Diamond Shapes: A Comprehensive Guide to Choosing the Right One

A diamond’s shape is one of its most defining and recognizable characteristics. It captures not only light, but also personality, emotion, and individuality. Whether for engagement rings, heirlooms, or fine jewellery, understanding diamond shapes is essential in appreciating their visual appeal and gemological significance.

In this blog, the International Institute of Gemology (IIG) offers an educational overview of the most popular diamond shapes, their features, and key considerations to help you make informed decisions—whether you’re a student, a buyer, or a jewellery professional.

Understanding Shape vs. Cut

Before diving into specific shapes, it’s crucial to distinguish between shape and cut, two terms often used interchangeably but with different meanings in gemology:

• Shape refers to the outline or form of the diamond (e.g., Round, Oval, Pear).
• Cut refers to the quality of the craftsmanship—how the diamond has been proportioned, faceted, and polished from rough. It directly affects the diamond’s brilliance and fire.

While one might say “Princess Cut” or “Round Cut,” it is technically more accurate to refer to the shape as Princess or Round, and discuss the cut grade separately.

How to Choose the Right Diamond Shape

Selecting a diamond shape is often a matter of personal preference. It should align with the wearer’s style, aesthetic, and the symbolic meaning one wishes to convey. While Round remains the most popular globally, several other shapes offer unique advantages and visual appeal.

Here’s a breakdown of 10 timeless and widely appreciated diamond shapes:

1. Round Brilliant

• Popularity: 60–70% of all diamonds sold.
• Features: 58 facets, unmatched brilliance and fire.
• Why Choose: Classic, universally flattering, ideal symmetry.
• Cut Type: Brilliant.

2. Princess

• Shape: Square with pointed corners.
• Features: Brilliant style cut with great sparkle.
• Ratio: 1.00 – 1.05 (ideal for a square appearance).
• Why Choose: Modern, youthful, and often appears larger than a round of equal weight.

3. Emerald

• Shape: Rectangular with step-cut facets and cropped corners.
• Features: Large open table, hall-of-mirrors effect.
• Ratio: 1.25 – 1.45.
• Clarity Tip: Choose VS1 or better to avoid visible inclusions.
• Why Choose: Elegant, vintage-inspired, refined symmetry.

4. Asscher

• Shape: Square version of the Emerald cut.
• Features: Step-cut with a high crown, deep pavilion.
• Ratio: 1.00 – 1.05.
• Why Choose: Art Deco aesthetic, bold symmetry.

5. Marquise

• Shape: Elongated with pointed ends.
• Features: Maximizes visible size, 58 facets.
• Ratio: 1.70 – 2.20.
• Note: May exhibit a bow-tie effect—a natural shadow seen in certain fancy shapes.
• Why Choose: Vintage glamour, makes fingers appear longer.

6. Oval

• Shape: Elongated Round.
• Features: 58 facets with excellent brilliance.
• Ratio: 1.30 – 1.50.
• Why Choose: Larger face-up appearance, timeless with a twist.

7. Radiant

• Shape: Rectangular with cropped corners.
• Features: 70 facets, brilliant-cut pattern.
• Ratio: 1.15 – 1.35.
• Why Choose: Combines Round brilliance with Emerald’s silhouette—ideal for modern tastes.

8. Pear

• Shape: Teardrop, with one pointed and one rounded end.
• Features: 58 facets.
• Ratio: 1.35 – 1.65.
• Why Choose: Expressive, flattering on the hand, often chosen for statement pieces or halo settings.

9. Heart

• Shape: Icon of romance; symmetrical with a cleft at the top.
• Features: Requires skilled cutting for symmetry.
• Ratio: 0.85 – 1.05.
• Why Choose: Sentimental value, ideal for romantic occasions like anniversaries or Valentine’s Day.

10. Cushion

• Shape: Square or rectangular with soft, rounded corners.
• Features: 58 larger facets for depth and fire.
• Ratio: 1.00 – 1.05.
• Why Choose: Old-world charm with a soft, pillow-like look—often preferred in vintage-style settings.

Understanding Length-to-Width Ratio (L:W)

For fancy-shaped diamonds (all shapes except Round), Length-to-Width Ratio is a vital metric. It determines how square, elongated, or proportionate the diamond appears.

• Formula: Length ÷ Width
• Example: A Princess cut measuring 4.50 mm × 4.45 mm has an L:W of 1.01—nearly a perfect square.
• Tip: Each shape has a recommended L:W range based on aesthetic norms, but individual preference always takes precedence.

What is the Bow-Tie Effect?

The Bow-Tie Effect is a visible shadow or dark area that sometimes appears across the center of certain fancy shapes—particularly Pear, Marquise, Oval, and Heart. While common, the extent of this effect varies with cut quality.

• Note: A well-cut diamond will minimize the bow-tie without sacrificing brilliance.
• Professional Tip: Always examine such shapes under different lighting conditions before making a purchase.

Conclusion: Let the Shape Reflect the Story

A diamond’s shape does more than define its appearance—it tells a story. Each cut carries with it symbolism, craftsmanship, and centuries of evolving design. Understanding the characteristics of different shapes helps you not only appreciate their beauty but also make more informed decisions as a consumer or gemologist.

At the International Institute of Gemology, we believe in empowering learners and professionals through deep knowledge and practical insights. Whether you’re a jewellery buyer, an industry professional, or a student of gemology, choosing the right diamond shape is a journey of discovery—and we’re here to guide you every step of the way.

For more educational articles, expert insights, and gemological training programs, visit www.iigindia.com