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Diamond Culet: Does It Affect Diamond Value?

Diamond Culet: Does It Affect Diamond Value?

When deciding on a diamond, there are a few pointers everybody relies on, such as cut, color, clarity, and carat. But there are a few more unsuspected features that can impact the price of a gem. 

Have you ever considered that the diamond culet might be amongst them? And while we’re at it, is there a legitimate reason to suspect that it’s a factor in diamond value? 

A culet is often referred to as one part of a diamond – but if you’re interested in learning why it’s specifically listed in some grade certificates, stay right here. We have a lot to talk about today!

What Is A Diamond Culet?

A culet (pronounced kyoo-lit) is a term generally used to describe the large bottom section of the diamond. But in reality, it’s a bit more specific and refers to a single bottom facet, or the absence of one, for that matter. 

Yes, that indicates that there is such a thing as a diamond that lacks the bottom facet – but that doesn’t mean it’s without a culet! Now, to grasp how a culet is created in the first place, you should take a quick look at diamond facet positioning achieved during the cutting process:

  • Table – The top facet that has the most critical role in gathering the light beams
  • Star – Smaller facets arranged around the table facet
  • Crown – Facets that build the upper diamond surface
  • Girdle – Perimeter facets that separate the top and the bottom of a gem and extend to both of those parts 
  • Pavilion – The bottom facets that come together and form a culet
  • Culet – The point in which pavilion facets meet (or an extra facet in that spot)

As mentioned, the pavilion facets are cut uniformly so that their tips all reach one point – at least, that’s the goal. What does this mean? 

Well, if they adjoin at the perfect angle, a sharp end will be created. This kind of facet position is desirable for a better cut grade.

But sometimes the culet looks different. It can also be a plane of a certain size that’s polished and parallel to the table facet – as if it is a smaller version of it. 

Sometimes such a culet results from sized pavilion facet angles, or it can be added to a sharp tip on purpose. You can look at two types of round brilliants for comparison: One can have 57 facets and the other 58 – the added one being the culet facet.

But the stones most famous for having distinct culet planes are, without a doubt, antique cuts – gemstones that are more than 100 years old. That’s the only scenario where a sizable culet is worthwhile. They include the frequently mentioned Old Mine Cut and Old European that can be recreated using old-school methods by experienced cutters

There are many notable differences between old and modern cuts, with the cushion cut being the prime example of it. You can learn more about it in this article

How Are Diamond Culets Evaluated?

Certified diamond grades in laboratories such as GIA are in charge of performing the appraisal of diamond culets. It’s worth noting that it can be done in a few different ways.

A non-contact optical measuring device – the GIA Multi-Purpose Gemological Reticule – or even a standard gemological microscope – can be used. They have the same purpose, though – to determine the size of a culet.

That’s a crucial step when having your gem appraised according to GIA’s Cut Grading System. 

Why? Well, a culet can change the face-up appearance of a stone. Don’t worry; we’ll be more specific in a few moments. 

First, you should know that experts take a look at the stone face-up under 10x magnification so that they’re looking at the culet through the table facet to determine the significance of the culet size. 

Besides this visual observation, researchers also use computer modeling to have more precise results. All these techniques finally add up to one formula: 

culet Size % = culet size (mm) X 100 average diameter

As stated, the measurements of a culet are expressed as a percentage relative to the average diameter of the diamond. Experts will generally use this formula as a guide when assessing a culet’s impact on a specific stone. 

But just like all other calculations, this one depends on the external factors, too, since all those mentioned devices can have inherent variabilities. Plus, there are often specific clarity issues or irregularities in shape or angle. If you’d like to read about diamonds’ irregularities, take a look at this article.

That’s why the final call is made by visual determination. Hence, graders often use photographic references. The whole process is then completed by placing the stone in the suitable culet grading category established by GIA. 

GIA’s International Diamond Grading System – Culet Size

There are a few precise categories outlined within this reputable grading system:

  • None 
  • Very Small 
  • Small (around 1,5% average)
  • Medium (around 3% average)
  • Slightly large (around 5% average)
  • Large (around 7% average)
  • Very Large (around 11% average)
  • Extremely Large (around 15% average)

Culets in the category of Medium or smaller are invisible to the naked eye and, as such, don’t affect the value of the stone. Culets of larger size can be considered an inclusion, dead area, or loss of light. 

That’s not an issue when the pavilion facets are perfectly pointed, and the culet is described as “None.” But in any other case, a culet is an additional facet of a specific size that’s parallel to the table.

Now, you’re probably wondering how much damage the flaws of a culet facet mentioned above can do – and that’s something we’ll get into in the following sections.

Diamond Culet & Diamond Light

A diamond prism creates four known light plays – but only two can be affected by the size of the culet. And those two, as you’re about to see, are brilliance and fire

Diamond Brilliance

Brilliance is thought of as the most critical light play of the lot – and it refers to the direction of the white light rays after they enter the stone’s prism. 

It doesn’t come naturally and is achieved thanks to fine cutting that catches light waves from any angle of the gem, pointing them to the top surface once they’re inside the gemstone – right in the viewer’s line of sight.

Of course, there’s a lot more you should know about brilliance, but we’ve covered that here. So, instead, we should move on to the second light phenomenon, known as fire.

Diamond Fire

It’s a well-known fact that diamonds “burn” more than any other material, producing a genuine rainbow! That essentially means they shine in a colorful flame of dispersed wave-lengths that separate from a white ray after a few bounces between the stone’s inner planes. 

And more bounces mean more flames! Then, they leave the gemstone in viewer-sight, much like brilliance – but you can find more on the differences between the two right here. We have other things to discuss in this guide!

End Result

It’s crucial for these two aspects of a stone’s light performance that the light remains inside the gem once it enters the planes. That’s why larger culets that imitate the table facet are an issue: They let the light waves out just as the table plane lets them in!

And in consequence, the light game can be diminished since the rays don’t get to stay inside the gem long enough to skip between the facets and create a light show. Instead, they exit the culet too soon. 

That, in turn, makes the culet look bad. The spots that let the light through turn into a dead area devoid of shine, as well. 

But here’s some good news: Scintillation, which has been proven to be the most relevant when it comes to a diamond shine, depends mostly on the movement of the light source, the stone, or their admirer.

Diamond Culet – Pros & Cons

A pointed diamond culet – and that of smaller size – is the right choice if you’re going for higher brilliance. However, that shine might light up a few problems. For example, such a tip can be very delicate and prone to chipping even with a touch of a finger. 

That’s why sometimes an extra facet is added to serve as coverage – a slightly larger plane that is parallel to the table facet. But even though it plays a protective role, it could also reduce the diamond’s shine. 

This can, indeed, be viewed as an antique charm – but are there any other solutions for those who prefer no culet at all?

Can A Diamond Culet Be Protected?

The Answer Is Yes and Yes! Diamonds are the hardest material ever known and earn a “perfect 10” on the Mohs scale of hardness. That means they can be scratched or scuffed solely by another diamond

Of course, this could be concerning if you have loose diamonds stored together. However, you can solve that by using diamond brifkas. If the name doesn’t ring a bell, we should mention you’ve most likely seen them in movies – and in most cases, they’re blueish paper bags.

These brifkas are layered, affordable, and convenient since they take up little space. And that’s mostly why they’re preferred over a Diafix with separated capsules, for example. 

So, that’s a short story about scratching a diamond. You can learn more about it here – since you’re probably more interested in breaking and chipping one at the tip.

Here’s the thing: When there are natural fractures inside the stone that grew at the same time as the gem itself, then, yes, a diamond can easily break if it falls at an inconvenient angle. 

However, when it comes to diamond culets, what should concern you most is chipping. You see, a diamond is deemed practically invincible but it has an Achilles heel – and that’s the culet.

It’s more delicate the more it’s pointed, and can be chipped sometimes even by the touch of the finger. That’s why it should be stored in the described brifka when transported as a loose piece – or set in a high setting band if part of a jewelry piece. 

This type of setting will separate the tip from the finger or the metal band. In some cases, diamond cutters will intentionally cut the tip to reduce the possibility of damage to a minimum. While we’re at it, we’d like to remind you to be careful when handling your stone while cleaning it – and be sure not to do it over a sink!

Related Read: How Much Force Does It Take To Break A Diamond?

Summary

Things aren’t always what they seem – that often pertains to diamonds, as well, and we can use the diamond culet as a shining example! It can be a tiny point or a large plane – but it’s so much more than a jewel part.

In reality, it’s the most vulnerable point of a stone and can be the cause of dullness and imperfection. Who would’ve thought something so minor could be so prominent, huh?

The fact is there are solutions to these challenges – and they include knowing the size of your gem’s culet, buying from an experienced jeweler, using a higher setting, and using a protective brifka when transporting a diamond.

But if you’re a fan of antique cut pieces, then you’ll probably recognize all of the imperfections caused by larger culet sizes as a touch of charm rather than something to worry about – even if the risk of chipping is higher.

That being said, both larger and smaller culets have their strengths and weaknesses. So, that comes down to your personal preference – and that’s the best criteria there is!