Reports · Chapter 05

GIA, IGI, and the laboratory landscape

How the major report issuers differ—and how to compare the document in front of you without relying on reputation alone.

The laboratory name matters because it tells you whose standards, instruments, terminology, and report format produced the grades. It is a starting point for interpretation, not a substitute for reading the report itself.

Begin with scope, not a league table

GIA, IGI, GCAL, HRD Antwerp, and other established laboratories offer different report families, services, and cut systems. Ask what kind of stone the report covers, which observations it includes, and which grading framework applies. A familiar logo does not make every document identical, and a less familiar format is not automatically weak.

GIA’s laboratory-grown service changed in 2025

GIA developed the modern four Cs framework and continues to issue grading reports for natural diamonds. Beginning October 1, 2025, it stopped using the natural-diamond color and clarity nomenclature for D-to-Z laboratory-grown submissions. Its replacement Laboratory-Grown Diamond Quality Assessment classifies eligible stones as Premium or Standard; stones below the Standard thresholds do not receive the assessment. Older GIA laboratory-grown reports with familiar color and clarity grades remain part of the record and can still be verified, so the report date and service name matter.

Worth remembering: It is more precise to say GIA changed how it evaluates laboratory-grown diamonds—not that it stopped examining them.

IGI is common in the laboratory-grown market

IGI issues natural and laboratory-grown diamond reports across a large international network. Its reports commonly identify origin and may state growth method, post-growth treatment, proportions, finish, inscription, and—for eligible stones—an overall cut grade. Read those fields directly rather than treating “IGI” as shorthand for one fixed product.

GCAL and HRD add different context

GCAL reports may emphasize documented optical-performance information and offer services with their own assurance language. HRD Antwerp issues diamond reports within a European market tradition and uses its own formats and grading procedures. For either, confirm the specific report type, current terms, and which measurements or images are actually included.

Older AGS documents still appear

American Gem Society Laboratories was especially associated with cut-quality analysis. Buyers may still encounter valid legacy AGS reports; GIA now also offers an AGS Ideal supplemental report for eligible diamonds. Verify an older document through the appropriate official record and read its date and scope in context.

Cut-grade words are not one shared scale

Each laboratory names its cut grades on its own scale. For round brilliants, GIA’s highest cut grade is Excellent; GIA does not issue an “Ideal” cut grade. IGI’s scale places Ideal above Excellent, followed by Very Good, Good, and Fair or Poor—so an IGI Excellent is that laboratory’s second tier. AGS reports used Ideal, expressed numerically as 0, as the top of their cut scale, and HRD Antwerp uses Excellent as its highest cut grade. The same word can therefore sit in a different position depending on who issued the report.

Worth remembering: Read a cut grade on the scale of the laboratory that issued it, not as a universal ranking.

Fancy shapes usually carry no overall cut grade

GIA does not assign an overall cut grade to fancy shapes such as ovals, emeralds, pears, marquises, cushions, and radiants; those reports grade polish and symmetry instead. Most IGI fancy-shape reports likewise omit an overall cut grade. When a listing describes an “Excellent cut oval,” the label usually comes from the seller rather than the laboratory. For fancy shapes, measurements, length-to-width ratio, and exact-stone imagery carry the cut information that a single grade cannot.

Color and clarity share most of their vocabulary, not a single standard

Most laboratories use the D-to-Z color letters and a clarity scale close to the familiar Flawless-to-Included terms, but the wording is not identical everywhere: HRD Antwerp, for example, calls its top clarity grade Loupe Clean (LC) and uses P1 to P3 where GIA uses I1 to I3. Each laboratory, however, applies its own standards and procedures, and many in the trade perceive differences in how strictly different laboratories grade. Where you can, compare stones graded by the same laboratory, and always verify the report on that laboratory’s own website before relying on it.

Check the report, not the listing

Retail listings sometimes show grades that do not appear on the laboratory report—an “Ideal” cut on a GIA round brilliant, for example, or a cut grade on a fancy shape whose report has none. Listing text can be abbreviated, merged from supplier feeds, or written as marketing. Open the report itself, match the report number and measurements, and treat any grade that is not printed there as the seller’s description.

How The Carat Standard reads grades across laboratories

We read each grade on the issuing laboratory’s own scale and show it exactly as that laboratory issued it. We do not translate one laboratory’s grade into another’s terms or supply a cut grade the report does not contain. When we assess cut, we look to the measured proportions recorded on the report rather than to the cut label alone.

Compare facts before comparing labels

When two stones carry reports from different laboratories, line up origin, report type, measurements, carat, color, clarity, finish, fluorescence, comments, and proportions. Similar grade words should not be assumed to represent identical procedures or tolerances. Then use exact-stone imagery and seller terms to answer the questions no laboratory report can settle.

Worth remembering: The most useful report is authentic, appropriate to the stone, complete enough for the decision, and verified at its issuing laboratory.

Essential language

Issuing laboratory: The organization that examined the stone and produced the grading or identification report.
Report type: The laboratory’s named service, which determines the scope and fields included.
Cut system: A laboratory’s method for assessing proportions, finish, and other factors related to cut quality.
Supplemental report: An additional document that evaluates a narrower subject alongside a primary report.
Legacy report: A valid older document issued under a laboratory service or system that has since changed.
Grading scale: The ordered set of grades a particular laboratory uses; the same word may hold a different position on another laboratory’s scale.

Questions to take with you

What exact report type and issue date am I reading?
Is this cut grade printed on the laboratory report, or added by the seller?
Where does this grade sit on the issuing laboratory’s own scale?
Can I verify every field through the issuing laboratory’s official report-check service?
Does this laboratory provide an overall cut grade for this particular shape and report type?
Which useful facts or images are absent from this format?
Am I comparing the actual measurements and comments—not only matching grade labels?