Clarity is one of the 4 C’s of a diamond and one that describes and determines the value of the gemstone. By definition, clarity means a gem’s relative freedom from blemishes and inclusions – the higher the clarity grade, the lesser will be the flaws in it.
While inclusions are located inside the gem, blemishes can be found on its surface. However, both clarity characteristics of diamonds can dim its brilliance, no matter how minute they are. In fact, although the minute ones are invisible to the naked eye and only a professional can see them using a scope, they still affect the overall value of the stone.
Both blemishes and birthmarks appear at distinct stages of the formation of a diamond. Birthmarks may be present right from the creation of the gem, whereas its blemishes may happen during cutting, setting, or wearing it. There are many distinct types of birthmarks or inclusions too. Since the gem forms in extreme heat as well as under high pressure, crystals can get trapped within it. This is one common birthmark in a diamond. Many of these diamond crystals can be seen if it is examined at 10x magnification.
In case the gemstone displays an uneven atomic structure, then it can have internal graining also. The clarity characteristic of the gem looks like faint streaks or lines. The gem can have internal breaks also, formed either during its formation or after it. They are the ‘feathers’ of the stone; called that way due to their feathery appearance.
On the other hand, blemishes happen after the formation of the gem, during cutting, mounting, and even after wearing the polished stone. Additional facets, thin ridges and parallel grooves or polish lines, and burns due to heat from the polishing wheel occurred during cutting, are some examples of blemishes occurred during its manufacturing phase. Scratches, abrasions, and chips are some blemishes occurred while handling or mounting the diamond on an engagement or wedding ring. However, chips usually denote deep openings where part of it was broken off, which occur often at its girdle edge.
As said, most of the blemishes and birthmarks are too small to be detected by the naked eye. A trained eye will be required for it and then grade the stone as per its clarity characteristics. In rare cases, a diamond can have an absence of inclusions or blemishes; if so, it gets a Flawless clarity grade. As such diamonds are extremely rare to find, they are the most expensive ones in the industry.