Cutting emerald (beryl)
Emerald is green beryl. With a low refractive index it needs a steep pavilion to keep head-on light in the stone, and with typical inclusions and some brittleness it is usually given a step cut with cropped corners, the shape that took its name.
Its low dispersion means colour, not fire, is what a cut has to show, which is another reason step cuts suit it so well.
Emerald 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 emerald
For each cut we measured how much of the pavilion, seen face-down, is steeper than emerald's critical angle of 39.4°, so that head-on light reflects instead of leaking out of the back. Weights are for each model at its reference size.
| Cut | Category | Pavilion reflecting head-on light | Weight | Verdict | Files |
|---|---|---|---|---|---|
| BL-Anteros Cut | Brilliants | 100% | 1.48 ct | Holds head-on light | 3D + cutting |
| BL-Vitruvio Cut | Brilliants | 100% | 1.55 ct | Holds head-on light | 3D + cutting |
| Cushion Cut | Jewellery cuts | 100% | 1.17 ct | Holds head-on light | 3D |
| Emerald Cut | Jewellery cuts | 100% | 1.17 ct | Holds head-on light | 3D + cutting |
| Princess Cut | Jewellery cuts | 100% | 1.12 ct | Holds head-on light | 3D |
| Square Cut | Jewellery cuts | 100% | 1.20 ct | Holds head-on light | 3D + cutting |
| T105 Round Brilliant Cut | Brilliants | 100% | 1.42 ct | Holds head-on light | 3D + cutting |
| T57 Round Brilliant Cut | Historic cuts | 100% | 1.40 ct | Holds head-on light | 3D + cutting |
| T73 Round Brilliant Cut | Brilliants | 100% | 1.54 ct | Holds head-on light | 3D + cutting |
| Triangle Cut | Jewellery cuts | 100% | 1.55 ct | Holds head-on light | 3D + cutting |
| Old European Cut | Historic cuts | 100% | 1.55 ct | Holds head-on light | 3D + cutting |
| Old Mine Cut | Historic cuts | 100% | 1.55 ct | Holds head-on light | 3D + cutting |
| Mazarin Cut | Historic cuts | 99% | 1.55 ct | Holds head-on light | 3D + cutting |
| Old Single Cut | Historic cuts | 99% | 1.55 ct | Holds head-on light | 3D + cutting |
| Peruzzi Cut | Historic cuts | 99% | 1.55 ct | Holds head-on light | 3D + cutting |
| Radiant Square Cut | Jewellery cuts | 97% | 1.17 ct | Minor windowing | 3D + cutting |
| Hexagon Cut | Jewellery cuts | 89% | 1.17 ct | Steepen the pavilion | 3D + cutting |
| Trillion Cut | Jewellery cuts | 89% | 1.55 ct | Steepen the pavilion | 3D + cutting |
| Octagon Cut | Jewellery cuts | 89% | 1.55 ct | Steepen the pavilion | 3D + cutting |
| Emerald Square Cut | Jewellery cuts | 81% | 1.17 ct | Steepen the pavilion | 3D + cutting |
| Asscher Cut | Jewellery cuts | 79% | 1.17 ct | Steepen the pavilion | 3D + cutting |
| Heart Cut | Jewellery cuts | 79% | 1.17 ct | Steepen the pavilion | 3D |
| Portuguese Bird's Nest Cut | Jewellery cuts | 78% | 1.55 ct | Steepen the pavilion | 3D + cutting |
| Baguette Cut | Jewellery cuts | 78% | 1.17 ct | Steepen the pavilion | 3D + cutting |
| Trilliant Cut | Jewellery cuts | 77% | 1.19 ct | Steepen the pavilion | 3D + cutting |
| Oval Cut | Jewellery cuts | 55% | 1.24 ct | Steepen the pavilion | 3D |
| Pear Cut | Jewellery cuts | 52% | 1.23 ct | Steepen the pavilion | 3D + cutting |
| Teardrop Cut | Jewellery cuts | 52% | 1.23 ct | Steepen the pavilion | 3D + cutting |
| Marquise Cut | Jewellery cuts | 43% | 1.23 ct | Steepen the pavilion | 3D + cutting |
| Radiant Cut | Jewellery cuts | 29% | 1.55 ct | Steepen the pavilion | 3D |
| Rectangle Cut | Jewellery cuts | 27% | 1.21 ct | Steepen the pavilion | 3D + cutting |
Emerald: questions
What pavilion angle should I use for emerald?
For a round design, about 43.1° or steeper. That is the angle at which head-on light meets both sides of the pavilion above emerald's critical angle of 39.4° and reflects twice before leaving through the crown. Fancy shapes vary, which is why every cut page lists its own figure.
What is the critical angle of emerald?
39.4°, from a refractive index of 1.577. Light striking a facet from inside the stone at less than this angle from the facet's normal passes out; above it, it reflects.
Which cuts work best in emerald?
15 of our 31 cuts reflect head-on light from their whole pavilion in emerald, including BL-Anteros Cut, BL-Vitruvio Cut, Cushion Cut, Emerald Cut, Princess Cut, Square Cut.
How much does emerald weigh compared with diamond?
Emerald has a specific gravity of about 2.72 against diamond's 3.52, so a stone of the same size weighs about 0.77 times as much as the diamond.