GIA Diamond Grading Report
GIA Diamond Grading Report
The industry-standard document for polished diamond assessment
The GIA Diamond Grading Report is a comprehensive laboratory document issued by the Gemological Institute of America (GIA) that provides a full, independent assessment of a polished diamond's quality characteristics. Widely regarded as the most authoritative and consistently applied diamond grading document in the world, it underpins pricing, insurance valuation, estate appraisal, and consumer confidence across every major market. The report is not a valuation — it contains no monetary figure — but its grades are the primary reference against which market prices are negotiated globally.
What the Report Covers
The Diamond Grading Report evaluates a diamond against the framework of the four principal quality factors — carat weight, colour, clarity, and cut — commonly referred to in the trade as the 4Cs, a terminology GIA itself introduced and standardised in the mid-twentieth century.
- Carat weight is recorded to the nearest hundredth of a carat.
- Colour grade is assigned on GIA's D-to-Z scale, where D represents colourlessness and Z the lower boundary of the near-colourless-to-light-yellow or light-brown range. Grades are determined by comparison with a master set of reference diamonds under controlled lighting conditions.
- Clarity grade is assigned on a scale running from Flawless (FL) through Internally Flawless (IF), Very Very Slightly Included (VVS1–VVS2), Very Slightly Included (VS1–VS2), Slightly Included (SI1–SI2), and Included (I1–I3). A plotted diagram — a schematic map of the diamond's crown and pavilion — records the position, nature, and relative size of clarity characteristics using standardised symbols.
- Cut grade (Excellent, Very Good, Good, Fair, Poor) is provided for standard round brilliant diamonds, assessing the interaction of proportions, symmetry, and polish in producing the stone's face-up appearance, brilliance, fire, and scintillation. Cut grading is not currently applied to fancy shapes on this report.
- Polish and symmetry are each graded separately on the same five-point scale.
- Fluorescence is described by intensity (None, Faint, Medium, Strong, Very Strong) and colour (most commonly blue).
- Measurements give minimum and maximum diameter (for round stones) or length-by-width dimensions (for fancy shapes), along with depth, expressed in millimetres.
Eligibility and Issuance
GIA issues the full Diamond Grading Report primarily for polished diamonds of approximately 1.00 carat and above, though the laboratory will examine smaller stones upon request. For diamonds below that threshold, GIA offers the Diamond Dossier, a more compact document that omits the plotted clarity diagram but includes a laser-inscribed report number and all principal grades. Both documents carry equal authority with respect to the grades themselves.
Laser Inscription and Verification
A unique report number is laser-inscribed on the diamond's girdle, providing a direct, permanent link between the physical stone and its documentation. This inscription can be read under magnification and verified against GIA's online report-check database at gia.edu/report-check, allowing any party in the supply chain — dealer, retailer, insurer, or end consumer — to confirm the authenticity of the report and review its grades independently.
Market Significance
Because GIA operates as a non-profit educational institution with no commercial interest in the sale of diamonds, its reports are perceived as free from the grade inflation that has occasionally been observed in documents issued by certain other laboratories. The Rapaport Diamond Report, the principal wholesale price benchmark for the trade, is calibrated explicitly to GIA colour and clarity grades, meaning that a stone accompanied by a GIA Diamond Grading Report can be priced with a precision and transparency that documents from less consistently graded laboratories cannot replicate. Major auction houses including Christie's, Sotheby's, and Bonhams routinely reference GIA grades in catalogue descriptions of significant diamonds, and many tender processes in the rough and polished diamond trade specify GIA grading as a condition of participation.
Limitations
The report grades the diamond as submitted; it does not detect all treatments with equal sensitivity across every submission, and GIA recommends that stones suspected of treatment be submitted with that disclosure. The report also does not assign a monetary value, and grades alone do not capture every factor relevant to a diamond's market price — including the precise nature and position of inclusions within a clarity grade, the face-up colour appearance of a near-colourless stone, or the qualitative character of a particular cut execution. Experienced buyers and gemmologists use the report as a foundation, not a ceiling, for their assessment.