Square Cut Sapphire: the square brilliant, short of the round on light and fire

Brilliance 78 · Fire 45 · Scintillation 78 · in our census, where the T73 scores 94 · 37 · 80 in sapphire

The square counterpart of the round brilliant: in sapphire it loses about a sixth of the round's light and holds steady when tipped.

See it in the simulatorGet the files
The Square Cut in sapphire, 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 Sapphire

Our square brilliant carries a full facet set on a square outline: 69 facets, 65.0% deep, with a steep 41.39° pavilion.

In sapphire nothing beats a baseline by our margins. It is not a dark stone, 78 for light, and it keeps more of that light at a tilt than the T73 does; but each gap that counts runs the other way.

Among our modern fancy shapes only the princess has a steeper pavilion figure, and still the square leaks three times what the T73 does.

Is a square cut a good choice for sapphire? Pros and cons

Pros

None by our margins. It keeps more light when tipped than the T73, from a lower starting point.

Cons

Compared with the T73 Round Brilliant in sapphire 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 sapphire (white) against the T73 Round Brilliant in sapphire (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 sapphire, against the T73 Round Brilliant in sapphire as an outline. Solid white marks where it reaches further, hatching where it falls short. The scores are listed below.50100Global−4Brilliance−16Fire+8Scintillation−2Spread−2Symmetry0Shape-norm0Tilt+9

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

  • Global75, the comparison 79, difference −4
  • Brilliance78, the comparison 94, difference −16
  • Fire45, the comparison 37, difference +8
  • Scintillation78, the comparison 80, difference −2
  • Spread98, the comparison 100, difference −2
  • Symmetry100, the comparison 100, difference 0
  • Shape-norm102, the comparison 102, difference 0
  • Tilt84, the comparison 75, difference +9
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 a sapphire gains as a square

No score clears our margins against the T73 in sapphire or the square in diamond. Tilted 20°, it keeps 84 of its face-up light against 75 for the T73, but we count Tilt as a pro only when Brilliance is within five points, and here it is 78 against 94. What the square offers is a clean outline that sits well beside other squares.

Where the square falls short in sapphire

Much less fire than in diamond

Fire 45 against 72 for the Square Cut in diamond: 27 points lower

Fire 45 against 72 for the same square in diamond, though above the T73 in sapphire, 37.

Square cut in sapphire face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 45)

Square Cut in sapphire · Fire 45

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: Sapphire limits it; the Oval Cut Sapphire reaches 74.

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

About a sixth less light than the T73

Brilliance 78 against 94 for the T73 Round Brilliant in sapphire: 16 points lower

Brilliance 78 against 94. In diamond the square returns 85, so sapphire costs it some light as well.

Square cut in sapphire face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 78)

Square Cut in sapphire · Brilliance 78

T73 round brilliant in sapphire face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 94)

T73 Round Brilliant in sapphire · Brilliance 94

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: For more light with corners, the Cushion Cut Sapphire returns 88 in sapphire.

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

Heavier than diamond

1.30 ct at 6.5 mm, against 1.14 ct for the same cut in diamond (+14%)

Edge to edge at 6.5 mm, a sapphire square is 1.30 ct where the diamond is 1.14 ct.

Sapphire1.30 ctDiamond1.14 ct
A Square Cut 6.5 mm across, weighed from the model's measured volume and each stone's specific gravity.

What helps: Specify squares by edge length.

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

Three times the T73's leakage

Leakage 16 against 5 for the T73 Round Brilliant in sapphire: 11 points higher

16% against 5% in our census. With the pavilion at 41.39°, comfortably over sapphire's 36.4°, a shallow pavilion is not the cause.

Square Cut in sapphire · Leakage 16

Square cut in sapphire tilted 0 degrees: Light Return map, 16% of the face leaking0° · 16% leak
Square cut in sapphire tilted 10 degrees: Light Return map, 14% of the face leaking10° · 14% leak
Square cut in sapphire tilted 20 degrees: Light Return map, 30% of the face leaking20° · 30% leak
Square cut in sapphire tilted 30 degrees: Light Return map, 32% of the face leaking30° · 32% leak

T73 Round Brilliant in sapphire · Leakage 5

T73 round brilliant in sapphire tilted 0 degrees: Light Return map, 1% of the face leaking0° · 1% leak
T73 round brilliant in sapphire tilted 10 degrees: Light Return map, 10% of the face leaking10° · 10% leak
T73 round brilliant in sapphire tilted 20 degrees: Light Return map, 29% of the face leaking20° · 29% leak
T73 round brilliant in sapphire tilted 30 degrees: Light Return map, 30% of the face leaking30° · 30% 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: The Cushion Cut Sapphire leaks 11%; a steeper square pavilion is not what our numbers suggest.

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

Who a square sapphire suits

The square suits a sapphire set in a row or a geometric design, where a straight edge and steady light under tilt are worth a few points face-up.

For more light in a squarish outline, the Cushion Cut Sapphire. With pointed corners, the Princess Cut Sapphire returns less, 68. For a step-cut square that faces up larger, the Emerald Square Cut Sapphire.

Square sapphires are often calibrated for channel settings, where hardness matters: at 9, sapphire resists daily scratches better than most coloured stones.

Square Cut Sapphire: questions

Is a square cut good for sapphire?

It is middling: Brilliance 78 against 94 for the T73, 16% leakage, Tilt 84.

Square or princess cut for a sapphire?

The square: Brilliance 78 against 68, leakage 16% against 27%.

Square or cushion for a sapphire?

The cushion returns more light (88) and leaks less (11%); the square holds more when tilted (84 against 72).

What does a 6.5 mm square sapphire weigh?

1.30 ct, measured edge to edge; the diamond equivalent is 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

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

Other cuts in sapphire

The Square Cut in other gemstones