--- title: "Gemstone 3D Models & Cutting Files" description: "3D models and faceting diagrams for diamond, moissanite, cubic zirconia, ruby, sapphire, emerald and amethyst, with each stone's critical angle." url: https://digitalgemology.com/gemstones/ image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01 --- > Markdown copy of https://digitalgemology.com/gemstones/. 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 Catalog # 3D models and cutting files by gemstone Seven stones · 37 cuts scored in each ## Why the stone changes the cut A faceting design is a set of angles, and the right angles depend on the material. When the refractive index of a stone is lower, its critical angle is larger. Then its pavilion must be steeper to keep light inside. A pavilion that is perfect in diamond can make an amethyst look washed out in the center. Each page below gives the numbers for one stone. It also ranks the top ten brilliants and the top ten jewelry cuts in that stone, by brilliance, fire and scintillation. Head-on light (the arrow) reflects only outside the gray wedge, and the wedge gets wider as the refractive index drops. - [**Diamond** RI 2.417 Critical angle 24.4° Guide pavilion 38.9°](https://digitalgemology.com/gemstones/diamond) - [**Moissanite** RI 2.648 to 2.691 Critical angle 22.2° Guide pavilion 39.5°](https://digitalgemology.com/gemstones/moissanite) - [**Cubic Zirconia** RI 2.15 to 2.18 Critical angle 27.7° Guide pavilion 38.1°](https://digitalgemology.com/gemstones/cubic-zirconia) - [**Ruby** RI 1.762 to 1.770 Critical angle 34.6° Guide pavilion 36.4°](https://digitalgemology.com/gemstones/ruby) - [**Sapphire** RI 1.762 to 1.770 Critical angle 34.6° Guide pavilion 36.4°](https://digitalgemology.com/gemstones/sapphire) - [**Emerald** RI 1.577 to 1.583 Critical angle 39.4° Guide pavilion 39.4°](https://digitalgemology.com/gemstones/emerald) - [**Amethyst** RI 1.544 to 1.553 Critical angle 40.4° Guide pavilion 40.4°](https://digitalgemology.com/gemstones/amethyst) ## One cut does not fit every stone The clearest way to see it is with two rounds that look almost the same on paper. The T73 has the round brilliant proportions published in 1919, calculated for diamond. DG-Anteros keeps the same 73 facets and the same 53% table. But its crown and pavilion angles are re-solved for moissanite, which bends light more strongly. Put each cut in each stone and look. Diamond RI 2.417 Moissanite RI 2.648 [T73](https://digitalgemology.com/cuts/t73-round-brilliant) ![T73 in diamond: face-up Light Return map](https://digitalgemology.com/img/demo/t73-round-brilliant-diamond-light.webp?v=14ae5a3a) ![T73 in diamond through a Hearts and Arrows viewer, face-up: the arrows](https://digitalgemology.com/img/demo/t73-round-brilliant-diamond-arrows.webp?v=8d5cbfc5) *Arrows, face-up* ![T73 in diamond through a Hearts and Arrows viewer, face-down: the hearts](https://digitalgemology.com/img/demo/t73-round-brilliant-diamond-hearts.webp?v=d069878f) *Hearts, face-down* **T73 in diamond.** Crisp arrows and crisp hearts: the proportions were worked out for diamond. ![T73 in moissanite: face-up Light Return map](https://digitalgemology.com/img/demo/t73-round-brilliant-moissanite-light.webp?v=0611f596) ![T73 in moissanite through a Hearts and Arrows viewer, face-up: the arrows](https://digitalgemology.com/img/demo/t73-round-brilliant-moissanite-arrows.webp?v=746a4f84) *Arrows, face-up* ![T73 in moissanite through a Hearts and Arrows viewer, face-down: the hearts](https://digitalgemology.com/img/demo/t73-round-brilliant-moissanite-hearts.webp?v=5ac7f585) *Hearts, face-down* **T73 in moissanite.** Both patterns break up. The same angles bend moissanite's light too far. [DG-Anteros](https://digitalgemology.com/cuts/dg-anteros) ![DG-Anteros in diamond: face-up Light Return map](https://digitalgemology.com/img/demo/bl-anteros-diamond-light.webp?v=6ef05310) ![DG-Anteros in diamond through a Hearts and Arrows viewer, face-up: the arrows](https://digitalgemology.com/img/demo/bl-anteros-diamond-arrows.webp?v=4817c5c4) *Arrows, face-up* ![DG-Anteros in diamond through a Hearts and Arrows viewer, face-down: the hearts](https://digitalgemology.com/img/demo/bl-anteros-diamond-hearts.webp?v=ab808069) *Hearts, face-down* **DG-Anteros in diamond.** The arrows go dark and the hearts flood with white: wrong stone for this cut. ![DG-Anteros in moissanite: face-up Light Return map](https://digitalgemology.com/img/demo/bl-anteros-moissanite-light.webp?v=e865dab4) ![DG-Anteros in moissanite through a Hearts and Arrows viewer, face-up: the arrows](https://digitalgemology.com/img/demo/bl-anteros-moissanite-arrows.webp?v=18bac25b) *Arrows, face-up* ![DG-Anteros in moissanite through a Hearts and Arrows viewer, face-down: the hearts](https://digitalgemology.com/img/demo/bl-anteros-moissanite-hearts.webp?v=8b73a390) *Hearts, face-down* **DG-Anteros in moissanite.** Crisp arrows and eight clean hearts: the cut it was drawn for. Direct Indirect Contrast Leak. Face-up, the way a light-return scope shows a stone. White: light from the viewer's white disk, which draws the arrows and hearts. Red: light from the red reflector. Black: the lens port, or light that never comes back. We compute all eight panels per instrument from the cut files themselves, with the same rules for every stone. The Hearts & Arrows viewer has a 2.5° lens hole, a white disk to 13.5° and a red reflector to 90°.