Radiant Cut Diamond Guide

It puts “crushed ice” into the “fire and ice” of a diamond’s sparkle.


As seen from above, the radiant cut has a distinctive faceted brilliance that comes from the interplay of step-cut facets and brilliant facets. It combines the timeless appeal of the brilliant-cut diamond with the allure of the intriguing emerald cut. With its scintillating and celebratory appearance, this is a great diamond to choose for a diamond engagement ring.


Diamond Cut

Branded as the Original Radiant Cut, and invented by master diamond cutter Harry Grossbard in 1977, the radiant diamond is a relatively new brilliant-cut diamond.

Referred to as a “cut-cornered rectangular modified brilliant” or a “cut-cornered square modified brilliant” on its GIA certificate, the radiant diamond has a combination of step-cut and brilliant facets on its crown with modified-brilliant facets on its pavilion (the section below the girdle of the diamond).

Bevelled or “cut” corners mean that the stone is resilient in any setting and that when seen from above, it has eight sides.

A good-quality radiant diamond usually has a sizable table, creating a magnificent vista into the glitzy kaleidoscope of its interior.



Radiant diamonds offer great radiance for your Rands (or for any currency), as they tend to be surprisingly less expensive than other diamonds, such as the ordinary brilliant-cut or even the emerald-cut diamond. A good cut tends to conceal any inclusions that would be more visible, as like an emerald diamond, inclusions are more naturally identifiable. If you are looking to purchase a radiant-cut diamond, you may want to consider the highest clarity possible or least select nothing below a “very good” cut.

These factors, together with a uniquely colourful and scintillating appearance, give radiant diamonds a competitive edge and have made them an extremely popular choice for engagement rings. Because of its rectangular shape, the radiant diamond is reminiscent of the emerald-cut diamond and the princess- cut diamond, differing due to its unique features of sharp, bevelled corners and unusual step-cut facets.

  • The crown of a radiant-cut diamond typically has 25 facets.
  • The pavilion or lower portion of a radiant diamond usually has 28 facets.
  • If there is a culet (a base facet),  the stone will have 29 facets in the pavilion.

The facets of the stone create a beautiful and mesmerizing kaleidoscope effect, in both the crown and pavilion. When considering a radiant-cut diamond for an engagement ring, examine the GIA certificate and also the appearance of the diamond.


Symmetry & Certification

Symmetry will be graded on the GIA certificate, but you should also check this carefully when viewing the stone. Observe the diamond from above, as the left and right sides and top and bottom sides of the stone must be symmetrical.

Each of the two sets of bevelled corners facing each other diagonally should also be identical to one another. Check that the edges are the same size and neither too large nor too small. Imagine a line dissecting the stone in half vertically, and another line cutting the stone in half horizontally.

The table of the stone should be centered where these lines meet.

Turn the diamond over, and once again imagine horizontal and vertical lines cutting through the centre of the stone, dissecting it into four equal quadrants. The culet or base facet should be centred where the horizontal and vertical lines meet.

If you are unsure about any aspect of the lines and symmetry of a radiant diamond, consult an expert diamond dealer at Cape Diamonds.


Diamond Table & Depth Percentage

The “table” of a diamond is the large, flat area on the top of the stone.

The size of the table in relation to the rest of the radiant diamond is essential because it’s where the majority of light enters the stone. This needs to be carefully balanced with the rest of the stone’s proportions to ensure that the correct amount of light enters in, allowing for maximum sparkle.

Contrary to what you might think, a larger table is not always better. If the diamond’s table facet is too wide, the upper facets on the crown will not have room to disperse light.  If the table of the stone is too small, there won’t be much light going into the stone, which will diminish its overall brilliance.


The depth percentage is the ratio of the depth to the width of the stone.

This is an important factor because if the stone is too tall, light will leak out the bottom of the stone, and if it’s too shallow light will be reflected back at the incorrect angle.

In both cases, less light is returned to your eyes, reducing the degree to which the stone appears to sparkle.

Varying from these percentages (between 59% and 70%, with an optimum of 61% – 67%) is likely to mean that a higher proportion of light is lost through the sides and the bottom of the diamond, giving the diamond a less brilliant appearance.



Colour Grading

The radiant-cut diamond tends to radiate colour in higher intensity or unpredictable ways. For example, sometimes an ordinary brilliant diamond with a reduced colour grading can even be recut into a radiant diamond and reclassified as a “fancy yellow”. Ensure that your stone has a good colour grading, and if you would like a radiant white diamond, choose a grade that is as close to colourless as possible  – definitely avoid any colours below the “I” diamond range.

The resilient shape of the radiant cut diamond makes it amenable to an imaginative range of settings. Larger stones look stunning as solitaires, and a halo of smaller diamonds around a central radiant diamond can add to the sparkle and apparent size. A radiant diamond also looks beautiful with side stones or set into a three-stone trilogy engagement ring. The radiant diamond can be set on a simple, single band, or placed into a split shank band.



Bow-Tie Effect

With its trimmed corners, the stone is much less likely to get snagged in clothing or hair than the square-cornered princess cut. The lack of exposed edges also means that there are fewer exposed areas that can strike hard surfaces, meaning that the stone is less likely to get chipped or even cracked.

Like other fancy shapes, radiant diamonds can exhibit a dramatic visual problem, the bow-tie effect. Elongated rectangular radiant cut diamonds are particularly prone to this defect, which is caused by the stone being improperly cut and proportioned so that close-up objects darken the stone across its circumference in shape, resembling a bowtie. If you are purchasing a radiant diamond elsewhere, always ensure that your diamond is free of a noticeable bow-tie.


Most importantly, a radiant diamond engagement ring can be designed in advance to perfectly match a wedding band that will, in all likelihood, be the next item of jewellery on your shopping list!