A review of the “foundation” of GIA’s new cut grade system


RD39 HCA 6.3		RD43 HCA 6.2		RD45 HCA 10? (off scale)

Ideal-Scope Lighting		Ideal-Scope Lighting		Ideal-Scope Lighting


Jewellery Shop Lighting		Jewellery Shop Lighting		Jewellery Shop Lighting


Disco Lighting		Disco Lighting		Disco Lighting


GIA photo 0.70ct		GIA photo 0.50ct		GIA photo o.54ct

DiamCalc Scores		DiamCalc Scores		DiamCalc Scores
Light Return Mono	0.88	Light Return Mono	0.77	Light Return Mono	0.65
Light Return Stereo	0.92	Light Return Stereo	0.81	Light Return Stereo	0.69
Contrast	1.03	Contrast	1.03	Contrast	0.99
Specifications		Specifications		Specifications
Table Size	57%	Table Size	57%	Table Size	62%
Crown Angle	35.5°	Crown Angle	38.5°	Crown Angle	37.0°
Pavilion Angle	41.2°	Pavilion Angle	41.8°	Pavilion Angle	45.2°
Star Length	55%	Star Length	55%	Star Length	60%
Lower Girdle	80%	Lower Girdle	80%	Lower Girdle	85%
Girdle Thickness	Etk	Girdle Thickness	Thk-Vtk	Girdle Thickness	Med-Vtk
Culet Size	None	Culet Size	None	Culet Size	None
Total Depth	74%	Total Depth	71.5%	Total Depth	69.3%
Polish	G	Polish	G	Polish	G
Symmetry	G	Symmetry	G	Symmetry	G
COMMENTS: This is a grade for the worst 1% of certified diamonds. (On 11/19/2004 there were only 441 plus 1.00ct rounds with depth % greater than 69% listed on Rapnet).
This one has old the AGS 0 proportions, but with an extremely thick girdle which adds 47% of additional weight. This 0.70ct diamond has the expected diameter of a 0.54ct diamond which has a ‘list’ of half the cost.		Because of its very thick girdle, this 0.50ct diamond has the expected diameter of a 0.37ct stone, which has a ‘list’ price of less than half the cost.		This is as bad as diamond cut quality gets. Stones like this are classed as ‘promotional’ and are seldom graded by laboratories. Its stated “large total depth” has nothing to do with its poor performance. (See discussion)

Specifications

Specifications

Specifications