Radiant Cut Amethyst: Pros, Cons & Leakage

The radiant carries a brilliant facet plan under the cropped-corner outline of a step cut. Our model has 74 facets on a rectangle 1.284 times as long as wide, and it is 53.8% deep, against 61.7% for the T73.

That shallow build buys size: only the marquise and the rectangle face up larger per carat in our census. Light is another matter. Even in diamond this model returns just 32; in amethyst it returns 20, and only the Old Single leaks a larger share.

Its fire, 41, edges past the T73's 36 in quartz but sits far under the diamond radiant's.

Should you cut amethyst as a radiant? Pros and cons

Pros

A quarter lighter than diamond 1.18 vs 1.56 ct
The third-largest face per carat we measure 118 vs 100

Cons

Under a third of the T73's light 20 vs 72
About three quarters of the light leaks 76 vs 28
Far less fire than the diamond radiant 41 vs 77
Slightly less sparkle than the round 74 vs 80

Compared with the T73 Round Brilliant in amethyst 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 amethyst (white) against the T73 Round Brilliant in amethyst (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 amethyst: ahead on 3, behind on 5.

Global51, the comparison 70, difference −19
Brilliance20, the comparison 72, difference −52
Fire41, the comparison 36, difference +5
Scintillation74, the comparison 80, difference −6
Spread105, the comparison 100, difference +5
Symmetry99, the comparison 100, difference −1
Shape-norm24, the comparison 77, difference −53
Tilt100, the comparison 80, difference +20

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 amethyst gains in a radiant

A quarter lighter than diamond

1.18 ct at 6.5 mm, against 1.56 ct for the same cut in diamond (−25%)

A specific gravity of 2.65 against 3.52 takes a quarter off a radiant of any given size. Together with its large face per carat, that gives a lot of face for very little weight.

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

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

The third-largest face per carat we measure

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

Measured from the outline, a carat of this radiant covers more area than every cut we measure except the marquise and the rectangle. At 53.8% deep it keeps little weight below the girdle.

Radiant Cut · 7.59 x 4.14 mm at 1.00 ct · Face-up size 118

T73 Round Brilliant · 7.12 mm at 1.00 ct · Face-up size 100

Both stones weigh 1.00 ct in amethyst 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 amethyst in the 3D Gemstone Simulator

The radiant's costs in amethyst

Under a third of the T73's light

Brilliance 20 against 72 for the T73 Round Brilliant in amethyst: 52 points lower

Of all the cuts we measure in amethyst, only DG-Bowtie and the Old Single return less. With so shallow a build, much of the light that enters meets the pavilion at angles quartz cannot hold.

Radiant cut in amethyst face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 20) — 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 amethyst face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 72) — 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: We have not measured a deeper radiant, so we promise none. In a rectangle, the Emerald Cut Amethyst returns 53; in a square, the Cushion Cut Amethyst 69.

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

About three quarters of the light leaks

Leakage 76 against 28 for the T73 Round Brilliant in amethyst: 48 points higher

Leakage is the share of light in our census that leaves through the pavilion instead of the crown. The diamond radiant loses 41%; in amethyst it loses 76%, the second-highest share we measure in this stone.

Radiant cut in amethyst tilted 0 degrees: Light Return map, 76% 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 amethyst tilted 10 degrees: Light Return map, 68% 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: A small radiant leaks the same share as a large one. The Cushion Cut Amethyst loses 31% in amethyst, DG-M5 Amethyst 15%.

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

Far less fire than the diamond radiant

Fire 41 against 77 for the Radiant Cut in diamond: 36 points lower

In amethyst the radiant scores 41 for fire, against 77 for the diamond radiant. Our fire score is a share of the light that returns, so the radiant's low brilliance does not pull it down: it still edges the T73 for fire in amethyst.

Radiant cut in amethyst face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 41) — 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.

Radiant cut in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 77) — 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.

What helps: For more fire in a stone that stays bright, DG-Anteros Amethyst (54) or DG-M5 Amethyst (50).

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

Slightly less sparkle than the round

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

In our model it has about as many facets as the T73, 74 against 73, yet it scores a few points less. Our score counts only facets that reach the surface, and the census scores its own radiant geometry, which has fewer of them than our model.

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: In a long outline, the Oval Cut Amethyst scores 87 for scintillation.

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

Who a radiant amethyst suits

Choose the radiant in amethyst when size for weight leads and the colour of the stone is the show. It gives the third-largest face per carat we measure, at three quarters of diamond's weight.

If light matters, look elsewhere: the Emerald Cut Amethyst keeps a rectangle and returns over twice as much, and the Oval Cut Amethyst keeps a long outline with more light and sparkle.

Radiant Cut Amethyst: questions

Is a radiant cut good for amethyst?

For face-up size, yes: 118 against 100 for the T73. Light is its weakness: Brilliance 20 where the T73 scores 72, and 76% of the light leaks.

Why does a radiant amethyst return so little light?

In our census 76% of its light leaves through the pavilion, against 28% for the T73. The model is shallow, 53.8% deep.

Radiant or emerald cut amethyst?

The emerald cut returns more light (53 against 20); the radiant faces up larger per carat (118 against 105) and has more fire (41 against 32).

What does a 6.5 mm wide radiant amethyst weigh?

1.18 ct, against 1.56 ct in diamond.

Get the Radiant Cut files

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Radiant Cut 3D files

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

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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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More gemstones and cuts

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

Radiant Cut Amethyst: more face per carat than all but two cuts we measure