"Kozibe" is name of optical effect like "Nail Head", "Fish Eye" and etc. The term "Kozibe" had been introduced by HRD staff in Antwerp. Kozibe diamonds that show culet through crown main facets in the face-up position. In particular this phenomenon led to strong fading of crown brightness for not very big stones. This effect is appeared only in diamonds with extra total height (big height is because of either high crown or thick girdle), and that is why it can be used as secondary negative attribute for big stones also. The value of angle in the field "Kozibe" in the DiamCalc means angle of tilt when observer can see culet through crown facets. If the value of angle is negative then it is no need to tilt because culet should be seen through all facets of crown. Figure 1. The photo real illustration show the kozibe effect. Crown angle is 35,00 degree, pavilion angle is 50,00 degree, culet is medium and kozibe is -1,70 degree. Obtained with DiamCalc software.

Proportions Diameter Sec.Diameter Total height Crown height (bezel) Crown height (valley) Crown angle Table diameter Pavilion depth (mains) Pavilion angle Culet Girdle valley	Advanced Square deviation Star facets Lower facets   Girdle (valley) Girdle (bezel)   Fish eye Kozibe	Advanced 2 Crown angle (min) Crown angle (max) Crown angle (avg)   Pavilion angle (min) Pavilion angle (max) Pavilion angle (avg)
OctoNus Spread & AGS Spread

Helium Polish cut parameters