The T73 benchmark is the round brilliant that our tools compare every cut with, in the same gemstone. It has Tolkowsky's 1919 angles and table, and 73 facets: 57 plus 16 girdle facets.
In more detail
Its main crown angle is 34.5° and its main pavilion angle 40.75°, with a 53% table. In diamond it reads 93 for brilliance, 78 for fire and 80 for scintillation in our census. It is a reference, not a top score: five cuts score higher overall in diamond.
How we measure it
The Cut Performance Wheel draws the T73 as a dashed outline. Each cut-page bar shows a thin mark for it. The Cut Grading Tool traces its brilliance and light maps on the T73.
Related terms
- Cut Performance Wheel: The Cut Performance Wheel is a free Digital Gemology tool. It draws eight light-performance scores of one cut, in one gemstone, on a wheel.
- Cut Performance Index: The Cut Performance Index is Digital Gemology's open table of light-performance scores for the cuts we sell, in seven gemstones. It gives each cut brilliance, fire, scintillation, tilt, symmetry, spread, shape-norm, leakage and an overall score.
- Brilliance: Brilliance is the white light that a cut stone returns to the viewer. In our census, it is the share of entering light that leaves through the crown toward the viewer.
- Crown angle: The crown angle is the slope of the bezel facets, measured against the plane of the girdle.
- Pavilion angle: The pavilion angle is the slope of the pavilion mains, measured against the plane of the girdle.