Brilliant Cut Form

Cut bears a significant impact on the cost of the diamond

Diamond cut is independent of its natural qualities and of the method of its production. The diamond-cutting procedure is implemented by specialists and gives the final shape to the stone as the objective.

The following table summarizes the four general classes of quality proportions and polishing (finishing) of a typical brilliant cut that can be identified in the modern diamond market in accordance with the standard of the Gemological Institute of America (GIA). The quality class is determined by the degree of deviations from ideal proportions. Boundaries between the categories are quite flexible:


The International System of Evaluation of Cut Diamonds


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Excellent

This diamond has the highest status. The culasse dimensions tend to vary in the range of 53–60 pct. For diamonds of, at least, 0.50 carat, culasse dimensions may be 61 pct or, in some cases, 62 pct. The crown angle is 34–35 degrees. The girdle has average dimensions. The pavilion depth is 43 pct. The culet is small or non-existent. Polishing is excellent.

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Average

The crown angle of such diamonds is 30–32 degrees. The culasse dimensions are 65–70 pct of the total diameter of the diamond. The girdle is either very thin or very thick. The culet is large. The pavilion depth is 41–46 pct. Polishing is average; this class also includes stones with the culasse dimensions of 51–52 pct or with the crown angle of 37 degrees.

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Good

Typically, the culasse dimensions of such diamonds fall in the range of 61–64 pct, respectively; and the crown angle is 32–34 degrees. The girdle can be either thin or thick. The pavilion depth is 42–44 pct. The culet is average. Polishing is good.

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Below the average

In such diamonds, the culet is very large. Polishing is below average. The culasse dimensions are more than 70 pct; depending on the crown angle, the girdle is either very thin or very thick. The crown angle is less than 30 degrees, and the pavilion depth may be either below 41 pct or more than 46 pct. Also, this class include diamonds with the crown angle of more than 37 degrees and the culasse dimensions of not more than 51 pct, which contain greater deviations in terms of symmetry.