Diamond Cut Types #illumedati 2

Hey guys, it’s Whatever Wednesdays again and I’m here to talk about Diamond Cut Types. I was originally going to talk about both Diamond Cut Types AND Diamond Grading, but then I realized that is way too long for one post.

Also, sorry for the late post. Both my kids were sick today…

Stock Photo From: Pexels

Ok, so in my prior post I gave a primer about Diamonds – What You Need to Know About Diamonds

As promised, I’m going to talk about cut type today… but not grading quite yet.

For those really interested, you can learn a ton more from Pricescope.com forum and I will include some educational links. However, that may be information overload for some, which is why I am writing these posts.

For the most part, this article will focus on Brilliance… because it is considered the most important. However, there are other considerations for a diamond’s beauty, including Fire, Scintillation, and Spread. I’ll go over this in more detail in a future post.

Round Brilliant Cut

This is considered the most traditional of all the cuts. As I stated before, it has been heavily studied and there is a lot of data on what is an ideal cut based on the Tolkowsky Ideal. In general, this cut has 58 facets and is considered the best way to make a diamond sparkle and therefore is the “most brilliant” cut. However, as with many things, that comes at a premium.

In order to cut a diamond as a Round Brilliant Cut, it may be difficult to maximize the carat weight of the rough diamond. (cutting for yield versus cutting for beauty)

In general, a Round Brilliant Cut will only retain 50% of the original weight of its rough.

For this reason, on a carat weight basis, keeping all the other C’s the same, you will most likely pay more for a Round Brilliant Cut.

In addition to that, in order to maximize the amount of sparkle the diamond has, the Round Brilliant Cut will need to be cut to the highest standard which is considered “ideal”. Be wary here. Just because a diamond is considered “ideal” or called “ideal” by the diamond store does not mean it is. As far as I know, only one gem lab certifies “Ideal Cut” Round Brilliants, and that is the American Gem Society (AGS). As such, if you truly want an ideal cut Round Brilliant, then you should make sure your diamond is AGS certified.

However, that does not mean that you can’t find “close to ideal” or even “ideal” diamonds that are GIA certified. However, GIA only certifies “Excellent” which is a range. It is possible to get a good deal on a diamond that is reasonably close to the Tolkowsky Ideal from GIA. I’ll explain this more in the Diamond Cut Grading post.

Because of the stringent standards of the AGS. I would be ok with buying an Ideal graded AGS diamond without seeing it in person.

Oval, Marquise, Heart and Pear Cuts

This is considered to be the “modified round brilliant” category.

If you consider a Round Brilliant to be 100% brilliance, then these would fall into the category of maybe 85-90% brilliance.

Unfortunately, these kind of cuts do not carry an “ideal” grading anywhere. This is probably because the standards for how they are cut can vary widely along with the significant variations in shape. For this reason, I would not buy any of these diamonds without visual inspection first.

This shape usually results in some degree of a “bow-tie” effect. This is usually not visible from pictures alone. Essentially, it’s a leakage of light where no reflection occurs and thus “light is absent”. How much of a “bow-tie” you are ok with will vary with each individual. For this reason, visual inspection is a must, preferably in a normal lighting setting (mild overhead fluorescent lighting or low light in a dinner setting).

Beyond4Cs has a good writeup on the bow-tie effect here. If you are considering this cut type, I would recommend visiting his site. Although he seems to be ok with viewing diamonds on a site with 360 degrees of viewing, I would not be comfortable buying with that alone. You should decide what you are ok with.

Princess Cut

The Princess Cut gets special mention here because it was en vogue for a few years. It is the 2nd most popular shape, behind the Round Brilliant.

While it was created in the 1960s, it recently gained popularity in the last 10-20 years. If a Round Brilliant is 100% brilliant, then a Princess Cut is probably around ~75% brilliance.

In general, a Princess Cut will retain 80% of the original weight of its rough.

Where did this popularity come from?

Well, I don’t know for sure, but it was probably a combination of marketing and celebrities getting married. For a short time period it seemed like a lot of celebrities were buying princess cut diamonds. It’s true name “Square Modified Brilliant” probably doesn’t sound as good as “Princess”

Why do you think it became popular?

Well, a few reasons.

  1. Carat size. A Princess Cut diamond will cost less per carat weight than a similar Round Brilliant.
  2. It faces up big. For the same carat weight, a Princess Cut diamond will have a larger face up area. (A square of the the same length is larger than a circle.)
  3. It’s different. People wanted to be unique and step away from the “boring” Round Brilliant.


I almost bought a Princess Cut Diamond. They are very nice diamonds, and also, an “ideal” grading for them does exist through AGS.

However, I opted for the traditional Round Brilliant because it was “classic” and “timeless” in my opinion.

In the event that I was going to buy a Princess Cut, I would have been ok with buying it sight unseen as well because stringent AGS standards are also in place for this cut.

Cushion, Emerald, Asscher and Radiant Cuts

Since these are less common, I will talk about them all together.

All of these cuts are ~60% brilliance compared to a Round Brilliant. **Royal Asscher cuts are slightly more.

Overall, the real reason to buy these cuts is because of their distinctive shape. This lends to different kinds of sparkle, ie. “broader flashes of fire” or smaller bursts of “pinfire”.

In particular, I think the Royal Asscher cuts are very interesting… and I considered buying one, but only very briefly.

However, because of the wide variation in these styles, it is difficult to grade them accurately. For this reason, I would not recommend buying these kinds of cuts sight unseen.

For completeness’s sake, AGS does publish their guidelines for Round, Princess, Oval, and Emerald cuts.

Just a warning: Those documents may make your eyes bleed with information.


There are more cuts of diamonds than you might think.

Round Brilliants are “classic”, but you will pay a premium for it. If you want an “Ideal Cut”, make sure it’s certified by AGS.

If you are ok with “near Ideal”, then GIA is an option. I’ll go over this more in my next post.

Princess Cuts are the second most popular, but are rated as “Ideal” for AGS.

All other cuts are difficult to assess sight unseen in my opinion.

I’ll go into more depth on Diamond Grading in my next post… although it may be a few posts.



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