Last updated on October 28, 2020
Cut quality is probably the most important characteristic of a diamond as it is the defining feature to maximize your stone’s brilliance, sparkle and overall beauty. Perhaps you have already heard the term “ideal diamond cut” but have you ever thought what exactly it means and how to define if the diamond you are looking at has too deep or too shallow cut?
What is a Diamond Cut?
In terms of cut quality, the term “cut” should not be confused with both the diamond shape, which can be round, oval, cushion etc, and facet arrangement which can be brilliant or step.
The cut is the biggest indicator of a diamond’s beauty and should be made a priority over the other 3 Cs. A diamond with no inclusions or colour tints will still look dull if it’s not cut exceptionally well. No precision, no brilliance and sparkle.
According to the Gemological Institute of America (GIA) diamond cut grades on a scale of Excellent, Very Good, Good, Fair and Poor. Excellent cut diamonds provide the maximum brilliance and fire, while poorly cut diamonds look dull.
What is an Ideal Diamond Cut?
Coined by a famous diamond cutter Marcel Tolkowsky back in the 1900s, the term “ideal diamond cut” refers to such proportions and angles when a diamond exhibits maximum brilliance and sparkle.
An ideal cut diamond has excellent polish and symmetry and reflects almost all the light that enters it. In other words, the ideal diamond cut is the highest possible standard which is also used as a benchmark for grading all diamonds.
While Tolkowsky’s ideal cut standards serve as a global guideline for today’s diamonds, some countries have made their modifications. There are at least six “ideal cut” standards being used today in the diamond industry but only three of them, including the one by Marcel Tolkowsky, are the most common.
What is a Deep Diamond Cut?
A diamond’s total depth or height is measured from the surface of the table to the culet, in other words from top to bottom. This measurement is expressed as a percentage of the average girdle diameter (Total Depth % = Total Depth (mm) / Average Girdle Diameter x 100).
Total depth percentage is one of the main factors when determining a diamond’s cut grade. When a diamond has the right combination of total depth and girdle diameter, it is more capable of reflecting light which results in a stronger and more beautiful sparkle.
When a diamond’s total depth is too high relative to the average girdle diameter, it is said that the diamond is too deep. As a result, the light doesn’t reflect properly, and the diamond looks less lively and have lower brightness compared with more proportional ones. In general, the deeper the cut of the stone, the duller it looks.
Moreover, deep cut diamonds look smaller than ideal cut diamonds of the same carat weight when set in a mounting. This effect appears because the cutter sacrifices of the stone’s width to achieve a greater depth. When the stone is set in a mounting, the additional depth is hidden in it so the only visible part is the diamond’s top, which is smaller than of the ideal cut diamond.
What is a Shallow Diamond Cut?
When a diamond’s total depth is too low relative to the average girdle diameter, it is said that the diamond is too shallow or spread (spready).
Shallow diamonds lack depth compared to ideal cut diamonds which is why most of the light entering does not reflect through the table but leaks out from the bottom of the stone (pavilion) sacrificing its brilliance and sparkle.
Moreover, shallow cut diamonds tend to exhibit a “fish eye effect” which occurs when the girdle of a diamond is reflected under the table facet. This phenomenon always detracts from the beauty of the stone.
The reason for shallow cut diamonds is to make them look bigger as from above spready diamonds look wider than normal and it seems that they are of larger carat size. Sadly, some shoppers blindly focus on “bigger and cheaper” diamonds without thinking of the overall beauty of the stone and the money they simply waste on such stones.