Octagon Cut Ruby: an even eight-sided face that keeps its light steady

Brilliance 78 · Fire 33 · Scintillation 66 · in our census, where the T73 scores 94 · 37 · 80 in ruby

Eight even sides and a stepped crown: in ruby the octagon returns more light than the diamond octagon, and much less fire.

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

Octagon Cut Ruby

On eight sides, the octagon repeats the hexagon's profile, with a stepped crown above and three pavilion tiers below. Its table spans 60.0% of the width, under a 39.8° crown, with a 29.3° pavilion and 49 facets in all.

In ruby its brilliance, 78, ties with the square and the Old European, and it is ahead of the hexagon, the Asscher and the emerald square.

Fire is where it falls furthest behind: 33 in ruby against 76 for the octagon in diamond.

Octagon cut ruby: a good choice? Pros and cons

Pros

None by our margins: Tilt 87, but on less light than the T73.

Cons

Compared with the T73 Round Brilliant in ruby and with the Octagon 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.

All eight scores against the T73

At a glance: the Octagon 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: Octagon 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−7Brilliance−16Fire−4Scintillation−14Spread0Symmetry0Shape-norm+1Tilt+12

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

  • Global72, the comparison 79, difference −7
  • Brilliance78, the comparison 94, difference −16
  • Fire33, the comparison 37, difference −4
  • Scintillation66, the comparison 80, difference −14
  • Spread100, the comparison 100, difference 0
  • Symmetry100, the comparison 100, difference 0
  • Shape-norm103, the comparison 102, difference +1
  • Tilt87, the comparison 75, difference +12
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

What ruby gains in an octagon cut

Two scores clear a baseline, Tilt and Brilliance, and neither ends up a pro. Its Tilt, 87, is above the T73's 75, but we count tilt as a pro only within five points of the T73's light, and 78 is not; the diamond octagon keeps more when tipped, 97. Against the diamond octagon the ruby returns more light, 78 to 71; each score counts once, where its gap is larger, so brilliance lands as a con. What the cut offers is an even, eight-sided face.

The octagon's costs in ruby

Under half the fire of a diamond octagon

Fire 33 against 76 for the Octagon Cut in diamond: 43 points lower

In ruby the octagon shows even less fire than the T73, 33 against 37: with dispersion this low, its broad, even facets have little to work with.

Octagon cut in ruby face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 33)

Octagon Cut in ruby · Fire 33

Octagon cut in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 76)

Octagon Cut in diamond · Fire 76

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: Among ruby cuts close to the T73's light, the Trilliant Cut Ruby gives the most fire, 52; DG-Anteros Ruby gives 43.

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

Less light than a round ruby

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

The pavilion is cut at 29.3°, under ruby's critical angle of 34.6°: light dropping straight through the 60.0% table can leave by the back. Even so, it keeps more than the hexagon, 64, on the same profile.

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

Octagon Cut in ruby · Brilliance 78

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: We have no measurements of a steeper octagon. For more light on a square footprint, the Cushion Cut Ruby returns 88.

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

A fifth of the light leaks

Leakage 20 against 5 for the T73 Round Brilliant in ruby: 15 points higher

20% of the light in our census exits through the pavilion; the T73 loses 5%, the diamond octagon 18%.

Octagon Cut in ruby · Leakage 20

Octagon cut in ruby tilted 0 degrees: Light Return map, 18% of the face leaking0° · 18% leak
Octagon cut in ruby tilted 10 degrees: Light Return map, 21% of the face leaking10° · 21% leak
Octagon cut in ruby tilted 20 degrees: Light Return map, 31% of the face leaking20° · 31% leak
Octagon cut in ruby tilted 30 degrees: Light Return map, 34% of the face leaking30° · 34% 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: A smaller octagon loses the same share. The Cushion Cut Ruby leaks 11%.

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

Fewer flashes than a round

Scintillation 66 against 80 for the T73 Round Brilliant in ruby: 14 points lower

Beyond the table, its facets sit in eight repeats round the stone, 49 in all against the T73's 73: a calmer pattern.

Octagon Cut · 49 facets · Scintillation 66

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 Square Cut Ruby scores 78, with the same brilliance as this cut.

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

Who an octagon ruby suits

The octagon suits a modern geometric design, or a coloured-stone ring where an even eight-sided face and steady light matter more than flashes of colour. Of the triangle, hexagon and octagon, it is the one with the most light.

For a square outline with more light, the Cushion Cut Ruby; for the same light with more sparkle, the Square Cut Ruby.

Octagon Cut Ruby: questions

Is an octagon cut good for ruby?

It returns 78 for brilliance, below the T73's 94, and holds it well when tilted. Its fire is low: 33, against 76 for the same cut in diamond.

Octagon ruby or octagon diamond?

The ruby returns more light face-up (78 against 71); the diamond has more than twice the fire (76 against 33).

Octagon or hexagon cut ruby?

The octagon, for light: 78 against 64, with 20% leakage against 24%. The hexagon has more fire, 45.

Get the Octagon Cut files

6 formatsMillimetresWatertight

Octagon Cut 3D files

The Octagon Cut as exact geometry: 49 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

Octagon Cut cutting files

The Octagon Cut as a faceting design: 41 + 8 girdles = 49 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 Octagon Cut: specifications, model and files

Other cuts in ruby

The Octagon Cut in other gemstones