The Four Cs of Diamond Value

Four Factor-known as the Four Cs affect the value of every diamond:
  • Clarity
  • Color
  • Cut
  • Carat Weight

Clarity: A stone's relative position on a flawless-to-imperfect scale.
Clarity characteristics are classified as inclusions (internal) or
blemishes (external). The size, number, position, nature, and color
or relief of characteristics determine the clarity grade. Very few
diamonds are flawless, that is, show no inclusions or blemishes when
examined by a skilled grader under 10x magnification. If other
factors are equal, flawless stones are most expensive.

Color: Grading color in the normal range involves deciding how
closely a stone's bodycolor approaches colorlessness.  Most
diamonds have at least a trace of yellow, brown, or gray bodycolor.
With the exception of some natural fancy colors; such as blue, pink,
purple, or red, the colorless grade is the most valuable.

Cut: The proportions and finish of a polished diamond (also called
make). Cut can also mean shape, as in emerald cut or marquise cut.
Proportions are the size and angle relationships between the facts
and different parts of the stone.  Finish includes polish and details of
facet shape and placement. Cut affects both the weight yield from
rough and the optical efficiency of the polished stone; the more
successful the cutter is in balancing these considerations, the most
valuable the stone will be.

Carat Weight: The metric carat, which equals 0.200 gram, is the
standard unit of weight for diamonds and most other gems. If other
factors are equal, the more a stone weighs, the more valuable it will
be.