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RD01 HCA 0.6 | RD08 HCA 2.2 | RD20 HCA 1.9 |
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Ideal-Scope Lighting | Ideal-Scope Lighting | Ideal-Scope Lighting |
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Jewellery Shop Lighting | Jewellery Shop Lighting | Jewellery Shop Lighting |
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Disco Lighting | Disco Lighting | Disco Lighting |
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GIA photo 0.61ct | GIA photo 0.50ct | GIA photo 0.62ct |
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DiamCalc Scores | DiamCalc Scores | DiamCalc Scores |
Light Return Mono | | 1.00 | | Light Return Mono | | 0.99 | | Light Return Mono | | 0.98 | |
Light Return Stereo | | 0.99 | | Light Return Stereo | | 1.00 | | Light Return Stereo | | 0.98 | |
Contrast | | 0.96 | | Contrast | | 0.97 | | Contrast | | 0.92 | |
Specifications | Specifications | Specifications |
Table Size | | 54% | Table Size | | 57% 58 | Table Size | | 61% |
Crown Angle | | 34.0° (34.3°) [i] | Crown Angle | | 33.5° (33.4) | Crown Angle | | 34.5° (34.3) |
Pavilion Angle | | 40.6° | Pavilion Angle | | 41.2° | Pavilion Angle | | 40.8° (40.7) |
Star Length | | 50% (53.8%) | Star Length | | 55% (54) | Star Length | | 55% |
Lower Girdle | | 75% (81%) | Lower Girdle | | 85% (84) | Lower Girdle | | 80% (79) |
Girdle Thickness | | Thin-Med (2.9%) | Girdle Thickness | | Med (3.9) | Girdle Thickness | | Med (3.2) |
Culet Size | | None | Culet Size | | None | Culet Size | | Non |
Total Depth | | 61.2% | Total Depth | | 61.1% | Total Depth | | 59.6% |
Polish | | VG | Polish | | VG | Polish | | VG |
Symmetry | | VG | Symmetry | | VG | Symmetry | | VG |
COMMENTS: GIA’s top grade appears looser than the proposed new AGS system |
An obviously good choice; slightly shallower than Tolkowsky proportions and excellent symmetry (as shown in the photo) give the appearance of bigger facets, with bigger but less frequent flashes of fire. This is enhanced by short lower girdle facets (LG’s). | The weakest of the 3 stones. Shorter LG’s could improve the stone. LG’s and what appears as the weakest symmetry of the 3 stones adds to the appearance of more facets. Note: slight ideal-scope table leakage does not greatly reduce light return. | The second best stone. Very few 61% table diamonds will also be given AGS’s top grade. The slight ideal-scope table leakage has little impact on light return. Note the thin looking pavilion mains caused by the larger sized table. |
[i]This is additional data listed in (brackets). In the GIA G&G Fire article, Fall 2001, 28 stones are listed with precise numerals. The later Foundation article includes these stones in the 45 used in that study; however they have been rounded – crowns to 0.5°, pavilions to 0.2° and minor facets to 5% steps.