Brilliance 88 · Fire 63 · Scintillation 85 · in our census, where the T73 scores 98 · 76 · 80 in GGG
How the DG-M5 handles light in GGG, measured: brilliance 88, fire 63 and 12% leakage, set against the T73 in the same stone and against the same cut in diamond.
GGG has a refractive index of 1.970 and a dispersion of 0.045. Its critical angle, from the low end of that range, is 30.5°, so a round design needs a pavilion of at least 37.4° for head-on light to reflect off both sides of the pavilion and leave through the table. We trace it with one index, 1.970, the midpoint of the published range, and a fire spread of 0.039, 0.86 of the published dispersion. Every picture here is our Light Return tracer at 1.970, and every figure is from the same light census that scores the other gemstones; the 3D Gemstone Simulator shows the DG-M5 in GGG 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 GGG, the census returns 88 of 100 for brilliance and 63 for fire, against 98 and 76 for the T73, our benchmark, in the same stone; the same DG-M5 in diamond reads 97 and 67.
Compared with the T73 Round Brilliant in GGG 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.
At a glance: the DG-M5 in GGG (white) against the T73 Round Brilliant in GGG (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 ggg: ahead on 2, level on 2, behind on 4.
Scintillation 85 against 80 for the T73 Round Brilliant in GGG: 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.
DG-M5 · 85 facets · Scintillation 85
T73 Round Brilliant · 73 facets · Scintillation 80
Try it yourself: Compare the Scintillation spoke in the Cut Performance Wheel
1.97 ct at 6.5 mm, against 0.98 ct for the same cut in diamond (+100%)
Weight follows specific gravity: 7.05 for GGG against 3.52 for diamond, so the same model at the same size weighs 1.97 ct here and 0.98 ct in diamond, 6.5 mm across. Nothing about the light changes with it.
Try it yourself: Weights in every gemstone on the DG-M5 page
Fire 63 against 76 for the T73 Round Brilliant in GGG: 13 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 (0.039 in GGG) and counts a ray as fire when the two directions differ by more than 0.6°. The DG-M5 reads 63 against 76 for the T73 in GGG. The figure is the census's; the 3D Gemstone Simulator renders GGG'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 GGG under the sunny-day lighting.
What helps: the Oval Cut reads 96 for fire in GGG, the best of the cuts we score there.
Brilliance 88 against 98 for the T73 Round Brilliant in GGG: 10 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 GGG, whose critical angle is 30.5°, the DG-M5 returns 88 of 100 and the T73 98. 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 GGG · Brilliance 88
T73 Round Brilliant in GGG · Brilliance 98
What helps: the DG-Broken Hearts and Arrows reads 98 for brilliance in GGG, the best of the cuts we score there.
Try it yourself: Open this Light Return map in the simulator
Leakage 12 against 2 for the T73 Round Brilliant in GGG: 10 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-M5 leaks 12% in GGG against 2% for the T73 in GGG. Grey in the maps below is leaking light; the share under each picture is that picture's own.
DG-M5 in GGG · Leakage 12
T73 Round Brilliant in GGG · Leakage 2
What helps: the DG-Broken Hearts and Arrows reads 2% for leakage in GGG, the best of the cuts we score there.
Try it yourself: Tilt it yourself in the simulator's light map
Pick the DG-M5 in GGG for this: it has more facets to sparkle with. The catch: it weighs more than in diamond, shows less fire than the T73, returns less light than the T73 and leaks more light than the T73.
If that catch matters more to you, the Oval Cut reads 96 for fire in GGG, 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.
In our census the DG-M5 returns 88 of 100 for brilliance and 63 for fire in GGG, against 98 and 76 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 37.4° for a round design: GGG's critical angle is 30.5°, 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 DG-M5's pavilion mains sit at 41.5°.
At 6.5 mm across, 1.97 ct in GGG, against 0.98 ct for the same cut in diamond (+100%): GGG's specific gravity is 7.05, diamond's 3.52.
Yes: the 3D Gemstone Simulator renders it live, with GGG's own refractive index and dispersion. GGG 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-M5 Cut as exact geometry: 85 planar facets, real-world scale, ready for CAD, rendering, printing and casting.
The DG-M5 Cut as a faceting design: 61 + 24 girdles = 85 facets, 96 index, 12-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.
GGG: optical properties and the top ten cuts · The DG-M5: specifications, model and files