If you’ve ever browsed diamond certifications, you’ve probably seen something called a “polish grade.” It sounds fancy—like a final buff or some extra sparkle. And when you see “Excellent” polish on a report, you might assume the diamond is flawless in every way. But here’s the thing: polish is one of the most misunderstood (and sometimes misleading) elements on a grading report. Let’s talk about what polish really means—and what most people aren’t telling you.
So… what is polish, exactly?
Polish refers to the surface finish of a diamond—how smooth the facets are after the cutting process. It doesn’t affect the shape or the angles of the cut, but it can influence how cleanly light reflects off the surface. In theory, better polish means better light performance and less surface haze.
Diamonds are graded for polish on a scale: Excellent, Very Good, Good, Fair, and Poor. Most diamonds on the market today are excellent or very good. Anything below that rarely shows up in quality collections because the difference is visible even to the untrained eye.
But here’s the dirty part
The polish grade doesn’t always reflect what you see—it reflects what a grader sees under 10x magnification. That means your diamond could have a microscopic polishing line or a faint surface grain that has zero impact on how it looks to the naked eye… and it could drop the polish grade because of that.
On the flip side, there are “excellent” polish diamonds out there that don’t sparkle as much as you’d expect. Why? Because polish is surface-level—it has nothing to do with proportions, symmetry, or how well the stone was actually cut. And cut is what really drives light performance.
It’s also kind of… automated now
Here’s something most consumers don’t know: polish grading, especially in mass-market lab environments, is often fast-tracked. It’s assessed quickly, sometimes even by machine in large volume grading operations. It’s not the artisanal hand-loupe inspection you might imagine. And in some cases, labs tend to overgrade polish because it’s the least critical “C” when push comes to shove.
So why do sellers hype it?
Because it’s an easy value-booster. A diamond with “Triple Excellent”—cut, symmetry, and polish—all graded Excellent, sounds premium. And in many cases, it is. But polish is the least important of the three. It’s also the easiest one to improve. If a diamond has perfect polish but mediocre cut proportions, it might look good on paper but fall flat in real life. And yet it sells because of that “Triple Ex” tag.
Should you avoid lower Polish grades?
Not necessarily. A diamond with Very Good polish can look identical to one with Excellent polish in real life. Unless you’re looking through a jeweler’s loupe under just the right lighting, you’re not going to notice microscopic grain lines or faint abrasions. What you will notice is brilliance, fire, and overall life—and those are driven by cut, not polish.
That said, you probably want to avoid anything below “Good” polish, especially for center stones. Below that, surface defects can become visible, and they can dull the sparkle or make the stone look hazy. But between excellent and very good? Go with what looks better, not just what’s written on paper.
Look at the diamond, not the report
This sounds obvious, but it’s worth repeating: a grading report is a guide—not gospel. Don’t chase an “excellent” polish grade just because you think it means better sparkle. Look at the diamond in person (or through video, if buying online). Rotate it. See how it performs in real light. A well-cut diamond with very good polish will always beat a poorly cut diamond with top-tier polish.
One last thing: don’t overpay for polish
Some retailers use polish grades as a pricing lever, charging more for “Triple Excellent” diamonds even when the difference is negligible. Unless you’re buying an investment-grade diamond or something massive, there’s usually no need to stretch your budget just for an excellent polish grade.
Final word
Polish is part of the story—but not the whole book. It’s one of those diamond details that gets hyped up but doesn’t always deliver what people assume. As long as the stone is clean, sparkling, and well-cut, your eye won’t notice if it’s Excellent or Very Good. And that’s the truth most people won’t tell you.