Brilliance 63 · Fire 48 · Scintillation 60 · in our census, where the T73 scores 86 · 50 · 80 in tourmaline
How the DG-Octagonal Kite handles light in tourmaline, measured: brilliance 63, fire 48 and 37% leakage, set against the T73 in the same stone and against the same cut in diamond.
Tourmaline has a refractive index of 1.603 to 1.655 and a dispersion of 0.017. Its critical angle, from the low end of that range, is 38.6°, so a round design needs a pavilion of at least 38.6° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.629, 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 1.603, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the DG-Octagonal Kite in tourmaline live. Tourmaline is strongly doubly refractive (birefringence up to 0.040), so its back facets can look doubled. Our census traces one index (1.629), so the doubling is not in these figures.
The DG-Octagonal Kite has 41 facets, a table of 55.0% of its width and a total depth of 70.0% of its width; its pavilion mains sit at 43.0°. In tourmaline, the census returns 63 of 100 for brilliance and 48 for fire, against 86 and 50 for the T73, our benchmark, in the same stone; the same DG-Octagonal Kite in diamond reads 88 and 82.
Compared with the T73 Round Brilliant in tourmaline and with the DG-Octagonal Kite 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-Octagonal Kite in tourmaline (white) against the T73 Round Brilliant in tourmaline (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 tourmaline: ahead on 1, level on 1, behind on 6.
1.11 ct at 6.5 mm, against 1.25 ct for the same cut in diamond (−11%)
Weight follows specific gravity: 3.13 for tourmaline against 3.52 for diamond, so the same model at the same size weighs 1.11 ct here and 1.25 ct in diamond, 6.5 mm across. Nothing about the light changes with it.
Try it yourself: Weights in every gemstone on the DG-Octagonal Kite page
Fire 48 against 82 for the DG-Octagonal Kite in diamond: 34 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 (0.015 in tourmaline) and counts a ray as fire when the two directions differ by more than 0.6°. The DG-Octagonal Kite reads 48 against 82 for the same cut in diamond. The figure is the census's; the 3D Gemstone Simulator renders tourmaline'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-Octagonal Kite in tourmaline under the sunny-day lighting.
What helps: the Oval Cut reads 80 for fire in tourmaline, the best of the cuts we score there.
Leakage 37 against 7 for the DG-Octagonal Kite in diamond: 30 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-Octagonal Kite leaks 37% in tourmaline against 7% 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-Octagonal Kite in tourmaline · Leakage 37
DG-Octagonal Kite in diamond · Leakage 7
What helps: the DG-M5 reads 4% for leakage in tourmaline, the best of the cuts we score there.
Try it yourself: Tilt it yourself in the simulator's light map
Brilliance 63 against 88 for the DG-Octagonal Kite in diamond: 25 points lower
The same cut in diamond returns 88. Tourmaline bends light less than diamond: its critical angle is 38.6°, diamond's 24.4°, so a pavilion facet has to be steeper before light reflects off it rather than passing out. The DG-Octagonal Kite's pavilion returns less of tourmaline's light than of diamond's, as the two maps show.
DG-Octagonal Kite in tourmaline · Brilliance 63
DG-Octagonal Kite in diamond · Brilliance 88
What helps: the DG-M5 reads 96 for brilliance in tourmaline, the best of the cuts we score there.
Try it yourself: Open this Light Return map in the simulator
Scintillation 60 against 80 for the T73 Round Brilliant in tourmaline: 20 points lower
Scintillation follows the number of facets the stone shows: 100 × (1 − e^(−facets / 45)). The DG-Octagonal Kite has 41 facets and the T73 73, so 60 against 80. It depends on the geometry alone, so it is the same in every stone.
DG-Octagonal Kite · 41 facets · Scintillation 60
T73 Round Brilliant · 73 facets · Scintillation 80
What helps: the DG-Miliano reads 98 for scintillation in tourmaline, the best of the cuts we score there.
Try it yourself: Compare the Scintillation spoke in the Cut Performance Wheel
Pick the DG-Octagonal Kite in tourmaline for this: it weighs less than in diamond. The catch: it shows less fire than in diamond, leaks more than in diamond, returns less light than in diamond and has fewer facets to sparkle with.
If that catch matters more to you, the Oval Cut reads 80 for fire in tourmaline, 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-Octagonal Kite model we traced.
In our census the DG-Octagonal Kite returns 63 of 100 for brilliance and 48 for fire in tourmaline, against 86 and 50 for the T73 in the same stone. Against that round and against the same cut in diamond it has 1 pro and 4 cons by our thresholds; the summary above names them.
At least 38.6° for a round design: tourmaline's critical angle is 38.6°, 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-Octagonal Kite's pavilion mains sit at 43.0°.
At 6.5 mm across, 1.11 ct in tourmaline, against 1.25 ct for the same cut in diamond (-11%): tourmaline's specific gravity is 3.13, diamond's 3.52.
Yes: the 3D Gemstone Simulator renders it live, with tourmaline's own refractive index and dispersion. Tourmaline 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-Octagonal Kite Cut as exact geometry: 41 planar facets, real-world scale, ready for CAD, rendering, printing and casting.
The DG-Octagonal Kite Cut as a faceting design: 33 + 8 girdles = 41 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.
Tourmaline: optical properties and the top ten cuts · The DG-Octagonal Kite: specifications, model and files