Math is the determining factor in deciding the cut of a diamond. Every diamond is cut according to an exact mathematical formula. The most common cut, the round brilliant, has 58 facets, or small, flat, polished planes designed to yield the maximum amount of light to be reflected back to the viewer.
This reflection, known as brilliance, is an extremely important factor in evaluating the quality of a diamond. A poorly cut diamond will actually lose light and appear dull. The two most common mistakes in cutting a diamond are:
Too Deep: Light escapes out the sides causing the diamond to appear dark and dull.
Too Shallow: Light is lost out of the bottom causing the diamond to lose brilliance.
A diamond's proportions refer to the Table Diameter, the Pavilion Depth, the Crown Angle, the Girdle Thickness, and the Culet Size. The calculations of these factors are confusing and involved, requiring complex mathematical formulations and expensive equipment to measure and calculate.
A diamonds brilliance is affected by:
a.) The depth of the diamond compared to its diameter
b.) The diameter of the table compared to the diameter of the diamond
All the facets of a diamond are not equally hard, it is therefore possible to polish and shape a diamond. The polish rating refers to the minute lines left on the diamond after the polishing process; these lines are straight in appearance. After cutting, each diamond facet is polished to improve the appearance and light return and so it is important to note all facets when considering this grade. If one of these facets has a burn mark from the polishing process then this will significantly affect the rating even though this may be unnoticeable when the diamond is set. A polish grade of good or higher will normally mean that no polish lines are visible to the unaided eye. However, below this rating polish lines may be visible, significantly reducing the overall brilliance of the diamond.
Symmetry refers to the alignment of a diamond's facets and its overall fire and brilliance. The light bounces around inside a diamond reflecting off the facets; if the facets are not properly aligned then the light will not be returned through the top of the diamond into the eye.* The symmetry of a diamond has an important influence on the overall appearance of the diamond, for example, if a round diamond has a poor symmetry then the overall appearance will not be round as the different sides of the diamond will not look the same.
* The term Hearts and Arrows is used to describe the visual effect achieved in a round diamond with perfect symmetry and angles, once this type of diamond is set the hearts and arrows pattern will not be visible.
Whilst the Color, Clarity, and Carat of a diamond are a good indication of the overall appearance of the diamond you will receive, they will often not be the final determining factors in the brilliance of the diamond and tehrefore the price of the diamond. Being that 98% of a diamond's brilliance is controlled by teh quality of its Cut those interested in teh most brilliant diamond should be aware of the diamond Cut. The industry has made this synonymous with the shape of the diamond but these are very different. When we refer to a diamond Cut we are in reality referring to the compilation of three main factors - proportion, polish, and symmetry of the facets of the diamond. It is important to understand these terms when comparing what may appear to be equal diamonds in terms of their Color, Clarity, and Carat weight with significant price differences.
Classification of Cut
All loose diamonds offered for sale are independently certified by recognized grading laboratories. It should however be noted that the different laboratories each use slightly different criteria with which to grade diamonds, and for this reason the same diamond could be graded by three independent laboratories and come back with three slightly differing reports. We understand that this can make it very difficult to compare diamonds that have been graded by different laboratories, and in recognition of this fact, our experienced in-house experts assign each diamond with a grade based upon current market trends and standards.
Shape refers to the contour and form of the stone. The most popular shape is the round, as the symmetry allowed with rounds leads to the most brilliant and reflective diamonds. Other popular cuts include Princess, Oval, Pear, and Radiant cut.