Naturally-occurring features called inclusions provide a special fingerprint within the stone. Inclusions are natural identifying characteristics such as minerals or fractures, occurring while the diamond was being formed in the Earth.The majority of these natural birthmarks are invisible to the naked eye, yet they affect the way light is reflected and refracted within the stone. Inclusions appear as different shapes, such as crystals, clouds or feathers. These idiosyncrasies often add to the overall character of the diamond. Containing several birthmarks or inclusions, the Excelsior is considered one on the world's most beautiful diamonds.Most inclusions are not visible to the naked eye unless magnified.To view inclusions, gemologists need to use a magnifying loupe that allows them to see a diamond at 10x its actual size.Inclusions are ranked on a scale of perfection, known as clarity. The clarity scale, ranging from F (Flawless) to Included (I), is based on the visibility of inclusions at a magnification of 10x. Even with a loupe, the birthmarks in the VVS (Very, Very Slightly Included) to VS (Very Slightly Included) range can be very difficult to find. It is only when a diamond is graded 'I' that it is possible to see the birthmarks with the naked eye. The position of inclusions can affect the value of a diamond and you should consider the number, size, brightness, nature and position of inclusions. Some inclusions can be hidden by a mounting, and have little effect on the beauty or brilliance of a stone. An inclusion in the middle or top of a diamond could impact the dispersion of light, sometimes making the diamond less brilliant.There are very few flawless diamonds found in nature, making these diamonds much more valuable.