Old Single Cut Sapphire: Pros, Cons & Light Leakage

Sapphire bends light far less than diamond: its critical angle is about 34.6°, against 24.4° for diamond. Light inside the stone must meet a facet more steeply to reflect, and the Old Single's few large facets rarely give it that chance.

The result is the weakest pairing on these pages. We publish it because people search for it, and because the numbers explain why.

Is sapphire good in an Old Single cut? Pros and cons

Pros

None that we measure.

Cons

Almost no fire 9 vs 84
Little light back to the eye 36 vs 94
Half the light leaks 54 vs 5
Few flashes 44 vs 80

Compared with the T73 Round Brilliant in sapphire and with the Old Single 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 Old Single 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.

Against the T73 Round Brilliant in sapphire: ahead on 1, level on 1, behind on 6.

Global49, the comparison 79, difference −30
Brilliance36, the comparison 94, difference −58
Fire9, the comparison 37, difference −28
Scintillation44, the comparison 80, difference −36
Spread97, the comparison 100, difference −3
Symmetry100, the comparison 100, difference 0
Shape-norm39, the comparison 102, difference −63
Tilt100, the comparison 75, difference +25

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 sapphire gains in an Old Single cut

We found no score where an Old Single in sapphire beats either baseline. Its Tilt reads 100, the top of the scale, but that is the share of very little light kept when tilted: its brilliance is 36. The case for it is colour and the antique outline, which we do not measure.

Why the Old Single struggles in sapphire

Almost no fire

Fire 9 against 84 for the Old Single Cut in diamond: 75 points lower

Sapphire's dispersion is 0.018, under half of diamond's. With so little light returning, the Old Single's fire falls to 9, against 84 for the same cut in diamond.

Old single cut in sapphire face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 9) — 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.

Old single cut in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 84) — 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: Little helps in sapphire: the best of our cuts for fire in sapphire, the Oval Cut, reaches 74.

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

Little light back to the eye

Brilliance 36 against 94 for the T73 Round Brilliant in sapphire: 58 points lower

The face-up map is mostly grey: light leaving through the pavilion.

Old single cut in sapphire face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 36) — 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.

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) — 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: In sapphire the T73 Round Brilliant returns 94, DG-Anteros 97 and DG-M5 100.

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

Half the light leaks

Leakage 54 against 5 for the T73 Round Brilliant in sapphire: 49 points higher

Half of it, 54%, is lost through the pavilion in our census; the T73 loses 5% in sapphire. The strip stays largely grey at every angle.

Old single cut in sapphire tilted 0 degrees: Light Return map, 69% of the face leaking — 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.

Old single cut in sapphire tilted 10 degrees: Light Return map, 48% of the face leaking — 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: A steeper pavilion is not the answer here: the mains already sit at 48.48°, well above sapphire's guide minimum of 36.4°. A different cut is: DG-Anteros leaks 3% in sapphire.

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

Few flashes

Scintillation 44 against 80 for the T73 Round Brilliant in sapphire: 36 points lower

26 facets against the T73's 73.

Old Single Cut · 26 facets · Scintillation 44

T73 Round Brilliant · 73 facets · Scintillation 80

Scintillation follows the number of facets: more facets, more and smaller flashes as the stone moves. Count the facets in each crown. Drawn from each cut's own model.

What helps: The facet plan sets it; the Old European Cut Sapphire has 81.

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

Who an Old Single sapphire suits

We would not choose an Old Single for a sapphire meant to be bright. It may suit a small, deep-coloured accent where the outline matters more than light.

For a round sapphire, the T73 Round Brilliant or DG-Anteros; for an antique round, the Old European Cut Sapphire, the least leaky of these old cuts in sapphire.

Old Single Cut Sapphire: questions

Is the Old Single a good cut for sapphire?

Not in our census: Brilliance 36 against 94 for the T73 in sapphire, and 54% of the light leaking.

Why does an Old Single sapphire look dark?

Sapphire's critical angle is about 34.6°, so light passes out through facets that would reflect it in diamond: 54% leaks here, 19% in diamond.

Which round cut works best in sapphire?

Of the cuts we sell, DG-M5 (100), DG-Anteros (97) and the T73 (94) return the most light in sapphire.

Does an Old Single sapphire show its colour well?

We do not measure colour. Our renders use a medium-tone blue, and the leaking areas read darker; whether that suits a stone is the cutter's call.

Get the Old Single Cut files

6 formatsMillimetresWatertight

Old Single Cut 3D files

The Old Single Cut as exact geometry: 26 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

GemCad96 index

Old Single Cut cutting files

The Old Single Cut as a faceting design: 18 + 8 girdles = 26 facets, 96 index, 8-fold mirror-image symmetry, ready for the machine.

.ascGemCad design file, 96 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 Old Single Cut: specifications, model and files

Old Single Cut Sapphire: why the eight cut leaks half its light in sapphire