Lab Diamond Certificates (LGD): Why IGI Is Beating GIA in the Lab-Grown Market, How to Read an LGD Report.

Lab-grown diamonds (LGDs) now make up a big share of engagement ring sales, and certifications are how you compare them with confidence. The lab on the report affects price, trust, and resale. Today, IGI grades most lab-grown diamonds in the retail market, even though GIA is the best-known name for natural diamonds. Here’s why IGI is leading for LGDs, how it differs from GIA, and how to read an LGD report without getting tripped up.

What an LGD Certificate Is—and Why It Matters

A lab diamond certificate (or grading report) is an independent assessment of the stone. It documents the 4Cs (carat, color, clarity, cut), measurements, fluorescence, and identifying marks. For lab-grown, it also discloses the growth method (CVD or HPHT) and any post-growth treatment.

Why it matters:

• Pricing: Two diamonds with the same grades will be priced closer together. Different labs can shift price because buyers trust some labs more.
• Verification: The report number is laser-inscribed on the girdle. You can verify the report online and match it to the stone.
• Disclosure: For LGDs, clear wording on “laboratory-grown,” growth method, and treatment prevents misrepresentation.

Why IGI Is Beating GIA in the Lab-Grown Market

GIA built the modern grading system and dominates natural diamonds. Yet for LGDs, IGI has the larger market presence. The reasons are practical.

• Speed and capacity: IGI built high-throughput grading in manufacturing hubs (India, China, Hong Kong, and others). Growers and cutters can ship locally, get faster turnaround, and keep inventory moving. Speed lowers carrying costs, which matters in a fast-changing LGD price landscape.
• Cost: IGI grading fees are often lower for the volumes LGD suppliers submit. Lower costs mean lower retail prices or higher margins—both attract sellers.
• Earlier LGD focus: IGI embraced LGD transparency and standardized D–Z color and FL–I clarity language early. Retailers got the simple, familiar 4C format shoppers expect.
• Retail integration: Many large chains and online sellers standardized on IGI for LGDs. Once a supply chain is built around a lab’s workflow and API/reporting tools, it tends to stick.
• Feature set for LGDs: IGI reports highlight growth method (CVD or HPHT) and post-growth treatment clearly. That makes it easy to merchandise “as-grown” vs. “treated” and meet disclosure rules.

GIA has updated its LGD reports over the past few years and now uses the same color and clarity scales as natural diamonds, with clear “Laboratory-Grown” wording. GIA remains the gold standard for natural stones and is respected for LGDs. But in practice, IGI’s speed, cost, and footprint near growers keep it ahead in LGD market share.

Are IGI Grades “Softer” Than GIA?

People often ask if IGI grades looser. The truth is nuanced:

• Color and clarity: On average, differences between IGI and GIA are small. You may see a half-grade to one-grade variance case by case. That happens between any two labs and even between different grading events.
• Cut: For round brilliants, GIA’s top cut grade (Excellent) is known to be conservative. IGI also awards “Excellent.” Some sellers feel IGI awards more Excellents, but the stone’s actual proportions and light performance matter more than the label.

What to do: use the report to shortlist, then judge the diamond itself—ideally with images/video and proportions. If you’re comparing a GIA-graded LGD with an IGI-graded LGD, expect close but not identical results. Buy with a return window and verify the inscription.

How to Read an LGD Report (Step by Step)

Whether it’s IGI or GIA, most LGD reports follow a similar flow. Here’s how to read it and what to look for.

• 1) Identification and verification
  • Lab name and report number: This is the diamond’s ID. The girdle should be laser-inscribed with the lab name and report number, plus clear “LABGROWN” or “Laboratory-Grown.” Match these exactly.
  • Digital check: Enter the report number on the lab’s website or scan the QR code. Confirm the 4Cs, measurements, and any remarks match the physical stone.
• 2) The 4Cs
  • Carat: Weight in carats, to two decimals. Example: 1.56 ct.
  • Color: D (colorless) to Z (light tint). LGDs often skew high color (D–F) because growers can target it. If your metal is yellow gold, G–I blends well; in platinum or white gold, F–H looks crisp.
  • Clarity: FL–I3. For most buyers, VS2–SI1 can be eye-clean and better value than VVS grades. Check the clarity plot to see inclusion type and location.
  • Cut (rounds only): Excellent/Very Good/Good. Cut drives sparkle. In practice, a “tight” Excellent with good angles outperforms a loose one. Fancy shapes (oval, emerald, cushion, pear) often have no overall cut grade; you must judge proportions and look.
• 3) Growth method and treatments
  • Growth method: CVD or HPHT. CVD often produces Type IIa material (very pure). HPHT can also be excellent, but may show metallic inclusions. This does not affect durability, only appearance if inclusions are eye-visible.
  • Post-growth treatment: Look for “None,” “HPHT,” “annealed,” or “as grown.” These are stable, permanent processes. Why it matters: some shoppers prefer “as grown” for principle, while treated stones can be priced more aggressively. Either way, disclosure should be clear.
• 4) Measurements and proportions (critical for round brilliance)
  • Dimensions: Example: 7.50–7.53 × 4.60 mm. This confirms carat-to-size spread.
  • Depth % and Table %: For rounds aiming at top light return, target roughly 61.0–62.5% depth and 54–58% table.
  • Crown and pavilion angles: Strong pairs are about 34.0–35.0° crown with 40.6–40.9° pavilion. These combinations minimize light leakage. Slight deviations can still perform, but extremes risk dullness or leakage.
  • Girdle and culet: “Medium–slightly thick” girdle is safe. Culet usually “None.”
  • Hearts & Arrows: Sometimes noted by IGI as a comment. Treat it as a pattern description, not a performance guarantee—confirm with actual imagery.
• 5) Finish and fluorescence
  • Polish and symmetry: Excellent/Very Good ideally. These affect how cleanly facets reflect light.
  • Fluorescence: None–Strong (usually blue). Faint–Medium is often neutral. Strong blue can make a J–K look slightly whiter in daylight but may turn hazy in some stones—check in different lighting.
• 6) Clarity plot and comments
  • Inclusions: For CVD, you might see needles or internal graining; for HPHT, small metallic pinpoints/crystals. Prefer inclusions off the table and near the edge. Avoid large, dark inclusions under the table.
  • Type designation: Many LGDs are Type IIa (very low nitrogen). It’s a nice-to-know, not a must-have.
  • Laser inscription details: Confirms lab-grown status and report number. This protects you from natural-vs-lab mix-ups.

Practical Buying Targets (Using the Report)

• Round brilliance sweet spots: Cut Excellent, depth 61–62.5%, table 54–58%, crown 34–35°, pavilion 40.6–40.9°, polish/symmetry Excellent or Very Good. This combination usually yields strong fire and brightness.
• Color: F–H for white metals; G–I for yellow gold. Go higher if you’re sensitive to tint or shopping a step-cut (emerald/asscher) that shows color more.
• Clarity: VS1–SI1 often looks clean to the eye. Verify with images/video, not just the grade.
• Fluorescence: None–Medium is safe. If Strong, view it in daylight and UV-rich lighting to ensure no haze.
• Fancy shapes: No lab cut grade. Use the report to filter (avoid very deep stones that face up small), then rely on videos and ASET/ideal-scope images if available. For ovals and pears, watch for dark bow-tie; the report won’t show it.

IGI vs GIA: Which Certificate Should You Choose?

If you’re buying a lab-grown diamond:

• IGI gives you broad availability, quick verification, and clear LGD disclosures. You’ll see more IGI-graded options at most retailers, especially in higher carat weights and fancy shapes.
• GIA carries strong brand recognition and consistent methodology. You may pay a small premium from some sellers because of that name recognition.

In both cases, the report is a tool—not the final verdict. Diamonds are individual. Let the report narrow your list. Then confirm performance and appearance with proportions, images, and return rights.

Red Flags and Easy Wins

• Red flags:
  • Report can’t be verified online or doesn’t match the inscription.
  • Lab-grown status is not printed clearly, or growth method/treatment is missing without explanation.
  • Unusual combinations (e.g., very high color with very strong fluorescence) without a video or inspection option.
• Easy wins:
  • Pick eye-clean over paper-clean: VS2 or SI1 that looks clean beats VVS on a tight budget.
  • Prioritize cut and proportions for sparkle. Color and clarity matter less once the stone is eye-clean and faces up white.
  • Confirm the laser inscription and keep the report PDF—helpful for insurance and resale.

Bottom line: IGI’s speed, scale, and LGD-first features made it the default for lab-grown diamonds, while GIA remains a respected option. Choose the certificate that gives you the inventory and confidence you need, but judge the diamond by how it looks and performs. The report gets you close; your eyes make the final call.