Radiant Cut Ruby: Pros, Cons & Fire

Take an emerald cut's outline, corners cropped, and fill it with brilliant facets: that is the radiant. Ours has 74 facets at a length-to-width ratio of 1.284 and 53.8% depth; it is on sale as a 3D model.

In ruby it is a stone of extremes. It has the third-highest fire and the third-largest face per carat of any cut we measure in ruby, and it leaks more light than any of them.

The diamond radiant is dim too, 32 for brilliance, and the ruby returns less still, 26.

Radiant cut ruby: good choice or not? Pros and cons

Cons

The second-dimmest cut we measure in ruby 26 vs 94
Most of the light leaks 67 vs 5
Heavier than a diamond radiant 1.78 vs 1.56 ct
Slightly fewer flashes than a round 74 vs 80

Compared with the T73 Round Brilliant in ruby and with the Radiant Cut in diamond. A difference counts from 3 points (Brilliance, Fire, Tilt, Leakage), 5 (Scintillation, Symmetry), 4% (face-up size per carat) or 5% (weight); Tilt counts as a pro only for a stone within 5 points of the brilliance it is compared with. How we measure.

All eight scores against the T73

At a glance: the Radiant Cut in ruby (white) against the T73 Round Brilliant in ruby (dashed): solid white where it reaches further, hatched where it falls short. Each pro and con is explained, with pictures, below.

Against the T73 Round Brilliant in ruby: ahead on 3, behind on 5.

Global59, the comparison 79, difference −20
Brilliance26, the comparison 94, difference −68
Fire69, the comparison 37, difference +32
Scintillation74, the comparison 80, difference −6
Spread105, the comparison 100, difference +5
Symmetry99, the comparison 100, difference −1
Shape-norm31, the comparison 102, difference −71
Tilt100, the comparison 75, difference +25

Face-up light census, a different measure from the Cut Grading Tool; Spread and Shape-norm above 100 sit on the ring. Spread is the census's estimate from depth alone; the face-up size in the pros and cons is measured from each model's outline.

Open it in the Cut Performance Wheel

What ruby gains in a radiant cut

Far more fire than a round ruby

Fire 69 against 37 for the T73 Round Brilliant in ruby: 32 points higher

Only the oval and DG-Elongated Hexagon score more in ruby. That fire sits on a face returning 26 for brilliance, so expect colour in a dim stone rather than in a lively one.

Radiant cut in ruby face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 69) — Look at the coloured flashes: those are fire. Same light, same size, same face-up angle; rendered by our 3D Gemstone Simulator from each cut's own model.

T73 round brilliant in ruby face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 37) — Look at the coloured flashes: those are fire. Same light, same size, same face-up angle; rendered by our 3D Gemstone Simulator from each cut's own model.

Try it yourself: See the fire in the 3D Gemstone Simulator

A larger face for its weight

Face-up size 118 against 100 for the T73 Round Brilliant in ruby (T73 = 100): 18% more face-up area for the same weight

Measured from the outline, the radiant covers more area per carat than all but two ruby cuts, the marquise and the rectangle. At 53.8% it is shallower than the T73, which keeps more of the weight in the face.

Radiant Cut · 6.63 x 3.61 mm at 1.00 ct · Face-up size 118

T73 Round Brilliant · 6.21 mm at 1.00 ct · Face-up size 100

Both stones weigh 1.00 ct in ruby and are drawn to the same scale in millimetres, from each cut's own model. Face-up size is the outline's area per carat, with the T73 at 100: a deeper stone, or a rounder outline, spreads less area for its weight.

Try it yourself: See its size at 1.00 ct in ruby in the 3D Gemstone Simulator

The catch with a radiant ruby

The second-dimmest cut we measure in ruby

Brilliance 26 against 94 for the T73 Round Brilliant in ruby: 68 points lower

Only DG-Bowtie returns less. Most of the light that enters goes on through the pavilion rather than back up, which is the leak below; the diamond radiant fares little better at 32.

Radiant cut in ruby face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 26) — Red, green and blue = light returning to the eye; grey = light leaving through the pavilion. This is the head-on view; the Brilliance score averages a wider cone of light, so the score can differ from what one picture shows.

T73 round brilliant in ruby face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 94) — Red, green and blue = light returning to the eye; grey = light leaving through the pavilion. This is the head-on view; the Brilliance score averages a wider cone of light, so the score can differ from what one picture shows.

What helps: Our measurements cover this geometry only, so we cannot say what other angles would return. For a brilliant face with far more light, the square Cushion Cut Ruby returns 88, and DG-M5 Ruby returns 100.

Try it yourself: Open this Light Return map in the simulator

Most of the light leaks

Leakage 67 against 5 for the T73 Round Brilliant in ruby: 62 points higher

67% of the light in our census leaves through the pavilion, the highest share of any cut we measure in ruby and well above the 41% of the diamond radiant.

Radiant cut in ruby tilted 0 degrees: Light Return map, 70% of the face leaking — Each frame is the Light Return map with the stone tilted away from you by the angle shown; grey is light leaving through the pavilion. The share under each frame is that picture's own.

Radiant cut in ruby tilted 10 degrees: Light Return map, 63% of the face leaking — Each frame is the Light Return map with the stone tilted away from you by the angle shown; grey is light leaving through the pavilion. The share under each frame is that picture's own.

What helps: The share does not shrink with the stone. DG-M5 Ruby lets out 0%, the Cushion Cut Ruby 11%.

Try it yourself: Tilt it yourself in the simulator's light map

Heavier than a diamond radiant

1.78 ct at 6.5 mm, against 1.56 ct for the same cut in diamond (+14%)

Ruby is the denser material, 4.00 against 3.52 in specific gravity, so the same radiant outline carries 14% more weight than in diamond.

A Radiant Cut 6.5 mm across, weighed from the model's measured volume and each stone's specific gravity.

What helps: Choose by millimetres, not carats.

Try it yourself: Weights in all seven gemstones on the Radiant Cut page

Slightly fewer flashes than a round

Scintillation 74 against 80 for the T73 Round Brilliant in ruby: 6 points lower

Scintillation 74 against the T73's 80: the census's model of the radiant divides its face a little less finely than the T73's.

Radiant Cut · 74 facets · Scintillation 74

T73 Round Brilliant · 73 facets · Scintillation 80

Scintillation follows the number of facets: more facets, more and smaller flashes as the stone moves. Count the facets in each crown. Drawn from each cut's own model.

What helps: The Cushion Cut Ruby scores 85 for scintillation.

Try it yourself: Compare the Scintillation spoke in the Cut Performance Wheel

Who a radiant ruby suits

The radiant suits a ruby where colour flashes and a large face per carat matter more than light: a statement piece seen across a room rather than up close. Expect a dim stone, Brilliance 26.

For a rectangle with more light, the step-cut Emerald Cut Ruby returns 65 and leaks 25%. For a large face per carat with more light, the Marquise Cut Ruby reaches 121 and returns 55.

Radiant Cut Ruby: questions

Is a radiant cut good for ruby?

For light, no: it returns 26 where the T73 returns 94, and 67% of its light leaks. For fire and face-up size it does well: 69 and 118.

Why does a radiant ruby look dark?

Because most of its light goes out of the back: 67% in our census, where the T73 Round Brilliant in ruby loses 5%.

Radiant or emerald cut ruby?

The emerald cut returns far more light (65 against 26); the radiant has more fire (69 against 47) and a larger face per carat (118 against 105).

How heavy is a 6.5 mm wide radiant ruby?

1.78 ct by our model's volume, where a diamond radiant of that width is 1.56 ct.

Get the Radiant Cut files

6 formatsMillimetresWatertight

Radiant Cut 3D files

The Radiant Cut as exact geometry: 74 planar facets, real-world scale, ready for CAD, rendering, printing and casting.

STEPExact faceted solid for CAD
3DMRhino, closed mesh on its own layer
STLWatertight mesh for printing and casting
OBJMesh for modelling and rendering
FBXBlender, 3ds Max, Maya, Cinema 4D, Unity, Unreal
GLBWeb, AR and quick previews

€9.99 · Personal useBuy the 3D files

In preparation

Radiant Cut cutting files

The faceting design for the Radiant Cut is in preparation. It will include the GemCad file, the tier table and a printable diagram.

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Questions before you buy? Email us.

More gemstones and cuts

Ruby: optical properties and the top ten cuts · The Radiant Cut: specifications, model and files

Radiant Cut Ruby: far more fire than a round, and a larger face per carat