Buying an Oval Cut Lab Diamond

Cut Quality: The Key to a Brilliant Oval Diamond

Cut quality is the most important factor in determining how well an oval cut lab diamond reflects light. Unlike round diamonds, oval diamonds do not receive a formal cut grade from GIA, meaning buyers must assess proportions, symmetry, and facet alignment manually.

1. Ideal Proportions for an Oval Cut Diamond

A well-cut oval diamond should have balanced proportions to maximize sparkle and avoid excessive bow-tie effects. Here are the recommended ranges:

✔ Length-to-Width Ratio: 1.30 – 1.50 (ideal balance between elongation and symmetry)
✔ Depth Percentage: 60% – 67% (ensures light is reflected optimally)
✔ Table Percentage: 53% – 63% (controls light performance and brilliance)
✔ Symmetry: Excellent to Very Good (ensures even light distribution)

A poorly cut oval diamond can appear too deep or too shallow, leading to light leakage and reducing overall brilliance.

2. Why Symmetry and Facet Alignment Matter

Oval diamonds should have evenly distributed facets to avoid visual imbalances. Key points to check:

• The two rounded ends should be symmetrical, without one side appearing larger.
• The oval should have a pleasing, proportionate shape, not too long or too squat.
• Facet arrangement should create consistent brilliance across the entire stone.

3. Avoiding Poorly Cut Ovals

Some oval diamonds may have uneven curves, high depth percentages, or misaligned facets, affecting their sparkle. Buyers should always check high-resolution images or 360° videos to ensure the diamond has a well-balanced shape.

A well-proportioned oval cut lab diamond will maximize light performance, ensuring the best possible sparkle.

The Bow-Tie Effect: How to Minimize It

The bow-tie effect is one of the biggest challenges when selecting an oval diamond. This dark shadow in the center of the stone is caused by light obstruction and can range from barely visible to very pronounced.

1. What Causes the Bow-Tie Effect?

The bow-tie occurs when light entering the diamond is blocked instead of reflected, leading to a darkened area across the center. This happens due to:

• Poor facet alignment causing light leakage.
• Incorrect depth or table proportions preventing even light reflection.
• Shallow or overly elongated ovals creating unbalanced light dispersion.

2. How to Reduce the Bow-Tie Effect

✔ Choose a well-cut diamond – Balanced proportions and excellent symmetry help minimize the bow-tie.
✔ Look for even light return – Diamonds with strong brilliance will have less noticeable bow-tie shadows.
✔ View HD Videos and ASET Images – Assess the diamond in different lighting to check how dominant the bow-tie appears.
✔ Avoid overly deep or shallow stones – Diamonds with poor depth proportions often show stronger bow-tie effects.

Some mild bow-tie effect is natural in most oval diamonds, but well-cut stones will have minimal darkening and an overall bright, lively appearance.

By focusing on cut quality and symmetry and evaluating the bow-tie effect through imaging, buyers can select an oval cut lab diamond with maximum brilliance and sparkle.

Best Color and Clarity for Oval Cut Lab Diamonds

When choosing an oval cut lab diamond, color and clarity play a crucial role in ensuring the stone appears bright, clean, and beautiful. Since oval diamonds have a brilliant facet pattern, they can help mask certain inclusions but may show more noticeable color in their elongated body.

A Fancy Intense Yellow GIA 1.01 Carat Oval Diamond from James Allen

1. Best Color Range for Oval Lab Diamonds

✔ G-H Color – The best balance between whiteness and value. These diamonds appear bright white in most settings.
✔ D-F Color – Completely colorless, but with a higher price tag. Best for those who want an icy white appearance.
✔ I-J Color – Slight warmth may be noticeable, especially in larger ovals, but can still appear white in yellow or rose gold settings.

Oval diamonds show more color at the tips due to their elongated shape, so choosing a slightly higher color grade (H or above) ensures a bright and balanced look.

2. Clarity Considerations for Oval Lab Diamonds

Since oval diamonds have brilliant faceting, they hide inclusions better than step-cut diamonds (like emerald cuts). However, placement matters—inclusions near the center may be visible, while those near the edges can be hidden by prongs.

✔ VS1–VS2 Clarity – The best choice for eye-clean diamonds with no visible inclusions.
✔ SI1 Clarity – Can be eye-clean but requires careful evaluation with magnified images or 360° videos.
✔ VVS1–VVS2 Clarity – Virtually flawless, but not necessary for an eye-clean diamond.
✔ Flawless (FL-IF) – Extremely rare and unnecessary since even lower grades can appear identical to the naked eye.

3. Key Takeaways for Color & Clarity in Oval Lab Diamonds

• Stick to H color or higher for a bright white appearance.
• VS1-VS2 clarity provides the best balance of quality and value.
• Always check high-resolution images to ensure inclusions aren’t visible in SI1 diamonds.

Carat Weight and Size Considerations

Oval diamonds are known for their larger face-up appearance, meaning they appear bigger per carat than round diamonds. This makes them a great choice for those wanting maximum visual impact without overspending.

1. How Oval Diamonds Compare to Round Diamonds in Size

Oval diamonds have a larger surface area than round diamonds of the same carat weight, making them look bigger.

A 1.50ct oval diamond can look as large as a 1.75ct round diamond, allowing buyers to get a larger look at a lower price.

2. Ideal Length-to-Width Ratio for Oval Diamonds

The L/W ratio affects how elongated an oval diamond appears.

✔ 1.30 – 1.50 (Ideal Range) – Balanced shape, not too round or too stretched.
✔ Under 1.30 (Shorter Ovals) – May look wider and closer to a cushion shape.
✔ Above 1.50 (Long Ovals) – Can appear overly stretched and may have more noticeable bow-tie effects.

3. Carat Weight Price Considerations

• Oval lab diamonds are significantly more affordable than natural ovals.
• Prices increase at 1.00ct, 1.50ct, and 2.00ct+, so shopping just under these sizes (e.g., 0.90ct, 1.40ct, 1.90ct) can save money while still appearing large.
• Cut quality matters more than carat weight—a well-cut 1.50ct oval can look larger and brighter than a poorly cut 1.75ct oval.

Key Takeaways for Carat Weight in Oval Lab Diamonds

• Oval diamonds look bigger per carat than round diamonds.
• 1.30–1.50 L/W ratio creates the most flattering, balanced shape.
• Cut quality should be prioritized over size for the best brilliance.

Certification and Light Performance Imaging

When buying an oval cut lab diamond, certification ensures that the diamond has been accurately graded for color, clarity, and carat weight by a reputable gemological lab. However, because GIA does not provide a formal cut grade for oval diamonds, buyers must rely on proportions, symmetry, and light performance imaging to assess brilliance.

1. Best Certifications for Oval Lab Diamonds

✔ GIA (Gemological Institute of America) – One of the most trusted labs for lab-grown and natural diamonds, known for strict color and clarity grading.
✔ IGI (International Gemological Institute) – The most widely used certification for lab-grown diamonds, providing full 4Cs grading, including cut evaluation.
✔ GCAL (Gem Certification & Assurance Lab) – Provides cut precision and light performance grading, making it a great option for those prioritizing brilliance and symmetry.

2. Why Light Performance Imaging is Crucial for Oval Diamonds

Even with a high-grade certification, oval diamonds should ideally come with light performance images to verify their brilliance, bow-tie effect, and facet symmetry. The most useful imaging includes:

• Ideal Scope – Helps identify areas of light leakage, ensuring strong brilliance.
• ASET (Angular Spectrum Evaluation Tool) – Measures how efficiently the diamond reflects light, helping detect poorly cut stones.
• 360° HD Videos – Essential for checking bow-tie visibility, facet alignment, and overall sparkle.

3. Why You Should Avoid Buying an Oval Diamond Without Imaging

Because oval diamonds vary in shape, cut quality, and light return, purchasing without detailed images is risky. A diamond may look good on paper but have a severe bow-tie effect or poor symmetry, which won’t be reflected in the grading report.

Tip: Always choose vendors that provide detailed imaging and certification from a reputable lab to ensure the highest quality.

Best Places to Buy an Oval Cut Lab Diamond

Choosing a trusted retailer is just as important as selecting the right diamond. The best online vendors provide detailed imaging, light performance analysis, and strong return policies to ensure buyers receive a high-quality diamond.

1. Top Retailers for High-Quality Oval Lab Diamonds

✔ Whiteflash – Specializes in precision-cut lab diamonds with full light performance imaging and 360° HD videos, ensuring maximum brilliance. They also have a stellar reputation for customer service.
✔ James Allen – Offers 360° HD videos of most diamonds, allowing buyers to inspect clarity, symmetry, and bow-tie effects.
✔ Brilliant Earth – Known for ethical lab-grown diamonds with a wide selection and high-quality imaging.
✔ Blue Nile – One of the largest diamond retailers, offering GIA and IGI-certified lab diamonds, but light performance imaging varies.

2. Why Imaging and Certification Matter More Than Price

• Some vendors may offer lower prices but lack detailed imaging, making it harder to verify cut quality.
• The best value comes from choosing a well-cut, properly certified oval lab diamond with verified light performance data, rather than focusing only on size or discounts.

3. Key Takeaways for Buying an Oval Cut Lab Diamond

✔ Prioritize Ideal Proportioned ovals with balanced proportions and minimal bow-tie effect.
✔ Choose GIA, IGI, or GCAL certification to ensure accurate grading.
✔ Stick to H+ color and VS2 clarity for the best balance of quality and value.