---
title: "Rectangle Cut Iolite: Pros, Cons and Scores"
description: "Rectangle Cut in iolite: brilliance 24, fire 60, leakage 72%, 2 pros and 4 cons against the T73, from our ray-traced light census."
url: https://digitalgemology.com/gemstones/iolite/rectangle
image: https://digitalgemology.com/img/stone-cuts/rectangle-iolite-og.jpg?v=92b07804
---

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# Rectangle Cut Iolite: lighter than the same cut in diamond

**Buy (instant download, personal-use license):** [Rectangle Cut 3D files, €9.99 · Personal use](https://digitalgemology.lemonsqueezy.com/checkout/buy/1e627cbe-69a3-44f0-a5da-e5cab29131b8) · [Rectangle Cut cutting files, €6.99 · Personal use](https://digitalgemology.lemonsqueezy.com/checkout/buy/1d8e7f45-2f16-44f2-8215-0aea13e29c3b) · [Get the cube free](https://digitalgemology.lemonsqueezy.com/checkout/buy/2d1ab55f-2bd6-4897-a4cd-f3320f54e99e)

Brilliance 24 · Fire 60 · Scintillation 63 · in our census, where the T73 scores 72 · 58 · 80 in iolite

How the Rectangle Cut handles light in iolite, measured: brilliance 24, fire 60 and 72% leakage, set against the T73 in the same stone and against the same cut in diamond.

[Get the files](https://digitalgemology.com/gemstones/iolite/rectangle#buy) [Open it in the Simulator](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=rectangle&stone=iolite&ct=1.00&view=angle&lighting=studio&turn=0) [All cuts in iolite](https://digitalgemology.com/gemstones/iolite)

Light Return map of the Rectangle Cut in iolite, face-up, from our own tracer at refractive index 1.542. Red, green and blue return light to the eye; gray leaks.

## Rectangle Cut Iolite

Iolite has a refractive index of 1.542 to 1.551 and a dispersion of 0.017. Its critical angle, from the low end of that range, is 40.4°, so a round design needs a pavilion of at least 40.4° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.547, the midpoint of the published range, and a fire spread of 0.015, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 1.542, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the Rectangle Cut in iolite live.

The Rectangle Cut has 45 facets and a total depth of 62.0% of its width; its pavilion mains sit at 33.5°. In iolite, the census returns 24 of 100 for brilliance and 60 for fire, against 72 and 58 for the T73, our benchmark, in the same stone; the same Rectangle Cut in diamond reads 50 and 77.

## Is iolite good in a Rectangle? Pros and cons, measured

### Pros

- [Lighter than the same cut in diamond](https://digitalgemology.com/gemstones/iolite/rectangle#pro-weight) 1.56 vs 2.10 ct
- [Faces up larger for its weight](https://digitalgemology.com/gemstones/iolite/rectangle#pro-faceup) 121 vs 100

### Cons

- [Returns less light than the T73 in iolite](https://digitalgemology.com/gemstones/iolite/rectangle#con-brilliance) 24 vs 72
- [Leaks more light than the T73 in iolite](https://digitalgemology.com/gemstones/iolite/rectangle#con-leak) 72 vs 28
- [Less fire in iolite than in diamond](https://digitalgemology.com/gemstones/iolite/rectangle#con-fire) 60 vs 77
- [Fewer facets, less sparkle](https://digitalgemology.com/gemstones/iolite/rectangle#con-scint) 63 vs 80

Compared with the T73 Round Brilliant in iolite and with the Rectangle Cut in diamond. A difference counts from 3 points (Brilliance, Fire, Tilt, Leakage), 5 (Scintillation, Symmetry), 4% (face-up size per carat) or 5% (weight); Tilt counts as a pro only for a stone within 5 points of the brilliance it is compared with. [How we measure](https://digitalgemology.com/about/how-we-measure).

## All eight scores against the T73

At a glance: the Rectangle Cut in iolite (white) against the T73 Round Brilliant in iolite (dashed): solid white where it reaches further, hatched where it falls short. Each pro and con is explained, with pictures, below.

Against the T73 Round Brilliant in iolite: ahead on 2, level on 2, behind on 4.

- Global 55, the comparison 74, difference −19
- Brilliance 24, the comparison 72, difference −48
- Fire 60, the comparison 58, difference +2
- Scintillation 63, the comparison 80, difference −17
- Spread 100, the comparison 100, difference 0
- Symmetry 100, the comparison 100, difference 0
- Shape-norm 31, the comparison 77, difference −46
- Tilt 100, the comparison 81, difference +19

Face-up light census, a different measure from the Cut Grading Tool; Spread and Shape-norm above 100 sit on the ring. Spread is the census's estimate from depth alone; the face-up size in the pros and cons is measured from each model's outline. [Open it in the Cut Performance Wheel](https://digitalgemology.com/tools/cut-performance-wheel?cut=rectangle&stone=iolite); these are the same census figures as our [Cut Performance Index](https://digitalgemology.com/learn/cut-performance-index).

## What the Rectangle Cut gains in iolite

### Lighter than the same cut in diamond

**1.56 ct** at 6.5 mm, against 2.10 ct for the same cut in diamond (−26%)

Weight follows specific gravity: 2.61 for iolite against 3.52 for diamond, so the same model at the same size weighs 1.56 ct here and 2.10 ct in diamond, 6.5 mm across. Nothing about the light changes with it.

*Weight of a 6.5 mm Rectangle Cut: 1.56 ct in iolite, 2.10 ct in diamond*

A Rectangle Cut 6.5 mm across, weighed from the model's measured volume and each stone's specific gravity.

[Try it yourself: Weights in every gemstone on the Rectangle Cut page](https://digitalgemology.com/cuts/rectangle#stones)

### Faces up larger for its weight

**Face-up size 121** against 100 for the T73 Round Brilliant in iolite (T73 = 100): 21% more face-up area for the same weight

Face-up size is the outline's area per carat, measured from each model (T73 = 100): 121 for the Rectangle Cut against 100 for the T73. The same volume spread over a longer or shallower outline shows more face for the weight; it is the same in every stone, because specific gravity scales every cut alike.

*Face-up outline of the Rectangle Cut at 1.00 ct in iolite: 8.44 x 5.60 mm, drawn to scale*

Rectangle Cut · 8.44 x 5.60 mm at 1.00 ct · Face-up size 121

*Face-up outline of the T73 Round Brilliant at 1.00 ct in iolite: 7.15 mm, drawn to scale*

T73 Round Brilliant · 7.15 mm at 1.00 ct · Face-up size 100

Both stones weigh 1.00 ct in iolite and are drawn to the same scale in millimeters, from each cut's own model. Face-up size is the outline's area per carat, with the T73 at 100: a deeper stone, or a rounder outline, spreads less area for its weight.

[Try it yourself: See its size at 1.00 ct in iolite in the 3D Gemstone Simulator](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=rectangle&stone=iolite&ct=1.00&view=up&lighting=studio&turn=0)

## What the Rectangle Cut gives up in iolite

### Returns less light than the T73 in iolite

**Brilliance 24** against 72 for the T73 Round Brilliant in iolite: 48 points lower

Brilliance is the share of the 3,200 census rays that enter the stone and come back out of the crown towards the viewer. In iolite, whose critical angle is 40.4°, the Rectangle Cut returns 24 of 100 and the T73 72. The Rectangle Cut's pavilion mains sit at 33.5°, the T73's at 40.8°. The maps below show where each stone's light returns from and where it leaks.

Rectangle Cut in iolite · Brilliance 24

T73 Round Brilliant in iolite · Brilliance 72

Red, green and blue = light returning to the eye; gray = leakage, light that leaves heading down or stays inside. This is the head-on view; the Brilliance score averages a wider cone of light, so the score can differ from what one picture shows.

**What helps:** [the DG-M5](https://digitalgemology.com/gemstones/iolite/dg-m5) reads 85 for brilliance in iolite, the best of the cuts we score there.

[Try it yourself: Open this Light Return map in the simulator](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=rectangle&stone=iolite&ct=1.00&view=up&map=1&turn=0)

### Leaks more light than the T73 in iolite

**Leakage 72** against 28 for the T73 Round Brilliant in iolite: 44 points higher

Leakage is the share of the census rays that enter the stone and leave through the pavilion, or through the crown heading down. The Rectangle Cut leaks 72% in iolite against 28% for the T73 in iolite. Grey in the maps below is leaking light; the share under each picture is that picture's own.

Rectangle Cut in iolite · Leakage 72

0° · 78% leak

10° · 74% leak

20° · 70% leak

30° · 67% leak

T73 Round Brilliant in iolite · Leakage 28

0° · 13% leak

10° · 38% leak

20° · 36% leak

30° · 44% leak

Each frame is the Light Return map with the stone tilted away from you by the angle shown; gray is leakage. The share under each frame is that picture's own.

**What helps:** [the DG-M5](https://digitalgemology.com/gemstones/iolite/dg-m5) reads 15% for leakage in iolite, the best of the cuts we score there.

[Try it yourself: Tilt it yourself in the simulator's light map](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=rectangle&stone=iolite&ct=1.00&view=up&map=1&turn=0)

### Less fire in iolite than in diamond

**Fire 60** against 77 for the Rectangle Cut in diamond: 17 points lower

Fire is the share of the returned light that splits into color at the exit facet: the census traces each exit again at the refractive index minus and plus the fire spread (0.015 in iolite) and counts a ray as fire when the two directions differ by more than 0.6°. The Rectangle Cut reads 60 against 77 for the same cut in diamond. The figure is the census's; the 3D Gemstone Simulator renders iolite's fire live.

The fire figure is the census's, traced at the refractive index minus and plus the fire spread. [See the fire in the 3D Gemstone Simulator](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=rectangle&stone=iolite&ct=1.00&view=up&lighting=sun&turn=0): the Rectangle Cut in iolite under the sunny-day lighting.

**What helps:** [the Oval Cut](https://digitalgemology.com/gemstones/iolite/oval) reads 82 for fire in iolite, the best of the cuts we score there.

[Try it yourself: See the fire in the 3D Gemstone Simulator](https://digitalgemology.com/tools/3d_gemstone_simulator?cut=rectangle&stone=iolite&ct=1.00&view=up&lighting=sun&turn=0)

### Fewer facets, less sparkle

**Scintillation 63** against 80 for the T73 Round Brilliant in iolite: 17 points lower

Scintillation follows the number of facets the stone shows: 100 × (1 − e^(−facets / 45)). The Rectangle Cut has 45 facets and the T73 73, so 63 against 80. It depends on the geometry alone, so it is the same in every stone.

*Facet diagram of the Rectangle Cut: its crown, seen face-up, 45 facets in all*

Rectangle Cut · 45 facets · Scintillation 63

*Facet diagram of the T73 Round Brilliant: its crown, seen face-up, 73 facets in all*

T73 Round Brilliant · 73 facets · Scintillation 80

Scintillation follows the number of facets: more facets, more and smaller flashes as the stone moves. Compare the facet counts under the drawings; each drawing shows only the crown. Drawn from each cut's own model.

**What helps:** [the DG-Miliano](https://digitalgemology.com/gemstones/iolite/dg-miliano) reads 98 for scintillation in iolite, the best of the cuts we score there.

[Try it yourself: Compare the Scintillation spoke in the Cut Performance Wheel](https://digitalgemology.com/tools/cut-performance-wheel?cut=rectangle&stone=iolite)

## Our verdict on the Rectangle Cut in iolite

Pick the Rectangle Cut in iolite for this: it weighs less than in diamond and faces up larger for its weight. The catch: it returns less light than the T73, leaks more light than the T73, shows less fire than in diamond and has fewer facets to sparkle with.

If that catch matters more to you, [the DG-M5](https://digitalgemology.com/gemstones/iolite/dg-m5) reads 85 for brilliance in iolite, the best of the cuts we score there.

Every figure on this page is from our light census, traced at one refractive index: a simulation of the geometry, not a grading report. The 3D files and cutting files below are the same Rectangle Cut model we traced.

## Rectangle Cut Iolite: questions

### Is the Rectangle a good cut for iolite?

In our census the Rectangle Cut returns 24 of 100 for brilliance and 60 for fire in iolite, against 72 and 58 for the T73 in the same stone. Against that round and against the same cut in diamond it has 2 pros and 4 cons by our thresholds; the summary above names them.

### What pavilion angle does iolite need?

At least 40.4° for a round design: iolite's critical angle is 40.4°, from the low end of its refractive index range, and head-on light has to reflect off both sides of the pavilion and leave through the table. The Rectangle Cut's pavilion mains sit at 33.5°.

### How much does a Rectangle weigh in iolite?

At 6.5 mm across, 1.56 ct in iolite, against 2.10 ct for the same cut in diamond (-26%): iolite's specific gravity is 2.61, diamond's 3.52.

### Can I see the Rectangle in iolite in 3D?

Yes: the 3D Gemstone Simulator renders it live, with iolite's own refractive index and dispersion. Iolite is traced by the same light census as the other gemstones, with its refractive index and fire spread derived from published values, so its scores are on the same scale; the pictures here are our Light Return tracer, and the Cut Performance Wheel sets it against any other cut and stone.

## Get the Rectangle Cut files

*6 formats* *Millimeters* *Watertight*

### Rectangle Cut 3D files

The Rectangle Cut as exact geometry: 45 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/1e627cbe-69a3-44f0-a5da-e5cab29131b8)

*GemCad* *96 index*

### Rectangle Cut cutting files

The Rectangle Cut as a faceting design: 41 + 4 girdles = 45 facets, 96 index, 2-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/1d8e7f45-2f16-44f2-8215-0aea13e29c3b)

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).

## More gemstones and cuts

[Iolite: optical properties and the top ten cuts](https://digitalgemology.com/gemstones/iolite) · [The Rectangle Cut: specifications, model and files](https://digitalgemology.com/cuts/rectangle)

### Other cuts in iolite

- [T73 Round Brilliant](https://digitalgemology.com/gemstones/iolite/t73-round-brilliant)
- [T105 Round Brilliant](https://digitalgemology.com/gemstones/iolite/t105-round-brilliant)
- [DG-Vitruvio](https://digitalgemology.com/gemstones/iolite/dg-vitruvio)
- [DG-Anteros](https://digitalgemology.com/gemstones/iolite/dg-anteros)
- [DG-Broken Hearts and Arrows](https://digitalgemology.com/gemstones/iolite/dg-broken-hearts-and-arrows)
- [Baguette Cut](https://digitalgemology.com/gemstones/iolite/baguette)
- [Emerald Cut](https://digitalgemology.com/gemstones/iolite/emerald-cut)
- [Marquise Cut](https://digitalgemology.com/gemstones/iolite/marquise)
- [Oval Cut](https://digitalgemology.com/gemstones/iolite/oval)
- [Pear Cut](https://digitalgemology.com/gemstones/iolite/pear)
- [Radiant Cut](https://digitalgemology.com/gemstones/iolite/radiant)
- [Teardrop Cut](https://digitalgemology.com/gemstones/iolite/teardrop)
- [Asscher Cut](https://digitalgemology.com/gemstones/iolite/asscher)
- [Cushion Cut](https://digitalgemology.com/gemstones/iolite/cushion)
- [Emerald Square Cut](https://digitalgemology.com/gemstones/iolite/emerald-square)
- [Princess Cut](https://digitalgemology.com/gemstones/iolite/princess)
- [Radiant Square Cut](https://digitalgemology.com/gemstones/iolite/radiant-square)
- [Square Cut](https://digitalgemology.com/gemstones/iolite/square)
- [Triangle Cut](https://digitalgemology.com/gemstones/iolite/triangle)
- [Trilliant Cut](https://digitalgemology.com/gemstones/iolite/trilliant)
- [Trillion Cut](https://digitalgemology.com/gemstones/iolite/trillion)
- [Hexagon Cut](https://digitalgemology.com/gemstones/iolite/hexagon)
- [Octagon Cut](https://digitalgemology.com/gemstones/iolite/octagon)
- [Portuguese Bird's Nest Cut](https://digitalgemology.com/gemstones/iolite/portuguese-birds-nest)
- [Old Single Cut](https://digitalgemology.com/gemstones/iolite/old-single)
- [Mazarin Cut](https://digitalgemology.com/gemstones/iolite/mazarin)
- [Peruzzi Cut](https://digitalgemology.com/gemstones/iolite/peruzzi)
- [Old Mine Cut](https://digitalgemology.com/gemstones/iolite/old-mine)
- [Old European Cut](https://digitalgemology.com/gemstones/iolite/old-european)
- [T57 Round Brilliant](https://digitalgemology.com/gemstones/iolite/t57-round-brilliant)
- [DG-M5](https://digitalgemology.com/gemstones/iolite/dg-m5)
- [DG-Miliano](https://digitalgemology.com/gemstones/iolite/dg-miliano)
- [DG-Rafaello](https://digitalgemology.com/gemstones/iolite/dg-rafaello)
- [DG-Bowtie](https://digitalgemology.com/gemstones/iolite/dg-bowtie)
- [DG-Elongated Hexagon](https://digitalgemology.com/gemstones/iolite/dg-elongated-hexagon)
- [DG-Octagonal Kite](https://digitalgemology.com/gemstones/iolite/dg-octagonal-kite)

### The Rectangle Cut in other gemstones

- [Diamond](https://digitalgemology.com/gemstones/diamond/rectangle)
- [Moissanite](https://digitalgemology.com/gemstones/moissanite/rectangle)
- [Cubic Zirconia](https://digitalgemology.com/gemstones/cubic-zirconia/rectangle)
- [Ruby](https://digitalgemology.com/gemstones/ruby/rectangle)
- [Sapphire](https://digitalgemology.com/gemstones/sapphire/rectangle)
- [Emerald](https://digitalgemology.com/gemstones/emerald/rectangle)
- [Amethyst](https://digitalgemology.com/gemstones/amethyst/rectangle)
- [Topaz](https://digitalgemology.com/gemstones/topaz/rectangle)
- [Spinel](https://digitalgemology.com/gemstones/spinel/rectangle)
- [Demantoid](https://digitalgemology.com/gemstones/demantoid/rectangle)
- [Zircon](https://digitalgemology.com/gemstones/zircon/rectangle)
- [Tourmaline](https://digitalgemology.com/gemstones/tourmaline/rectangle)
- [Peridot](https://digitalgemology.com/gemstones/peridot/rectangle)
- [Tanzanite](https://digitalgemology.com/gemstones/tanzanite/rectangle)
- [YAG](https://digitalgemology.com/gemstones/yag/rectangle)
- [Pyrope](https://digitalgemology.com/gemstones/pyrope/rectangle)
- [Almandine](https://digitalgemology.com/gemstones/almandine/rectangle)
- [Spessartine](https://digitalgemology.com/gemstones/spessartine/rectangle)
- [Grossular](https://digitalgemology.com/gemstones/grossular/rectangle)
- [Chrysoberyl](https://digitalgemology.com/gemstones/chrysoberyl/rectangle)
- [Kunzite](https://digitalgemology.com/gemstones/kunzite/rectangle)
- [Morganite](https://digitalgemology.com/gemstones/morganite/rectangle)
- [GGG](https://digitalgemology.com/gemstones/ggg/rectangle)
- [Strontium titanate](https://digitalgemology.com/gemstones/strontium-titanate/rectangle)
- [Synthetic rutile](https://digitalgemology.com/gemstones/synthetic-rutile/rectangle)