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4Cs of Diamonds:
Diamond Cut

Round Diamond

For one to make an informed decision while shopping for a diamond, it’s crucial to understand the 4Cs – cut, clarity, color, and carat. These criteria are used by gemologists and jewelers worldwide to assess a diamond’s quality and value, and acts as a standard for diamond comparison. While a diamond’s carat, clarity, and color all play an important role, it should be noted that the foundation of its appearance lies with its cut, since it’s the cut that determines how the diamond will reflect light.

A well-cut diamond reflects light brilliantly and is a testament not only to nature, but also to modern technology and the skill of the diamond cutter. In this article, we’ll explore the importance of diamond cut, discussing exactly what it is, how it’s graded, and what role it
plays in diamond selection.

The Basics of Diamond Cut

In the diamond industry, the term “diamond cut” can refer to two aspects. It can sometimes refer to the actual shape of the diamond – princess cut, cushion cut – or it can refer to how well the stone was cut and faceted from its raw form. In this article, we are referring to the latter.

Diamond cut chart guide
Fig 1. An optimally cut diamond will have the right balance of depth and width to allow light to enter, reflect, and disperse in a way that maximizes its shine. Diamonds with a shallow or a deep cut can result in light leakage, where light escapes from the sides or bottom of the diamond, diminishing its brilliance, scintillation, and fire.

A diamond with an excellent graded cut is shaped and faceted to maximize light play; its physical dimensions are set up so that its facets work together to refract and reflect the maximum amount of light back towards the viewer out of the top part of the stone (table). This optimization of light reflection results in a greater level of brilliance, scintillation, and fire – the three characteristics that are the hallmarks of a beautiful stone.

  • Brilliance – Refers to the white light that a diamond reflects back to the viewer as it stands still
  • Scintillation: Refers to the patterns of light and dark that are observed as a diamond is viewed dynamically – when either the observer, the light source, or the diamond itself is moving.
  • Fire: Refers to the multitude of colors observed when white light is dispersed upon entering a diamond.

In a poorly cut diamond, the facets are arranged poorly, meaning that the light that enters the stone is leaked through the sides or the bottom rather than reflected back towards the viewer. Put in another way, a poorly cut diamond makes inefficient use of the light that enters it, leading to a dull and lackluster-looking gem.

Understanding Diamond Cut Grades by the GIA

The Gemological Institute of America (GIA) has a standardized grading system to evaluate diamond cut quality. This grading system has tiers that range from Excellent to Poor, and judges how well a diamond reflects light. The higher the cut grade, the more exceptional the brilliance, scintillation, and fire.

  • Excellent: Stones with an excellent cut have the proportions, symmetry, and polish needed to reflect nearly all of the light that enters them back towards the viewer (the table). An excellent cut means that the stone reflects a maximal amount of brilliance, scintillation, and fire.

  • Very Good Cut: With this cut, the stone still reflects most of its entered light through its top facet, producing a high degree of light play. These stones have more variability in their proportions than excellent cut ones, but nonetheless still exhibit a high degree of brilliance, scintillation, and fire.

  • Good Cut: A diamond with a good cut offers an excellent balance between cut quality and value. These diamonds still reflect light really well, but come at a more affordable price than higher tier cuts.

  • Fair and Poor Cuts: These diamonds have poor performance when it comes to light reflection; a significant amount of light that enters them is leaked out through the bottom or sides, leading to a dull appearance.

Components of a Diamond Cut

In addition to understanding diamond cut grade, it’s important to familiarize oneself with the components that contribute to a diamond’s cut, namely the proportions, symmetry, and polish of the diamond. An excellent cut diamond has three of these components optimized for the optimal amount of light reflection.


Illustration of a diamond's anatomy
FIg 2. Illustration of a rbrilliant ound cut diamond's anatomy

A diamond’s proportions refer to the relationship between its physical dimensions – namely the size, shape, and angle of its facets. These include the:

  • Table: The top flat surface of the diamond
  • Girdle: The wide part of the diamond
  • Crown: The part that is above the girdle
  • Pavilion: The bottom portion below the girdle
  • Depth: The height from the table to the culet (point at the bottom of the diamond)

In an excellent cut diamond, the proportions of all these physical parts are set in ratios that optimize the refraction and reflection of light. This means that most of the light that enters the stone exits through the table (the top facet of the diamond), reflecting brilliantly towards the viewer.


Diamond symmetry refers to how precisely aligned its facets are in relation to one another. A high degree of symmetry in a diamond means that its facets are well-aligned in a purposeful way that allows light to be directed through the stone optimally. High degrees of symmetry make efficient use of the light that enters a diamond, helping ensure that the stone will shine brilliantly. 


The polish of a diamond refers to how smooth its facets are. A well-polished diamond is one that allows light to enter and exit it with minimal interference. If a diamond’s polish is subpar – meaning it has scratches, scuffs, or disturbances on its facets – light movement throughout it can be hindered and the stone’s brilliance and beauty can be reduced.


As we wrap up our article, it’s clear that there’s a lot more to diamonds than what most would consider. Not all diamonds are equal, and the beauty and value of one depends heavily on a number of factors, namely its cut, clarity, color, and carat.

While pursuing the highest grades in each of these categories contributes to a stunning diamond, it also results in a higher price. The trick then, becomes choosing a stone that falls in line with your budget while balancing what you want from each C.

Compromises aside, it’s important to remember that a diamond’s visual appeal is heavily dependent on its cut, as the cut has a direct impact on brilliance, scintillation, and fire. It’s for this reason that cut is often considered one of the most important Cs.

In any case, choosing the right diamond for you and your situation is highly personal, and goes beyond choosing one just based upon metrics alone. No two diamonds are the same, and it’s for this reason why it’s important for one to be informed when making a purchase.

If you’re in the San Diego area and you’re looking to purchase a diamond, we invite you to our showroom where our team can help you with a professional consultation. We have over 40 years of experience in the jewelry industry, and also have a GIA graduate on-site, so you can rest assured that you’re in the right hands. Whether you’re looking for a loose diamond to include in a custom piece, or are shopping around for something to add to your collection, our team can help you get the perfect piece that will be enjoyed for years to come.