Introduction
When you purchase a diamond above 1.00 ct, the document most likely accompanying it is a GIA Diamond Grading Report. This is GIA's most detailed report type — a single-page record containing everything the laboratory observed and measured during its examination. No other GIA document provides as much information about an individual stone.
The Diamond Grading Report is issued for diamonds of 0.15 ct and above, though in practice it is the standard for stones at the 1.00 ct threshold and higher, where the value justifies the more comprehensive assessment. Smaller diamonds more commonly receive the GIA Diamond Dossier, a compact alternative that omits the clarity plot.
This article walks through the report's layout section by section, explains what each part tells you, and points to detailed guides where you can learn to read each section in depth. For a broader overview of what any grading report contains — not just GIA's — see What a Report Contains. For background on GIA as an institution, see GIA Profile.
Key Points
Report Header
The top of the report establishes identity. It includes the GIA logo, the report title ("GIA Diamond Grading Report"), and the date of examination. The date matters: grades reflect the diamond's condition at that moment. If the stone has been re-polished, chipped, or altered since the examination date, the grades may no longer apply.
The report number appears prominently in the header. This number is unique to the diamond and links it to GIA's permanent database. On most diamonds graded with the full report, the same number is laser-inscribed on the girdle, creating a physical connection between stone and document. See Report Number & Inscription for how to locate and verify the inscription.
Shape and Cutting Style
Directly below the header, the report identifies the diamond's shape and cutting style — for example, "Round Brilliant" or "Oval Modified Brilliant." This classification determines which grading criteria apply. GIA assigns a formal cut grade only to standard round brilliants; fancy shapes receive proportions data and finish grades but no overall cut grade. See Shape & Cutting Style on the Report for details.
Measurements
The report records the diamond's dimensions in millimetres. For round brilliants, this appears as minimum diameter – maximum diameter × depth (e.g., 6.51 – 6.55 × 4.03 mm). For fancy shapes, the format is length × width × depth.
These numbers tell you the diamond's physical size — something carat weight alone does not reveal. Two 1.00 ct diamonds can differ by half a millimetre in spread depending on how they are cut. See Measurements on the Report for how to interpret this section.
The 4Cs Grades
The central section presents the grades that drive pricing and comparison:
- Carat Weight — recorded to the hundredth of a carat (e.g., 1.52 ct), measured on calibrated scales
- Colour Grade — on GIA's D-to-Z scale, determined by comparison against master stones under controlled lighting. See Normal Colour Range
- Clarity Grade — on the FL-to-I3 scale, assessed at 10× magnification. See GIA Clarity Scale
- Cut Grade — for round brilliants only, graded from Excellent to Poor based on proportions, light performance, and craftsmanship. See Cut Grade Scale
For a detailed explanation of how to read this panel, see 4Cs Panel on the Report.
Finish Grades
Below the 4Cs, the report assesses the diamond's finish in two components:
- Polish — the smoothness and quality of facet surfaces, graded Excellent to Poor
- Symmetry — the precision of facet alignment and intersection, also Excellent to Poor
These grades affect how cleanly the diamond handles light. A stone with Excellent proportions but Poor symmetry will not perform to its potential. See Finish on the Report for what each grade means in practice.
Fluorescence
The report records the diamond's reaction to long-wave ultraviolet light, graded from None to Very Strong. When fluorescence is present, the colour is also noted — most commonly blue.
Fluorescence is neither a defect nor a bonus. Its effect depends on the specific stone: in some diamonds it enhances apparent colour; in others, strong fluorescence can produce a milky or hazy appearance. The report gives you the grade; evaluating its visual impact requires seeing the diamond in person. See Fluorescence on the Report for context.
Clarity Plot
The clarity plot is what distinguishes the full Diamond Grading Report from the Dossier. It is a schematic diagram — a map of the diamond — showing the location, size, and type of every inclusion and blemish the gemologist observed. Red symbols indicate internal characteristics (inclusions); green symbols indicate external characteristics (blemishes).
This section rewards careful reading. The clarity grade tells you a diamond is VS2; the plot tells you whether that VS2 inclusion sits directly under the table — visible face-up — or near the girdle, where a prong setting would conceal it entirely. Two VS2 diamonds can look very different depending on inclusion placement. See Clarity Plot on the Report for how to interpret the symbols.
Proportions Diagram
The proportions diagram presents a cross-section of the diamond with exact measurements:
- Table percentage — the width of the table facet relative to the average girdle diameter
- Crown angle — the angle from the crown main facets to the girdle plane
- Pavilion angle — the angle from the pavilion main facets to the girdle plane
- Total depth percentage — the diamond's height relative to its width
- Star length, lower half length — additional facet proportions
- Girdle thickness — described as a range (e.g., "Thin to Medium")
- Culet size — typically "None" (pointed) in modern cuts
Crown angle and pavilion angle together determine how efficiently a diamond returns light to the viewer. The proportions diagram gives you the raw data to assess this. See Proportions Diagram on the Report for how to read it.
Comments
The comments section contains additional observations that do not fit into the structured fields above. Common entries include notes about laser inscription, minor polish details not shown on the plot, and — critically — disclosures about treatments or transparency concerns.
Pay particular attention to the comment "Additional clouds are not shown." This indicates cloud inclusions beyond those plotted, which may affect the diamond's transparency in ways the clarity grade alone does not communicate. See Comments on the Report for a guide to common entries and what they mean.
Security Features
GIA reports include multiple anti-counterfeiting measures:
- Hologram — a GIA-branded holographic element embedded in the report
- Microprint line — a fine line of text, visible under magnification, that cannot be accurately reproduced by standard printers or scanners
- Unique report number — linked to GIA's online database for independent verification
- QR code — on newer reports, providing direct access to the digital record
These features protect against forged or altered reports. Always verify a report online through GIA's Report Check service before relying on it for a purchase decision. See Online Report Verification for step-by-step instructions.
Summary
The GIA Diamond Grading Report is the most complete grading document available for a diamond. It combines the 4Cs grades with a clarity plot, proportions diagram, finish and fluorescence assessments, precise measurements, and a comments section — giving you a full technical profile of the stone in a single page. For diamonds of 1.00 ct and above, this report is the market standard and the document Czech consumers should expect when making a significant diamond purchase. Use it as your starting point: read each section, cross-reference with the detailed how-to-read guides linked above, and then evaluate the diamond with your own eyes. The report tells you what the laboratory found. What the diamond means to you is a separate question — and that one, only you can answer.