Diamond cutting files and 3D models

Cutting diamond

Diamond has the highest refractive index of any natural gem in common use, so its critical angle is small and almost any sensible pavilion reflects head-on light. What separates a good diamond cut from an average one is how much of that light comes back towards the viewer, and how it is broken into brilliance and fire.

Diamond is not cut on a hobby faceting machine: it is sawn, bruted and polished on a scaife, or cut with lasers. Faceting files are still the standard way to plan and communicate a diamond design, and 3D models are what jewellery CAD needs.

Diamond optical properties

Where a property has a range, angles are calculated from the lower refractive index, which gives the stricter limit.

Every cut, measured in diamond

For each cut we measured how much of the pavilion, seen face-down, is steeper than diamond's critical angle of 24.4°, so that head-on light reflects instead of leaking out of the back. Weights are for each model at its reference size.

Diamond: questions

Other gemstones

• Moissanite
• Cubic Zirconia
• Ruby
• Sapphire
• Emerald
• Amethyst