The 1919 angles at 185 facets, and the cleanest demonstration in the registry of what facet count alone is worth.
Global score against T57, Tolkowsky’s 1919 ideal, measured the same way in the same material.
Diamondn = 2.417+3.04Ahead
Moissaniten = 2.65+3.04Ahead
Cubic zirconian = 2.16+2.82Ahead
−6T57 = 0+6
The short version
T185 is Marcel Tolkowsky’s 1919 proportions modelled at 185 facets rather than the 57 he specified. Same table, same crown, same pavilion. Only the facet pattern changes.
That makes it the control for the whole registry. It finishes 3.04 points above the standard in diamond, and 2.66 of those points, 87% of the margin, is scintillation. Everything else nets to +0.38. If you want to know what a facet count is worth on this scale and what it is not, this is the row to read.
The full account of what Tolkowsky calculated, and what each cut in the T-series changes about it, is on the 1919 ideal.
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
Ahead
91.65 against the standard's 88.61. Of the +3.04, scintillation is +2.66. Useful light moves +0.10, fire −0.02, tilt +0.34 and leak −0.03. The optics are the same stone; the sparkle density is not.
TermThis cut / standardPoints
Useful lightweight 0.3492.692.3+0.10
Fireweight 0.2078.778.8−0.02
Tiltweight 0.1692.590.4+0.34
Scintillationweight 0.1098.471.8+2.66
Symmetryweight 0.10100.0100.0+0.00
Leakweight 0.10 ↓2.171.88−0.03
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
Ahead
92.86 against the standard's 89.82, an identical +3.04 at a different index, and again +2.66 of it is scintillation. Leak nearly matches the standard's at 7.46% against 7.76%.
TermThis cut / standardPoints
Useful lightweight 0.3486.185.3+0.27
Fireweight 0.2097.297.5−0.06
Tiltweight 0.1694.093.2+0.13
Scintillationweight 0.1098.471.8+2.66
Symmetryweight 0.10100.0100.0+0.00
Leakweight 0.10 ↓7.467.76+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
Ahead
94.59 against the standard's 91.77. The pattern holds a third time: +2.66 of the +2.82 is scintillation, and tilt lands level to the decimal.
TermThis cut / standardPoints
Useful lightweight 0.3498.498.0+0.14
Fireweight 0.2087.086.8+0.04
Tiltweight 0.1687.187.1+0.00
Scintillationweight 0.1098.471.8+2.66
Symmetryweight 0.10100.0100.0+0.00
Leakweight 0.10 ↓0.580.51−0.01
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
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 gap between the standard and this stone, 2.66 points, 87% of it, is the scintillation term alone. Everything else nets to +0.38. This row is the price list for facet count, and every other margin in the registry should be read against it.
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 BL-M5, drawn for that index, finishes 2.27 points above it there.
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.