Carat | Cut | Clarity | Color
Many people confuse cut with the shape of a diamond. Most diamonds are cut round with a full 58 facets, and a good cut, or make, has more scintillation, more sparkle. The shape of the diamond, however, is largely a matter of personal preference and does not directly affect the value. It is the work of a master cutter that allows the diamond to be cut in such a way as to permit the maximum amount of light to be reflected through the diamond, and that's a great reflection on you. It is the cut that enables a diamond to make the best use of light.
The key words that help define a cut are as follows:
Proportion - The best cut diamonds reflect light back to the eye evenly in the face-up position. Here no dark areas are visible. Dark or 'dead' areas are due to poor cutting. When a diamond is well-cut (either a fine cut or an Ideal cut), light enters through the table and travels all the way to the pavilion where it reflects from one side of the diamond to the other - intensifying in the mirror-like facets as it travels - before reflecting back out of the diamond through the table and into the observer's eye. This brightness that should come from the very heart of a diamond is known as brilliance. Brilliance is what differentiates the diamonds ability to reflect light from those lesser abilities found in other gemstones.
Note: The fine and ideal cuts are sought after while the shallow and deep cuts offer too much loss of light as a result of the cut itself.
Finish - Finish is the quality imparted to a diamond by the direct skill of the diamond cutter. The term "finish" entails every aspect of a diamond's appearance that is not a result of the diamond's natural existence when it is recovered from the ground. The diamond's design, the precision of its cutting details, and the quality of its polish are all a consideration when a gemologist is grading finish. If you examine a diamond's grading report, you will see its finish graded according to two separate categories: polish and symmetry.
Polish - is defined as any blemish on the surface of the diamond not significant enough to affect clarity.
Symmetry - is defined as the variations in a diamond's symmetry. Small variations can include misalignment of facets or facets that fail to point correctly to the girdle (this misalignment is completely undetectable to the naked eye). Symmetry problems are indicative of diamonds graded as fair or poor.
Table - is defined as the largest and top-most facet on the diamond's crown. The table percentage is the value which represents how the diameter of the table facet compares to the diameter of the entire diamond. So, for example if a diamond with a 53% table has a table which is 53% as wide as the diamond's outline. For a round diamond, gemologists calculate table percentage by dividing the diameter of the table, which is measured in millimeters (this millimeter measurement does not appear on diamond grading reports) by the average girdle diameter (an average of the first two millimeter measurements on the top left-hand side of a diamond grading report). For a fancy shape diamond, table percentage is calculated by dividing the width of the table, at the widest part of the diamond, by the millimeter width of the entire stone (this total width measurement is the second of the three millimeter values in the top left-hand corner of the diamond grading report. The Table measurements are subtleties which vary ever so slightly and should not become a pre-occupation is diamond selection.
Scintillation - is defined as the ability to reflect and return white light to the eye. Creating those quick flashes of light you see as a person tilts the diamond back and forth during normal movement.
Dispersion - is defined as the facets, and the angles at which a diamond is cut. The way they have been skillfully designed to break up white light as it hits the surface, separating it into its component spectral colors-red, blue, green etc. This effect, which appears as a play of small flashes of color across the surface of the diamond as it is tilted, is also called "fire".
The crown - For a round diamond, in order for the crown to provide sufficient fire, the bezel facets should be cut within a specific range of angles (usually between 33 and 35 degrees). However, this range is merely a guideline, not a hard-and-fast rule that must be adhered to in every case. At the outer points of this range, you might find diamonds with crown angles of as little as 31.5 degrees and as much as 35.9 degrees which are still very attractive. These angles do not affect the diamond's table percentage in any way. It is possible for a diamond's crown to have any combination of crown angles and table size that a cutter desires.
The pavilion - is the part of the diamond that lays just below the girdle. It is easy to see why people often neglect to consider it's contribution to a diamond's beauty; when a diamond is set, typically only the crown stands out prominently, and the girdle and pavilion are hidden beneath prongs or bezels. They seem to serve only as the utilitarian purpose of providing a way to hold the diamond in place. However, it is this hidden part of the diamond that is the key to brilliance. The secret is in the pavilion angles, which, in a round diamond, should typically be between 40.5 and 41.5 Degree.
Bow Ties are directly related with fancy accounts. They are light reflected back to the eye from the pavilion. It differs from point to point within any given diamond. This effect is manifested in the form of tiny patterns, known as bow ties, in the diamond's center. They look like a man's bow tie. They are a very important part of the fancy cut. They are directly responsible for the diamonds brilliance. The difference is that most fancy shapes require deeper pavilions than round diamonds do in order to achieve the same amount of brilliance.