T105 Round Brilliant Emerald: Pros, Cons & Leakage

The T105 keeps the 1919 main angles and divides the plan more finely: eight star halves on the crown, three rows of lower halves on the pavilion, and a knife-edge girdle. Our model has 105 facets and a 40.75° pavilion, and is 59.3% deep.

In diamond it nearly matches the best rounds for light, 95. In emerald it falls to 71, below the T73's 78, and leaks 29% of the light. Why the finer pavilion costs light in emerald and not in diamond, our census does not say; it measures that it does.

Should an emerald be cut as a T105? Pros and cons

Pros

Lighter than a diamond of the same width 0.71 vs 0.92 ct
More sparkle than the T73 90 vs 80

Cons

Much less fire than in diamond 34 vs 77
Nearly three in ten rays leak 29 vs 1
Much less light than in diamond 71 vs 95
Slightly less steady when tilted than in diamond 83 vs 87

Compared with the T73 Round Brilliant in emerald and with the T105 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 emerald (white) against the T73 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 T73 Round Brilliant in emerald: ahead on 3, level on 1, behind on 4.

Global70, the comparison 73, difference −3
Brilliance71, the comparison 78, difference −7
Fire34, the comparison 39, difference −5
Scintillation90, the comparison 80, difference +10
Spread101, the comparison 100, difference +1
Symmetry100, the comparison 100, difference 0
Shape-norm77, the comparison 84, difference −7
Tilt83, the comparison 77, difference +6

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 T105

Lighter than a diamond of the same width

0.71 ct at 6.5 mm, against 0.92 ct for the same cut in diamond (−23%)

0.71 ct for a 6.5 mm stone in emerald, 0.92 ct in diamond. Beryl's lower density does all the work.

A T105 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 T105 Round Brilliant page

More sparkle than the T73

Scintillation 90 against 80 for the T73 Round Brilliant in emerald: 10 points higher

Three rows of lower halves and the crown's star halves give 105 facets against 73. Our scintillation score follows the facet plan, so the gain holds in any stone.

T105 Round Brilliant · 105 facets · Scintillation 90

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.

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

The catch with a T105 emerald

Much less fire than in diamond

Fire 34 against 77 for the T105 Round Brilliant in diamond: 43 points lower

Fire 34 against 77. Emerald's dispersion caps the colour, and the T105 also scores a little below the T73 in emerald, 39.

T105 round brilliant in emerald face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 34) — 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.

T105 round brilliant in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 77) — 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

Nearly three in ten rays leak

Leakage 29 against 1 for the T105 Round Brilliant in diamond: 28 points higher

The census sends 29% of the light out through the pavilion, against 1% for the diamond version: the largest leak gap among the T-series rounds in emerald.

T105 round brilliant in emerald tilted 0 degrees: Light Return map, 20% 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.

T105 round brilliant in emerald tilted 10 degrees: Light Return map, 35% 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: The pavilion mains are at 40.75°, above emerald's 39.4° guide minimum, so a steeper pavilion is not the remedy our data supports. A different round is: DG-Anteros Emerald leaks 14%.

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

Much less light than in diamond

Brilliance 71 against 95 for the T105 Round Brilliant in diamond: 24 points lower

71 here against 95 in diamond, the steepest drop of the three T-series rounds.

T105 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 71) — 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.

T105 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 95) — 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: With fewer facets and a girdle band, the T73 Round Brilliant Emerald returns 78; DG-M5 Emerald returns 90.

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

Slightly less steady when tilted than in diamond

Tilt 83 against 87 for the T105 Round Brilliant in diamond: 4 points lower

Tipped 20°, it keeps 83 of its face-up light; in diamond, 87. That is a small gap, and above the T73's 77 in emerald.

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

Who a T105 emerald suits

Choose the T105 in emerald for its finer sparkle and the period plan, and set it to protect the knife edge. Expect less light than a T73.

If light matters more than sparkle, DG-M5 Emerald or the T73 Round Brilliant Emerald. For fine sparkle without the light cost, DG-Vitruvio Emerald scores 98 at 78 brilliance.

T105 Round Brilliant Emerald: questions

T105 or T73 for an emerald?

The T73 returns more light (78 against 71) and leaks less (22% against 29%); the T105 sparkles more (90 against 80).

Does a T105 emerald need a protective setting?

Its crown and pavilion meet at a knife edge with no girdle band, and emerald is 7.5 to 8 on the Mohs scale, so a bezel or a protective rim is sensible.

How much light does a T105 emerald leak?

29% in our census, against 22% for the T73 in emerald and 1% for the T105 in diamond.

Get the T105 Round Brilliant Cut files

6 formatsMillimetresWatertight

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.

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

T105 Round Brilliant Cut cutting files

The T105 Round Brilliant Cut as a faceting design: 105 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 T105 Round Brilliant: specifications, model and files

T105 Round Brilliant Emerald: more sparkle than the T73, from extra pavilion tiers