Virtually all natural diamonds contain identifying characteristics, yet many are invisible to the naked eye. Under the scrutiny of a jeweler's 10x-magnifying loupe or microscope, natural phenomena -- called inclusions -- may be seen. These are nature's birthmarks, and they may look like tiny crystals, clouds, or feathers.
Diamonds categorized as internally flawless reveal no such inclusions. Flawless stones are at the top of the diamond quality scale and are treasured for their rarity and beauty. Diamonds with very, very small inclusions are graded as V V S 1 or V V S 2. This quality level would contain inclusions very difficult for a trained eye to find under magnification. Diamonds with very small inclusions are graded as V S 1 or V S 2. This quality level would contain inclusions difficult for a trained eye to find under magnification. Diamonds with small inclusions are graded as S I 1, S I 2 or S I 3. This quality level would contain inclusions somewhat easy to for a trained eye to find under magnification. The S I 2 and S I 3 levels might contain inclusions visible from the underside of the diamond, but not in the face up position. Diamonds with inclusions very easy to see under magnification are grades as I 1, I 2 or I 3. This quality level may also contain inclusions visible to the trained eye in the face up position.
The number, color, type, size and position of surface and internal birthmarks affect a diamond's value. Major inclusions can interfere with the path of light that travels through a diamond, diminishing its brilliance and sparkle and therefore its value.