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 Variation |
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 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 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 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-Pointing | Ptg 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-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