A Guide to Radiant Cut Diamonds

The radiant cut diamond is a relatively new entry into the world of diamond shapes. It was developed in the late 1970’s and became an instant success. Many diamond shapes and facet arrangements have come onto the scene with great fanfare only to quickly disappear as a temporary fad. But the radiant cut made a solid place for itself by combining the linear outline of the emerald cut with a facet arrangement that delivers more sparkle and a distinctive overall visual appeal.

In this article we will discuss the most important factors that every shopper should understand in order to make a great buy on a high performing and beautiful radiant cut diamond. We will also provide guidance on creating the finished product, with beautiful images of radiant cut diamond rings.

*While this article is primarily based on natural, Earth- mined radiant diamonds, most of the info below also applies to radiant lab grown diamonds, with some of the differences discussed. 

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The radiant cut can be generally thought of as a hybrid shape- a cross between an emerald cut and a round brilliant. It shares an identical shape outline with the emerald cut featuring a square or rectangular overall shape, with corners that are clipped straight so that the outline is a straight lined octagon.

But whereas the emerald cut features a facet arrangement of horizontal ‘step’ facets, the radiant has a mixture of horizontal and vertical facets that give it a completely different visual appearance.

The Radiant was originally a patented cut, but the patent has since expired and the term radiant is used generically for this diamond cut. GIA lab reports describe a radiant cut as a “cut cornered rectangular (or square) modified brilliant”.

The overall outline of radiant cuts, like emerald cuts, can vary from square to very elongated. The length to width ratio will significantly impact the visual appearance of the diamond. To a large degree this aspect is in the realm of personal choice, however a radiant that is too elongated can suffer performance problems such as a “bow tie” effect.

The length to width ratio is a measure of how close to square the diamond is. Dividing length by width, a perfectly square diamond has a ratio of 1.00. The extent to which the ratio is greater than 1 indicates the extent to which it is elongated. Most rectangular radiants are in the balanced range 1.20 to 1.40 L/W range.

A more elongated shape tends to look bigger and is more graceful on the hand. A more square shape may work better for certain types of setting designs. As long as light performance does not suffer, length to width ratio is largely a personal taste factor.

Corners should be clipped to a balanced size, not so large that they begin to appear of similar size to the sides, and not so small that the angularity they bring to the shape will be lost to the prongs that cover them.

A radiant cut diamond tends to accentuate body color. The longer ray paths passing through the diamond by virtue of the facet arrangement tend to trap more of the body color of the diamond. It is for this reason that a great number of fancy color diamonds are cut into radiants. Therefore it is advisable to target a slightly higher color range than you otherwise might if shopping for a round brilliant. Well cut round brilliant diamonds, such as ideal cuts, tend to directly return a high volume of ambient light to the eye concealing some body color and looking whiter than their color grade. Radiants and some other fancy cuts tend to do the opposite.

To find a radiant cut that looks white, it is best to stay in the upper near colorless range of G-H. Colors in the I-J or lower range will begin to show a bit of yellow.

One of the value factors that radiant cut diamonds offer over emerald cuts is that they tend to conceal inclusions better. Emerald cut diamonds reveal clarity features more readily than any other cut. The small, fast scintillation patterns of radiant cuts tend to make small inclusions much more difficult to see. It is therefore possible to find lower clarity radiant cuts at significant savings that are eye clean and pretty.

There are many nice radiant cut diamonds available in the Si range. Just be careful that the inclusions are not negatively impacting transparency, as can sometimes happen. The resulting loss of brilliance can happen even in a top quality cut. This can be a subtle effect that requires a trained eye to diagnose, so working with an experienced vendor of high integrity is your best assurance of finding a truly great radiant cut.

As with any diamond, the light performance produced by the cut is the essence of what creates its special beauty – brilliance, fire and sparkle. The challenging thing about radiant cuts for the non-expert is assessing light performance. A GIA report will tell you many things about a radiant, but it will not tell you much of anything about light performance. While there are proportion measurements and even polish and symmetry grades, these do not directly reveal how the diamond handles light. It is necessary then to rely on other diagnostics to make those assessments.

Diamond images and videos are helpful, and advanced imaging such as ASET add even more information. ASET is a light map that provides details on brightness, light leakage and contrast – the essential components of light performance. But interpreting ASET signatures on fancy shape diamonds requires experience. It is not as straight forward for radiants as it is for round brilliants. It is therefore advisable to deal with a vendor who can provide in-depth analysis and provide you with the diagnostics necessary to understand these all-important aspects.

An ASET light map shows light return from high and low angles, areas of light leakage, and areas of contrast. Below are several examples of nice radiants and the different ASET signatures that you may see in shopping for a radiant with an expert who can provide this information.

Because the radiant cut features mixed faceting some areas of the diamond will return direct flash while others tend to return a more subtle twinkle effect often likened to ‘crushed ice’. To many shoppers, the crushed ice look is very appealing. Many cushion cuts also produce this flavor of light performance.

The physical facets of a crushed ice cut create many secondary reflections which bounce around internally resulting in a great number of small ‘virtual’ facets. In some cases they are small but distinct, with enough contrast to create a mesmerizing twinkling effect. But in other cases these reflections can get somewhat ‘mushy’, less distinct, and less attractive.

The crushed ice effect is most apparent in the center of a radiant cut, under the table. Some observers describe it as looking into a well, or a hall of mirrors. The eye descends into a seemingly endless bottom towards the culet.

With experience it is possible to decode an ASET map and predict whether the light performance will likely be bright and appealing or dim and lackluster. With a trained eye, these things can be assessed by looking at the diamond in multiple lighting environments.

For example, the ASET map below belongs to the beautiful crushed ice radiant above. Notice that the components of light performance are broken up and evenly spread throughout the diamond. Even though there is a fair amount of leakage, the diamond has great eye appeal. This is due to the curious fact that leakage, if small and evenly distributed, can actually contribute to dynamic contrast and be additive to performance.

Most certified radiant cut diamonds on the market today have lab reports from the GIA. The report provides the essential identification and grading of the diamond including carat weight, dimensions, color, clarity, fluorescence, polish and symmetry grades, and basic proportions. It may also provide additional comments that can be important. A GIA report does not, however, provide an overall cut grade. This important piece of information you will need to get through consultation with an expert, by reviewing advanced light performance images, studying HD video, viewing in person, or all of the above.

Although the radiant cut has a mixed cut that is capable of producing good brightness, the optics of the round brilliant cut are very distinctive. Even if the radiant is very square, it will retain its distinctive look and rarely be mistaken for a round. However, certain setting styles can make the distinctions less apparent. But to a certain extent that defeats the purpose of choosing a unique shape like the radiant.

There is no other diamond cut capable of optimizing brightness, fire, and scintillation to the degree that a well cut round brilliant can. Because of the inherent symmetry of the design and the fact that it produces a combination of large and small virtual facets, a precision cut round brilliant will outperform virtually all other diamond shapes.

However, like shopping for a car, horsepower may not be the priority for every buyer. The angular shape and more subdued twinkle of a radiant may be more appealing to some shoppers.

The most comparable shape to the radiant cut, and the one most shoppers looking for radiants also consider, is the princess cut. But beyond the fact that both have rectilinear outlines, the visual appearance differs significantly.

First, the Princess cut does not have clipped corners. The corners come to a point and are often set into V-tip prongs. A radiant with very small clipped corners can look like a princess from an outline perspective, but the flavor of the optics is very different.

The brilliant style faceting of the princess cut gives it a different type of light performance. The mixed cut of the radiant tends to produce a crushed ice pattern of very small random reflections and a twinkling effect, whereas the princess cut tends to have regular reflections that are a bit more flashy. Princess cuts with more chevron facets can start to look very much like radiants, especially if the l/W ratio tends more toward rectangle than square. A very square radiant can look very much like a princess, especially if it has very small corners.

Shoppers interested in radiant cuts should also consider a princess, particularly when looking for light performance approaching that of a round brilliant. Lab certified Ideal cut princess cuts are available with light performance reports from the American Gem Society Laboratories (AGSL), which makes finding a top performer much easier. No such certification is available for radiant cuts. The Whiteflash A CUT ABOVE® Princess is a true super ideal, with qualifications that go above and beyond even the AGSL lab report.

As mentioned earlier, GIA does not currently grade cut quality on radiant cuts or any other fancy shapes. Therefore, the information on a GIA report pertaining to all-important cut quality and light performance is woefully lacking. The dimensions are listed, so it is possible to calculate length to width ratio and get a sense of the shape, and cut aspects of polish and symmetry are listed, which has some bearing on the care taken by the cutter in the finishing process. Also listed are depth and table percentages. Typically both measurements will be in the mid to upper 60 percent range. If either strays down into the 50’s or up into the 70’s, the diamond deserves extra scrutiny. Crown height is not listed on a GIA report, nor are any other measurements that might be helpful in assessing cut quality.

The paucity of information on the lab report makes additional diagnostics even more important. Advanced imaging such as ASET is very informative, even if you are buying in person. When buying online a 3D video is a must.

In some cases the elongated shape of a radiant cut may appear larger than a round of comparable carat weight. However, this may be more of an optical illusion. And if a radiant, or any other shape, is cut too deep, it will be hiding carat weight and not look as big as one of the same weight that is well cut. And even if a radiant is proportioned to have good ‘spread’ (surface area), if it suffers any light performance deficits, especially around the perimeter, it will appear to be smaller than one that has better brightness. Ideal cut rounds are known to appear larger than rounds of average cut quality of the same diameter because they return more light to the eye from edge to edge.

Cutters of natural diamonds often use different rough to cut fancy shapes, rather than the more common octahedral rough used to cut rounds and princess cuts. They also will use creativity to extract the most profitable finished diamond out of that rough, without necessarily prioritizing light performance. Liberties are often taken that result in some deficit in one aspect or another. So, the answer to the question as to whether a radiant cut looks bigger is ‘”it depends”! This is another reason it is wise to shop with a vendor who has expertise in cut quality and light performance. This is the best assurance that you find a radiant that checks all the boxes.

A radiant cut will theoretically be less expensive than a comparable size and quality round brilliant. All ‘fancy shape’ diamonds are priced according to trade guidelines that are lower than the prices for rounds. So it is possible to save some money when buying a radiant cut compared to a round. However, there are many variables that go into the pricing of fancy cut diamonds. A radiant that is priced relatively low may have issues that are not readily apparent to the average diamond shopper.

Because the GIA does not grade cut quality on fancy shapes, cutters are not penalized by making compromises to light performance or spread. A radiant that is priced low may be hiding weight or leaking too much light, or both. Because these market considerations do not apply to lab grown rough, it is reasonable to expect radiant cut lab diamonds to have been cut without compromises to light performance in order to maximize carat weight. 

The best advice is to first shop around and compare prices, which is easy to do online. Then identify a vendor who is qualified to provide you the expert advice needed for a successful purchase. Choosing a trustworthy vendor who is able to provide advanced diagnostics and solid advice is your best assurance of getting a fair price on a great diamond.

Lab grown diamonds have emerged in the last few years as an affordable option and many diamond shoppers are taking full advantage. The substantially lower prices of lab diamonds enables shoppers to extend the reach of their available budgets to increase diamond size and/or quality and to incorporate finer designer brand settings into their purchase. It also enables shoppers to experiment with different shapes and faceting styles and has made radiant lab grown diamonds an increasingly popular choice.

Because lab diamonds have essentially the same chemical, physical and optical properties as natural diamonds, they are equally brilliant and fiery if cut with precision. As mentioned above, the low cost and availability of rough lab diamonds makes it unnecessary for the cutter to be overly concerned with carat yield, and can focus on making the most beautiful diamond possible.

There are some unique issues with lab diamonds that need to be understood, some of which cannot be gleaned from a gemological report. It is therefore important to have any significant diamond purchase evaluated carefully by an expert. That said, because their prices are so much lower than natural diamonds, there is less at stake. But in the final analysis you want the best performing diamond you can get for whatever your budget is.

Radiant cut diamonds are pretty versatile in terms of compatible setting choices. Settings for emerald cuts, princess cuts and even rounds are readily adaptable to radiants. Like other angular shapes radiants look great in modern architectural designs and some vintage designs such as art deco styling.

There are three main options for putting together a radiant cut ring; select a style with an interchangeable head, find a radiant or emerald style in a designer brand catalogue and order that setting for the specific dimensions of your diamond, or create a custom made ring for your specific size radiant.

Many ring styles are constructed in a way that the head that actually holds the diamond is a separate piece and can be interchanged depending on the shape and size of the diamond to be held. Many solitaire styles are constructed this way. You can usually tell if a style does not have an interchangeable head as the setting for the diamond is built-in and fully integrated into the overall design. There are a wide variety of styles available with interchangeable heads that can accommodate a radiant cut.

Although most designer brands have styles in their catalogues that are suitable for radiants, you may not find them in stock with any given retailer. You can browse the catalogues of the various designers for options, and any authorized retailer of that designer can order that design for the radiant cut ring you choose. You can always inquire with a friendly and knowledgeable Whiteflash jewelry and diamond consultant for assistance finding designer setting options.

Many customers choosing fancy diamonds are also interested in having a custom design made that will capture a totally unique and personal design aesthetic. This is sometimes a more expensive option and may not be ideal for every customer as the outcome is sometimes not entirely predictable. Whiteflash has full manufacturing capabilities and a step by step process that eliminates almost all uncertainties. Feel free to contact us for advice on your goals. Our experienced diamond and jewelry consultants will help you determine the best approach for your project.

Below are samples of radiant cut rings that Whiteflash has provided for customers ranging from simple solitaire style adapting our own sleek line pave engagement ring for the radiant, to designer brand styles, to full Whiteflash custom creations.

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Whiteflash is a leader in the field of light performance analysis, with decades of experience assessing all diamond shapes and facet arrangements. Our A CUT ABOVE® brand of natural super ideal round and princess cut diamonds are considered by experts to be among the finest precision cut diamonds available anywhere.

We are authorized distributors for the finest bridal brands in the market including Tacori, Verragio, Simon G, A. Jaffe and others. We have maintained an unbroken string of A+ ratings with the Better Business Bureau since 2004 and have been awarded the BBB Pinnacle Award for 2021, 2020, 2018, 2015, and 2012. We operate a manufacturing operation to service everything we sell and to create custom jewelry from scratch.

Whiteflash is one of very few retail jewelers certified for ISO 9000 Quality Management and has earned an international reputation for excellence. And we would love to earn your business!