Cushion Cut Zircon: brighter in zircon than in diamond
Brilliance 91 · Fire 74 · Scintillation 85 · in our census, where the T73 scores 98 · 69 · 80 in zircon
How the Cushion Cut handles light in zircon, measured: brilliance 91, fire 74 and 8% leakage, set against the T73 in the same stone and against the same cut in diamond.
Light Return map of the Cushion Cut in zircon, face-up, from our own tracer at refractive index 1.925. Red, green and blue return light to the eye; gray leaks.
Cushion Cut Zircon
Zircon has a refractive index of 1.925 to 1.984 and a dispersion of 0.039. Its critical angle, from the low end of that range, is 31.3°, so a round design needs a pavilion of at least 37.2° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.955, the midpoint of the published range, and a fire spread of 0.034, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 1.925, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the Cushion Cut in zircon live. Zircon is strongly doubly refractive (birefringence up to 0.059), so its back facets can look doubled. Our census traces one index (1.955), so the doubling is not in these figures.
The Cushion Cut has 85 facets and a total depth of 65.0% of its width; its pavilion mains sit at 39.6°. In zircon, the census returns 91 of 100 for brilliance and 74 for fire, against 98 and 69 for the T73, our benchmark, in the same stone; the same Cushion Cut in diamond reads 80 and 73.
Is zircon good in a Cushion? Pros and cons, measured
Compared with the T73 Round Brilliant in zircon and with the Cushion 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 Cushion Cut in zircon (white) against the T73 Round Brilliant in zircon (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 zircon: ahead on 3, behind on 5.
Global85, the comparison 88, difference −3
Brilliance91, the comparison 98, difference −7
Fire74, the comparison 69, difference +5
Scintillation85, the comparison 80, difference +5
Spread98, the comparison 100, difference −2
Symmetry97, the comparison 100, difference −3
Shape-norm106, the comparison 105, difference +1
Tilt76, the comparison 82, difference −6
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; these are the same census figures as our Cut Performance Index.
What the Cushion Cut gains in zircon
Brighter in zircon than in diamond
Brilliance 91 against 80 for the Cushion Cut in diamond: 11 points higher
The same cut in diamond returns 80. Zircon bends light less than diamond: its critical angle is 31.3°, diamond's 24.4°, so a pavilion facet has to be steeper before light reflects off it rather than passing out. The Cushion Cut's pavilion returns more of zircon's light than of diamond's, as the two maps show.
Cushion Cut in zircon · Brilliance 91
Cushion Cut in diamond · Brilliance 80
Red, green and blue = light returning to the eye; gray = leakage, light that leaves heading down or stays inside. 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.
Fire 74 against 69 for the T73 Round Brilliant in zircon: 5 points higher
Fire is the share of the returned light that splits into color at the exit facet: the census traces each exit again at the refractive index minus and plus the fire spread (0.034 in zircon) and counts a ray as fire when the two directions differ by more than 0.6°. The Cushion Cut reads 74 against 69 for the T73 in zircon. The figure is the census's; the 3D Gemstone Simulator renders zircon's fire live.
The fire figure is the census's, traced at the refractive index minus and plus the fire spread. See the fire in the 3D Gemstone Simulator: the Cushion Cut in zircon under the sunny-day lighting.
Scintillation 85 against 80 for the T73 Round Brilliant in zircon: 5 points higher
Scintillation follows the number of facets the stone shows: 100 × (1 − e^(−facets / 45)). The Cushion Cut has 85 facets and the T73 73, so 85 against 80. It depends on the geometry alone, so it is the same in every stone.
Scintillation follows the number of facets: more facets, more and smaller flashes as the stone moves. Compare the facet counts under the drawings; each drawing shows only the crown. Drawn from each cut's own model.
1.68 ct at 6.5 mm, against 1.27 ct for the same cut in diamond (+33%)
Weight follows specific gravity: 4.665 for zircon against 3.52 for diamond, so the same model at the same size weighs 1.68 ct here and 1.27 ct in diamond, 6.5 mm across. Nothing about the light changes with it.
A Cushion Cut 6.5 mm across, weighed from the model's measured volume and each stone's specific gravity.
Tilt 76 against 92 for the Cushion Cut in diamond: 16 points lower
Tilt is how much of its face-up brilliance a stone keeps when the census tilts it 20° about its long axis, with 2,200 rays. The Cushion Cut keeps 76 against 92 for the same cut in diamond. The tilt strips below show the maps at 0°, 10°, 20° and 30°, with each picture's own leak share under it.
Cushion Cut in zircon · Tilt 76
0° · 6% leak
10° · 10% leak
20° · 25% leak
30° · 37% leak
Cushion Cut in diamond · Tilt 92
0° · 16% leak
10° · 8% leak
20° · 14% leak
30° · 22% leak
Tilt is how much of its own face-up light a stone keeps when tilted. Each frame is the Light Return map with the stone tilted away from you by the angle shown; gray is leakage. The share under each frame is that picture's own.
What helps:the DG-M5 reads 98 for tilt in zircon, the best of the cuts we score there.
Leakage 8 against 2 for the T73 Round Brilliant in zircon: 6 points higher
Leakage is the share of the census rays that enter the stone and leave through the pavilion, or through the crown heading down. The Cushion Cut leaks 8% in zircon against 2% for the T73 in zircon. Grey in the maps below is leaking light; the share under each picture is that picture's own.
Cushion Cut in zircon · Leakage 8
0° · 6% leak
10° · 10% leak
20° · 25% leak
30° · 37% leak
T73 Round Brilliant in zircon · Leakage 2
0° · 1% leak
10° · 6% leak
20° · 15% leak
30° · 26% leak
Each frame is the Light Return map with the stone tilted away from you by the angle shown; gray is leakage. The share under each frame is that picture's own.
Pick the Cushion Cut in zircon for this: it returns more light than in diamond, shows more fire than the T73 and has more facets to sparkle with. The catch: it weighs more than in diamond, loses more light when tilted than in diamond and leaks more light than the T73.
If that catch matters more to you, the DG-M5 reads 98 for tilt in zircon, the best of the cuts we score there.
Every figure on this page is from our light census, traced at one refractive index: a simulation of the geometry, not a grading report. The 3D files and cutting files below are the same Cushion Cut model we traced.
Cushion Cut Zircon: questions
Is the Cushion a good cut for zircon?
In our census the Cushion Cut returns 91 of 100 for brilliance and 74 for fire in zircon, against 98 and 69 for the T73 in the same stone. Against that round and against the same cut in diamond it has 3 pros and 3 cons by our thresholds; the summary above names them.
What pavilion angle does zircon need?
At least 37.2° for a round design: zircon's critical angle is 31.3°, from the low end of its refractive index range, and head-on light has to reflect off both sides of the pavilion and leave through the table. The Cushion Cut's pavilion mains sit at 39.6°.
How much does a Cushion weigh in zircon?
At 6.5 mm across, 1.68 ct in zircon, against 1.27 ct for the same cut in diamond (+33%): zircon's specific gravity is 4.665, diamond's 3.52.
Can I see the Cushion in zircon in 3D?
Yes: the 3D Gemstone Simulator renders it live, with zircon's own refractive index and dispersion. Zircon is traced by the same light census as the other gemstones, with its refractive index and fire spread derived from published values, so its scores are on the same scale; the pictures here are our Light Return tracer, and the Cut Performance Wheel sets it against any other cut and stone.
Get the Cushion Cut files
6 formatsMillimetersWatertight
Cushion Cut 3D files
The Cushion Cut as exact geometry: 85 planar facets, real-world scale, ready for CAD,
rendering, printing and casting.
Save with a bundle: the Cushion Cut 3D files are also in Jewelry Essentials 3D, 10 cuts for €29.99 until 1 December, then €39.99 (€99.90 as single files). Buy the bundle.
Save with a bundle: the Cushion Cut cutting files are also in Faceter's Classics, 10 cuts for €22.49 until 1 December, then €29.99 (€69.90 as single files). Buy the bundle.
Not sure the files open in your software? Get the cube free: the same six formats, for your email address, used only to send them (privacy).
