Old European Cut Topaz: what our light census measures
Brilliance 70 · Fire 37 · Scintillation 81 · in our census, where the T73 scores 86 · 35 · 80 in topaz
How the Old European Cut handles light in topaz, measured: brilliance 70, fire 37 and 30% leakage, set against the T73 in the same stone and against the same cut in diamond.
Light Return map of the Old European Cut in topaz, face-up, from our own tracer at refractive index 1.606. Red, green and blue return light to the eye; gray leaks.
Old European Cut Topaz
Topaz has a refractive index of 1.606 to 1.644 and a dispersion of 0.014. Its critical angle, from the low end of that range, is 38.5°, so a round design needs a pavilion of at least 38.5° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.625, the midpoint of the published range, and a fire spread of 0.012, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 1.606, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the Old European Cut in topaz live.
The Old European Cut has 74 facets, a table of 45.0% of its width and a total depth of 64.7% of its width; its pavilion mains sit at 41.5°. In topaz, the census returns 70 of 100 for brilliance and 37 for fire, against 86 and 35 for the T73, our benchmark, in the same stone; the same Old European Cut in diamond reads 90 and 74.
Is topaz good in an Old European? Pros and cons, measured
Compared with the T73 Round Brilliant in topaz and with the Old European Cut in diamond.
A difference counts from 3 points (Brilliance, Fire, Tilt, Leakage), 5 (Scintillation,
Symmetry), 4% (face-up size per carat) 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 Old European Cut in topaz (white) against the T73 Round Brilliant in topaz (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 topaz: ahead on 4, level on 1, behind on 3.
Global71, the comparison 75, difference −4
Brilliance70, the comparison 86, difference −16
Fire37, the comparison 35, difference +2
Scintillation81, the comparison 80, difference +1
Spread98, the comparison 100, difference −2
Symmetry100, the comparison 100, difference 0
Shape-norm110, the comparison 92, difference +18
Tilt91, the comparison 74, difference +17
Face-up light census, a different measure from the Cut Grading Tool; Spread and Shape-norm above 100 sit on the ring. Spread is the census's estimate from depth alone; the face-up size in the pros and cons is measured from each model's outline. Open it in the Cut Performance Wheel; these are the same census figures as our Cut Performance Index.
What the Old European Cut gains in topaz
Against the T73 in topaz and the same cut in diamond, no figure of the Old European Cut is ahead by the thresholds above. Its figures are in the wheel and the FAQ; Topaz ranks every cut we score in topaz.
What the Old European Cut gives up in topaz
Less fire in topaz than in diamond
Fire 37 against 74 for the Old European Cut in diamond: 37 points lower
Fire is the share of the returned light that splits into color at the exit facet: the census traces each exit again at the refractive index minus and plus the fire spread (0.012 in topaz) and counts a ray as fire when the two directions differ by more than 0.6°. The Old European Cut reads 37 against 74 for the same cut in diamond. The figure is the census's; the 3D Gemstone Simulator renders topaz's fire live.
The fire figure is the census's, traced at the refractive index minus and plus the fire spread. See the fire in the 3D Gemstone Simulator: the Old European Cut in topaz under the sunny-day lighting.
What helps:the Oval Cut reads 68 for fire in topaz, the best of the cuts we score there.
Leakage 30 against 5 for the Old European Cut in diamond: 25 points higher
Leakage is the share of the census rays that enter the stone and leave through the pavilion, or through the crown heading down. The Old European Cut leaks 30% in topaz against 5% for the same cut in diamond. Grey in the maps below is leaking light; the share under each picture is that picture's own.
Old European Cut in topaz · Leakage 30
0° · 33% leak
10° · 40% leak
20° · 34% leak
30° · 47% leak
Old European Cut in diamond · Leakage 5
0° · 3% leak
10° · 7% leak
20° · 10% leak
30° · 17% leak
Each frame is the Light Return map with the stone tilted away from you by the angle shown; gray is leakage. The share under each frame is that picture's own.
What helps:the DG-M5 reads 4% for leakage in topaz, the best of the cuts we score there.
Brilliance 70 against 90 for the Old European Cut in diamond: 20 points lower
The same cut in diamond returns 90. Topaz bends light less than diamond: its critical angle is 38.5°, diamond's 24.4°, so a pavilion facet has to be steeper before light reflects off it rather than passing out. The Old European Cut's pavilion returns less of topaz's light than of diamond's, as the two maps show.
Old European Cut in topaz · Brilliance 70
Old European Cut in diamond · Brilliance 90
Red, green and blue = light returning to the eye; gray = leakage, light that leaves heading down or stays inside. This is the head-on view; the Brilliance score averages a wider cone of light, so the score can differ from what one picture shows.
What helps:the DG-M5 reads 96 for brilliance in topaz, the best of the cuts we score there.
Face-up size 95 against 100 for the T73 Round Brilliant in topaz (T73 = 100): 5% less face-up area for the same weight
Face-up size is the outline's area per carat, measured from each model (T73 = 100): 95 for the Old European Cut against 100 for the T73. The same volume spread over a longer or shallower outline shows more face for the weight; it is the same in every stone, because specific gravity scales every cut alike.
Old European Cut · 6.31 mm at 1.00 ct · Face-up size 95
T73 Round Brilliant · 6.47 mm at 1.00 ct · Face-up size 100
Both stones weigh 1.00 ct in topaz and are drawn to the same scale in millimeters, from each cut's own model. Face-up size is the outline's area per carat, with the T73 at 100: a deeper stone, or a rounder outline, spreads less area for its weight.
What helps:the Marquise Cut reads 121 for face-up size in topaz, the best of the cuts we score there.
Against the T73 in topaz and the same cut in diamond, no figure of the Old European Cut is ahead by our thresholds. The catch: it shows less fire than in diamond, leaks more than in diamond, returns less light than in diamond and faces up smaller for its weight.
If that catch matters more to you, the Oval Cut reads 68 for fire in topaz, the best of the cuts we score there.
Every figure on this page is from our light census, traced at one refractive index: a simulation of the geometry, not a grading report. The 3D files and cutting files below are the same Old European Cut model we traced.
Old European Cut Topaz: questions
Is the Old European a good cut for topaz?
In our census the Old European Cut returns 70 of 100 for brilliance and 37 for fire in topaz, against 86 and 35 for the T73 in the same stone. Against that round and against the same cut in diamond it has 0 pros and 4 cons by our thresholds; the summary above names them.
What pavilion angle does topaz need?
At least 38.5° for a round design: topaz's critical angle is 38.5°, from the low end of its refractive index range, and head-on light has to reflect off both sides of the pavilion and leave through the table. The Old European Cut's pavilion mains sit at 41.5°.
How much does a Old European weigh in topaz?
At 6.5 mm across, 1.09 ct in topaz, against 1.09 ct for the same cut in diamond, the same weight to the per cent: topaz's specific gravity is 3.535, diamond's 3.52.
Can I see the Old European in topaz in 3D?
Yes: the 3D Gemstone Simulator renders it live, with topaz's own refractive index and dispersion. Topaz is traced by the same light census as the other gemstones, with its refractive index and fire spread derived from published values, so its scores are on the same scale; the pictures here are our Light Return tracer, and the Cut Performance Wheel sets it against any other cut and stone.
Get the Old European Cut files
6 formatsMillimetersWatertight
Old European Cut 3D files
The Old European Cut as exact geometry: 74 planar facets, real-world scale, ready for CAD,
rendering, printing and casting.
Save with a bundle: the Old European Cut 3D and cutting files are also in Historic Cuts Complete, 6 cuts for €29.99 until 1 December, then €39.99 (€101.88 as single files). Buy the bundle.
Not sure the files open in your software? Get the cube free: the same six formats, for your email address, used only to send them (privacy).
