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Diamond Cuts 101: What You Should Know Before You Buy

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When it comes to buying a diamond, the cut is the most important of the 4 Cs. Diamond cuts is a complex topic, but buying a beautifully cut diamond isn’t complicated. This “Diamond Cuts 101” guide explains what you need to know about cuts before you make a diamond purchase. 

Why Are Diamonds Cut?

1.04-Carat Emerald Cut Diamond Blue Nile
A 1.04-carat emerald cut very good cut diamond from Blue Nile. Emerald cut diamonds are cut in steps, giving the diamond a mirror-like look.

Diamonds directly from the mine, or “rough diamonds”, look quite different than the brilliant, sparkly diamonds in engagement rings. Before they are cut and polished, diamonds have a dull, opaque appearance. Cutting a diamond removes its rough outer surface to reveal the clear beauty underneath. The process removes weight, decreasing a diamond’s carat size, so diamond cutters must find a balance between preserving the diamond and getting an excellent cut. 

Diamonds used to be cut by hand–a difficult process that demanded a high price for the best-cut diamonds. Diamonds are now cut by lasers, so precisely-cut diamonds with excellent symmetry and polish are available almost everywhere. This causes the price differences between the top-rated diamond cuts to be less significant than they once were.  

Diamond-Cut vs. Shape 

James Allen Diamonds
Asscher and cushion-cut diamonds are variations of the traditional square, princess-shaped diamond. From James Allen.

The terms cut and shape are often used interchangeably. There’s a difference when it comes to grading diamonds according to the 4 C’s. 

Shape is the diamond’s overall outline or figure: round, square, rectangular, oval. 

Cut describes how the diamond’s surface has been cut into many tiny facets. The orientation and size of the facets affect how the light will pass through the diamond. This influences how much the diamond will sparkle and how large it will appear. Diamond cut grades range from excellent to poor.

The standard diamond shapes can be cut into fancier shapes, like emerald, pear, cushion, heart, asscher, radiant and more. Most online diamond retailers let you search for diamonds by shape. 

Blue Nile Cuts
The most common diamond shapes. The fancy shapes are all variations of the standard round, square, oval, or rectangle shapes. From Blue Nile.

You’ll often see diamonds described as “emerald cut”, “cushion cut”, or “princess cut.” Remember that emerald and cushion refer to the diamond’s overall appearance and not the grade of the cut. A diamond’s full description will include more information about how the diamond was cut and the cut’s rating. 

Diamond-Cut Styles

0.952 F VS2 Signature Round Brian Gavin
A 0.95-carat round brilliant diamond. This diamond’s cut and symmetry are rated as ideal. From Brian Gavin Diamonds.

The most common modern diamond cutting styles are brilliant, step, and mixed. 

Brilliant Cut Diamond 

A diamond that has many triangular and kite-shaped facets spreading outwards from the center of the stone. Brilliant cut diamonds, like round, princess, and oval, are designed to maximize sparkle and shine. 

emerald custom made
Find this Ring at Custom MadeAn emerald cut diamond engagement ring. Emerald cut diamonds have crisp facets that look like a set of steps. From CustomMade.

Step Cut 

A diamond that is square or rectangular and consists of facets that are parallel to each other. The facets are cut on all four sides of the diamond, with a flat surface on top. These facets look like a set of steps descending into the diamond. Step cut diamonds have fewer facets to reflect light, so they aren’t as sparkly as brilliant-cut diamonds. Instead, they have a clean, sophisticated look, almost like a mirror. Emerald, asscher, and baguette diamonds are all step cut diamonds.

radiant cuts blue nile
A radiant cut diamond from Blue Nile. Radiant cut diamonds are elongated yet brilliant, maximizing sparkle and fire.

Mixed Cuts

A mixed cut diamond, or hybrid cut, is a combination of brilliant and step cuts. Radiant cut diamonds are one of the most popular mixed cut styles. These are typically elongated like an emerald cut diamond, with brilliant-cut facets to make them sparkle.  

Grading Diamond Cut 

Diamond cut is a measure of how well a diamond reflects light. Poorly cut diamonds won’t reflect as much light, giving the diamond less brilliance and fire. Some of the light will reflect out of the bottom of the stone, which is unseen when a diamond is set in a ring. Poorly cut diamonds may have light or dark patches that make the diamond look dull and lackluster. So, what do you need to consider about cuts when buying a diamond online? 

Excellent or Ideal good cut diamonds James Allen
Excellent or Ideal cut diamonds will reflect almost all of the light that goes into the diamond. These diamonds are sparkly and brilliant. Diamonds with a worse cut, such as good, won’t reflect much light out of the top, diminishing their appearance. From James Allen.

Cut grade varies according to the gemological laboratory. The Gemological Institute of America grades cut as excellent, very good, good, fair, and poor. Almost all of the light that enters an excellent cut diamond is reflected, giving them the most fire, brilliance, and sparkle. Diamonds with a very good cut are just a step below the excellent cut and have a similarly beautiful appearance. A diamond with either excellent or very good cut is a great choice for an engagement ring center stone. 

The American Gem Society (AGS) laboratory rates diamonds as ideal, excellent, very good, good, fair, and poor. The ratings are similar, with ideal and excellent as the top-tier diamond cuts. 

When buying a diamond online, look at the diamond’s information to see which lab created the report. Retailers like Blue Nile and James Allen sell GIA-certified diamonds, while many of the diamonds sold by Brian Gavin and White Flash are certified by AGS. Some retailers have their own ratings too, so make sure to read all the information about a diamond before you buy. 

Cut, Polish, and Symmetry

1.024 F SI1 Signature Cushion Brian Gavin
A stunning 1.024-carat cushion cut diamond with ideal cut, polish, and symmetry. From Brian Gavin.

Polish and symmetry are two other factors that affect a diamond’s cut. 

After a diamond is cut, the facets are polished to give the diamond a smooth, glass-like appearance. 

Polish is rated according to how smooth the surface is, from excellent to poor. The specific grades are excellent, very good, good, fair, and poor. The better a diamond’s polish, the better each facet will reflect light. 

Symmetry is how well-aligned a diamond’s facets are. If a diamond’s facets aren’t aligned symmetrically, the light entering the diamond will be misdirected. This will diminish the diamond’s sparkle and even give it a dull appearance. Symmetry is also rated from excellent to poor. An off-center table, misaligned facets, and extra or missing facets can all decrease a diamond’s symmetry grade. 

Triple Excellent, or Triple X, diamonds are those with excellent cut, polish, and symmetry. With advances in diamond cutting technology, it’s easy for diamond cutters to make Triple X diamonds. Consumer demand for Triple X diamonds is high and so is the availability. Many jewelers consider Triple X diamonds to be the standard for diamond engagement rings. It’s still important to check the diamond’s certificate–be very cautious about buying a diamond with anything other than a “very good” or “excellent” symmetry and polish rating. 

Evaluating Diamond Cut Online 

0.80 carat oval diamond excellent cut with clarity
A 0.80-carat oval diamond with excellent cut and polish and very good symmetry. The cut on an oval diamond is in the round brilliant style. From With Clarity.

The most important thing to do when evaluating a diamond’s cut online is to read all of the information provided by the retailer. Each retailer describes cut in a slightly different way, and some don’t provide cut grades for fancy cut diamonds. Fortunately, online retailers do a good job of explaining the cut grades. You can search for diamonds by cut and get a definition of each grade. 

Retailers also have curated collections of the highest-quality cut diamonds. Blue Nile has a collection of princess, round, and cushion diamonds called Astor Ideal. James Allen has a similar collection called True Hearts, and Brian Gavin has a Hearts and Arrows collection of round and cushion diamonds. These branded diamonds are beautiful and highly ranked, but you don’t have to shop in this category to find a quality diamond. 

In Conclusion

When searching for diamonds, remember that many websites use the term “ideal” instead of “excellent”. The majority of diamonds on the market today have ideal/excellent or very good cuts, so look for those stones. Watch the videos and look at the pictures of each diamond so you can see how it interacts with light. Check the rating for symmetry and polish, as they have a big impact on a diamond’s sparkle. The cut might be the most important of the 4 Cs, but it is easy to find the best diamond now that you know what to look for.