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Cut

The “cut” of a diamond is a man-made enhancement that determines its radiance.  A well-cut diamond exhibits brilliance (white light), dispersion (rainbow colored light) and scintillation (sparkle). All three terms describe how effectively the stone returns light back to the viewer's eye. Though there is no single measurement of a diamond that defines its cut, various factors such as the relationship between a diamond's light performance, dimensions and finish are considered. Most gemologists regard cut as the most important diamond characteristic; even if a diamond has perfect color and clarity, a poorly cut diamond will be lackluster, while a well-cut diamond will appear brilliant and fiery. The width and depth of a diamond can have an effect on how light passes through and exits, creating brilliance.


Too Shallow: Light is lost through the bottom, causing the diamond to lose brightness.

Too Deep: Light escapes out the sides, causing the diamond to appear drab and dark.


Determining a diamond's cut grade goes beyond simple measurements of width and depth. It requires computer-aided design tools to create a three-dimensional model to map the diamond's proportions. The correlation between the various dimensions will greatly affect how light reacts once it enters the diamond and how it performs upon exit. By using sophisticated computer modeling, it is possible to track light behavior and measure its level of brightness.



Diameter: The width of the diamond as measured by its girdle.
Table: The largest facet of a gemstone, found at the very top.
Crown: The top section of a diamond, reaching from the girdle to the table.
Girdle: The meeting point of the crown and pavilion that defines the perimeter of the diamond.
Pavilion: The bottom section of a diamond, reaching from the girdle to the culet.
Culet: The facet at the bottom tip of a gemstone. The preferred culet is not visible with the naked eye (it is graded "none" or "small").

Depth: The total height of a gemstone measured from the culet to the table.



Polish and symmetry are two vital features of the cutting process. The polish grade describes the sheen of the diamond's facets and the symmetry grade refers to the facets' alignment. With poor polish, the surface of a facet can be muted and may seem blurred or dull. With poor symmetry, light is deflected, causing a loss of brilliance.  The polish and symmetry grades are listed on each diamond detail page and within the GIA or AGSL diamond grading report. For the most stunning diamond, look for a symmetry grade in a GIA graded diamond as excellent (EX), very good (VG), or good (G). An AGSL graded diamond will use ideal (ID), excellent (EX), very good (VG), or good (G). Avoid diamonds with symmetry grades of fair (F) or poor (P), since the alignment of their facets may misdirect light to the point that it negatively affects the brilliance of the diamond. This is important, because not only do well-cut diamonds appear more brilliant, they can also appear larger than other stones of the same carat weight.