The gemology
The language of a diamond report, in plain terms. These are the words you will meet on a DGI certificate and across the trade.
Carat ct
A diamond’s weight. One carat equals 0.2 grams, divided into 100 points.
Colour D–Z
How colourless a stone is, graded from D (icy white) down to Z (light yellow or brown).
Clarity FL–I3
The absence of internal inclusions and surface blemishes, from Flawless to Included.
Cut
How precisely a stone is faceted and proportioned — the craft that governs how it returns light.
Table
The large flat facet on the top of the stone, expressed as a percentage of its width.
Crown
The upper portion of the diamond, above the girdle.
Girdle
The thin band around the widest part of the stone, where crown meets pavilion.
Pavilion
The lower cone of the diamond, below the girdle, that reflects light back to the eye.
Culet
The tiny facet (or point) at the very bottom of the pavilion.
Depth
The stone’s height from table to culet, given as a percentage of its width.
Inclusion
A natural internal characteristic — a crystal, feather or cloud — used to grade clarity.
Brilliance
The white light a diamond reflects back to the viewer.
Fire
The flashes of rainbow colour produced as light disperses within the stone.
Scintillation
The sparkle and play of light and dark as the diamond or the light moves.
Polish
The smoothness of the finished facet surfaces, graded from Excellent to Poor.
Symmetry
How precisely the facets align and meet — a measure of cutting accuracy.
Fluorescence
A glow some diamonds emit under ultraviolet light, most often blue.
Hearts & Arrows
A pattern of optical symmetry seen in superbly cut round brilliants.
Dia-Script
A laser inscription on the girdle — the report number, logo or a personal message.
Diamond Seal
A tamper-evident capsule that seals a graded stone to its certificate.
Rapaport
The industry price list widely used as a benchmark for diamond values.
Lab-grown
A genuine diamond grown in a laboratory by HPHT or CVD, identical in properties to a mined one.
Report No.
The unique number that ties a stone to its record in the DGI registry.
Appraisal
An estimated replacement value, based on the current Rapaport list — not an official valuation.
Read your
These terms come together on every DGI report. See how they are laid out, and how to verify a certificate is authentic.