Triangle Cut Diamond: Pros, Cons & Fire

The triangle is the three-sided cut with the fewest facets: a table, two crown tiers and three pavilion tiers on an equilateral outline. Our model has a 60.0% table, a 35.3° crown, a 41.76° pavilion and a depth of 55.4%.

Beside the T73 Round Brilliant in diamond, the triangle gains on fire and loses on scintillation, brilliance, leakage and face-up size. Tilt and symmetry are level.

Beside the other three-sided cuts it trails on light: the Trilliant Cut Diamond returns 78, the Trillion Cut Diamond 67.

Is a triangle cut diamond worth choosing? Pros and cons

Pros

More fire than a round 86 vs 78

Cons

The fewest flashes we measure 34 vs 80
Little more than half a round's light 53 vs 93
A quarter of the light leaks 25 vs 2
The smallest face for its weight we measure 89 vs 100

Compared 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 T73

At a glance: the Triangle Cut 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 3, level on 1, behind on 4.

Global71, the comparison 90, difference −19
Brilliance53, the comparison 93, difference −40
Fire86, the comparison 78, difference +8
Scintillation34, the comparison 80, difference −46
Spread104, the comparison 100, difference +4
Symmetry100, the comparison 100, difference 0
Shape-norm69, the comparison 100, difference −31
Tilt94, the comparison 92, 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

What diamond gains in a triangle cut

More fire than a round

Fire 86 against 78 for the T73 Round Brilliant in diamond: 8 points higher

A plan this simple has large facets, and more of the light that returns is split into colour than in the T73. The trillion, with bowed sides, shows a point more.

Triangle cut in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 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.

T73 round brilliant in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 78) — 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.

Try it yourself: See the fire in the 3D Gemstone Simulator

The triangle's costs in diamond

The fewest flashes we measure

Scintillation 34 against 80 for the T73 Round Brilliant in diamond: 46 points lower

No cut we measure has fewer facets, and none scores lower for scintillation, which is read from the facets that reach the surface. Expect a few large flashes, not a glitter.

Triangle Cut · 19 facets · Scintillation 34

T73 Round Brilliant · 73 facets · Scintillation 80

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.

What helps: The facet plan sets this. For three sides with far more sparkle, the Trillion Cut Diamond scores 80 and the Trilliant Cut Diamond 79.

Try it yourself: Compare the Scintillation spoke in the Cut Performance Wheel

Little more than half a round's light

Brilliance 53 against 93 for the T73 Round Brilliant in diamond: 40 points lower

Its pavilion is steep, 41.76° against diamond's 38.9° guide minimum, so the loss is not a shallow-pavilion problem. With three tiers below the girdle, there are few surfaces to send light back up.

Triangle cut in diamond face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 53) — 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.

T73 round brilliant in diamond face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 93) — 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: The Trilliant Cut Diamond returns 78, the most of the three-sided cuts we measure. Steepening is not what our data suggests: the pavilion already clears the guide minimum.

Try it yourself: Open this Light Return map in the simulator

A quarter of the light leaks

Leakage 25 against 2 for the T73 Round Brilliant in diamond: 23 points higher

The triangle loses 25% of its light out of the back in our census, where the T73 loses 2%. That ties it with the emerald cut; the two other three-sided cuts lose far less.

Triangle cut in diamond tilted 0 degrees: Light Return map, 26% of the face leaking — 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.

Triangle cut in diamond tilted 10 degrees: Light Return map, 29% of the face leaking — 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: Size does not change the share. The Trilliant Cut Diamond loses 11%, the Trillion Cut Diamond 13%.

Try it yourself: Tilt it yourself in the simulator's light map

The smallest face for its weight we measure

Face-up size 89 against 100 for the T73 Round Brilliant in diamond (T73 = 100): 11% less face-up area for the same weight

Drawn at the same weight beside the T73, the triangle covers less area: the lowest Face-up size of any cut we measure in diamond. The trillion, with bowed sides, faces up level with the T73.

Triangle Cut · 8.12 x 7.03 mm at 1.00 ct · Face-up size 89

T73 Round Brilliant · 6.48 mm at 1.00 ct · Face-up size 100

Both stones weigh 1.00 ct in diamond and are drawn to the same scale in millimetres, 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 Trillion Cut Diamond faces up at 100 for its weight. Otherwise, compare stones by millimetres rather than carats.

Try it yourself: See its size at 1.00 ct in diamond in the 3D Gemstone Simulator

Who a triangle cut diamond suits

Choose the triangle for bold, simple flashes of colour in a geometric setting, and as a first faceting design: with 19 facets there is little to go wrong.

For a three-sided diamond that returns more light, the Trilliant Cut Diamond; for more sparkle and more face for the weight, the Trillion Cut Diamond.

Triangle Cut Diamond: questions

Is a triangle cut diamond sparkly?

Less than any cut we measure: Scintillation 34 against 80 for the T73, from 19 facets.

Triangle, trillion or trilliant cut diamond?

For light, the trilliant (78); for face-up size, the trillion (100). All three beat the T73 on fire, the trillion most (87), but each from far less light than a round. The triangle trails both on brilliance, leakage and sparkle.

Does a triangle diamond look small for its weight?

Yes, more than any other cut we measure in diamond: Face-up size 89 against 100 for the T73.

Is a triangle a good first cut for a new faceter?

It has 19 facets in two crown tiers and three pavilion tiers, so there are few angles to set.

Get the Triangle Cut files

6 formatsMillimetresWatertight

Triangle Cut 3D files

The Triangle Cut as exact geometry: 19 planar facets, real-world scale, ready for CAD, rendering, printing and casting.

STEPExact faceted solid for CAD
3DMRhino, closed mesh on its own layer
STLWatertight mesh for printing and casting
OBJMesh for modelling and rendering
FBXBlender, 3ds Max, Maya, Cinema 4D, Unity, Unreal
GLBWeb, AR and quick previews

€9.99 · Personal useBuy the 3D files

GemCad96 index

Triangle Cut cutting files

The Triangle Cut as a faceting design: 16 + 3 girdles = 19 facets, 96 index, 3-fold symmetry, ready for the machine.

.ascGemCad design file, 96 index gear
.csvTier table: angles, indices and cutting order
DiagramPrintable faceting diagram

€9.99 · Personal useBuy the cutting files

Questions before you buy? Email us.

More gemstones and cuts

Diamond: optical properties and the top ten cuts · The Triangle Cut: specifications, model and files

Triangle Cut Diamond: more fire than a round, with the fewest facets we measure