Octagon Cut Emerald: Pros, Cons & Light Return

Eight equal sides, a stepped crown and a pavilion in three tiers: our octagon has 49 facets, a 60.0% table and a 39.8° crown over a pavilion figure of 29.3°, and it stands 61.0% deep.

In emerald it returns 69, against 71 for the same octagon in diamond: one of the smallest gaps between the two stones that we measure. The Emerald Cut, Asscher, Emerald Square, baguette and rectangle all return less in emerald.

Three of its four cons are set against the diamond octagon, and the fourth, Scintillation, against the T73. Brilliance, 69 against 78 for the T73, also clears our margin, but we show only the four largest cons and it comes fifth, ahead of Face-up size (95 against 100).

How good is an octagon cut emerald? Pros and cons

Pros

Lighter than a diamond octagon 0.95 vs 1.23 ct

Cons

Much less fire than the diamond octagon 34 vs 76
Steadier than a round, not as steady as in diamond 83 vs 97
Fewer flashes than a round 66 vs 80
More leakage than in diamond 31 vs 18

Compared with the T73 Round Brilliant in emerald and with the Octagon 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 Octagon Cut 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 2, level on 2, behind on 4.

Global67, the comparison 73, difference −6
Brilliance69, the comparison 78, difference −9
Fire34, the comparison 39, difference −5
Scintillation66, the comparison 80, difference −14
Spread100, the comparison 100, difference 0
Symmetry100, the comparison 100, difference 0
Shape-norm90, the comparison 84, difference +6
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. 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 emerald gains in an octagon cut

Lighter than a diamond octagon

0.95 ct at 6.5 mm, against 1.23 ct for the same cut in diamond (−23%)

Six and a half millimetres across, our octagon weighs 0.95 ct in emerald and 1.23 ct in diamond. Of the two materials, beryl is the less dense, 2.72 against 3.52.

A Octagon Cut 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 Octagon Cut page

The catch with an octagon emerald

Much less fire than the diamond octagon

Fire 34 against 76 for the Octagon Cut in diamond: 42 points lower

34 against 76. The plan is identical, so the gap is the stone's. It sits a few points below the T73 in emerald as well, 39.

Octagon cut 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.

Octagon cut in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 76) — 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.

What helps: This is emerald. For more colour with light to match, DG-Anteros Emerald scores 52 at 86 brilliance, though as a round.

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

Steadier than a round, not as steady as in diamond

Tilt 83 against 97 for the Octagon Cut in diamond: 14 points lower

Tipped by 20°, the emerald octagon keeps 83 of its face-up light: more than the T73's 77 in emerald; of the cuts within 10 points of the T73's brilliance here, only the square brilliant keeps more, 85, and the T105 keeps as much, 83. The diamond octagon keeps 97.

Octagon cut in emerald tilted 0 degrees: Light Return map, 21% of the face leaking — 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.

Octagon cut in emerald tilted 10 degrees: Light Return map, 39% of the face leaking — 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.

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

Fewer flashes than a round

Scintillation 66 against 80 for the T73 Round Brilliant in emerald: 14 points lower

49 facets against 73: Scintillation 66 against 80. A stepped crown makes broad flashes rather than fine glitter, whatever the stone.

Octagon Cut · 49 facets · Scintillation 66

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: A finer plan raises it: the square brilliant scores 78 and the Cushion Cut Emerald 85.

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

More leakage than in diamond

Leakage 31 against 18 for the Octagon Cut in diamond: 13 points higher

31% against 18% for the diamond octagon, and 22% for the T73 in emerald. Even so, it is the lowest leakage of the step cuts we measure in emerald.

What helps: We have not measured a steeper octagon and promise nothing from one. For less leakage in emerald, DG-M5 Emerald loses 10%.

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

Who an octagon emerald suits

Of the step-cut outlines we measure in emerald, this is the one our numbers favour: the most light, the least leakage and a steady stone when tipped. It suits a geometric centre stone where emerald's colour should read clearly.

For more sparkle and still more light, a round such as DG-M5 Emerald. For a rectangular step cut, the Emerald Cut Emerald, with less light.

Octagon Cut Emerald: questions

Is an octagon cut good for emerald?

Yes, as step cuts go: Brilliance 69 against 78 for the T73, 31% leakage and Tilt 83.

Octagon or emerald cut for an emerald?

The octagon returns more light (69 against 58), leaks less (31% against 35%) and holds far steadier when tipped (83 against 52). The Emerald Cut faces up larger per carat and sparkles a little more.

Does an octagon emerald have fire?

Not much: 34, against 39 for the T73 in emerald and 76 for the octagon in diamond.

What does a 6.5 mm octagon emerald weigh?

0.95 ct by our model's volume; the diamond equivalent is 1.23 ct.

Get the Octagon Cut files

6 formatsMillimetresWatertight

Octagon Cut 3D files

The Octagon Cut as exact geometry: 49 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

Octagon Cut cutting files

The Octagon Cut as a faceting design: 41 + 8 girdles = 49 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 Octagon Cut: specifications, model and files

Octagon Cut Emerald: nearly the light of the diamond octagon, for less weight