Diamond clarity is one of the four quality factors (the 4Cs) that describe and determine the value of a diamond. By definition, clarity means “a gemstone’s relative freedom from inclusions and blemishes.” These two terms are locational- blemishes are found on the outside of the gem and inclusions are located on the inside. Both of these clarity characteristics can dim the brilliance of a diamond, though some are so minute that they are invisible to the naked eye.

Both inclusions and blemishes appear in a diamond at different stages of a diamond’s formation. Inclusions may be present from a diamond’s creation, whereas blemishes may appear during cutting, setting, or even the wearing of a diamond.

There are many different types of inclusions, also known as internal clarity characteristics. As diamonds form in extreme heat and under great pressure, small crystals can become trapped inside. This is a common inclusion. Many of these crystals can only be seen if the diamond is studied at 10x magnification. If the diamond has an irregular atomic structure, it can also have a clarity characteristic called graining. Graining looks like faint lines or streaks. Diamonds can also have internal breaks, formed during or after formation. These breaks are called ‘feathers,’ because of their feathery appearance.

Blemishes occur after a diamond’s formation, during the cutting, mounting, and wearing of a polished diamond. Extra facets, polish lines (thin parallel grooves and ridges) or burns (from excessive heat on the polishing wheel during cutting) are examples of blemishes introduced during the manufacturing process. Nicks, scratches, chips and abrasions are examples of blemishes introduced during the handling, mounting or wearing of a diamond. Chips are shallow openings where part of the diamond was broken off, most often at the girdle edge.

Many inclusions and blemishes are too tiny to be seen by anyone other than a trained diamond grader. In some cases, a diamond can have a flawless clarity, or a total absence of any blemish or inclusion. Since rarity and value are related, a diamonds with a flawless clarity are incredibly rare and thus, the most valuable of all diamonds.

Learn more about diamond clarity with Diamond Clarity: Understanding Diamond Clarity Grades.