Have you ever seen a natural, unpolished diamond? If so, you know that while rough diamonds are beautiful, they look almost like quartz. They certainly do not sparkle and shine like their polished, faceted counterparts.

Polishing does a lot for a diamond, and has a major impact on its value. What happens when a diamond you purchased begins to age? Sometimes, if it gets scuffed up, it can lose its sparkle.

The Risks of Polishing Diamonds

Polishing a diamond properly takes specialized knowledge and equipment. Jewelers use sophisticated computer programs to assess raw diamonds and figure out which cut and shape would suit them best.

The aim is to make the diamond sparkle as beautifully as possible while eating into as little of the material as possible. Every time a diamond is cut, part of its mass is lost. While this should seem obvious, it is easy to forget.

Once a cut is decided on, the jeweler uses a polishing wheel to sand down the diamond’s facets. This process itself utilizes industrial diamonds. The wheel contains a large disc made of stone and covered with diamond dust. Only diamond is hard enough to cut other diamonds.

There are various reasons you might think of re polishing a diamond. Perhaps it has become scuffed or scratched, and there are new imperfections to remove. Or maybe you just are not satisfied with its clarity or sparkle.

Extreme close-up of the surface of a diamond. Re-polishing might remove (some of) the bubbles and inclusions, but it is risky – Image credit to Kurt Bauschardt – CC-BY-SA-2.0

It is risky returning a diamond to the polishing wheel. Each time you cut a diamond, you do risk breaking it or irreparably botching it. There are other risks too, though. It is very easy to overdo it.

A great little anecdote to illustrate this possibility is the famous Koh-i-Noor diamond. The Koh-i-Noor was 186 karats originally, when it was uncut. It was at that time the largest known diamond in the world. It was housed in a Hindu temple, where it served as the eye of a goddess.

It was claimed by the British Empire as part of the spoils of conquest, and presented to Queen Victoria in 1850. The diamond was cut and presented at the Great Exhibition in Hyde Park, London, in 1851. Despite its huge size, it wasn’t considered brilliant enough.

As a result, the stone was cut and re-cut a number of times. Queen Victoria’s consort, Prince Albert, oversaw most of this. He was never satisfied. Over time, he reduced the size of the diamond by 42%, all in an attempt to re-cut and re-polish it to unattainable perfection. Today, the Koh-i-Noor weighs only 105.602 carats.

As you can see, you can lose a lot of material when you try to re-cut and re-polish a diamond! While Prince Albert’s dissatisfaction is understandable on some level, he clearly went overboard with his attempts to improve the appearance of the diamond. So much so that he removed almost half of its weight before he was done—and even then he wasn’t happy with the result.

This is not to say there are not some equally famous success stories out there. Laurence Graff of Graff Diamonds purchased the renowned Wittelsbach diamond in 2008 and took a great risk of re-polishing it. He lost only 4.45 carats (out of 25.52), and managed to bring its clarity from VS2 to Internally Flawless. He managed to achieve a similar success with the famous Graff Pink.

While there probably isn’t so much history at stake with your own diamond, your own gem is still very precious, and the decision to re-polish is one that deserves your careful consideration. If you are mostly happy with the appearance of your diamond, you may want to leave it alone, especially if it is small.

Every time you have your diamond cut and polished, it will lose at least some mass. On the other hand, if you are absolutely certain that the risk is worth it, you may want to go for it. Sometimes the decision to re-polish a diamond can turn an average stone into an extraordinary one.