CUT DIAMOND: SHAPES AND CUTTING ELEMENTS.

A gem-quality diamond is not mounted in the state it has been quarried. At first it is cut. For many centuries, the style of diamond cutting has been gradually changed along with understanding optical properties and development of lapidary arts. In 1919, Marcel Tolkowsky calculated the angles and proportions of an ideal diamond, which would be characterized by the maximum luster and fire. A round diamond with 57 facets (the commonest style) was taken as an original shape.


The main parameters of a cut diamond
The main parameters of a cut diamond are :

  • Average girdle diameter (mm) (the mean value of the minimum and maximum diameter) is taken as 100%;
  • Table size (% of the average girdle diameter);
  • Total depth (mm and % of the average girdle diameter);
  • Crown height (from the upper edge of girdle to table; % of the average girdle diameter);
  • Pavilion depth (from the lower edge of girdle to culet; % of the average girdle diameter);
  • Girdle thickness (qualitative grading or % of the average girdle diameter);
  • Crown angle (degrees; the angle between the bezel facets and the girdle plane);
  • Pavilion angle (degrees; the angle between the pavilion main facets and the girdle plane);
  • Culet size (qualitative grading).

The facets of a diamond having a similar shape and a similar tilt to the girdle plane form a stage.


The common fancy cutting styles

In addition to the standard round brilliant cut (57 facets), there are other cutting styles in the market, which are commonly called fancy styles.

These and some other styles have their own names; the rest require the term "fancy" added to their description (for example, round fancy cut). The cutting elements of such diamonds may be described with additional terms; for example, some elongated shapes have a keel instead of a culet . Fancy shapes include wedge-cut (oval, pear, marquise, heart, princess, radiant), step-cut (emerald, baguette, square), and combined varieties.

Simplified varieties of the round brilliant cut are represented by Kr-17 (with eight facets on the pavilion and eight facets on the crown) and Kr-33 (with sixteen facets on both crown and pavilion). These styles are usually applied to small stones.

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