---
title: "Amethyst 3D Gem Models & Faceting Diagrams"
description: "Amethyst 3D models and faceting diagrams: RI 1.544, critical angle 40.4°, and the top ten brilliants and jewelry cuts in amethyst, by brilliance, fire and scintillation."
url: https://digitalgemology.com/gemstones/amethyst
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

> Markdown copy of https://digitalgemology.com/gemstones/amethyst. 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

[Gemstones](https://digitalgemology.com/gemstones/)

# Amethyst 3D models and cutting files

Refractive index 1.544 to 1.553 · critical angle 40.4° · 37 cuts scored

Crystal structure, one unit cell · drag to turn

## Cutting amethyst (quartz)

Amethyst is purple quartz. Quartz has one of the lowest refractive indices of the common faceting materials. Its critical angle is large, so designs made for diamond window badly unless the cutter makes the pavilion steeper. It is also a favorite first stone for cutters, and designers test most faceting designs in quartz first.

Amethyst often shows color zoning. Cutters orient the rough so the darker zone sits low in the pavilion, where the facets spread its color across the face-up stone.

## Amethyst optical properties

**Refractive index** 1.544 to 1.553

**Birefringence** 0.009

**Dispersion** 0.013

**Hardness (Mohs)** 7

**Specific gravity** 2.65

**Crystal system** Trigonal

**Critical angle** 40.4°

**Guide minimum pavilion angle** 40.4° for a round design

Where a property has a range, we calculate angles from the lower refractive index. It gives the stricter limit.

## The top ten cuts in amethyst

**In amethyst, the DG-M5 Cut performs best of the 11 brilliants we score: 85 for brilliance, 50 for fire and 85 for scintillation.** The DG-Anteros Cut follows at 82, 54 and 80, then the DG-Vitruvio Cut at 71, 36 and 98. Of the three, the DG-M5 Cut has the highest brilliance and the DG-Anteros Cut has the most fire.

**The top ten brilliants in amethyst, ranked by brilliance, fire and scintillation added together (equal totals share a place), each out of 100, with the T73 Round Brilliant benchmark in amethyst**

| Cut | Brilliance | Fire | Scintillation |
| --- | --- | --- | --- |
| [DG-M5](https://digitalgemology.com/gemstones/amethyst/dg-m5), *House cut* | 85 (T73 benchmark 72) | 50 (T73 benchmark 36) | 85 (T73 benchmark 80) |
| [DG-Anteros](https://digitalgemology.com/gemstones/amethyst/dg-anteros), *Brilliant* | 82 (T73 benchmark 72) | 54 (T73 benchmark 36) | 80 (T73 benchmark 80) |
| [DG-Vitruvio](https://digitalgemology.com/gemstones/amethyst/dg-vitruvio), *Brilliant* | 71 (T73 benchmark 72) | 36 (T73 benchmark 36) | 98 (T73 benchmark 80) |
| [DG-Broken Hearts and Arrows](https://digitalgemology.com/gemstones/amethyst/dg-broken-hearts-and-arrows), *Brilliant* | 71 (T73 benchmark 72) | 35 (T73 benchmark 36) | 86 (T73 benchmark 80) |
| [T73 Round Brilliant](https://digitalgemology.com/gemstones/amethyst/t73-round-brilliant), *Benchmark* | 72 | 36 | 80 |
| [T105 Round Brilliant](https://digitalgemology.com/gemstones/amethyst/t105-round-brilliant), *Brilliant* | 65 (T73 benchmark 72) | 31 (T73 benchmark 36) | 90 (T73 benchmark 80) |
| [DG-Miliano](https://digitalgemology.com/gemstones/amethyst/dg-miliano), *House cut* | 60 (T73 benchmark 72) | 28 (T73 benchmark 36) | 98 (T73 benchmark 80) |
| [T57 Round Brilliant](https://digitalgemology.com/gemstones/amethyst/t57-round-brilliant), *Historic cut* | 71 (T73 benchmark 72) | 37 (T73 benchmark 36) | 72 (T73 benchmark 80) |
| [Old European](https://digitalgemology.com/gemstones/amethyst/old-european), *Historic cut* | 59 (T73 benchmark 72) | 37 (T73 benchmark 36) | 81 (T73 benchmark 80) |
| [DG-Rafaello](https://digitalgemology.com/gemstones/amethyst/dg-rafaello), *House cut* | 45 (T73 benchmark 72) | 26 (T73 benchmark 36) | 96 (T73 benchmark 80) |

Score out of 100 T73 Round Brilliant, our benchmark, in amethyst **Brilliants:** the round cuts we score, from the Old Single to our house rounds. Ranked by brilliance, fire and scintillation added together; equal totals share a place

**In amethyst, the Oval Cut performs best of the 23 jewelry cuts we score: 52 for brilliance, 69 for fire and 87 for scintillation.** The Teardrop Cut follows at 49, 60 and 81, then the Pear Cut at 52, 60 and 76.

**The top ten jewelry cuts in amethyst, ranked by brilliance, fire and scintillation added together (equal totals share a place), each out of 100, with the T73 Round Brilliant benchmark in amethyst**

| Cut | Brilliance | Fire | Scintillation |
| --- | --- | --- | --- |
| [Oval](https://digitalgemology.com/gemstones/amethyst/oval), *Jewelry cut* | 52 (T73 benchmark 72) | 69 (T73 benchmark 36) | 87 (T73 benchmark 80) |
| [Teardrop](https://digitalgemology.com/gemstones/amethyst/teardrop), *Jewelry cut* | 49 (T73 benchmark 72) | 60 (T73 benchmark 36) | 81 (T73 benchmark 80) |
| [Pear](https://digitalgemology.com/gemstones/amethyst/pear), *Jewelry cut* | 52 (T73 benchmark 72) | 60 (T73 benchmark 36) | 76 (T73 benchmark 80) |
| [Asscher](https://digitalgemology.com/gemstones/amethyst/asscher), *Jewelry cut* | 60 (T73 benchmark 72) | 52 (T73 benchmark 36) | 72 (T73 benchmark 80) |
| [Trillion](https://digitalgemology.com/gemstones/amethyst/trillion), *Jewelry cut* | 60 (T73 benchmark 72) | 44 (T73 benchmark 36) | 80 (T73 benchmark 80) |
| [Cushion](https://digitalgemology.com/gemstones/amethyst/cushion), *Jewelry cut* | 69 (T73 benchmark 72) | 24 (T73 benchmark 36) | 85 (T73 benchmark 80) |
| [Square](https://digitalgemology.com/gemstones/amethyst/square), *Jewelry cut* | 65 (T73 benchmark 72) | 34 (T73 benchmark 36) | 78 (T73 benchmark 80) |
| [Trilliant](https://digitalgemology.com/gemstones/amethyst/trilliant), *Jewelry cut* | 63 (T73 benchmark 72) | 34 (T73 benchmark 36) | 79 (T73 benchmark 80) |
| [Emerald Square](https://digitalgemology.com/gemstones/amethyst/emerald-square), *Jewelry cut* | 61 (T73 benchmark 72) | 40 (T73 benchmark 36) | 72 (T73 benchmark 80) |
| [Marquise](https://digitalgemology.com/gemstones/amethyst/marquise), *Jewelry cut* | 38 (T73 benchmark 72) | 48 (T73 benchmark 36) | 86 (T73 benchmark 80) |

Score out of 100 T73 Round Brilliant, our benchmark, in amethyst **Jewelry cuts:** the fancy shapes we score, our house shapes among them. Ranked by brilliance, fire and scintillation added together; equal totals share a place

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 facets give as a stone moves, and we read it from the facets of each cut. We score 37 cuts, with the same figures as the [Cut Performance Wheel](https://digitalgemology.com/tools/cut-performance-wheel?cut=dg-m5&stone=amethyst), where you can compare any cut with any other in amethyst. Mazarin, Peruzzi and Old Mine, historic cushions, are in neither list. Each measured cut’s own page shows its figures in all seven gemstones. A simulation of the geometry, not a grading report.

## Amethyst: questions

### What pavilion angle should I use for amethyst?

For a round design, at least 40.4°. At that angle or steeper, light that arrives straight down reflects off both sides of the pavilion, beyond the critical angle of amethyst (40.4°). Then it leaves through the table. The angle is the larger of the critical angle and (180° − critical angle) / 4. Faceters usually cut a degree or two steeper, for light that arrives off the axis. Fancy shapes vary, so every cut page lists its own figure.

Head-on light in amethyst at 40.4°: look at the first main, where it meets the critical angle.

### What is the critical angle of amethyst?

40.4°, from a refractive index of 1.544. Light that strikes a facet from inside the stone at less than this angle from the normal of the facet passes out. At a larger angle, it reflects.

### Which cuts work best in amethyst?

We add brilliance, fire and scintillation together. By that total, the DG-M5 Cut, the DG-Anteros Cut and the DG-Vitruvio Cut are the best brilliants in amethyst. By the same total, the best jewelry cuts are the Oval Cut, the Teardrop Cut and the Pear Cut. We score 37 cuts in all, and this page ranks the top ten of each.

### How much does amethyst weigh compared with diamond?

Amethyst has a specific gravity of about 2.65, and diamond has 3.52. So a stone of the same size weighs about 0.75 times as much as the diamond.

## Other gemstones

- [Diamond](https://digitalgemology.com/gemstones/diamond)
- [Moissanite](https://digitalgemology.com/gemstones/moissanite)
- [Cubic Zirconia](https://digitalgemology.com/gemstones/cubic-zirconia)
- [Ruby](https://digitalgemology.com/gemstones/ruby)
- [Sapphire](https://digitalgemology.com/gemstones/sapphire)
- [Emerald](https://digitalgemology.com/gemstones/emerald)

[Browse all cuts](https://digitalgemology.com/cuts/)