What does polish grade mean for a lab-grown diamond?

Polish is a graded quality attribute describing the condition of a lab-grown diamond's facet surfaces after cutting and finishing. IGI evaluates polish as a distinct criterion, separate from cut and symmetry, on a six-point scale: Ideal, Excellent, Very Good, Good, Fair, and Poor. The grade reflects how cleanly each facet was smoothed during cutting, with common characteristics including faint wheel marks or minor surface nicks too small to affect the clarity grade. A grade of Good or higher means no polish defects are detectable without magnification, so facets reflect light cleanly across the stone's surface. Grades below Good, particularly Fair or Poor, introduce surface haze that interrupts how light enters and exits the stone, reducing brightness in ways visible under magnification and sometimes to the naked eye. Polish matters most in high-facet cuts such as rounds and ovals, where surface irregularities more readily disrupt light return. For buyers working within a budget, choosing Very Good over Excellent is a practical trade-off: the visual difference is negligible to the naked eye, and the saving can be redirected toward carat weight or colour. For everyday jewellery, Very Good or higher is the threshold where polish stops being a meaningful concern. When comparing lab-grown diamonds at similar carat weights, checking the polish grade on the IGI certificate before focusing on price differences is a straightforward way to protect optical performance.