--- title: "Octagon Cut GGG: Pros, Cons and Scores" description: "Octagon Cut in GGG: brilliance 75, fire 69, leakage 21%, 1 pro and 4 cons against the T73, from our ray-traced light census." url: https://digitalgemology.com/gemstones/ggg/octagon image: https://digitalgemology.com/img/stone-cuts/octagon-ggg-og.jpg?v=e4ce53d3 --- > Markdown copy of https://digitalgemology.com/gemstones/ggg/octagon. 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 # Octagon Cut GGG: holds its light better in GGG than in diamond **Buy (instant download, personal-use license):** [Octagon Cut 3D files, €9.99 · Personal use](https://digitalgemology.lemonsqueezy.com/checkout/buy/26baac35-16bd-4143-97ba-9eeb7fd4da11) · [Octagon Cut cutting files, €6.99 · Personal use](https://digitalgemology.lemonsqueezy.com/checkout/buy/390b595d-894b-4e34-be35-57f44d569591) · [Buy the bundle](https://digitalgemology.lemonsqueezy.com/checkout/buy/9170b0c0-5357-490e-b6ef-3ce4f7fcd282?checkout%5Bdiscount_code%5D=BUNDLE25) · [Get the cube free](https://digitalgemology.lemonsqueezy.com/checkout/buy/2d1ab55f-2bd6-4897-a4cd-f3320f54e99e) Brilliance 75 · Fire 69 · Scintillation 66 · in our census, where the T73 scores 98 · 76 · 80 in GGG How the Octagon Cut handles light in GGG, measured: brilliance 75, fire 69 and 21% leakage, set against the T73 in the same stone and against the same cut in diamond. [Get the files](https://digitalgemology.com/gemstones/ggg/octagon#buy) [Open it in the Simulator](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=octagon&stone=ggg&ct=1.00&view=angle&lighting=studio&turn=0) [All cuts in GGG](https://digitalgemology.com/gemstones/ggg) Light Return map of the Octagon Cut in GGG, face-up, from our own tracer at refractive index 1.97. Red, green and blue return light to the eye; gray leaks. ## Octagon Cut GGG GGG has a refractive index of 1.970 and a dispersion of 0.045. Its critical angle, from the low end of that range, is 30.5°, so a round design needs a pavilion of at least 37.4° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.970, the midpoint of the published range, and a fire spread of 0.039, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 1.970, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the Octagon Cut in GGG live. The Octagon Cut has 49 facets, a table of 60.0% of its width and a total depth of 61.0% of its width; its pavilion mains sit at 29.3°. In GGG, the census returns 75 of 100 for brilliance and 69 for fire, against 98 and 76 for the T73, our benchmark, in the same stone; the same Octagon Cut in diamond reads 71 and 76. ## Is GGG good in an Octagon? Pros and cons, measured ### Pros - [Holds its light better in GGG than in diamond](https://digitalgemology.com/gemstones/ggg/octagon#pro-tiltStab) 100 vs 97 ### Cons - [Heavier than the same cut in diamond](https://digitalgemology.com/gemstones/ggg/octagon#con-weight) 2.47 vs 1.23 ct - [Returns less light than the T73 in GGG](https://digitalgemology.com/gemstones/ggg/octagon#con-brilliance) 75 vs 98 - [Leaks more light than the T73 in GGG](https://digitalgemology.com/gemstones/ggg/octagon#con-leak) 21 vs 2 - [Fewer facets, less sparkle](https://digitalgemology.com/gemstones/ggg/octagon#con-scint) 66 vs 80 Compared with the T73 Round Brilliant in GGG 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](https://digitalgemology.com/about/how-we-measure). ## All eight scores against the T73 At a glance: the Octagon Cut in GGG (white) against the T73 Round Brilliant in GGG (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 ggg: ahead on 1, level on 2, behind on 5. - Global 80, the comparison 90, difference −10 - Brilliance 75, the comparison 98, difference −23 - Fire 69, the comparison 76, difference −7 - Scintillation 66, the comparison 80, difference −14 - Spread 100, the comparison 100, difference 0 - Symmetry 100, the comparison 100, difference 0 - Shape-norm 99, the comparison 105, difference −6 - Tilt 100, the comparison 82, difference +18 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=octagon&stone=ggg); these are the same census figures as our [Cut Performance Index](https://digitalgemology.com/learn/cut-performance-index). ## What the Octagon Cut gains in GGG ### Holds its light better in GGG than in diamond **Tilt 100** against 97 for the Octagon Cut in diamond: 3 points higher Tilt is how much of its face-up brilliance a stone keeps when the census tilts it 20° about its long axis, with 2,200 rays. The Octagon Cut keeps 100 against 97 for the same cut in diamond. The tilt strips below show the maps at 0°, 10°, 20° and 30°, with each picture's own leak share under it. Octagon Cut in GGG · Tilt 100 0° · 26% leak 10° · 16% leak 20° · 17% leak 30° · 28% leak Octagon Cut in diamond · Tilt 97 0° · 23% leak 10° · 15% leak 20° · 19% leak 30° · 23% leak 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; gray is leakage. The share under each frame is that picture's own. [Try it yourself: Compare the Tilt spoke in the Cut Performance Wheel](https://digitalgemology.com/tools/cut-performance-wheel?cut=octagon&stone=ggg&vs=octagon&vsstone=diamond) ## What the Octagon Cut gives up in GGG ### Heavier than the same cut in diamond **2.47 ct** at 6.5 mm, against 1.23 ct for the same cut in diamond (+100%) Weight follows specific gravity: 7.05 for GGG against 3.52 for diamond, so the same model at the same size weighs 2.47 ct here and 1.23 ct in diamond, 6.5 mm across. Nothing about the light changes with it. *Weight of a 6.5 mm Octagon Cut: 2.47 ct in GGG, 1.23 ct in diamond* 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 every gemstone on the Octagon Cut page](https://digitalgemology.com/cuts/octagon#stones) ### Returns less light than the T73 in GGG **Brilliance 75** against 98 for the T73 Round Brilliant in GGG: 23 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 GGG, whose critical angle is 30.5°, the Octagon Cut returns 75 of 100 and the T73 98. The Octagon Cut's pavilion mains sit at 29.3°, the T73's at 40.8°. The maps below show where each stone's light returns from and where it leaks. Octagon Cut in GGG · Brilliance 75 T73 Round Brilliant in GGG · Brilliance 98 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-Broken Hearts and Arrows](https://digitalgemology.com/gemstones/ggg/dg-broken-hearts-and-arrows) reads 98 for brilliance in GGG, 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=octagon&stone=ggg&ct=1.00&view=up&map=1&turn=0) ### Leaks more light than the T73 in GGG **Leakage 21** against 2 for the T73 Round Brilliant in GGG: 19 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 Octagon Cut leaks 21% in GGG against 2% for the T73 in GGG. Grey in the maps below is leaking light; the share under each picture is that picture's own. Octagon Cut in GGG · Leakage 21 0° · 26% leak 10° · 16% leak 20° · 17% leak 30° · 28% leak T73 Round Brilliant in GGG · Leakage 2 0° · 0% leak 10° · 4% leak 20° · 14% leak 30° · 23% 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-Broken Hearts and Arrows](https://digitalgemology.com/gemstones/ggg/dg-broken-hearts-and-arrows) reads 2% for leakage in GGG, 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=octagon&stone=ggg&ct=1.00&view=up&map=1&turn=0) ### Fewer facets, less sparkle **Scintillation 66** against 80 for the T73 Round Brilliant in GGG: 14 points lower Scintillation follows the number of facets the stone shows: 100 × (1 − e^(−facets / 45)). The Octagon Cut has 49 facets and the T73 73, so 66 against 80. It depends on the geometry alone, so it is the same in every stone. *Facet diagram of the Octagon Cut: its crown, seen face-up, 49 facets in all* Octagon Cut · 49 facets · Scintillation 66 *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. **What helps:** [the DG-Miliano](https://digitalgemology.com/gemstones/ggg/dg-miliano) reads 98 for scintillation in GGG, the best of the cuts we score there. [Try it yourself: Compare the Scintillation spoke in the Cut Performance Wheel](https://digitalgemology.com/tools/cut-performance-wheel?cut=octagon&stone=ggg) ## Our verdict on the Octagon Cut in GGG Pick the Octagon Cut in GGG for this: it holds its light better than in diamond when tilted. The catch: it weighs more than in diamond, returns less light than the T73, leaks more light than the T73 and has fewer facets to sparkle with. If that catch matters more to you, [the DG-Broken Hearts and Arrows](https://digitalgemology.com/gemstones/ggg/dg-broken-hearts-and-arrows) reads 98 for brilliance in GGG, 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 Octagon Cut model we traced. ## Octagon Cut GGG: questions ### Is the Octagon a good cut for GGG? In our census the Octagon Cut returns 75 of 100 for brilliance and 69 for fire in GGG, against 98 and 76 for the T73 in the same stone. Against that round and against the same cut in diamond it has 1 pro and 4 cons by our thresholds; the summary above names them. ### What pavilion angle does GGG need? At least 37.4° for a round design: GGG's critical angle is 30.5°, 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 Octagon Cut's pavilion mains sit at 29.3°. ### How much does a Octagon weigh in GGG? At 6.5 mm across, 2.47 ct in GGG, against 1.23 ct for the same cut in diamond (+100%): GGG's specific gravity is 7.05, diamond's 3.52. ### Can I see the Octagon in GGG in 3D? Yes: the 3D Gemstone Simulator renders it live, with GGG's own refractive index and dispersion. GGG 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 Octagon Cut files *6 formats* *Millimeters* *Watertight* ### Octagon Cut 3D files The Octagon Cut as exact geometry: 49 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/26baac35-16bd-4143-97ba-9eeb7fd4da11) *GemCad* *96 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. - **.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/390b595d-894b-4e34-be35-57f44d569591) Save with a bundle: the Octagon Cut cutting files are also in [Faceter's Classics](https://digitalgemology.com/cuts/#bundles), 10 cuts for €22.49 until 1 December, then €29.99 (€69.90 as single files). [Buy the bundle](https://digitalgemology.lemonsqueezy.com/checkout/buy/9170b0c0-5357-490e-b6ef-3ce4f7fcd282?checkout%5Bdiscount_code%5D=BUNDLE25). 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 [GGG: optical properties and the top ten cuts](https://digitalgemology.com/gemstones/ggg) · [The Octagon Cut: specifications, model and files](https://digitalgemology.com/cuts/octagon) ### Other cuts in GGG - [T73 Round Brilliant](https://digitalgemology.com/gemstones/ggg/t73-round-brilliant) - [T105 Round Brilliant](https://digitalgemology.com/gemstones/ggg/t105-round-brilliant) - [DG-Vitruvio](https://digitalgemology.com/gemstones/ggg/dg-vitruvio) - [DG-Anteros](https://digitalgemology.com/gemstones/ggg/dg-anteros) - [DG-Broken Hearts and Arrows](https://digitalgemology.com/gemstones/ggg/dg-broken-hearts-and-arrows) - [Baguette Cut](https://digitalgemology.com/gemstones/ggg/baguette) - [Emerald Cut](https://digitalgemology.com/gemstones/ggg/emerald-cut) - [Marquise Cut](https://digitalgemology.com/gemstones/ggg/marquise) - [Oval Cut](https://digitalgemology.com/gemstones/ggg/oval) - [Pear Cut](https://digitalgemology.com/gemstones/ggg/pear) - [Radiant Cut](https://digitalgemology.com/gemstones/ggg/radiant) - [Rectangle Cut](https://digitalgemology.com/gemstones/ggg/rectangle) - [Teardrop Cut](https://digitalgemology.com/gemstones/ggg/teardrop) - [Asscher Cut](https://digitalgemology.com/gemstones/ggg/asscher) - [Cushion Cut](https://digitalgemology.com/gemstones/ggg/cushion) - [Emerald Square Cut](https://digitalgemology.com/gemstones/ggg/emerald-square) - [Princess Cut](https://digitalgemology.com/gemstones/ggg/princess) - [Radiant Square Cut](https://digitalgemology.com/gemstones/ggg/radiant-square) - [Square Cut](https://digitalgemology.com/gemstones/ggg/square) - [Triangle Cut](https://digitalgemology.com/gemstones/ggg/triangle) - [Trilliant Cut](https://digitalgemology.com/gemstones/ggg/trilliant) - [Trillion Cut](https://digitalgemology.com/gemstones/ggg/trillion) - [Hexagon Cut](https://digitalgemology.com/gemstones/ggg/hexagon) - [Portuguese Bird's Nest Cut](https://digitalgemology.com/gemstones/ggg/portuguese-birds-nest) - [Old Single Cut](https://digitalgemology.com/gemstones/ggg/old-single) - [Mazarin Cut](https://digitalgemology.com/gemstones/ggg/mazarin) - [Peruzzi Cut](https://digitalgemology.com/gemstones/ggg/peruzzi) - [Old Mine Cut](https://digitalgemology.com/gemstones/ggg/old-mine) - [Old European Cut](https://digitalgemology.com/gemstones/ggg/old-european) - [T57 Round Brilliant](https://digitalgemology.com/gemstones/ggg/t57-round-brilliant) - [DG-M5](https://digitalgemology.com/gemstones/ggg/dg-m5) - [DG-Miliano](https://digitalgemology.com/gemstones/ggg/dg-miliano) - [DG-Rafaello](https://digitalgemology.com/gemstones/ggg/dg-rafaello) - [DG-Bowtie](https://digitalgemology.com/gemstones/ggg/dg-bowtie) - [DG-Elongated Hexagon](https://digitalgemology.com/gemstones/ggg/dg-elongated-hexagon) - [DG-Octagonal Kite](https://digitalgemology.com/gemstones/ggg/dg-octagonal-kite) ### The Octagon Cut in other gemstones - [Moissanite](https://digitalgemology.com/gemstones/moissanite/octagon) - [Diamond](https://digitalgemology.com/gemstones/diamond/octagon) - [Cubic Zirconia](https://digitalgemology.com/gemstones/cubic-zirconia/octagon) - [Ruby](https://digitalgemology.com/gemstones/ruby/octagon) - [Sapphire](https://digitalgemology.com/gemstones/sapphire/octagon) - [Emerald](https://digitalgemology.com/gemstones/emerald/octagon) - [Amethyst](https://digitalgemology.com/gemstones/amethyst/octagon) - [Topaz](https://digitalgemology.com/gemstones/topaz/octagon) - [Spinel](https://digitalgemology.com/gemstones/spinel/octagon) - [Demantoid](https://digitalgemology.com/gemstones/demantoid/octagon) - [Zircon](https://digitalgemology.com/gemstones/zircon/octagon) - [Tourmaline](https://digitalgemology.com/gemstones/tourmaline/octagon) - [Peridot](https://digitalgemology.com/gemstones/peridot/octagon) - [Tanzanite](https://digitalgemology.com/gemstones/tanzanite/octagon) - [YAG](https://digitalgemology.com/gemstones/yag/octagon) - [Pyrope](https://digitalgemology.com/gemstones/pyrope/octagon) - [Almandine](https://digitalgemology.com/gemstones/almandine/octagon) - [Spessartine](https://digitalgemology.com/gemstones/spessartine/octagon) - [Grossular](https://digitalgemology.com/gemstones/grossular/octagon) - [Chrysoberyl](https://digitalgemology.com/gemstones/chrysoberyl/octagon) - [Kunzite](https://digitalgemology.com/gemstones/kunzite/octagon) - [Iolite](https://digitalgemology.com/gemstones/iolite/octagon) - [Morganite](https://digitalgemology.com/gemstones/morganite/octagon) - [Strontium titanate](https://digitalgemology.com/gemstones/strontium-titanate/octagon) - [Synthetic rutile](https://digitalgemology.com/gemstones/synthetic-rutile/octagon)