Diamond polish refers to the degree of smoothness of each facet of a diamond. Polish features include: burn, abrasion, pit, lines & more. Find out how a diamond's polish can impact its appearance and more with our diamond polish guide, straight from Queensmith's experts.
What is diamond polish?
Diamond polish is the surface smoothness of each diamond facet. Diamond polish is assessed and recorded by diamond graders, and contributes to the overall cut characteristics of the diamond. During polish grading, any defects or imperfections in the polish are noted. The smoother each facet, the better the polish grade, and the better the diamond’s dispersion of light. Put simply, a high diamond polish grade results in better sparkle.
Diamond Polish Grading Scale
The GIA determines diamond polish grade under 10x magnification. Once all surface defects and characteristics are recorded, the diamond will be awarded a polish grade. The fewer and less severe the polish defects, the better the diamond polish grade. Queensmith recommends you consider diamonds with Excellent to Very Good polish grades, for diamonds with the best sparkle.
Excellent - The diamond shows no polish defects, or incredibly minute features are visible only under magnification and with difficulty.
Very Good - The diamond shows extremely minor polish defects, e.g. transparent polish lines or faint scratches, visible only under magnification.
Good - The diamond shows minor polish defects, e.g. moderate to heavy polish lines or heavy scratches. The lustre of the diamond may be slightly impacted by the polish defects.
Fair - The diamond shows polish defects that may be visible without magnification, e.g. heavy polish lines or burned facets. The lustre of the diamond is noticeably impacted by the polish defects.
Poor - The diamond shows major polish defects that are visible without magnification, e.g. dark and deep polish lines, burned facets over the crown and pavilion. The diamond has very little lustre due to the polish defects.
Images via gia.edu
How does diamond polish affect the cut grade?
Along with diamond symmetry, diamond polish characteristics contribute to the overall cut grade. Symmetry and polish indicate the quality of a diamond’s finish. For an overall Excellent cut grade, the diamond polish and symmetry must be graded Very Good or Excellent. Likewise, an overall Very Good cut grade will have Good or Very Good symmetry and polish grades, and so on.
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A diamond's polish grade contributes to its overall cut grade. You don't need to get too into the polish grades - instead, opt for an Excellent or at least Very Good cut grade, and the polish grade will be more than adequate.
Diamond polish features and characteristics
The majority of diamonds feature some kind of polish irregularity, albeit invisible to the naked eye in the case of Excellent and Very Good polish grades. Here are the 10 polish features diamonds can feature.
Abrasion - Tiny scratches on the edge of a facet. The minuscule marks of the abrasion appear along the line of the facet edge, creating a fuzzy white line where an otherwise crisp facet edge would be.
Burn - Excessive heat during the polishing process causes a translucent white haze. A diamond burn can look cloudy.
Laser Manufacturing Remnant - A tiny white groove on the surface of the diamond that was created during cutting. Diamond cutters use lasers to map where to cut and which parts of the rough diamond to remove.
Lizard Skin - A rough looking, uneven texture, typically confined to one facet, where the diamond was polished off-grain. The look is comparable to reptile skin, although minute.
Nick - A small chip, or notch, where two facets meet. This is typically along the girdle.
Pit - A minute ‘hole’ or cavity. This will appear as a small white dot on the diamond’s surface.
Rough Girdle - An unpolished girdle, or a girdle that appears rough due to irregularities like pits and nicks. Most diamonds in circulation have polished girdles.
Scratch - A line-like blemish, typically ultra thin and not particularly long. A scratch will appear like a faint white line.
Polish Lines- Multiple lines, running parallel to each other. These are typically faint white or transparent unless referred to as Drag Lines, which are more apparent to the naked eye than typical polish lines.
Images via gia.edu