House cut · 193 facets · Registry 21 July 2026
The fire cut.
1.40 points ahead of the 1919 ideal in diamond, and 1.34 of that is fire.
Global score against Tolkowsky 1919, measured the same way in the same material.
−2Tolkowsky 1919 = 0+2
The short version
Cinderella is the most single-minded of the house diamond cuts. It carries 85.4 points of fire against the standard's 78.7, the highest diamond figure in the registry, and almost the whole of its 1.40-point margin comes from that one term.
It pays for it in leak: 4.42% against 2.17%. If you want coloured flash rather than white brightness, that is the trade, made deliberately, and on the record.
The ledger
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.
Ahead 93.05 against the standard's 91.65. One term carries the result. Fire contributes +1.34 of the +1.40; every other term nets to +0.06 after the leak penalty is paid.
Published Global gap +1.40. The six terms reconstruct it to 0.00 of a point. The difference is rounding in the source figures, not a second method.
Behind 91.62 against the standard's 92.86. Behind on brightness (84.0 is the lowest useful-light figure anywhere in the registry) and, unusually for this cut, behind on fire as well, at 93.0 against 97.2. Only tilt is in its favour.
Published Global gap −1.24. The six terms reconstruct it to 0.01 of a point. The difference is rounding in the source figures, not a second method.
Level 95.01 against the standard's 94.59. Fire lifts again (+0.92, and 91.6 tops the cubic zirconia column) but tilt hands 0.30 back at 85.2, the lowest tilt figure in that column. Net +0.42: level, not a win.
Published Global gap +0.42. The six terms reconstruct it to 0.02 of a point. The difference is rounding in the source figures, not a second method.
What it's doing
The ledger is unusually lopsided. Useful light barely moves (93.1 against 92.6, worth 0.17). Tilt is fractionally better. Scintillation is a rounding difference. What Cinderella does is take dispersion up 6.7 points and accept the consequence: light that travels further inside the stone before it returns is light that more often doesn't return at all.
Two and a quarter points of extra leakage cost it 0.23 of Global. The fire it bought returned 1.34. On a scale that weights fire at 0.20 and retained light at 0.10, that trade pays, and it is the clearest example in the registry of a cut being engineered for one visual effect rather than an average.
Where it gives ground
Leak, and moissanite. At 4.42% it holds less light than the standard, than Miliano, or than either Tolkowsky reference.
And the geometry that buys fire in diamond stops buying it at n = 2.65: in moissanite Cinderella returns less fire than the standard does (93.0 against 97.2) and finishes 1.24 points behind. The trade only works in the material it was drawn for.
How to read this
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.
Global = 0.34 useful + 0.20 fire + 0.16 tilt + 0.10 scintillation + 0.10 symmetry + 0.10 (100 − leak).
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.
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