Brilliance 28 · Fire 61 · Scintillation 34 · in our census, where the T73 scores 72 · 36 · 80 in amethyst
Three sides, 19 facets, and a larger share of its returned light split into colour than the round brilliant in quartz, 61 against 36. It trails the round on light, sparkle and face-up size.
The triangle is the plainest of the three-sided cuts: two crown tiers over three pavilion tiers, nothing spare. The model we trace sits on a 60.0% table, with a 35.3° crown above and a 41.76° pavilion below, 55.4% deep overall. No cut we measure has fewer facets.
Its pavilion clears amethyst's 40.4° guide minimum, yet the census returns only 28 for brilliance, well under half the T73's 72. In diamond the same model returns 53.
Fire is its bright spot: only the oval, DG-Bowtie and DG-Elongated Hexagon score more in amethyst.
Compared with the T73 Round Brilliant in amethyst and with the Triangle 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.
At a glance: the Triangle Cut in amethyst (white) against the T73 Round Brilliant in amethyst (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 amethyst: ahead on 3, level on 1, behind on 4.
Fire 61 against 36 for the T73 Round Brilliant in amethyst: 25 points higher
Large facets split the light that returns into broad flashes of colour, and the census finds a larger share of it split here than in the T73's finer plan. That share comes from a stone returning little light overall, so expect the colour in a darker face than a round's.
Triangle Cut in amethyst · Fire 61
T73 Round Brilliant in amethyst · Fire 36
0.59 ct at 6.5 mm, against 0.79 ct for the same cut in diamond (−25%)
At a specific gravity of 2.65 against 3.52, the amethyst triangle weighs three quarters of the same stone in diamond. Measured 6.5 mm wide, it is the lightest stone on our amethyst pages.
Try it yourself: Weights in all seven gemstones on the Triangle Cut page
Scintillation 34 against 80 for the T73 Round Brilliant in amethyst: 46 points lower
With 19 facets against the T73's 73, it gives our scintillation score the least to count of any cut in our amethyst census. Sparkle here is the plan, not the stone.
Triangle Cut · 19 facets · Scintillation 34
T73 Round Brilliant · 73 facets · Scintillation 80
What helps: This is the facet plan. For a three-sided amethyst with far more sparkle, the Trillion Cut Amethyst scores 80.
Try it yourself: Compare the Scintillation spoke in the Cut Performance Wheel
Brilliance 28 against 72 for the T73 Round Brilliant in amethyst: 44 points lower
Its pavilion clears the guide minimum. A triangle's three corners return less than a circle's rim, and with so few facets there are few paths back to the eye.
Triangle Cut in amethyst · Brilliance 28
T73 Round Brilliant in amethyst · Brilliance 72
What helps: We have measured no steeper triangle and promise none. In three sides, the Trilliant Cut Amethyst returns 63 and the Trillion Cut Amethyst 60.
Try it yourself: Open this Light Return map in the simulator
Leakage 43 against 25 for the Triangle Cut in diamond: 18 points higher
The same facets in diamond lose about a quarter of the light. In amethyst the share climbs past two fifths, 43%.
Triangle Cut in amethyst · Leakage 43
Triangle Cut in diamond · Leakage 25
What helps: Size does not move the share. In three sides, the Trillion Cut Amethyst leaks 30%.
Try it yourself: Tilt it yourself in the simulator's light map
Face-up size 89 against 100 for the T73 Round Brilliant in amethyst (T73 = 100): 11% less face-up area for the same weight
Measured from the outline at the same weight, the triangle covers less area than any other cut in our census. Choosing amethyst does not change that: face-up size is set by the model's shape.
Triangle Cut · 8.92 x 7.72 mm at 1.00 ct · Face-up size 89
T73 Round Brilliant · 7.12 mm at 1.00 ct · Face-up size 100
What helps: Choose by millimetres rather than carats. The Trillion Cut Amethyst faces up at 100, level with the round.
Try it yourself: See its size at 1.00 ct in amethyst in the 3D Gemstone Simulator
The triangle suits accent stones, geometric clusters and a first faceting project in amethyst, where colour from big facets is welcome.
For a three-sided centre stone with more light, the Trillion Cut Amethyst or the Trilliant Cut Amethyst. For the most fire among amethyst cuts within ten points of the T73's brilliance, DG-Anteros Amethyst.
For fire, yes: 61 against 36 for the T73. It is weak on light, Brilliance 28, and its Scintillation of 34 is the lowest we measure in amethyst.
The trillion returns more light (60 against 28), sparkles far more and faces up larger per carat; the triangle has more fire (61 against 44).
Our model has 19, the fewest of any cut we measure; the T73 has 73.
0.59 ct; the diamond triangle, 0.79 ct.
The Triangle Cut as exact geometry: 19 planar facets, real-world scale, ready for CAD, rendering, printing and casting.
The Triangle Cut as a faceting design: 16 + 3 girdles = 19 facets, 96 index, 3-fold symmetry, ready for the machine.
Questions before you buy? Email us.
Amethyst: optical properties and the top ten cuts · The Triangle Cut: specifications, model and files