Diamond Color Grading

 The Gemological Institute of America (GIA) diamond color grading system is divided into 23 color ranges, denoted with the letters “D” through “Z”.  A chart on this page illustrates the grading system and gives general color descriptions and information for each grade.

 Gary H. Petersen assures that diamonds are accurately color graded to GIA standards by comparing the diamonds we grade against GIA certified and registered master diamonds.  These are diamonds which have been color graded, registered and certified by GIA.

 Mounted diamonds may be assigned a two-color grade range, e.g., “H-I”.  Depending on the visual and color interference presented by the mounting, it is not always possible to differentiate the subtle color distinctions between two adjacent color grades when stones are mounted.

 Gary H. Petersen does not assign a color grade of “D” to a mounted diamond.  If the appraiser believes  the diamond may be within this category, we will recommend de-mounting the diamond prior to establishing the final color grade.

 Unmounted diamonds are assigned a single color grade.