A diamond's beauty is visible to anyone. Its quality, however, is written in a language most buyers never learn: a few lines of grades, measurements and proportions on a grading report. Learn to read that page and you'll never overpay for sparkle again.
The short answer: most lab-grown diamonds are graded by IGI (International Gemological Institute), which uses the full 4Cs scale: carat, cut, colour and clarity, plus polish, symmetry and growth method. Since October 2025, GIA no longer gives lab-grown diamonds individual colour and clarity grades; it classifies them simply as "Premium" or "Standard". For engagement ring buyers comparing stones side by side, a detailed IGI report offers the most granular information.
Why a Grading Report Matters
Two diamonds can share a carat weight and look completely different. One may blaze with light; the other may look glassy or dark. The report explains why. It gives you:
- Independent verification of the stone's quality, not just the seller's description.
- A fair basis for comparison between stones and between retailers.
- Proof of origin, confirming the diamond is laboratory-grown.
- Insurance documentation for valuation and replacement.
- An identity, via a laser inscription on the diamond's girdle that matches the report number.
IGI vs GIA: The Lab-Grown Landscape in 2026
The grading landscape changed significantly in late 2025, and it's worth understanding before you buy.
|
Feature |
IGI lab-grown report |
GIA Lab-Grown Diamond Quality Assessment |
|---|---|---|
|
Colour grade |
Full D–Z scale |
Not given individually |
|
Clarity grade |
Full FL–I scale |
Not given individually |
|
Overall classification |
4Cs grades |
"Premium" or "Standard" |
|
Growth method noted |
Yes (CVD or HPHT) |
Laboratory-grown confirmed |
|
Laser inscription |
Yes |
Yes |
|
Market share in lab-grown |
The dominant grader |
A small share |
Under GIA's current system, a "Premium" stone must be D colour, at least VVS clarity, with excellent polish and symmetry (and an excellent cut grade for round brilliants). "Standard" covers E to J colour with VS clarity. Stones below that threshold receive no GIA report at all. IGI has continued to apply the same 4Cs scale it uses for natural diamonds.
Reading the Report, Line by Line
Report Number and Inscription
A unique number, usually laser-inscribed on the girdle alongside the words "Laboratory-Grown". Ask your jeweller to show you the inscription under a loupe; it should match the report exactly. You can also verify the number on the laboratory's website.
Shape and Cutting Style
Round brilliant, oval, emerald, cushion, pear and so on. Shape is personal taste; cutting style tells you how the facets are arranged.
Measurements
Length, width and depth in millimetres. Two stones of identical carat weight can have very different face-up sizes. A shallow-cut stone looks bigger; an overly deep one hides its weight underneath.
Carat Weight
Weight, not size. One carat equals 0.2 grams. Prices jump at "magic" weights such as 1.00ct and 1.50ct, so a 0.95ct stone can offer near-identical looks for noticeably less.
Colour Grade
On the D–Z scale, D is completely colourless. In a white-metal setting, G to H looks icy white to most eyes. In yellow or rose gold, you can comfortably go lower, as the metal warms the stone anyway.
Clarity Grade
From Flawless (FL) to Included (I). VS1 and VS2 stones are usually "eye-clean", meaning no inclusions are visible without magnification. That's the sweet spot for value.
Cut Grade, Polish and Symmetry
The most important line on the page. Cut determines brilliance, fire and scintillation. For round brilliants, insist on Ideal or Excellent. Polish and symmetry should be Very Good or Excellent.
Growth Method and Treatment
IGI reports note whether the stone was grown by CVD (Chemical Vapour Deposition) or HPHT (High Pressure, High Temperature), and whether any post-growth treatment was applied to improve colour. Both methods produce real diamonds. A treated stone isn't inferior, but it should always be disclosed.
Fluorescence
A soft glow under UV light. In lab-grown diamonds it's generally uncommon and rarely affects appearance.
The Value Sweet Spot for an Engagement Ring
|
Specification |
Sweet spot |
Why |
|---|---|---|
|
Cut |
Ideal / Excellent |
Sparkle is non-negotiable |
|
Colour |
F–H |
Looks white, avoids the D-colour premium |
|
Clarity |
VS1–VS2 |
Eye-clean without paying for invisible perfection |
|
Carat |
Just under a magic weight |
More stone for your rand |
|
Polish / Symmetry |
Very Good or better |
Crisp facet definition |
Red Flags to Watch For
- No report, or an in-house "certificate" issued by the seller rather than an independent laboratory.
- A report that doesn't match the inscription.
- Vague language such as "near colourless" in place of a stated grade, if you're expecting a detailed report.
- Undisclosed treatment or a missing growth method.
- Unrealistic pricing that seems too good for the grades listed.
Frequently Asked Questions
Is IGI or GIA better for lab-grown diamonds? For lab-grown diamonds, IGI provides the most detailed grading, using the full colour, clarity and cut scales. Since October 2025, GIA classifies lab-grown diamonds only as "Premium" or "Standard" rather than giving individual grades.
What does CVD or HPHT mean on a diamond report? CVD (Chemical Vapour Deposition) and HPHT (High Pressure, High Temperature) are the two methods used to grow diamonds in a laboratory. Both produce real diamonds with identical properties to mined stones.
What clarity should I choose for a lab-grown engagement ring? VS1 or VS2 clarity offers the best value for most engagement rings. These grades are typically eye-clean, meaning inclusions aren't visible without magnification.
How can I check a lab-grown diamond report is genuine? Enter the report number on the grading laboratory's website and confirm the details match. Then ask your jeweller to show you the laser inscription on the diamond's girdle under magnification.
Conclusion
A grading report turns a beautiful stone into an understood one. Read the cut grade first, look for eye-clean clarity, choose a colour that suits your metal, and always match the inscription to the paperwork.
PURA sources certified lab-grown diamonds for bespoke engagement rings and fine jewellery. Visit pura.co.za to speak to our team, and we'll walk you through every line of your diamond's report before you choose.