Popular since the 1980s, radiant is the first angular shape that has a complete brilliant cut facet pattern. It is also one of the most faceted and brilliant diamond cuts available on the market. If you are interested in buying a diamond with a vibrant look and brilliance, this radiant cut diamond guide is a must-read.
History of Radiant Cut Diamonds
The original radiant cut was invented by a master diamond cutter Henry Grossbard in 1977.
Grossbard knew that many people loved the elegant elongated shape of the emerald cut but felt that it did not sparkle enough. His goal was to combine the best features of the emerald cut and the round brilliant into one diamond cut that would unleash the full potential of a diamond’s brilliance.
After years of careful experimentation, Grossbard perfected the original radiant cut in 1981. It was a revolution in the diamond industry; the elegant emerald shape was transformed into a new cut with unparalleled sparkle. Although it did not exceed the round brilliant cut’s brilliance, it is still more brilliant than any other angular cut.
Radiant cut diamonds come in both rectangular and square shapes with distinctive cropped corners. Featuring 70 facets, the radiant cut is the first angular cut, the second being the princess cut, which has a complete brilliant cut facet pattern both on the crown and pavilion. It is also worth mentioning that grading reports describe the shape and the cutting style of the radiant cut as cut-cornered rectangular modified brilliant or cut-cornered square modified brilliant.
Even though the radiant cut has only been in the diamond industry for less than 50 years, it managed to gain extreme popularity in a short amount of time.
Radiant Cut Diamond Cut Quality
Diamond cut quality is the main factor when determining a stone’s appearance and level of fire, brilliance and scintillation.
While the Gemological Institute of America (GIA) and other lab entities provide cut grading for the round brilliant cut, they do not give a cut quality grade for fancy shaped diamonds, including the radiant cut. This is because fancy shapes have many non-standardised facet structures, meaning they can be cut to a wide range of proportions. However, grading laboratories list information on polish and symmetry which are some of the key features to choosing a brilliant and sparkly stone.
When choosing a radiant cut diamond, make sure to pay attention to the corners of the stone. They should be even, not too wide and not too narrow. The culet should be centred and all sides parallel to each other. Symmetry is the key to maintaining the overall beauty of the stone. Also, look for a stone that has no bowtie effect. It occurs when a stone has misaligned facets causing some light to leak at the centre and not bounce back to the table.
Since there is no industry-wide consent on what cut parameters make an ideal radiant cut diamond, it is recommended to use the table below as a general guideline for evaluating the cut quality of radiant cut diamonds.
| EXCELLENT | VERY GOOD | GOOD | FAIR | POOR | |
|---|---|---|---|---|---|
| TABLE % | 61 - 69 | 57 - 60 or 70 - 72 | 54 - 56 or 73 - 74 | 51 - 53 or 75 - 79 | < 51 or > 79 |
| DEPTH % | 61 - 67 | 59 - 60.9 or 67.1 - 70 | 57 - 58.9 or 70.1 - 74 | 54 - 56.9 or 74.1 - 79 | < 54 or > 79 |
| GIRDLE | Very Thin to Slightly Thick | Very Thin to Slightly Thick | Very Thin to Thick | Very Thin to Very Thick | Extremely Thin to Extremely Thick |
| CULET | None | Very Small | Small | Medium | > Medium |
Radiant Cut Diamond Colour
The colour of radiant cut diamonds is graded on a scale from D to Z, where D signifies a completely colourless stone and Z means an easily noticeable yellow or brown tint.
As a general rule, smaller radiant cut diamonds weighing 0.50 carats and less hide colour better than larger ones, but the differences in colour in radiant diamonds are easier to spot than in other diamond shapes. For this reason, it is recommended to opt for an H colour or better to have a diamond that will appear white and colourless to the naked eye. However, keep in mind that colour should be compared on a case-by-case basis.
The chart below provides a general guideline for evaluating colour in the radiant cut diamonds.
| SIZE | EXCELLENT | VERY GOOD | GOOD | FAIR | POOR |
|---|---|---|---|---|---|
| < .50 ct | D - G | H - I | J - K | L - M | > M |
| .51 - 1.0 ct | D - F | G | H - I | J - K | > K |
| 1.0 - 2.0 ct | D - F | D - F | G - H | I - J | > J |
| > 2.0 ct | D - F | D - F | G | H - I | > I |
Radiant Cut Diamond Clarity
The GIA grades the clarity of radiant cut diamonds on a scale from FL to I3, where FL means a flawless stone and I3 indicates a heavily included diamond.
Due to their facet arrangement and excellent light performance, radiant cut diamonds hide inclusions and blemishes fairly well, especially in comparison to step cut diamonds. Moreover, smaller radiant cut diamonds hide imperfections better than larger ones do, which is why if you are going to purchase a smaller stone, you may opt for a lower clarity grade such as SI1 and SI2 while keeping an eye-clean appearance.
The chart below provides a general guideline for evaluating clarity in radiant cut diamonds.
| SIZE | EXCELLENT | VERY GOOD | GOOD | FAIR | POOR |
|---|---|---|---|---|---|
| < .50 ct | FL - VS2 | SI1 - SI2 | I1 | I2 | > I2 |
| .51 - 1.0 ct | FL - VS1 | VS2 - SI1 | SI2 | I1 - I2 | > SI2 |
| 1.0 - 2.0 ct | FL - VVS2 | VS1 - VS2 | SI1 - SI2 | I1 | > I1 |
| > 2.0 ct | FL - VVS2 | VS1 - VS2 | SI1 | SI2 | > SI2 |
Radiant Cut Diamond Length to Width Ratio
The length to width ratio expresses how relatively long or wide a diamond appears. It is calculated by dividing the length of the diamond by its width. For example, if the length of a radiant cut diamond is 7mm and the width is 5mm, its length to width ratio is 1.4.
Each fancy diamond shape has a certain length to width ratio that is considered most appealing for that shape. Radiant cut diamonds come in various ratios, from perfectly square (any ratio of 1.05 or less will appear square to the naked eye) to the more traditional rectangle. However, the optimal ratio for radiant cut diamonds is between 1.00 – 1.35, with rectangular shapes going up to 2.00.
The table below serves as a guideline for evaluating the ratio of radiant cut diamonds.
| EXCELLENT | VERY GOOD | GOOD | FAIR | POOR | |
|---|---|---|---|---|---|
| SQUARE | 1.00 - 1.03 | 1.00 - 1.03 | 1.04 - 1.05 | 1.06 - 1.08 | > 1.08 |
| RECTANGLE | 1.20 - 1.30 | 1.15 - 1.19 or 1.31 - 1.35 | 1.10 - 1.14 or 1.36 - 1.40 | 1.08 - 1.09 or 1.41 - 1.50 | < 1.08 or > 1.50 |
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