Diamonds are
assigned color grades by comparing them to diamonds with color grades which
have been certified by GIA as master color comparison diamonds. The color
grade of a diamond is determined by arranging the GIA master color
comparison diamonds about one half inch apart, the lightest on the left and
the others on the right in order of increasing darkness To accurately
determine color, a diamond must be completely free of all dirt and oil. A
diamonds color is best observed when viewed through the pavilion in the
table-down position on a flat white diamond grading trough with line of
sight parallel to the girdle plane. A diamonds color grade is
determined by moving it along the row of masters comparison guide diamonds
until one seems to match. It is then placed on the side of the master, and
then on the other side and compared carefully. If the diamonds color tone is
lighter than the master, the next highest color grade is assigned. If the
diamond is the same or only slightly darker, the grade of the master
comparison guide diamond is assigned. To attain the most accurate analysis
of a diamonds color it is recommended that a diamond be color graded in a
white color free environment. Color grades are most accurate when evaluated
in a darkened room using only the correct light source. Filtered, cool
white, balanced fluorescent light is best; unlike sunlight, it is nearly
free of ultraviolet light. The GIA GEM Diamond Lite is probably the
best color grading light. |