Clarity:

A diamond is judged by professionals on how ‘clear’ it is, and the stone is then placed into a category.

FL, IF – these ratings flawless or Internally Flawless represents the highest grade in this area. Such stones are extremely rare and hence invariably very expensive.

VVS1, VVS2 – These ratings represent a diamond which is only ‘very very slightly included’. ‘Included’ means, essentially, occluded or cloudy. Inclusions of non-diamond material or structure are responsible for lack of perfect clarity.
Despite the ominous sounding word, these gems are very high quality. The flaws can only barely be seen under 10 x magnifications.

VS1, VS2 – Very Slightly Included ratings represent high quality stones. No flaw is visible to the naked eye.

SI1, SI2 – Slightly Included gems contains flaws that are visible under 10 x magnifications and may just barely be seen by those with very sharp eyes. Beyond having good eyesight, though, one needs to know what to look for. Generally, non-experts won’t notice much of anything.

I1, I2, I3 – These are mediocre quality stones that may still look very nice. But they have visible flaws when one looks closely that will reduce the brilliance of the stone’s appearance.

Color:

Beyond the degree of clarity, diamonds - though usually thought of as clear or ‘white’ - can come in any of hundreds of colors. Fashions change and in one era what might be considered a flaw will be highly valued by the next generation. Color in a diamond is actually created by the impurities that mix with the diamond’s carbon structure.

A 200-carat blue diamond in the Smithsonian (the Hope Diamond), for example, is valued not only for its unusually large size. Its rare and pure color is also a significant factor.

Blue, pink and yellow are among the most common colors found in ring stones.

E diamonds are also considered colorless. Any impurities are in trace amounts detectable only by experts with special tools.

F are also graded colorless, but a slight color may be seen by an expert.

G-H are near colorless. Non-experts can detect some shading if they look closely, but these can still be high quality diamonds.

I-J Near colorless diamonds in which the color is slightly detectable. Still have a very good value.

K-M are stones in which the color is highly noticeable. Observe, though, that these ratings are for diamonds that are ranked according to how little color they have. As a result, many will find a yellow diamond quite beautiful.

What’s important is to have the color be uniform. Most people still consider even a small spot of color to be a flaw. Of course, that too is simply a matter of taste and some future trendsetter may decide such diamonds are worth even more.

Cutting:

One factor that is difficult to rank in terms of price or quality is how the stone is cut. That’s because, to a very large extent, which cut is better is a matter of taste. A Round-cut can be just as beautiful as an Oval; a Square-Cut may be just as lovely as a Princess-cut gem (rectangular). Other common shapes are the Marquise, the Pear, Emerald cut, Trilliant (a wedge shape), Radiant, Cushion and Heart shaped.