|
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. |