A well-cut diamond is vastly different from an uncut or poorly cut one. As a result, diamond cuts are key players in determining the value of a diamond. But how do we properly evaluate and check diamond cut quality?

It is fairly easier to check the diamond cut quality because any flaw in the cut is quite evident. This affects the stone’s brilliance and shine and often ends up looking disproportionate or asymmetrical. While assessing diamonds, gemologists and professions look at the diamond grading, which in turn includes diamond cutting grade.  

What is a Diamond Cut?

Cutting a diamond is the key to increasing its appeal and so, requires expert craftsmanship and skill. A common misconception is that diamond cut refers to its shape. Whereas in fact diamond cut involves the proportions, polish, symmetry and depth given to the stone. This goes on to determine the angle at which light enters the diamond. If the light does not enter at the best angle, the diamond will not reflect light properly. This will result in a dark and dull appearance, which in turn will decrease the diamond value.

Based on the final shape given to the diamond, names have been assigned to them. You may have heard of Princess cut or Emerald cut diamonds. While determining the diamond cut quality, these too are taken into account.

Checking the Brilliance of Diamond Cuts

Diamond cuts that allow maximum reflection of light sparkle the best. This is what we understand by a “brilliantly cut diamond”. For example, the Princess Cut proportions in a diamond are designed in this way. You can simply place two such diamonds side by side and observe their sparkle. The one that dazzles has a higher diamond cut quality.

The diamond cut quality of Round Cut diamonds can also be determined in this manner by comparing the brilliance of two stones.

On the other hand, checking the diamond cut quality for faceted cuts follow a different rule. While comparing diamonds with step or faceted cuts like Asscher or Emerald cuts, we should focus more on the proportions of the facets and whether or not the stone has been symmetrically cut.

 Checking Cut Grades of Diamonds

Having understood how to check for the brilliance of diamonds, let’s move on to checking diamond quality through cut grades.

You must have heard of GIA diamonds. Have you wondered why they are so valuable? The reason is that the Gemological Institute of America (GIA) is most trusted and reputed laboratory when it comes to assessing diamonds.

They have come up with a uniform grading system for diamonds with the following grade chart: Excellent, Very Good, Good, Fair and Poor.

Since GIA covers the most important factors to check diamond cut quality, their system of grading is followed by most laboratories. As a result, diamond cut grade is assigned on the basis of proportion, symmetry and dimensions that enhance the overall appearance of the stone.

Diamond Cuts and their Prices

Diamond cut quality is a key player in determining the value of a diamond. The better the cut, the higher its grading, and the more will be its price. As discussed above, diamonds of higher cut grade have brilliant proportions, symmetry and facets. In fact, of all the 4Cs listed by GIA: color, clarity, cut and carat weight, diamond cut is thought be the most critical. The reason is quite simple – only a well-cut diamond allows optimum reflection of light. And it is this sparkle that differentiates diamonds from any other stone. Thus, it comes as no surprise that diamond cut quality has such an important role to play in determining the price of diamonds.

To understand diamond cut quality, we need to understand the factors that affect it. Here, we have listed the parts and aspects of a diamond and the role they play:

• Girdle :

   

  This is the outer edge or diameter of the diamond. A well-cut diamond can be judged by looking at the thickness of the girdle. Ideally, the girdle should be of proportional thickness to the size of the stone. Therefore, it should not be too thick or too thin. Additionally, the girdle should also be even throughout otherwise the diamond will appear deformed.

• Culet :

   

  The culet refers to the flat portion of the diamond at the very bottom. Ideally, a culet should be very small. Many diamond cuts may not have a culet altogether.

• Table :

   

  The diamond table refers to the flat surface at the top of the diamond. Since we look at any diamond from the top angle through the table, it needs to be well cut and polished. A good balance of percentage between the table and depth needs to be maintained for a for high diamond cut quality.

• Depth :

   

  This is the distance between the table and the culet, i.e. the top and bottom of the diamond. The girdle divides the depth. The weight of any diamond is revealed by its depth. As a result, a good depth percent should be maintained for the overall appearance of the diamond.

Some other factors that affect diamond cut quality according to GIA

 To check the quality of a diamond cut, GIA diamond cutting grade consists of 7 factors. Of these, the weight ratio, durability, symmetry and polish assess the diamond’s craftsmanship.

Of these 7, the following 3 are the most important:  

• Fire:
  

  This refers to the flashes of light that occur due to prismatic effect occurring within the diamond.

• Brightness:
  

  Refers to the white light reflection, both internal and external, of the diamond.

• Scintillation:
  

  Highlights the contrasting light and dark areas so that each facet is clearly visible, giving the diamond a crisp appearance. 

Ideal Round Cut Diamond Proportions

Understated yet sophisticated, round diamonds are perhaps also the most versatile. A round diamond cut is a great choice for those who do not prefer big, chunky diamonds. Its simple elegance, paired with its high-range versatility makes it an all-time classic diamond cut.

When we talk of the most sought-after table percentage for round cut diamonds, it usually falls between the 53-58% mark.  Ideally you should go for round cut diamonds in this range.

Keep in mind that Round cut diamonds with table percentage less than 51% or greater than 64% are not recommended at all. The fall under “Fair” or even “Poor” in the GIA diamond cut quality grading chart. 

Ideal Princess Cut Diamond Proportions

The most popular choice for engagement rings, the Princess cut is elegant and sophisticated. Its square shape looks neat and crisp. Detailed layers are cut into the stone, making it resemble an inverted pyramid when viewed from the side. It is worth noting that Princess cut diamonds are cheaper than round cut diamonds. The reason is that the rough diamond is used more efficiently and very little of the stone is wasted during the cutting process of Princess cuts.

Unlike Round cut diamonds, the ideal table percentage for Princess Cut falls between the 60-75% range. Values either greater than 78% or less than 57% reveal lower diamond cut quality.

Similarly, the length to width ratio is also very important in Princess cut diamonds because of the role they play in determining the proportion od such stones. Thus, a Princess Cut should have a length to width ratio of 1:1 to 1.05:1.05.

Diamonds that have greater differences in this ratio will lose their preferred square shape. Rather, they will end up looking oblong or even rectangular and lose their visual appeal.

Ideal Cushion Cut Diamond Proportions

Unlike the Princess cut diamond which has sharp corners, the Cushion cut features square or rectangular diamonds with rounded corners. This gives it a somewhat soft appearance, resembling a pillow or cushion – hence its name. Cushion cuts are an extremely popular choice because they are less prone to damage and sparkle brilliantly.

The preferred table percentage for cushion cut diamonds have a broad range between 58-70%.

The depth percentage of the diamond should also preferably fall between the 58-70% mark for a higher diamond cut quality.

Ideal Oval Cut Diamond Proportions

Oval cut diamonds have an elongated shape, otherwise bearing resemblance to round diamonds in terms of its layers and facets. Oval cut diamonds are among the most popular choice for halo diamond rings where tiny stones surround the central oval stone. The end result is that the oval shape makes the ring appear bigger and more luxurious.

When we talk of the most sought-after table percentage for round cut diamonds, it usually falls between the 52-64%.  However, Oval cut diamonds with table percentage less than 50% and higher than 68% are not recommended.

Similarly, the length to width ratio for Oval Cut diamonds should ideally be between 1.25 to 1.60 for the best look.

 Ideal Emerald Cut Diamond Proportions

The brilliant emerald cut ring is a rarity. An emerald cut diamond requires extreme precision in its craftsmanship. The result is the sharp, chiselled appearance of the rectangular diamonds that sit on your fingers. Emerald cuts in diamonds are highly coveted due to their rarity and the concentric, rectangular faceted cut of the stone.

A table percentage falling between 60-70% are ideal for Emerald Cuts because they enhance the faceted-look of the stone.

 Ideal Asscher Cut Diamond Proportions

Blending the classic cuts of the Princess and Emerald style diamonds, the Asscher cut diamond rings are a timeless piece, maintaining their elegance and appeal for a long time. Their most important feature is that they are brilliantly faceted. The concentric cuts of the diamonds enhance clarity and allow optimum reflection of light, making the diamonds sparkle beautifully.

Like Emerald Cuts, the ideal table percentage for Ascher cuts also falls between the 60-70% mark. Avoid going lower than 55% and higher than 75% otherwise you’ll lose out on the crisp, neat look of the beautiful Ascher cuts.

 Bottomline

The points in this article have covered everything you need to know to get started on your quest of sell diamonds and understanding the key role played by diamond cut quality. Remember, when evaluating a diamond, it’s all about the balance between the most important factors.