Portuguese Bird's Nest Cut Amethyst: sparkle level with the highest we measure, from well over a hundred facets

Brilliance 37 · Fire 1 · Scintillation 98 · in our census, where the T73 scores 72 · 36 · 80 in amethyst

A woven nest of 177 facets gives amethyst as much sparkle as any cut we measure. In quartz 63% of its light leaves through the back, against 13% in diamond.

See it in the simulatorGet the files
The Portuguese Bird's Nest Cut in amethyst, 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 Amethyst

The Portuguese cut is sixteen-fold, with five crown tiers and five pavilion tiers, each offset half a step from the one above so the facets interlock. Our model has 177 facets, a 48.9% table, a low 26.0° crown and a 38.0° pavilion.

That pavilion sits a little under quartz's critical angle of 40.4°, so light coming straight down through the table can pass out of the back instead of reflecting. In diamond, whose critical angle is far smaller, the same model returns 85 and leaks 13%; in amethyst, 37 and 63%.

Its sparkle score follows the facet plan, so it reads the same in either stone. With DG-Miliano, this plan has the most facets of any cut we measure.

Is the Portuguese cut good for amethyst? Pros and cons

Pros

Cons

Compared with the T73 Round Brilliant in amethyst 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 amethyst (white) against the T73 Round Brilliant in amethyst (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 amethyst, against the T73 Round Brilliant in amethyst as an outline. Solid white marks where it reaches further, hatching where it falls short. The scores are listed below.50100Global−18Brilliance−35Fire−35Scintillation+18Spread0Symmetry0Shape-norm−37Tilt+20

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

  • Global52, the comparison 70, difference −18
  • Brilliance37, the comparison 72, difference −35
  • Fire1, the comparison 36, difference −35
  • Scintillation98, the comparison 80, difference +18
  • Spread100, the comparison 100, difference 0
  • Symmetry100, the comparison 100, difference 0
  • Shape-norm40, the comparison 77, difference −37
  • Tilt100, the comparison 80, difference +20
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 amethyst gains in a Portuguese Bird's Nest

Lighter than diamond

0.84 ct at 6.5 mm, against 1.11 ct for the same cut in diamond (−25%)

The same millimetres in amethyst weigh three quarters of the diamond version, 2.65 against 3.52 in specific gravity.

Amethyst0.84 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

Sparkle level with the best we measure

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

177 facets, interlocked in tiers, give our scintillation score more to count than the T73's 73. Only DG-Miliano and DG-Vitruvio match it in amethyst, and the diamond version scores the same.

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

What amethyst costs the Portuguese Bird's Nest

Almost no fire

Fire 1 against 65 for the Portuguese Bird's Nest Cut in diamond: 64 points lower

Quartz's dispersion of 0.013 is one reason, but every cut here shares it, and the census does not say why this plan falls so far below the rest. It is the lowest fire we measure in amethyst; the next lowest, the Peruzzi, scores 13.

Portuguese bird's nest cut in amethyst face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 1)

Portuguese Bird's Nest Cut in amethyst · Fire 1

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: For colour, look to another plan: of the cuts within ten points of the T73's brilliance in amethyst, DG-Anteros Amethyst carries the most fire, 54.

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

Most of the light leaks

Leakage 63 against 13 for the Portuguese Bird's Nest Cut in diamond: 50 points higher

Nearly five times the diamond's share leaves through the back. The picture's diamond strip shows how little grey diamond lets through, an eighth or less in every frame.

Portuguese Bird's Nest Cut in amethyst · Leakage 63

Portuguese bird's nest cut in amethyst tilted 0 degrees: Light Return map, 67% of the face leaking0° · 67% leak
Portuguese bird's nest cut in amethyst tilted 10 degrees: Light Return map, 58% of the face leaking10° · 58% leak
Portuguese bird's nest cut in amethyst tilted 20 degrees: Light Return map, 53% of the face leaking20° · 53% leak
Portuguese bird's nest cut in amethyst tilted 30 degrees: Light Return map, 48% of the face leaking30° · 48% 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: The pavilion sits under the 40.4° guide minimum for rounds, but we have not measured a steeper bird's nest and promise none. For a round that loses little, DG-M5 Amethyst leaks 15%.

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

Under half the diamond's light

Brilliance 37 against 85 for the Portuguese Bird's Nest Cut in diamond: 48 points lower

Light that the diamond version sends back from the pavilion passes through it in quartz. The T73 returns 72 in amethyst, so the bird's nest trails the round here too.

Portuguese bird's nest cut in amethyst face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 37)

Portuguese Bird's Nest Cut in amethyst · Brilliance 37

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: For a many-faceted round that stays bright in amethyst, DG-Vitruvio Amethyst matches this sparkle (98) with 71 brilliance.

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

Who a Portuguese cut amethyst suits

The bird's nest suits a cutter who wants a showpiece and a buyer who values sparkle over fire. In amethyst, expect a glittering stone that is darker than the same cut in diamond, with almost no colour play.

For the same sparkle with far more light, DG-Vitruvio Amethyst. If you want light above all, choose DG-M5 Amethyst.

Portuguese Bird's Nest Cut Amethyst: questions

Is the Portuguese cut good for amethyst?

For sparkle, yes: Scintillation 98, against 80 for the T73. It gives up light and nearly all its fire for it: Brilliance 37, Fire 1.

Why does a Portuguese cut amethyst show so little fire?

Our census scores it 1, the lowest we measure in amethyst. Quartz splits light weakly; the census does not give the rest of the reason.

How many facets does a Portuguese Bird's Nest have?

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

What does a 6.5 mm Portuguese cut amethyst weigh?

0.84 ct; in diamond it is 1.11 ct.

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

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