T73 Round Brilliant Ruby: the benchmark round, with more sparkle than the T57

Brilliance 94 · Fire 37 · Scintillation 80 · in our census, where the T57 scores 94 · 39 · 72 in ruby

Our benchmark round, in ruby. Against its 1919 parent, the T57, the girdle band adds sparkle and costs nothing in light.

See it in the simulatorGet the files
The T73 Round Brilliant in ruby, rendered at an angle in our 3D Gemstone Simulator under studio light
Rendered in our 3D Gemstone Simulator from the T73 Round Brilliant model, 1.00 ct, studio light.

T73 Round Brilliant Ruby

The T73 is the 1919 round brilliant with a sixteen-facet girdle band: 73 facets, a 40.75° pavilion and a depth of 61.7%. Every other ruby round on this site is measured against it; on this page we set it against the T57 instead, the same plan without the girdle facets.

In ruby the two return the same light, Brilliance 94 each, and the T73 sparkles more. The cons all come from comparing ruby with diamond in the same cut: less fire, less light kept when tilted, more weight and a little more leakage.

Most rubies are not cut round at all; ovals and cushions keep more of the flat, hexagonal rough. When a ruby is cut round, this is the plan most cutters reach for.

How good is a T73 round ruby? Pros and cons

Pros

Cons

Compared with the T57 Round Brilliant in ruby and with the T73 Round Brilliant 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 T57

At a glance: the T73 Round Brilliant in ruby (white) against the T57 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: T73 Round Brilliant in ruby, against the T57 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+1Brilliance0Fire−2Scintillation+8Spread−1Symmetry0Shape-norm+1Tilt+1

Against the T57 Round Brilliant in ruby: ahead on 4, level on 2, behind on 2.

  • Global79, the comparison 78, difference +1
  • Brilliance94, the comparison 94, difference 0
  • Fire37, the comparison 39, difference −2
  • Scintillation80, the comparison 72, difference +8
  • Spread100, the comparison 101, difference −1
  • Symmetry100, the comparison 100, difference 0
  • Shape-norm102, the comparison 101, difference +1
  • Tilt75, the comparison 74, difference +1
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 a T73

More sparkle than the T57

Scintillation 80 against 72 for the T57 Round Brilliant in ruby: 8 points higher

Sixteen girdle facets bring the count from 57 to 73, and our scintillation score follows the facet plan. The crown and pavilion are unchanged, so the light behind the sparkle is the same.

T73 Round Brilliant · 73 facets · Scintillation 80

T57 Round Brilliant · 57 facets · Scintillation 72

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.

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

Where the T73 costs a ruby

Far less fire than a diamond T73

Fire 37 against 78 for the T73 Round Brilliant in diamond: 41 points lower

Fire falls from 78 in diamond to 37 in ruby across identical facets. Corundum's 0.018 dispersion leaves little colour to split out, and the 1919 angles cannot add more.

T73 round brilliant in ruby face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 37)

T73 Round Brilliant in ruby · Fire 37

T73 round brilliant in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 78)

T73 Round Brilliant in diamond · Fire 78

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: No round fixes this in ruby. Stretch the plan into an Oval Cut Ruby and fire reaches 74, the most colourful ruby we measure.

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

Holds less light at an angle than in diamond

Tilt 75 against 92 for the T73 Round Brilliant in diamond: 17 points lower

At a 20° tilt the ruby keeps 75 of its face-up light and the diamond 92. The 1919 angles were worked out for diamond, whose critical angle is 24.4°; ruby's is 34.6°, and rocking the stone finds the difference.

T73 Round Brilliant in ruby · Tilt 75

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

T73 Round Brilliant in diamond · Tilt 92

T73 round brilliant in diamond tilted 0 degrees: Light Return map, 4% of the face leaking0° · 4% leak
T73 round brilliant in diamond tilted 10 degrees: Light Return map, 2% of the face leaking10° · 2% leak
T73 round brilliant in diamond tilted 20 degrees: Light Return map, 9% of the face leaking20° · 9% leak
T73 round brilliant in diamond tilted 30 degrees: Light Return map, 14% of the face leaking30° · 14% leak
Tilt is how much of its own face-up light a stone keeps when tilted. 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: DG-Miliano Ruby keeps 83 at 20° in ruby, giving up a few points of brilliance.

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

Heavier than diamond

1.15 ct at 6.5 mm, against 1.01 ct for the same cut in diamond (+14%)

Same outline, denser stone: a 6.5 mm T73 is 1.15 ct in ruby and 1.01 ct in diamond.

Ruby1.15 ctDiamond1.01 ct
A T73 Round Brilliant 6.5 mm across, weighed from the model's measured volume and each stone's specific gravity.

What helps: Calibrated round settings are sized in millimetres, so order a T73 ruby that way.

Try it yourself: Weights in all seven gemstones on the T73 Round Brilliant page

A little more leakage than in diamond

Leakage 5 against 2 for the T73 Round Brilliant in diamond: 3 points higher

5% against 2%: small in both, and among the lowest on our ruby pages. DG-M5 and DG-Anteros are the only ruby cuts we measure that leak less.

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

T73 Round Brilliant in diamond · Leakage 2

T73 round brilliant in diamond tilted 0 degrees: Light Return map, 4% of the face leaking0° · 4% leak
T73 round brilliant in diamond tilted 10 degrees: Light Return map, 2% of the face leaking10° · 2% leak
T73 round brilliant in diamond tilted 20 degrees: Light Return map, 9% of the face leaking20° · 9% leak
T73 round brilliant in diamond tilted 30 degrees: Light Return map, 14% of the face leaking30° · 14% 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: DG-M5 Ruby leaks 0% in ruby. Size does not move the share.

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

Who a T73 ruby suits

Choose the T73 for a round ruby with proportions any cutter or setter will recognise, a girdle that seats in a standard setting, and light within a few points of the best we measure.

Two rounds return more light in ruby: DG-M5 Ruby and DG-Anteros Ruby. DG-Vitruvio gives finer sparkle at identical light: DG-Vitruvio Ruby. For colour flashes, look beyond rounds: the Oval Cut Ruby has twice the T73's fire in ruby.

If you are cutting, ruby's dichroism makes orientation the first decision: a table across the c-axis shows the purplish-red ray, one along it the orangier ray.

T73 Round Brilliant Ruby: questions

Is the T73 a good cut for ruby?

A sound one, and the reference for every round on our ruby pages: Brilliance 94, 5% leakage. DG-M5 and DG-Anteros edge past it, at 100 and 97.

T73 or T57 for a ruby?

They return the same light; the T73 sparkles more (80 against 72) and has a girdle a setter can seat.

Does a round ruby have fire?

Not much. Our T73 in ruby scores 37 for fire; the same round in diamond, 78.

What does a 6.5 mm round ruby weigh?

A T73 ruby 6.5 mm across is about 1.15 ct; the diamond equivalent, 1.01 ct.

Get the T73 Round Brilliant Cut files

6 formatsMillimetresWatertight

T73 Round Brilliant Cut 3D files

The T73 Round Brilliant Cut as exact geometry: 73 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

T73 Round Brilliant Cut cutting files

The T73 Round Brilliant Cut as a faceting design: 57 + 16 girdles = 73 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 T73 Round Brilliant: specifications, model and files

Other cuts in ruby

The T73 Round Brilliant in other gemstones