Diamond Symmetry

Symmetry is graded on a scale from Excellent to Poor based on the presence and visibility of symmetry deviations at 10x magnification. The following features are considered in the symmetry assessment.

Symmetry Feature Abbreviation Definition Example
Crown Angle Variation CV Unequal crown angles
Crown Height Variation CHV Girdle plane not parallel to the table causing uneven crown height
Culet Off-Center C/oc Deviation of the culet from the central position on the pavilion
Extra Facet EF Additional facet placed without regard for symmetry and not required by the cutting style
Girdle Thickness Variation GTV Variation of the girdle thickness at the bezel-main positions
Lower Half Percentage
LPV Variation of lower half facet length percentages
Lower Half Variation LHV Unequal lower half facet angles
Misalignment Aln Displacement of the crown and pavilion facets in relation to each other
Misshapen Facet Fac
Difference in shape or size between one facet and another of the same type, or distortion of a given facet; bezel, star and main facets that are misshapen are listed more specifically as misshapen bezel (MB), misshapen star (MS) and misshapen main (MM)
Missing Facet MF Asymmetrically missing facet
Natural N Part of the original rough diamond’s surface that remains on the polished diamond
Non-Octagonal Table T/oct
The table of a Round Brilliant is not a regular octagon, showing differences among the four table sizes (T/oct) or among the eight table edges (TEV)
Non-Pointing Ptg
Fully formed facet that does not reach its prescribed location (short facet) or is incompletely finished (open facet), resulting in adjoining facets not meeting at precise points; non-pointing of bezel and main facets are listed more specifically as short main (SM), short bezel (SB), open main (OM) and open bezel (OB)
Out-of-Round OR Deviation from the circular shape of a round diamond
Pavilion Depth Variation PDV Variation of pavilion depth
Pavilion Angle Variation PV Unequal pavilion angles
Star Percentage Variation SPV Variation of star facet length percentages
Star Angle Variation SV Unequal star facet angles
Table Off-Center T/oc Deviation of the table from the central position on the crown
Table/Culet Alignment T/C Displacement of the table facet and culet in different directions
Upper Half Variation UHV Unequal upper half facet angles
Uneven Outline UO Asymmetrical shape outline; also refers to bumps and flattened areas created by a natural, extra facet or uneven girdle faceting on round diamonds

This information is courtesy of GIA