Oval Cut Tanzanite: more fire than the T73 in tanzanite
Brilliance 64 · Fire 79 · Scintillation 87 · in our census, where the T73 scores 92 · 47 · 80 in tanzanite
How the Oval Cut handles light in tanzanite, measured: brilliance 64, fire 79 and 30% leakage, set against the T73 in the same stone and against the same cut in diamond.
Light Return map of the Oval Cut in tanzanite, face-up, from our own tracer at refractive index 1.685. Red, green and blue return light to the eye; gray leaks.
Oval Cut Tanzanite
Tanzanite has a refractive index of 1.685 to 1.707 and a dispersion of 0.019. Its critical angle, from the low end of that range, is 36.4°, so a round design needs a pavilion of at least 36.4° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.696, the midpoint of the published range, and a fire spread of 0.016, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 1.685, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the Oval Cut in tanzanite live.
The Oval Cut has 93 facets and a total depth of 64.0% of its width; its pavilion mains sit at 41.0°. In tanzanite, the census returns 64 of 100 for brilliance and 79 for fire, against 92 and 47 for the T73, our benchmark, in the same stone; the same Oval Cut in diamond reads 47 and 92.
Is tanzanite good in an Oval? Pros and cons, measured
Compared with the T73 Round Brilliant in tanzanite and with the Oval 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 Oval Cut in tanzanite (white) against the T73 Round Brilliant in tanzanite (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 tanzanite: ahead on 2, behind on 6.
Global73, the comparison 80, difference −7
Brilliance64, the comparison 92, difference −28
Fire79, the comparison 47, difference +32
Scintillation87, the comparison 80, difference +7
Spread99, the comparison 100, difference −1
Symmetry98, the comparison 100, difference −2
Shape-norm74, the comparison 99, difference −25
Tilt61, the comparison 73, difference −12
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 Oval Cut gains in tanzanite
More fire than the T73 in tanzanite
Fire 79 against 47 for the T73 Round Brilliant in tanzanite: 32 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 (0.016 in tanzanite) and counts a ray as fire when the two directions differ by more than 0.6°. The Oval Cut reads 79 against 47 for the T73 in tanzanite. The figure is the census's; the 3D Gemstone Simulator renders tanzanite'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 Oval Cut in tanzanite under the sunny-day lighting.
Face-up size 108 against 100 for the T73 Round Brilliant in tanzanite (T73 = 100): 8% more face-up area for the same weight
Face-up size is the outline's area per carat, measured from each model (T73 = 100): 108 for the Oval Cut 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.
Oval Cut · 7.81 x 5.87 mm at 1.00 ct · Face-up size 108
T73 Round Brilliant · 6.58 mm at 1.00 ct · Face-up size 100
Both stones weigh 1.00 ct in tanzanite 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.
Scintillation 87 against 80 for the T73 Round Brilliant in tanzanite: 7 points higher
Scintillation follows the number of facets the stone shows: 100 × (1 − e^(−facets / 45)). The Oval Cut has 93 facets and the T73 73, so 87 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.
1.36 ct at 6.5 mm, against 1.42 ct for the same cut in diamond (−5%)
Weight follows specific gravity: 3.35 for tanzanite against 3.52 for diamond, so the same model at the same size weighs 1.36 ct here and 1.42 ct in diamond, 6.5 mm across. Nothing about the light changes with it.
A Oval Cut 6.5 mm across, weighed from the model's measured volume and each stone's specific gravity.
Tilt 61 against 92 for the Oval Cut in diamond: 31 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 Oval Cut keeps 61 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.
Oval Cut in tanzanite · Tilt 61
0° · 34% leak
10° · 37% leak
20° · 47% leak
30° · 53% leak
Oval Cut in diamond · Tilt 92
0° · 31% leak
10° · 31% leak
20° · 32% leak
30° · 35% 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 84 for tilt in tanzanite, the best of the cuts we score there.
Brilliance 64 against 92 for the T73 Round Brilliant in tanzanite: 28 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 tanzanite, whose critical angle is 36.4°, the Oval Cut returns 64 of 100 and the T73 92. The Oval Cut's pavilion mains sit at 41.0°, the T73's at 40.8°. The maps below show where each stone's light returns from and where it leaks.
Oval Cut in tanzanite · Brilliance 64
T73 Round Brilliant in tanzanite · Brilliance 92
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.
What helps:the DG-M5 reads 100 for brilliance in tanzanite, the best of the cuts we score there.
Leakage 30 against 8 for the T73 Round Brilliant in tanzanite: 22 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 Oval Cut leaks 30% in tanzanite against 8% for the T73 in tanzanite. Grey in the maps below is leaking light; the share under each picture is that picture's own.
Oval Cut in tanzanite · Leakage 30
0° · 34% leak
10° · 37% leak
20° · 47% leak
30° · 53% leak
T73 Round Brilliant in tanzanite · Leakage 8
0° · 9% leak
10° · 19% leak
20° · 30% leak
30° · 32% 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 tanzanite, the best of the cuts we score there.
Pick the Oval Cut in tanzanite for this: it shows more fire than the T73, faces up larger for its weight, has more facets to sparkle with and weighs less than in diamond. The catch: it loses more light when tilted than in diamond, returns less light than the T73 and leaks more light than the T73.
If that catch matters more to you, the DG-Miliano reads 84 for tilt in tanzanite, 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 Oval Cut model we traced.
Oval Cut Tanzanite: questions
Is the Oval a good cut for tanzanite?
In our census the Oval Cut returns 64 of 100 for brilliance and 79 for fire in tanzanite, against 92 and 47 for the T73 in the same stone. Against that round and against the same cut in diamond it has 4 pros and 3 cons by our thresholds; the summary above names them.
What pavilion angle does tanzanite need?
At least 36.4° for a round design: tanzanite's critical angle is 36.4°, 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 Oval Cut's pavilion mains sit at 41.0°.
How much does a Oval weigh in tanzanite?
At 6.5 mm across, 1.36 ct in tanzanite, against 1.42 ct for the same cut in diamond (-5%): tanzanite's specific gravity is 3.35, diamond's 3.52.
Can I see the Oval in tanzanite in 3D?
Yes: the 3D Gemstone Simulator renders it live, with tanzanite's own refractive index and dispersion. Tanzanite 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 Oval Cut files
6 formatsMillimetersWatertight
Oval Cut 3D files
The Oval Cut as exact geometry: 97 planar facets, real-world scale, ready for CAD,
rendering, printing and casting.
Save with a bundle: the Oval 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 Oval 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).
