Introduction
Diamond polishing is the quality and condition of the facet surfaces. If the facets—which act like tiny mirrors—are clear and smooth, they reflect light well. If a diamond’s facets aren’t smooth, they can inhibit or alter light reflection (making the diamond appear dull).
A rough diamond often has miniscule crystal bumps present on the facets. When a diamond is polished, those bumps are removed. By using a fine grain diamond dust on a polishing wheel and polishing for a long time, a gemologist achieves higher polishing grades.
After a diamond is cut, the cutter will finish the stone to achieve a smooth, glass-like surface. The quality of this work is known as diamond polishing. Gemologists, once again, examine the stone under 10x magnification in order to rank a diamond’s polishing, looking for remnants of imperfections the cutter may have left behind.
While inclusions occur naturally as the diamond forms, polishing marks are the result of human error. Nearly every diamond has some sort of flaw due to polishing. But unlike symmetry, many of these flaws are so minute that they cannot be seen with the naked eye.
Diamond Polishing Grade: Which grade should you choose?
Diamond polishing grades are given based on the smoothness of each facet. A gemologist reviews the diamond under magnification to determine the polishing grade. We recommend diamonds that have Excellent, Very Good or Good polishing grades. Diamonds with a lower polishing grade (Fair and Poor) won’t reflect light as well and may appear dull.
Here are the GIA polishing grades:
Excellent: No polishing flaws are visible under 10x magnification (standard jeweler’s loupe).
Very Good: Polishing flaws are very difficult to spot under 10x magnification.
Good: Polishing flaws are somewhat difficult to find with 10x magnification.
Fair: Some polishing flaws are seen under 10x magnification and may also be visible to the naked eye. These diamonds are not recommended.
Poor: Flaws are visible under magnification and to the naked eye. These diamonds are not recommended.
Diamond Polishing Marks
Some polishing marks are so faint that gemologists can only find them under high magnification and at a certain angle. The most common polishing marks are:
Scratch: A transparent-looking white line on the diamond’s surface.
Nick: A small notch on a facet or girdle junction.
Abrasion: A collection of nicks at facet junctions.
Pit: A small opening in the surface, usually due to inclusions falling out during polishing.
Lizard skin: A bumpy looking texture.
Rough girdle: A girdle that has been left unpolished.
Burn marks: A whitish haze on a diamond’s surface, caused by high temperatures from a polishing wheel.
Does Diamond Polishing matter?
Diamond polishing does impact a diamond’s beauty and brilliance, but not as much as you might think.With over six years of experience in the diamond industry and working for one of the largest and most well-respected firms in the world, I cannot distinguish between an “Excellent” Polishing diamond, a “Very Good” Polishing diamond or even a “Good” Polishing diamond.Technically speaking, “Excellent” Polishing diamonds have been polished longer on the polishing wheel with a finer grain of diamond dust. But the simple fact is, if I can’t tell the difference with a 10x loupe, there’s no way I’ll be able to perceive a difference without magnification. So there’s no reason to pay for it.
While it might look nice on a piece of paper to have a pretty word like “Excellent” written under Polishing, it’s certainly not worth paying extra for. It’d be like a car salesman convincing you to purchase a $5000 upgrade package for a “friendlier cabin aura.”Instead of searching for an “Excellent” diamond polishing grade, it’s more important to look for a well cut diamond with plenty of brilliance. Besides looking at the Cut grade, review the diamond up-close to see how brilliant it is. For example, this stunning 0.8 Carat True Hearts diamond from James Allen offers an incredible amount of brilliance. The light reflects well off of the diamond’s table and facets. A diamond like this makes for a truly stunning engagement ring.
Look at this comparison of two diamonds from Blue Nile, a 1.21ct H/VS2 Round diamond with Excellent polishing (left) and a 1.21ct H/VS1 Round diamond with Very Good polishing (right). Inclusions aside, they look virtually identical. diamond polishing very good excellent
Impact of Diamond Polishing on Price
A diamond’s polishing grade can impact the price, but not as significantly as other qualities. Most Excellent cut diamonds also have “Excellent” polishing, though some of these diamonds may have a “Very Good” or “Good” polishing grade. A lower Polishing graded diamond might be priced slightly less, saving you a few dollars, depending on the other qualities of the diamond.Most GIA graded diamonds have an Excellent polishing, though. In fact, there are so few GIA Very Good polishing diamonds, that they’re usually more expensive than Excellent polishing diamonds. Because Excellent polishing grade diamonds are so common, a lot of sellers have diamonds certified by not-so-strict labs. They go with a more lenient lab because they don’t want to carry Very Good polishing graded diamonds.
When you shop for diamonds, it’s most important to be on the lookout for a beautifully cut diamond with plenty of brilliance (rather than a certain Polishing grade). As long as the Polishing grade is Good or better, the diamond’s beauty won’t be impacted by polishing flaws since they won’t be visible to the naked eye. If you can save some money going for a slightly lower Polishing grade, it’s fine to do so.
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