What are Diamond Cut Grades?

  • August 2, 2019
  • In Diamonds
  • By DiamondsForever

Diamond cut is less about shape and more about how well the facets on a diamond interact with light. Facets are like tiny mirrors that work to reflect light in and out of a diamond. When they are just right, they show it by an intense shine and sparkle.

So what does diamond cut mean to you? The cut of diamonds has to do with symmetry. It is the most important factor in how beautiful a diamond is. It impacts brilliance (how white light is reflected), fire (flashes of color) and scintillation (how it sparkles). A diamond of any carat weight, color, or clarity without the brilliance, fire, and scintillation is a non-starter.

When a diamond is cut from rough stone, there is understandable pressure to end up with as much carat weight (size) as possible. When cut is sacrificed for carat weight, it usually results in a diamond that is not cut well. This in turn negatively impacts how light moves through a diamond. The thing that makes a diamond a diamond is missing-in-action when a diamond is cut poorly.

Diamond Cut Chart

Of the “Four C’s,” the cut is the hardest one to wrap ones head around. But it’s the most crucial in understanding value. The beauty of a well-cut diamond is apparent to the naked eye. What’s harder to understand is its underlying elements.

A well-cut diamond allows for most of the light entering the diamond to exit back through the top. This leads to intense fire and sparkle. A poorly cut diamond causes light to leak out of the bottom or sides, lessening that sparkle.

How Does Diamond Cut Affect Beauty and Price

What is a diamond cut and what does a diamond cutting grade mean? When you see a 3-carat diamond with a poor cut grade, you can be assured that cut was sacrificed for carat weight. A well-cut 2-carat diamond will have more fire and brilliance than a poorly-cut 3-carat diamond. The larger diamond may still cost more overall, but the well-cut smaller diamond will cost more per carat. The reason is that it may have been more expensive to produce (due to significant loss of rough stone). On the upside, a well-cut diamond can appear larger.

GIA cut grades range from “Poor” to “Excellent” and are based on several factors, including a diamonds face-up appearance (brightness, fire, scintillation), design (weight ratio, durability), and craftsmanship (polish, symmetry).

The shape of a diamond plays some part as far as brilliance and cost. Some shapes are more expensive to cut because their very shape dictates more rough stone be lost. Round cut diamonds are generally more expensive because of this. Emerald, princess, and cushion-cut diamonds are generally more affordable because their shapes dictate less loss of rough stone. Heart-shaped diamonds are the most expensive for the same reason as rounds.
 

Diamond Depth Percentage

Diamond depth percentage refers to the distance between the table (top) and the culet (bottom). It’s calculated by dividing the depth by the width. The lower the diamond depth percentage, the larger a diamond will appear. The ideal diamond depth percentage helps the table refract light as it enters the diamond and redirects it from the lower part of diamond back to the eye of the beholder.

Diamonds that sacrifice cut for carat weight can have an out-of-whack depth percentage. Bad depth percentage can either be too deep or too shallow. Both can cause visually unappealing consequences. A diamond with too shallow of a depth can cause most of the light to exit the bottom of the diamond. Too deep, light leaks out the sides. The latter will reduce a diamond’s sparkle and fire and thus impact its value negatively. An ideal depth percentage will heighten sparkle and thus impact value positively.
 

Diamond Table Percentage

A diamond’s table is the window into the soul of a diamond. If a table is too large, it will hinder how the light plays off the other facets. If too small, light will get trapped inside the diamond and be forced to leak out the bottom or sides. So while a larger table can help a diamond look larger, the effect can be lost if less light leaves the top (less light leaving the top of a diamond can cause it to appear smaller).

A diamond’s depth percentage and diamond’s table percentage play a major role in how beautiful a diamond is (or is not). A diamond’s table percentage is calculated by dividing the width of the table (top) by the total diamond width. The ideal table percentage will vary depending on the shape of gemstone (round, emerald, etc).

Anything that causes light to reflect poorly will impact value negatively. Alternately, a diamond that has an ideal table percentage will have more sparkle and thus impact value positively.
 

Diamond Proportion

How a diamond is proportioned determines its sparkle. Diamond proportion refers to the relationship between each facet’s size, shape, and angle. Facets are like tiny mirrors. Where they are positioned impacts how light travels through a diamond.

Whenever light hits a facet of a diamond, it either immediately bounces back (reflects) or bends (refracts). Reflection causes that shine and refraction causes that sparkle. The latter is due to light scattering as it moves through a diamond. It also creates dispersion (that fiery rainbow effect).

A well proportioned diamond will have facets angled to maximize its interaction with the light. A proportional flaw of the facet structure affects a diamond’s appearance by altering how light travels through it. Misshapen and misaligned facets or a table that is off-center can negatively impact sparkle. The main reason a diamond cutter might mess up the proportions of a diamond would be in the name of maintaining as much carat weight as possible from the rough stone. If the symmetry of the facets is off even a little bit, the light won’t refract properly. This can cause light to drain out of the bottom making a diamond look dull.

A dull diamond is definitely worth less than a sparkly diamond. There are no set ideal proportions. It really depends on the visual appearance of the stone (how light passes through it).

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