You've been told to always buy a certified diamond. Good advice. But when you start shopping, you'll encounter two names most often: GIA and IGI. Both are legitimate certification bodies. Both are widely accepted in the jewellery industry. But they are not identical and understanding the difference will help you shop more confidently.
What Does Diamond Certification Mean?
A diamond certificate (also called a grading report) is a document produced by an independent gemological laboratory that assesses and records the characteristics of a specific diamond. The grader examines the stone under controlled conditions and assigns grades across the Four Cs — Cut, Colour, Clarity, and Carat — along with additional details about the stone's proportions, fluorescence, and any significant inclusions.
The certificate is independent of the jeweller, it is not produced by the person selling you the stone. This independence is what makes it valuable.
GIA — Gemological Institute of America
GIA is the world's most recognised and respected gemological laboratory. Founded in 1931, it established the 4Cs grading system that the entire diamond industry uses. GIA grading is considered the industry gold standard globally.
GIA grades conservatively. This is important. GIA's colour and clarity grades are applied with strict consistency, a stone graded VS1 by GIA is reliably VS1. This conservatism means you can trust the certificate accurately represents the stone.
GIA certified diamonds carry a price premium. Because the market recognises GIA's authority, diamonds with GIA certificates typically command slightly higher prices than equivalent stones with other certificates. For buyers, this premium reflects genuine assurance.
IGI — International Gemological Institute
IGI is the world's largest independent gemological laboratory network, with grading facilities across multiple continents. It is particularly widely used for lab-grown diamonds — the majority of certified lab-grown stones carry IGI reports.
IGI grades slightly more generously than GIA. Industry analysis has consistently found that IGI assigns slightly higher colour and clarity grades to comparable stones than GIA would. This doesn't mean IGI certificates are fraudulent — but it does mean an IGI-graded stone may not be exactly equivalent to a GIA stone of the same stated grade.
For lab-grown diamonds, IGI is the standard. In this segment of the market, IGI's dominance makes it the practical choice. GIA also certifies lab-grown diamonds, but IGI has the larger share.
Which Should You Choose?
For natural diamonds, a GIA certificate offers the most reliable assurance. If two comparable stones are on offer at similar prices — one GIA, one IGI — the GIA stone is the safer choice for long-term value.
For lab-grown diamonds, IGI is widely accepted and perfectly appropriate. The secondary market for lab-grown stones is limited regardless of certificate, so the premium attached to GIA certification matters less in this category.
The most important thing in either case: the stone should have a certificate. Buying an uncertified diamond from any laboratory is not recommended — you have no independent assurance of what you're actually purchasing.
At Lailah & Co., all our diamonds are certified by GIA or IGI and we walk clients through the grading report at every consultation. Book an appointment to understand exactly what you're buying before you commit.