Virtually all natural diamonds contain identifying characteristics, many of which are invisible to the naked eye. Clarity is the degree to which a stone is free form marks called blemishes and internal features called inclusions. Inclusions normally have a greater impact on grade, value, beauty and durability than do blemishes.

Irregularities in the atomic arrangement of a growing diamond crystal can cause what is known as graining. Graining may look like faint lines in the stone. Many diamonds contain crystals of other minerals. Tiny ones are called pinpoints. Groups of very tiny ones – too small to be seen individually – are called clouds. Included diamond crystals that reach the surface are called knots. Most diamond professionals use the term feather for any fracture in a diamond. Leaving part of the crystal’s original surface on the cut stone produces a natural. If a natural is confined to the girdle, it is considered a hallmark of good cutting proving the cutter removed only as much rough as necessary.

When shopping for a diamond, the goal is to decide what level of these “flaws” is appropriate for this particular purchase. A certain level of flaws can be to your advantage since they act as a fingerprint. These flaws can lower the price of the diamond to make it affordable without affecting its beauty to your eye.
The position of an inclusion affects how readily it can be seen. Cutters call the area seen through the table the heart of the stone and make every effort to cut a stone so that inclusions are not visible through the table of the finished stone. The preferred position for inclusions is under the bezel facets or near the girdle because they are less noticeable there.
Sometimes inclusions are located where they cause multiple reflections in the pavilion facets when you look at the stone from the top. Such reflectors lower the clarity grade more than similar non-reflection inclusions. An untrained person will have a very difficult time trying to find inclusions or blemishes in FI, IF, VVS1, or VVS2 grades even with a microscope.
VS1 and VS2 graded stones have very small inclusions that are difficult to find even when viewed under 10X magnification. To the novice, you still may need proof to find the flaws. These are very high quality diamonds.
SI1 and SI2 are the two most common grades for the typical buyer. These grades have inclusions or blemishes when viewed under 10X magnification. Most SI1 clarity diamonds should be “eye clean,” which means the flaws can’t be seen with the naked eye when viewed from the top. These are good quality diamonds and provide great beauty at a very reasonable price. Most SI2 clarity diamonds will have inclusions visible to the naked eye from the back of the stone. Caution! There are some SI2 clarity diamonds that have inclusions easily visible to the naked eye and should only be used for earrings or pendants, not for engagement rings.
I1, I2 and I3 are commercial grade diamonds and should be avoided except perhaps for I1 in earrings. Many people unwittingly buy I1 and I2 stones in uncertified stones, but if you shop carefully you can buy an eye-clean SI1 stone for a great price and not worry about the clarity.
Advice: For diamonds with many facets (i.e., brilliant round), it is extremely difficult to see the difference between SI1 and higher grades even with a loupe or microscope. Therefore, target SI1 or VS2 as the best clarity values with outstanding beauty.

A diamond is the hardest thing in the world, but not the toughest. Diamonds can get abrasions or even chip through normal wear and tear. When diamonds rub together while being stored, they may get scratched or abraded (minute scratches and pits along facet edges). Be careful that diamonds do not come in contact with another diamond. Diamonds are valuable objects and should not be abused.