Understanding the clarity of a diamond

If you’re thinking about buying a diamond, you may well have heard people talking about a diamond’s ‘clarity’. Diamond clarity is a concept that is often misunderstood, and since it has a major impact on a diamond’s value and therefore price, it’s worth taking a moment to get to grips with it.

The value and therefore price of diamonds is largely determined by the ‘4 Cs’: carat weight (i.e. size), and three measures of quality: colour, clarity, cut. Of these, clarity refers to how ‘clean’ the crystal is.

A diamond that you look at today will have started life millions of years ago, as liquid carbon trapped under huge pressure and at incredible temperatures far below the surface of the earth. It gradually rose to the surface, and as the temperature and pressure decreased it hardened into the crystalline structure we call rough (or unpolished) diamond. During this process, tiny imperfections would have developed within the crystal structure, which we call inclusions.

Inclusions can take many forms. Perhaps a specks of other material got trapped within the crystal. Or the stone could include small bubbles, or feathers (tiny cracks). Not every ‘inclusion’ is equally problematic. The more of them there are, the bigger and more central they are, the more visible they are, and the lower the stone’s ‘clarity’ is said to be.

There is no formula to determine the clarity of a specific diamond. It isn’t possible to simply count the inclusions and map them on the stone to calculate a universally-accepted clarity grade. Instead, it’s the job of an expert gemologist to make a subjective assessment based on years of experience.


Diamond clarity is assessed at 10x magnification, and a diamond with no imperfections visible at this magnification is graded as ‘internally flawless’ (IF) or ‘loupe clean’ (LC – a loupe being the name of the magnifying glass that jewellers use to view diamonds). In reality, even an internally flawless diamond will have some imperfections in the crystal structure if viewed at a high enough level of magnification.

Below IF, the other clarity grades are very very slightly included (VVS1 and VVS2), very slightly included (VS1 and VS2), slightly included (SI1 and SI2), and included (I1, 12 and I3).

Overspending on clarity is a common mistake, with many clients assuming that an internally flawless, VVS1 or VVS2 diamond will look better to the naked eye than a VS1. If a diamond has been properly graded this won’t be the case, but by choosing to go with a higher clarity than necessary, a fixed budget will mean having to compromise more than necessary on the size, colour or cut of their diamond.

As a rule of thumb, if a brilliant cut diamond has been assessed as VS2 clarity by a reputable authority it ought to be flawless to the naked eye. But you do need to be careful as not all diamonds are graded to the same strict standards, and a less reputable authority might grade a brilliant cut diamond as being VS2 (or higher) even when there are inclusions visible to the naked eye. It is easier to spot inclusions in diamonds without brilliant faceting (such as the emerald cut), and so if you want one of these to be ‘eye clean’, you need to be looking at VS1 or higher.

One common misconception about clarity is that it has a major impact on how a diamond sparkles. In reality, only in diamonds with very poor clarity are the inclusions big enough to have a discernible impact on how light passes through the crystal, and hence the sparkle. For the majority of diamonds, the cut, polish, and symmetry of the stone are the key factors that determine how much a diamond sparkles. So, if a diamond has even reasonable clarity (small inclusions visible to the naked eye), then going further up the clarity scale won’t bring an improvement in sparkle.

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