Diamond Cut Chart Explained

Are you seeking your ideal diamond for your engagement ring in Melbourne? Read our detailed guide to learn more about the diamond cut chart and how diamonds are graded from poor to excellent cut. 

While each of the 4C’s play a role in a diamond’s overall quality, the cut is often considered the most crucial. It directly influences how a diamond interacts with light, affecting its brilliance, fire, and scintillation. The diamond cut is largely responsible for a diamond’s sparkle. 

Evaluating the Diamond cut grading pioneered by GIA, the highest cut grade diamonds receive is an ‘excellent’ cut for symmetry and polish. 

Continue reading below as we explain all you need to know about diamond cut grading, including how to interpret the GIA diamond cut chart. 

The Basics of Diamond Cut

Diamond cut refers to how well a diamond's facets interact with light. It involves the proportions, symmetry, and polish of the diamond. Unlike diamond shape (e.g., round, oval, marquise, emerald), which describes the external silhouette. The cut explains the craftsmanship of the diamond’s facets and how effectively the diamond reflects light.

A well-cut diamond will sparkle, dance with light, and appear larger and more brilliant than a poorly cut one. The cut and the facets determine how light enters, reflects, and exits the diamond, impacting its overall appearance and beauty.

What is the GIA Diamond Cut Grading Chart? 

The Gemological Institute of America (GIA) first established the 4C’s diamond chart in the 1950s, a criteria used to evaluate and describe a diamond’s cut quality.

The cut grading scale ranges from Excellent, representing the highest level of craftsmanship and light performance, all the way to Poor, indicating limited brilliance and fire. This grading scale is internationally recognised grading appears on all GIA, GCAL, and IGI diamond grading reports.

The most admired diamonds are those with an Excellent cut, as they reflect light in the most optimal way, creating maximum sparkle, brilliance, and fire.

As we examine diamond cut grading, it’s important to understand that diamonds are always assessed as loose stones prior to being set within an engagement ring.

What is the GIA Diamond Cut Scale

The GIA diamond cut chart is grouped into five categories that describe how effectively a diamond’s proportions and symmetry reflect light. 

The GIA's cut grading scale for Round Brilliant Cut diamonds is as follows:

• Excellent: Featuring ideal proportions, excellent symmetry, and polish. Reflects light that enters the diamond, exhibiting exceptional brilliance and fire.

• Very Good: Shows very well-balanced proportions and symmetry with high-quality polish. Reflects most light, offering excellent brilliance and fire.

• Good: Has reasonably good proportions, symmetry, and polish. Reflects a fair amount of light, with good brilliance and fire.

• Fair: Features average proportions and symmetry with acceptable polish. Reflects some light, with limited brilliance and fire.

• Poor: Lacks precise proportions, symmetry, or polish. Reflects very little light, lacking brilliance and fire.

Additional Grading Information about the Diamond Cut

Included on the Diamond grading report is Additional Grading information. Revealing further insights into a diamond's cut quality and finish. 

• Symmetry: Evaluates the symmetry of the overall diamond shape, including the precision of the diamond's facet alignment. Symmetry assesses the degree to which the diamond’s facets are all aligned and matching in shape and size. The grading scale ranges from “Excellent” being the highest through to “Poor”.  Gemological Diamond graders assess for any variations in angles, uneven facets, extra facets, misalignments any part of the diamond being off-centre to establish the final grade assigned to the diamond.
  
  

• Polish: Describes the quality of the diamond's surface after polishing, indicating how smooth hand free from blemishes the facets are. The grading scale also ranges from “Excellent” being the highest  through to “Poor” representing the lowest. Gemological Diamond labs look for any polishing lines, scratches, abrasions or burns on the surface of the stone during the polishing process to determine their final assessment of the diamond.
  
  

• Proportions: The proportions of a diamond on a grading certificate are portrayed through a detailed diagram. It appears on a certificate as the side view of the diamond accompanied with the angles and relative measurements of the stone. Diamond graders measure a diamond’s table size, total depth, pavilion depth, pavilion angle, crown height, crown angle, girdle thickness, lower girdle and cutlet to display the proportions and shape of the facets. The listed angles and ratios can be
   

These elements work together to influence how light interacts with the diamond, affecting its sparkle and overall appearance.

Beyond the 4C’s 

At JANAI, we go beyond the GIA 4C’s to measure a diamond's sparkle and how it interacts with light - using more advanced assessments such as Light performance to measure a diamond's Brilliance, Fire, Light symmetry or Light loss. Through 3D scanning, every diamond facet can be measured to exacting degrees and produce a detailed report. Assisting you in selecting a diamond with impeccable cut and optical qualities. Our consultants will guide you through every detail of light performance, so you can view how the diamond’s brilliance truly comes to life.

In-store we have analytical tools to determine how a diamond interacts with light, and to ensure a diamond's visual beauty through ideal cut and symmetry. Using tools such as ASET scope, H&A scope, Ideal Scope, during your consultation you may see the red pattern, which represents light return, contrast and light leakage. For a better understanding of the quality of your diamond cut.

The better the cut, the more a diamond will sparkle. A well-cut diamond creates that classic, unmistakable brilliance you expect. Conversely, a poorly cut diamond lacks light performance and appears dull. Many factors such as proportions, symmetry, and polish all contribute to the diamond's ability to reflect light effectively.

Hearts and Arrows Cut

For the finest in Diamond Cutting, Hearts and Arrows Diamonds embody a commitment to precision and excellence. The Hearts and arrows diamond cuts are the pinnacle of diamond craftsmanship. They are not just beautiful, but a testament to diamond cuttering mastery to showcase the highest standard of technical perfection.

Hearts and arrows diamonds achieve absolute precision in craftsmanship and symmetry. Revealing a contrasting pattern of eight arrows from above and eight hearts from below.

• Time to Cut and Polish: A Hearts and Arrows diamond takes around 3-4 times longer than the average brilliant cut to produce. 

• Distinctive Pattern: Hearts and Arrows cut deliver superior brilliance and unrivalled light performance and sparkle. 

• Ideal proportions: The angles and proportions of Hearts and Arrows cut diamonds are responsible for reflecting all of the light from the lower pavilions of the diamond to brightly sparkle from the top of the stone. 

Conclusion

Understanding diamond cut is essential for selecting a diamond that offers maximum brilliance and beauty. By focusing on cut quality and balancing the other 4Cs, you can ensure your diamond sparkles brilliantly and meets your expectations. During your appointment, our consultants at JANAI will assist in finding your perfect diamond for your Engagement Ring in Melbourne. 

To begin custom designing your ring, please fill out our booking form below.