Three GIA Cut graded
diamonds* were photographed in GIA's Diamond Dock light box. One was Very Good and two were GIA Excellent.
Table 1. Diamonds used in this review
| Specimen | A. | B. | C. |
| Carat/Color/Clarity | 1.16 G SI1 | 1.19 G VS2 | 1.28 G VS1 |
| Diameter | 6.85mm | 6.75mm | 6.92mm |
| Table / depth % | 60% / 58.9% | 55% / 62.7% | 57% / 62.9% |
| Crown Angle | 33° | 34.5° | 35° |
| Pavilion Angle | 40.6° | 41° | 41.4° |
| Girdle[i] | medium to slightly-thick | medium to slightly-thick | medium to slightly-thick |
| Star / Lower Girdle % | 50% / 80% | 45% / 80% | 45% / 80% |
| GIA Cut Grade | Very Good | Excellent | Excellent |
| AGS Light Performance | 3 | 0 (Ideal) | 2 |
| DiamCalc Light Return | .96 | .99 | .88 |
| DiamCalc Contrast | .93 | .99 | 1.01 |
| DiamCalc Spread | +3% | -3% | -5% |
All stones were graded by GIA: Very good or Excellent for Symmetry and Polish. None for Fluorescence.
Stone A has Painted Upper Girdle Facets |
Figure 1. A young grade using GIA's Diamond Dock lighting box. The tray is actually the same shade as the body of the box, but appears lighter because of its proximity to the two 15 watt high color temperature florescent tubes. There are two switches on the upper right for these tubes and / or 12 LED lights (which are not turned on, also this photo was taken with flash).
[*] - All three diamonds were graded and certified by GIA. The report numbers have not been given to protect the anonymity of the companies who made these diamonds available for this study.
[i] - The girdle profiles shown here for all three Medium to Slightly-Thick graded stones. There is very little difference, especially between A - 1.16 and C - 1.28ct stones. Note that C has slightly painted upper girdle facets which adds to the 'shallowness' of this stone by reducing the contrast and lowering the upper girdle facet angles by around one degree.
