Cut: One of The 4Cs of Diamond Quality

In days gone by, before diamond cutters were the technologically savvy, mathematical geniuses they've become in modern times, the rough diamonds worn as amulets paled in comparison to the tantalizing hues of rubies, sapphires, and emeralds. However, during The Age of Reason, man discovered the art of harnessing and redirecting light through a stone by placing carefully calculated facets into it. Thus, the diamond became, and will ever remain, the king of all stones. This very specialized art of cutting diamonds provides the foundation of what is known as the 4Cs of Diamond Quality. While Color, Clarity, and Carat Weight are extremely important factors in determining the grade and value of a diamond, it is Cut that rises above the pack in importance.

Brightness, Fire, and Scintillation

In the context of diamond quality, Cut refers not to the shape of a diamond, but to the size, number, and relative proportions of the facets placed on a diamond's surface {cited}. The characteristics of these facets nearly single-handedly determine the way light interacts with a particular diamond, thereby determining the Brightness, Fire, and Scintillation of that diamond.

• BRIGHTNESS is a measure of how much light is reflected from the polished facets within the stone and back through the crown.
• FIRE refers to the defraction of light through the stone's crystal structure. It is the fire in a diamond that releases the colorful rainbows that dance around the room.
• SCINTILLATION refers to the sparkling flashes of light a diamond produces when the stone, the wearer, or the observer moves.

It is these three attributes that give a polished diamond its dazzling and often mesmerizing beauty.

How the Cut Grade is Determined

Cut is the most crucial and "the only element of the 4Cs influenced by the human hand" {cited}. According to the Gemological Institute of America (GIA), "it is the most complex and technically difficult to analyze" {cited}. In addition to calculating a diamond's proportions--how its depth compares to its diameter, how its table diameter compares to its overall diameter, its weight in relation to its diameter, its girdle thickness, the symmetry of facet placement, and the quality of polish on its facets--the GIA Cut Grade also considers the overall design and craftsmanship of the stone. Adding to the complexity for consumers is the fact that the GIA Cut Grades are not applied industry-wide in the same way that clarity, carat weight, and color are. Experts report that retailers are free to assign cut grades based on whichever parameters they deem important. This leads to inconsistency in non-GIA-certified diamonds and can seriously affect the quality of the diamond you're about to purchase. By arming yourself with an understanding of the GIA Cut Grades and precisely how cut affects a diamond's interaction with light, and by taking the time to compare various diamonds side by side, you can ensure that you will choose the very best diamond for your very special occasion.

The Five Cut Grades

According to the GIA, there are five Cut Grades: Excellent, Very Good, Good, Fair, and Poor. If a diamond has a grading that differs from this wording, you can be sure the retailer is not using the GIA standards to determine cut. A diamond of Excellent Cut will reflect "nearly all of the light that enters it, creating exceptional sparkle and life" {Lumera Diamonds}. A Very Good diamond, under normal lighting, will reflect a significant portion of the light that enters it, rendering it observably similar to an Excellent Cut stone. A diamond graded Good will deliver "an above average appearance" by reflecting most of the light that enters it {Lumera Diamonds}. A Fair Cut is suitable primarily for smaller stones, as much of the light that enters the diamond will leak out the sides and bottom. Perceived fire and brilliance are greatly reduced in a Fair diamond. A diamond of Poor quality will appear dull even to the untrained observer. Very little of the light that enters the stone will reflect from the crown, having leaked out the sides and the bottom.

How Light Interacts With a Diamond

Experts agree that approximately 20% of the light that strikes a diamond is immediately reflected off the surface of the stone. The Cut of a diamond is what determines where the remaining 80% of the light will end up. In Excellent and Very Good cuts, nearly all of the light will bounce off of the precisely placed polished facets and back out through the crown (top) of the diamond, dazzling the eye of the observer. In the case of Good and Fair diamonds, due to a number of different factors related to symmetry and/or the depth of the pavilion, a portion of that light will either pass completely through the bottom or make a 90-degree turn and leak out the sides of the stone. Only a moderate amount of the light which enters will return to shine through the crown of the diamond to reach the observer's eye. Diamonds of Poor cut quality lose almost all of the light out the bottom or sides, resulting in a dull or drab appearance.

How to Determine Which Cut Grade is Best for You

While Excellent and Very Good cuts are the cream of the crop, they often cost more per carat than stones rated Very Good or Good. Especially when selecting a stone for a solitaire engagement ring, it is often economically advantageous to choose a larger stone with excellent clarity and color with a Cut Grade of Good, or even Fair, though it is never wise to sacrifice cut if the clarity and color of the diamond are low. Stones with a Cut Grade of Good or Fair should still flash with the brilliance and fire diamonds are so famous for, and they will be striking in their larger size. In order to elicit more sparkle from a diamond in this category, you may want to choose a setting that reveals as much of the pavilion as possible. That way, even the light leaking out the sides will catch the eye of the observer. Solitaire and tension set rings are ideal for this purpose. The surest way to determine which cut is best for you is to sit down with a diamond expert and compare diamonds of various cuts and sizes in various settings. Looking at loose and set diamonds side by side will demonstrate the subtle, and not so subtle, differences between the cut grades in proportion to carat size and color. There really is no substitute for seeing in person the play of light diamonds of high cut quality will manifest.