Oval Cut Diamonds Buying Guide

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May 21

Oval Cut Diamonds are a trendy alternative to traditional round brilliants but leak more light and exhibit a prominent bowtie effect that can be unappealing.

Fortunately, it's possible to minimize the bowtie effect by adhering to specific facet designs and proportions. We'll show you how in this response to the following client inquiry:

"Hi Todd, I’ve been searching for oval cut diamonds for a while. It seems to be a fairly uncommon shape in stores. Are there any ideal proportions for oval-shaped diamonds that you can recommend?"

Oval Diamond Brilliant from Blue Nile.

Oval Cut Diamonds from Blue Nile.

"I’m on a budget of about 2500 dollars for the diamond itself, and half-carat to three-quarter carat seems to be the range for my budget. At least, based on what I’m seeing in oval brilliant-cut diamonds with D-E-F color, and good symmetry."

"is there a specific range for total depth and table size that you recommend for this shape? Should I also be considering the crown and pavilion measurements? Thank you." – Stefan

Oval Cut Diamonds Proportions Chart:

The American Gem Society Laboratory (AGSL) does issue overall cut grades of AGS Ideal-0 for oval brilliant cut diamonds. It depends on the cumulative polish, symmetry, proportions, and light performance grades.

In that case, very few cutters submit their oval brilliant-cut diamonds to the AGSL for grading. After all, it is extremely unlikely that they will receive an overall cut grade of AGS Ideal-0 for fancy shape diamonds.

A few diamond cutters like Brian Gavin produce ideal fancy shape diamonds. His production routinely gets an overall cut grade of AGS Ideal-0 on the Platinum Light Performance grading platform.

Unfortunately, Brian Gavin has yet to produce an oval brilliant cut diamond. Perhaps he'll tackle that project soon and discover a way to improve the light performance of this shape.

Meanwhile, the AGSL does not publish the proportions criteria for oval brilliant-cut diamonds. Thus I cannot provide you with the AGSL parameters describing the ideal proportions for oval cut diamonds.

However, I find the legacy proportions chart by Gemologist David Atlas to be a good starting point. David is the founder of Accredited Gem Appraisers, but has since retired. Note that I only use this information as a guideline and additional information is essential to making a good choice.

Oval Diamonds Proportions Chart

AGA Proportions Chart for Oval Brilliant Cut Diamonds.

Selecting Oval Cut Diamonds By the Numbers:

ASET Scope Blue Nile Oval Cut Diamond

ASET for Blue Nile Oval Diamond.

One of the challenges with picking an oval-shaped diamond by the numbers is that the GIA does not provide full details. Specifically, the GIA does not provide the crown or pavilion measurements.

In other words, they only provide the total depth, table diameter, and girdle thickness. Under those circumstances, you are essentially buying blind.

In that case, it is essential to work with a vendor who provides complete details. However, there is still a lot that we can tell from images that show the side profile.

We can also use ASET and Ideal Scope images to see how evenly the diamond is reflecting light. Only a few vendors provide these images for fancy shape diamonds. However, I can sometimes get them from the supplier, as I did with this oval-cut diamond from Blue Nile.

ASET and Ideal Scope Images for Oval Cut Diamonds:

Ideal Scope Blue Nile Oval Cut Diamond

Ideal Scope Image for Blue Nile Oval Diamond.

The supplier for this oval-shaped diamond from Blue Nile also provides an Ideal Scope image. We use that device to determine how much light is leaking from a diamond.

It is essential to understand that all diamonds leak light to some degree. However, some diamonds leak more light than others. Generally speaking, oval cut diamonds are prone to light leakage.

That is due to the difference in the lengths of the crown and pavilion facets. Consequently, that is the same reason this shape also exhibit a bowtie effect as shown below.

Conversely, if ASET and Ideal Scope images are not available, you can buy those scopes from David Atlas. Please tell him that Todd from Nice Ice says hello.

What Is the Bowtie Effect in Oval-shaped Diamonds?

Oval Diamond Bowtie Effect

Bowtie Effect in Oval-Shaped Diamonds.

A difference in the length of the pavilion facets creates the diamond bowtie effect shown here. The specific facet structure can also affect the intensity of the bowtie effect.

Our oval-cut diamond buying guide provides more information about the different facet patterns. It is essential to know the crown and pavilion measurements because they also factor into the equation.

Those measurements and the degree of optical precision will also influence the degree of contrast brilliance. Optical precision is the consistency of facet shape, size, and alignment.

The symmetry grade on the diamond grading report does not take optical precision into account. You need an ASET Scope to evaluate that characteristic.

The Best Places to Buy Oval Cut Diamonds:

This article is built upon an inquiry sent through our free Diamond Concierge Service. In that case, we sent a handful of recommendations for oval-shaped diamonds that met our selection criteria.

Conversely, it's probably easier to let us search for diamonds, but it's still fun to do it yourself. In that case, here are the best places to buy diamonds online:

Please send us links to any diamonds that you are considering if you want our opinion. We're happy to look over the details and see whether we can provide any additional images. Please share this article on social media if you find it helpful. Thank you.

About the Author

Dive deep into the glittering world of diamonds with Todd Gray, the CEO of Gray Matter Development, LLC. Todd has 35+ years of experience as a diamond buyer and trade consultant. He ghostwrites content for several online vendors and is an avid Freediver, currently exploring the Cenotes of Yucatan, Mexico. Dive into brilliance with Todd Gray!