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Diamond Symmetry

Diamond Symmetry – What Is It?

Diamond symmetry is the equality between corresponding parts of a stone. It is 1/2 of the category "craftsmanship" and 1/7 of the total data that decides a diamond's cut grade. Symmetry plays a huge factor on the overall brilliance of a diamond.

The symmetry of a diamond refers to the arrangement of the facets and finished angles, created by the diamond cutter. Excellent symmetry of a well-cut and well-proportioned diamond can have a great effect on the diamond’s beauty. Grading reports will often state the diamond’s symmetry in the following terms: Excellent, Very good, Good, Fair, or Poor.

It is often assumed that diamonds with poor symmetry were cut by professionals with poor skills. However just the opposite may be quite true.

When a rough diamond is being polished, the goal usually consists of creating the heaviest and most valuable diamond carat weight possible. An experienced cutter may be able to effectively perform this function by polishing a diamond with imperfect symmetry to avoid inclusions (negatively effecting the diamond clarity). It is also a fact that “key weights” (Like 1.0 carat or 2.0 carats) can be priced much higher than weights just a fraction below. (Like .99 carats or 1.99 carats)

Diamond Symmetry

The experienced diamond professional may decide to create a diamond with variations in the girdle thickness, an off-center table or culet, or a tilted table in order to achieve the “Key weight”.

The information above can be very confusing, but if you follow the chart below you’ll get a better understanding. To basically sum it all up; the more symmetrical the diamond is the more beautiful it’s diamond cut it. The more fire and ice, the more brilliance, the more sparkle. The better light passes through. When comparing GIA, or EGL, or any appraisal card check out the symmetry of the diamond and come back here and compare. It’ll make a world of difference!

The Diamond Symmetry Chart

Type: Round Brilliant Cut

Diamond Cut Grade Excellent Very Good Good Fair – Poor
Difference in Value 10 – 15% More 5 – 10% More 0% Even 10 – 20% Less
Table %  53 – 57  58 – 61  62 – 64  65+
Depth %  62.5 – 60.6  62.9 – 59.5  63.9 – 57  64+ or 56.9 & below
Polish  Excellent – Very Good  Very Good – Good  Good  Fair – Poor
Symmetry  Excellent – Very Good  Very Good – Good  Good  Fair – Poor
Culet  None – Very Small  Very Small – Small  Small – Medium  Medium – Large
Girdle  Thin – Medium  Thin – Thick  Very Thin – Thick  Extremely Thin – Very Thick

Type: Square Cuts – Princess, Radiant, Emeralds

Diamond Cut Grade Excellent Very Good Good Fair – Poor
Difference in Value 10 – 15% More 5 – 10% More 0% Even 10 – 20% Less
Table %  65 – 70  71 – 75  76 – 80  85+
Depth %  66 – 71  71 – 75  76 – 80  80+
Polish  Excellent – Very Good  Very Good – Good  Good  Fair – Poor
Symmetry  Excellent – Very Good  Very Good – Good  Good  Fair – Poor
Culet  None – Very Small  Very Small – Small  Small – Medium  Medium – Large
Girdle  Thin – Medium  Thin – Thick  Very Thin – Thick  Extremely Thin – Very Thick

Type: Elongated Cuts – Radiants, Emeralds

Diamond Cut Grade Excellent Very Good Good Fair – Poor
Difference in Value 10 – 15% More 5 – 10% More 0% Even 10 – 20% Less
Table %  65 – 69  70 – 74  75 – 80  80+
Depth %  64 – 69  63 – 71  72 – 78  79+
Polish  Excellent – Very Good  Very Good – Good  Good  Fair – Poor
Symmetry  Excellent – Very Good  Very Good – Good  Good  Fair – Poor
Girdle  Thin – Medium  Thin – Thick  Very Thin – Thick  Extremely Thin – Very Thick
Culet  None – Very Small  None – Small  Small – Medium  Medium – Large
Length / Width Ratio  1:1.35 – 1:1.42  1:1.29 – 1:1.49  1:1.20 – 1:1.60  Subjective

Type: Pear

Diamond Cut Grade Excellent Very Good Good Fair – Poor
Difference in Value 10 – 15% More 5 – 10% More 0% Even 10 – 20% Less
Table %  55 – 58  53 – 61  50 – 64  48 – 69
Depth %  59 – 63  57 – 65  55 – 68  50 – 75
Polish  Excellent – Very Good  Very Good – Good  Good  Fair – Poor
Symmetry  Excellent – Very Good  Very Good – Good  Good  Fair – Poor
Girdle  Thin – Medium  Thin – Thick  Very Thin – Thick  Extremely Thin – Very Thick
Culet  None – Very Small  None – Small  Small – Medium  Medium – Large
Length / Width Ratio  1:1.45 – 1:1.60  1:1.35 – 1:1.70  1:1.25 – 1:1.80  1:1.20 – 1:2.0+
Bow-Tie Effect  None – Minimal  Minimal – Average  Average – Significant  Significant

Type: Marquise

Diamond Cut Grade Excellent Very Good Good Fair – Poor
Difference in Value 10 – 15% More 5 – 10% More 0% Even 10 – 20% Less
Table %  55 – 58  53 – 61  50 – 64  48 – 69
Depth %  59 – 63  57 – 65  55 – 68  50 – 75
Polish  Excellent – Very Good  Very Good – Good  Good  Fair – Poor
Symmetry  Excellent – Very Good  Very Good – Good  Good  Fair – Poor
Girdle  Thin – Medium  Thin – Thick  Very Thin – Thick  Extremely Thin – Very Thick
Culet  None – Very Small  None – Small  Small – Medium  Medium – Large
Length / Width Ratio  1:1.95 – 1:2.05  1:1.8 – 1:2.2  1:1.65 – 1:2.3  1:1.5 – 1:2.4
Bow-Tie Effect  None – Minimal  Minimal – Average  Average – Significant  Significant

Type: Oval

Diamond Cut Grade Excellent Very Good Good Fair – Poor
Difference in Value 10 – 15% More 5 – 10% More 0% Even 10 – 20% Less
Table %  55 – 58  53 – 61  50 – 64  48 – 69
Depth %  59 – 63  57 – 65  55 – 68  50 – 75
Polish  Excellent – Very Good  Very Good – Good  Good  Fair – Poor
Symmetry  Excellent – Very Good  Very Good – Good  Good  Fair – Poor
Girdle  Thin – Medium  Thin – Thick  Very Thin – Thick  Extremely Thin – Very Thick
Culet  None – Very Small  None – Small  Small – Medium  Medium – Large
Length / Width Ratio  1:1.35 – 1:1.42  1:3- 1:1.5  1:1.25 – 1:1.65  1:1.15 – 1:1.9
Bow-Tie Effect  None – Minimal  Minimal – Average  Average – Significant  Significant

Please be aware that all data represented in the tables above can vary slightly. These charts are to be used for reference only, and not for exact or legal purposes.

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