DG-M5 Tanzanite: returns more light than the T73 in tanzanite
Brilliance 100 · Fire 47 · Scintillation 85 · in our census, where the T73 scores 92 · 47 · 80 in tanzanite
How the DG-M5 handles light in tanzanite, measured: brilliance 100, fire 47 and 0% leakage, set against the T73 in the same stone and against the same cut in diamond.
Light Return map of the DG-M5 in tanzanite, face-up, from our own tracer at refractive index 1.685. Red, green and blue return light to the eye; gray leaks.
DG-M5 Tanzanite
Tanzanite has a refractive index of 1.685 to 1.707 and a dispersion of 0.019. Its critical angle, from the low end of that range, is 36.4°, so a round design needs a pavilion of at least 36.4° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.696, the midpoint of the published range, and a fire spread of 0.016, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 1.685, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the DG-M5 in tanzanite live.
The DG-M5 has 85 facets and a total depth of 60.6% of its width; its pavilion mains sit at 41.5°. In tanzanite, the census returns 100 of 100 for brilliance and 47 for fire, against 92 and 47 for the T73, our benchmark, in the same stone; the same DG-M5 in diamond reads 97 and 67.
Is tanzanite good in a DG-M5? Pros and cons, measured
Compared with the T73 Round Brilliant in tanzanite and with the DG-M5 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 DG-M5 in tanzanite (white) against the T73 Round Brilliant in tanzanite (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 tanzanite: ahead on 4, level on 3, behind on 1.
Global83, the comparison 80, difference +3
Brilliance100, the comparison 92, difference +8
Fire47, the comparison 47, difference 0
Scintillation85, the comparison 80, difference +5
Spread100, the comparison 100, difference 0
Symmetry100, the comparison 100, difference 0
Shape-norm107, the comparison 99, difference +8
Tilt69, the comparison 73, difference −4
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 DG-M5 gains in tanzanite
Returns more light than the T73 in tanzanite
Brilliance 100 against 92 for the T73 Round Brilliant in tanzanite: 8 points higher
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 tanzanite, whose critical angle is 36.4°, the DG-M5 returns 100 of 100 and the T73 92. The DG-M5's pavilion mains sit at 41.5°, the T73's at 40.8°. The maps below show where each stone's light returns from and where it leaks.
DG-M5 in tanzanite · Brilliance 100
T73 Round Brilliant in tanzanite · Brilliance 92
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.
Leakage 0 against 8 for the T73 Round Brilliant in tanzanite: 8 points lower
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-M5 leaks 0% in tanzanite against 8% for the T73 in tanzanite. Grey in the maps below is leaking light; the share under each picture is that picture's own.
DG-M5 in tanzanite · Leakage 0
0° · 0% leak
10° · 9% leak
20° · 28% leak
30° · 32% leak
T73 Round Brilliant in tanzanite · Leakage 8
0° · 9% leak
10° · 19% leak
20° · 30% leak
30° · 32% 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.
Scintillation 85 against 80 for the T73 Round Brilliant in tanzanite: 5 points higher
Scintillation follows the number of facets the stone shows: 100 × (1 − e^(−facets / 45)). The DG-M5 has 85 facets and the T73 73, so 85 against 80. It depends on the geometry alone, so it is the same in every stone.
Scintillation follows the number of facets: more facets, more and smaller flashes as the stone moves. Compare the facet counts under the drawings; each drawing shows only the crown. Drawn from each cut's own model.
0.94 ct at 6.5 mm, against 0.98 ct for the same cut in diamond (−5%)
Weight follows specific gravity: 3.35 for tanzanite against 3.52 for diamond, so the same model at the same size weighs 0.94 ct here and 0.98 ct in diamond, 6.5 mm across. Nothing about the light changes with it.
A DG-M5 6.5 mm across, weighed from the model's measured volume and each stone's specific gravity.
Fire 47 against 67 for the DG-M5 in diamond: 20 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 (0.016 in tanzanite) and counts a ray as fire when the two directions differ by more than 0.6°. The DG-M5 reads 47 against 67 for the same cut in diamond. The figure is the census's; the 3D Gemstone Simulator renders tanzanite'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-M5 in tanzanite under the sunny-day lighting.
What helps:the DG-Elongated Hexagon reads 79 for fire in tanzanite, the best of the cuts we score there.
Tilt 69 against 83 for the DG-M5 in diamond: 14 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-M5 keeps 69 against 83 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-M5 in tanzanite · Tilt 69
0° · 0% leak
10° · 9% leak
20° · 28% leak
30° · 32% leak
DG-M5 in diamond · Tilt 83
0° · 0% leak
10° · 4% leak
20° · 14% leak
30° · 26% leak
Tilt is how much of its own face-up light a stone keeps when tilted. 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-Miliano reads 84 for tilt in tanzanite, the best of the cuts we score there.
Pick the DG-M5 in tanzanite for this: it returns more light than the T73, leaks less light than the T73, has more facets to sparkle with and weighs less than in diamond. The catch: it shows less fire than in diamond and loses more light when tilted than in diamond.
If that catch matters more to you, the DG-Elongated Hexagon reads 79 for fire in tanzanite, 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-M5 model we traced.
DG-M5 Tanzanite: questions
Is the DG-M5 a good cut for tanzanite?
In our census the DG-M5 returns 100 of 100 for brilliance and 47 for fire in tanzanite, against 92 and 47 for the T73 in the same stone. Against that round and against the same cut in diamond it has 4 pros and 2 cons by our thresholds; the summary above names them.
What pavilion angle does tanzanite need?
At least 36.4° for a round design: tanzanite's critical angle is 36.4°, 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-M5's pavilion mains sit at 41.5°.
How much does a DG-M5 weigh in tanzanite?
At 6.5 mm across, 0.94 ct in tanzanite, against 0.98 ct for the same cut in diamond (-5%): tanzanite's specific gravity is 3.35, diamond's 3.52.
Can I see the DG-M5 in tanzanite in 3D?
Yes: the 3D Gemstone Simulator renders it live, with tanzanite's own refractive index and dispersion. Tanzanite 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 DG-M5 Cut files
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DG-M5 Cut 3D files
The DG-M5 Cut as exact geometry: 85 planar facets, real-world scale, ready for CAD,
rendering, printing and casting.
