Most Diamonds contain inclusions. Sometimes they are incorrectly referred to as “carbon spot”. In reality they can be a myriad of things from other minerals such as carbon or even a garnet. There can also be minute fractures within the stone. What ever they are, they are the internal characteristics of the stone. It is what makes each diamond unique. You should learn to recognize the “birthmarks” in your stone as they are an easy means of identification.
The Clarity Grades as defined by the Gemological Institute of America are generally accepted throughout the world. Each has a very specific meaning. The grading takes place using 10x magnification using either a loupe or a gem microscope. As can be expected, the fewer inclusions, the rarer, thus the more valuable the stone.