Square Cut Amethyst: a square brilliant, a quarter lighter in weight than diamond

Brilliance 65 · Fire 34 · Scintillation 78 · in our census, where the T73 scores 72 · 36 · 80 in amethyst

The square counterpart of the round brilliant: in quartz it leaks barely more than the T73, and returns less light.

See it in the simulatorGet the files
The Square Cut in amethyst, rendered at an angle in our 3D Gemstone Simulator under studio light
Rendered in our 3D Gemstone Simulator from the Square Cut model, 1.00 ct, studio light.

Square Cut Amethyst

Our square brilliant carries a full facet set, 69 facets, on a 41.39° pavilion, 65.0% deep. That pavilion is about one degree past amethyst's guide minimum of 40.4°.

In amethyst it leaks 29%, close to the T73's 28%, and holds its light well when tipped: Tilt 84. Its brilliance sits too far below the T73's for that Tilt to count as a pro.

The cons are set mostly against the same square in diamond, where the cut is far stronger. Its fire, 34, sits about level with the T73's 36 in amethyst, and under half the diamond square's.

Is a square brilliant good for amethyst? Pros and cons

Pros

Cons

Compared with the T73 Round Brilliant in amethyst and with the Square Cut in diamond. A difference counts from 3 points (Brilliance, Fire, Tilt, Leakage), 5 (Scintillation, Symmetry), 2 (Spread) 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.

All eight scores against the T73

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

Performance wheel: Square Cut in amethyst, against the T73 Round Brilliant in amethyst as an outline. Solid white marks where it reaches further, hatching where it falls short. The scores are listed below.50100Global−3Brilliance−7Fire−2Scintillation−2Spread−2Symmetry0Shape-norm+9Tilt+4

Against the T73 Round Brilliant in amethyst: ahead on 2, level on 1, behind on 5.

  • Global67, the comparison 70, difference −3
  • Brilliance65, the comparison 72, difference −7
  • Fire34, the comparison 36, difference −2
  • Scintillation78, the comparison 80, difference −2
  • Spread98, the comparison 100, difference −2
  • Symmetry100, the comparison 100, difference 0
  • Shape-norm86, the comparison 77, difference +9
  • Tilt84, the comparison 80, difference +4
Face-up light census, a different measure from the Cut Grading Tool; Spread and Shape-norm above 100 sit on the ring.
Open it in the Cut Performance Wheel

What amethyst gains in a square brilliant

A quarter lighter than diamond

0.86 ct at 6.5 mm, against 1.14 ct for the same cut in diamond (−25%)

A 6.5 mm square brilliant weighs 0.86 ct in amethyst, 1.14 ct in diamond.

Amethyst0.86 ctDiamond1.14 ct
A Square Cut 6.5 mm across, weighed from the model's measured volume and each stone's specific gravity.

Try it yourself: Weights in all seven gemstones on the Square Cut page

The catch with a square amethyst

Under half the diamond's fire

Fire 34 against 72 for the Square Cut in diamond: 38 points lower

The diamond square scores 72. Quartz splits light into colour so weakly that the same facets reach under half that, about the T73's level in amethyst.

Square cut in amethyst face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 34)

Square Cut in amethyst · Fire 34

Square cut in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 72)

Square Cut in diamond · Fire 72

Look at the coloured flashes: those are fire. Same light, same size, same face-up angle; rendered by our 3D Gemstone Simulator from each cut's own model.

What helps: In a square outline, the Asscher Cut Amethyst reaches 52; the Oval Cut Amethyst gives the most in amethyst, 69.

Try it yourself: See the fire in the 3D Gemstone Simulator

Less light than the diamond square

Brilliance 65 against 85 for the Square Cut in diamond: 20 points lower

Diamond's high index holds the light the square's corners send down; quartz lets more of it go.

Square cut in amethyst face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 65)

Square Cut in amethyst · Brilliance 65

Square cut in diamond face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 85)

Square Cut in diamond · Brilliance 85

Red, green and blue = light returning to the eye; grey = light leaving through the pavilion. 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 Cushion Cut Amethyst returns 69 in amethyst.

Try it yourself: Open this Light Return map in the simulator

More leakage than in diamond

Leakage 29 against 10 for the Square Cut in diamond: 19 points higher

29% of the light in our census escapes in amethyst, against 10% in diamond. Of the square outlines we measure in amethyst, it leaks the least.

Square Cut in amethyst · Leakage 29

Square cut in amethyst tilted 0 degrees: Light Return map, 26% of the face leaking0° · 26% leak
Square cut in amethyst tilted 10 degrees: Light Return map, 35% of the face leaking10° · 35% leak
Square cut in amethyst tilted 20 degrees: Light Return map, 34% of the face leaking20° · 34% leak
Square cut in amethyst tilted 30 degrees: Light Return map, 46% of the face leaking30° · 46% leak

Square Cut in diamond · Leakage 10

Square cut in diamond tilted 0 degrees: Light Return map, 7% of the face leaking0° · 7% leak
Square cut in diamond tilted 10 degrees: Light Return map, 11% of the face leaking10° · 11% leak
Square cut in diamond tilted 20 degrees: Light Return map, 16% of the face leaking20° · 16% leak
Square cut in diamond tilted 30 degrees: Light Return map, 22% of the face leaking30° · 22% leak
Each frame is the Light Return map with the stone tilted away from you by the angle shown; grey is light leaving through the pavilion. The share under each frame is that picture's own.

What helps: Steepening is not the fix: the pavilion is at 41.39°, above the guide minimum. DG-M5 Amethyst leaks 15%.

Try it yourself: Tilt it yourself in the simulator's light map

Marginally smaller for its weight

Spread 98 against 100 for the T73 Round Brilliant in amethyst: 2 points lower

At 65.0% deep it puts a little more weight below the girdle than the T73, so it faces up slightly smaller per carat.

Square Cut · 6.84 mm at 1.00 ct · Spread 98

T73 Round Brilliant · 7.12 mm at 1.00 ct · Spread 100

Both stones weigh 1.00 ct in amethyst and are drawn to the same scale, from each cut's own model. Spread is face-up size per carat: a deeper stone carries more weight below the girdle and looks smaller for its weight.

What helps: Choose by millimetres. For a square face that looks larger for its weight, the Asscher Cut Amethyst reaches 107.

Try it yourself: Compare the Spread spoke in the Cut Performance Wheel

Who a square amethyst suits

Choose the square brilliant for an amethyst centre or accent stone with crisp corners and steady light as it moves. Its corners need protecting in a setting; quartz at hardness 7 chips more easily than diamond.

A square is also a sensible second shape for a hobby cutter who has finished a first round in amethyst: the facet plan is close to the round's, and the pavilion angle clears the guide minimum.

For more light in a square, the Cushion Cut Amethyst; for a face that looks bigger, the Asscher Cut Amethyst.

Square Cut Amethyst: questions

Is a square cut good for amethyst?

It is the least leaky square outline we measure in amethyst, 29%, with Brilliance 65 against 72 for the T73.

Square or cushion amethyst?

The cushion returns more light (69 against 65); the square holds better when tipped (84 against 67).

Why does a square amethyst leak less than an Asscher?

Our census measures the result, 29% against 39%. A brilliant pavilion at 41.39° stands far steeper than a step cut's.

What does a 6.5 mm square amethyst weigh?

0.86 ct; in diamond, 1.14 ct.

Get the Square Cut files

6 formatsMillimetresWatertight

Square Cut 3D files

The Square Cut as exact geometry: 69 planar facets, real-world scale, ready for CAD, rendering, printing and casting.

  • STEPExact faceted solid for CAD
  • 3DMRhino, closed mesh on its own layer
  • STLWatertight mesh for printing and casting
  • OBJMesh for modelling and rendering
  • FBXBlender, 3ds Max, Maya, Cinema 4D, Unity, Unreal
  • GLBWeb, AR and quick previews
€9.99 · Personal useBuy the 3D files
GemCad64 index

Square Cut cutting files

The Square Cut as a faceting design: 57 + 12 girdles = 69 facets, 64 index, 4-fold mirror-image symmetry, ready for the machine.

  • .ascGemCad design file, 64 index gear
  • .csvTier table: angles, indices and cutting order
  • DiagramPrintable faceting diagram
€9.99 · Personal useBuy the cutting files

Questions before you buy? Email us.

More gemstones and cuts

Amethyst: optical properties and the top ten cuts · The Square Cut: specifications, model and files

Other cuts in amethyst

The Square Cut in other gemstones