A more or less unequal girdle diameter develops during the bruiting of a rough diamond in which, for example, the cutter is making the most of a slightly rectangular shaped distorted octahedron, and is "stretching" the brilliant in one direction in order to save weight. Damage on one side of a diamond octahedron can also be the cause of an unequal girdle diameter. In order to 'save weight the cutter does not reduce the whole diameter but cuts material away only in the region of the damage (Fig 267).
Deviation from circular form should not amount to more than 2 %; exceeding this limit results in a visible loss of brilliance, and the stone can thus no longer be graded as having a "very good" cut.
 |
 |
| Fig 267a Irregular girdle diameter | Fig 267 Irregular girdle diameter |
| Symmetry Features | Tilted table |