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The Definitive Guide to the Round Brilliant

By Lead Gemologist, GG. Erica Hirsch

Traditional and classic, yet versatile enough to adorn any trendy engagement ring creation you can dream up.  Alone, surrounded, or flanked, the Round Brilliant Cut (RBC) is a crowd pleaser. For that reason, rounds tend to be more expensive, per carat, compared to other shapes.

How do you find the round diamond that’s right for you? We have assembled our best intel here. Using our education and experience, we hope to assist you on your journey to find the diamond you will adore.   

The 4 C’s for Round Diamonds

Color in Rounds

Round shaped diamonds hide color pretty well.  An I graded colored diamond can appear pretty colorless in the real world.  

Quick tip — if considering a setting with multiple stones, make sure they are “color matched.”.

Read up on the science behind fluorescence if you are so inclined. In person, you will find it undetectable to the naked eye. Fluorescence does not affect a stone’s integrity. Diamonds with fluorescence typically cost 10% to 20% less. In addition to cost savings, fluorescence can improve the appearance of a diamond’s color by up to two shades in color grades H through K.  We suggest allowing up to medium fluorescence in grades E-G, and up to very strong fluorescence in color grades H-K.

Diamonds are graded for color with their top side facing down. Because of this, you may come across the term “face up.” This is used to explain that a stone’s color may appear different than it was graded.

Example: An I grade diamond can appear as light as H face up, and even closer to G if it has strong fluorescence.  In the J, K, and onward grades the recipe is less dependable.

Quick Tip — yellow gold can actually make a warmer, more yellow diamond appear whiter. 
The same J colored diamond set in yellow gold appears whiter.

Clarity in Rounds

Round cut diamonds hide inclusions (flaws) pretty well. Within the diamond trade, a stone may be described “eye clean” to which most gemologists would inquire, “who’s eyes?”  The industry defines “eye clean” as “free of inclusions visible with normal vision from a distance of 6-12 inches.”

Diamonds are reflective by nature, hence the sparkle. This also means a single inclusion can be reflected, like a hall of mirrors. Not great news, we know, but try your best to detect this using the certificate and your eyes.

Clarity grades are based on the size, location and number of inclusions.  Inclusions can disrupt light interaction. Think of them as roadblocks. With rounds, try to avoid black crystals on the table. Too many small black crystals can also make a diamond look gray. Feathers are colorless and acceptable if they do not reach the girdle. Twinning wisps are no problem when there are just a few.  Pinpoints are fine, as long as they appear in small numbers. Needles are typically small and undetectable.

Avoid any diamonds with the following: cavity, knot, chip, laser drill hole, etch channel, pit, indented natural and certain feathers. Not sure what you’re looking at? Check out our inclusion guide.

These inclusions could impact the integrity of the diamond, leaving it vulnerable. Diamonds are hard, not tough. You wouldn’t think twice about cutting something with a sharp knife on a ceramic plate, but think how careful you are when placing it in the sink.

Occasionally, we are able to hide an inclusion under a prong — it would be our secret.   

Bottom line, it may take some hunting to find the perfect round brilliant, but it’s what we love doing, and we are here to help.

Carat and Cut for Rounds 

There is a relationship between Carat and Cut.  When viewing two 1 carat diamonds, one with a Poor cut the other Very Good, the poorly cut diamond will not sparkle well.  Even if the diamond has high grades in other areas, it will perform poorly. A poorly cut round diamond will also look far smaller than a well cut one, because of it’s deeper proportions. Other poorly cut diamonds may look larger than a well cut one, but are too shallow to perform well.  

No one should pay for carat weight they cannot see. Understanding the relationship between carat and cut is essential. Girdle and total depth (pavilion) areas are prone to unnecessary bulk. Since diamonds are sold by weight the practice of leaving extra behind to increase cost without any benefit to performance has been one of the industry’s best-kept secrets. Our reference guide will help you avoid this. Girdle, total depth, and crown angle proportions can make or literally break your stone.

You may come across stones that claim to be cut or faceted differently.  In fact, stones that are well faceted (triple X’s, excellent in all grades) will show hearts and arrows without extra attention. Those with additional faceting on the underbelly of a diamond are not likely to increase your sparkle.  Keeping your diamond clean is all you need to see those sparkles.

Anatomy of a Round Brilliant

Diagram of a diamond depicting the girdle. The long thin piece that divides the top from the bottom.

Girdle

Accept: Thin – Thick

Avoid: Very Thin & Extremely Thick

Why: Very thin girdles can chip or crack. Very thick means you are paying for weight you can’t see. Loses sparkle.

Diagram of the table of a diamond. The flat long part on top.

Table

Accept: 54 – 65

Avoid: < 54 or > 63

Why: Light should bounce off the table like sun off of a window.

Diagram depicting a diamonds overall depth. The point from the top of the diamond down until the culet or bottom of the diamond.

Total Depth

Accept: 58-62.5

Avoid: < 58 or > 63

Why: You are paying for weight you can’t see. Loses sparkle.

Crown Angle

Accept: 32.5-34.5

Avoid: < 32.5 or > 34.5

Why: Can appear too high or flat like a pancake. Can disrupt light

Selected style

Parker No. 7

Round Bezel

Shown in 18K Yellow Gold