The cut does not refer to the shape of a diamond (pictured left) but rather to a diamond's proportions, symmetry and polish. The cut has 3 main effects on appearance: brilliance (the brightness created by the white light reflected on the surface and inside the polished diamond, fire (the dispersion of light in colors of the visible spectrum) and scintillation (flashes of light and dark) otherwise known as the sparkle!
This is typically the first and most important diamond characteristic because of the human's eye to detect light performance and in essence, the reflectiveness of the diamond.
Shallow Cut: Means that entering light strikes the pavilion facet at a low angle and escapes through the bottom of the diamond
Ideal Cut: A well cut diamond means that light strikes each pavilion facet at an angle which allows most of the light to reflect back to the crown (top).
Deep Cut: Means that entering light strikes the first pavilion facet at angle sharp enough to reflect to the second pavilion. However, as the light strikes the second pavilion the angle is too low and causes the light to refract and escape through the bottom of the diamond.
Color refers to a diamond's lack of color, and the grades evaluate the whiteness of a stone. A color grade of "D" is the highest possible, while a color grade of "Z" is the lowest possible.
Since color manifests itself in diamonds as a pale yellow, the less color a diamond has the higher (better) the grade.
The clarity of a diamond refers to inclusions (blemishes), or lack there of that are seen in the diamond. As the scale (pictured left) indicates, FL is a Flawless diamond which means that it is free from ALL inclusions or blemishes even at 10x magnification. VVS1-VVS2 means the the diamond has minor inclusions that are Very Very Small and difficult to see even under 10x magnification. VS1-VS2 means that the diamond has minor inclusions that are Very Small and can be seen under 10x magnification and occasionally to the naked eye (would appear as a small speck in the diamond). SI1-SI2 means that the diamond has inclusions that can be seen at 10x magnification and may be seen to the naked eye. I1-I2-I3 means that the diamond is imperfect and inclusions are visible under 10x magnification and are likely to be seen to the naked eye.
Carat is the term used to describe the weight of any diamond. Refer to the chart for a pictorial representation to determine carat weight.