The reference stone: the one most people already own.
The 1919 ideal as the trade actually cuts it, and 3.04 points behind the same design at 185 facets.
Global score against Tolkowsky 1919, measured the same way in the same material.
Diamondn = 2.417−3.04Behind
Moissaniten = 2.65−3.04Behind
Cubic zirconian = 2.16−2.82Behind
−4Tolkowsky 1919 = 0+4
The short version
Tolkowsky 57 is the round brilliant as it is cut in practice: 57 facets, girdle left as a knife edge. In the registry it is a control, not a house cut, and it finishes below the 185-facet standard in all three materials.
Read where the gap comes from before reading it as a weak stone. Useful light (92.3 in diamond) and leak (1.88%) are within a whisker of the standard's. What it lacks is sparkle density.
The ledger
Where the points come from
Global is a weighted sum of six terms. Subtract the standard's figure from this cut's,
term by term, and the six differences add back up to the published gap. Nothing is hidden in the total,
so you can see exactly which part of the stone is doing the work.
In diamond n = 2.417
Behind
88.61 against the standard's 91.65. 2.66 of the 3.04-point gap is scintillation. Everything else together comes to 0.39, and 0.34 of that is tilt.
TermThis cut / standardPoints
Useful lightweight 0.3492.392.6−0.10
Fireweight 0.2078.878.7+0.02
Tiltweight 0.1690.492.5−0.34
Scintillationweight 0.1071.898.4−2.66
Symmetryweight 0.10100.0100.0+0.00
Leakweight 0.10 ↓1.882.17+0.03
Sum of the six terms−3.05
Published Global gap −3.04. The six terms reconstruct it to
0.01 of a point. The difference is rounding in the source figures, not a second method.
In moissanite n = 2.65
Behind
89.82 against the standard's 92.86. 97.5 points of fire, second in the registry only to BL-M5's 99.6, and still 3.04 points behind the standard, because the entire gap lives in sparkle density.
TermThis cut / standardPoints
Useful lightweight 0.3485.386.1−0.27
Fireweight 0.2097.597.2+0.06
Tiltweight 0.1693.294.0−0.13
Scintillationweight 0.1071.898.4−2.66
Symmetryweight 0.10100.0100.0+0.00
Leakweight 0.10 ↓7.767.46−0.03
Sum of the six terms−3.03
Published Global gap −3.04. The six terms reconstruct it to
0.01 of a point. The difference is rounding in the source figures, not a second method.
In cubic zirconia n = 2.16
Behind
91.77 against the standard's 94.59. Leak is fractionally cleaner than the standard's (0.51% against 0.58%) and useful light fractionally lower (98.0 against 98.4). Optically a coin toss; 2.66 points of scintillation decide it.
TermThis cut / standardPoints
Useful lightweight 0.3498.098.4−0.14
Fireweight 0.2086.887.0−0.04
Tiltweight 0.1687.187.1+0.00
Scintillationweight 0.1071.898.4−2.66
Symmetryweight 0.10100.0100.0+0.00
Leakweight 0.10 ↓0.510.58+0.01
Sum of the six terms−2.83
Published Global gap −2.82. The six terms reconstruct it to
0.01 of a point. The difference is rounding in the source figures, not a second method.
What it's doing
Of its 3.04-point deficit in diamond, 2.66 is scintillation: 71.8 against 98.4, the lowest figure in the registry. It has 128 fewer facets to sparkle with.
Strip the scintillation term out and the two stones are separated by 0.39 of a point. Same angles, same job, doing it about equally well. The Global scale is not saying this is a poorly performing stone; it is saying it produces fewer distinct flashes per unit of movement, which is exactly what a knife-edge girdle at 57 facets should produce.
Where it gives ground
Tilt is the one real optical difference: 90.4 against 92.5, the lowest of the three Tolkowskys in diamond.
And at 57 facets there is no route to a higher scintillation figure. The deficit is structural rather than a matter of finishing, which is precisely why it makes a good control.
How to read this
The protocol
Monte-Carlo ray census on exact facet geometry: 3,200 rays face-up plus 2,200 at
20° tilt, cosine-weighted from a 7° near-vertical cone. Every cut is scored against Tolkowsky's 1919 ideal,
measured the same way in the same material.
These are engine estimates, ± 2 points, not lab-certified grades.
A lead of under half a point sits inside the engine's resolution, so we don't claim it as a win. A deficit is reported as a deficit, however small.
Symmetry
Reads 100 for every cut, because each is modelled from exact geometry rather than
a finished stone. It contributes nothing to any comparison here: it cancels, and we show the row anyway.
The rest of the registry
Behind the standard in all three materials. Read the decomposition for why.