Diamond quality is rated using 4Cs: Cut, Clarity, Colour and Carat (weight). The scale was devised by the Gemological Institute of America (GIA) in 1953. The 4Cs are now used almost universally to grade diamonds.

VS1 refers to the clarity of diamonds. Clarity might be confusing because it is actually a measure of the flaws in a diamond, both internally and on the surface. Internal flaws are called inclusions, and surface flaws are blemishes.

The scale runs from Flawless (FL) to Included (I). VS1 means that a diamond has very slight inclusions that will be visible under 10x magnification, using a jeweller’s loupe, but are rarely visible to the naked eye.

The GIA grades for diamond clarity

• FL–Flawless
• IF – Internally Flawless
• VVS1 – Very Very Small Inclusions 1
• VVS2 – Very Very Small Inclusions 2
• VS1 – Very Small Inclusions 1
• VS2 – Very Small Inclusions 2
• SI1 – Small Inclusions 1
• SI2 – Small Inclusions 2
• I1 – Inclusions 1
• I2 – Inclusions 2

Inclusions in diamonds are a normal part of the process of their creation; only about 1% of diamonds are graded as flawless (FL).

Is A VS1 Diamond A Good Choice?

For most buyers, an eye-clean diamond will be a great choice. Eye-clean means that to a person of healthy eyesight, there will be no visible flaws in the diamond, even if there are inclusions under magnification. In practical terms and to anyone who is not a jeweller, there is no difference between an eye-clean VS1 diamond and an FL, flawless diamond, except the price! There’s just no need to pay more than the cost of a VS1 diamond. Save the money or use the savings to pay for a larger or better cut gem. Incidentally, diamond cut quality is worth paying for. It is the quality of the cutting that brings out the brilliance and sparkle of a diamond. The only possible exception is with very low-grade I1 or I2 diamonds where the inclusions reduce the amount of light available for reflection and making sparkle. Most jewellers do not even sell I1 and I2 diamonds.

Exceptions To The VS1 Rule

In general, a VS1 diamond will give you the clarity you need with no need to pay for a higher grade, there are a couple of exceptions where spending more might be worthwhile.

Diamonds Above 2 Carats

The advice to buy a VS1 diamond applies to most diamonds sold, which are less than 2 carats. Diamonds above 2 carats in weight will, because of their size have larger facets than a smaller gem. These larger facets act as windows into the diamond and can reveal inclusions that would not be seen in a smaller diamond. The larger surfaces of the diamond are more likely to have surface blemishes than a smaller gem.

Of course, very often you will still be okay with a VS1 grade, but you will need to check it more carefully and certainly not buy it sight unseen.

Step Cuts And Large Tables

By far the most popular diamond shape is the round brilliant. This diamond shape has 58 facets, each catching and reflecting light to create the characteristic sparkle. The reflections make it hard to detect inclusions within the diamond. Diamonds with fewer facets or with facets cut into stepssuch as emerald or asscher cut are much less effective at concealing flaws. To a lesser degree, other diamond shapes with a large table (the flat top facet) such as baguettes share the same issue.

With these diamonds, you need to check each diamond very carefully. As with large diamonds you may be able to get away with a VS1. It might be necessary to jump a grade to VVS2 with the attendant jump in price to be sure of getting the quality you want.

Why Buy A VS1 Rather Than A VS2?

For diamonds of less than 2 carats, it can be hard to tell the difference between a VS1 and VS2 diamond. A good VS2 diamond can offer great value to the lucky buyer. A VS2 can be eye-clean or have its inclusions in areas that are not easily seen or even hidden by the metal of the setting. A VS1 diamond removes the element of luck! In a VS2 diamond, one can hope for no visible inclusions; in a VS1 diamond, you can expect not to see any visible inclusions.

As diamond grades are a range from best to worst, a lousy VS2 might not be much better than a good I1. Such a diamond would probably not be a good choice, and a VS1 would undoubtedly be a much better gem.

With a VS1 diamond, it might need an expert to pick out inclusions under 10x magnification, with a VS2 the inclusions will probably be evident under magnification.

So, even an eye-clear VS2 diamond will be worse than a VS1 diamond. The choice is yours when you buy, but the choice is a question of the standards you set.

Some Buying Ideas

When you buy a diamond, look out for the certification. Not all diamonds carry an independent certificate, some tiny stones are not economical to grade, but larger ones should be. The certification should come from the GIA or AGL, these are the two highest reputed grading labs and their reports can be counted upon to be accurate. GIA and AGL reports are trusted across the industry and will be accepted by insurers and jewellers if you come to sell the stone.

Always check your diamonds before purchase. If you buy online, then use high-quality images or video to make your choice. Avoid low-resolution, poor-quality photos. If you purchase from a brick and mortar store,then check out the diamond in-person and ask to use a jeweller’s loupe to see the diamond under magnification.When you choose a diamond, whether it is a VS1, VS2, or better, trust your own judgment and your eyes. A diamond is a lifetime purchase - you want to get it right. If you are unsure about what you are seeing, ask for another diamond to make a comparison. Don't be afraid to choose a different stone of higher or lower clarity.