T105 Round Brilliant Ruby: Pros & Cons

Take the T57, keep its main angles (40.75° on the pavilion), and add 48 facets: eight star halves on the crown, two extra rows of lower halves and eight pavilion star halves at the girdle. Our 105-facet model is 59.3% deep, with no girdle band at all.

In ruby the added facets do what they are for: scintillation rises clearly. They also cost a little: Brilliance 90 against 94 for the T73, and twice its leakage. Against the same cut in diamond the costs are fire, tilt and more leakage still.

Without a girdle band it is also one of the lightest rounds for its width on our ruby pages, level with the T57.

Should a ruby be cut as a T105? Pros and cons

Pros

Finer sparkle than the T73 90 vs 80

Cons

Under half the fire of a diamond T105 36 vs 77
Heavier than the same size in diamond 1.04 vs 0.92 ct
Darkens more when tipped than in diamond 78 vs 87
Far more leakage than in diamond 10 vs 1

Compared with the T73 Round Brilliant in ruby and with the T105 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 T73

At a glance: the T105 Round Brilliant 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.

Against the T73 Round Brilliant in ruby: ahead on 3, level on 1, behind on 4.

Global78, the comparison 79, difference −1
Brilliance90, the comparison 94, difference −4
Fire36, the comparison 37, difference −1
Scintillation90, the comparison 80, difference +10
Spread101, the comparison 100, difference +1
Symmetry100, the comparison 100, difference 0
Shape-norm97, the comparison 102, difference −5
Tilt78, the comparison 75, difference +3

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 T105

Finer sparkle than the T73

Scintillation 90 against 80 for the T73 Round Brilliant in ruby: 10 points higher

Our scintillation score is built from the facet plan, and 105 facets divide the face more finely than 73. The added rows of lower halves are where most of the new flashes come from.

T105 Round Brilliant · 105 facets · Scintillation 90

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.

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

The T105's costs in ruby

Under half the fire of a diamond T105

Fire 36 against 77 for the T105 Round Brilliant in diamond: 41 points lower

Fire 36 in ruby, 77 in diamond. Extra facets cannot make up for a dispersion of 0.018; they divide the little colour there is into smaller pieces.

T105 round brilliant in ruby face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 36) — 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.

T105 round brilliant in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 77) — 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: Dividing the crown further cannot raise corundum's dispersion. A ruby meant to flash colour is better as an Oval Cut Ruby, at 74.

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

Heavier than the same size in diamond

1.04 ct at 6.5 mm, against 0.92 ct for the same cut in diamond (+14%)

The knife-edge model is light for a round, 1.04 ct at 6.5 mm in ruby; in diamond the same outline is 0.92 ct.

A T105 Round Brilliant 6.5 mm across, weighed from the model's measured volume and each stone's specific gravity.

What helps: Choose by width; the knife edge already makes this one of the lighter rounds for its size.

Try it yourself: Weights in all seven gemstones on the T105 Round Brilliant page

Darkens more when tipped than in diamond

Tilt 78 against 87 for the T105 Round Brilliant in diamond: 9 points lower

Rocked by 20°, the ruby keeps 78 of its face-up light, the diamond 87. The T105's extra facets do not change how corundum's wider escape cone behaves.

T105 round brilliant in ruby tilted 0 degrees: Light Return map, 12% of the face leaking — 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.

T105 round brilliant in ruby tilted 10 degrees: Light Return map, 10% of the face leaking — 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: For a fine-sparkling ruby round that also holds up at an angle, DG-Miliano Ruby keeps 83.

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

Far more leakage than in diamond

Leakage 10 against 1 for the T105 Round Brilliant in diamond: 9 points higher

10% of the light leaves through the pavilion in our ruby census, 1% in diamond. The slightly steeper added facets help diamond more than corundum, whose critical angle is 34.6°.

What helps: No size changes the share. Going back to the 73-facet plan cuts it: the T73 Round Brilliant Ruby leaks 5% in ruby, DG-M5 Ruby 0%.

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

Who a T105 ruby suits

The T105 suits a round ruby where finer sparkle than the T73 is wanted and the setting will protect a knife-edge girdle, such as a full bezel. Expect a few points less light.

If you want both sparkle and the T73's light, DG-Vitruvio Ruby scores 98 with 94 brilliance. If the ruby is going into prongs and needs a faceted girdle band, choose the T73 Round Brilliant Ruby.

T105 Round Brilliant Ruby: questions

Does a T105 ruby sparkle more than a T73?

Yes: Scintillation 90 against 80.

Is a T105 ruby less bright than a T73?

A few points less, 90 against 94, and it lets 10% of the light out of the back where the T73 lets out 5%.

Is a knife-edge girdle safe on a ruby?

Ruby is hard, 9 on the Mohs scale, but a knife edge is thin at any hardness and chips more easily than a faceted girdle. Our cut notes advise a protective setting for exactly that reason.

What does a 6.5 mm T105 ruby weigh?

Lighter than a T73 of the same width: about 1.04 ct in ruby, 0.92 ct in diamond.

Get the T105 Round Brilliant Cut files

6 formatsMillimetresWatertight

T105 Round Brilliant Cut 3D files

The T105 Round Brilliant Cut as exact geometry: 105 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

T105 Round Brilliant Cut cutting files

The T105 Round Brilliant Cut as a faceting design: 105 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 T105 Round Brilliant: specifications, model and files

T105 Round Brilliant Ruby: more sparkle than the T73, on a knife-edge girdle