T105 Round Brilliant Diamond: finer sparkle than the T73 on the same main angles
Brilliance 95 · Fire 77 · Scintillation 90 · in our census, where the T73 scores 93 · 78 · 80 in diamond
The 1919 round, divided more finely and finished to a knife edge: more scintillation than the T73, the least leakage in our diamond census, and a weaker hold on its light when tipped.
Rendered in our 3D Gemstone Simulator from the T105 Round Brilliant model, 1.00 ct, studio light.
T105 Round Brilliant Diamond
Take the T57, keep its main angles, and divide it further: eight star halves on the crown, and on the pavilion three rows of lower halves where the T57 has one, plus eight pavilion star halves at the girdle. That is the T105. Like the T57 it has no girdle band, so crown and pavilion meet at a knife edge. In all, the T105 model counts 105 facets on the T57's 40.75° pavilion, 59.3% deep.
We compare it with the T73 Round Brilliant, which shares its main angles. The extra facets lift scintillation clearly. Brilliance edges ahead, 95 against 93, though not by enough to count, and its leakage of 1% is the lowest of any cut we measure in diamond.
Is a T105 round brilliant good in diamond? Pros and cons
Compared with the T73 Round Brilliant in diamond.
A difference counts from 3 points (Brilliance, Fire, Tilt, Leakage), 5 (Scintillation,
Symmetry), 2 (Spread) 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 T105 Round Brilliant in diamond (white) against the T73 Round Brilliant in diamond (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 diamond: ahead on 5, level on 1, behind on 2.
Global91, the comparison 90, difference +1
Brilliance95, the comparison 93, difference +2
Fire77, the comparison 78, difference −1
Scintillation90, the comparison 80, difference +10
Spread101, the comparison 100, difference +1
Symmetry100, the comparison 100, difference 0
Shape-norm102, the comparison 100, difference +2
Tilt87, the comparison 92, difference −5
Face-up light census, a different measure from the Cut Grading Tool; Spread and Shape-norm above 100 sit on the ring.
Scintillation 90 against 80 for the T73 Round Brilliant in diamond: 10 points higher
The added rows split the plan into smaller facets, and our scintillation score follows the facet count: 105 against the T73's 73. It still sits below DG-Rafaello and DG-Miliano, which carry more facets again.
Scintillation follows the number of facets: more facets, more and smaller flashes as the stone moves. Count the facets in each crown. Drawn from each cut's own model.
Tilt 87 against 92 for the T73 Round Brilliant in diamond: 5 points lower
Tipped by 20°, it holds 87 of its face-up light, against 92 for the T73. The gap is at the edge of our threshold. Over the whole census it leaks less than any cut we measure, so this is a narrower point: how much of its face-up light survives a tip.
T105 Round Brilliant in diamond · Tilt 87
0° · 2% leak
10° · 2% leak
20° · 11% leak
30° · 14% leak
T73 Round Brilliant in diamond · Tilt 92
0° · 4% leak
10° · 2% leak
20° · 9% leak
30° · 14% 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; grey is light leaving through the pavilion. The share under each frame is that picture's own.
What helps: The angles are not the problem: the 40.75° pavilion is the T73's own and sits above diamond's 38.9° guide minimum, so steepening is not the fix. If the stone will often be seen at an angle, DG-Rafaello Diamond holds 97 and the T73 Round Brilliant Diamond 92.
Choose the T105 for a classic round that sparkles more finely than the T73 and lets the least light out of the back of anything we measure. It suits a cutter who wants the 1919 angles with a richer facet plan.
The knife-edge girdle needs protecting in a setting; if the setter needs a girdle to seat, the T73 Round Brilliant Diamond is the same round with a sixteen-facet band. For more sparkle still, DG-Vitruvio Diamond reaches 98.
T105 Round Brilliant Diamond: questions
Is a T105 round brilliant better than a T73?
For sparkle and leakage, slightly: Scintillation 90 against 80, leakage 1% against 2%. When tipped it keeps less light, 87 against 92.
Why does the T105 have no girdle band?
It follows the T57, where crown and pavilion meet at a knife edge. Our model keeps that edge, and at 59.3% deep it is shallower than the T73's 61.7%.
How many facets does a T105 have?
105: the T57's plan plus star halves on the crown and extra rows of halves on the pavilion.
What does a 6.5 mm T105 diamond weigh?
About 0.92 ct, from the measured volume of the knife-edge model.
Get the T105 Round Brilliant Cut files
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T105 Round Brilliant Cut 3D files
The T105 Round Brilliant Cut as exact geometry: 105 planar facets, real-world scale, ready for CAD,
rendering, printing and casting.
