When you hold a diamond up to the light and watch it erupt into a kaleidoscope of brilliance, you're witnessing the result of far more than just good luck. That breathtaking sparkle is the product of precise craftsmanship, scientific cutting, and two grading factors that most shoppers overlook entirely: polish and symmetry. Understanding what diamond polish and symmetry mean - and why they matter for lab-grown stones - can be the difference between a diamond that dazzles for a lifetime and one that quietly underperforms.
At 6ix of Diamonds, we believe that an informed buyer is a confident buyer. Whether you're shopping for an engagement ring collection in Toronto or selecting a stunning piece of fine jewelry as a gift, knowing how to read a diamond's quality beyond the traditional 4Cs gives you a meaningful edge. And when it comes to lab-grown diamonds - which offer the same physical, chemical, and optical properties as mined diamonds at 60-80% less cost - these finer grading details become especially important to understand.
So let's break it down. No jargon, no confusion - just clear, expert guidance to help you choose a stone that truly shines.
What Is Diamond Polish?
Diamond polish refers to the overall smoothness and condition of a diamond's surface after it has been cut and finished. During the cutting process, a diamond cutter uses a spinning wheel coated with diamond dust to shape and refine each facet. Polish is the grade assigned to how well that finishing work was executed.
The Gemological Institute of America (GIA) and the International Gemological Institute (IGI) - the two most trusted certification bodies for both mined and lab-grown diamonds - grade polish on the following scale:
- Excellent - Virtually no polish blemishes visible under 10x magnification
- Very Good - Minor imperfections detectable only by a trained gemologist
- Good - Some surface characteristics visible under magnification
- Fair - Noticeable polish features that may affect brilliance
- Poor - Heavy polish flaws that visibly diminish the diamond's appearance
Why Polish Affects Brilliance
Think of polish like the lens of a camera. A perfectly clean, smooth lens transmits light with maximum clarity. A smudged or scratched lens scatters and distorts that light. The same principle applies to a diamond's facets. Poor polish means light entering the stone encounters micro-abrasions and surface irregularities that reduce the diamond's ability to reflect and refract light with maximum efficiency. The result? A stone that looks slightly dull or milky rather than brilliantly alive.
For engagement rings, where the centre stone is meant to command attention, polish grade is particularly critical. We always recommend selecting a diamond graded Excellent or Very Good in polish for any stone that will be prominently displayed.
What Is Diamond Symmetry?
While polish describes the surface of each individual facet, symmetry describes how well all the facets are aligned, shaped, and positioned relative to one another. A diamond with poor symmetry may have facets that are misaligned, off-centre, or uneven in size - even if the stone looks acceptable at a glance.
IGI and GIA grade symmetry using the same five-point scale as polish: Excellent, Very Good, Good, Fair, and Poor.
Common Symmetry Issues to Know
Some of the most frequent symmetry flaws gemologists identify include:
- Off-centre culet - The bottom point of the diamond isn't perfectly centred
- Wavy girdle - The middle band of the diamond undulates instead of sitting level
- Misshapen facets - Individual facets vary in size or shape when they should match
- Table off-centre - The large flat top facet isn't properly centred on the stone
- Extra facets - Additional small facets added to hide inclusions, disrupting the pattern
Each of these imperfections can interfere with the precise optical engineering that makes a well-cut diamond so mesmerizing. Light entering one facet is meant to bounce at exact angles to exit through the top of the stone in a controlled, brilliant pattern. When symmetry is compromised, that light leaks out the sides or bottom instead - reducing sparkle and visual impact.
Why These Grades Matter Especially for Lab-Grown Diamonds
This is where the conversation gets particularly relevant for modern diamond shoppers. Understanding what diamond polish and symmetry mean for lab-grown stones is essential because of how the market has evolved.
Lab-grown diamonds are created using two primary methods: High Pressure High Temperature (HPHT) and Chemical Vapor Deposition (CVD). Both methods produce rough diamonds that then must be cut and polished by skilled craftspeople - exactly like mined diamonds. The cutting process is identical, the grading standards are identical, and the optical performance potential is identical.
However, because lab-grown diamonds are significantly more affordable - often 60-80% less than their mined counterparts - buyers sometimes assume they need to make compromises elsewhere. That's a misconception worth correcting. With the savings you gain from choosing a lab-grown diamond, you can absolutely afford to select a stone with Excellent grades in both polish and symmetry without stretching your budget.
IGI and GIA Certification: Your Quality Guarantee
At 6ix of Diamonds, every lab-grown diamond we carry comes with certification from either the GIA or IGI. These certificates provide a comprehensive report that includes the stone's grades for cut, colour, clarity, carat weight - and critically, polish and symmetry.
When you visit our Toronto showroom or browse our collection online, you'll always be able to view the grading report for any diamond you're considering. We strongly advise never purchasing a diamond without a certificate from one of these two institutions. An uncertified diamond leaves you with no independent verification of what you're actually buying.
How to Use Polish and Symmetry Grades When Shopping
Now for the practical part - how do you actually use this information when choosing a diamond?
The Triple Excellent Standard
In the diamond industry, the most coveted cutting designation is often referred to as Triple Excellent (3EX) - meaning a diamond receives Excellent grades for Cut, Polish, and Symmetry. For round brilliant diamonds, this is the gold standard, and it's widely available in lab-grown stones.
For fancy shapes - ovals, cushions, pears, emeralds, and marquise cuts - GIA and IGI don't assign an overall cut grade the same way they do for rounds. This makes polish and symmetry grades even more important for fancy shapes, as they become primary indicators of cutting quality.
Prioritizing Your Grades
If budget requires any trade-off (which is far less common with lab-grown stones), here's a helpful priority framework:
- Never go below Very Good in either polish or symmetry for a centre stone
- Aim for Excellent/Excellent for round brilliants - the optical precision matters most here
- For fancy shapes, prioritize symmetry slightly over polish, as facial symmetry is what most affects visual appeal in elongated cuts
- For side stones in pavé or halo settings, Good grades are generally acceptable since those stones are small and set closely together
If you're designing a bespoke design service piece, our team can walk you through exactly which grades make sense for your chosen setting and stone shape. Consider building your own ring to select every detail with confidence.
Real-World Impact: Can You See the Difference?
A fair question - and the honest answer is nuanced. The difference between Excellent and Very Good polish or symmetry is generally not visible to the naked eye. However, the difference between Excellent and Good - or worse, Fair - can sometimes be detected, especially in certain lighting conditions.
More importantly, when you're comparing two diamonds of the same colour, clarity, and carat weight side by side, the one with superior polish and symmetry will consistently look brighter and more lively. It's a subtle but real advantage that compounds over a lifetime of wearing.
This matters particularly for pieces that are meant to be showcased prominently. Whether you're selecting [diamond earrings](/category/diamond earrings) that frame your face or a stunning [diamond necklace](/category/diamond necklaces) that sits at your neckline, the sparkle factor is part of what makes fine jewelry so meaningful.
Visiting Our Toronto Showroom
The best way to truly understand the impact of polish and symmetry is to see diamonds side by side in person. At our Toronto showroom, our gemologists are passionate about education - we love showing clients exactly how different grades perform under various lighting conditions, and helping you understand what you're seeing in each stone's certificate.
We work with a carefully curated selection of IGI and GIA-certified lab-grown diamonds, sourced with full transparency and ethical accountability. Our clients consistently tell us that the combination of expert guidance, certified quality, and the remarkable savings of lab-grown diamonds makes the experience unlike any other jewelry shopping they've done.
If you're ready to explore, book a consultation with our team. Whether you're starting from scratch or have a specific vision in mind, we're here to make the process effortless and genuinely enjoyable.
Conclusion
Diamond polish and symmetry are two of the most underappreciated factors in a diamond's overall beauty - and understanding what diamond polish and symmetry mean for lab-grown stones gives you a powerful advantage as a buyer. These grades determine how efficiently a stone handles light, and they're fully documented on every IGI and GIA certificate. With lab-grown diamonds delivering the same optical excellence as mined stones at a fraction of the price, there's no reason to compromise on these quality markers.
At 6ix of Diamonds, we're committed to helping GTA shoppers make brilliant choices - in every sense of the word. Explore our collection, build your own ring, or book a consultation with our team today. Your perfect diamond is waiting.