IGI vs GIA: Which Diamond Certificate Should You Trust? (2026)

Both IGI and GIA are respected diamond grading laboratories, and a certificate from either is far better than none at all. But for a lab grown diamond bought in 2026, an IGI certificate is arguably the more useful of the two, and the reason is a change GIA made in late 2025. IGI still grades lab grown diamonds on the full 4Cs, giving you the specific D colour and VVS clarity grades most buyers expect. GIA now sorts lab grown stones into just two categories, Premium and Standard. Here is what that means for you.

In this article

• The change that matters: GIA in 2025
• IGI vs GIA at a glance
• Does the lab affect the diamond itself?
• The one check to always make
• FAQ

The change that matters: GIA in 2025

For five years, from 2020 onwards, GIA treated lab grown diamonds much like natural ones: a specific colour grade, a specific clarity grade, the same vocabulary buyers already understood. That stopped in October 2025. Lab grown stones now come back from GIA labelled simply Premium or Standard. No D. No VVS1. Two boxes, and yours goes in one of them.

GIA's argument is reasonable enough on its face. Most lab grown diamonds cluster tightly at the top of the quality range these days, so splitting hairs between adjacent grades arguably tells you less than it used to.

There is logic to that. But if you are trying to compare two stones, or you simply want to know exactly what you are buying, Premium tells you far less than D colour, VVS clarity does. This is why IGI has become the practical choice for lab grown diamonds: it still gives you the granular detail, and it grades the large majority of lab stones on the market. Existing GIA reports issued before the change remain perfectly valid; nothing needs regrading.

IGI vs GIA at a glance

	IGI	GIA
Lab grown grading (2026)	Full 4Cs: specific colour and clarity grades	Two tiers: Premium or Standard
Natural diamond reputation	Highly respected	The historic gold standard
Share of lab grown market	Grades the large majority	A small share
Colour scale used	D-to-Z (same as natural)	D-to-Z for natural; tiers for lab grown
Best for a lab grown buyer	Yes: specific, comparable grades	Less informative since Oct 2025

Does the lab affect the diamond itself?

The honest answer is no. The certificate describes the diamond; it does not change it. A well-cut, D colour, VVS clarity lab grown diamond is exactly that whether the report is issued by IGI or GIA. What the lab affects is how much useful information the report gives you, and right now, for a lab grown stone, an IGI report gives you more.

This is the same point we make about how a diamond is grown: the method, and the lab, are lines on a certificate. What you actually wear is the stone. If you want the fuller picture on grading, our guide to whether lab grown diamonds are real covers how they test and certify.

The one check to always make

Whichever lab graded your diamond, both IGI and GIA laser-inscribe the report number onto the girdle, the thin edge, of the stone. It is invisible to the naked eye but readable under magnification. Always ask to see the inscription and match it to the certificate number. It is the simplest way to confirm the report in front of you belongs to the diamond in front of you, and any reputable jeweller will do it with you gladly.

A certificate is an independent description, not an appraisal and not a price. It tells you what the diamond is, not what it is worth. Buy the stone, verify the paperwork, and treat the two as one.

Frequently asked questions

Is IGI or GIA better for a lab grown diamond?

For a lab grown diamond in 2026, IGI is generally the more useful certificate, because it still grades on the full 4Cs with specific colour and clarity grades. Since October 2025, GIA reports lab grown diamonds only as Premium or Standard, which tells you less. For natural diamonds, GIA remains the most respected authority.

Why did GIA stop giving lab grown diamonds a colour and clarity grade?

GIA says the vast majority of lab grown diamonds now fall into a very narrow, high-quality range, so grading them on the full natural-diamond scale was, in its view, no longer meaningful. Since October 2025 it uses two tiers, Premium and Standard, instead.

Is an IGI certificate trustworthy?

Yes. IGI is an independent, globally recognised laboratory that grades the large majority of the world's lab grown diamonds using standardised conditions and multiple gemmologists. Its lab grown reports give you specific, comparable 4Cs grades.

Does an IGI or GIA certificate tell me what my diamond is worth?

No. A grading report describes the diamond's characteristics; it is not an appraisal or a valuation. Price depends on the market, not the certificate. Treat the report as a description of quality, not a price tag.

What certificate do Not Mined diamonds come with?

Every Not Mined diamond is independently certified by IGI or GIA, hand-picked at D colour, VVS+ clarity and Ideal cut, with the report number laser-inscribed on the stone. You always know exactly what you are buying. You can read more on our diamond certificate page.