T73 Round Brilliant Strontium titanate: more fire in strontium titanate than in diamond
Brilliance 93 · Fire 98 · Scintillation 80 · in our census, where the T57 scores 92 · 98 · 72 in strontium titanate
How the T73 Round Brilliant handles light in strontium titanate, measured: brilliance 93, fire 98 and 2% leakage, set against the T57 in the same stone and against the same cut in diamond.
Light Return map of the T73 Round Brilliant in strontium titanate, face-up, from our own tracer at refractive index 2.409. Red, green and blue return light to the eye; gray leaks.
T73 Round Brilliant Strontium titanate
Strontium titanate has a refractive index of 2.409 and a dispersion of 0.190. Its critical angle, from the low end of that range, is 24.5°, so a round design needs a pavilion of at least 38.9° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 2.409, the midpoint of the published range, and a fire spread of 0.163, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 2.409, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the T73 Round Brilliant in strontium titanate live. Strontium titanate has nearly diamond's refractive index (2.409 against 2.417) with about four times its dispersion (0.190 against 0.044): light takes much the same paths as in diamond, and far more of it splits into color.
The T73 Round Brilliant has 73 facets and a total depth of 61.7% of its width; its pavilion mains sit at 40.8°. In strontium titanate, the census returns 93 of 100 for brilliance and 98 for fire, against 92 and 98 for the T57, our benchmark, in the same stone; the same T73 Round Brilliant in diamond reads 93 and 78.
Is strontium titanate good in a T73? Pros and cons, measured
Compared with the T57 Round Brilliant in strontium titanate and with the T73 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 T57
At a glance: the T73 Round Brilliant in strontium titanate (white) against the T57 Round Brilliant in strontium titanate (dashed): solid white where
it reaches further, hatched where it falls short. Each pro and con is explained, with pictures, below.
Against the T57 Round Brilliant in strontium titanate: ahead on 5, level on 2, behind on 1.
Global94, the comparison 92, difference +2
Brilliance93, the comparison 92, difference +1
Fire98, the comparison 98, difference 0
Scintillation80, the comparison 72, difference +8
Spread100, the comparison 101, difference −1
Symmetry100, the comparison 100, difference 0
Shape-norm100, the comparison 99, difference +1
Tilt92, the comparison 90, difference +2
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 T73 Round Brilliant gains in strontium titanate
More fire in strontium titanate than in diamond
Fire 98 against 78 for the T73 Round Brilliant in diamond: 20 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 (0.163 in strontium titanate) and counts a ray as fire when the two directions differ by more than 0.6°. The T73 Round Brilliant reads 98 against 78 for the same cut in diamond. The figure is the census's; the 3D Gemstone Simulator renders strontium titanate'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 T73 Round Brilliant in strontium titanate under the sunny-day lighting.
Scintillation 80 against 72 for the T57 Round Brilliant in strontium titanate: 8 points higher
Scintillation follows the number of facets the stone shows: 100 × (1 − e^(−facets / 45)). The T73 Round Brilliant has 73 facets and the T57 57, so 80 against 72. 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 the T73 Round Brilliant gives up in strontium titanate
Heavier than the same cut in diamond
1.47 ct at 6.5 mm, against 1.01 ct for the same cut in diamond (+46%)
Weight follows specific gravity: 5.13 for strontium titanate against 3.52 for diamond, so the same model at the same size weighs 1.47 ct here and 1.01 ct in diamond, 6.5 mm across. Nothing about the light changes with it.
A T73 Round Brilliant 6.5 mm across, weighed from the model's measured volume and each stone's specific gravity.
Face-up size 100 against 107 for the T57 Round Brilliant in strontium titanate (T73 = 100): 7% less face-up area for the same weight
Face-up size is the outline's area per carat, measured from each model (T73 = 100): 100 for the T73 Round Brilliant against 107 for the T57. 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.
T73 Round Brilliant · 5.72 mm at 1.00 ct · Face-up size 100
T57 Round Brilliant · 5.90 mm at 1.00 ct · Face-up size 107
Both stones weigh 1.00 ct in strontium titanate 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 helps:the Marquise Cut reads 121 for face-up size in strontium titanate, the best of the cuts we score there.
Our verdict on the T73 Round Brilliant in strontium titanate
Pick the T73 Round Brilliant in strontium titanate for this: it shows more fire than in diamond and has more facets to sparkle with. The catch: it weighs more than in diamond and faces up smaller for its weight.
If that catch matters more to you, the Marquise Cut reads 121 for face-up size in strontium titanate, 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 T73 Round Brilliant model we traced.
T73 Round Brilliant Strontium titanate: questions
Is the T73 a good cut for strontium titanate?
In our census the T73 Round Brilliant returns 93 of 100 for brilliance and 98 for fire in strontium titanate, against 92 and 98 for the T57 in the same stone. Against that round and against the same cut in diamond it has 2 pros and 2 cons by our thresholds; the summary above names them.
What pavilion angle does strontium titanate need?
At least 38.9° for a round design: strontium titanate's critical angle is 24.5°, 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 T73 Round Brilliant's pavilion mains sit at 40.8°.
How much does a T73 weigh in strontium titanate?
At 6.5 mm across, 1.47 ct in strontium titanate, against 1.01 ct for the same cut in diamond (+46%): strontium titanate's specific gravity is 5.13, diamond's 3.52.
Can I see the T73 in strontium titanate in 3D?
Yes: the 3D Gemstone Simulator renders it live, with strontium titanate's own refractive index and dispersion. Strontium titanate 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 T73 Round Brilliant Cut files
6 formatsMillimetersWatertight
T73 Round Brilliant Cut 3D files
The T73 Round Brilliant Cut as exact geometry: 73 planar facets, real-world scale, ready for CAD,
rendering, printing and casting.
Save with a bundle: the T73 Round Brilliant 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.
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).
