Diamond certification & grading guide

Lab-grown diamonds can receive independent grading reports, but they are not always graded in the same way as natural diamonds. Since October 2025, GIA has assessed eligible LGDs as “Premium” or “Standard”, rather than using the detailed color and clarity grades applied to natural diamonds. Other laboratories use different systems, so buyers should check who issued the report and what it covers¹.

How does diamond grading differ for natural and lab-grown diamonds?

Close Up Of A Rough Natural Diamond Image Library Image 2

Grading approach

Independent labs grade natural diamonds against detailed quality criteria, including the 4Cs.

Grading approach

Grading detail varies by lab. GIA now limits eligible lab-grown diamonds to a broader Premium or Standard rating rather than full 4Cs grading*.

Color and clarity

Each diamond receives its own individual color grade and its own clarity grade.

Color and clarity

Placed into one broader category rather than separate grades at labs that follow GIA’s approach.

Minimum grading threshold

Every submitted diamond receives a grade, regardless of quality.

Minimum grading threshold

At GIA specifically, a diamond only receives a rating if it meets a minimum quality baseline first*.

Report identification

Identified as natural

Report identification

Identified as laboratory-grown

*GIA’s system for eligible lab-grown diamonds since October 2025².

How are diamonds certified?

Diamond grading is an independent assessment by a gemological laboratory. A grading report records a diamond’s characteristics and can confirm whether it is natural or a laboratory-grown diamond (LGD)³.

How are natural diamonds certified?

Natural diamonds are assessed by gemologists using specialist equipment. Laboratories such as GIA and IGI grade characteristics including the 4Cs of diamonds (opens in a new window) and issue an independent grading report⁴.

gemologists using specialist equipment to assess a natural diamond

How are lab-grown diamonds certified?

LGDs can receive independent grading reports, but the assessment depends on the laboratory. GIA now places eligible LGDs into Premium or Standard categories rather than applying the detailed color and clarity grades used for natural diamonds (opens in a new window)⁵.

Which diamond grading laboratories are most recognized?

GIA and IGI are two widely recognized laboratories that independently assess diamonds⁶.

a GIA certificate next to a natural diamond

GIA grading reports

GIA continues to grade natural diamonds using the detailed 4Cs system. Eligible LGDs receive the broader Premium or Standard assessment.

IGI grading reports

IGI issues reports for both natural and lab-grown diamonds, identifying how each diamond was formed⁷.

What information is included in a diamond grading report?

Depending on the laboratory and report, information can include carat weight, measurements, cut, color, clarity, polish, symmetry, fluorescence and treatments⁸.

Origin and growth method disclosure

A grading report can identify whether a diamond is natural or laboratory-grown. Lab-grown reports may also identify the growth method and treatments⁹.

Why does diamond certification matter?

An independent grading report gives buyers verified information about a diamond’s identity and quality, making it easier to understand and compare diamonds before buying¹⁰.

A grading report is also essential when selling natural diamonds, not only does it provide the buyer with verification on the quality of the diamond, it will help qualify its resale value and justify buying decisions. Certified diamonds are easier to market for this reason and are valued higher than diamonds with no certification.

FAQs

How are natural diamonds certified?

Natural diamonds are assessed by independent gemological laboratories to confirm that they are a real diamond (opens in a new window) formed naturally and to grade characteristics such as the 4Cs.

How reliable is diamond certification?

Reports from recognized independent laboratories provide an expert assessment of a diamond’s characteristics and identity. Testing can distinguish natural diamond formation (opens in a new window) from laboratory growth.

How is diamond clarity graded?

Diamond clarity (opens in a new window) assesses inclusions and blemishes. Our diamond clarity guide (opens in a new window) explains the grades and what they mean when choosing a natural diamond.

How is diamond color graded?

Diamond color (opens in a new window) is graded according to how much color a diamond displays, with GIA’s natural diamond scale running from D to Z.

What is a lab-grown diamond?

If you’re wondering what a lab-grown diamond is (opens in a new window), it is a diamond created using HPHT or CVD technology rather than formed naturally within the Earth.