T105 Round Brilliant Sapphire: Pros & Cons

The T105 keeps the T57's main angles and adds 48 facets, cut a little steeper: eight star halves on the crown, and three rows of lower halves on the pavilion where the T57 has one, with eight pavilion star halves at the girdle. There is no girdle band: the crown runs straight into the pavilion at a knife edge.

The model stands 59.3% deep on a 40.75° pavilion. In sapphire the extra facets raise the sparkle score, while light slips a few points under the T73 and twice as much leaks: 10% against 5%.

Is the T105 a good round for sapphire? Pros and cons

Pros

More sparkle than the T73 90 vs 80

Cons

Fire at under half the diamond figure 36 vs 77
Heavier than a diamond of its size 1.04 vs 0.92 ct
Less light kept when tipped than in diamond 78 vs 87
Twice the T73's leakage 10 vs 1

Compared with the T73 Round Brilliant in sapphire 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 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 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 a sapphire gains in the T105

More sparkle than the T73

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

105 facets against 73, with most of the extra division on the pavilion. In a blue sapphire that breaks the colour into smaller, quicker points as the stone moves.

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

Where the T105 costs a sapphire

Fire at under half the diamond figure

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

The same T105 scores 77 in diamond and 36 here. Adding facets does not add dispersion.

T105 round brilliant in sapphire 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: No facet count fixes it. The Oval Cut Sapphire scores 74 in sapphire, the most we measure.

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

Heavier than a diamond of its size

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

Sapphire puts 1.04 ct into a 6.5 mm T105; diamond, 0.92 ct. With no girdle band it is still among the lightest of our rounds at that width.

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

What helps: Order by millimetres; a 6.5 mm T105 is 1.04 ct.

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

Less light kept when tipped than in diamond

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

Tilted 20°, it keeps 78 of its face-up light against 87 for the diamond version.

T105 round brilliant in sapphire 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 sapphire 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: In sapphire, DG-Miliano Sapphire keeps 83 of its light when tipped and sparkles more, at 98.

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

Twice the T73's leakage

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

10% of the light leaves through the pavilion in our census, against 5% for the T73 in sapphire and 1% for the T105 in diamond. The mains sit at 40.75°, above sapphire's 36.4° guide minimum, so a shallow main angle is not the explanation.

What helps: Steepening the mains is not the answer at 40.75°. The T73 Round Brilliant Sapphire loses 5% in sapphire and DG-M5 Sapphire 0%.

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

Who a T105 sapphire suits

The T105 suits a sapphire cutter who wants more sparkle on the classic angles and can protect a knife edge. Sapphire's hardness of 9 resists scratches, but an exposed knife-edge girdle can still chip.

For a seated girdle and half the leakage, the T73 Round Brilliant Sapphire. For finer sparkle still, with the T73's light, DG-Vitruvio Sapphire.

If the rough is colour-zoned, a busy pavilion like this one can help mix bands of blue and colourless into a more even face-up colour.

T105 Round Brilliant Sapphire: questions

Is a T105 round brilliant good for sapphire?

It sparkles more than the T73 (90 against 80) but returns a little less light (90 against 94) and leaks 10%.

T105 or T73 for a sapphire?

The T73 for light and a girdle a setter can seat; the T105 for sparkle. Their fire is level: 36 against 37.

What does a 6.5 mm T105 sapphire weigh?

About 1.04 ct; in diamond, 0.92 ct.

Does a T105 sapphire need a protective setting?

Yes, for the knife-edge girdle: a bezel or a full rim of prongs shields it.

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

Sapphire: optical properties and the top ten cuts · The T105 Round Brilliant: specifications, model and files

T105 Round Brilliant Sapphire: 48 more facets, and more sparkle than the T73