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 FeatureAbbreviationDefinitionExample
Crown Angle VariationCVUnequal crown angles
Crown Height VariationCHVGirdle plane not parallel to the table causing uneven crown height
Culet Off-CenterC/ocDeviation of the culet from the central position on the pavilion
Extra FacetEFAdditional facet placed without regard for symmetry and not required by the cutting style
Girdle Thickness VariationGTVVariation of the girdle thickness at the bezel-main positions
Lower Half Percentage
Variation
LPVVariation of lower half facet length percentages
Lower Half VariationLHVUnequal lower half facet angles
MisalignmentAlnDisplacement of the crown and pavilion facets in relation to each other
Misshapen FacetFac
MB
MS
MM
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 FacetMFAsymmetrically missing facet
NaturalNPart of the original rough diamond’s surface that remains on the polished diamond
Non-Octagonal TableT/oct
TEV
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-PointingPtg
SM
SB
OM
OB
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-RoundORDeviation from the circular shape of a round diamond
Pavilion Depth VariationPDVVariation of pavilion depth
Pavilion Angle VariationPVUnequal pavilion angles
Star Percentage VariationSPVVariation of star facet length percentages
Star Angle VariationSVUnequal star facet angles
Table Off-CenterT/ocDeviation of the table from the central position on the crown
Table/Culet AlignmentT/CDisplacement of the table facet and culet in different directions
Upper Half VariationUHVUnequal upper half facet angles
Uneven OutlineUOAsymmetrical 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