Brilliance 81 · Fire 67 · Scintillation 80 · in our census, where the T73 scores 72 · 58 · 80 in iolite
How the DG-Anteros handles light in iolite, measured: brilliance 81, fire 67 and 19% leakage, set against the T73 in the same stone and against the same cut in diamond.
Iolite has a refractive index of 1.542 to 1.551 and a dispersion of 0.017. Its critical angle, from the low end of that range, is 40.4°, so a round design needs a pavilion of at least 40.4° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.547, the midpoint of the published range, and a fire spread of 0.015, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 1.542, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the DG-Anteros in iolite live.
The DG-Anteros has 73 facets, a table of 53.5% of its width and a total depth of 59.4% of its width; its pavilion mains sit at 40.1°. In iolite, the census returns 81 of 100 for brilliance and 67 for fire, against 72 and 58 for the T73, our benchmark, in the same stone; the same DG-Anteros in diamond reads 95 and 74.
Compared with the T73 Round Brilliant in iolite and with the DG-Anteros 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.
At a glance: the DG-Anteros in iolite (white) against the T73 Round Brilliant in iolite (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 iolite: ahead on 5, level on 2, behind on 1.
0.72 ct at 6.5 mm, against 0.97 ct for the same cut in diamond (−26%)
Weight follows specific gravity: 2.61 for iolite against 3.52 for diamond, so the same model at the same size weighs 0.72 ct here and 0.97 ct in diamond, 6.5 mm across. Nothing about the light changes with it.
Try it yourself: Weights in every gemstone on the DG-Anteros page
Fire 67 against 58 for the T73 Round Brilliant in iolite: 9 points higher
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 (0.015 in iolite) and counts a ray as fire when the two directions differ by more than 0.6°. The DG-Anteros reads 67 against 58 for the T73 in iolite. The figure is the census's; the 3D Gemstone Simulator renders iolite'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 DG-Anteros in iolite under the sunny-day lighting.
Tilt 68 against 85 for the DG-Anteros in diamond: 17 points lower
Tilt is how much of its face-up brilliance a stone keeps when the census tilts it 20° about its long axis, with 2,200 rays. The DG-Anteros keeps 68 against 85 for the same cut in diamond. The tilt strips below show the maps at 0°, 10°, 20° and 30°, with each picture's own leak share under it.
DG-Anteros in iolite · Tilt 68
DG-Anteros in diamond · Tilt 85
What helps: the T105 Round Brilliant reads 87 for tilt in iolite, the best of the cuts we score there.
Try it yourself: Compare the Tilt spoke in the Cut Performance Wheel
Leakage 19 against 2 for the DG-Anteros in diamond: 17 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 DG-Anteros leaks 19% in iolite against 2% for the same cut in diamond. Grey in the maps below is leaking light; the share under each picture is that picture's own.
DG-Anteros in iolite · Leakage 19
DG-Anteros in diamond · Leakage 2
What helps: the DG-M5 reads 15% for leakage in iolite, the best of the cuts we score there.
Try it yourself: Tilt it yourself in the simulator's light map
Brilliance 81 against 95 for the DG-Anteros in diamond: 14 points lower
The same cut in diamond returns 95. Iolite bends light less than diamond: its critical angle is 40.4°, diamond's 24.4°, so a pavilion facet has to be steeper before light reflects off it rather than passing out. The DG-Anteros's pavilion returns less of iolite's light than of diamond's, as the two maps show.
DG-Anteros in iolite · Brilliance 81
DG-Anteros in diamond · Brilliance 95
What helps: the DG-M5 reads 85 for brilliance in iolite, the best of the cuts we score there.
Try it yourself: Open this Light Return map in the simulator
Pick the DG-Anteros in iolite for this: it weighs less than in diamond and shows more fire than the T73. The catch: it loses more light when tilted than in diamond, leaks more than in diamond and returns less light than in diamond.
If that catch matters more to you, the T105 Round Brilliant reads 87 for tilt in iolite, 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 DG-Anteros model we traced.
In our census the DG-Anteros returns 81 of 100 for brilliance and 67 for fire in iolite, against 72 and 58 for the T73 in the same stone. Against that round and against the same cut in diamond it has 2 pros and 3 cons by our thresholds; the summary above names them.
At least 40.4° for a round design: iolite's critical angle is 40.4°, 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 DG-Anteros's pavilion mains sit at 40.1°.
At 6.5 mm across, 0.72 ct in iolite, against 0.97 ct for the same cut in diamond (-26%): iolite's specific gravity is 2.61, diamond's 3.52.
Yes: the 3D Gemstone Simulator renders it live, with iolite's own refractive index and dispersion. Iolite 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.
The DG-Anteros Cut as exact geometry: 73 planar facets, real-world scale, ready for CAD, rendering, printing and casting.
The DG-Anteros Cut as a faceting design: 57 + 16 girdles = 73 facets, 96 index, 8-fold mirror-image symmetry, ready for the machine.
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).
Questions before you buy? Email us.
Iolite: optical properties and the top ten cuts · The DG-Anteros: specifications, model and files