What is VS1?
The VS part of the clarity grade stands for very slightly included and consists of two subcategories of VS1 and VS2. Diamonds that fall within this broader category of VS have minor inclusions that are difficult to somewhat easy for a trained grader to see when viewed under 10x magnification. VS1 represents the diamonds that have inclusions that are difficult for a trained grader to see. They are definitely quite a bit cleaner in appearance than their VS2 counterparts.
Where does it fall on the clarity scale?
VS is really in the middle of all the clarity categories. There are a total of 10 clarity grades from GIA. VS1 is the 5th and VS2 is the 6th clarity grade. VS1 represents the middle of all clarity grades.
Why is it so important?
Not only does VS represent the middle of all diamond clarity, but it is also regarded as a general threshold for eye-clean stones. This means that for all stones with VS2 or better clarity, the diamond will appear flawless and indistinguishable to the naked eye. While VS2 is generally considered to be the benchmark of eye-clean diamonds. VS1 is the guarantee for an eye-clean and eye-perfect stone.
The Role of Crystals:
One unspoken rule for diamond clarity is the role of crystals. For GIA, a pinpoint and a crystal are really separated by whether the inclusion has a discernable body or essentially a point. So, what does it have to do with our VS1 stones? A crystal in 99% of the cases will demote the clarity of a diamond from a VVS to VS. This means VS1 will include very clean stones that unfortunately have a slightly too large pinpoint to call the stone a VVS2 stone. Keep a special lookout for VS1 with crystal as the first clarity characteristic listed for a great stone.
A picture is worth a thousand bucks
Any diamond that is 1 carat or larger and GIA graded will come with a plot or map for all the internal and external features. But should you rely on the plot alone to decide on purchasing the stone? No. VS1 can vary greatly in their face-up appearance all while still costing you around the same amount of money. Thus it is crucial to see the inclusions in real life and check if they are low relief (jargon meaning if the inclusions stand out little from the background). If it is low relief, you have found a great stone. If it is conspicuous, maybe you could get a better stone for that money.
What to avoid when choosing a VS1 stone?
There are generally two types of inclusions to look out for: Internal inclusions that are less desired and inclusions that can pose a durability issue.
One thing to keep an eye out for is opaque black crystals (also called Piqué). They are often roundish and appear very solid. In VS1 stones, they appear towards the edge of the girdle in very inconspicuous places. If you could avoid them, great!
A common durability concern comes from knots and cavities. Knots are crystals that are exposed on the surface. If you are unlucky, that little crystal might decide to move out. That leaves you with an ugly hole and a lighter stone. Very sad. A cavity is what happens when the knot pops out. It's a hole in the stone that can fill with super hard to clean dirt and oil or even chip/break the stone if hit just right.
Another more elusive issue is inclusions near the cutlet or the bottom tip of the diamond. This occurs if a crystal or any other inclusion is located towards the bottom. The many pavilion facets will reflect the one small inclusion many times all around the stone. Those are the easiest to find in a video.
Now decide on the rest of the 4Cs:
Buying a VS1 is buying assurance - you can be sure that the stone will be eye-clean. Congrats! Go forth and claim your gem!