Different
Shapes 
Cut
Clarity
Color
Carat
Certificates
Math is the determining factor in deciding the cut of a diamond. Every diamond is cut according to an exact mathematical formula.
The most common cut, the round brilliant, has 58 facets, or small, flat, polished planes designed to yield the maximum amount of light to be reflected back to the viewer.
This reflection, known as brilliance, is an extremely important factor in evaluating the quality of a diamond. A poorly cut diamond will actually lose light and appear dull. The two most common
mistakes in cutting a diamond are:
Brilliance?
Determining
a diamond's cut grade, however, goes beyond simple measurements of
width and depth. Using an optical measuring device, a
three-dimensional model is created to determine the diamond's
proportions and angles. The interrelations between these various
dimensions will greatly affect how light reacts once it enters and
how it behaves once it exits; by using sophisticated computer
modeling, it is possible to trace light behavior and measure its
levels of brightness, fire and scintillation - the face-up
appearance.
Diameter:
The width of the diamond as measured through the girdle.
Table: The largest facet of a gemstone.
Crown: The top portion of a diamond extending from the girdle
to the table.
Girdle: The intersection of the crown and pavilion which
defines the perimeter of the diamond.
Pavilion: The bottom portion of a diamond, extending from the
girdle to the culet.
Culet: The facet at the tip of a gemstone. The preferred culet
is not visible with the unaided eye (graded "none" or
"small").
Depth: The height of a gemstone measured from the culet to the
table.
Polish and
Symmetry
Polish
and symmetry are two important aspects of the cutting process. The
polish grade describes the smoothness of the diamond's facets, and
the symmetry grade refers to alignment of the facets. With poor
polish, the surface of a facet can be dulled, and may create
blurred or dulled sparkle. With poor symmetry, light can be
misdirected as it enters and exits the diamond. The polish and
symmetry grades are clearly listed in each diamond detail page and
within the GIA or AGSL diamond grading report. For the most
beautiful diamond, look for a symmetry grade of excellent (EX),
very good (VG), or good (G) for a GIA graded diamond, and ideal
(ID), excellent (EX), very good (VG), or good (G) for an AGSL
graded diamond. Avoid diamonds with symmetry grades of fair (F) or
poor (P), as the alignment of their facets may misdirect light so
severely that it affects the brilliance of the diamond.
