Portuguese Bird's Nest Cut Emerald: sparkle level with the highest we measure in this stone, and lighter in weight than diamond

Brilliance 42 · Fire 2 · Scintillation 98 · in our census, where the T73 scores 78 · 39 · 80 in emerald

177 facets woven in sixteen-fold tiers. In emerald its Scintillation, 98, is level with the highest we measure; its Fire is 2, and 58% of its light leaks.

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

Portuguese Bird's Nest Cut Emerald

The Portuguese cut stacks five crown tiers over five pavilion tiers, each offset half an index step so the facets interlock into a woven nest. The model we trace has a 48.9% table, a low 26.0° crown and a 38.0° pavilion, 63.1% deep overall.

In diamond it returns 85 and leaks only 13%. Emerald roughly halves that light. Its pavilion at 38.0° sits just under emerald's 39.4° guide minimum, and in our census 58% of the light leaks out of the back.

Its fire, 2, is the lowest of every cut we measure in emerald. The census records that; it does not explain it.

Portuguese cut emerald: does it work? Pros and cons

Pros

Cons

Compared with the T73 Round Brilliant in emerald and with the Portuguese Bird's Nest 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 Portuguese Bird's Nest 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: Portuguese Bird's Nest 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−18Brilliance−36Fire−37Scintillation+18Spread0Symmetry0Shape-norm−38Tilt+23

Against the T73 Round Brilliant in emerald: ahead on 2, level on 2, behind on 4.

  • Global55, the comparison 73, difference −18
  • Brilliance42, the comparison 78, difference −36
  • Fire2, the comparison 39, difference −37
  • Scintillation98, the comparison 80, difference +18
  • Spread100, the comparison 100, difference 0
  • Symmetry100, the comparison 100, difference 0
  • Shape-norm46, the comparison 84, difference −38
  • 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. 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 a Portuguese cut

Lighter than the diamond version

0.86 ct at 6.5 mm, against 1.11 ct for the same cut in diamond (−23%)

A 6.5 mm Portuguese cut comes to 0.86 ct in emerald and 1.11 ct in diamond: beryl is the lighter material, 2.72 against 3.52.

Emerald0.86 ctDiamond1.11 ct
A Portuguese Bird's Nest 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 Portuguese Bird's Nest Cut page

As fine a sparkle as any cut we measure in emerald

Scintillation 98 against 80 for the T73 Round Brilliant in emerald: 18 points higher

177 facets, more than twice the T73's 73, give Scintillation 98, level with DG-Miliano and DG-Vitruvio at the top of our emerald scores. The score follows the plan and is the same in diamond.

Portuguese Bird's Nest Cut · 177 facets · Scintillation 98

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 Portuguese cut emerald

Almost no fire

Fire 2 against 65 for the Portuguese Bird's Nest Cut in diamond: 63 points lower

2, against 65 for the same cut in diamond and 39 for the T73 in emerald: the lowest fire of any cut we measure in this stone.

Portuguese bird's nest cut in emerald face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 2)

Portuguese Bird's Nest Cut in emerald · Fire 2

Portuguese bird's nest cut in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 65)

Portuguese Bird's Nest Cut in diamond · Fire 65

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 the stone and the plan together. Among cuts that hold their light in emerald, DG-Anteros Emerald gives 52.

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

Over half the light leaks

Leakage 58 against 13 for the Portuguese Bird's Nest Cut in diamond: 45 points higher

58% in our census, against 13% for the Portuguese cut in diamond. Emerald needs a ray to strike a facet beyond 39.4° to turn it back, and a pavilion at 38.0° lets head-on light past.

Portuguese Bird's Nest Cut in emerald · Leakage 58

Portuguese bird's nest cut in emerald tilted 0 degrees: Light Return map, 66% of the face leaking0° · 66% leak
Portuguese bird's nest cut in emerald tilted 10 degrees: Light Return map, 54% of the face leaking10° · 54% leak
Portuguese bird's nest cut in emerald tilted 20 degrees: Light Return map, 44% of the face leaking20° · 44% leak
Portuguese bird's nest cut in emerald tilted 30 degrees: Light Return map, 42% of the face leaking30° · 42% leak

Portuguese Bird's Nest Cut in diamond · Leakage 13

Portuguese bird's nest cut in diamond tilted 0 degrees: Light Return map, 12% of the face leaking0° · 12% leak
Portuguese bird's nest cut in diamond tilted 10 degrees: Light Return map, 8% of the face leaking10° · 8% leak
Portuguese bird's nest cut in diamond tilted 20 degrees: Light Return map, 8% of the face leaking20° · 8% leak
Portuguese bird's nest cut in diamond tilted 30 degrees: Light Return map, 8% of the face leaking30° · 8% 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: We have not measured the Portuguese cut with a steeper pavilion, so we promise nothing from one. DG-Vitruvio Emerald matches its scintillation and leaks 22%.

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

About half the light of the diamond version

Brilliance 42 against 85 for the Portuguese Bird's Nest Cut in diamond: 43 points lower

42 against 85. The stone is the only thing that changes between the two figures, so this loss is emerald's, with this cut's angles.

Portuguese bird's nest cut in emerald face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 42)

Portuguese Bird's Nest Cut in emerald · Brilliance 42

Portuguese bird's nest cut in diamond face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 85)

Portuguese Bird's Nest Cut in diamond · Brilliance 85

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-Vitruvio Emerald returns 78 with the same top sparkle score; DG-M5 Emerald returns 90.

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

Who a Portuguese cut emerald suits

The Portuguese cut is a showpiece for the faceting machine, and in emerald it stays one for its pattern: sparkle level with the finest we measure, little light and next to no fire. Cut it for the craft, not for a lively stone.

If you want that level of sparkle with light behind it, DG-Vitruvio Emerald scores 98 for scintillation and returns 78. The Portuguese cut itself is a far stronger pairing in diamond.

Portuguese Bird's Nest Cut Emerald: questions

Is a Portuguese cut good for emerald?

For sparkle, yes: Scintillation 98. For light and fire, no: Brilliance 42 against 85 in diamond, Fire 2.

Why does a Portuguese cut emerald have so little fire?

Our census scores it 2, the lowest in emerald; the same cut in diamond scores 65. Emerald's dispersion is 0.014, but why so little of this plan's returned light is split into colour, the census does not say.

Portuguese cut or DG-Vitruvio for an emerald?

Scintillation is level, 98 and 98. DG-Vitruvio returns far more light (78 against 42), leaks less (22% against 58%) and has more fire (40 against 2).

How many facets does a Portuguese bird's nest cut have?

Our model has 177, in sixteen-fold tiers, against 73 on the T73 Round Brilliant.

Get the Portuguese Bird's Nest Cut files

6 formatsMillimetresWatertight

Portuguese Bird's Nest Cut 3D files

The Portuguese Bird's Nest Cut as exact geometry: 177 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

Portuguese Bird's Nest Cut cutting files

The Portuguese Bird's Nest Cut as a faceting design: 161 + 16 girdles = 177 facets, 96 index, 16-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

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Emerald: optical properties and the top ten cuts · The Portuguese Bird's Nest Cut: specifications, model and files

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