Deep Cut
A deep cut diamond appears small for its weight, since much of its weight is in its deep pavilion and thick girdle. Some of the light that enters the diamond through the crown escapes through the pavilion.
Ideal Cut
An ideal cut diamond is cut to ideal proportions, a set of proportions that maximizes the brilliance and sparkle of a round brilliant cut: light enters the diamond through the crown and is reflected back through the crown.
Shallow Cut
A shallow cut diamond appears large for its weight, due to its characteristically large table, thin girdle, shallow crown and shallow pavilion. Some of the light that enters the diamond through the crown escapes through the pavilion.
Cut is the most important factor in determining a diamond's beauty and value, and the only one of the 4 C's that is completely under human control.
Cut determines how a diamond reflects and plays with light. A diamond is most beautiful when it catches the light and displays brilliance, fire and sparkle. These three terms are important to understand when explaining how diamonds handle light.
Brilliance is the total effect of light reflected and refracted from the interior and exterior surfaces of the diamond. Reflection refers to returning light like a mirror; refraction refers to the bending of light. Brilliance depends on the extent to which light entering from above is reflected back from the pavilion or base facets. The more light reflected, and the less that is leaked or refracted out through the pavilion, the more brilliant the diamond.
Fire is also called dispersion. Fire is the breaking up of white light into the colors of the spectrum. Fire causes the rainbow effect you see and is an element of beauty and excitement in a diamond.
Sparkle is also called scintillation. It is the flashing effect seen when a diamond moves in the light.
Three factors determine cut quality: proportions, symmetry and polish. Proportion refers to the relationship between the size, shape and angle of each facet. Symmetry refers to the exactness of the diamond's shape as well as the even placement and symmetrical arrangement of the facets. Polish is the diamond's smoothness and shine. Cut grade is determined by a diamond's face-up appearance (brightness, fire, and scintillation), design (ratio and durability), and craftsmanship (polish and symmetry). The Gemological Institute of America (GIA) cut grades are Excellent, Very Good, Good, Fair and Poor.
Excellent Cut |
Virtually all light that enters the diamond is reflected |
Maximum brilliance and fire |
Very Good Cut |
Nearly all of the light that enters the diamond is reflected |
High brilliance and fire |
Good Cut |
Most of the light that enters the diamond is reflected |
Brilliance and sparkle |
Fair Cut |
Much of the light that enters the diamond escapes through the pavilion |
Very little brilliance and fire |
Poor Cut |
Most of the light that enters the diamond escapes through the pavilion |
Little to no brilliance or fire |