The Better Cut a Diamond, the More Brilliant
The way a diamond is cut may affect its value because a stone that is not properly proportioned lacks the brilliance of a well cut stone. A well cut or faceted diamond, regardless of its shape, scintillates with fire and light -- offering the greatest brilliance and value. While nature determines a diamond's clarity, carat weight and color, the hand of a master craftsman is necessary to release its fire, sparkle and beauty. If the diamond is cut with just the right proportions and at certain precise angles, the stone’s ability to reflect and refract light will be maximized; the diamond will sparkle at greatest capacity. When a round diamond is cut to Ideal proportions, light will bounce freely within the diamond and reflect back out of the crown without escaping through the opposite side or the bottom of the stone. Diamonds that are cut too deep or too shallow lose light that spills through the side or bottom. As a result, poorly cut stones will be less brilliant and beautiful -- and certainly less valuable -- than well cut diamonds higher on the Diamond Quality Chart. The diamond cutter will determine the stone’s brilliance and scintillation. Fancies are more subjective than rounds when it comes to proportions. Whereas there are sets of rules for round proportions, the same does not apply to fancies. The important factor is that the facets should be well aligned.
The girdle and culet is also other important part of the cut. The girdle rating indicates both the thickness of the girdle and whether it is polished or faceted. These two criteria affect the value and durability of a diamond. Girdle thickness ranges from extremely thin to extremely thick -- both extremes tend to lower a diamond's value. A medium rating is desired for the girdle, although diamond shapes with more than one point (i.e. pear or marquise) will often have a thick to very thick girdle in the area of the points. The culet is the tiny facet at the bottom of the diamond that looks like a point. The desired culet is small to very small, so that it is not visible through the top of the stone. A larger culet is often visible through the top and reduces brilliance at the center of the stone.
A top finish is important, because it directly affects the look of the diamond. It is the quality of the finish that unlocks the hidden beauty in the diamond. Two factors, polish and symmetry, indicate the finish of a diamond. These factors show the care and craftsmanship that went into the finishing of the stone.
Polish: The final finish must be perfectly void of any streaks or marks left over by the manufacturing process. A diamond's polish is a good indication of the care taken by the diamond cutter. The better the polish, the brighter and more lustrous the stone. Polishes rated excellent, very good, good, fair or poor.
Symmetry: Symmetry describes several factors of a diamond including how the facet edges align with one another, depending on the diamond facets of either side match, and whether the facets of the top portion of the diamond are aligned with corresponding facets in the bottom portion. A diamond’s facet needs to be of equal size and perfectly opposite its counterpart on the crown and pavilion. Symmetry should be graded as excellent, very good or good; if it is fair or poor, your diamond has been poorly cut and its value and beauty will be less.