Diamond color is all about what you can’t see. Diamonds are valued by how
closely they approach colorlessness – the less color, the higher their value.
(The exception to this is fancy-color diamonds, such as pinks and blues, which
lie outside this color range.)
Most diamonds found in jewelry stores run from colorless to
near-colorless, with slight hints of yellow or brown.
GIA’s color-grading scale for diamonds is the industry standard. The scale
begins with the letter D, representing colorless, and continues with increasing
presence of color to the letter Z, or near-colorless. Each letter grade has a
clearly defined range of color appearance. Diamonds are color-graded by
comparing them to stones of known color under controlled lighting and precise
viewing conditions.
Many of these color distinctions are so subtle as to be invisible to the
untrained eye. But these slight differences make a very big difference in
diamond quality and price.
Why does the GIA color grading system start at D?
Before GIA developed the D-Z Color Grading Scale, a variety of other systems
were loosely applied. These included letters of the alphabet (A, B and C, with
multiple A’s for the best stones), Arabic (0, 1, 2, 3) and Roman (I, II, III)
numerals, and descriptions such as “gem blue” or “blue white.” The result of all
these grading systems was inconsistency and inaccuracy. Because the creators of
the GIA Color Scale wanted to start fresh, without any association with earlier
systems, they chose to start with the letter D—a letter grade normally not
associated with top quality.