All About Diamond Cut, Technicalities and Common Sense in Diamond Shopping

In this post, ( third in the 4 C’s series), I will  give you an overview on what you need to know about diamond cut. This should help you keep the confusion away while you’re shopping for your diamond.

I’ll get technical with how to read the diamond grading report, but also arm you with common sense.

Let’s Talk About Diamond Cut

If you’re not a technical details person just skip that part. The aim here is to make your diamond search easier to confront and to arm you with the data to feel confident in your choice of a diamond.

It’s Diamond Cut “Type” not Cut “Shape” We’re Talking About Here

Before we get started, let’s clear something up. Diamond Cut and shape are two words often used interchangeably but can mean different things. Diamonds come in many shapes: round, rectangular, triangular, oval, etc.

No matter the shape, every diamond has been cut by a professional gem cutter. The skill of the cutter goes far in determining the beauty and price of the diamond.

From Lump to Sparkly Beauty

Envision starting with a dull lump of rough diamond. To the average person, it looks like an ordinary pebble you’d find on the beach.  It’s not shiny. It doesn’t sparkle. Without a degree from the GIA, (Gemological Institute of America) you’d be hard pressed to know it’s a valuable diamond.

Now picture five 100% identical rough diamonds sitting in front of you. Stay with me. Hold on to that picture.

Give each one of these five stones to a different man or woman sitting in front of a big horizontally spinning metal wheel. These people are all diamond cutters. Each one is going to take one of the “roughs” and cut and polish it into a sparkling, dazzling—and now, expensive—round shaped gem that will be someday mounted in a gold ring. (See step by step diamond cutting.)

A Diamond Cutter’s Skills

Depending on the skill of the cutter, each diamond will look a little different. One may stand out above the others. Its dimensions are slightly different. It has a fire and brilliance the others lack. It just looks better than the other four!

The reason could be because of the cut and the way the light entering the diamond gets refracted. Refraction is basically; light entering a gem moving around inside depending on the crystalline structure, before zipping back out. 

Reflection is light bouncing off the surface; refraction is light shining back out from down inside the gemstone.

If our diamond cutter is good, lots of light gets refracted back, making the diamond look especially sparkly.

If he’s not so good, the diamond won’t have as much sparkle and fire as a well cut one would. If the cutter is new or just off his or her game, the diamond could just sit there like a piece of glass without much pizzazz.

Let’s Focus on the Round Cut Diamond

The most common diamond shape is round. The reason for this is that round cut diamonds are perfectly proportioned to take advantage of the natural octahedral  crystal that comes out of the ground and maximizes as much of the rough diamond crystal as possible.

The different cut names have to do with the number of facets (the shiny, flat planes on the surface of a stone) and the proportions (the percentages of each part of a cut stone compared with the others). You’ll hear of diamond cut names like “old European cut,” “round brilliant,” “ideal cut,” “hearts and arrows,” and many others.

Words to Know in Discussing Diamonds and Reading a Diamond Grading Report (Certificate)

The flat, center top of a diamond is called the table.
The top half (actually less than half) of the diamond is called the crown and bottom half is called the pavilion. The widest point of the diamond separating the crown from the pavilion is called the girdle.
The point at the very bottom of a diamond is called the culet.

The Two Most Important Diamond Proportions and Why

The two proportions that contribute most to the fire and brilliance of a diamond are:

a) the depth of the stone (length from table to culet) as a percentage of the width, and:

b) the width of the table as a percentage of the width of the entire stone. This measurement is taken at the girdle.

These percentages are listed on all diamond grading reports. A rough guide follows.

What Depth Percentages on a Diamond Grading Report Mean:

Ideal                58-60%

Excellent         60-62%

Good               62-64%

Fair                  64-66%

Poor                 Greater than 66%

How to Read Table percentages on a Diamond Grading Report:

Ideal                53-58%

Excellent         to 60%

Good               to 64%

Fair                  64-70%

Poor                 Greater than 70%

What’s the Difference  Between Round Brilliant Cut and Ideal Cut?

Most round diamonds today are “round brilliant” cut. They have 58 facets. Many older and smaller carat diamonds have fewer facets and don’t sparkle as much as round brilliants cuts.

“Ideal cuts” are essentially round brilliant diamonds that have been cut with well researched proportions, which are thought to be “ideal” and to refract light “ideally!”

You can’t go wrong with an ideal cut diamond. But if that is out of your price range, know that close is often good enough in horseshoes, hand grenades and diamond cutting. So look at the ideal proportions here and use them as a guide to look towards and know about, as opposed to slavishly insisting upon.

How Diamond Cut Effects Diamond Pricing

Two diamonds with the same color and clarity can weigh exactly the same, but be different  in price. Before you shout, “shenanigans,” you may notice that one stands out more than the other. It exhibits more fire and brilliance than the other.

Why is that? You guessed it. The more expensive one has been cut better than its less expensive pal.

Now You’re Ready to Stand up and Look at Diamonds Fearlessly

Now that you’ve read up on how important cut is to a diamond and how to read a diamond grading report I want to share my personal opinion.

It’s important to really look at the diamond and not “buy the cert,” which basically means read about all the perfect proportions and assume the diamond is what you want.

Look at the diamond, if you’re not impressed, don’t let the cert sway you. The diamond’s look is more important than the proportions and all the specifics. If you’re looking at a diamond with no certificate, which many under a carat stones are, and it’s a sparkly little beast, show it some love.

Look at it compared to other diamonds, especially one that you know is a good one. If that little diamond is refracting light like crazy, of good color and is the size you want, it’s probably cut well. Get it!

This Wedding Set Was Made with Attention to Great Diamond Cut. It Sparkles Even When Dirty

May you find the diamond of your or your fiancee’s dreams!

Calla Gold
Diamond Seller and Diamond Educator Also see my posts on:
Diamond Carat Weight
Diamond Color
Diamond Clarity