for the same diamond, but with a VVS2 clarity is $6,821. That means the presence of a few additional inclusions such as cavities decreased the average price 8%.

If we opted for an SI1 clarity, which means the cavities and other inclusions could be noticeable without magnification, the average price is $4,555.

That’s a 33% decrease in price compared to VVS2 clarity.

As you can see from these examples, the presence of cavities and other inclusions significantly affects costs. 

You can expect anywhere from an 8% to a 20% decrease in price for each grade lower on the GIA clarity scale. 

That’s why I recommend starting your search at SI1 and moving up the scale from there until you find one that’s eye-clean. You’ll avoid the premiums charged for higher grades but still have a diamond that appears flawless.

Can They be Removed?

It’s natural to wonder if diamond cavities can be removed. 

The process of removing inclusions, or at least making them invisible to the naked eye, is called clarity enhancement.

The primary reason cavities aren’t fixed is because it would mandate the cutter reduce the overall weight. The rough stone would have to be cut even more, and the diamond would sell for less because it’s a smaller carat weight.

It’s a economic decision that opts for a larger diamond with the cavity inclusion over a smaller diamond without it.

If the cavities were to be removed or enhanced, there are two options available.

The first is fracture filling. The method involves filling the cavity with a glass-like substance. The refractive index of the glass is similar to a diamond, so the cavity becomes nearly invisible.

The fracture filling is apparent in the image below, but a quality treatment doesn’t stand out.

It’s only recommended for diamonds with small cracks, but even minor treatment results in it being less durable and valuable. 

The other method is less about filling the cavity and more about removing the accumulation within it. 

Boiling a diamond uses a mixture of strong acids and intense heat. The diamond is sealed in a pressure container, and once the process is complete, it’s cleaned again with the hopes its shine is restored.

Boiling a diamond is approved by the GIA, but my recommendation is to avoid these treatments altogether. 

Is a Diamond with a Cavity Worth It?

Don’t eliminate a diamond from consideration on the basis of a cavity.

All diamonds have some degree of inclusions, so the goal is to find the one that minimizes those imperfections while also staying within your budget.

But in the case of searching for my now-wife’s engagement ring, I did avoid a diamond with cavities. 

Instead, I chose a VS1 diamond that was eye-clean, and the inclusions had minimal affect on its brilliance.

If you’re considering one with cavities, there are a few aspects to consider. 

The first is size. If you want an eye-clean diamond where the cavities aren’t visible, ensure they’re only minor, especially on a larger diamond where inclusions are more likely to show.

Secondly, pay attention to the position. If the cavities are large and located near the edges, especially on a diamond with sharp corners, it could cause durability issues.

Thirdly, note how the cavities may impact its light performance. This is also related to their size and position, because larger cavities under the table or pavilion will likely have the most impact on its brilliance.

But with a better understanding of cavities and their effect on a diamond’s quality, you’ll be prepared to choose the right one for you.