T73 Round Brilliant Emerald: Pros, Cons & Fire

On every other emerald page the T73 is the round we measure against. Here it is the subject, so it is set against the T57: the same 1919 proportions with a knife-edge girdle and 57 facets. The T73 adds sixteen girdle facets for 73 in all, at a 40.75° pavilion, 61.7% deep.

In emerald the two return the same light and leak the same share. Against the T73 in diamond, both fall well behind on light and fire.

So the page answers a narrow question: what does the girdle band buy in emerald? Finer sparkle, and nothing else we can measure. The cons are the distance from the diamond T73, and they belong to the stone.

Is a T73 round brilliant right for emerald? Pros and cons

Pros

Lighter than a diamond T73 0.78 vs 1.01 ct
More sparkle than the T57 80 vs 72

Cons

Half the fire of a diamond T73 39 vs 78
Over a fifth of the light leaks 22 vs 2
Less light than the diamond version 78 vs 93
Keeps less light when tilted 77 vs 92

Compared with the T57 Round Brilliant in emerald and 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 T57

At a glance: the T73 Round Brilliant in emerald (white) against the T57 Round Brilliant in emerald (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 emerald: ahead on 3, level on 3, behind on 2.

Global73, the comparison 72, difference +1
Brilliance78, the comparison 78, difference 0
Fire39, the comparison 40, difference −1
Scintillation80, the comparison 72, difference +8
Spread100, the comparison 101, difference −1
Symmetry100, the comparison 100, difference 0
Shape-norm84, the comparison 84, difference 0
Tilt77, the comparison 76, difference +1

Face-up light census, a different measure from the Cut Grading Tool; Spread and Shape-norm above 100 sit on the ring.

Open it in the Cut Performance Wheel

What emerald gains in a T73

Lighter than a diamond T73

0.78 ct at 6.5 mm, against 1.01 ct for the same cut in diamond (−23%)

Emerald's specific gravity, 2.72 against diamond's 3.52, makes the same 6.5 mm T73 0.78 ct rather than 1.01 ct.

A T73 Round Brilliant 6.5 mm across, weighed from the model's measured volume and each stone's specific gravity.

Try it yourself: Weights in all seven gemstones on the T73 Round Brilliant page

More sparkle than the T57

Scintillation 80 against 72 for the T57 Round Brilliant in emerald: 8 points higher

Scintillation counts the facet plan. The girdle band takes the T57's 57 facets to 73, and the score rises from 72 to 80 in any stone.

T73 Round Brilliant · 73 facets · Scintillation 80

T57 Round Brilliant · 57 facets · Scintillation 72

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.

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

Where the T73 falls short in emerald

Half the fire of a diamond T73

Fire 39 against 78 for the T73 Round Brilliant in diamond: 39 points lower

39 in emerald, 78 in diamond. The proportions are identical; the stone's dispersion, 0.014 against 0.044, makes the difference.

T73 round brilliant in emerald face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 39) — 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

Over a fifth of the light leaks

Leakage 22 against 2 for the T73 Round Brilliant in diamond: 20 points higher

Light inside emerald must meet a facet at more than 39.4° from its perpendicular to be reflected; in diamond, 24.4° is enough. So 22% leaks here and 2% in diamond, through the same pavilion.

T73 round brilliant in emerald tilted 0 degrees: Light Return map, 11% 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.

T73 round brilliant in emerald tilted 10 degrees: Light Return map, 34% 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: Steepening is not what the numbers support: the 40.75° pavilion is already above the 39.4° guide minimum. DG-M5 Emerald leaks 10%.

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

Less light than the diamond version

Brilliance 78 against 93 for the T73 Round Brilliant in diamond: 15 points lower

The 1919 angles were worked out for diamond. In emerald they return 78; our own DG-M5 returns 90 in the same stone.

T73 round brilliant in emerald face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 78) — 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: DG-M5 Emerald (90) and DG-Anteros Emerald (86) both return more light in emerald.

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

Keeps less light when tilted

Tilt 77 against 92 for the T73 Round Brilliant in diamond: 15 points lower

At 20° it holds 77 of its face-up light, against 92 in diamond. The T57, with its knife edge, is a point behind at 76: no real difference.

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

Who a T73 emerald suits

The T73 is a sound, conventional round for emerald, with a girdle a setter can seat. It is not the best round we measure in the stone: two of our own designs return more light.

For more light, DG-M5 Emerald or DG-Anteros Emerald. For the historical plan without the girdle band, the T57 Round Brilliant Emerald; for finer sparkle with the same light, DG-Vitruvio Emerald.

T73 Round Brilliant Emerald: questions

Is a round brilliant a good cut for emerald?

A reasonable one: the T73 returns 78 in emerald and leaks 22%. DG-M5 does better, at 90 and 10%.

T73 or T57 for an emerald?

The light is the same (78 against 78); the T73 sparkles more (80 against 72) and has a girdle to set.

Why does a round emerald have so little fire?

Emerald's dispersion is 0.014, under a third of diamond's. The T73 scores 39 for fire in emerald and 78 in diamond.

Get the T73 Round Brilliant Cut files

6 formatsMillimetresWatertight

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.

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

T73 Round Brilliant Cut cutting files

The T73 Round Brilliant Cut as a faceting design: 57 + 16 girdles = 73 facets, 96 index, 8-fold mirror-image 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

Emerald: optical properties and the top ten cuts · The T73 Round Brilliant: specifications, model and files

T73 Round Brilliant Emerald: finer sparkle than the T57, on the same proportions