These colours are subdivided into 10 colour grades, called the "International
Colour Grading Scale" (see colour comparison table 220.127.116.11.)
|International Colour Grading Scale|
|exceptional white +||blanc exceptionnel +||hochfeines Weiss +||D|
|exceptional white||blanc exceptionnel||hochfeines Weiss||E|
|rare white +||blanc extra +||feines Weiss +||F|
|rare white||blanc extra||feines Weiss||G|
|slightly tinted white +||blanc nuancé +||leicht getöntesWeiss +||I|
|slightly tinted white||blanc nuancé||leicht getöntesWeiss||J|
|tinted white +||légèrement teinté +||getöntes Weiss +||K|
|tinted white||légèrement teinté||getöntes Weiss||L|
|tinted colour||couleur teintée||getönt||M-Z|
The colours must be determined by comparison with masterstones.
After a complete validation and on the base of a comparison between the results of a measuring instrument with those of a grader, colour measuring equipment can be used for grading.
The colour grades are fixed by a series of masterstones, which, as a definition, fix the lower limit of each colour grade. An international reference-series has been composed by representatives of the WFDB, the IDMA and CIBJO.
A series of valid masterstones must be selected by direct comparison with the international reference series.
The masterstones must comply with the following requirements:
The colour comparison with masterstones is performed under normalized artificial light, equivalent to northern daylight. It is recommended that the characteristics of the artificial light source used, approximate the C.I.E.-standard illuminant D65 (C.I.E. = Commission Internationale de I'Eclairage / International Commission on Illumination).
The masterstones and the diamond to be graded are placed on a V-shaped white support (e.g. a folded white paper) and observed from a direction, perpendicular to the pavilion facets.
The comparison with the masterstones is made as follows: if no difference in colour is observed between the diamond to be graded and a specific reference-diamond, then the colour of the latter is conclusive.
If the colour of the diamond to be graded lies between those of two reference-diamonds, then the colour of the darkest one is conclusive.
Diamonds of equivalent colour are compared with the same masterstones and in the same manner as diamonds with light-yellow colour.
In case of a clearly visible distinction, this has to be mentioned together with the colour grade.
The colour determination is performed by comparison with colour standards.
The following characteristics are described:
Depending on the above mentioned characteristics of the colour, the term "fancy" may precede the colour description.