Lab Grown Diamond Symmetry and Polish: How They Impact Beauty
When evaluating a lab grown diamond, most buyers focus on the 4Cs — cut, color, clarity, and carat weight. But within the cut grade, two sub-categories deserve special attention: symmetry and polish. These factors directly influence how your diamond handles light and, consequently, how beautiful it appears.
What Is Diamond Symmetry?
Symmetry refers to how precisely the diamond's facets align with each other. A perfectly symmetrical diamond has facets that mirror each other exactly across corresponding points, creating balanced light performance from every angle.
What Graders Evaluate
When a gemological lab like IGI or GIA grades symmetry, they examine:
- Facet alignment — do corresponding facets on opposite sides match in size, shape, and angle?
- Table centering — is the flat top facet centered on the crown?
- Culet position — is the bottom point centered directly below the table?
- Crown/pavilion alignment — do the upper and lower halves align properly?
- Girdle uniformity — is the edge (girdle) consistent in thickness around the stone?
- Facet pointing — do facet edges meet at precise points rather than leaving small gaps?
Symmetry Grades
| Grade | Meaning | Recommendation |
|---|---|---|
| Excellent (EX) | No symmetry deviations visible under 10x magnification | Ideal — maximum light performance |
| Very Good (VG) | Minor deviations visible under 10x, invisible to naked eye | Excellent value — visually indistinguishable from EX |
| Good (G) | Some deviations that may subtly affect light performance | Acceptable for investment-conscious buyers |
| Fair (F) | Noticeable deviations that affect light return | Not recommended |
| Poor (P) | Obvious deviations, significantly reduced beauty | Avoid |
What Is Diamond Polish?
Polish refers to the smoothness of each facet's surface after the diamond has been cut and polished. Think of polish as the "finish" on the diamond — just as a car's paint can be mirror-smooth or slightly textured, a diamond's facet surfaces can be perfectly smooth or carry tiny imperfections from the polishing process.
Polish Features
Common polish characteristics that affect grading:
- Burn marks — hazy areas from excessive heat during polishing
- Polish lines — fine lines left by the polishing wheel
- Scratches — surface scratches from the polishing process
- Abrasion — tiny nicks along facet junctions
- Lizard skin — bumpy surface texture on certain facets
- Pit — a tiny opening on a facet surface
Polish Grades
| Grade | Meaning | Recommendation |
|---|---|---|
| Excellent (EX) | No polish features visible under 10x magnification | Ideal — pristine surface quality |
| Very Good (VG) | Minor features visible under 10x, invisible to naked eye | Excellent choice — no visible difference from EX |
| Good (G) | Features visible under 10x, usually invisible to naked eye | Good value option |
| Fair (F) | Features visible to naked eye in certain lighting | Not recommended for fine jewelry |
| Poor (P) | Obvious features affecting appearance | Avoid |
How Symmetry and Polish Affect Light Performance
Symmetry's Role
Symmetry directly affects the three components of diamond beauty:
- Brilliance — misaligned facets send light in unintended directions, reducing the white light that returns to your eye
- Fire — asymmetric facets disperse light unevenly, creating inconsistent rainbow flashes
- Scintillation — the sparkle pattern appears unbalanced when facets don't correspond properly
Polish's Role
Polish affects light at the surface level:
- A perfectly polished facet acts like a tiny mirror — reflecting and refracting light with maximum efficiency
- Surface imperfections scatter light before it enters or exits the diamond, slightly dulling overall brilliance
- The effect is cumulative — a diamond has 57-58 facets, so polish quality across all surfaces matters
Lab Grown Diamond Advantage
Lab grown diamonds have an inherent advantage in achieving excellent symmetry and polish. The controlled growth conditions produce crystals with fewer internal stresses and more consistent hardness, making precision cutting and polishing easier. As a result, a higher percentage of lab grown diamonds achieve Excellent ratings in both categories compared to mined stones.
Practical Buying Recommendations
The Sweet Spot
For the best value-to-beauty ratio:
- Aim for EX/EX or EX/VG in symmetry/polish for round brilliants
- VG/VG is excellent value — the visual difference from EX/EX is imperceptible to the naked eye
- For fancy shapes (oval, cushion, pear), VG/VG is standard and perfectly beautiful
When to Prioritize Excellent
- Solitaire engagement rings where the single diamond is the entire focus
- Larger diamonds (2ct+) where any imperfections become more noticeable
- When paired with a prong setting that exposes maximum surface area
When VG/VG Is More Than Enough
- Smaller accent diamonds in pavé settings
- Diamonds under 0.50ct where differences are invisible
- Stud earrings and pendants viewed from conversational distance
Reading Your Certificate
On your lab grown diamond certificate, symmetry and polish are listed as separate line items under the cut quality section. Look for:
- The symmetry grade (EX, VG, G, F, P)
- The polish grade (EX, VG, G, F, P)
- Some certificates list specific symmetry/polish features noted during grading
Both symmetry and polish contribute to the overall cut grade, but they're evaluated independently. A diamond can have Excellent symmetry but only Good polish, or vice versa.
Recommended Pieces
- 14K White Gold 3 3/8Ct Round/Ruby Round Ladies
- Ladies Ring 1 1/2Ct Round 14K Yellow Gold
- Ladies Solitaire Ring 2Ct Oval 14K White Gold
Browse our certified lab grown diamond collection — every piece features diamonds selected for exceptional cut quality, symmetry, and polish.
