Brilliance 84 · Fire 39 · Scintillation 85 · in our census, where the T73 scores 90 · 47 · 80 in kunzite
How the Cushion Cut handles light in kunzite, measured: brilliance 84, fire 39 and 15% leakage, set against the T73 in the same stone and against the same cut in diamond.
Kunzite has a refractive index of 1.660 to 1.676 and a dispersion of 0.017. Its critical angle, from the low end of that range, is 37.0°, so a round design needs a pavilion of at least 37.0° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.668, the midpoint of the published range, and a fire spread of 0.015, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 1.660, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the Cushion Cut in kunzite live.
The Cushion Cut has 85 facets and a total depth of 65.0% of its width; its pavilion mains sit at 39.6°. In kunzite, the census returns 84 of 100 for brilliance and 39 for fire, against 90 and 47 for the T73, our benchmark, in the same stone; the same Cushion Cut in diamond reads 80 and 73.
Compared with the T73 Round Brilliant in kunzite 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.
At a glance: the Cushion Cut in kunzite (white) against the T73 Round Brilliant in kunzite (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 kunzite: ahead on 2, behind on 6.
1.15 ct at 6.5 mm, against 1.27 ct for the same cut in diamond (−10%)
Weight follows specific gravity: 3.18 for kunzite against 3.52 for diamond, so the same model at the same size weighs 1.15 ct here and 1.27 ct in diamond, 6.5 mm across. Nothing about the light changes with it.
Try it yourself: Weights in every gemstone on the Cushion Cut page
Scintillation 85 against 80 for the T73 Round Brilliant in kunzite: 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.
Cushion Cut · 85 facets · Scintillation 85
T73 Round Brilliant · 73 facets · Scintillation 80
Try it yourself: Compare the Scintillation spoke in the Cut Performance Wheel
Fire 39 against 73 for the Cushion Cut in diamond: 34 points lower
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 (0.015 in kunzite) and counts a ray as fire when the two directions differ by more than 0.6°. The Cushion Cut reads 39 against 73 for the same cut in diamond. The figure is the census's; the 3D Gemstone Simulator renders kunzite'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 kunzite under the sunny-day lighting.
What helps: the Oval Cut reads 78 for fire in kunzite, the best of the cuts we score there.
Tilt 69 against 92 for the Cushion Cut in diamond: 23 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 69 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 kunzite · Tilt 69
Cushion Cut in diamond · Tilt 92
What helps: the DG-Miliano reads 84 for tilt in kunzite, the best of the cuts we score there.
Try it yourself: Compare the Tilt spoke in the Cut Performance Wheel
Brilliance 84 against 90 for the T73 Round Brilliant in kunzite: 6 points lower
Brilliance is the share of the 3,200 census rays that enter the stone and come back out of the crown towards the viewer. In kunzite, whose critical angle is 37.0°, the Cushion Cut returns 84 of 100 and the T73 90. The Cushion Cut's pavilion mains sit at 39.6°, the T73's at 40.8°. The maps below show where each stone's light returns from and where it leaks.
Cushion Cut in kunzite · Brilliance 84
T73 Round Brilliant in kunzite · Brilliance 90
What helps: the DG-M5 reads 99 for brilliance in kunzite, the best of the cuts we score there.
Try it yourself: Open this Light Return map in the simulator
Leakage 15 against 9 for the Cushion Cut in diamond: 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 15% in kunzite against 9% for the same cut in diamond. Grey in the maps below is leaking light; the share under each picture is that picture's own.
Cushion Cut in kunzite · Leakage 15
Cushion Cut in diamond · Leakage 9
What helps: the DG-M5 reads 1% for leakage in kunzite, the best of the cuts we score there.
Try it yourself: Tilt it yourself in the simulator's light map
Pick the Cushion Cut in kunzite for this: it weighs less than in diamond and has more facets to sparkle with. The catch: it shows less fire than in diamond, loses more light when tilted than in diamond, returns less light than the T73 and leaks more than in diamond.
If that catch matters more to you, the Oval Cut reads 78 for fire in kunzite, 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.
In our census the Cushion Cut returns 84 of 100 for brilliance and 39 for fire in kunzite, against 90 and 47 for the T73 in the same stone. Against that round and against the same cut in diamond it has 2 pros and 4 cons by our thresholds; the summary above names them.
At least 37.0° for a round design: kunzite's critical angle is 37.0°, 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°.
At 6.5 mm across, 1.15 ct in kunzite, against 1.27 ct for the same cut in diamond (-10%): kunzite's specific gravity is 3.18, diamond's 3.52.
Yes: the 3D Gemstone Simulator renders it live, with kunzite's own refractive index and dispersion. Kunzite 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.
The Cushion Cut as exact geometry: 85 planar facets, real-world scale, ready for CAD, rendering, printing and casting.
The Cushion Cut as a faceting design: 69 + 16 girdles = 85 facets, 96 index, 2-fold mirror-image symmetry, ready for the machine.
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).
Questions before you buy? Email us.
Kunzite: optical properties and the top ten cuts · The Cushion Cut: specifications, model and files