Old Single Cut Ruby: a simple eight cut that lets half the light through

Brilliance 36 · Fire 9 · Scintillation 44 · in our census, where the T73 scores 94 · 37 · 80 in ruby

A table, one ring of crown facets and one ring of pavilion mains: in ruby, more than half the light in our census leaves through the back.

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

Old Single Cut Ruby

Think of an octahedron with its top sawn off for a table and its corners bevelled: that is the single cut, one crown angle and one pavilion angle throughout. We measured it with 26 facets, a 57.5% table, a 40.0° crown and a steep 48.48° pavilion.

That pavilion is twelve degrees past ruby's guide minimum of 36.4°, so the leak is not the classic window of a shallow stone. With so few facets, light that misses the main reflections has nowhere else to go.

Today the single cut lives on mostly in melee, tiny stones where a full brilliant would be wasted, and small calibrated rubies are among them.

Can an Old Single cut work for ruby? Pros and cons

Pros

None that we measure. Its Tilt of 100 is a full share of very little light.

Cons

Compared with the T73 Round Brilliant in ruby 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 ruby (white) against the T73 Round Brilliant in ruby (dashed): solid white where it reaches further, hatched where it falls short. Each pro and con is explained, with pictures, below.

Performance wheel: Old Single Cut in ruby, against the T73 Round Brilliant in ruby as an outline. Solid white marks where it reaches further, hatching where it falls short. The scores are listed below.50100Global−30Brilliance−58Fire−28Scintillation−36Spread−3Symmetry0Shape-norm−63Tilt+25

Against the T73 Round Brilliant in ruby: 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 ruby gains in an Old Single cut

We found no score where the Old Single beats the T73 in ruby or the same cut in diamond. Tilt sits at 100, the top of the scale, because a stone returning so little light has little to lose when it rocks. Its case is size and simplicity: in very small rubies, a point of red matters more than brilliance.

Why the Old Single struggles in ruby

Almost no fire at all

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

Fire 9, the lowest score on our ruby pages, against 84 for the eight cut in diamond. Weak dispersion meets weak light return: what little light comes back is barely split into colour.

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

Old Single Cut in ruby · Fire 9

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)

Old Single Cut in diamond · Fire 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: Corundum gives little fire in any cut; the most we measure in ruby is the Oval Cut Ruby's 74.

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

Little light back through the crown

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

Brilliance 36 against 94 for the T73 in ruby, the widest light gap on our ruby pages. Twenty-six facets cannot catch light from as many directions as a brilliant, and corundum's 34.6° critical angle lets much of what they miss escape.

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

Old Single Cut in ruby · Brilliance 36

T73 round brilliant in ruby 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 ruby · 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: Any modern round recovers most of it: in ruby, DG-M5 Ruby returns 100 and the T73 Round Brilliant Ruby 94.

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

More than half the light leaks

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

54% of the light in our census leaves through the pavilion, the highest share on our ruby pages; the T73 loses 5%.

Old Single Cut in ruby · Leakage 54

Old single cut in ruby tilted 0 degrees: Light Return map, 69% of the face leaking0° · 69% leak
Old single cut in ruby tilted 10 degrees: Light Return map, 48% of the face leaking10° · 48% leak
Old single cut in ruby tilted 20 degrees: Light Return map, 48% of the face leaking20° · 48% leak
Old single cut in ruby tilted 30 degrees: Light Return map, 53% of the face leaking30° · 53% leak

T73 Round Brilliant in ruby · Leakage 5

T73 round brilliant in ruby tilted 0 degrees: Light Return map, 1% of the face leaking0° · 1% leak
T73 round brilliant in ruby tilted 10 degrees: Light Return map, 10% of the face leaking10° · 10% leak
T73 round brilliant in ruby tilted 20 degrees: Light Return map, 29% of the face leaking20° · 29% leak
T73 round brilliant in ruby 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: Steepening will not help: at 48.48° the pavilion is already far above the 36.4° guide minimum. DG-M5 Ruby leaks 0%.

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

Slow, sparse flashes

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

Scintillation follows the facet count: 26 against 73 for the T73, so the sparkle comes in a few large blinks rather than a fine glitter.

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 eight-cut plan sets this, not the angles. For an antique ruby round with many more flashes, the Old European Cut Ruby scores 81.

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

Who an Old Single ruby suits

We would not cut a ruby of any size worth showing as an Old Single. It suits melee and accent rubies where a dot of red is all that is wanted, and period pieces that need the eight cut.

If it must be antique and round, the Old European Cut Ruby more than doubles the light, at 78. For any ruby meant to look bright, choose a modern round such as DG-Anteros Ruby.

Old Single Cut Ruby: questions

Is the Old Single a good cut for ruby?

Not if light matters: Brilliance 36 against 94 for the T73, with 54% leaking through the pavilion.

Why is an Old Single ruby so dark?

Few facets and a 34.6° critical angle: more than half the light escapes, 54% in our census against 19% for the same cut in diamond.

What does a 6.5 mm Old Single ruby weigh?

The deep eight cut comes to about 1.20 ct at 6.5 mm in ruby, 1.05 ct in diamond.

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

Ruby: optical properties and the top ten cuts · The Old Single Cut: specifications, model and files

Other cuts in ruby

The Old Single Cut in other gemstones