When it comes to a diamond’s brilliance, cut is everything.
While all four C’s — cut, color, clarity, and carat — play a role in a diamond’s beauty, cut quality is by far the most important.
Even the most colorless and flawless diamond will appear dull if the cut is poor. In contrast, a beautifully cut diamond radiates life, fire, and sparkle — capturing every glimmer of light perfectly.
It’s also important to note: the cut grade officially applies only to round brilliant diamonds.
Fancy shapes — like oval, pear, marquise, cushion, or Asscher cuts — may not be assigned a formal cut grade on certificates, making expert selection even more important when shopping for these styles.
In this guide, Tang & Co. walks you through everything you need to know about diamond cut — what makes a diamond truly dazzle, and what to look for when choosing your perfect engagement ring.
What Is Diamond Cut, Exactly?
Diamond cut refers to how well a diamond’s facets are proportioned, polished, and aligned to maximize light reflection.
It affects a diamond’s sparkle, symmetry, fire, and even how large it appears.
When a diamond is poorly cut, it can look dull, lifeless, and smaller than its carat weight suggests — no matter how colorless or flawless it is.
It’s important to note that cut and shape are not the same:
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Shape describes the diamond’s outline (e.g., round, oval, pear).
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Cut describes the craftsmanship — the symmetry, proportions, and polish — that define the stone’s brilliance.
What Affects a Diamond’s Cut Grade?
1. Proportions
The relationship between a diamond’s table size, depth, and overall symmetry impacts how light travels through the stone.
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Table Percentage: The top flat surface (the table) should have the right proportion compared to the diamond’s width to reflect light beautifully.
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Depth: A diamond that's too deep or too shallow loses brilliance. Proper depth creates maximum sparkle and a lively, vibrant appearance.
Tang&Co Tip: Even a 1.00ct diamond can appear smaller (and less brilliant) if it’s poorly proportioned.
2. Symmetry
High-quality diamonds have excellent symmetry, where all facets are precisely aligned.
Perfect symmetry allows light to enter and exit the diamond evenly, creating that coveted fire and brilliance.
Poor symmetry reduces sparkle and causes light leakage, leading to a stone that appears dull.
3. Polish
After cutting, diamonds are polished to smooth any surface marks.
A well-polished diamond appears crystal-clear and maximizes light reflection, while poorly polished stones can look cloudy or scratched.
Diamond Cut Grades Explained
Diamond cuts are graded on a scale from Excellent to Poor:
| Grade | Description |
|---|---|
| Excellent | Superior brilliance, fire, and scintillation. The highest standard. |
| Very Good | Exceptional sparkle, almost indistinguishable from Excellent to the naked eye. |
| Good | Bright and attractive, though with slightly less scintillation. |
| Fair | Limited brilliance; noticeable darkness or dullness. |
| Poor | Poor proportions and symmetry; lacks sparkle and life. |
How to Choose a Diamond Based on Cut
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For Round Brilliant diamonds, rely heavily on the cut grade listed on the GIA or IGI certificate. Standards are strict for rounds, so Excellent and Very Good cuts are safe, sparkling choices.
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For fancy shapes (such as oval, pear, emerald, or Asscher), cut grades are often not listed.
In these cases, focus on proportions, symmetry, and visual appearance — examining 3D previews or videos is essential.
Tang&Co Tip:
Prioritize Excellent or Very Good cut grades for maximum brilliance. Save smartly by selecting a Very Good cut if you want stunning sparkle at a more accessible price point.
Final Thoughts
At Tang & Co., we believe the right cut unlocks the full beauty of a diamond.
A well-cut diamond radiates more brilliance, fire, and life — turning a beautiful stone into an unforgettable masterpiece.
When choosing your center stone, investing in cut quality ensures your diamond will shine with breathtaking elegance for a lifetime.