The cut of a diamond refers to its proportions
Quite often the cut of a diamond is confused with its shape. Diamonds are cut into various shapes depending upon the original form of the uncut diamond, which is referred to as rough. Whatever the shape, a well-cut diamond is better able to reflect light.
A diamond's ability to reflect light determines its display of fire and brilliance. Diamonds are usually cut with 58 facets, or separate flat surfaces. These facetsfollow a mathematical formula and are placed at precise angles in relation to each other. This relationship is designed to maximize the amount of light reflected through the diamond and to increase its beauty.Well Cut - When a diamond is cut to proper proportions, light is reflected from one facet to another and then dispersed through the top of the stone. Within the Well Cut standards are the sub categories of Ideal, Excellent, and Very Good.
Ideal - This range is very strict and combines the best in brilliance and fire. Technically, the head of the class.
Excellent - This range is also of great beauty yet slightly more flexible regarding percentages. Many experts prefer the appearance of this range to Ideal.
Very Good - This range is balanced between precise proportions and price considerations. Viewed by many as the best overall value in beauty and price.
Deep Cut - When the cut of a diamond is too deep, some light escapes through the opposite side of the pavilion.Shallow Cut - When the cut of a diamond is too shallow, light escapes through the pavilion before it can be reflected.
The cut, or proportions, of a diamond is measured in percentages relative to the diameter of its girdle. The girdle diameter of each diamond is always considered 100%. Example: The girdle of a diamond measures 10 millimeters (100%). The table measures 5.6 millimeters. The total depth measurement is 6.1 millimeters. The diamond would be described as having a table of 56% and a depth of 61%. The table and depth percentages are the key to determining good proportions. Read About Color