Rendered in our 3D Gemstone Simulator from the Triangle Cut model, 1.00 ct, studio light.
Triangle Cut Sapphire
The triangle is an equilateral cut with two crown tiers over three pavilion tiers and no spare facets. Its 19 facets sit on a 41.76° pavilion under a 35.3° crown, with a 60.0% table and a total depth of 55.4%.
In sapphire no score counts as a pro, and six count as cons; the four largest are shown below.
It also faces up smaller for its weight than any other cut we measure: Face-up size 89, against 100 for the T73.
Is a triangle cut any good for sapphire? Pros and cons
Pros
None by our margins. It holds its light when tipped, but it has little light to hold.
Compared with the T73 Round Brilliant in sapphire and with the Triangle 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 Triangle Cut in sapphire (white) against the T73 Round Brilliant in sapphire (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 sapphire: ahead on 3, level on 1, behind on 4.
Global57, the comparison 79, difference −22
Brilliance33, the comparison 94, difference −61
Fire54, the comparison 37, difference +17
Scintillation34, the comparison 80, difference −46
Spread104, the comparison 100, difference +4
Symmetry100, the comparison 100, difference 0
Shape-norm43, the comparison 102, difference −59
Tilt100, the comparison 75, difference +25
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.
No score counts as a pro. Tipped 20°, it scores 100 for Tilt, the top of the scale, but Tilt is a share of the stone's own light, and at 33 brilliance that is a share of a small amount, so we do not count it. Fire, 54, is above the T73's 37 but far under the diamond triangle's 86. What it offers is the design: 19 facets, an approachable first cut for a new faceter.
The catch with a triangle sapphire
About a third of the T73's light
Brilliance 33 against 94 for the T73 Round Brilliant in sapphire: 61 points lower
Brilliance 33 against 94. In diamond the same triangle returns 53, so sapphire's lower refractive index costs it a good deal of light here.
Triangle Cut in sapphire · Brilliance 33
T73 Round Brilliant in sapphire · Brilliance 94
Red, green and blue = light returning to the eye; grey = light leaving through the pavilion. 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: For a three-sided sapphire with far more light, the Trilliant Cut Sapphire returns 86.
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.
Leakage 42 against 5 for the T73 Round Brilliant in sapphire: 37 points higher
The census sends 42% of the light out through the back of this triangle; for the T73 the figure is 5%. The pavilion is at 41.76°, above sapphire's 36.4° guide minimum; we have not measured a steeper triangle.
Triangle Cut in sapphire · Leakage 42
0° · 37% leak
10° · 33% leak
20° · 34% leak
30° · 28% leak
T73 Round Brilliant in sapphire · Leakage 5
0° · 1% leak
10° · 10% leak
20° · 29% leak
30° · 30% leak
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: A smaller stone leaks the same share, since the angles set it. The Trilliant Cut Sapphire leaks 12%.
Fire 54 against 86 for the Triangle Cut in diamond: 32 points lower
54 against 86 for the same triangle in diamond; the census changes the whole material, so it does not isolate dispersion. In sapphire it still beats the T73, 37.
Triangle Cut in sapphire · Fire 54
Triangle Cut in diamond · Fire 86
Look at the coloured flashes: those are fire. Same light, same size, same face-up angle; rendered by our 3D Gemstone Simulator from each cut's own model.
The triangle suits a first faceting project and designs that want a crisp, simple three-sided stone.
For a triangle that is bright in sapphire, choose the Trilliant Cut Sapphire: more than twice the light, a fraction of the leakage, and more than twice the sparkle.
For curved sides and a larger face for its weight, the Trillion Cut Sapphire measures 100 for face-up size, though it returns less light than the trilliant.
Triangle Cut Sapphire: questions
Is a triangle cut good for sapphire?
Not for light: Brilliance 33 against 94 for the T73, with 42% leaking. It has only 19 facets.
Triangle or trilliant for a sapphire?
The trilliant, for light: 86 against 33, with 12% leakage against 42%. The triangle has slightly more fire, 54 against 52.
What does a 6.5 mm triangle sapphire weigh?
0.90 ct for our model, against 0.79 ct for the same triangle in diamond.
Get the Triangle Cut files
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Triangle Cut 3D files
The Triangle Cut as exact geometry: 19 planar facets, real-world scale, ready for CAD,
rendering, printing and casting.
