Not the 57-facet stone in the shop window. Tolkowsky's 1919 angles taken to 185 facets: the hardest version of the ideal to beat.
Global score against Tolkowsky 1919, measured the same way in the same material.
Diamondn = 2.417+0.00Level
Moissaniten = 2.65+0.00Level
Cubic zirconian = 2.16+0.00Level
−2Tolkowsky 1919 = 0+2
The short version
This is the zero on every chart in the registry, and it is worth knowing exactly what it is: Marcel Tolkowsky's 1919 proportions, modelled at 185 facets rather than the 57 most people picture.
The distinction matters because facet count is the cheapest thing on this scale. Scoring house cuts against the 185-facet version rather than the 57 removes the easiest way to manufacture a margin. Three house cuts still finish ahead of it in diamond. One does in moissanite. None does in all three.
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
Level
91.65 against the standard's 91.65. The reference condition: the geometry solved for this refractive index, performing as designed. 2.17% leak and 92.6% useful light.
TermThis cut / standardPoints
Useful lightweight 0.3492.692.6+0.00
Fireweight 0.2078.778.7+0.00
Tiltweight 0.1692.592.5+0.00
Scintillationweight 0.1098.498.4+0.00
Symmetryweight 0.10100.0100.0+0.00
Leakweight 0.10 ↓2.172.17+0.00
Sum of the six terms+0.00
Published Global gap +0.00. The six terms reconstruct it to
0.00 of a point. The difference is rounding in the source figures, not a second method.
In moissanite n = 2.65
Level
92.86 against the standard's 92.86. The standard's weakest showing. Leak more than triples to 7.46% and useful light falls to 86.1: the gap BL-M5 was drawn to close.
TermThis cut / standardPoints
Useful lightweight 0.3486.186.1+0.00
Fireweight 0.2097.297.2+0.00
Tiltweight 0.1694.094.0+0.00
Scintillationweight 0.1098.498.4+0.00
Symmetryweight 0.10100.0100.0+0.00
Leakweight 0.10 ↓7.467.46+0.00
Sum of the six terms+0.00
Published Global gap +0.00. The six terms reconstruct it to
0.00 of a point. The difference is rounding in the source figures, not a second method.
In cubic zirconia n = 2.16
Level
94.59 against the standard's 94.59. Its cleanest material. 98.4% useful light and 0.58% leak, though three house cuts still finish above it.
TermThis cut / standardPoints
Useful lightweight 0.3498.498.4+0.00
Fireweight 0.2087.087.0+0.00
Tiltweight 0.1687.187.1+0.00
Scintillationweight 0.1098.498.4+0.00
Symmetryweight 0.10100.0100.0+0.00
Leakweight 0.10 ↓0.580.58+0.00
Sum of the six terms+0.00
Published Global gap +0.00. The six terms reconstruct it to
0.00 of a point. The difference is rounding in the source figures, not a second method.
What it's doing
The registry carries the same 1919 design three times: at 57 facets with the girdle left as a knife edge, at 73 with the girdle faceted, and at 185. Across those three the optical terms barely move: useful light travels 0.6 points, fire 0.5, leak 0.3. Scintillation travels 26.6, from 71.8 to 98.4.
Of the 3.04-point Global gap between the 57-facet stone and this standard, 2.66 points (87% of it) is the scintillation term alone. Between the 73-facet version and this one, every term except scintillation nets to zero to within a hundredth of a point.
That is the most useful single fact in the registry, and it cuts against the house cuts as much as for them: facets are cheap points. It is also why the standard is set at 185 rather than 57. Any margin a house cut holds over this line had to be won on angles, because the facet lever has already been pulled.
Where it gives ground
It is a diamond solution, and it shows outside diamond. At n = 2.65 the same pavilion leaks 7.46% and useful light falls to 86.1, which is why a cut designed for that index can take 2.27 points off it.
Tolkowsky solved for the material in front of him in 1919. Moissanite did not reach the jewellery trade until the late 1990s.
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
This cut is the benchmark. Every figure in the registry is measured against it.