Old Single Cut Emerald: lighter in weight than diamond, and the weakest pairing on these pages

Brilliance 17 · Fire 32 · Scintillation 44 · in our census, where the T73 scores 78 · 39 · 80 in emerald

Twenty-six facets and a steep pavilion, in a stone with a 39.4° critical angle: three-quarters of the light passes straight through.

See it in the simulatorGet the files
The Old Single Cut in emerald, rendered at an angle in our 3D Gemstone Simulator under studio light
Rendered in our 3D Gemstone Simulator from the Old Single Cut model, 1.00 ct, studio light.

Old Single Cut Emerald

The single cut is an octahedron with its top sawn off and its corners bevelled: one crown angle, one pavilion angle. Our model has a 57.5% table, a 40.0° crown and a 48.48° pavilion, 67.5% deep.

In diamond this plan returns 72. Emerald's refractive index is only about 1.58, and the census shows the result: Brilliance 17, the lowest of any page we have written for this stone. The pavilion is far above the 39.4° guide minimum, so a shallow pavilion is not the cause; with so few large facets, light gets few chances to turn back up.

Can an emerald work as an Old Single cut? Pros and cons

Pros

Cons

Compared with the T73 Round Brilliant in emerald and with the Old Single Cut 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 Old Single 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.

Performance wheel: Old Single Cut in emerald, against the T73 Round Brilliant in emerald as an outline. Solid white marks where it reaches further, hatching where it falls short. The scores are listed below.50100Global−28Brilliance−61Fire−7Scintillation−36Spread−3Symmetry0Shape-norm−66Tilt+23

Against the T73 Round Brilliant in emerald: ahead on 1, level on 1, behind on 6.

  • Global45, the comparison 73, difference −28
  • Brilliance17, the comparison 78, difference −61
  • Fire32, the comparison 39, difference −7
  • Scintillation44, the comparison 80, difference −36
  • Spread97, the comparison 100, difference −3
  • Symmetry100, the comparison 100, difference 0
  • Shape-norm18, the comparison 84, difference −66
  • Tilt100, the comparison 77, difference +23
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 an Old Single cut

Lighter than an eight-cut diamond

0.81 ct at 6.5 mm, against 1.05 ct for the same cut in diamond (−23%)

The single cut is deep, 67.5%, so it is a heavy stone for its width; emerald lightens it. At 6.5 mm it is 0.81 ct, against 1.05 ct in diamond.

Emerald0.81 ctDiamond1.05 ct
A Old Single 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 Old Single Cut page

Why the Old Single fails in emerald

A small fraction of the T73's light

Brilliance 17 against 78 for the T73 Round Brilliant in emerald: 61 points lower

17 against 78: less than a quarter. The same cut in diamond returns 72, so this is the pairing failing, not the plan alone.

Old single cut in emerald face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 17)

Old Single Cut in emerald · Brilliance 17

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)

T73 Round Brilliant in emerald · 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.

What helps: In emerald, the Old European Cut Emerald keeps an antique round at 64; DG-M5 Emerald returns 90.

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

Three-quarters of the light leaks

Leakage 75 against 19 for the Old Single Cut in diamond: 56 points higher

75% of the light in our census leaves through the pavilion, about four times the diamond version's 19%.

Old Single Cut in emerald · Leakage 75

Old single cut in emerald tilted 0 degrees: Light Return map, 68% of the face leaking0° · 68% leak
Old single cut in emerald tilted 10 degrees: Light Return map, 68% of the face leaking10° · 68% leak
Old single cut in emerald tilted 20 degrees: Light Return map, 64% of the face leaking20° · 64% leak
Old single cut in emerald tilted 30 degrees: Light Return map, 56% of the face leaking30° · 56% leak

Old Single Cut in diamond · Leakage 19

Old single cut in diamond tilted 0 degrees: Light Return map, 24% of the face leaking0° · 24% leak
Old single cut in diamond tilted 10 degrees: Light Return map, 19% of the face leaking10° · 19% leak
Old single cut in diamond tilted 20 degrees: Light Return map, 27% of the face leaking20° · 27% leak
Old single cut in diamond tilted 30 degrees: Light Return map, 35% of the face leaking30° · 35% 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 steeper pavilion is not the answer: at 48.48° the mains are already about nine degrees past emerald's 39.4° guide minimum. A different plan is: the Old European Cut Emerald leaks 36%.

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

Little fire, from little light

Fire 32 against 84 for the Old Single Cut in diamond: 52 points lower

Fire depends on light coming back to the eye to be split. Here little comes back, and emerald splits it weakly: 32 against 84 for the diamond version.

Old single cut in emerald face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 32)

Old Single Cut in emerald · Fire 32

Old single cut in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 84)

Old Single Cut in diamond · Fire 84

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

Few, large flashes

Scintillation 44 against 80 for the T73 Round Brilliant in emerald: 36 points lower

With 26 facets against the T73's 73, the stone shows a slow, broad flash pattern; the score is the same in any stone.

Old Single Cut · 26 facets · Scintillation 44

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: Only more facets change this. An antique round with them: the Old European Cut Emerald, at 81.

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

Who an Old Single emerald suits

We would not cut an emerald as an Old Single for light. If the plan is wanted for a tiny accent stone, where the site's cut notes say the eight cut still serves, expect a dark, glassy face.

For an antique round in emerald, the Old European Cut Emerald; for a round with light, DG-M5 Emerald or the T73 Round Brilliant Emerald.

Old Single Cut Emerald: questions

Is the Old Single a good cut for emerald?

No, in our census: Brilliance 17 against 78 for the T73, and 75% of the light leaking through the pavilion.

Why does an Old Single emerald lose so much light?

Emerald reflects light inside the stone only when it meets a facet at more than 39.4° from the perpendicular. In this cut 75% gets out through the back; the same cut in diamond loses 19%.

Does an Old Single emerald keep its light when tilted?

It scores 100 for Tilt, the maximum, because Tilt measures the share of its own light it keeps, and it has little to keep: Brilliance 17.

Get the Old Single Cut files

6 formatsMillimetresWatertight

Old Single Cut 3D files

The Old Single Cut as exact geometry: 26 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

Old Single Cut cutting files

The Old Single Cut as a faceting design: 18 + 8 girdles = 26 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 Old Single Cut: specifications, model and files

Other cuts in emerald

The Old Single Cut in other gemstones