--- title: "T57 Round Brilliant Cut: 3D Model & Faceting Diagram" description: "T57 Round Brilliant Cut 3D model and GemCad faceting diagram: 57 facets, 8.15 x 8.15 x 4.83 mm. Six formats, measured in 7 gemstones." url: https://digitalgemology.com/cuts/t57-round-brilliant image: https://digitalgemology.com/img/cuts/t57-round-brilliant-og.jpg?v=d06c1420 --- > Markdown copy of https://digitalgemology.com/cuts/t57-round-brilliant. 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 [Cuts](https://digitalgemology.com/cuts/) · [Historic cuts](https://digitalgemology.com/cuts/#historic) # T57 Round Brilliant Cut **Buy (instant download, personal-use license):** [3D files · €9.99](https://digitalgemology.lemonsqueezy.com/checkout/buy/6818fad8-a74d-4c41-80a7-dfc92d1f6b11) · [Cutting files · €6.99](https://digitalgemology.lemonsqueezy.com/checkout/buy/ac539570-4805-4645-af3f-8cf47ba6b593) · [T57 Round Brilliant Cut 3D files, €9.99 · Personal use](https://digitalgemology.lemonsqueezy.com/checkout/buy/6818fad8-a74d-4c41-80a7-dfc92d1f6b11) · [T57 Round Brilliant Cut cutting files, €6.99 · Personal use](https://digitalgemology.lemonsqueezy.com/checkout/buy/ac539570-4805-4645-af3f-8cf47ba6b593) · [Buy the bundle](https://digitalgemology.lemonsqueezy.com/checkout/buy/dcf2c236-6e04-4292-8040-9d21ac6446d1?checkout%5Bdiscount_code%5D=HISTORIC25) · [Get the cube free](https://digitalgemology.lemonsqueezy.com/checkout/buy/2d1ab55f-2bd6-4897-a4cd-f3320f54e99e) 3D model and faceting diagram · 57 facets · 8.15 x 8.15 mm The 57-facet round brilliant with a knife-edge girdle. It has the proportions that Marcel Tolkowsky published in Diamond Design in 1919. The facet plan has nothing added: table, 8 stars, 8 bezels, 16 upper halves, 8 pavilion mains and 16 lower halves. [3D files · €9.99](https://digitalgemology.lemonsqueezy.com/checkout/buy/6818fad8-a74d-4c41-80a7-dfc92d1f6b11) [Cutting files · €6.99](https://digitalgemology.lemonsqueezy.com/checkout/buy/ac539570-4805-4645-af3f-8cf47ba6b593) Instant download · [Personal-use license](https://digitalgemology.com/licence) · [What is in the files](https://digitalgemology.com/cuts/t57-round-brilliant#buy) · [Grade it in 3D](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=t57-round-brilliant) ## About the T57 Round Brilliant Cut The 57-facet round brilliant with a knife-edge girdle. It has the proportions that Marcel Tolkowsky published in Diamond Design in 1919. The facet plan has nothing added: table, 8 stars, 8 bezels, 16 upper halves, 8 pavilion mains and 16 lower halves. It is the last step in the evolution of the brilliant before the faceted girdle became standard. It is the historical baseline of the modern round. We keep it for teaching, comparison and period work. ## T57 Round Brilliant Cut specifications Measured from the delivered model, not quoted from a standard. **Category** Historic cuts **Facets** 57 planar facets **Outline** Length to width 1.000 **Total depth** 59.2% of width **Crown angle (main)** 34.5° **Pavilion angle (main)** 40.8° **Reference size** 8.15 x 8.15 x 4.83 mm at 1.81 ct in diamond **Volume** 102.78 mm³ **Cutting file accuracy** Every crown and pavilion facet within 0.005° of the 3D model (average under 0.001°) **Index gear** 96 **Symmetry** 8-fold mirror-image symmetry **Tiers** 3 crown, 2 pavilion **Files** STEP, 3DM, STL, OBJ, FBX, GLB, GemCad .asc, tier table, diagram ## Face-up and profile *Face-up facet diagram of the T57 Round Brilliant Cut* Face-up: the crown facets, drawn from the model's own edges. *Side profile of the T57 Round Brilliant Cut* Profile: 59.2% total depth. ![Light Return map of the T57 Round Brilliant Cut in diamond: a computed render showing direct, indirect and contrast light across the face-up stone.](https://digitalgemology.com/img/cuts/t57-round-brilliant-lightmap.webp?v=debcbd64) Light Return map of the T57 Round Brilliant Cut in diamond. A computed render of the model's geometry, not a photograph. ## Cut Performance Index - Diamond **88.6** overall, 7th of 37 - Moissanite **89.8** overall, 10th of 37 - Cubic Zirconia **91.8** overall, 7th of 37 - Ruby **78.1** overall, 8th of 37 - Sapphire **78.1** overall, 8th of 37 - Emerald **71.7** overall, 6th of 37 - Amethyst **68.6** overall, 6th of 37 [See how every cut compares](https://digitalgemology.com/learn/cut-performance-index) ## How the T57 Round Brilliant Cut performs in seven gemstones **The T57 Round Brilliant Cut performs best in cubic zirconia, where its brilliance and fire together are highest: 98 for brilliance and 87 for fire.** Its fire peaks in moissanite, at 98. In diamond it scores 92 for brilliance and 79 for fire, against 93 and 78 for the T73 benchmark. Its scintillation, 72, comes from its pattern of facets, so it is the same in every stone. **Brilliance, fire and scintillation of the T57 Round Brilliant Cut in seven gemstones, out of 100, with the T73 Round Brilliant benchmark in each** | Gemstone | Brilliance | Fire | Scintillation | | --- | --- | --- | --- | | [Diamond](https://digitalgemology.com/gemstones/diamond) | 92 (T73 benchmark 93) | 79 (T73 benchmark 78) | 72 (T73 benchmark 80) | | [Moissanite](https://digitalgemology.com/gemstones/moissanite) *Highest fire* | 85 (T73 benchmark 86) | 98 (T73 benchmark 97) | 72 (T73 benchmark 80) | | [Cubic Zirconia](https://digitalgemology.com/gemstones/cubic-zirconia) *Best overall* *Highest brilliance* | 98 (T73 benchmark 98) | 87 (T73 benchmark 87) | 72 (T73 benchmark 80) | | [Ruby](https://digitalgemology.com/gemstones/ruby) | 94 (T73 benchmark 94) | 39 (T73 benchmark 37) | 72 (T73 benchmark 80) | | [Sapphire](https://digitalgemology.com/gemstones/sapphire) | 94 (T73 benchmark 94) | 39 (T73 benchmark 37) | 72 (T73 benchmark 80) | | [Emerald](https://digitalgemology.com/gemstones/emerald) | 78 (T73 benchmark 78) | 40 (T73 benchmark 39) | 72 (T73 benchmark 80) | | [Amethyst](https://digitalgemology.com/gemstones/amethyst) | 71 (T73 benchmark 72) | 37 (T73 benchmark 36) | 72 (T73 benchmark 80) | Score out of 100 T73 Round Brilliant, our benchmark, in the same stone **Best overall:** the highest brilliance and fire together Brilliance is the share of face-up light that the stone returns. Fire is the share of that light that splits into color. Both come from our face-up light census. Scintillation is the sparkle that the facets give as the stone moves, and we read it from its facets. They are the same figures as the [Cut Performance Wheel](https://digitalgemology.com/tools/cut-performance-wheel?cut=t57-round-brilliant&stone=cubic-zirconia), where you can compare the T57 Round Brilliant Cut with any other cut. A simulation of the geometry, not a grading report. ### Head-on reflection, critical angle and weight in each stone The same geometry behaves differently in every material. Light that meets a pavilion facet at less than the critical angle of the stone does not reflect. It passes straight out of the back and shows face-up as a window. For each stone, we measured how much of the pavilion of this model, seen face-down, is steeper than that angle. We also measured what the model weighs at its reference size. Head-on light in amethyst: a steep facet reflects it, a shallow facet lets it out of the back. | Stone | Refractive index | Critical angle | Pavilion reflecting head-on light | Weight at this size | Verdict | | --- | --- | --- | --- | --- | --- | | [Diamond](https://digitalgemology.com/gemstones/diamond) | 2.417 | 24.4° | 100% | 1.81 ct | Holds head-on light | | [Moissanite](https://digitalgemology.com/gemstones/moissanite) | 2.648 to 2.691 | 22.2° | 100% | 1.65 ct | Holds head-on light | | [Cubic Zirconia](https://digitalgemology.com/gemstones/cubic-zirconia) | 2.15 to 2.18 | 27.7° | 100% | 2.98 ct | Holds head-on light | | [Ruby](https://digitalgemology.com/gemstones/ruby) | 1.762 to 1.770 | 34.6° | 100% | 2.06 ct | Holds head-on light | | [Sapphire](https://digitalgemology.com/gemstones/sapphire) | 1.762 to 1.770 | 34.6° | 100% | 2.06 ct | Holds head-on light | | [Emerald](https://digitalgemology.com/gemstones/emerald) | 1.577 to 1.583 | 39.4° | 100% | 1.40 ct | Holds head-on light | | [Amethyst](https://digitalgemology.com/gemstones/amethyst) | 1.544 to 1.553 | 40.4° | 100% | 1.36 ct | Holds head-on light | Head-on light, first reflection. The [3D Gemstone Simulator](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=t57-round-brilliant) traces the full Light Return in each of these gemstones. ## Available in… The T57 Round Brilliant stone by stone: what each gemstone gains and loses in this cut, measured. - [Diamond](https://digitalgemology.com/gemstones/diamond/t57-round-brilliant) - [Moissanite](https://digitalgemology.com/gemstones/moissanite/t57-round-brilliant) - [Cubic Zirconia](https://digitalgemology.com/gemstones/cubic-zirconia/t57-round-brilliant) - [Ruby](https://digitalgemology.com/gemstones/ruby/t57-round-brilliant) - [Sapphire](https://digitalgemology.com/gemstones/sapphire/t57-round-brilliant) - [Emerald](https://digitalgemology.com/gemstones/emerald/t57-round-brilliant) - [Amethyst](https://digitalgemology.com/gemstones/amethyst/t57-round-brilliant) ![T57 Round Brilliant Cut 3D model](https://digitalgemology.com/img/cuts/t57-round-brilliant-3d.webp?v=2ceea3ce) ## Grade the T57 Round Brilliant Cut in 3D Open it in the 3D Gemstone Simulator. Set its carat, color, clarity and cut grade in any of seven gemstones. Turn it under ten kinds of light, and watch its 3D gemstone report change as you go. Free, in your browser. [Open it in the Simulator](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=t57-round-brilliant) ## T57 Round Brilliant Cut: questions ### What files come with the T57 Round Brilliant Cut 3D model? Six formats. STEP is the exact faceted solid for CAD, and 3DM is for Rhino. STL and OBJ are meshes. FBX is for Blender, 3ds Max, Maya, Cinema 4D, Unity and Unreal. GLB is for the web and AR. All are in millimeters at real-world scale, with 57 planar facets. ### Is there a faceting diagram for the T57 Round Brilliant Cut? Yes. The cutting files contain a GemCad .asc design (57 facets, 96 index, 8-fold mirror-image symmetry) and a printable faceting diagram. They also contain a tier table in CSV, with the angles, indices and cutting order. ### Does the T57 Round Brilliant Cut work in sapphire, emerald or amethyst? We measured the pavilion of this model against the critical angle of each stone. In Diamond, Moissanite, Cubic Zirconia, Ruby, Sapphire, Emerald, Amethyst, the whole pavilion reflects head-on light. ### How accurate is the T57 Round Brilliant Cut cutting file? We check it facet by facet against the 3D model that it was written from. Every crown and pavilion facet within 0.005° of the 3D model (average under 0.001°). The angles are the ones you set on the machine. The 3D model is the same stone that you render or set. ### How big is the T57 Round Brilliant Cut model, and what does it weigh? The model measures 8.15 x 8.15 x 4.83 mm, which is 1.81 ct in diamond. At the same size, it weighs 1.65 ct in moissanite, 2.98 ct in cubic zirconia, 2.06 ct in ruby, 2.06 ct in sapphire, 1.40 ct in emerald, 1.36 ct in amethyst. You can scale it uniformly to any size: the weight follows the cube of the size. Twice the size holds eight times the material, so it weighs eight times as much. ### Can I 3D print or cast the T57 Round Brilliant Cut model? Yes. The mesh is watertight and manifold, with outward normals and no duplicate vertices, so it prints and casts without repair. Use the STEP file when you need the exact faceted solid in CAD. ## Learn Free lessons that use this cut, with videos where they have one. - [Tolkowsky's 1919 ideal cut: the brilliant that was calculated](https://digitalgemology.com/learn/historic-cuts/tolkowsky-ideal-cut-1919) - [The parts of a diamond: crown, girdle and pavilion](https://digitalgemology.com/learn/diamond-anatomy/parts-of-a-diamond) - [Hearts and arrows diamonds: precision you can see](https://digitalgemology.com/learn/historic-cuts/hearts-and-arrows-diamonds) - [Crown angle and crown height in a round diamond](https://digitalgemology.com/learn/diamond-anatomy/diamond-crown-angle) - [Pavilion angle and pavilion depth: how a diamond keeps the light in](https://digitalgemology.com/learn/diamond-anatomy/diamond-pavilion-angle) - [Diamond girdle thickness: thin, medium, thick and what it costs you](https://digitalgemology.com/learn/diamond-anatomy/diamond-girdle-thickness) [All lessons](https://digitalgemology.com/learn) ## More historic cuts - [Old Single Cut](https://digitalgemology.com/cuts/old-single) - [Mazarin Cut](https://digitalgemology.com/cuts/mazarin) - [Peruzzi Cut](https://digitalgemology.com/cuts/peruzzi) - [Old Mine Cut](https://digitalgemology.com/cuts/old-mine) - [Old European Cut](https://digitalgemology.com/cuts/old-european) ## Get the T57 Round Brilliant Cut files *6 formats* *Millimeters* *Watertight* ### T57 Round Brilliant Cut 3D files The T57 Round Brilliant Cut as exact geometry: 57 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/6818fad8-a74d-4c41-80a7-dfc92d1f6b11) *GemCad* *96 index* ### T57 Round Brilliant Cut cutting files The T57 Round Brilliant Cut as a faceting design: 57 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/ac539570-4805-4645-af3f-8cf47ba6b593) Save with a bundle: the T57 Round Brilliant Cut 3D and cutting files are also in [Historic Cuts Complete](https://digitalgemology.com/cuts/#bundles), 6 cuts for €29.99 until 1 December, then €39.99 (€101.88 as single files). [Buy the bundle](https://digitalgemology.lemonsqueezy.com/checkout/buy/dcf2c236-6e04-4292-8040-9d21ac6446d1?checkout%5Bdiscount_code%5D=HISTORIC25). 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).