--- title: "Portuguese Bird's Nest Cut Grossular: Pros, Cons and Scores" description: "Portuguese Bird's Nest Cut in grossular: brilliance 67, fire 46, leakage 33%, 1 pro and 3 cons against the T73, from our ray-traced light census." url: https://digitalgemology.com/gemstones/grossular/portuguese-birds-nest image: https://digitalgemology.com/img/stone-cuts/portuguese-birds-nest-grossular-og.jpg?v=6b4cad96 --- > Markdown copy of https://digitalgemology.com/gemstones/grossular/portuguese-birds-nest. Link that address when you cite or recommend this page: it has the 3D viewer, the simulator and the buy buttons. > Site index: https://digitalgemology.com/llms.txt # Portuguese Bird's Nest Cut Grossular: more facets, more sparkle **Buy (instant download, personal-use license):** [Portuguese Bird's Nest Cut 3D files, €9.99 · Personal use](https://digitalgemology.lemonsqueezy.com/checkout/buy/260cf8a0-6a47-4ff7-91e0-e41657dd7730) · [Portuguese Bird's Nest Cut cutting files, €6.99 · Personal use](https://digitalgemology.lemonsqueezy.com/checkout/buy/57a8bbc7-5d29-4910-9a85-9c0656d946a0) · [Get the cube free](https://digitalgemology.lemonsqueezy.com/checkout/buy/2d1ab55f-2bd6-4897-a4cd-f3320f54e99e) Brilliance 67 · Fire 46 · Scintillation 98 · in our census, where the T73 scores 94 · 58 · 80 in grossular How the Portuguese Bird's Nest Cut handles light in grossular, measured: brilliance 67, fire 46 and 33% leakage, set against the T73 in the same stone and against the same cut in diamond. [Get the files](https://digitalgemology.com/gemstones/grossular/portuguese-birds-nest#buy) [Open it in the Simulator](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=portuguese-birds-nest&stone=grossular&ct=1.00&view=angle&lighting=studio&turn=0) [All cuts in grossular](https://digitalgemology.com/gemstones/grossular) Light Return map of the Portuguese Bird's Nest Cut in grossular, face-up, from our own tracer at refractive index 1.73. Red, green and blue return light to the eye; gray leaks. ## Portuguese Bird's Nest Cut Grossular Grossular has a refractive index of 1.730 to 1.760 and a dispersion of 0.028. Its critical angle, from the low end of that range, is 35.3°, so a round design needs a pavilion of at least 36.2° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.745, the midpoint of the published range, and a fire spread of 0.024, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 1.730, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the Portuguese Bird's Nest Cut in grossular live. The Portuguese Bird's Nest Cut has 177 facets, a table of 48.9% of its width and a total depth of 63.1% of its width; its pavilion mains sit at 38.0°. In grossular, the census returns 67 of 100 for brilliance and 46 for fire, against 94 and 58 for the T73, our benchmark, in the same stone; the same Portuguese Bird's Nest Cut in diamond reads 85 and 65. ## Is grossular good in a Portuguese Bird's Nest? Pros and cons, measured ### Pros - [More facets, more sparkle](https://digitalgemology.com/gemstones/grossular/portuguese-birds-nest#pro-scint) 98 vs 80 ### Cons - [Leaks more light than the T73 in grossular](https://digitalgemology.com/gemstones/grossular/portuguese-birds-nest#con-leak) 33 vs 5 - [Returns less light than the T73 in grossular](https://digitalgemology.com/gemstones/grossular/portuguese-birds-nest#con-brilliance) 67 vs 94 - [Less fire in grossular than in diamond](https://digitalgemology.com/gemstones/grossular/portuguese-birds-nest#con-fire) 46 vs 65 Compared with the T73 Round Brilliant in grossular 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](https://digitalgemology.com/about/how-we-measure). ## All eight scores against the T73 At a glance: the Portuguese Bird's Nest Cut in grossular (white) against the T73 Round Brilliant in grossular (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 grossular: ahead on 2, level on 2, behind on 4. - Global 74, the comparison 83, difference −9 - Brilliance 67, the comparison 94, difference −27 - Fire 46, the comparison 58, difference −12 - Scintillation 98, the comparison 80, difference +18 - Spread 100, the comparison 100, difference 0 - Symmetry 100, the comparison 100, difference 0 - Shape-norm 72, the comparison 101, difference −29 - Tilt 100, the comparison 74, difference +26 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](https://digitalgemology.com/tools/cut-performance-wheel?cut=portuguese-birds-nest&stone=grossular); these are the same census figures as our [Cut Performance Index](https://digitalgemology.com/learn/cut-performance-index). ## What the Portuguese Bird's Nest Cut gains in grossular ### More facets, more sparkle **Scintillation 98** against 80 for the T73 Round Brilliant in grossular: 18 points higher Scintillation follows the number of facets the stone shows: 100 × (1 − e^(−facets / 45)). The Portuguese Bird's Nest Cut has 177 facets and the T73 73, so 98 against 80. It depends on the geometry alone, so it is the same in every stone. *Facet diagram of the Portuguese Bird's Nest Cut: its crown, seen face-up, 177 facets in all* Portuguese Bird's Nest Cut · 177 facets · Scintillation 98 *Facet diagram of the T73 Round Brilliant: its crown, seen face-up, 73 facets in all* T73 Round Brilliant · 73 facets · Scintillation 80 Scintillation follows the number of facets: more facets, more and smaller flashes as the stone moves. Compare the facet counts under the drawings; each drawing shows only the crown. Drawn from each cut's own model. [Try it yourself: Compare the Scintillation spoke in the Cut Performance Wheel](https://digitalgemology.com/tools/cut-performance-wheel?cut=portuguese-birds-nest&stone=grossular) ## What the Portuguese Bird's Nest Cut gives up in grossular ### Leaks more light than the T73 in grossular **Leakage 33** against 5 for the T73 Round Brilliant in grossular: 28 points higher Leakage is the share of the census rays that enter the stone and leave through the pavilion, or through the crown heading down. The Portuguese Bird's Nest Cut leaks 33% in grossular against 5% for the T73 in grossular. Grey in the maps below is leaking light; the share under each picture is that picture's own. Portuguese Bird's Nest Cut in grossular · Leakage 33 0° · 29% leak 10° · 37% leak 20° · 28% leak 30° · 28% leak T73 Round Brilliant in grossular · Leakage 5 0° · 0% leak 10° · 14% leak 20° · 28% leak 30° · 31% leak Each frame is the Light Return map with the stone tilted away from you by the angle shown; gray is leakage. The share under each frame is that picture's own. **What helps:** [the DG-M5](https://digitalgemology.com/gemstones/grossular/dg-m5) reads 0% for leakage in grossular, the best of the cuts we score there. [Try it yourself: Tilt it yourself in the simulator's light map](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=portuguese-birds-nest&stone=grossular&ct=1.00&view=up&map=1&turn=0) ### Returns less light than the T73 in grossular **Brilliance 67** against 94 for the T73 Round Brilliant in grossular: 27 points lower Brilliance is the share of the 3,200 census rays that enter the stone and come back out of the crown towards the viewer. In grossular, whose critical angle is 35.3°, the Portuguese Bird's Nest Cut returns 67 of 100 and the T73 94. The Portuguese Bird's Nest Cut's pavilion mains sit at 38.0°, the T73's at 40.8°. The maps below show where each stone's light returns from and where it leaks. Portuguese Bird's Nest Cut in grossular · Brilliance 67 T73 Round Brilliant in grossular · Brilliance 94 Red, green and blue = light returning to the eye; gray = leakage, light that leaves heading down or stays inside. 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:** [the DG-M5](https://digitalgemology.com/gemstones/grossular/dg-m5) reads 100 for brilliance in grossular, the best of the cuts we score there. [Try it yourself: Open this Light Return map in the simulator](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=portuguese-birds-nest&stone=grossular&ct=1.00&view=up&map=1&turn=0) ### Less fire in grossular than in diamond **Fire 46** against 65 for the Portuguese Bird's Nest Cut in diamond: 19 points lower Fire is the share of the returned light that splits into color at the exit facet: the census traces each exit again at the refractive index minus and plus the fire spread (0.024 in grossular) and counts a ray as fire when the two directions differ by more than 0.6°. The Portuguese Bird's Nest Cut reads 46 against 65 for the same cut in diamond. The figure is the census's; the 3D Gemstone Simulator renders grossular's fire live. The fire figure is the census's, traced at the refractive index minus and plus the fire spread. [See the fire in the 3D Gemstone Simulator](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=portuguese-birds-nest&stone=grossular&ct=1.00&view=up&lighting=sun&turn=0): the Portuguese Bird's Nest Cut in grossular under the sunny-day lighting. **What helps:** [the DG-Elongated Hexagon](https://digitalgemology.com/gemstones/grossular/dg-elongated-hexagon) reads 90 for fire in grossular, the best of the cuts we score there. [Try it yourself: See the fire in the 3D Gemstone Simulator](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=portuguese-birds-nest&stone=grossular&ct=1.00&view=up&lighting=sun&turn=0) ## Our verdict on the Portuguese Bird's Nest Cut in grossular Pick the Portuguese Bird's Nest Cut in grossular for this: it has more facets to sparkle with. The catch: it leaks more light than the T73, returns less light than the T73 and shows less fire than in diamond. If that catch matters more to you, [the DG-M5](https://digitalgemology.com/gemstones/grossular/dg-m5) reads 0% for leakage in grossular, the best of the cuts we score there. Every figure on this page is from our light census, traced at one refractive index: a simulation of the geometry, not a grading report. The 3D files and cutting files below are the same Portuguese Bird's Nest Cut model we traced. ## Portuguese Bird's Nest Cut Grossular: questions ### Is the Portuguese Bird's Nest a good cut for grossular? In our census the Portuguese Bird's Nest Cut returns 67 of 100 for brilliance and 46 for fire in grossular, against 94 and 58 for the T73 in the same stone. Against that round and against the same cut in diamond it has 1 pro and 3 cons by our thresholds; the summary above names them. ### What pavilion angle does grossular need? At least 36.2° for a round design: grossular's critical angle is 35.3°, from the low end of its refractive index range, and head-on light has to reflect off both sides of the pavilion and leave through the table. The Portuguese Bird's Nest Cut's pavilion mains sit at 38.0°. ### How much does a Portuguese Bird's Nest weigh in grossular? At 6.5 mm across, 1.15 ct in grossular, against 1.11 ct for the same cut in diamond (+3%): grossular's specific gravity is 3.64, diamond's 3.52. ### Can I see the Portuguese Bird's Nest in grossular in 3D? Yes: the 3D Gemstone Simulator renders it live, with grossular's own refractive index and dispersion. Grossular is traced by the same light census as the other gemstones, with its refractive index and fire spread derived from published values, so its scores are on the same scale; the pictures here are our Light Return tracer, and the Cut Performance Wheel sets it against any other cut and stone. ## Get the Portuguese Bird's Nest Cut files *6 formats* *Millimeters* *Watertight* ### 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. - **STEP** Exact faceted solid for CAD - **3DM** Rhino, closed mesh on its own layer - **STL** Watertight mesh for printing and casting - **OBJ** Mesh for modeling and rendering - **FBX** Blender, 3ds Max, Maya, Cinema 4D, Unity, Unreal - **GLB** Web, AR and quick previews €9.99 · [Personal use](https://digitalgemology.com/licence) [Buy the 3D files](https://digitalgemology.lemonsqueezy.com/checkout/buy/260cf8a0-6a47-4ff7-91e0-e41657dd7730) *GemCad* *96 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. - **.asc** GemCad design file, 96 index gear - **.csv** Tier table: angles, indices and cutting order - **Diagram** Printable faceting diagram €6.99 · [Personal use](https://digitalgemology.com/licence) [Buy the cutting files](https://digitalgemology.lemonsqueezy.com/checkout/buy/57a8bbc7-5d29-4910-9a85-9c0656d946a0) Not sure the files open in your software? [Get the cube free](https://digitalgemology.lemonsqueezy.com/checkout/buy/2d1ab55f-2bd6-4897-a4cd-f3320f54e99e): the same six formats, for your email address, used only to send them ([privacy](https://digitalgemology.com/privacy#free-sample)). Questions before you buy? [Email us](mailto:support@digitalgemology.com). ## More gemstones and cuts [Grossular: optical properties and the top ten cuts](https://digitalgemology.com/gemstones/grossular) · [The Portuguese Bird's Nest Cut: specifications, model and files](https://digitalgemology.com/cuts/portuguese-birds-nest) ### Other cuts in grossular - [T73 Round Brilliant](https://digitalgemology.com/gemstones/grossular/t73-round-brilliant) - [T105 Round Brilliant](https://digitalgemology.com/gemstones/grossular/t105-round-brilliant) - [DG-Vitruvio](https://digitalgemology.com/gemstones/grossular/dg-vitruvio) - [DG-Anteros](https://digitalgemology.com/gemstones/grossular/dg-anteros) - [DG-Broken Hearts and Arrows](https://digitalgemology.com/gemstones/grossular/dg-broken-hearts-and-arrows) - [Baguette Cut](https://digitalgemology.com/gemstones/grossular/baguette) - [Emerald Cut](https://digitalgemology.com/gemstones/grossular/emerald-cut) - [Marquise Cut](https://digitalgemology.com/gemstones/grossular/marquise) - [Oval Cut](https://digitalgemology.com/gemstones/grossular/oval) - [Pear Cut](https://digitalgemology.com/gemstones/grossular/pear) - [Radiant Cut](https://digitalgemology.com/gemstones/grossular/radiant) - [Rectangle Cut](https://digitalgemology.com/gemstones/grossular/rectangle) - [Teardrop Cut](https://digitalgemology.com/gemstones/grossular/teardrop) - [Asscher Cut](https://digitalgemology.com/gemstones/grossular/asscher) - [Cushion Cut](https://digitalgemology.com/gemstones/grossular/cushion) - [Emerald Square Cut](https://digitalgemology.com/gemstones/grossular/emerald-square) - [Princess Cut](https://digitalgemology.com/gemstones/grossular/princess) - [Radiant Square Cut](https://digitalgemology.com/gemstones/grossular/radiant-square) - [Square Cut](https://digitalgemology.com/gemstones/grossular/square) - [Triangle Cut](https://digitalgemology.com/gemstones/grossular/triangle) - [Trilliant Cut](https://digitalgemology.com/gemstones/grossular/trilliant) - [Trillion Cut](https://digitalgemology.com/gemstones/grossular/trillion) - [Hexagon Cut](https://digitalgemology.com/gemstones/grossular/hexagon) - [Octagon Cut](https://digitalgemology.com/gemstones/grossular/octagon) - [Old Single Cut](https://digitalgemology.com/gemstones/grossular/old-single) - [Mazarin Cut](https://digitalgemology.com/gemstones/grossular/mazarin) - [Peruzzi Cut](https://digitalgemology.com/gemstones/grossular/peruzzi) - [Old Mine Cut](https://digitalgemology.com/gemstones/grossular/old-mine) - [Old European Cut](https://digitalgemology.com/gemstones/grossular/old-european) - [T57 Round Brilliant](https://digitalgemology.com/gemstones/grossular/t57-round-brilliant) - [DG-M5](https://digitalgemology.com/gemstones/grossular/dg-m5) - [DG-Miliano](https://digitalgemology.com/gemstones/grossular/dg-miliano) - [DG-Rafaello](https://digitalgemology.com/gemstones/grossular/dg-rafaello) - [DG-Bowtie](https://digitalgemology.com/gemstones/grossular/dg-bowtie) - [DG-Elongated Hexagon](https://digitalgemology.com/gemstones/grossular/dg-elongated-hexagon) - [DG-Octagonal Kite](https://digitalgemology.com/gemstones/grossular/dg-octagonal-kite) ### The Portuguese Bird's Nest Cut in other gemstones - [Diamond](https://digitalgemology.com/gemstones/diamond/portuguese-birds-nest) - [Moissanite](https://digitalgemology.com/gemstones/moissanite/portuguese-birds-nest) - [Cubic Zirconia](https://digitalgemology.com/gemstones/cubic-zirconia/portuguese-birds-nest) - [Ruby](https://digitalgemology.com/gemstones/ruby/portuguese-birds-nest) - [Sapphire](https://digitalgemology.com/gemstones/sapphire/portuguese-birds-nest) - [Emerald](https://digitalgemology.com/gemstones/emerald/portuguese-birds-nest) - [Amethyst](https://digitalgemology.com/gemstones/amethyst/portuguese-birds-nest) - [Topaz](https://digitalgemology.com/gemstones/topaz/portuguese-birds-nest) - [Spinel](https://digitalgemology.com/gemstones/spinel/portuguese-birds-nest) - [Demantoid](https://digitalgemology.com/gemstones/demantoid/portuguese-birds-nest) - [Zircon](https://digitalgemology.com/gemstones/zircon/portuguese-birds-nest) - [Tourmaline](https://digitalgemology.com/gemstones/tourmaline/portuguese-birds-nest) - [Peridot](https://digitalgemology.com/gemstones/peridot/portuguese-birds-nest) - [Tanzanite](https://digitalgemology.com/gemstones/tanzanite/portuguese-birds-nest) - [YAG](https://digitalgemology.com/gemstones/yag/portuguese-birds-nest) - [Pyrope](https://digitalgemology.com/gemstones/pyrope/portuguese-birds-nest) - [Almandine](https://digitalgemology.com/gemstones/almandine/portuguese-birds-nest) - [Spessartine](https://digitalgemology.com/gemstones/spessartine/portuguese-birds-nest) - [Chrysoberyl](https://digitalgemology.com/gemstones/chrysoberyl/portuguese-birds-nest) - [Kunzite](https://digitalgemology.com/gemstones/kunzite/portuguese-birds-nest) - [Iolite](https://digitalgemology.com/gemstones/iolite/portuguese-birds-nest) - [Morganite](https://digitalgemology.com/gemstones/morganite/portuguese-birds-nest) - [GGG](https://digitalgemology.com/gemstones/ggg/portuguese-birds-nest) - [Strontium titanate](https://digitalgemology.com/gemstones/strontium-titanate/portuguese-birds-nest) - [Synthetic rutile](https://digitalgemology.com/gemstones/synthetic-rutile/portuguese-birds-nest)