What is Diamond Symmetry?
A diamond’s finish contains two major elements: Polish & Symmetry. Symmetry is the arrangement, size, and shaping of diamond's facets. The facets are the flat planes that run along the surfaces of the diamond. Symmetry is angles and lines that form the placement of the facets. Nowadays, symmetry is completely controlled by the manufacturing process. Machines very carefully cut diamonds to produce the most accurate shapes. However, at times the diamond cutter will leave a symmetry imperfection in the diamond in order to prevent a different inclusion from showing in the finished diamond. Symmetry is a subset of the diamond’s cut grade. Symmetry grades refer to how carefully and cleanly diamond facets have been cut in relation to each other. Low symmetry grades can have a negative effect on a diamond’s sparkle and its ability to hide inclusions. While symmetry is not as crucial of an element in a diamond as the cut is, it can still make a different in the visual appearance of the diamond. However, it is important to avoid diamonds that have poor symmetry as this can be detrimental to the look of the diamond. Although symmetry is not as big of decider in the visual appearance, it can make a price different of up to 15% between the varius cut grades. Therefore, it can be a good charecteristic to look at when comparing two diamonds that otherwise have the same cut grade and similiar charecteristics.Shop Diamonds
Like other diamond attributes, Symmetry is graded on a scale standardized by GIA.
Excellent: The diamond’s facets are perfectly sized and proportioned. The location of the diamond’s attributes, such as culet, girdle table, etc. are in all the perfect locations. The diamond is not out of shape. The diamond can achieve an Excellent cut grade.
Very Good: The diamond’s facet sizes and proportionately are near perfect. There may be one or two disproportionate elements that are viewed under 10px magnification. The impact on the diamond Cut grade and sparkle are minimal. The diamond can still achieve an Excellent cut grade.
Good: The size or location of attributes and facets is slightly disproportionate. The sparkle of the diamond is affected, as a result. The diamond can achieve a Very Good cut grade, at best.
Fair & Poor: The facets and proportionately are noticeably imperfect. In non-round shapes, the shaping is not perfect. The diamond’s sparkle and brilliance are impacted adversely and the diamond can achieve, at best, a Good cut grade. A diamond with poor symmetry may misdirect light that travels into the diamond, sending it off at slightly wrong angles, and thereby reducing the diamond's brilliance,
Examples of symmetry imperfections: off center culet, misshapen facets, off center table, faceting that is not properly pointed, crown and pavilion misalignment, table and girdle not parallel. More information on symmetry defects is listed below. The Symmetry grade is based on the severity of these infractions.
Types of Symmetry Defects
Out of Round
The round cut diamond is not well shaped and the ratio of length to width is greater than 1.10.
Table off Center
The table facet at the top of the diamond is not perfectly center. The light performance of the diamond may be affected.
Culet off Center
The point at the bottom of the diamond is not directly centered. Light performance may be reduced in the diamond pavilion.
Table Culet Alignment
The proportional locations of the tablet and cet are incorrect.
Crown and Pavilion Misalignment
The girdle points where the crown and pavilion facets should align are uneven. This can change the way light bounces in the diamond.
The girdle isn’t in the straight line around the diamond. This can affect the evenness of a diamond’s setting.
The skit and triangular shaped facets are uneven and the pattern is not symmetrical. This affects the amount of light that enters each diamond facet.