The total depth percentage is a very
important element of a diamond's proportions and it is greatly
responsible for the amount of brilliance that a diamond will display.
Diamonds which have ideal to very fine cut with proper total depth
percentage provide the greatest brilliance.
Ideal
to Very Fine Cut Diamonds have total depth percentages between
59% and 63%. Diamonds within this range usually provide excellent
brilliance. Diamonds that have depths outside these ranges usually
cost less, but a degree of brilliance is lost. When depth percentage
becomes greater than 65%, the center of the diamond becomes dark
as light refracts through the bottom of the diamond.
However, proper total depth percentage
does not guarantee proper cut. Total depth percentage is very
important but it can sometimes be misleading. Total depth percentage
is a representation of a diamond's overall total depth. It is
possible for two diamonds to have the same depth percentage and
be proportioned differently.
Total depth percentage is a combination
of many other important elements of diamond cut. These elements
include crown height, crown angle, pavilion depth percentage,
pavilion angle and girdle thickness. These elements are properly
proportioned in ideal cut diamonds.
However, some diamonds with total
depth percentages that are in the range of ideal may be improperly
cut and display less brilliance. A diamond with ideal total depth
percentage may also have an overly deep bottom, (deep pavilion
depth percentage & steep pavilion angles) and have a very
low top, (low crown height & shallow crown angle.) A simpler
example would be two men that are six feet tall. One man has perfect
symmetry. His upper body is in proper proportion to his lower
body. The other man has very long legs and a short waist.
