Clarity is another important concern when choosing a diamond. And it’s important that you know how the rating system works before you buy one. It’s really easy, actually. There are basically just two things you need to know: Diamonds are sorted into two main categories, those with visual inclusions and blemishes, and those that are “eye clean”, meaning that there are no inclusions or blemishes than can be seen with the naked eye. From there the clarity of a diamond is further broken down into subcategories.

Most people make the mistake of thinking that a diamond’s clarity refers to how clear it is, but that’s not the case. Clarity actually refers to the internal and external imperfections of the diamond. The grading system for a stone’s clarity is based on the number and visibility of these imperfections.

The best diamonds, get a grade of FL or IF – Flawless or Internally Flawless – meaning that they are perfect stones, inside and out. A grade of I-1, I-2, or I-3 means that the diamond is imperfect, with a grade of I-3 being the worst.

Then the next category breaks it down even further with grades of VVS! And VVS2, which mean that the diamond is very, very slightly imperfect;, VS1 and VS2, meaning the diamond is very slilghtly imperfect; and SI-1 and SI-2, which meant that the stone is slightly imperfect.

The last C, of course, refers to the color of the stone, with a completely colorless stone being the most perfect. Diamonds are not all truly colorless, but it’s the colorless diamonds, sometimes called white diamonds, which all other shades are judged against.

The Gemological Institute of America (GIA) has devised a set of guidelines to grade diamond color and a lettering system from D to Z was set up to help distinguish the different quality levels, with D being used for only the rarest, most colorless diamonds. These colorless diamonds sometimes contain traces of yellow to a yellowish brown color and shouldn’t be confused with the Fancy, colored diamonds. Those are rated with their own system.
D-E-F
Colorless.
G-H-I-J
Nearly colorless.
K-L-M
Faintly tinted, usually yellow.
N-O-P-Q-R
Lightly tinted, usually yellow. Tint can be seen with the naked eye.
S-T-U-V-W-X-Y-Z
Tinted, usually yellow, may progress to brownish. Tint visible to the naked eye, even when mounted.

While the color of the diamond does affect the quality grade and the price, it shouldn’t be your main concern. If a diamond just has a very slight tint to it, say a bit of yellowish color, if you put it in a setting made of a white metal, like white gold or platinum, it will make the stone appear more clear in color, as opposed to putting it in a yellow setting, like gold, which would make the stone appear more yellow. Again, you want to look at the diamond you thinking of buying in different types of light to see how it reacts under any condition. Look at it in sunlight, fluorescent light and under a jeweler’s black light to see how much it sparkles and shines. And hold it against different colored backgrounds, too, if possible.