T57 Round Brilliant Grossular: faces up larger for its weight
Brilliance 94 · Fire 59 · Scintillation 72 · in our census, where the T73 scores 94 · 58 · 80 in grossular
How the T57 Round Brilliant handles light in grossular, measured: brilliance 94, fire 59 and 6% leakage, set against the T73 in the same stone and against the same cut in diamond.
Light Return map of the T57 Round Brilliant in grossular, face-up, from our own tracer at refractive index 1.73. Red, green and blue return light to the eye; gray leaks.
T57 Round Brilliant Grossular
Grossular has a refractive index of 1.730 to 1.760 and a dispersion of 0.028. Its critical angle, from the low end of that range, is 35.3°, so a round design needs a pavilion of at least 36.2° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.745, the midpoint of the published range, and a fire spread of 0.024, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 1.730, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the T57 Round Brilliant in grossular live.
The T57 Round Brilliant has 57 facets and a total depth of 59.2% of its width; its pavilion mains sit at 40.8°. In grossular, the census returns 94 of 100 for brilliance and 59 for fire, against 94 and 58 for the T73, our benchmark, in the same stone; the same T57 Round Brilliant in diamond reads 92 and 79.
Is grossular good in a T57? Pros and cons, measured
Compared with the T73 Round Brilliant in grossular and with the T57 Round Brilliant 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 T57 Round Brilliant in grossular (white) against the T73 Round Brilliant in grossular (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 grossular: ahead on 2, level on 3, behind on 3.
Global82, the comparison 83, difference −1
Brilliance94, the comparison 94, difference 0
Fire59, the comparison 58, difference +1
Scintillation72, the comparison 80, difference −8
Spread101, the comparison 100, difference +1
Symmetry100, the comparison 100, difference 0
Shape-norm101, the comparison 101, difference 0
Tilt73, the comparison 74, difference −1
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 T57 Round Brilliant gains in grossular
Faces up larger for its weight
Face-up size 107 against 100 for the T73 Round Brilliant in grossular (T73 = 100): 7% more face-up area for the same weight
Face-up size is the outline's area per carat, measured from each model (T73 = 100): 107 for the T57 Round Brilliant against 100 for the T73. The same volume spread over a longer or shallower outline shows more face for the weight; it is the same in every stone, because specific gravity scales every cut alike.
T57 Round Brilliant · 6.62 mm at 1.00 ct · Face-up size 107
T73 Round Brilliant · 6.41 mm at 1.00 ct · Face-up size 100
Both stones weigh 1.00 ct in grossular and are drawn to the same scale in millimeters, 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.
What the T57 Round Brilliant gives up in grossular
Less fire in grossular than in diamond
Fire 59 against 79 for the T57 Round Brilliant in diamond: 20 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 (0.024 in grossular) and counts a ray as fire when the two directions differ by more than 0.6°. The T57 Round Brilliant reads 59 against 79 for the same cut in diamond. The figure is the census's; the 3D Gemstone Simulator renders grossular'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 T57 Round Brilliant in grossular under the sunny-day lighting.
What helps:the DG-Elongated Hexagon reads 90 for fire in grossular, the best of the cuts we score there.
Tilt 73 against 90 for the T57 Round Brilliant in diamond: 17 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 T57 Round Brilliant keeps 73 against 90 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.
T57 Round Brilliant in grossular · Tilt 73
0° · 0% leak
10° · 15% leak
20° · 28% leak
30° · 31% leak
T57 Round Brilliant in diamond · Tilt 90
0° · 4% leak
10° · 2% leak
20° · 10% leak
30° · 16% 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-Miliano reads 83 for tilt in grossular, the best of the cuts we score there.
Scintillation 72 against 80 for the T73 Round Brilliant in grossular: 8 points lower
Scintillation follows the number of facets the stone shows: 100 × (1 − e^(−facets / 45)). The T57 Round Brilliant has 57 facets and the T73 73, so 72 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.
What helps:the DG-Miliano reads 98 for scintillation in grossular, the best of the cuts we score there.
Leakage 6 against 2 for the T57 Round Brilliant in diamond: 4 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 T57 Round Brilliant leaks 6% in grossular against 2% for the same cut in diamond. Grey in the maps below is leaking light; the share under each picture is that picture's own.
T57 Round Brilliant in grossular · Leakage 6
0° · 0% leak
10° · 15% leak
20° · 28% leak
30° · 31% leak
T57 Round Brilliant in diamond · Leakage 2
0° · 4% leak
10° · 2% leak
20° · 10% leak
30° · 16% 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.
What helps:the DG-M5 reads 0% for leakage in grossular, the best of the cuts we score there.
Our verdict on the T57 Round Brilliant in grossular
Pick the T57 Round Brilliant in grossular for this: it faces up larger for its weight. The catch: it shows less fire than in diamond, loses more light when tilted than in diamond, has fewer facets to sparkle with and leaks more than in diamond.
If that catch matters more to you, the DG-Elongated Hexagon reads 90 for fire in grossular, 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 T57 Round Brilliant model we traced.
T57 Round Brilliant Grossular: questions
Is the T57 a good cut for grossular?
In our census the T57 Round Brilliant returns 94 of 100 for brilliance and 59 for fire in grossular, against 94 and 58 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.
What pavilion angle does grossular need?
At least 36.2° for a round design: grossular's critical angle is 35.3°, 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 T57 Round Brilliant's pavilion mains sit at 40.8°.
How much does a T57 weigh in grossular?
At 6.5 mm across, 0.95 ct in grossular, against 0.92 ct for the same cut in diamond (+3%): grossular's specific gravity is 3.64, diamond's 3.52.
Can I see the T57 in grossular in 3D?
Yes: the 3D Gemstone Simulator renders it live, with grossular's own refractive index and dispersion. Grossular 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 T57 Round Brilliant Cut files
6 formatsMillimetersWatertight
T57 Round Brilliant Cut 3D files
The T57 Round Brilliant Cut as exact geometry: 57 planar facets, real-world scale, ready for CAD,
rendering, printing and casting.
Save with a bundle: the T57 Round Brilliant Cut 3D and cutting files are also in Historic Cuts Complete, 6 cuts for €29.99 until 1 December, then €39.99 (€101.88 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).
