Brilliance 61 · Fire 49 · Scintillation 78 · in our census, where the T73 scores 90 · 47 · 80 in kunzite
How the Princess Cut handles light in kunzite, measured: brilliance 61, fire 49 and 34% 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 Princess Cut in kunzite live.
The Princess Cut has 85 facets and a total depth of 68.5% of its width; its pavilion mains sit at 41.9°. In kunzite, the census returns 61 of 100 for brilliance and 49 for fire, against 90 and 47 for the T73, our benchmark, in the same stone; the same Princess Cut in diamond reads 57 and 83.
Compared with the T73 Round Brilliant in kunzite and with the Princess 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 Princess 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 1, level on 1, behind on 6.
1.34 ct at 6.5 mm, against 1.48 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 1.34 ct here and 1.48 ct in diamond, 6.5 mm across. Nothing about the light changes with it.
Try it yourself: Weights in every gemstone on the Princess Cut page
Fire 49 against 83 for the Princess 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 Princess Cut reads 49 against 83 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 Princess 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.
Brilliance 61 against 90 for the T73 Round Brilliant in kunzite: 29 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 Princess Cut returns 61 of 100 and the T73 90. The Princess Cut's pavilion mains sit at 41.9°, the T73's at 40.8°. The maps below show where each stone's light returns from and where it leaks.
Princess Cut in kunzite · Brilliance 61
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 34 against 10 for the T73 Round Brilliant in kunzite: 24 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 Princess Cut leaks 34% in kunzite against 10% for the T73 in kunzite. Grey in the maps below is leaking light; the share under each picture is that picture's own.
Princess Cut in kunzite · Leakage 34
T73 Round Brilliant in kunzite · Leakage 10
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
Tilt 73 against 89 for the Princess 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 Princess Cut keeps 73 against 89 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.
Princess Cut in kunzite · Tilt 73
Princess Cut in diamond · Tilt 89
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
Pick the Princess Cut in kunzite for this: it weighs less than in diamond. The catch: it shows less fire than in diamond, returns less light than the T73, leaks more light than the T73 and loses more light when tilted 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 Princess Cut model we traced.
In our census the Princess Cut returns 61 of 100 for brilliance and 49 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 1 pro 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 Princess Cut's pavilion mains sit at 41.9°.
At 6.5 mm across, 1.34 ct in kunzite, against 1.48 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 Princess Cut as exact geometry: 93 planar facets, real-world scale, ready for CAD, rendering, printing and casting.
The Princess Cut as a faceting design: 81 + 4 girdles = 85 facets, 96 index, 4-fold mirror-image symmetry, ready for the machine.
Save with a bundle: the Princess 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 Princess 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 Princess Cut: specifications, model and files