Old Mine Cut Chrysoberyl: what our light census measures
Brilliance 49 · Fire 31 · Scintillation 81 · in our census, where the T73 scores 94 · 29 · 80 in chrysoberyl
How the Old Mine Cut handles light in chrysoberyl, measured: brilliance 49, fire 31 and 50% leakage, set against the T73 in the same stone and against the same cut in diamond.
Light Return map of the Old Mine Cut in chrysoberyl, face-up, from our own tracer at refractive index 1.746. Red, green and blue return light to the eye; gray leaks.
Old Mine Cut Chrysoberyl
Chrysoberyl has a refractive index of 1.746 to 1.755 and a dispersion of 0.015. Its critical angle, from the low end of that range, is 34.9°, so a round design needs a pavilion of at least 36.3° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.751, the midpoint of the published range, and a fire spread of 0.013, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 1.746, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the Old Mine Cut in chrysoberyl live.
The Old Mine Cut has 74 facets, a table of 60.3% of its width and a total depth of 65.6% of its width; its pavilion mains sit at 44.4°. In chrysoberyl, the census returns 49 of 100 for brilliance and 31 for fire, against 94 and 29 for the T73, our benchmark, in the same stone; the same Old Mine Cut in diamond reads 59 and 72.
Is chrysoberyl good in an Old Mine? Pros and cons, measured
Compared with the T73 Round Brilliant in chrysoberyl and with the Old Mine 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 Mine Cut in chrysoberyl (white) against the T73 Round Brilliant in chrysoberyl (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 chrysoberyl: ahead on 3, behind on 5.
Global61, the comparison 77, difference −16
Brilliance49, the comparison 94, difference −45
Fire31, the comparison 29, difference +2
Scintillation81, the comparison 80, difference +1
Spread98, the comparison 100, difference −2
Symmetry90, the comparison 100, difference −10
Shape-norm77, the comparison 101, difference −24
Tilt100, the comparison 75, difference +25
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 Mine Cut gains in chrysoberyl
Against the T73 in chrysoberyl and the same cut in diamond, no figure of the Old Mine Cut is ahead by the thresholds above. Its figures are in the wheel and the FAQ; Chrysoberyl ranks every cut we score in chrysoberyl.
What the Old Mine Cut gives up in chrysoberyl
Returns less light than the T73 in chrysoberyl
Brilliance 49 against 94 for the T73 Round Brilliant in chrysoberyl: 45 points lower
Brilliance is the share of the 3,200 census rays that enter the stone and come back out of the crown towards the viewer. In chrysoberyl, whose critical angle is 34.9°, the Old Mine Cut returns 49 of 100 and the T73 94. The Old Mine Cut's pavilion mains sit at 44.4°, the T73's at 40.8°. The maps below show where each stone's light returns from and where it leaks.
Old Mine Cut in chrysoberyl · Brilliance 49
T73 Round Brilliant in chrysoberyl · Brilliance 94
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 100 for brilliance in chrysoberyl, the best of the cuts we score there.
Leakage 50 against 5 for the T73 Round Brilliant in chrysoberyl: 45 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 Mine Cut leaks 50% in chrysoberyl against 5% for the T73 in chrysoberyl. Grey in the maps below is leaking light; the share under each picture is that picture's own.
Old Mine Cut in chrysoberyl · Leakage 50
0° · 53% leak
10° · 46% leak
20° · 42% leak
30° · 38% leak
T73 Round Brilliant in chrysoberyl · Leakage 5
0° · 1% leak
10° · 11% leak
20° · 28% leak
30° · 30% 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 0% for leakage in chrysoberyl, the best of the cuts we score there.
Fire 31 against 72 for the Old Mine Cut in diamond: 41 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 (0.013 in chrysoberyl) and counts a ray as fire when the two directions differ by more than 0.6°. The Old Mine Cut reads 31 against 72 for the same cut in diamond. The figure is the census's; the 3D Gemstone Simulator renders chrysoberyl'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 Mine Cut in chrysoberyl under the sunny-day lighting.
What helps:the Oval Cut reads 67 for fire in chrysoberyl, the best of the cuts we score there.
Symmetry 90 against 100 for the T73 Round Brilliant in chrysoberyl: 10 points lower
Symmetry reads how evenly the pavilion facets of each design family are cut: 100 − 6 × their scatter in degrees. The Old Mine Cut reads 90, the T73 100. It depends on the geometry alone, so it is the same in every stone.
Old Mine Cut · 74 facets · Symmetry 90
T73 Round Brilliant · 73 facets · Symmetry 100
Symmetry scores how regular the pavilion facets are within the design. Compare how evenly the facets repeat around each pavilion. Drawn from each cut's own model.
Against the T73 in chrysoberyl and the same cut in diamond, no figure of the Old Mine Cut is ahead by our thresholds. The catch: it returns less light than the T73, leaks more light than the T73, shows less fire than in diamond and has a less regular pavilion than the T73.
If that catch matters more to you, the DG-M5 reads 100 for brilliance in chrysoberyl, 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 Mine Cut model we traced.
Old Mine Cut Chrysoberyl: questions
Is the Old Mine a good cut for chrysoberyl?
In our census the Old Mine Cut returns 49 of 100 for brilliance and 31 for fire in chrysoberyl, against 94 and 29 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 chrysoberyl need?
At least 36.3° for a round design: chrysoberyl's critical angle is 34.9°, 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 Mine Cut's pavilion mains sit at 44.4°.
How much does a Old Mine weigh in chrysoberyl?
At 6.5 mm across, 1.28 ct in chrysoberyl, against 1.21 ct for the same cut in diamond (+6%): chrysoberyl's specific gravity is 3.73, diamond's 3.52.
Can I see the Old Mine in chrysoberyl in 3D?
Yes: the 3D Gemstone Simulator renders it live, with chrysoberyl's own refractive index and dispersion. Chrysoberyl 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 Mine Cut files
6 formatsMillimetersWatertight
Old Mine Cut 3D files
The Old Mine Cut as exact geometry: 74 planar facets, real-world scale, ready for CAD,
rendering, printing and casting.
Save with a bundle: the Old Mine 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).
