As well as the thickness of the girdle, its symmetry must also be checked:
- is the girdle equally thick all round
- is the girdle completely or partially knife-edged
- is the girdle parallel to the table
- is the girdle wavy ?
|Fig 299 Wavy girdle|
|Fig 300 Very irregular girdle: thin to extremely thick|
A symmetrical girdle runs with equal thickness round the stone in a plane parallel to that of the table surface. The points and edges of the upper and lower main facets and of the girdle facets meet at the girdle exactly one under the other and thus ensure equal distances between the 16 intersections. The symmetry is affected when the girdle has a wavy course in relation to the plane of the table (Fig 299) or is unequally thick or, in extreme cases, varies from knife-edged to too-thick (Fig 300); or the intersections are irregular owing to edge displacement at the girdle. An evaluation of these features follows according to their visibility, frequency and effect on the brilliance. In addition to the proportions and the symmetry, cut grading takes into consideration the external features of a cut diamond, for which 10 x magnification is decisive for the evaluation.
|Size of the culet||External Features|