Identifying the Cut Grade (5.44)

Identifying the Cut Grade (5.44)

The most cost effective approach in recognizing proper proportions is with your 10x loupe. If necessary review these previous sections to understand the importance of the "Cut Grade": Note: Some subsections were intentionally left out since they do not directly relate to "Cut Grade".

The Critical Angle (5.08)

Pavilion Angle (5.09) 

Crown Angle (5.10)

Measuring Crown Angles (5.11)

Judging Crown Angles (5.13)

The Pavilion Main Method (5.14)

Estimating Pavilion Angle (5.15)

The Pavilion Depth (5.16)

Table Reflection Method (5.17)

General Rules for Pavilion Depth Estimation (5.18)

Deep Pavilions (5.19)

Shallow Pavilion (5.20)

The Culet (5.21)

Fish-Eye (5.23)

The Table (5.24)

Measuring Table Size (5.25)

The Table Percentage Ratio Method (5.26)

The Table Percentage Bowing Method (5.27)

The Ideal Star Shape (5.28)

Estimating Table Size by Eye (5.29)

Likeliness of Breakage (5.30)

Girdle Thickness (5.31)

The Overall Appearance of the Girdle (5.35)

Upper and Lower Girdle Facets (Halves) (5.36)

The Role of the Upper and Lower Girdle Facets (Halves) (5.37)

Lower Girdle Facet Height (5.38)

Upper Girdle Facet Height (5.39)

Cutting the Upper and  Lower Girdle Facets (Halves) (5.40) 

The Star Facets (5.41)

Proportion Analyzers

The very popular Sarin DiaScan Diamond Cut Evaluator (currently selling for $7400-$9400), is a popular choice for diamond cutters and volume dealers. The Sarine Diamension HD is more sophisticated and detailed instrument. There are also other similar instruments from Sarine.

Left Courtesy of Kassoy: https://kassoy.com/sarin/sarin-diascan-diamond-cut-evaluator.asp

Right Courtesy of Aerodiam: https://aerodiam.com/sarin-products/diamension-hd/

The more affordable (on the preowned market), old school GIA Proportionscope:

GIA's Facetware: Free access with (login credentials) to GIA's database of 38.5 million proportion possibilities.  https://www.gia.edu/facetware

Courtesy of Lexus Group https://lexusindia.in/so-gf.html

General Proportions and Characteristics

The general proportions and characteristics you will look for in an excellent cut grade for a round brilliant cut are:

Table Size: 53%-60%

Crown Angles: 33.7-35.8 Degrees

Girdle Thickness: Thin-Slightly Thick (No wavy or scalloped girdles. Make sure girdle is parallel with table).

Pavilion Angle: 40.2-41.25 Degrees (Consistent angles all the way around. Watch out for out of center culets). Use the Table Reflection Method.

Total Depth: 59.0%-62.0%

Culet: None (pointed) or Very Small (No abraded culets or very small culets that do not form a perfect octagon).

Polish and Symmetry: Excellent or Very Good

 

 

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