How to Read a GRA or IGI Certificate

A certificate is a description written by a laboratory, not a guarantee of beauty. Two stones with identical grades can look different, because grading does not measure cut quality in the way most buyers assume.

The fields that matter

Measurements. Length × width × depth in millimeters. This is the field to use when matching a setting.
Carat weight. Rounded to two decimals. A 0.995 ct stone may be graded 1.00.
Color grade. D–Z for diamonds. D–F colorless, G–J near-colorless, K–M faint, below that visible tint.
Clarity grade. FL/IF, VVS1–2, VS1–2, SI1–2, I1–3. SI1 is usually eye-clean; SI2 sometimes is not.
Polish and symmetry. Excellent, very good, good, fair. Below "good", light return suffers.
Fluorescence. None, faint, medium, strong. Strong blue fluorescence can make a stone look milky in daylight.
Comments. Read these. They mention treatments, growth method, and "clarity characteristics" that are not plotted.

What the certificate does not tell you

It does not tell you whether the stone has a bow-tie, whether the color looks gray in daylight, or whether the cut is proportioned to return light well. Those need a video or an in-person look. A certificate with excellent grades and a bad make is still a bad stone.

GRA for moissanite

GRA cards state measurements, color and clarity for moissanite. They are issued by the supplier rather than an independent international laboratory, which is worth knowing: they are consistent within the trade, but they are not the same category of document as an IGI or GIA report.

Verifying a report

IGI and GIA reports have a report number and can be checked in the laboratory’s online database. Ask for the report number before you buy, and check it yourself — the check takes a minute and it is the only way to know the paper matches the stone.

What to ask for instead of a grade

Ask for a hand-held video in daylight, with the stone held between fingers. That single request eliminates most of the risk in buying a fancy-shape stone remotely.