How do I verify a GIA Diamond Grading Report is authentic?

Type the 10-digit report number printed top-right into GIA Report Check at gia.edu. The full report should display. Reports issued after 2006 on stones 1.00ct and larger are also laser-inscribed on the girdle with the same number — verify both before payment.

What do the red and green marks on the GIA clarity plot mean?

Red marks indicate internal inclusions — crystals, feathers, clouds. Green marks indicate surface features — naturals and extra facets. Location matters as much as grade: a VS2 with a feather reaching the girdle carries durability risk that a VS2 with a central crystal does not, and should price lower.

How does GIA fluorescence affect a diamond's price?

Strong Blue fluorescence in D–H colorless stones discounts the price 10–15% because roughly 3% appear milky or hazy in sunlight. In I–M stones, medium blue fluorescence can mask yellow and improve apparent color, and these stones often trade at a slight premium in the secondary market.

Is a GIA Excellent cut grade enough for a round brilliant?

GIA Excellent covers a wide range of proportions. For top-tier light performance, look for table 54–58%, depth 60.5–62.5%, crown angle 34–35°, pavilion angle 40.6–41.0°, and Excellent polish and symmetry. The AGS Ideal supplement, now issued through GIA, separates the best Excellents from the rest of the band.

What does "Clouds are not shown" mean on a GIA report?

It usually means a diffuse cloud inclusion contributed to the clarity grade but was too spread out to plot individually. On a VS2 or SI1 this is a warning — the stone can look milky in person and should price lower than a comparable stone with a discrete crystal inclusion.

Reading a GIA Report: 7 Lines That Move Diamond Price $1k+ in 2026

A GIA Diamond Grading Report is two pages of small print that determine the price of the stone in your hand. Most buyers look at color, clarity, and carat weight and stop there. The information that separates a fairly-priced stone from an overpriced one is in the proportions diagram and the comments section.

This article is the hub. Four companion spokes go deep on the calls that move price most often: GIA vs AGS grading scales, GIA fluorescence grades explained, GIA cut grade vs AGS 0, and reading a GIA laser inscription.

The header: report number and date

Every GIA report has a 10-digit report number, printed top-right, and laser-inscribed on the diamond's girdle (mandatory for reports issued after 2006 on stones 1.00ct and larger; optional below). Type the number into GIA's Report Check at gia.edu and the full report should display. If it does not, walk away. Counterfeit GIA reports are rare but exist, and laser inscriptions can be added to non-graded stones to mimic a real report. The step-by-step procedure for finding the inscription on a girdle and cross-checking it on Report Check lives in the reading a GIA laser inscription spoke.

The report date matters. GIA tightened its cut grading methodology in 2006 and color grading consistency in 2012. A report from 2003 is not invalid, but cut grade language differs and color may grade half a step softer if re-submitted today.

The 4Cs section

Carat weight

Reported to two decimal places, rounded down from the third decimal. A stone weighing 1.498ct is reported as 1.49ct, not 1.50ct. The 0.01ct difference matters because the per-carat price jumps at psychological thresholds (1.00, 1.50, 2.00) — the current threshold deltas by clarity grade live in our diamond price per carat in 2026 reference. Sellers sometimes label a 1.49ct stone as "essentially a 1.5" — the report is the source of truth.

Color

GIA grades D (colorless) through Z (light yellow or brown) under controlled lighting against master stones. The grades that matter at retail:

D–F: colorless. Premium pricing. Visually indistinguishable face-up in most settings.
G–J: near colorless. G and H are the value sweet spot in white gold/platinum.
K–M: faint color. Appropriate in yellow gold settings, where the metal masks warmth.

Clarity

Graded at 10x magnification by trained graders. FL and IF are flawless or internally flawless. VVS1/VVS2 inclusions are difficult for a grader to find at 10x. VS1/VS2 inclusions are visible at 10x but not to the naked eye. SI1 may be eye-clean depending on inclusion location; SI2 usually is not. I1–I3 inclusions are visible without magnification.

The clarity plot on page two shows the location and type of inclusions. Red marks are inclusions (crystals, feathers, clouds); green marks are surface features (naturals, extra facets). A VS2 with a single crystal under the table is a different stone from a VS2 with a feather reaching the girdle — the second carries a small but real durability risk and should price lower.

Cut

Only graded on round brilliants. Excellent / Very Good / Good / Fair / Poor. The grade is calculated from proportions, polish, and symmetry. "Excellent" covers a wide range — a triple-Excellent stone with shallow pavilion angles (40.6°) performs differently than one at 41.0°. For a top-tier round, you want:

Table: 54–58%
Depth: 60.5–62.5%
Crown angle: 34–35°
Pavilion angle: 40.6–41.0°
Polish and symmetry: Excellent

The wide range inside GIA Excellent is exactly why a separate light-performance grade — the old AGS scale, now living inside GIA as the AGS Ideal supplement — still matters on rounds. The full comparison and when the $25 supplement is worth pulling is in GIA cut grade vs AGS 0, and the broader scale-to-scale translation is in GIA vs AGS grading scales.

Fluorescence

None / Faint / Medium / Strong / Very Strong, with color (almost always Blue). Strong Blue fluorescence in D–H stones can cause a milky or hazy appearance in sunlight in roughly 3% of cases — visible enough that the trade discounts these stones 10–15%. In I–M stones, medium blue fluorescence can actually improve apparent color by masking yellow, and these stones often trade at a slight premium in the secondary market. The full decision tree by color band, and how to use the 10–15% discount as leverage on a clean stone, is in GIA fluorescence grades explained.

Comments and the back page

The Comments section is where treatments, additional inclusions not plotted, and clarity characteristics like "clouds not shown" or "internal graining is not shown" appear. "Clouds are not shown" on a VS2 or SI1 is a warning — it usually means a hazy cloud inclusion contributed to the grade but was too diffuse to plot. These stones can look milky in person.

What to ignore on the report

The GIA report does not assign a price — the relationship between a report's grades and a stone's real-world dollar value is unpacked in diamond value vs price. It does not certify origin, with the exception of separate origin reports for colored stones; for the per-hue pricing math on those, see our fancy color diamond value hub. And it does not guarantee future value — the secondary-market reality is in our diamond resale value reference. A report is a description of what the stone is, not a recommendation that you should buy it. Bring it to a jeweler you trust, look at the stone under daylight-balanced light, and decide from there.